Thermosets and Composites: Technical Information for Plastics Users

Thermosets and Composites Technical Information for Plastics Users, by M. Biron ISBN: 1856174115 Publisher: Elsevier Sc...

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Thermosets and Composites Technical Information for Plastics Users, by M. Biron

ISBN: 1856174115 Publisher: Elsevier Science & Technology Books Pub. Date: December 2003

List of Tables and Figures Tables Chapter 1 Table Table Table Table Table Table Table Table Table Table Table Table Table Table

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14

World consumption or production by weight (million tonnes) 2 World consumption or production in terms of volume (million m3) 3 World consumption at equal tensile stress (million m3 *Young's modulus) 3 Growth in world consumption- normalized on 100 for reference year 1985 4 4 Examples of material hardnesses 5 Tensile properties of various materials 7 Specific tensile properties of various materials 9 Physical and electrical properties of various materials 10 Thermal properties of various materials 12 Order of magnitude of some material costs (s 13 Order of magnitude of some material costs (s 15 [Tensile properties/cost per litre] ratios of various materials 26 Examples of the process choice versus the part characteristics 27 Examples of economic characteristics of some processes

Chapter 2 Table Table Table Table Table Table Table Table Table Table Table

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11

Table 2.12 Table 2.13 Table 2.14 Table 2.15 Table 2.16

Global plastic consumption 32 Market share for the major plastics 33 Market share for some engineering and speciality plastics 33 Annual consumption of major thermosets (1000 tonnes and %) 35 Composite consumption in North America, Europe and Asia 36 Market shares for the main matrices used for composites 37 Market shares for the seven main plastic application sectors 38 Market shares for the eight main thermoset application sectors 39 Market shares for the nine main composite application sectors 41 Market shares (%) for the main European countries 44 Europe: market shares (% by weight) for the nine main composite application sectors 45 Europe: market shares (% value) for the nine main composite application sectors 46 North America: market shares (%) for the nine main composite application sectors 47 Global consumption of major thermosets 1990-2005 (1000 tonnes and %) 48 Market shares and predicted growth for the nine main composite application sectors in the USA 49 Processing turnover statistics 50

Thermosets and Composites

Table Table Table Table

2.17 2.18 2.19 2.20

Table Table Table Table Table

2.21 2.22 2.23 2.24 2.25

Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table

2.26 2.27 2.28 2.29 2.30 2.31 2.32 2.33 2.34 2.35 2.36 2.37 2.38 2.39 2.40

Processing company and employment statistics 50 Comparative prices of resins and additives 52 Average selling prices of composites for different markets 54 Examples of mould prices (s and part costs expresse as the ratio [part price]/[raw composite price] 55 Automotive hood: unit cost (g) for prototypes and small outputs 55 Automotive hood: unit cost (g) for small and medium outputs 55 Automotive hood: unit cost (s for mass production 56 Processing methods for prototypes (relative cost per unit) 56 Processing methods for small and medium annual production (relative cost per unit) 56 Processing methods for high annual production (relative cost per unit) 56 Racing canoes: glass and aramid fibre comparison 57 Examples of prices for parts sold on catalogue 58 Examples of parts manufactured to order in small quantities: Unit costs 61 Weight reduction by composites 62 Automotive & transportation: Consumption of thermosets and composites 63 Furniture and bedding: polyurethane consumption in the USA 74 Polyurethane: US consumption in 2000 91 Unsaturated polyesters: shares in % per process (estimations) 95 Unsaturated polyester composites: shares in % per market (estimations) 96 Phenolic resins: shares in % per market (estimations) 104 Amino resin moulded parts: shares in % per market (estimations) 106 Epoxide resins: shares in % per market (estimations) 108 Silicones: shares in % per end use (estimations) 116 Silicones: shares in % per market (estimations) 116

Chapter 3 Table Table Table Table

3.1 3.2 3.3 3.4

Examples of UL temperature indices Examples of part tolerances for normal and precision classes Mechanical property examples for different glass reinforcements Some examples of Poisson's ratio

147 165 167 167

Chapter 4 Table 4.1 Table Table Table Table Table Table Table Table Table Table Table

XVIII

4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12

Polyurethanes: examples of property variations after immersion in ASTM C fuel for 72 h at 50~ Polyurethanes: chemical behaviour Characteristic examples of structural foams and dense polyurethanes Characteristic comparison of various polyurethane foams Castable polyurethanes: property examples RIM elastomer polyurethanes: examples of properties RIM structural foam polyurethanes: examples of properties Rigid polyurethane foams: examples of properties Semi-rigid polyurethane foams: examples of properties Flexible polyurethane foams: examples of properties Polyurea properties: examples Unsaturated polyester: performance retention after immersion in hot water

190 191 195 195 197 199 200 201 201 202 203 214

Contents

Table 4.13 Table 4.14 Table 4.15 Table Table Table Table

4.16 4.17 4.18 4.19

Table 4.20 Table 4.21 Table 4.22 Table 4.23 Table 4.24 Table 4.25 Table 4.26 Table 4.27 Table 4.28 Table 4.29 Table 4.30 Table 4.31 Table 4.32 Table 4.33 Table 4.34 Table 4.35 Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table

4.36 4.37 4.38 4.39 4.40 4.41 4.42 4.43 4.44 4.45 4.46 4.47 4.48 4.49 4.50 4.51 4.52 4.53

Unsaturated polyester unreinforced resins for casting and moulding, matrices for composites: examples of resin properties 217 Vinylester neat resins for casting and moulding, matrices for composites: examples of resin properties 218 Filled or short fibre reinforced unsaturated polyesters (UP): examples of resin properties 219 Fire retardant vinylester resins: examples of resin properties 219 Unsaturated polyester BMC: examples of composite properties 220 Unsaturated polyester SMC: examples of composite properties 220 Other glass fibre reinforced unsaturated polyesters: examples of composite properties 222 Aramid and carbon fibre reinforced acrylate urethane: examples of composite properties 223 Examples of characteristics of certain phenolic moulding powders after ISO 800 224 Designation examples of some phenolic moulding powders after ISO 800 224 Examples of phenolic resin chemical behaviour at room temperature 231 Examples of glass fibre reinforced phenolic moulding powders 235 Examples of mineral filled phenolic moulding powders 237 Examples of organic filled phenolic moulding powders 237 Examples of tribological phenolic moulding powders (after Vynco) 238 Glass fibre reinforced phenolic SMC and BMC: examples of properties 239 Phenolic foam: examples of properties 239 Melamines: chemical behaviour examples 244 Melamine foams: characteristic examples 246 Melamines: characteristic examples 247 Phenolic modified melamines: Characteristic examples 249 Filled unsaturated polyester modified melamines: characteristic examples 250 V0 cellulose filled urea-formaldehyde moulding powder: characteristic examples 250 Epoxies: examples of chemical behaviour at room temperature 261 Examples of moulding and cast epoxides: general properties 268 Examples of epoxide matrices for composites: general properties 269 Examples of filled and reinforced moulding epoxides: general properties 270 Examples of unidirectional epoxide composites: general properties 272 Examples of epoxide composites: general properties 273 Examples of foamed epoxides: general properties 274 Examples of epoxide syntactic foams: general properties 275 Polyimides: examples of tribological properties 281 Polyimides: examples of chemical behaviour at room temperature 285 Thermoset polyimides for moulding: property examples 291 Condensation polyimides for moulding: property examples 293 Undefined polyimides for moulding: property examples 295 Polyimides for laminates: property examples 296 Polyimide foams: property examples 297 Polyimide films: property examples 297 Silicones and fluorosilicones: examples of chemical behaviour 306 Silicone foam: property examples 310 XIX

Thermosets and Composites

Table Table Table Table Table Table Table Table Table Table Table Table Table

4.54 4.55 4.56 4.57 4.58 4.59 4.60 4.61 4.62 4.63 4.64 4.65 4.66

Silicone resins for electronics and optics: property examples Glass fibre reinforced silicone resin laminates: property examples HVR silicones: Property examples LSR silicones: property examples RTV silicones: property examples Silicone elastomers for electronics Silicone foams: property examples Fluorosilicone resins for optics: property examples Fluorosilicone elastomers: property examples Polycyanate syntactic foams: property examples Polycyanate composites: property examples Neat polycyanates: property examples Dicyclopentadiene: property examples

311 312 312 313 314 315 315 315 316 321 321 322 325

Chapter 6 Table 6.1 Table 6.2 Table 6.3 Table 6.4 Table 6.5 Table 6.6 Table 6.7 Table 6.8 Table 6.9 Table 6.10 Table 6.11 Table Table Table Table

6.12 6.13 6.14 6.15

Table Table Table Table Table Table Table Table Table

6.16 6.17 6.18 6.19 6.20 6.21 6.22 6.23 6.24

XX

Examples of the suggested process choice versus the part characteristics 345 Examples of epoxy composite properties versus hardener and cure processing 352 Suggestions for the choice of processes versus thermoset nature 357 Example properties for composites with two reinforcements: matrix effects 370 Average composition and main property examples of the three main types of glass fibres used in polymer reinforcement 374 Typical mechanical and physical properties of various glass fibres 375 Examples of reinforcement ratios based on tensile strength and modulus of various reinforced polymers 376 Examples properties of various carbon fibres 379 Examples of reinforcement ratios of CFRP and enhancement ratios versus GFRP 381 Example properties of various aramid fibres 382 Examples of enhancement ratios obtained with incorporation of aramid fibres instead of glass fibres in a composite 383 Characteristic comparison examples of the three main fibres 383 Properties of some sustainable fibres compared to glass fibres 385 Example properties of various fibres 388 Example properties of a 60% glass fibre reinforced resin for different fibre forms 389 Example properties of PVC foams 391 Example properties for polystyrene foams 393 Example properties for polyurethane foams 393 Example properties for polyethylene foams 394 Example properties for polypropylene foams 395 Example properties for polymethacrylimide foams 396 Examples of properties of polyetherimide foam 397 Some typical properties of high performance syntactic foams 398 Examples of properties of polyethersulfone foams 398

Contents

Table 6.51 Table 6.52 Table 6.53

Property examples for polyamide nanocomposites processed by various methods 403 Property examples of a 2% nanosilicate filled polyamide 404 Property examples for various intermediate semi-manufactured thermoset and thermoplastic composites 411 Examples of self-reinforced polypropylene properties compared to other general-purpose solutions 413 Classification of the main reinforcement possibilities 444 Property examples of the same thermoplastic reinforced with the same level of the three main reinforcement fibres 445 Examples of nanocomposite properties 445 Property examples of short glass fibre reinforced plastics 446 Property examples of the same thermoplastic reinforced with increasing levels of the same short glass fibre 446 Property examples of the same thermoplastic (PA) reinforced with increasing levels of carbon fibres 447 Basic property example of short carbon fibre reinforced thermoplastics 448 Basic property examples of short aramid, glass and carbon fibre reinforced polyamide 449 Basic property examples of long glass fibre reinforced polyamides and polypropylenes 450 Basic property examples of long glass fibre reinforced BMCs 451 Basic property examples of glass fibre reinforced SMCs 452 Basic property examples of carbon fibre reinforced SMCs with epoxy matrix 453 Basic property examples of glass mat reinforced unsaturated polyesters 453 Basic property examples of glass mat thermoplastics (GMT) 454 Basic property examples of glass fabric and roving reinforced composites 455 Basic property examples of glass mat thermoplastics (GMT) 455 Basic property examples of carbon fabric reinforced acrylate urethane (unsaturated polyester) 456 Property examples of thermoplastic prepregs 456 Basic property examples of aramid reinforced acrylate urethane (unsaturated polyester) 457 Basic property examples of aramid reinforced UD epoxy composite in the fibre direction 457 Flexural modulus and maximum load examples for sandwich composites 458 Basic property examples of carbon reinforced UD epoxy and polyimide composites 458 Property examples of RRIM and SRRIM composites 459 Property examples of composites made of reinforced foamed matrices 460 Property examples of RRIM and SRRIM composites 460

Chapter 7 Table 7.1 Table 7.2 Table 7.3 Table 7.4 Table 7.5

Property examples of epoxy syntactic foams Examples of smoke emission for selected plastics Examples properties of conductive and neat plastics Selected properties example of fire-proofed epoxy and hybrid composite Annual growth (%) in major thermoset and composite consumption

Table 6.25 Table 6.26 Table 6.27 Table 6.28 Table 6.29 Table 6.30 Table 6.31 Table 6.32 Table 6.33 Table 6.34 Table 6.35 Table 6.36 Table 6.37 Table 6.38 Table 6.39 Table 6.40 Table Table Table Table Table

6.41 6.42 6.43 6.44 6.45

Table 6.46 Table 6.47 Table 6.48 Table 6.49 Table 6.50

465 465 466 466 472 xxI

Thermosets and Composites

Table 7.6 Table 7.7 Table 7.8 Table 7.9 Table 7.10

Property examples of BMC and glass fibre reinforced polyamide Processing and end-of-life scraps of glass reinforced polypropylene: property retention versus the number of recycling cycles Property retention (%) of BMC/SMC and polypropylene versus the level of BMC recyclate Comparison of the calorific properties of coal and plastic waste fuels Examples of properties of "extruded or injected woods" compared to PVC

479 488 489 489 491

Figures Chapter 1 Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig.

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14 1.15 1.16

World consumption evolutions - base 100 in 1985 Hardness of some materials Tensile strength (MPa) of various materials Tensile modulus (GPa) of various materials Specific tensile strength (MPa) of various materials Specific tensile modulus (GPa) of various materials Examples of fatigue failure Examples of material costs s Examples of material costs s Examples of ratios "Tensile strength versus costs per litre" Examples of ratios "Tensile modulus versus costs per litre" Thermoset before crosslinking or thermoplastic Thermoset after crosslinking Pyramid of excellence for some thermoset families Pyramid of excellence for some composite families Selection scheme of the material and process

4 5 6 6 8 8 11 13 14 15 15 16 16 17 19 30

World plastic consumption - Million tons Market shares based in the whole thermoset consumption Market shares based in the whole plastic consumption Market shares of the 3 main regions of composite consumption % Market shares of the 3 main composite matrixes Market shares of the 7 major plastic application sectors Market shares of the 8 major thermoset application sectors Market shares of the 9 major composite application sectors Market shares of the main thermoplastic processings Market shares of the main thermoset processings Market shares of the main composite processings Composite market shares in European countries Composite market shares for the main applications in Europe Composite market shares for the main applications in America End-life cost of the plastic parts Plastic raw materials: costs e per litre Additive panel Relative costs of various fibre reinforcements

32 35 36 37 38 39 40 41 42 43 43 45 46 48 50 51 52 53

Chapter 2 Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. XXII

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18

Contents

Fig. 2.19 Fig. 2.20 Fig. 2.21

Relative costs of various cores for sandwich composites Overspending of composites versus metal and ArF or CF composites versus GF ones Overcost of the CF composite versus GF ones

53 60 60

Chapter 3 Fig. 3.1 Fig. 3.2 Fig. 3.3 Fig. 3.4 Fig. 3.5 Fig. 3.6 Fig. 3.7 Fig. 3.8 Fig. 3.9 Fig. 3.10 Fig. 3.11 Fig. 3.12 Fig. 3.13 Fig. 3.14 Fig. 3.15

Tensile behaviour of polymers Continuous use temperature examples, ~ HDT A examples, ~ Density examples, g/cm3 Tensile strength examples, MPa Elongation at break examples % Flexural strength examples, MPa Flexural Modulus examples, GPa Compression strength examples, MPa Notched impact strength examples, Index without unit Heat modulus retention examples, % Fatigue examples, Index without unit versus cycle numbers Resistivity examples, loglo(ohm cm) Dielectric rigidity examples, kV/mm Dielectric loss factor examples, 10-4

149 168 169 170 171 172 173 174 175 176 177 178 179 180 181

Chapter 4 Fig. 4.1 Fig. 4.2 Fig. 4.3 Fig. 4.4 Fig. 4.5 Fig. 4.6 Fig. 4.7 Fig. 4.8 Fig. 4.9 Fig. 4.10 Fig. 4.11 Fig. 4.12 Fig. 4.13 Fig. 4.14 Fig. 4.15

Polyurethane: Ageing for 7 days. Tensile strength retention versus temperature of ageing Polyurethane: Ageing for 7 days. Elongation at break retention versus temperature of ageing Polyurethane: examples of tensile strength retention versus immersion time in hot water Examples of polyurethane foams: tensile strength versus density Vinylester composites. Tensile modulus retention versus testing temperature Vinylester composite (A) ageing at 160, 182, 204 ~ Examples of flexural strength retention versus time (month) Vinylester composite (B) ageing at 160, 182, 204 ~ Examples of flexural strength retention versus ageing time (month) Unsatured polyester. Tensile strength versus % and length of fibres Unsatured polyester. Tensile modulus versus % and length of fibres Unsatured polyester: Examples of creep deflection (mm) versus testing time (hours) Unsatured polyester. Notched impact versus % and length of fibres Unsatured polyester: Examples of endurance strengths versus the number of cycles in water Example of phenolic BMC ageing at 150 ~ up to 225 ~ Tensile retention versus time Example of ageing of two phenolic BMC: Modulus retention versus time at 225 ~ Glass fibre reinforced melamine: example of modulus retention versus temperature

188 188 190 194 209 210 210 211 211 212 212 213 229 229 242 XXIII

Thermosets and Composites

Fig. 4.16 Fig. Fig. Fig. Fig.

4.17 4.18 4.19 4.20

Fig. 4.21 Fig. 4.22 Fig. 4.23 Fig. 4.24 Fig. 4.25 Fig. 4.26 Fig. 4.27 Fig. 4.28 Fig. 4.29 Fig. 4.30 Fig. Fig. Fig. Fig.

4.31 4.32 4.33 4.34

Heat resistant epoxide: example of lifespan for 70% flexural strength rentention versus temperature 256 Epoxide: example of LN(half-life in days) versus 1000/T en ~ 256 Epoxide: example of creep versus time at 20 ~ and 80 ~ 258 Epoxide: example of creep modulus versus time at 23 ~ and 85 ~ 258 Epoxide dynamic fatigue: examples of SN curves. Maximum stress versus cycle numbers 259 Glass fabric reinforced epoxy composite: Example of dynamic fatigue: SN curves, maximum stress versus cycle numbers 260 Polyimides: Examples of flexural modulus retention versus temperature 279 Polyimides: Examples of half-life versus temperature 280 Polyimides: Examples of coefficient of friction versus temperature 281 Polyimides: Examples of creep modulus (MPa) versus time (hours) 282 Polyimides: Examples of lineic dimensional variation versus time (days) 282 Polyimides: Two examples of SN curves maximum stress (MPa) versus loading cycle number 283 Dynamic fatigue of polyimide: Two examples of maximum stress (MPa) versus temperature 283 Polyimide: Tensile strength and elongation retentions versus WeatherOmeter exposure time (h) 284 Silicone: Examples of tensile strength and elongation at break retentions versus temperature 302 Silicone: Examples of half-life versus temperature 303 Silicone: Examples of compression sets versus time 305 Polycyanates: Examples of tensile strength versus water content 319 Polycyanates: Examples of glass transition temperature versus water content 319

Chapter 5 Fig. Fig. Fig. Fig. Fig. Fig. Fig.

5.1 5.2 5.3 5.4 5.5 5.6 5.7

Thermoset processing methods Principle of the compression moulding Principle of the compression transfer moulding Principle of the high-pressure injection moulding Principle of the extrusion Principle of the RIM: Resin Injection Moulding Principle of the rotational moulding of a cylindrical tank

330 331 333 334 335 337 338

Chapter 6 Fig. Fig. Fig. Fig.

6.1 6.2 6.3 6.4

Fig. Fig. Fig. Fig. Fig.

6.5 6.6 6.7 6.8 6.9

XXIV

Schematic curve of a performance versus fibre length 347 Thermoset matrices: Examples of mechanical properties 356 Thermoset matrices: Examples of thermal properties 356 Neat thermoplastic matrices: Examples of continuous use temperatures at unstressed state 366 Neat thermoplastic matrices: Examples of HDT A (1.8 MPa), ~ 367 Neat thermoplastic matrices: Examples of tensile modulus, GPa 368 Neat thermoplastic matrices: Examples of tensile strength, MPa 369 Fibres: Examples of tensile strength versus modulus 371 Fibres: Examples of reinforcement ratios for short glass fibre reinforced PA6 372

Contents

Fig. 6.10 Fig. 6.11 Fig. 6.12 Fig. 6.13 Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig.

6.14 6.15 6.16 6.17 6.18 6.19 6.20 6.21 6.22

Fig. 6.23 Fig. 6.24 Fig. Fig. Fig. Fig. Fig.

6.25 6.26 6.27 6.28 6.29

Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig.

6.30 6.31 6.32 6.33 6.34 6.35 6.36 6.37 6.38 6.39 6.40 6.41 6.42

Ratios [Costs of short glass fibre reinforced thermoplastics/neat thermoplastics] versus costs of the neat grades 377 Glass, aramid, carbon fibre reinforced composites: Tensile modulus versus tensile strength examples 384 Schematic principle of a sandwich composite with foamed core 390 Example of sandwich panel made from an extruded polypropylene honeycomb core 399 Sandwich structure examples: Flexural strength versus density 401 Schematic structure of nanofillers 402 Sandwich structure examples: Flexural modulus versus density 402 Schematic structures of nanocomposites 403 Schematic manufacturing of SMC 405 Example of the effect of glass fibre level on flexural modulus 406 Example of the effect of glass fibre level on flexural strength 407 Example of the effect of glass fibre level on impact strength 407 Polypropylene GMT examples: Thermal and mechanical property examples 409 Polyester GMT examples: Thermal and mechanical property examples 410 Examples of various intermediate semi-manufactured composites: Modulus versus strength 412 Principle of the hand lay-up moulding 415 Principle of the vacuum bag moulding after hand or spray lay-up 417 Principle of the pressure bag moulding after hand or spray lay-up 418 Principle of the press moulding after hand lay-up or spray lay-up 419 Principle of the SRRIM: Structural Reinforced Resin Injection Moulding 421 Principle of the infusion process 422 Principle of the VARI - Vacuum Assisted Resin Injection 424 Principle of the compression transfer moulding 426 Principle of the high-pressure injection moulding 427 Principle of an automated tape placement machine 428 Principle of the filament winding 430 Principle of the pultrusion 431 Principle of the pullwinding 432 Schematic continuous sheeting 433 Principle of the stamping 435 Principle of the composite insert moulding 436 Principle of the extrusion-compression process 437 Principle of the sandwich structure 438

Chapter 7 Fig. Fig. Fig. Fig. Fig. Fig. Fig. Fig.

7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8

Laws and requirements of the market Design diagram Project diagram Thermoset types: Recent patents for a same period Fibre types: Recent patents for a same period Nanoreinforcements: Recent patents Structures and processes: Recent patents The waste collect and pretreatment

466 468 469 482 483 483 484 486 xxv

Disclaimer

All the information contained in this work was collected from reliable documentation and verified as far as possible. However, we cannot accept responsibility for the accuracy of the data. The characteristic data and economic figures are not guaranteed and cannot be used for calculations, computations or other operations to determine design, cost-effectiveness or profitability. The reader must verify the technical data and economic figures with his own suppliers of raw materials or parts, and other current technical and economic sources.

Acronyms and abbreviations 5V

UL fire rating

ABS

Acrylonitrile-Butadiene-Styrene

AMC

Alkyd Moulding Compound

ArF or AF

Aramid Fibre

ASA

Acrylonitrile Styrene Acrylate

ASTM

American Society for Testing and Materials

ATH

Aluminium TriHydrate

BF

Boron Fibre

BMC

Bulk Moulding Compound

BMI

BisMalelmide

CA

Cellulose Acetate

CAB

Cellulose AcetoButyrate

CAD

Computer Aided Design

CE

Cyanate Ester

CF

Carbon Fibre

CFC

ChloroFluoroCarbon

CIC

Continuous Impregnated Compound

CNT

Carbon NanoTube

CONC

Concentrated solution

COPE

COPolyEster TPE

CS

Compression Set

CUT

Continuous Use Temperature under unstressed state

Cy

PolyCyanate

DAP

DiAllyl Phthalate

DCPD

Poly(DicycloPentaDiene)

DMC

Dough Moulding Compound

DRIV

Direct Resin Injection and Venting

DSC

Differential Scanning Calorimeter

Thermosets and Composites

EB

Elongation at Break

EE

Electricity & Electronics

EMI

ElectroMagnetic Interference

EP

EPoxy

ESC

Environmental Stress Cracking

ESD

ElectroStatic Discharge

ETFE

Ethylene-TetraFluoroEthylene

FEP

Fluorinated Ethylene Propylene

FR

Fire Retardant

GF

Glass Fibre

GMT

Glass Mat Thermoplastic

HB

UL fire rating

HDT

Heat Deflection Temperature

HPGF

High Performance short Glass Fibre reinforced polypropylene

HSCT

High Speed Civil Transport (aircraft)

HTPC

Hybrid ThermoPlastic Composite

HTV

High Temperature Vulcanization

ILSS

InterLaminar Shear Strength

IMC

In Mould Coating

IPN

Interpenetrating Polymer Network

IRHD

International Rubber Hardness

IRM

International Referee Material

ISO

International Standardisation Organisation

LCP

Liquid Crystal Polymer

LCTC

Low Cost Tooling for Composites

LDPE

Low Density PolyEthylene

LEFM

Linear Elastic Fracture Mechanics

LFRT

Long Fibre Reinforced Thermoplastic

LFT

Long Fibre reinforced Thermoplastic

LGF

Long Glass Fibre

LIM

Liquid Injection Moulding

LRTM

Light RTM

LSR

Liquid Silicone Rubber

LWRT

Low Weight Reinforced Thermoplastic

XXX

Acronyms and abbreviations

MF

Melamine

O&M

Organisation & Methods department

PA

PolyAmide

PAI

PolyAmide Imide

PAN

PolyAcryloNitrile

PBI

PolyBenzImidazole

PBT

PolyButyleneTerephthalate

PC

PolyCarbonate

PCL

PolyCaproLactone

PCTFE

PolyChloroTriFluoroEthylene

PE

PolyEthylene

PEAR

PolyEtherAmide Resin

PEBA

PolyEther Bloc Amide

PEEK

PolyEtherEther Ketone

PEG

PolyEthylene Glycol

PEI

PolyEtherImide

PEK

PolyEtherKetone

PES or PESU

PolyEtherSulfone

PET

PolyEthylene Terephthalate

PETI

PhenylEthynyl with Imide Terminations

PF

Phenolic resin

PF1Ax

PF general purpose, ammonia free

PF2Cx

PF heat resistant, glass fibre reinforced

PF2Dx

PF impact resistant, cotton filled

PF2E1

PF mica filled

PFA

PerFluoroAlkoxy

PGA

PolyGlycolic Acid

PHA

PolyHydroxyAlkanoate

PHB

PolyHydroxyButyrate

PI

PolyImide

PLA

PolyLactic Acid

PMI

PolyMethacrylImide

PMMA

PolyMethylMethAcrylate

POM

PolyOxyMethylene or Polyacetal XXXI

Thermosets and Composites

PP

PolyPropylene

PPE

PolyPhenylene Ether

PPO

PolyPhenylene Oxide

PPS

PolyPhenylene Sulfide

PPSU

PolyPhenyleneSulfone

Prepreg

Preimpregnated

PS

PolyStyrene

PSU

PolySulfone

PTFE

PolyTetraFluoroEthylene

PUR

PolyURethane

PV

Pressure*Velocity

PVA

PolyVinyl Alcohol

PVC

PolyVinyl Chloride

PVDF

PolyVinyliDene Fluoride

PVF

Polyvinyl Fluoride

RF

RadioFrequency

RFI

Resin Film Impregnation

RH

Relative Humidity or Hygrometry

RIM

Reaction Injection Moulding

RIRM

Resin Injection Recirculation Moulding

RP

Reinforced Plastic

RRIM

Reinforced Reaction Injection Moulding

RT

Room Temperature

RTM

Resin Transfer Moulding

RTP

Reinforced ThermoPlastic

RTV

Room Temperature Vulcanization

SAN

Styrene AcryloNitrile

SATUR

Saturated solution

SB

Styrene Butadiene

SCRIMP

Seeman's Composite Resin Infusion Moulding Process

Si

Silicone

SMA

Styrene Maleic Anhydride

SMC

Sheet Moulding Compound

SN curve

Plot of stress or strain (S) leading to the failure after N cycles of repeated loading

XXXII

Acronyms and abbreviations

SOL

Solution

SP-polyimides

Condensation polyimides

SRRIM

Structural Reinforced Resin Injection Moulding

TAC

TriAllyl Cyanurate

TDI

Toluene-2,4-Dilsocyanate

TFE

TetraFluoroEthylene

TGA

ThermoGravimetric Analysis

TGV

High speed train

TMC

Thick Moulding Compound

TP

ThermoPlastic

TPE

ThermoPlastic Elastomer

TPU

ThermoPlastic polyUrethane

TR

Temperature-Retraction procedure

TS

Tensile Strength

UD

UniDirectional composite

UF

Urea-Formaldehyde

UL

Underwriters Laboratories

Unkn.

Unknown

UP

Unsaturated Polyester

UV

UltraViolet

V0 to V2

UL fire rating

VARI

Vacuum Assisted Resin Injection

VARTM

Vacuum Assisted RTM

VE

VinylEster

VIP

Vacuum Infusion Process

VST

Vicat Softening Temperature

ZMC

a highly automated process using Moulding Compounds

XXXIII

Table of Contents

List of tables and figures Disclaimer Acronyms and abbreviations Ch. 1

Outline of the actual situation of plastics compared to conventional materials

Ch. 2

The plastics industry: economic overview

Ch. 3

Basic criteria for the selection of thermosets

Ch. 4

Detailed accounts of thermoset resins for moulding and composite matrices

Ch. 5

Thermoset processing

Ch. 6

Composites

Ch. 7

Future prospects for thermosets and composites Conclusion Index

Chapter 1

Outline of the actual situation

of plastics compared to conventional materials

Thermosets and Composites

No engineer or designer can be ignorant of plastics, but the decision to use a new material is difficult and important. It has both technical and economical consequences. It is essential to consider: 9 The actual penetration of the material category in the industrial area 9 The abundance or scarcity of the material and the process targeted 9 The functionalities of the device to be designed 9 The characteristics of the competing materials 9 The cost 9 The processing possibilities 9 The environmental constraints. The goal of the facts and figures that follow is to help clarify quickly the real applications for thermosets and composites and the relative importance of the various material families and processes involved.

1.1 Polymers: the industrial and economic reality compared to traditional materials 1.1.1 Plastic and metal consumption

Usually, material consumption is considered in terms of weight (Table 1.1), but it is also interesting to examine: 9 The consumption or production in terms of volume (Table 1.2), which is the most important for fixed part sizes. 9 The consumption linked to the rigidity of the engineering materials (Table 1.3). In this last case, if the reference material, of unitary section area and unitary length, is M0 (volume V0 = 1) with Young's modulus E0, it can be

Table 1.1 World consumption or production by weight (million tonnes) Year

Plastic

Sted

A~minium

1970

30

595

10

1975

40

644

13

1980

48

716

16

1985

68

719

17

1990

92

770

19

1995

122

752

20

2000

147

848

24

Outline of the actual situation of plastics compared to conventional materials

Table 1.2

World consumption or production in terms of volume (million m 3) Year

Plastic

Steel

A~minium

1970

30

76

4

1975

40

82

5

1980

48

92

6

1985

68

92

6

1990

92

99

7

1995

122

96

7

2000

147

109

9

Table 1.3

World consumption at equal tensile stress (million m3*Young's modulus) Year

Plastic

Steel

A~minium

1970

60

15 000

300

1975

80

16 000

375

1980

96

18 000

450

1985

136

18 000

450

1990

184

20000

525

1995

244

19 000

525

2000

297

21 000

675

replaced with material M1 with unitary length, section area S1, and Young's modulus E l . For the same tensile stress: SI*E1 = l ' E 0 So: $1 = E0/E1 The volume of M1 with the same rigidity as M0 is: V1 = $1"1

= V0*E0/E1

therefore: V I * E 1 = V0*E0 Table 1.3 compares the rigidity-modified data for consumption. expressed as volume (million m 3) * Young's modulus (GPa). The tensile modulus is arbitrarily fixed at 2 for plastics, 200 for steel and 75 for aluminium. The annual consumption of plastics is: 9 Intermediate between those of steel and aluminium in terms of weight, that is, roughly a sixth of the consumption of steel and six times the consumption of aluminium for recent years. 9 Higher than those of steel and aluminium in terms of volume in recent years: roughly 1.4 times the consumption of steel and 16 times that of aluminium.

Thermosets and Composites

9

Lower than those of steel and aluminium if we reason in terms of equal rigidity: plastic consumption is equivalent to roughly 1% of the steel consumption and half that of aluminium. The average annual growth rate over the past 30 years is: 9 5 . 5 % for plastics 9 1.1% for steel. Over the 15 years from 1985 to 2000, the average annual growth rates are confirmed for plastics and steel (Table 1.4). The polymer composites also show a progression exceeding that of metals. Figure 1.1 displays these normalized changes in world consumption. Table 1.4

Growth in world consumption - normalized on 100 for reference year 1985

Plastics

Composites

Aluminium

Steel

1985

100

100

100

100

1990

135

150

112

107

1995

179

160

118

104

2000

216

190

141

115

Figure 1.1.

World consumption evolutions - base 100 in 1985

1.1.2 Mechanical properties 1.1.2.1. Intrinsic mechanical properties

Expressed in the same Vickers unit, the hardnesses of the engineering materials cover a vast range, broader than 1 to 100. The handful of example figures in Table 1.5 do not cover the hardnesses of rubbers, alveolar polymers and flexible thermoplastics... Table 1.5

Hardness

Examples of material hardnesses

Aluminium

PMMA

Steel

Tungsten

15

22

150

350

Glass 540

Tungstencarbide 2400

Outline of the actual situation of plastics compared to conventional materials

Figure 1.2 visualizes the hardnesses of a broad range of materials. Table 1.6 indicates the tensile characteristics of some traditional materials (metals, glass, wood) and polymers in various forms:

Figure 1.2. Table 1.6

Hardness of some materials Tensile properties of various materials

Tensile strength, MPa YieM stress, MPa Metals & alloys Min. Max. Min. Max. Steel Titanium Aluminium Magnesium

300 1000 75 85

Bulk glass Fibre glass

40 2000

1800 1000 700 255

200

1700

30 43

550 190

Tensile modulus, GPa

210 105 75 44

Glass 300 3500

55-85

Wood Wood

5

16

11

Polymer composites Unidirectional CF Unidirectional A r F Unidirectional G F SMC CF SMC GF

1800 1400 800 280 48

3000 1500 800 350 285

260 87 28 50 21

Long glassfibre reinforcedpolymers EP LGF

90

90

16

Short glassfibre reinforcedpolymers EP GF & Mineral P E E K 30% CF P E E K 30% GF

50 210 165

100 210 165

14 17 10

Neatpolymers PEEK Epoxy

80 70

90

4 4

Foamed polymers Expanded & foamed plastics 0.05 16 0.02-0.5 ArF: aramid fibre; CF: c a r b o n fibre; GF: glass fibre; L G F : long glass fibre; U D : unidirectional.

Thermosets and Composites

9

Unidirectionalcomposites, highly anisotropic.

9

S M C , 2 D quasi-isotropic.

9

LFRT, more or less quasi-isotropic.

9

Short fibre reinforced plastics, 3D isotropic.

9

Neat polymers, 3D isotropic.

9

Alveolar polymers.

The indicated figures are examples and do not constitute exhaustive ranges. Figures 1.3 and 1.4 show that: 9

Unidirectional composites in the fibre direction can c o m p e t e with existing metals and alloys. H o w e v e r , it is necessary to m o d e r a t e this good classification by taking account of these composites' high anisotropy, with low resistance and m o d u l u s in the direction p e r p e n d i c u l a r to the fibres.

9

The h i g h e s t - p e r f o r m a n c e engineering m a g n e s i u m and a l u m i n i u m alloys.

plastics

compete

with

Wood Engineering plastics _

Glass Other composites, UD perpendicular fibre Current metals & alloys _

UD Composites fibre direction l

I

l

10

100

1000

, MPa

10000

Figure 1.3. Tensile strength (MPa) of various materials

Wood Engineering plastics Other composites & UD perpendicular fibre UD Composites fibre direction Current metals & alloys !

10 Figure 1.4. Tensile modulus (GPa) of various materials

!

100

,GPa 1000

Outline of the actual situation of plastics compared to conventional materials

1.1.2.2. Specific mechanical properties

The specific mechanical properties take account of the density and consider the performance to density ratio: [performance/density]. Due to the high densities of metals, the resulting classification (Table 1.7 and Figures 1.5 and 1.6) is different from that for the mechanical properties alone. Table 1.7

Specific tensile properties of various materials

Density

Specific tensile strength, MPa

Specific tensile modulus, GPa

Metals & alloys Min.

Max.

Steel

7.8

38

231

Titanium

4.5

220

222

23

Aluminium

2.8

27

250

27

Magnesium

1.75

49

146

25

16

120

12

21

27

Glass 2.5

Wood 0.4-0.75

13-27

Polymer composites Unidirectional CF

1.56

1154

1923

167

Unidirectional A r F

1.37

1022

1095

64

Unidirectional G F

1.9

421

421

15

SMC CF

1.5

187

233

33

SMC GF

1.8

27

158

3-12

50

9

Long glassfibre reinforcedpolymers EP L G F

1.8

50

Short glassfibre reinforcedpolymers EP G F & mineral

1.9

26

53

5-9

P E E K 30% CF

1.44

146

146

12

P E E K 30% GF

1.52

109

109

7

PEEK

1.3

62

62

3

Epoxy

1.2

58

75

3

2

17

0.4-0.6

Neat polymers

Foamed polymers Expanded & foamed plastics

0.02-0.9

ArF: aramid fibre; CF: c a r b o n fibre; GF: glass fibre; L G F : long glass fibre; U D : unidirectional.

Thermosets and Composites

Wood Glass Engineering plastics Other composites, UD perpendicular fibre Current metals & alloys UD Composites fibre direction !

1

!

10

100

i

MPa

'

1000

1000(

Figure 1.5. Specific tensile strength (MPa) of various materials

Engineering plastics Other composites & UD perpendicular fibre

m

Wood

m

Current metals & alloys UD Composites fibre direction

!

1

10

GPa

100

100C

Figure 1.6. Specific tensile modulus (GPa) of various materials

The graphs in Figures 1.5 and 1.6 show that: 9 Unidirectional composites in the fibre direction can compete with existing metals and alloys and some have the highest performances. However, it is necessary to moderate this good classification by taking account of their high anisotropy with low resistance and modulus in the direction perpendicular to the fibres. 9 The best of the other engineering plastics cannot match the high performance of the magnesium and aluminium alloys in terms of rigidity. 1.1.3 Thermal and electrical properties

Metals are characterized by their low coefficients of thermal expansion and their strong thermal and electric conductivities, whereas wood (except where there is excessive moisture), glass and polymers have high coefficients of thermal expansion and are electrical and thermal insulators. The loading or reinforcement of the polymers changes these characteristics:

Outline of the actual situation of plastics compared to conventional materials

9

The coefficients of thermal expansion decrease.

9

Carbon fibres, steel fibres, carbon blacks lead to more or less conducting polymer grades.

Table 1.8 displays some thermal and electrical characteristics of polymers and conventional materials. Table 1.8

Physical and electrical properties of various materials

Coefficients of thermal expansion, l ~Y6

Thermal conductivity, W/m.K

Electricalresistivity, loglo

Metals & alloys Copper

16-20

115-394

-7 to -8

Aluminium

20-25

237

-7 t o - 8

1.2

12-15

Glass 8.8

Wood 0.1-0.2

5: high hygrometry 8: for 12% moisture

Polymer composites Unidirectional CF Fibre direction

-0.04

50

38

1

Fibre direction

12

0.4

11-15

Perpendicular to the fibre direction

22

0.2

11-15

Perpendicular to the fibre direction Unidirectional GF

SMC CF

3

SMC GF

11-20

11

Short fibre reinforcedpolymers Epoxy CF

3-12

0.6-1.1

EP GF

12-20

0.6-1.2

P E E K 30% CF

15-40

0.9

5

P E E K 30% GF

15-20

0.4

15

14

Neat polymers Epoxy

60

0.2

15

PEEK

40-60

0.25

16

Foamed polymers Plastics

0.025-0.120

ArF: aramid fibre; CF: carbon fibre; GF: glass fibre; L G F : long glass fibre; U D : unidirectional.

Thermosets and Composites

1.1.4 Durability

Metals and glass generally support higher temperatures than polymers, which present a more or less plastic behaviour under stresses, leading to: 9 An instant reduction of the modulus and ultimate strength. 9 A long-term creep or relaxation. Polymers are sensitive to thermo-oxidation and, for some, to moisture degradation. The other polymers, unlike current steels, are not sensitive to corrosion. Table 1.9 displays some thermal characteristics of polymer and conventional materials. Metals have minimum melting points higher than 400 ~ and often higher than 1000 ~ whereas: 9 Thermosets because of the crosslinking cannot melt but decompose without melting as the temperature increases. 9 Thermoplastics melt in the range of 120 ~ for polyethylene to 350 ~ for high-performance thermoplastics.

Table 1.9

Thermal properties of various materials

Melting point (~

Long-term resistance temperature under unstressed s t a t e (~

Heat deflection temperature, HD T 1.8 MPa ( ~C)

Metals Iron

1535

Aluminium

1660

Magnesium

649

Polymer composites UD EP/CF

Non-fusible

150-230

UD E P / G F

Non-fusible

150-230

SMC E P / G F

Non-fusible

130-230

290

Short fibre reinforced polymers EP/CF

Non-fusible

130-230

EP/GF

Non-fusible

130-230

290

P E E K 30 CF

334

250

320

P E E K 30 G F

334

250

Neatpolymers Epoxy

Non-fusible

130-230

PEEK

334

250

10

150

Outline of the actual situation of plastics compared to conventional materials

The thermal behaviour of the polymers can be characterized: 9 Immediately, by the H D T (heat deflection temperature) under a 1.8 MPa load. For the chosen examples, the values vary between 150 ~ and 320 ~ In the long term, by the CUT (continuous use temperature) in an unstressed state. For the examples chosen, the values vary from 130 ~ to 320 ~ Polymers are sensitive to a greater or lesser degree to photo-degradation, which can limit their exterior uses. On the other hand, many polymers, including the commodities, are resistant to the chemicals usually met in industry or at home and displace the metals previously used for these applications" galvanized iron for domestic implements, gas and water pipes, factory chimneys, containers for acids and other chemicals... Polymers, like other materials, are sensitive to fatigue. Figure 1.7 plots some examples of fatigue test results according to the logarithm of the number of cycles leading to failure. To compensate for their handicaps in terms of properties compared to the traditional materials, polymers have effective weapons: 9 Manufacturing in small quantities or large series of parts of all shapes and all sizes, integrating multiple functions, which is unfeasible with metals or wood. 9 Possibility of selective reinforcement in the direction of the stresses. 9 Weight savings, lightening of the structures, miniaturization. 9 Reduction of the costs of finishing, construction, assembling and handling.

1000-

9~

100 -

10-

Magnesium ~ P O M / G ~ ~ C/GF Zinc

M ~ m

pSU

Log (number of cydes)

5

i

i

I

I

6

7

8

9

Figure 1.7. Examples of fatigue failure

11

Thermosets and Composites

9

9 9

Aesthetics, the possibilities of bulk colouring or in-mould decoration to take the aspect of wood, metal or stone, which removes or reduces the finishing operations. Durability, absence of rust and corrosion (but beware of ageing), reduction of the maintenance operations. Transparency, insulation and other properties inaccessible for the metals.

1.1.5 Material costs

Obtaining information on the prices is difficult and the costs are continuously fluctuating. The figures in the following tables and graphs are only orders of magnitude used simply to give some idea of the costs. They cannot be retained for final choices of solutions or estimated calculations of cost price. Usually, the material costs are considered versus weight but it is also interesting to examine: 9 The cost per volume, which is the most important for a fixed part size. 9 The cost linked to the rigidity for the engineering materials. 1.1.5. 1. Cost per weight of various materials

Table 1.10 and the graph in Figure 1.8 demonstrate that plastics and polymer composites are much more expensive than metals, even more specialized ones such as nickel.t Table 1.10

Order of magnitude of some material costs (~/kg) Minimum

Maximum

Thermosets DCPD

5

7

Epoxy

3

10

Melamine

2

4

Phenolic

2

7

Polyimide

70

160

Polycyanate

20

50

Polyurethane

3

7

1.7

2

2

5

4

7

0.8

160

0.2

0.4

Urea formaldehyde Unsaturated polyester Vinylester

Thermoplastics From commodities to high-tech

Metals Steel 12

Outline of the actual situation of plastics compared to conventional materials

Table 1.10

Order of magnitude of some material costs (~/kg)

Minimum

Maximum

Metals Special steel

1.4

2

Aluminium

1

2

Titanium

3

4

Copper

1.5

1.7

Nickel

5

6

0.6

0.8

Wood

Polymer composites Composite CF

140

Composite ArF

100

Composite GF

50

SMC

2-5

Composites Thermosets Thermoplastics Metals Wood

m i

1

Figure 1.8.

!

i

100

10

r

1000

Examples of material costs ~ / k g

1.1.5.2. Cost per volume of various materials

As for the specific mechanical properties, the high densities of metals modify the classification (Table 1.11 and Figure 1.9) of the various materials. Table 1.11

Order of magnitude of some material costs (~/litre)

Minimum

Maximum

Thermosets DCPD

5

7

Epoxy

4

10

Melamine

3

5

Phenolic

3

10

Polyimide

80

260

Polycyanate

24

60

Polyurethane

4

9

Urea formaldehyde

2

3 13

Thermosets and Composites

Table 1.11

Order of magnitude of some material costs (~/litre)

Minimum

Maximum

Tbermosets Unsaturated polyester

3

7

5

9

0.8

260

Steel

1.6

3.2

Vinylester

Thermoplastics From commodities to high-tech

Metals

Special steel

10

16

Aluminium

3

6

Titanium

13

18

Copper

13

15

Nickel

45

54

0.5

0.6

Wood

Polymer composites Composite CF

220

Composite ArF

140

Composite GF

100

SMC GF

4-10

Composites Thermosets Thermoplastics Metals Wood

II !

1

Figure 1.9.

10

......... | ' 100

~/litre 1003

Examples of material costs ~?/litre

According to the cost per volume: , Plastics are competitive. Only the very high performance plastics or composites are more expensive than metals. 9 Wood is the cheapest material. 1.1.5.3. [Performance~cost per litre] ratios of various materials

Table 1.12 and Figures 1.10 and 1.11 confirm that the composites are more expensive than metals for the same mechanical performances. It is necessary oexploit their other properties to justify their use. 14

Outline of the actual situation of plastics compared to conventional materials

Table 1.12

[Tensile properties/cost per litre] ratios of various materials Tensile strength (MPa per ~/litre)

Tensile modulus (GPaper ~/litre)

Metals & alloys Minimum

Maximum

Steel

187

562

65-130

Titanium

55

77

7

Aluminium

25

117

17

27

20

Wood 10

Polymer composites Unidirectional CF

8

14

1

Unidirectional A r F

10

11

1

Unidirectional GF

8

8

1

SMC G F

12

28

2-5

ArF: aramid fibre; CF: c a r b o n fibre; GF: glass fibre

Composites

Metals

Wood

1

Figure 1.10.

Figure 1.11.

!

!

10

100

MPaJ~/litre 1000

Examples of ratios "Tensile strength versus costs per litre"

!

!

10

100

GPa/~/litre 1000

Examples of ratios "Tensile modulus versus costs per litre" 15

Thermosets and Composites

1.2 What are thermosets, composites and hybrids? 1.2.1 Thermosets

Thermosets before hardening, like thermoplastics, are independent macromolecules. But in their final state, after hardening, they have a threedimensional structure obtained by chemical crosslinking produced after (spray-up moulding or filament winding) or during the processing (compression or injection moulding, for example). Figures 1.12 and 1.13 schematize the molecular arrangements of these polymers.

Figure 1.12. Thermoset before crosslinking or thermoplastic

Figure 1.13. Thermoset after crosslinking

Some polymers are used industrially in their two forms, thermoplastic and thermoset, for example, the polyethylenes or the VAE. Thermoset consumption is roughly 15-20% of the total plastic consumption. The links created between the chains of the thermosets limit their mobility and possibilities of relative displacement and bring certain advantages and disadvantages. 16

Outline of the actual situation of plastics compared to conventional materials

Advantages: 9

Infusibility: thermosets are degraded by heat without passing through the liquid state. This improves some aspects of fire behaviour: except for particular cases, they do not drip during a fire and a certain residual physical cohesion involves a barrier effect. 9 When the temperature increases the modulus retention is better, due to the three-dimensional structure. 9 Better general creep behaviour, the links between the chains restricting the relative displacements of the macromolecules, one against the other. 9 Simplicity of the tools and processing for some materials worked or processed manually in the liquid state.

Disadvantages: 9

The chemical reaction of crosslinking takes a considerable time that lengthens the production cycles and, often, requires heating, that is, an additional expenditure. 9 The processing is often more difficult to monitor, because it is necessary to take care to obtain a precise balance between the advances of the crosslinking reaction and the shaping. 9 Certain polymers release gases, in particular water vapour, during hardening. 9 The wastes are not reusable as virgin matter because of the irreversibility of the hardening reaction. At best, they can be used like fillers after grinding. 9 The infusibility prevents assembly by welding. The "pyramid of excellence" (see Figure 1.14) arbitrarily classifies the main families of thermosets according to their performances, consumption level and degree of specificity:

Figure 1.14. Pyramid of excellence for some thermoset families 17

Thermosets and Composites

9 Urea-formaldehydes (UF): old materials of modest properties. 9 Phenolic resins (PF) and melamines (MF): good thermal behaviour but declining. 9 Unsaturated polyesters (UP) and polyurethanes (PUR): the most used for their general qualities. 9 Epoxy (EP): broad range of properties. Some are used for high-tech composites. 9 Silicones (Si): flexibility and high heat resistance, physiological harmlessness. 9 Polyimides (PI): high-tech uses, limited distribution. 9 Polycyanates (Cy): highly targeted uses and very restricted distribution. 1.2.2 Polymer composites Polymer composites are made from" 9 A polymer matrix, thermoset or thermoplastic, 9 A non-miscible reinforcement closely linked with the matrix: fibres of significant length compared to the diameter, yarn, mats, fabrics, foams, honeycombs, etc. The consumption of composites with organic matrices is a few percent of the total plastic consumption. The main advantages of the composites are: 9 Mechanical properties higher than those of the matrix, 9 The possibility of laying out the reinforcements to obtain the best properties in the direction of the highest stresses. The development of the composites is held back by the recycling difficulties, attenuated in the case of the thermoplastic matrices. The "pyramid of excellence" (see Figure 1.15) classifies, as arbitrarily as for the thermosets, the composites according to their performances, consumption level and degree of specificity: 9 Unsaturated polyesters (UP) reinforced with glass fibres: the most used for their performances and low cost. 9 Phenolic resins (PF) reinforced with glass fibres: fire resistance, good performances and low cost. 9 Epoxy (EP) reinforced with glass fibres perform better than the UP/ GF. 9 Epoxy (EP) reinforced with aramid or carbon fibres or with honeycombs: high-tech and high cost composites performing better than the EP/GF. 9 Silicone (Si) reinforced with glass fibres: flexibility, heat resistance, chemical resistance and physiological harmlessness. I8

Outline of the actual situation of plastics compared to conventional materials

Figure 1.15. Pyramid of excellence for some composite families

9

9

Polyimide (PI) reinforced with aramid or carbon fibres or with honeycombs: very high-tech and high cost composites performing better than the EP composites. The consumption is limited. Polycyanate matrices: very specific uses, high-tech and high cost composites, very restricted distribution.

1.2.3 Hybrid materials

Hybrid materials are not really a clearly defined material category but result from a design method that associates, by integrating them closely, one or more polymers on the one hand and, generally, one or more other materials which provide one or more functionalities difficult or impossible to obtain with only one polymer. The limit between hybrid materials and associated ones is rather fuzzy. This definition does not regard as hybrids, for example, those polymers joined after their manufacture onto structures of metal or concrete. On the other hand, overmoulding on structural and functional inserts is regarded as hybrid. The hybrid techniques often associate polymers and metals and combine the benefits of the two material classes. The metal provides the rigidity and the overmoulded reinforced plastic keeps the shape of the metal and adds numerous functionalities. There is also a growing interest in the association of elastic polymers, which assume the sealing or damping functionalities, to rigid plastics or composites that have the structural role. One of the materials can be overmoulded on the other or the two materials can be co-moulded. 19

Thermosets and Composites

The polymer/metal hybrids allow, by associating simple and inexpensive plastic processes (injection moulding, for example) with simple and inexpensive metal processes (stamping, embossing, bending), the integration, thanks to the plastic elements, of the maximum number of functionalities: mountings, fastening points, fixings, cable holders, housings, embossings, eyelets, clips, etc. This leads to: 9 The elimination of the assembling stages of the suppressed components. 9 Reduction of the dimensional defects of the assembled components. 9 Avoids the welding operations able to cause metal deformations. This principle, in more or less complex versions, is applied to: 9 Front-end of recent cars such as the Ford Focus and VW Polo. 9 Footbrake pedals in metal/plastic hybrid. 9 Wheels of planes in hybrid metal/composite epoxy/carbon. 9 Car doors. 9 Frame-hull ( M O S A I C project) in hybrid composite/aluminium. Inversely, the polymer can sometimes provide the structural functions whereas the metal ensures a role not easily assumed by the polymer: 9 For high-pressure air tanks, it is a hybrid design that gives the best results: a thin metal liner ensures the sealing and is used as a mandrel to make the envelope by the filament winding technique. The aramid or carbon fibres ensure the mechanical resistance. The weight saving is 30-50% compared to the all-metal tanks while the costs are optimized. 9 The engines of the Polimotor and Ford projects are in hybrid composites of phenolic resins/glass fibres and epoxy/glass fibres with combustion chambers, cylinders and pistons in metal. This permits the direct contact with hot combustion gases that the polymer could not support. The composite provides the rigidity of the engine. 9 Certain incinerator chimneys are in hybrid stainless steel with inner lining in sandwich resin/glass fibres with core in foamed polyurethane. The materials associated with the polymers can also be concrete or wood: 9 Structural panels for individual construction, Azurel de Dow, made of wood and expanded polystyrene. 9 Rigid elements for the modular design of dwellings made of hollow structures of glass fibre reinforced unsaturated polyester filled with concrete. 1.3 Plastics: an answer to the designer's main problems

Designers are directly or indirectly subjected to economical, technical and environmental constraints. The thermosets and composites are well positioned to provide solutions. 20

Outline of the actual situation of plastics compared to conventional materials

1.3.1

Economic requirements

Cost savings on the total life of the parts. A polymer overcost can be compensated for by designing, processing, finishing, assemblage, operating and maintenance costs and by a longer durability. The plastics and polymer composites offer: 9 Design freedom: realization of all shape and size parts unfeasible with metals or wood. 9 Integration of several functionalities by using the property versatilities such as structural and other additional properties: damping, shock and noise absorption, heat insulation, electrical insulation, translucence or transparency, rigidity of UD composites or flexibility of some polyurethanes, thermal stability of silicones, polyimides... 9 The possibility to combine two polymer materials to ensure several functionalities if all the desired characteristics are not brought together in a single polymer. A polyurethane flexible foam and a rigid polyurethane can combine structural and damping properties in the same part. 9 The possibility of selective reinforcement in the direction of the stresses by selecting particular composites or by part drawing. 9 The reduction of design and production set-up times. 9 Weight reduction thanks to the good mechanical properties combined with low density. The resulting fuel saving in automotive, labour and handling savings in building and civil engineering...allow the reduction of the operating costs. 9 The aesthetics, the possibilities of bulk colouring or in-mould decoration to take the aspect of wood, metal or stone that remove or reduce the finishing operations. 9 The integration of functionalities, the large sizes permitted by certain processing methods, the particular processes of assembly lead to cost reductions of assemblage, to smoother surfaces without rivets or weldings favourable to aesthetic quality and to a greater aerodynamic optimization. 9 The opportunities of repairing the composites permit the recovery of expensive parts after damage. 1.3.2 Technical requirements

Solidity, reliability and permanence of the parts, increasingly harsher environments, higher temperatures... The plastics and polymer composites offer: 9 Durability, the absence of rust and corrosion (but beware of ageing). 9 Ease and reduction of maintenance. 21

Thermosets and Composites

Good fatigue behaviour, the slowness of the damage propagation, the possibility of targeting a damaged mode to preserve the essential functionalities of the part between two inspections. 1.3.3 Marketing requirements

Aesthetics, comfort, frequent renewal of the product ranges. The plastics and polymer composites offer: 9 Design freedom: realization of all shape and size parts unfeasible with metals or wood. 9 Adaptation to "niche" products. 9 Production flexibility: processing adaptability from the prototype to mass production. 9 The possibility to refresh or to renew the product lines more frequently thanks to the easier replacement and modification of tools with plastic than with metals. 1.3.4 Environmental requirements

The standards and regulations limit pollution and increase the level of recycled wastes. The plastics and polymer composites offer: 9 Weight reduction thanks to good mechanical properties combined with low density. This leads to fuel savings in automotive and transportation sectors, labour and handling savings in building and civil engineering..- that reduce the pollution. 9 The reduction or suppression of the periodic painting of metals contributes to a reduction in pollution. The recycling of wastes is difficult for the thermosets and composites because of the crosslinking and/or the presence of fibres broken during the recycling. 1.3.5 Some weaknessesof the polymer materials

Like all materials, polymers also have their weaknesses, general or specific. To start with, the reader may have noticed that all the quoted advantages are never joined together in the same polymer class. Moreover, polymers meet certain general obstacles as technical materials. Let us quote for example: sensitivity to impact, ageing, low rigidity, thermal behaviour, rate of production, recycling.

1.4 Outline of the technical and economic possibilities of processing A satisfactory combination of part, polymer and process is of the first importance: 9 Each process does not allow the fabrication of all types of parts 9 Not all polymers are suitable for processing by all the methods. 22

Outline of the actual situation of plastics compared to conventional materials

It is pointless to select a polymer of high performance if it is not, technically and economically, suitable to manufacture the part under consideration. For the choice of the process according to the part, the following points are the main ones to be considered: 9 The shape: parts of all shapes and limited sizes are, generally, manufactured by moulding by compression, injection, transfer and the derived methods such as RIM, RRIM, RTM... Parts of constant section are, generally, manufactured by pultrusion and derived methods. 9 The size" parts of enormous size are manufactured by hand lay-up, spray lay-up, centrifugal moulding, filament winding... 9 The aspect: a good aspect on the totality of the part surface is only obtained by moulding. The other processes leave either rough-cut sections or a more or less rough face. 9 The quantity to produce: the rate of output depends on the process. Injection moulding, RTM and SMC allow mass production whereas hand lay-up or spray lay-up moulding hardly exceed 1000 parts. 1.4.1 Thermosetprocessing

The processes used for thermoplastics are modified for the thermosets: 9 It is necessary to heat after obtaining the part shape for a sufficient time to crosslink the thermoset, which solidifies and gains its cohesion and final properties. 9 Due to the irreversible formation of a three-dimensional network during hardening, the thermosets cannot be processed by thermoforming or welding, and boiler-making is very limited. 1.4.1.1. Moulding the solid thermosets

They can be moulded by compression, compression-transfer and injection. Generally: 9 The part sizes are limited by the mould size and the press power. 9 The parts are isotropic. 9 The whole surface of the part has a good finish. Each process presents some particularities: 9 Compression moulding: o Is suited for small and medium output. o Thick parts are problematic because of the low thermal conductivity of the polymers. o Released gas cannot escape and induces voids and internal stresses. o Inserts are difficult to use. o Finishing is often essential. 23

Thermosets and Composites

o 9 o o o o o 9 o o o o o o

The o u t p u t rates are low, the m o u l d and press are relatively inexpensive, and the labour costs are high. Compression-transfer moulding: Is suited for m e d i u m output. The quality of the thick parts is particularly improved. Inserts are easy to use. Finishing is often simple. The o u t p u t rates, the mould and press prices, the labour costs are halfway b e t w e e n compression and injection moulding. Injection moulding: Permits total a u t o m a t i o n of the process. Is suited for mass production. The optimization of the moulding p a r a m e t e r s can be difficult and the part warpage is sometimes difficult to predict. Normally, finishing is unnecessary. A p a r t from the particular cases of resins filled with fibres and other acicular or lamellar fillers, the parts are isotropic. The output rates, the mould and press prices are the highest, and the labour costs are reduced to the minimum.

1.4.1.2. Moulding the liquid thermosets

They can be m o u l d e d by: 9 Simple liquid resin casting in an open or closed mould: o Is suited for small and m e d i u m output. o The part sizes are limited by the mould size. o Reinforcements can be arranged in the m o u l d before casting. o The parts are isotropic with neat resin or with isotropic reinforcements. o The aspect is correct for one part surface for open moulding, and for the whole part surface for closed moulding. A finishing step is often essential. o The moulds are inexpensive and there is no press but the labour costs are high. The output rates are low. 9 Low-pressure injection moulding, RIM, R R I M : o Are suited for m e d i u m output. o The part sizes are limited by the m o u l d size. o Reinforcements can be arranged in the m o u l d before injection. o The parts are isotropic with neat resin or with isotropic reinforcements. o The aspect is well finished for the whole part surface. o The moulds are pressure resistant and m o r e expensive than for the casting. A press and a mixing/injection unit are necessary but the labour costs are moderate. The output rates are in a m e d i u m range. 24

Outline of the actual situation of plastics compared to conventional materials

1.4.1.3. Secondaryprocessing

9 o o o 9

o

o

Boilermaking is reduced because of the 3D network that forbids thermoforming and welding. It is possible to use techniques such as machining, bonding of sheets, slabs, pipes, blanks... This technique allows the building of very large size tanks, cisterns, tubing, etc. from prototypes up to medium output. The workers must be skilled and the labour costs are high. Machining: practically all the thermosets can be machined to some degree by almost all the metal machining methods after adaptation of the tools and processes to a greater or lesser extent: Sawing, drilling, turning, milling, tapping, threading, boring, grinding, sanding, polishing, engraving, planing... The low thermal conductivity and the decrease of the mechanical characteristics at elevated temperature limit the machining temperature and it is necessary to cool and reduce the tool feed motion. Machining is suited for prototypes and low output of complex parts made from blanks whose mould could be simplified; it is also suited to making thick or tight tolerance parts.

1.4.2 Composite processing 1.4.2.1. Primary processes

The processes differ according to the nature of the matrix: 9 Thermosets: it is necessary to heat after obtaining the part shape for a sufficient time to crosslink the thermoset, which solidifies and gains its cohesion and final properties. 9 Thermoplastics: a cooling only may be necessary after obtaining the part shape. The processes are numerous and differ in their technical and economic possibilities. Let us quote for example: 9 Atmospheric moulding processes: hand lay-up, spray lay-up 9 Liquid moulding: RRIM, RTM, impregnation, infusion... 9 Solid state moulding: compression and injection, SMC, BMC, ZMC... 9 Prepreg systems 9 Bag moulding 9 Filament winding 9 Centrifugal moulding 9 Continuous sheet manufacture 9 Pultrusion 9 Sandwich composites... The process, the structure of the composites, the design of the parts, and the output are interdependent factors that cannot be isolated one from the others. 25

Thermosets and Composites

The shape of the parts must be adapted to the material and the process, which dictates certain conditions, for example, the maximum thickness, the thickness variations on the same part, the acceptable radius for the direction changes of the walls (depth of grooves, flanges, ribs...), the possibility of using reinforcement ribs and inserts, the possibility of creating apertures and cavities during the transformation, the aesthetics. The part sizes are limited by the tool sizes such as moulds, dies, autoclaves or winding machines and by the power and the size of equipment such as presses, bags, pultrusion machines... The following tables schematize some general technical and economic possibilities of various processes without claiming to be exhaustive. Other values may be recorded for the parameters concerned and not all the processes are examined. Table 1.13 shows some examples of the process choice versus the part characteristics. Table 1.13

Examples of the process choice versus the part characteristics

Part size, maximum area in m 2

Thickness, mm

Examples of parts

Smooth surface

Method

Virtually unlimited, <300

Unlimited 2-10

Ship

1

Hand lay-up

Virtually unlimited

Unlimited 2-10

Ship

1

Spray lay-up

Up to 15

1-10

Car body element

2

Resin injection

Up to 15

3-10

Car body element

2

Cold compression moulding

Up to 5

1-6

Car body element

2

Hot compression moulding mats and preforms

Up to 5

2-10

Car body element

2

Hot compression moulding prepregs

Up to 10

Housing

1

RRIM

Limited

Electric & electronic parts

2

High pressure injection

Up to 20

Aeronautics elements

Up to 4

Diameter from 5 cm up to 25 m * with specific equipment 26

1 to 10 and more

All

Autoclave

Automobile parts

2

Stamping

Pressurized tank

1

Filament winding

Outline o f the actual situation o f plastics compared to conventional materials

Table 1.13

Examples of the process choice versus the part characteristics

Part size, maximum area in m 2

Thickness, mm

Examples ofparts

Up to 30

3-15

Tube, pipe

Limited section

3-20

Profile

Limited section

1-4

Roof sheeting

Smooth surface

Method

1

Centrifugal moulding

All

Pultrusion

2

Continuous impregnation

*Manufacture on specific material developed for a particular part.

Table 1.14 shows examples of the economic characteristics of some processes. Table 1.14

Examples of economic characteristics of some processes

Method

Output, units

Cycle time

Investment

Labour cost

Hand lay-up

1-1000

30 min to several days

Low

High

Spray lay-up

1-1000

30 min to several days

Low

High

Resin injection

200-10 000

30 min to several hours

Medium

Medium

Cold compression moulding

500-20 000

5-30 min

Medium to high

Medium

Hot compression moulding mats and preforms

Mass production

1-10 min

High

Medium

Hot compression moulding prepregs

Mass production

2-5 min

High

Low

RRIM

1000-250 000

Medium

High pressure injection>10 000

High

Low

Autoclave

<5000

Medium

Medium

Stamping

Medium output

Medium

Low

Filament winding

<10 000

According to part

High

High

10 min to some hours

High

Low

Centrifugal moulding

Pultrusion

Continuous

Continuous

High

Low

Con tin uous impregnation

Con t in uous

Con tin uous

High

Low

1.4.2.2. Secondaryprocessing 9 Machining: practically all the composites can be machined to some degree by almost all the metal machining methods after adaptation of the tools and processes to a greater or lesser extent: 27

Thermosets and Composites

o

o

9 o o

o

9 o o

Sawing, drilling, turning, milling, tapping, threading, boring, grinding, sanding, polishing, engraving, planing... The low thermal conductivity and the decrease of the mechanical characteristics at elevated temperature limit the machining temperature and it is necessary to cool and reduce the tool feed motion. Machining is suited for prototypes and low output of complex parts made from blanks (whose mould could be simplified); it is also suited to make thick or tight tolerance parts. However it is necessary to make several points: Machining destroys the gelcoat if it exists. To avoid the risks of a later attack, it is necessary to re-make a new gelcoat locally. For the anisotropic composites, machining cannot be done in all directions. Drilling, for example, can be done only perpendicularly to layers. The carbon and glass fibres are very abrasive and quickly wear away high-speed steel tools. For intensive use, carbide or diamond tools are more suitable. Assemblage: Welding does not apply to the thermosets. For thermoplastics, the presence of fibres disturbs welding, which is not often used. Joining does not present particular difficulties and is used to assemble composite with composite or metal. The parts can have structural functions, such as, for example, the assemblage of a metal structure and a composite superstructure on a frigate. Joining avoids the damage of the composite by drilling and allows an excellent distribution of the loads.

1.4.2.3. Repair possibilities: a significant composite advantage

The large composite-made parts have the significant economical advantage of being rather easy to repair: 9 A good professional can correctly repair the most-common thermoset composites or those of intermediate performance. Surface damage can be repaired by: puttying, sanding, gel coating or painting. For deep damage, the repair is more complex: removal of the layer soiled by the external medium (for example, water for ships, chemicals for tanks...), in situ lay-up to replace the destroyed layer, gel coating or painting. 9 For the high-performance or sandwich composites, repairs, when they are possible, are always much more delicate. However, race boats are currently repaired after damage. 1.4.3 Hybrid processing

The constituents of a hybrid can be interlocked: 28

Outline of the actual situation of plastics compared to conventional materials

Mechanically: overmoulding of the polymer on the metal, which bears anchorages such as lugs, holes... Chemically: bonding of the polymer to the metal treated with a primer or adhesion of two compatibilized polymers. Certain thermosets such as polyurethane are easily bonded on metals but the adhesion of polypropylene and some other materials is difficult.

1.5 Environmental constraints The ecological constraints, which vary from country to country, are of two main types: 9 Toxicity and pollution 9 Recycling. 1.5.1 Toxicity and pollution

Without entering into details, let us recall some examples. These are far from representing the whole extent of the problem. 9 The obligation to respect limits of residual monomer rates. For example, after application of the urea-formaldehyde resin, the residual rate of formaldehyde is limited according to national regulations. 9 The use of heavy metals and halogens is more and more disputed. 9 Solvents, for example styrene, are subject to increasingly severe legal requirements. 1.5.2 The recycling of polymers

Polymer recycling presents technical and economic difficulties and is less advanced, industrially, than that of metals. In the automobile, for example, the rate of metal recycling is higher than 95 %. For polymers, recycling is only minor with isolated industrial achievements such as battery boxes. Volvo, for its recent $40 model, has achieved a 9-kg recycled plastic use. The main ways for recycling polymers are: 9 Re-use with virgin material in the same or another application. 9 Conversion into basic chemicals by chemolysis or thermolysis. 9 Energy production by combustion. Recycling the wastes is difficult for the thermosets and composites because of the crosslinking and/or the presence of fibres broken during the recycling. To be solved, recycling must be considered at the design stage in order to choose the best solutions for the part at the end of its life. Some general rules, to which there are of course exceptions, can be stated: 9 Part marking makes the later identification of the materials easier. 9 Avoid the use of incompatible polymers in the same part or subset. 9 Standardize the polymers used. 29

Thermosets and Composites

9 9

Choose the assembling methods leading to the easiest dismantling at the end of the lifetime. Preferably choose a material whose recycling will be possible in the same fabrication...

1.6 The final material/process/cost compromise The final choice of the design team results from many iterations concerning the functional properties, the environmental constraints, the possibilities to produce the part in the required quantities, and the price. The price considered may just be the part cost but can also include assembling, delivery, set up and end-of-life costs, taking account of durability, the savings in maintenance, etc. Figure 1.16 shows an example of the selection scheme for the material and process.

Figure 1.16. Selectionscheme of the material and process

References Websites

spmp.sgbd.com, worldsteel.org, www.world-aluminium.org

Papers [1] F. Pardos, Antec 2002 Proceedings, p. 2736 [2] E Szabo, International Polymer Science and Technology, Vol. 28, No. 11, (2001), p.T/1 [3] E Pardos, Antec 1999 Proceedings, p. 3034 30

Chapter 2

The plastics industry: economic overview

Thermosets and Composites

The decision to use a new material is difficult and important. It has both technical and economic consequences, making it essential to consider: 9 The abundance or scarcity of the material and the process targeted. 9 The cost. 9 The actual penetration of the material category in the industrial area. The goal of the following facts and figures is to help quickly clarify the real applications and the relative importance of the various families and processes. The figures are roughly estimated from professional or government studies and papers or news from technical reviews. These sources can indicate significantly different figures according to the methodology used (applications, whether or not the captive industry is taken into account, etc.).

2.1 Overview of the global plastics industry Worldwide plastic consumption is of the order of 150 million tonnes annually, with a turnover of $500 billion. Over the past five years, global plastic consumption has grown consistently by an average annual rate of 3 %, compared with 2% for steel. Table 2.1 and Figure 2.1 indicate the orders of magnitude of global plastic consumption. Table 2.1

Global plastic consumption

Commodity

Million tonnes

%

108

72

Engineering

7

5

Composites

5- 7

3-5

1

<1

Speciality

<1

<1

Others

27

18

Total

150

100

TPE

120

Commodity

100 80 60 40 20

Engineering

Others Composites

Specialty

0 Figure 2.1.

32

TPE

World plastic consumption - Million tons

The plastics industry: economic overview

The market shares for the major plastic families are estimated in Table 2.2; however, other figures can be found in other sources according to the applications taken into account and the areas considered. The market shares (order of magnitude only) for some engineering and speciality plastics were estimated (see Table 2.3). Table 2.2

Market share for the major plastics

Thermoplastics

Thermosets

Market share (%)

PE

27

PP

15

PVC

13

PS

9 Amino resins

PET

7 5

PUR

4

Unsaturated polyesters

3

Phenolic resins

1

PA

1

Other engineering resins

3 Other engineering resins

1

TPE

<1

Total thermoplastics

74 Total thermosets

16

Composites

4

Others

6

Total

Table 2.3

100

Market share for some engineering and speciality plastics

Thermoplastics

Thermosets

Market share (%)

Polyurethanes

A few %

Amino resins

A few %

Phenolic resins

A few %

Unsaturated polyesters

A few %

PET

Polyamides

Several %

1% to a few %

33

Thermosets and Composites

Table 2.3

Market share for some engineering and speciality plastics

2.2 Market shares of the various thermoset families in the main industrialized countries Table 2.4 and Figures 2.2 and 2.3 indicate: The market shares of the thermosets with the highest consumptions in the world, the U S A and Europe.z 9

The share of the thermosets in the total plastic consumption.

The identified thermosets represent 16% of overall plastic consumption. The distribution between the families varies from one area to another for phenolics, epoxies and aminoresins.For these, the variation perhaps comes from a problem of identification in the statistics, as some may include significant applications that are outside the framework of this book. 34

The plastics industry: economic overview

Table 2.4

Annual consumption of major thermosets (1000 tonnes and %) USA

Europe

Worm

kt

%

kt

%

kt

%

Polyurethanes

2800

36

1700

33

6200

31

Unsaturated polyesters

1700

22

700

13

4000

20

Phenolic resins

1600

20

600

12

3600

18

Amino resins

1400

18

1900

36

5000

25

300

4

300

6

1200

6

7800

100

5200

100

20 000

100

Epoxies Total for the major thermosets Total plastic consumption Major thermoset share of the plastic total

40 000

30 000

150 000

19%

17%

13%

Other thermosets Total thermoset share

Figure 2.2.

3% 16 %

Market shares based in the whole thermoset consumption

35

Thermosets and Composites

Polyurethanes Phenolics ~

Others ~

~

~

~

~

Amino resins

Epoxies ~Unsaturated Polyesters

Figure 2.3. Market shares based in the whole plastic consumption

2.3 Market shares of composites

In terms of weight, the share of composites in the total plastics consumption is relatively weak (4-5 %), but the share in terms of value is higher: roughly12%. The growth rate, 4-7% per year, is greater than that of the plastics industry as a whole. Asian consumption is specifically orientated to glass reinforced plastics (GRP) without significant production of advanced composites. Table 2.5 and Figure 2.4 show the consumption of composites in North America, Europe and Asia. Approximately 75% of composite matrices are thermosets, and 25% thermoplastics. The polyester resins are the most used, followed by polypropylene. The thermoplastic share is growing fast.

Table 2.5

Composite consumption in North America, Europe and Asia N. America

Europe

Asia

Composite consumption (million tonnes)

3.4

2.1

1.5

Share of global composite consumption (%)

48

30

22

36

The plastics industry: economic overview

Figure 2.4.

Table 2.6

Thermosets

Market shares of the 3 main regions of composite consumption %

Market shares for the main matrices used for composites

Thermoplastics

Market share, %

UP

65

EP

8

PF

1

Others

<1 PP Others

Total

24 1 100

37

Thermosets and Composites

Figure 2.5. Market shares of the 3 main composite matrixes

2.4 Market shares for the main application sectors Table 2.7 and Figure 2.6 indicate the approximate market shares consumed by different application sectors for plastics as a whole. The figures may vary according to geographical region and may evolve with time. Table 2.7

Market shares for the seven main plastic application sectors

Market

%

Packaging

39

Building & civil engineering

24

Automotive & transportation

13

Electricity & electronics

7

Sports & leisure

5

Furniture & bedding

4

Medical

1

Others

7

Total

9 9

38

100

Three application s e c t o r s - packaging, building & civil engineering, automotive & transportation-consume 76% of all plastics. The seven application sectors that each consume more than 1% of plastics together account for 93 % of all plastics consumption.

The plastics industry: economic overview

Figure 2.6.

Market shares o f the 7 major plastic application sectors

The consumption of thermoplastics predominates (as indicated by Table 2.4) and the market share distribution of the thermoset application sectors (see Table 2.8 and Figure 2.7) is significantly different from thermoplastics and consequently from the average for all plastics. Table 2.8

Market shares for the eight main thermoset application sectors

Market

Plastics as a whole OCkomTable 2. 7), %

Paints, adhesives, cements

Thermosets, % 53

Automotive & transportation

13

14

Building & civil engineering

24

7

Electricity & electronics

7

7

Furniture & bedding

4

7

Consumer goods

4

Mechanical & industrial

2

Packaging Others Total

39

1

7

5

94

100 39

Thermosets and Composites

Figure 2.7. Market shares of the 8 major thermoset application sectors

The paints, adhesives & cements sector consumes more than 50% of thermosets even though it is not listed in the main plastic application sectors. 9

The shares consumed by the automotive & transportation and electricity & electronics sectors are similar for thermosets and for plastics as a whole.

9

The building & civil engineering sector is approximately one third as important for thermosets as for plastics as a whole.

9

The thermoset market share of the furniture & bedding sector is approximately twice the average for the whole.

9

The packaging sector, which is a major application area for plastics as a whole, consumes barely 1% of the thermosets.

The consumption of composites (see Table 2.9 and Figure 2.8) is also atypical: 9 40

The building & civil engineering sector is the major consumer.

The plastics industry: economic overview Table 2.9

Market shares for the nine main composite application sectors

Market

Totalfor all plastics, %

Composites, %

Building & civil engineering

24

30

Automotive & transportation

13

25

7

16

Electricity & electronics Mechanical & industrial Sports & leisure

10 5

8

Shipbuilding

6

Aeronautics

3

Medical

1

Railway Others

1 1

7

Total

57

Figure 2.8.

100

Market shares of the 9 major composite application sectors

The composite market shares taken by the automotive & transportation, electricity & electronics, and sports and leisure sectors are approximately twice the average for plastics as a whole. 41

Thermosets and Composites

9 The shipbuilding sector consumes 6% of composites. 9 The aeronautics sector is a significant composite consumer, particularly in terms of turnover, because of the high proportion of advanced composites used with matrices such as epoxies, polycyanates, polyimides, PEEK, and reinforcements such as carbon fibres. 9 The packaging sectorisabsent.

2.5 Importance of the various processing modes For each type of polymer, there are several possible processing methods from which it will be necessary to choose to best suit the required geometries, production rates, targeted properties and economic context. Even for apparently similar processes (injection moulding, for example), the machines and the methodologies are different for thermosets than for thermoplastics. Thermosets must be crosslinked, which takes time and, in the majority of the cases, needs a heating stage. Finally, each plastic family uses specific processes. Figures 2.9, 2.10 and 2.11 give some indications of the distribution of thermoplastic, thermoset and composite consumptions according to the processing methods.

Figure 2.9. Market shares of the main thermoplastic processings 42

The plastics industry: economic overview

Figure 2.10.

Market shares of the main thermoset processings

Figure 2.11.

Market shares of the main composite processings 43

Thermosets and Composites

More than 50% of the thermosets are not involved in engineering uses and are processed with specific methods such as gluing, spraying, powdering, coating, varnishing, impregnation or agglomeration. A large proportion of the polyurethanes, accounting for approximately 20% of all thermosets, are foamed. Thermosets can be processed in bulk, liquid or powdered form and the other processing methods are therefore very varied: 9 Conventional moulding" compression, transfer, injection. 9 Low pressure injection moulding: RIM, RRIM. 9 Liquid moulding: cast, centrifugal. 9 Calendaring. 9 Extrusion: high and low pressure. 9 Encapsulation, inclusion. 9 Sintering. 9 Machining. Some thermosets are mono- or bi-component liquids that harden at ambient or elevated temperatures and can, subsequently, require a postcuring stage. Some of them are processed manually with very simple tools such as cast moulding, inclusion, and encapsulation. Composite processing uses specialized methods. SMC/BMC and GMT moulding are the main methods. There are also some manual processes such as: 9 Hand lay-up, currently used for large parts. 9 Prepreg, used for high-tech parts. 2.6 The european market The European market consumes 28% of the worldwide composite market. Table 2.10 and Figure 2.12 show the market shares for the main European countries. Table 2.10

Market shares (%) for the main European countries

Germany

28

Italy

18

France

15

United Kingdom

8

Spain

8

The Netherlands

7

Belgium

6

Others Total Europe 44

10 100

The plastics industry: economic overview

Figure 2.12.

Composite market shares in European countries

Germany is the largest producer followed by Italy and France. The market shares of the United Kingdom, Spain, the Netherlands and Belgium are approximately equal. Apart from the automotive & transportation sector, which is larger, and the electricity & electronics sector, which is lower, the market shares (see Table 2.11 and Figure 2.13)are similar to the global averages. If we consider turnover rather than tonnage, the classification of the endmarkets is appreciably different, as can be seen in Table 2.12. Table 2.11

Europe: market shares (% by weight) for the nine main composite application sectors

World

Europe

Building & civil engineering

30

33

Automotive & transportation

25

32

Mechanical & industrial

10

10

Electricity & electronics

16

8

45

Thermosets and Composites Table 2.11

Europe: market shares (% by weight) for the nine main composite application sectors

World

Europe

Sports & leisure

8

8

Shipbuilding

6

4

Aeronautics

3

3

Railway

1

1

Medical

1

1

100

100

Total

Figure 2.13.

Table 2.12

Composite market shares for the main applications in Europe

Europe: market shares (% value) for the nine main composite application sectors

Weight

Value

Automotive & transportation

32

33

Building & civil engineering

33

25

8

12

10

9

Sports & leisure Mechanical & industrial

46

The plastics industry: economic overview

Table 2.12

Europe: market shares (% value) for the nine main composite application sectors Weight

Value

Aeronautics

3

7

Electricity & electronics

8

6

Shipbuilding

4

4

Railway

1

2

Medical

1

2

100

100

Total

2.7 The north american market The division between the end-markets in North America (Table 2.13 and Figure 2.14) is noticeably different from the worldwide picture: 9 Automotive & transportation is the major sector. 9 Corrosion protection is the third-largest sector. 9 Shipbuilding is twice the world average. 9 Building & civil engineering and electricity & electronics are lower than the average.

Table 2.13

North America: market shares (%) for the nine main composite application sectors World

N. America

Automotive & transportation

25

31

Building & civil engineering

30

20

Corrosion protection Shipbuilding

11 6

11

16

10

8

8

10

5

Aeronautics

3

2

Railway

1

1

Medical

1

1

100

100

Electricity & electronics Sports & leisure Mechanical & industrial

Total

47

Thermosets and Composites

Figure 2.14.

Composite market shares f o r the main applications in America

2.8 Consumption growth trends 2.8.1 Thermosets

After an average increase of 3% per year during the 1990-2000 period, thermoset consumption is expected to increase by 4% per year during the next few years to give the results in Table 2.14. Table 2.14

Global consumption of major thermosets 1990-2005 (1000 tonnes and %) 1990

2000

2005

1000 t

%

1000 t

Polyurethanes

4900

31

7000

33

8500

34

Amino resins

3000

20

4000

20

4700

19

Unsaturated polyesters

3600

23

4500

21

5500

22

Phenolic resins

3100

20

4200

20

4700

19

900

6

1300

6

1600

6

15 500

100

21 000

100

25 000

100

Epoxies Total of the major thermosets 48

%

1000 t

%

The plastics industry: economic overview

Environmental regulations favour water-based or powder-based adhesives, coatings and so on Globalization promotes the transfer of general-purpose thermoset processing from Europe to Asia. 2.8.2

Composites

The growth of composite consumption in industrialized countries is approximately estimated at a few percent. Table 2.15 shows some trends for the USA. Table 2.15

Market shares and predicted growth for the nine main composite application sectors in the USA

% share of composite consumption

% annual change

Automotive & transportation

31

5

Corrosion protection

11

5

Shipbuilding

11

5

Electricity & electronics

10

4

Sports & leisure

8

4

Railway

1

4

Medical

1

4

Aeronautics

2

3

20

2

5

2

100

4

Building & civil engineering Mechanical & industrial Total

2.9 Structure of the plastic processing industry In Europe, there are approximately 29 000 companies specializing in processing plastics. They employ about one million people, and have sales of around ~100billion. These figures do not represent all plastic processing. A large number of enterprises are integrated into automotive, electrical/electronics, building and toys and games firms and are not taken into account in these statistics. SMEs employing more than 100 workers generate 75% of the plastic processing turnover. The general trend is towards alliances and mergers. In the USA, there are approximately 13 000 companies specializing in processing plastics, about half the European figure. They employ about 600 000 people, and have sales of around ~63 billion. A large number of enterprises, integrated into other industries, are not included in these statistics. 49

Thermosets and Composites

Compared with the U S A and Japan (Tables 2.16 and 2.17), Europe appears to have: 9 Smaller companies than the U S A (a smaller ratio of employees versus the number of companies), but larger ones than Japan. 9 The same order of productivity as the USA, but a noticeably lower productivity than Japanese firms (in terms of average turnover per employee). Table 2.16 Processing turnover statistics Turnover (million ~)

Average turnover (million ~) per company

Averageturnover (million ~) per employee

Europe

98 000

3.4

0.1

USA

63 000

4.8

0.1

Japan

86 000

4.3

0.2

Table 2.17 Processing company and employment statistics No. of companies

No. of employees

Ratio of employees to companies

Europe

29 000

1 000 000

34

USA

13 000

610 000

47

Japan

20 000

447 000

23

2.10 Plastic costs

Polymeric materials are intrinsically expensive, but their use becomes appealing if one takes into account the processing costs, the new technical possibilities that they permit and the total cost at the end of their lifetime. Figure 2.15 analyses the various cost components. I

I

I o'y merrawmateria II

IL

I

Processing

I I

Finishing

]

assembling

[

Operating, maintenance ]

I I Dismantling, recycling I Figure 2.15.

5O

End-life cost of the plastic parts

I

einforcements

I

The plastics industry: economic overview 2.10.1 Raw material costs

Most significantly, the price per litre varies from about ~ 1 to more than ~200 according to the nature of the polymer itself, the formulation of the grades and the inclusion of high-cost reinforcements including carbon fibres and so on. The highest prices relate to the most performing polymers and also the least used. Figure 2.16 illustrates this situation with, for comparison, the approximate prices per litre of conventional materials" 9 ~1.75--~14 for iron and steel. 9 ~1 for wood. PP PE PVC PS UF

UF

ABS PET 1 PMMA 1 PA ! CA 1 MF 11 ACRYLIQUE IMIDE 1

uPi 9 PBT i l DCPD i -1

VEi1

MF

UP

DCPD VE

PC" 1 PF 9 ppE ~-1 PUR I POM" -!

PF PUR

EPil

EP

PA 110U 12i -ll PPS i --II PSU --ll PEI ----1 PAI - ----1 PESU" ----ll PTFE~ Polycyanate

Polycyanate

LCP ETFE i

PEEK PFA

PI /

PCTFE } 0

Figure 2.16.

50

100

150

200

per litre 250

300

Plastic raw materials: costs ~?p e r litre

51

Thermosets and Composites

2.10.2 Examples of additive costs

Apart from the reinforcements, the additives are numerous and some are more expensive than the raw polymer. Figure 2.17 displays the main additive categories. Additives Crosslinking Hardeners, curatives Promoters Inhibitors Aspect and dimensional stability Low-profile, low shrink Pigments, colourants Processing enhancers Wetting agents, thixotropics. Release agents. Cost cutters Cheap fillers, blowing agents Specific characteristics Dielectric Fire retardant... Figure 2.17. Additive panel

Table 2.18 indicates the comparative prices of resins and additives from the same suppliers and for appropriate small quantities. Table 2.18

Comparative prices of resins and additives

Additive Polymer

Resin cost (~/kg) Type

Cost (~/kg)

Epoxy

5-25

Hardener

20-40

Unsaturated polyester

1-7

Gelcoat

2-30

Styrene thinner

7-8

Wax 52

20

The plastics industry: economic overview

2.10.3 Reinforcement costs

The price of the fibrous reinforcements (Figure 2.18) depends on the nature of the fibres and the form of the reinforcement: continuous or chopped fibres, mats, rovings, fabrics or unidirectional. The prices of fibres cover a large range, which partly explains the low consumption of fibres other than those of E-glass. The prices of sandwich composite cores (Figure 2.19) range from 1 (reference) for balsa to 5 for the aramid honeycombs.

E-glass fibre

II

R-Glass fibre

II

Aramid Fibre

Carbon fibre Figure 2.18. Relative costs of various fibre reinforcements

Balsa

I

Aluminium honeycomb

PVC foam

Aramid honeycomb Figure 2.19. Relative costs of various cores for sandwich composites 53

Thermosets and Composites

2.10. 4

Processing costs

The following figures for processing costs are some examples of the orders of magnitude for specific cases; a different context can lead to a very differentcost. For a given processing technology, the processing costs are highly dependent on: 9 The annual production. 9 The size and shape of the parts. 9 The precision level. 9 The material cost. 9 The processing difficulties. 9 The recycling possibilities. The injection moulding cost of a part roughly represents the price of the raw polymer. The average selling prices are of the order of: 9 ~6/kg for building purposes. 9 ~9/kg for consumer goods. 9 ~ l l / k g for technical parts. Each model of parts requires the machining of a specific mould whose cost (for example g 5 0 000 or much more) is charged to the series of parts manufactured. The composites, even those that are mass-produced, always have a high added value. Table 2.19 displays some approximate average selling prices per kg. The choice of processing technology for composites is guided by: 9 The annual production. 9 The part size and its shape. 9 The chosen polymer and reinforcements.f

Table 2.19

54

Average selling prices of composites for different markets

The plastics industry: economic overview

Table 2.20 shows some examples related to a part weighing a few kilograms moulded in a glass fibre reinforced polyester. For another part, an automotive hood (bonnet), a more sophisticated element than the previous part, the costs are higher because of the complexity, the precision and the aesthetics. Table 2.20 Examples of mould prices (s and part costs expressed as the ratio [part price]/[raw composite price] Number of parts

1 O0 Mould prices (~?)

Hand lay-up

3000

RTM

10 000

SMC

150 000

200

1000

3000

10 000

Part costs expressed as [part price]/[composite price] 20

7 7

3

2.5 5

2

The next three tables display the most suitable technologies for each production range among: 9 SMC: the cheapest plastic processing technique for 100 000 units and above. 9 CBS: a special technology developed by composite manufacturer by SP Systems (Isle of Wight, UK), the cheapest technique in the range of 10 to some thousands of units. 9 RTM: an interesting technique for medium-sized production runs. 9 Prepreg, which competes with CBS for 10 units. In Tables 2.21, 2.22 and 2.23 the costs are compared with those obtained for steel. Steel is cheapest for the largest production runs but, perhaps, inishing costs are higher. Table 2.21

Automotive hood: unit cost (s for prototypes and small outputs

Units per annum

CBS

Prepreg

10

2300

2300

100

700

1000

Table 2.22

Automotive hood: unit cost (s for small and medium outputs

Units per annum

SMC

Steel

100 1000 10 000

1300 200

300

RTM

CBS

Prepreg

2300

700

1000

800

650

1000

600

600

55

Thermosets and Composites

Table 2.23

Automotive hood: unit cost (E) for mass production

Units per annum

Steel

SMC

100 000

60

115

1 million

35

100

Tables 2.24, 2.25 and 2.26 analyse some examples of the relative processing cost versus the annual production in units. The various technologies listed are not suitable for all materials or parts: 9

Machining is used with numerous materials.

9

Hand lay-up is used particularly for unsaturated polyester composites reinforced with glass fibres.

9

Rotational moulding uses liquid resins.

9

Vacuum forming uses thermoplastic sheets.

9

Blow moulding uses thermoplastics.

9

Injection moulding is used with thermoplastics and thermosets.

Table 2.24

Processing methods for prototypes (relative cost per unit)

Units per annum

Hand lay-up

Machining

1

700

150

10

70

125

Table 2.25

Processing methods for small and medium annual production (relative cost per unit)

~~ 100

25

110

1000

15

100

35

10 000

Table 2.26

~ ~

:~ 60

10

40

15

80

200

7

7

7

10

20

Processing methods for high annual production (relative cost per unit)

Rotational moulding, sophisticatedtooling

Blow moulding

Injection

100 000

3

2.5

2.5

1 million

2.5

1.5

1

56

The plastics industry: economic overview

The costs shown in these three tables are index-linked and do not have intrinsic value. The reference (base 1) is the part cost for injection moulding of 1 million parts per year. The comparison is only valid for these three tables. 2.10.5 Examples of part costs

The 9 9 9 9 9 9

cost of the finished parts is influenced by: The type of material, in particular, the reinforcement. The design, particularly the mass reduction. The annual production. The precision level. The aesthetics. The "high-tech" label, in particular for aramid or carbon fibre reinforced composites. Comparing prices for parts made from different materials: 9 For surgical parts, the replacement of stainless steel by liquid crystal polymer (LCP) leads to a material cost of the same order, but the ease of LCP processing compared to metal results in a lower final cost. The cost savings are about 50% for some standard parts and up to 90% for high-tech parts. 9 For racing canoes, Table 2.27 compares the unit price and the price per kg according to the reinforcement (glass or aramid fibres). The gap in the price per kg of 26% is reduced to 9% for the unit price because of the redesign of the part, which involves a 14% lightening.

Table 2.27

Racing canoes: glass and aramid fibre comparison

Unit price (~) GF

2334

ArF

2544

Unit price overcharge of the ArF versus the GF composite (%)

9

Weight (kg)

Price per kg (~/kg)

22

106

19

134

Overchargeof the price per kg (%)

26

Table 2.28 compares the prices of composite and conventional material parts sold by catalogue. Apart from the case of carbon fibre and glass fibre composites, the overspend on the carbon fibre decreases when the unit cost increases (Figure 2.20). The same behaviour is observed when aramid fibres replace glass fibres. The examination of these few examples, which are not exhaustive, shows that: 9 The replacement of a conventional metal by a composite involves a significant overspend. On the other hand, in the case of a special steel replacement, the composite solution leads to the same cost. 57

Thermosets and Composites

9 9

For a composite element, the replacement of glass fibres by aramid or carbon fibres involves a more limited overspend. In a special case, replacement of the conventional material (ebony) with a glass fibre composite leads to a drastic cost saving.

Table 2.28

Examples of prices for parts sold on catalogue

Type ofparts

Material

Unit price

Overchargeof the compositepart %

Aramid~bre versusglassfibre composites Canoe

Marine part

Unspecified part

GF

2,334

ArF

2,544

GF

2,276

ArF

2,512

GF

168

ArF

238

9

10

42

Aramid fibre composites versus metal Unspecified part

Alu

180

ArF

370

106

Carbonfibre composites versus metal Aeronautic part

Bicycle frame

Speedbar

Aeronautic push rod

Alu

Unknown

CF

Unknown

Steel/Alu

150 to 500

CF

500 to 1,500"

Alu

Unknown

CF

Unknown

Metal

Unknown

CF

Unknown

100

200 to 230

100

Negligible

Carbonfibre versusglassfibre composites Unspecified part

Chuffs

Chuffs

Unspecified part

Automobile part

Unspecified part

58

GF

234

CF

313

GF

217

CF

290

GF

183

CF

270

GF

134

CF

220

GF

115

CF

196

GF

114

CF

180

34

34

48

64

70

58

The plastics industry: economic overview

Table 2.28

Examples of prices for parts sold on catalogue

Type ofparts Unspecified part

Single seat cowl

Unspecified part

Unspecified part

Unspecified part

Material

Unit price

GF

110

CF

185

GF

106

CF

166

GF

98

CF

163

GF

90

CF

152

GF

48

CF

63

Overchargeof the compositepart %

68

57

66

69

31

Glassfibre composites versus metal Structural element for industry

Carbon steel

Unknown

GF

Unknown

Alu

180

GF

260

Marine part

Alu

75

GF

160

Marine part

Alu

55

GF

79 to 90

Corrosion-resistant steel

Unknown

GF

Unknown

Unspecified part

Offshore oil-rig element

50 to 150

44

113

44 to 64

negligible

Composites versusprecious wood Bow

Ebony

220 to 650

GF

60 to 110

-72 to -85

CF

580 to 1,700

160

Unspecified composite Artificial teeth

Hg/Ag

Unknown

Composite

Unknown

50 to 100

* The maximum cost comes from the carbon fibre composite cost and the over Alu: aluminium ArF: Aramid fibre

Hg/Ag: amalgam CF: carbon fibre

GF: glass fibre

59

Thermosets and Composites

Figure 2.20.

Overcost o f the CF composite versus GF ones

Figure 2.21 displays various composite overspends versus metal or other composites.

Figure 2.21.

Overspending o f composites versus metal and A r F or CF composites versus GF ones

For parts manufactured to order in small quantities, sometimes a single unit, the prices can be considerably higher (see Table 2.29).However, they can remain competitive for many reasons, some of which are explained in the next paragraph. 60

The plastics industry: economic overview

Table 2.29

Examples of parts manufactured to order in small quantities: Unit costs

Part

Offshore oil rig

Composite

GRP

Conventional material

Ratio o f unit costs:

Composite versus conventional material

Unit cost (6s

Composite

Conventional material

Carbon steel

Unknown

Unknown

1.5-2.5

Corrosionresistant steel

Unknown

Unknown

Roughly equal

Bridge

14 m length GRP

Concrete

600 000

300 000

2

High-speed coach body

Composite

Aluminium

Unknown

Unknown

4

Building, consolidation plates

5 kg CF/EP

94 kg steel

Unknown

Unknown

10

Unsuitable

28 000

Not applicable

Not applicable

laminate

F1 Monocoque

1 m 2 - 60 plies

element

of CF/EP

2.10.6 Assembly, operating and maintenance costs: three factors to favour composites 2.10.6.1. Assembly cost savings

The redesign of the parts, the integration of several functions, and the choice of new assembly technologies are some of the most important sources of cost savings with plastics and composites. The high material costs of the cases previously listed are partly or completely justified by a drastic decrease of the assembly costs: 9 For the two-level high-speed coach, the sticking together of two moulded half-hulls replaces the multitudinous welds on the metal model. The substantial economy in work time compensates for the cost of the composite, which is four times higher than that of aluminium. 9 For the consolidation of existing structures with carbon fibre reinforced plates weighing 5 kg instead of steel ones weighing 94 kg, the material cost is widely compensated for by the reduction of the assembly cost in harsh environments: very isolated works, difficult access in mountains, etc. A single worker can operate without any means of heavy handling. 9 For a 14 m motorway bridge, the overspend is compensated for by the facility of installation due to the weight, which is a quarter of the traditional bridge. With delivery in two sections the bridge can be installed in one day. Traffic interruption is considerably reduced. 61

Thermosets and Composites

9

For an offshore oil rig the cost of a GRP part is currently identical to or lower than that of corrosion-resistant steel. In addition, the expenses for the installation are reduced (set-up time can be divided by four, reduced transport cost and less heavy lifting) and the costs induced are not more than: o 60-90% compared to carbon steel. o 40-80% compared to stainless steel.

2.10.6.2. Operating cost savings

The automotive and aerospace sectors are excellent examples of the compensation of materials overspend by the operating cost savings. The weight savings from the use of polymers and composites offer higher performances, for example: 9 Aeronautics, railway and other transportation: the total saving in mass makes it possible to increase the payload and speeds and/or to reduce fuel consumption. Consequently, the operating costs are reduced. 9 Engines: the weight saving on the moving parts allows an increase of the revolution or translation speed and a better yield while decreasing the vibrations and the noise. The overspend allowed for a traditional solution compared with a polymer solution is roughly: 9 ~300 per kg gained for a helicopter. 9 ~1200 per kg gained for a satellite. Table 2.30 displays examples of weight savings by composites. Table 2.30 Weight reduction by composites Application sector

Part type

Composite

Early material

Weightreduction

(%) Aeronautics

Automotive

Structural

Composite

Metal

15-45

Push rod

CF/EP

Metal

30

Streamlining

Sandwich: PVC foam/CF reinforced skins

Prepreg

30

Spring

Composite

Metal

30-50

2.10.6.3. Maintenance cost savings

The high material costs of some cases previously listed are partly or completely justified by a drastic decrease in the maintenance costs, mainly due to corrosion resistance. For example: . The current maintenance of the motorway bridge is simplified and the lifetime before major repairs is expected to be 75 years instead of 20 years, ensuring the final profitability of the project. 62

The plastics industry: economic overview

The corrosion resistance of the offshore oil rig element is expected to be sufficient to remain operational during the entire lifetime of the project without needing frequent repairs and/or replacements that have a high impact on the long-term profitability.

2.11 Survey of main markets 2.11.1 Automotive and transportation

Table 2.31 analyses North American and European consumption by the automotive and transportation sector for thermosets and composites: 9 By weight. 9 By share of the total consumption of thermosets. 9 The average annual variation over recent years. Table 2.31

Automotive & transportation: Consumption of thermosets and composites

Consumption in 2001 (million t)

Market share in the material family by weight, %

Averagegrowthper year (%)

North America Thermosets

1

14

Composites

1

32

6

Europe Thermosets

0.7

13

Composites

0.7

33

6

The growth of plastics in mass-produced passenger cars is slow since, for the same manufacturer and the same car category, the plastic percentage grew from 3% in 1968 to 12% in 1995 and was roughly the same in 2002. 2.1 1.1.1. Thermosets and composites in the automotive industry

The 9 9 9

car industry is subject to many constraints: Economic competition, worsened by production overcapacities. Margin reductions. Shortening of the development cycles especially for the small "niche" series. 9 Strengthening of pollution, recycling and energy regulations. All these reasons persuade the carmakers to lighten the vehicles, to improve the quality and the performances, to extend guarantees, to reduce development and manufacturing times, to reduce costs and to support materials that can be recycled. Thermosets and composites have many suitable properties to satisfy some of these requirements: 63

Thermosets and Composites

9

Ease and freedom of design (realization of forms impossible with metals). 9 Integration of functionalities. 9 Aesthetics. 9 Non-rusting (but beware of ageing). 9 Possibility of bulk colouring. 9 Damping properties (noise reduction). 9 Reduction of design and manufacturing times. 9 Adaptation to "niche" vehicles. On the other hand, recycling brings some particular problems due to the irreversible crosslinking of thermosets and the modification of the reinforcements' morphology. The use of thermosets and composites allows: 9 Cost savings: the carmakers support the use of materials and processes that facilitate construction and assembly. Composites allow the reduction of part numbers by the integration of functionalities. 9 Weight reduction: the need for fuel consumption savings and environmental constraints involve vehicle weight savings. The problem is particularly significant on account of the customers' requirements concerning progress in safety and comfort. 9 Ease of production: the vehicle models are refreshed and renewed more and more often. All these modifications require replacements and modifications of tools that are easier with plastics than with metals. 9 Noise reduction: the damping properties of plastics favour a reduction in unwanted noise. 9 Reduction of the finishing costs: plastics allow the integration of functions and, consequently, lead to the reduction of assembly costs. The possibilities of bulk colouring and in-mould decoration also contribute to the reduction of the finishing costs. To progress in the automotive industry, plastics must improve their performance characteristics, ease of processing, productivity and recycling, for example: 9 Better thermal resistance: under-hood applications are undergoing an increase of the service temperature. In the cockpit interior, temperatures are tending to increase due to the increase in glazed surfaces. The rise in lamp power and headlight miniaturization leads to a temperature increase in the optical system and reflector. For the body, painting on line requires a sufficient thermal resistance to tolerate the cooking temperature. Consequently, it is necessary to use new grades or new, more thermal-resistant families. 64

The plastics industry: economic overview

9 Better low temperature behaviour: regulations tend towards an increase in low temperature impact resistances and a more ductile behaviour. 9 Ease of processing: improved flow properties and processability leads to cycle time reductions and productivity gains. 9 Low finishing costs: bulk colouring, in-mould decoration, an intelligent design and an effective maintenance of the moulds reduces or avoids painting and other finishing operations, cutting the finishing costs.

9 Recycling: more effective solutions are sought. The development of the mono-material concept is not favourable to thermosets and composites. However, self-reinforcing thermoplastic composites such as self-reinforced polypropylene (Curv TM from BP), are promising. The use of thermosets and composites is growing in various segments of vehicles: 9 Damping and protective devices: polyurethane foams. 9 Body, external elements, structural parts. 9 Passenger compartment. 9 Under-the-hood and other mechanical elements. Some examples of thermoset and composite uses are listed below. Damping and protection: 9 Bumpers, composite inserts for energy-absorbing bumpers. 9 Bumper beams in GMT. 9 Polyurethane damping foams. 9 Polyurethane foams for safety padding of instrument panels or sun visors. 9 Polyurethane foam for energy-absorbing bumpers. 9 Steering wheels (possibly combined with airbag doors) in polyurethane with cellular core (foamed with pentane, without CFC or HCFC), possibly decorated by in-mould-painting. 9 Headrest in polyurethane with cellular core (foamed with pentane, without CFC or HCFC), possibly decorated by in-mould-painting. Body, external elements, structural parts: 9 Engine hood, trunk lid, hatchback, tailgate in composites. 9 Body of niche or medium output vehicles in glass fibre reinforced polyester composites (RTM, BMC or SMC). 9 BMC tailgate of the Volvo V70. 9 Truck fenders, rigid roofs, bumper skirts and spoilers in RIM polyurethane. 9 Fenders, roofs, sliding sunroofs, spoilers for niche or medium output vehicles in composites or RIM. 9 Doors in composites or hybrid materials. 65

Thermosets and Composites

9 9

9 9 9 9 9 9

9 9 9 9 9 9

9 9 9 9 9 9 9 9 9 9 9 9 9 9 66

Housing of rear view mirror, back ventilation grid, front-end (part integrating the grill and the headlight frame) in composites. Various crossbars (driving support, transmission, etc.), door reinforcements, leaf springs, commercial vehicle floors, trunks, luggage boxes, battery trays in composites. Monocoque (single shell) frames of special vehicles in composites. Body panels, doors, fenders in polyurea RIM. Body panels, doors, rear doors, bonnets in SMC (possibly foamed) or ZMC. Roofs or fenders of 4WD in glass fibre reinforced polyester composites, SMC. Inner doors in glass fibre reinforced polyester composites. Front-end in hybrid of glass bead loaded PA6 and stamped metal. Front-end in GMT. GMT protection shields beneath the engine. Hatchback doors, noise shields in GMT. Cabins of heavy lorries in glass and Kevlar fibre reinforced composites. Shelters, ambulance cells, trailer or special vehicle bodies in glass fibre reinforced polyester, SMC or hand lay-up. Sandwich panels with polyurethane or PVC foam cores for thermal insulation of semi-trailers, containers, isothermal and refrigerating vehicles. The skins are in glass fibre reinforced polyester composites or metal foil. Floors of isothermal semi-trailers in laminated sandwich reinforced with a plywood core. Thermoplastic composites for the vertical body panels of the Saturn by General Motors (1000 vehicles per day). Thermoplastic composites for the fenders of the Class A by MercedesBenz, the Scenic and Laguna by Renault. Thermoplastic skin over a SMC frame for the tailgate of the Class A by Mercedes-Benz. F1 hull in epoxy/carbon fibres. Frame of amphibious car in epoxy/glass/carbon/Kevlar. Frame-hull of concept car in composite/aluminium hybrid. Body parts of sandwich composite with epoxy foam core and two steel skins. Decklids in SMC for the Mercedes-Benz Coupe. Pickup truck boxes in SMC. Repair putty in SMC for body panels. SMC rear floor: one SMC part replaces 40 steel ones. SMC cabin step with integrated segment of wheel housing for Mercedes truck. Truck front panels in standard or low density SMC.

The plastics industry: economic overview

9 SMC roof and side spoilers for truck cabins. 9 Thermoplastic nanocomposites for the step-assist on the 2002 GMC Safari and Chevrolet Astro Van. 9 Underbody parts in self reinforced polypropylene (Curv) for the Audi A4. 9 Front-end of the Mini Cooper in long glass fibre reinforced polypropylene (Stamax). 9 Front-end in long glass fibre reinforced polypropylene (Compel). 9 DCPD: Running boards for vans with moulded-in footstep Passenger compartment:

9 Polyurethane foams are often used for comfort and, to a certain extent, for the passengers' protection. 9 Frames of front and back seats, seat slides, instrument panels, consoles, package trays, parcel shelves and trays, glove compartments in thermoset composites or GMT. 9 Door handles in composites. 9 Safety transparent sandwich composites for glazing: polyvinyl butyrate or ionoplast core and two glass skins. 9 Instrument panel substrates in long fibre reinforced thermoplastic (Verton). Under-the-hood compartment and other mechanical elements:

9 Engine covers, rocker covers, sumps, front-end (part integrating the grill and the headlight frames, the battery support, the ventilator frame, the radiator support); ignition systems, distributors, lids of distribution chain, heating and air-conditioning ducts, air filters, pulleys of water pump, steering columns, drive shafts are parts under development in thermosets and composites. 9 For lighting, the reflectors have seen the total replacement of metal, which rusted, by plastics and composites. 9 Engine covers and sumps in BMC. 9 Oil sumps in SMC. 9 Footbrake pedals in metal/plastic hybrid. 9 Pedal supports of Peugeot 405 in GMT. 9 Toothed belts in Kevlar reinforced polyurea (development). 9 Oil/gas separating membranes for shock absorbers, hydropneumatic suspensions, frame supports for 4WD, various bearings converted to polyurethane. 9 Paints and coatings for cars and planes converted to polyurethane or polyurea. 9 Engines (Polimotor, Ford projects) in hybrid composites of glass reinforced phenolic resin or epoxy and metal for the combustion chambers, cylinders and pistons. 67

Thermosets and Composites

9 Particle filter systems in SMC (BMW 3 and 5 series). 9 Steering housing in long glass fibre reinforced polypropylene (Celstran). 9 Proton battery tray in long glass fibre reinforced thermoplastic (Verton). Looking to the future of thermosets and composites, the factors that need development are: 9 Recycling organization: o Intelligent design: reduction of material diversity, polymer compatibility, marking of the parts, ease of disassembly. Development of the mono-material concept is limited to polyurethanes, permitting the production of hard and soft parts. The other thermosets are less adaptable because of the impossibility to obtain flexible parts. The GMTs based on polyolefin are compatible with TPO, but the fibres are broken during the recycling. The self-reinforcing thermoplastic composites such as the "Curv" self-reinforced polypropylene are promising. o The economical and technical aspects of waste collection and recycling itself, with its outlets, need to be worked on. o The development of technical and economical solutions for the re-use of the recycled materials. 9 Reduction of the raw material and processing costs. 9 Improvement of the characteristics, both the initial properties and after long-term use and ageing. 9 The replacement of metals by plastics and structural composites. 2.1 1.1.2. Composites in railway applications

The need and the possibility of their use in these applications are due to: 9 The increase of speeds and capacities, which imposes a reduction in the vehicle masses. 9 The commercialization of new products, in particular multipurpose materials bringing acoustic, thermal and aesthetic properties in reasonable thicknesses and weights. 9 The evolution towards a design adapted to the technical requirements (aerodynamics) and aesthetical trends. Composite materials are used externally for the realization of body elements of high-speed trains such as EuroStar and internally for varnishing and as structural elements including the creation of two-level coaches and complete trailers (TGV Duplex). The advantages of composites for railway uses include: 9 Lightness: the Duplex aluminium high-speed train makes it possible to transport 545 passengers at 300 km/h with a load of 17 tonnes per axle; the use of composite materials will make it possible to travel at 68

The plastics industry: economic overview

360 km/h while reducing the axle load to 16 tonnes in the same conditions of safety and comfort. 9 Corrosion resistance: the non-rusting behaviour makes maintenance simpler and cuts its cost. 9 Ease of assembly: for a two-levelled coach, it is sufficient to assemble two moulded half-hulls. One avoids the multiple welds essential to the constitution of the metal structures. The substantial economy in assembly time makes it possible to compensate for the cost of the composite, which is four times higher than that of aluminium. 9 The excellent vibratory, acoustic and thermal behaviour of composites improves the comfort of the passengers. On the negative side, the railway standards for fire performance and smoke emissions are particularly stringent, which brings problems for these materials with organic matrices. The first uses of composites and hand lay-up moulded glass fibre reinforced polyester in railways are more than 40 years old. They were mainly used in interior installations" window frames, ventilation ducts, floors, decorative laminates... At the end of 1950, a panoramic rail-coach was equipped with fuel tanks, a panoramic dome and two end-parts of glass fibre reinforced polyesters. This material, quite resistant from a mechanical point of view and having an attractive quality/price ratio, was then used again for many coaches and high-speed train noses. For the design of structural parts, the criteria of fire behaviour play a significant role and an interesting solution is a sandwich with epoxy resin skins and possibly some complementary protection such as aluminium foil, intumescing painting or metallic coating. For the French high-speed train, the TGV, the retained construction principle for the two-levelled coaches includes two half-tubes, one male and the other female, only requiring one type of mould thanks to the symmetry of the parts. The intermediate floor is independently manufactured and joined in the tube on two integrated beams. The parts are moulded with a vacuum bag and external heating metal mould process with 120 ~ prepregs. The investments are in line with the limited series. In a different area, a "snow metro" intended to serve a skiing piste with a maximum 33 % slope and a flow of 3000 passengers/hour, consists of a body in a glass/polyester M2/F3 composite, moulded with the hand lay-up technique and hung on an aluminium frame. The doors, fire exit wickets and the floor are made from a sandwich with a PVC foam core. The parts are vacuum moulded in complete mould, which ensures a suitable surface aspect with an economical tooling cost. Examples of operational or development parts for transportation, excluding automotive: 69

Thermosets and Composites

Comfort, soundproofing, damping 9 Polyurethane foam seats, backrests and headrests for high-speed trains. 9 Polyurethane foams for soundproofing. 9 Rigid polyurethane foams for thermal insulation of the heating ducts under frame of high-speed trains. 9 Rigid polyurethane foams for door fillings. 9 Carpet underlays in polyurethane. 9 Foams for saddles of two-wheelers. 9 Bumpers, energy-absorbing fenders in SMC. External and structural parts 9 High-speed train noses in glass fibre reinforced polyester. 9 Composites for various coach parts of high-speed trains weighing 23% of the total mass. 9 Station and rolling stock equipment for subways and other public transport in glass fibre reinforced phenolic resin satisfying the fire and smoke regulations. 9 Cable cars in epoxy/Kevlar/honeycomb (Nomex). 9 Sandwich composites for driver's cabs, bottom and covering panels of high-speed trains. Interior parts

9 9 9 9

9 9 9

Boat and plane interior elements in RIM. Seat frames in GMT, RTM or BMC. Partition panels for high-speed trains in glass fibre reinforced phenolic resin satisfying the fire and smoke regulations. Ceilings, outer and corridor sidewalls, toilet modules, sliding doors, luggage racks, folding tables, seats made of sandwich composites for high-speed trains. SMC luggage racks for trains. SMC pillars of Berlin S-Bahn. SMC window frames for high-speed trains.

Lighting 9 Reflectors in glass fibre reinforced polyester. 2.11.2 Building and civil engineering industry The building and civil engineering industry is a sector where new materials such as plastics penetrate slowly, except for the renovation market where the consumers directly measure the advantages of plastics. The plastic components bring" 9 Lower costs. 9 A better productivity. 9 Lightness. 70

The plastics industry: economic overview

9 9 9

Corrosion resistance. Ease of handling and installation. Aesthetics, possibility of being decorated to take on the aspect of wood, metal or stone. 9 Possibility of translucence or even transparency of certain resins. 9 Ease of maintenance. 9 Insulating properties. 9 Greater design freedom than for wood and metals. 9 Better price stability compared to wood. On the other hand, it is necessary to be careful of the ageing and the mechanical resistance. However, some examples of works built in the middle of the 1950s with glass fibre reinforced polyester show that longevity could be significant. The barriers to the development of composites in buildings are, inter alia: 9 Lack of experience and knowledge of these materials for building sectors. 9 The difficulty in transposing the experience gained in other industrial sectors. 9 The complexity of the choice and the sizing of these materials. 9 The comprehension difficulties between the contributors from different professions having very dissimilar mentalities. 9 The public image of plastics. 9 The harsh environment of building sites. 9 The rigour of implementation is not very compatible with the practices and the qualification of the building workers. Approximately 20% of all composites and polyurethanes are used in the building sector. For insulation, polyurethane foam lags far behind glass wool (more than 60% of the insulation market) and expanded polystyrene. In the USA, the annual rate of growth of plastics in the building and civil engineering industry is estimated at 5% up to the year 2000, which is double of the rate of growth of the building and civil engineering industry itself. Examples of operational or development parts for the building and civil engineering industry are: 9 Polyurethane foams for heat insulation of roofs, walls, ceilings, floors, and cores of sandwich panels for industrial construction. 9 Polyurethane foams for soundproofing. 9 Polyurethane sealing ribbons for concrete prefabricated elements. 9 Points of fence piles in RIM polyurethane. 9 Polyurethane cements for liquid seals for terraces, communal kitchens. 9 Liquid polyurethane for the realization of waterproofing coatings for terraces, settling tanks, balconies, car parks, roofs, tunnels. 71

Thermosets and Composites

9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

9 9 9 9

9 9

9 9 9 9 9 9 72

Splashed polyurethane coatings for building renovation. Polyurethane coatings for sport and recreation grounds. Polyurethane foams for thermal insulation of cold stores. Polyurethane foams for pipe insulation of district heating. Polyurethane foam half-shells for heating piping insulation. Polyurethane foams for insulation of refrigerating pipes. Polyurethane foams for insulation of oil tanks and pipelines. Plates of polyurethane elastomer for gravel screens. Polyurethane elastomer bushing for low-power tracked excavators. Polyurethane elastomer blades or scrapers for snowploughs. Silicone sealants for building frontages. Silicone sealants for glazing and windowpanes. Silicone spacers for glazing. Self-adhesive or clampable silicone seals for doorframes, doors and windows. Cellular silicone profiles for sealing. Roofs and weatherboardings of agricultural or industrial buildings, sporting equipment, general-purpose rooms and churches in glass fibre reinforced polyester sheets, possibly corrugated or ribbed. The first French building of this type (a church) was built in 1954. Bonnets, bodies, housings for equipment protection (elevators, ventilators, fans) in glass fibre reinforced polyester. Frames in pultruded glass fibre reinforced polyester. Dwelling modules in glass fibre reinforced polyester integrating walls, ceilings, electric installations, and shower rooms. Frontages of Heathrow Airport in sandwich Aerolam from Ciba (honeycomb aluminium with two skins of epoxy/glass fibre), and of Seville hospital in panels of Trespa from Hoechst. Load-bearing panels for individual construction, Azurel by Dow made of wood and expanded polystyrene hybrid. Frontages in a sandwich made of polyurethane or PVC foam core and skins of fire-resistant glass fibre reinforced polyester. The panels are attached on a steel framework. Panels in a sandwich of expanded polystyrene core with composite skins. Sandwich panels made from foamed polyester inlaid with fine gravel or sand on one face. Cornices, ornamental mouldings, sculptures in composites for hotels, casinos and buildings. Light partitions in sandwich composites based on phenolic resins for public buildings subjected to severe fire standards. Windows in pultruded profiles in the U S A and Canada. False ceilings in sandwich composites.

The plastics industry: economic overview

9 Pillars and beams out of pultruded tubes filled with concrete. 9 Cable shelves in pultruded profiles. 9 Gratings, duckboards made with pultruded profiles. 9 Formwork, coffering in glass fibre reinforced polyester. 9 Handrails for building sites in pultruded profiles. 9 Refilling of concrete cracks with epoxy resins. 9 Moulds in RTM for ceiling elements moulded in concrete. 9 Pedestrian bridge (120m length) in pultruded composites of continuous glass fibre mat reinforced polyester. 9 All-purpose bridges in glass reinforced plastics. 9 Cable shelves for the Channel Tunnel, in fireproofed acrylic pultruded sections. 9 Reinforcement of existing concrete structures by carbon fibre reinforced epoxy laminate. The plates weigh 5 kg versus 94 kg for the steel ones. The additional cost (10 times higher) is acceptable only for repairs in harsh environments. 9 Telegraph pole supports in glass fibre reinforced polyester (SMC). 9 Telephone posts centrifugally moulded in self-extinguishing glass fibre reinforced polyester. 9 Tiles of 30 cm by 1.2 m in GMT. 9 Gratings and duckboards in pultruded profiles for beaches and piers allowing the circulation of trucks. 9 Sluice gates in glass reinforced composites. 9 Sloping roof of petrol station in pultruded 40% glass fibre reinforced polyester profiles. 9 Chemical or wine tanks in glass fibre reinforced polyester up to 10 m in diameter by filament winding. 9 Piping in glass fibre reinforced polyester up to 10 m in diameter by filament winding. 9 Industrial chimneys in glass fibre reinforced polyester. 9 Desulphurization chimneys in glass reinforced vinylester and epoxy. 9 Incinerator chimney in a hybrid of stainless steel with a liner made from a sandwich of glass fibre reinforced polyester and a core of polyurethane foam. 9 BMC roof tiles, lighter and more aesthetic than clay and concrete ones. 9 BMC exterior spotlight housing: no paint or rust. 9 BMC sinks and counter tops for kitchens. 9 SMC gas metering cabinet. 9 SMC water gratings. 9 Balcony modules in SMC. 9 DCPD: excavator housings, tractor fenders for rear-wheels (John Deere). 73

Thermosets and Composites

2.11.3 Furniture and bedding

This sector consumes approximately 4% of plastics in total, including roughly 7% of thermosets. 33% of the polyurethanes are used to provide comfort. Generally, furniture is not listed in the composite consumption statistics. The main applications are decorative laminates for the kitchen and the bathroom, glass fibre reinforced polyesters for street furniture and seats for communal installations. In other uses such as garden furniture, communal and professional furniture thermosets and composites find few outlets. Table 2.32 indicates the consumption of polyurethane in the U S A and its evolution. Table 2.32

Furniture and bedding: polyurethane consumption in the USA

Consumption in 2000 (1000 t)

Average annual growth (%)

Comfort

397

3

Carpet underlay

258

2

2.1 1.3.1. Interior and communal furniture

Polyurethane foams are leaders in the comfort arena: 9 Mattresses, pillows, cushions of flexible foam, possibly multihardness. 9 Seats, backrests, armrests for chairs and armchairs. The structural function can be combined with comfort: 9 Structures of seats and other furniture in R I M polyurethane. 9 Seats out of polyurethane foam with a structural skin. For the other functions, the composites can bring: 9 Low or acceptable cost on condition that the design is reconsidered. 9 Suitable durability of aesthetics, colouring and aspect. 9 Mechanical behaviour. 9 Design freedom. 9 Adaptability of the manufacturing processes to the output. 9 Lightness and ease of assembly. 9 Minimum maintenance. 9 Good resistance to moisture, grease, hygiene and household chemicals for kitchen and bathroom furniture. Examples of marketed or development parts:

9

74

Decorative laminates with filled phenolic resin core and decorative skins out of amino resins for kitchen, bathrooms and other home or communal furniture (hospitals, schools, sporting and social equipment).

The plastics industry: economic overview

9

9 9 9 9 9 9 9

Decorative laminates with filled phenolic resin cores and decorative skins out of amino resins for professional furniture: superstores, office automation and industry. Decorative elements such as country-style exposed beams out of polyurethane rigid foam. Furniture parts out of polyurethane rigid foam. Baths in glass fibre reinforced polyester (SMC or hand lay-up) with polyester or acrylic resin or melamine gelcoats. Cabins or sanitary blocks in glass fibre reinforced polyester or cellulose fibre reinforced phenolic resin and melamine gelcoat. Coffee tables with plate in carbon fibre or Kevlar reinforced composite attached to a metal frame. Seats for communities in glass fibre reinforced polyester screwed on metal frames. Complete furniture of an exceptional room (Brochier room) of a famous hotel is of Aerolam sandwich from Ciba (aluminium honeycomb with two epoxy/glass fibre skins).

2.1 1.3.2. Outdoor furniture, street furniture

Composites can bring: Low or acceptable cost on condition that the design is reconsidered. 9 Weather resistance adapted to the lifetime of the parts, suitable durability of mechanical properties, aesthetics, colouring and aspect. 9 Mechanical behaviour. 9 Design freedom. 9 Adaptability of the manufacturing processes to the output. 9 Ease of mass production. 9 Lightness and ease of assembly. 9 Minimum maintenance. 9 Good resistance to moisture, grease and maintenance chemicals. For street furniture, it is necessary to provide a greater mechanical resistance (vandalism, intensive use, safety of fixings) and, possibly, fire resistance. Examples of marketed or development parts:

9 9 9 9

Translucent roofs in glass fibre reinforced polyesters. Benches of bus shelters in glass fibre reinforced polyesters attached on a steel flame. Hollow signposts of bus stops in glass fibre reinforced polyesters filled with polyurethane foam injected in situ. Traffic signs in glass fibre reinforced polyesters attached on a metal flame. 75

Thermosets and Composites

9

Cabins and doors of public toilets: the polyester is not always sufficiently resistant to vandalism and in such cases is replaced by stainless steel. 9 Public benches in BMC. 9 Parisian newspaper kiosks in glass fibre reinforced polyesters since 1982. 2.11.4 Aeronautics, space, armaments

Aeronautics, space and defence consumed roughly 3% of the composite tonnage. The high-performance composites are predominant and, consequently, the prices are much higher than the average cost for plastics. Composite uses in military aircrafts date from the 1950s for lightly loaded parts made of glass fibre reinforced polyester. The introduction of boron fibres in 1966 allowed composite applications in more technical parts such as an air deflector on the F i l l and the empennages of the F14 and F15, which contain only 2% of composites. From 1975, boron fibre, found to be too expensive, was replaced by carbon fibre and 1978 saw the appearance of the first elements of aerofoil and fuselage on the Harrier, 26% of which, except for engines and weapons, is composed of epoxy/carbon composites. The share of composites goes up to 40% on the F16 XL and the structure of the Rafale is primarily composites. For commercial aircraft, the first structural part was a flap of Concorde (1973) made of epoxy/carbon, followed by the drifts of Airbus, DC10 and Boeing 747. A T R 72 and 42 comprise approximately 20% of composites. For civil aviation the percentage can reach 80%. In high-performance composites: 9 The most commonly used resins are the epoxies (more than 80%) followed by the polyimides. Carbon fibre reinforced P E E K applications are starting to appear. 9 The most usual reinforcements are carbon fibres followed by aramid and high modulus glass fibres. Boron, quartz and silicon carbide have very specific uses. Interest in composites in aeronautical and space engineering results from: 9 The possibilities of lighter structures thanks to good mechanical properties associated with a low density. 9 The design freedom coming from the forms than can be realized and the versatility of the assembly processes. 9 Cost savings thanks to the possibility of function integration. 9 The absence of corrosion, countered by a relatively high sensitivity to ageing. 76

The plastics industry: economic overview

However, replacing metals by composites raises various issues that need to be taken into account to avoid problems: 9 The impact behaviour. 9 The thermal resistance. 9 The naturally insulating properties. 9 Degassing in the space vacuum. 2.1 1.4.1. Advantages of composites for aerospace applications

9

Structure lightening: compared to metal parts, those made from composites are 15-45% lighter, according to the technological level and the degree of functional integration. 9 Cost cutting: assembly simplification by functional integration, the favourable lifetime and the repair possibilities lead to a profit from manufacturing and operational costs. 9 Performances: the possibility of obtaining complex shapes; particular assembly processes lead to smoother surfaces due to the removal of rivets. Weight reduction permits a greater aerodynamic optimization and performance benefits. 9 Safety: because of their organic character, these materials are insensitive to corrosion but can be, on the other hand, relatively sensitive to ageing. Composites have the advantages of their fatigue behaviour, the slowness of damage propagation, the possibility of targeting a damaged mode to preserve the essential functions of the part between two inspections. 2.1 1.4.2. Disadvantages of composites

9

Ageing: the organic nature of these materials makes them sensitive to their environment" moisture, temperature, radiation and contact with various organic liquids. The combination of several of these parameters, or the simultaneous application of static and dynamic stresses can involve synergistic effects. However, some matrices are especially ageing resistant. 9 Electrical conductivity: polymer materials are naturally insulating, which obstructs electrostatic discharges. Carbon fibres improve the electrical conductivity to a certain extent. 9 Impact behaviour: composites are more or less sensitive to impact and it is necessary to take this into account in the designing, drawing and sizing of the parts. 9 Vacuum degassing: the polymer and additive choices, and certain pretreatments such as vacuum and thermal pre-treatments, can improve the degassing behaviour. 9 Quality: composite use requires a quality assurance system adapted to the lack of operational experience, the specificity of the products used and the complexity of the manufacturing processes. 77

Thermosets and Composites

2.1 1.4.3. Examples of operational or development parts

Electronic device box for shooting station: The structure has a complex shape, must be light and rigid and support numerous mechanical, optical and electronic devices. Produced at an output of 75 parts per month, it is moulded by R T M with epoxy resin on deformable carbon fabric preforms and various glass/epoxy or carbon/epoxy inserts. After machining thermoplastic parts and metal inserts are added. Empennage: this structural part is subjected to high stresses and elevated temperatures because of the hypersonic flying conditions: aerodynamic loading, vibrations, kinetic heating. Temperatures are in the range of 130600 ~ according to the location. It is moulded by R T M with a resin bismaleimide of high thermal and mechanical performance reinforced with carbon fabrics and braids. A TR72 jib cowk This aerodynamic part, slightly loaded, is made of a sandwich composite with a closed cell foam core covered with very thin carbon skins. It is R T M moulded with a profit of 30% compared to a traditional prepreg solution. High-pressure gas cylinders for oxygen storage: Aerospatiale Missiles markets such parts with a 0.3-4 litres capacity for 210-325 bars operating pressures. Initially, these parts were intended for nitrogen storage and were manufactured starting from an aluminium inner liner without a weld on which a composite glass/epoxy was wound. The storage volume compared to the mass of the bottle ranged from 200 to 300 1/kg. Currently, cylinders with a thin stainless steel inner liner are produced for oxygen storage used by fighter pilots. Stored volumes reach 400 1/kg. High-pressure gas cylinders for space use: filled with helium under several hundred bars, they are used in the propulsion systems of space vehicles and launchers. To save from 30% to 50% on mass compared to metal cylinders, while optimizing the costs, Aerospatiale uses a thin metal inner liner for sealing. This is used as a mandrel to manufacture the structural envelope by filament winding of Kevlar or carbon fibres to ensure mechanical resistance. The carbon fibres make it possible to gain a 10% mass reduction compared to Kevlar. For an operating pressure of 400 bars, the capacities are 3001. Rods for Airbus: Since 1994, Aerospatiale has produced stress transmission rods that equip certain sections of the Airbus planes. Made out of epoxy resin and carbon fibres, they bring a weight saving of roughly 30% compared to their metal equivalent, for a comparable cost. They are produced by filament winding on a hardened sand mandrel. Jet engine cone: A polyimide is selected for its high temperature behaviour. Aileron jack hood for Airbus plane: its principal function is aerodynamic and the stresses are moderate. The part is thermoformed from a blank cut out in a pre-consolidated reinforced thermoplastic sheet. In spite of the 78

The plastics industry: economic overview

high cost of this thermoplastic, the specific process implemented by Aerospatiale for this application leads to a 50% cost reduction compared to the use of thermoset prepreg. Fuselage panel: Aerospatiale is developing a fuselage panel (1.6 • 2 m) in carbon fibre reinforced PEEK. This thermoplastic composite is constituted of a skin reinforced locally in the window zone. A metallized latticework is integrated on the external face for lightning and other dielectric discharges. Propeller blades of Transalk The hybrid design comprises a base tulip of steel, a polyurethane foam core, a carbon fibre braiding, an external skin in Kevlar and an epoxy resin moulded by the RTM process. Helicopter rotor blades: Since 1970, Aerospace and MBB have made them of sandwich composites of foam or honeycomb cores and glass or carbon reinforced skins with metal for the leading edges. The ends of the Super-Puma rotor blades are equipped with a dismountable salmon of complex shape moulded in carbon/epoxy. This salmon is coated with nickel, constituting a good protection against rain erosion and lightning. The blades of tail rotors use traditional composite materials: glass and carbon reinforced epoxy. Plane wheel: The selected hybrid design comprises metal and epoxy/ carbon composite. Hydraulic fluid tanks for jet engines: The selected carbon reinforced bismaleimide resin is 180 ~ long-term resistant. Careenage for Atlantique2: The sandwich composite is made of a honeycomb core with glass and Kevlar fibre reinforced epoxy skins treated to favour electrostatic discharges. Polarizer for Mirage 2000: The double sandwich selected was made of epoxy/carbon/honeycomb/carbon/honeycomb/glass. Satellite antenna reflectors: These reflectors are made of carbon/ aluminium honeycomb or Kevlar fibre/Kevlar honeycomb sandwich hulls. Breakable cap of the Aster container: This cap is intended for the sealing of pressurized containers and launching tubes. It must be torn by the passage of the projectile. The part must perform well against external attacks, tear under a limited load without ejection of fragments and be lightweight with small overall dimensions. The solution of draping carbon/ epoxy prepregs was selected because of the possibility of locally intercalating very different materials according to the required functions. Directional jet pipes: The chosen technical solution to ensure mobility is to articulate the jet pipes thanks to a flexible hemispherical laminate made of metal and elastomer layers. Helicopter rotor boss: the hemispherical laminated system made of alternating metal and elastomer layers makes it possible to save 65 % of the price and 50% of the mass compared to the traditional mechanical solution. 79

Thermosets and Composites

Satellite solar panels: The structure is a sandwich composite with a honeycomb core and glass fibre reinforced epoxy resin facings. Stiffeners ofacousticalpanels: the polyimide is chosen for its adaptability to the space environment. Protection hoods: a reinforced polyimide is chosen for its mechanical and thermal properties. Ablative materials: 9 Composites of silica fibre reinforced phenolic matrix. These materials have a low thermal conductivity and density lower than 1.65. 9 A felt of silica fibres bound by an organic matrix with a very low density (0.25) presents high insulating characteristics and a good ablation behaviour. Tank travelling wheel: a glass fibre reinforced epoxy instead of metal leads to a weight reduction of 25 %. In addition to the parts already examined, let us consider other industrial or potential applications: 9 Epoxies and their composites" arms of centrifugal machines for pilot training, external kerosene tanks for helicopters, cryogenic tanks for rockets. 9 Polyimides: parts intended to function in space vacuum; thermal and mechanical protection for aeronautics. 9 Polyimide foam: soundproofing and thermal insulation of missiles, planes and helicopters; protection for equipment embarked on space shuttles; cryogenic protection on satellites; insulation of piping. 9 Silicones: high-temperature seals, connectors, shock and vibration absorbers; external joints for aircraft windows, hatches, doors; coatings for safety cables. 9 Polycyanates" structural parts for satellites, missiles, aeronautics, fuselage and airframe elements. 9 Polyethylene fibre (Dyneema by DSM) reinforced composites for anti-ballistic products such as safety cockpit doors for Boeing 737 or 757 and others. 9 Carbon fibre reinforced plastics for ailerons, flaps, doors and covers of Boeing and Airbus since 1983. 9 High-strength carbon fibre reinforced epoxy for empennage and floor beams of the Boeing 777 since 1991. 9 Carbon fibre reinforced plastics for space stations and satellites by NASA. 9 Camouflage supporting structures, telescopic cable rod sets, lattice masts and other lightweight structures in thermoplastic prepregs (Towflex). 9 Tubular bangalore torpedoes for mine clearing, mine detecting probes in thermoplastic prepregs (Towflex). 80

The plastics industry: economic overview

9 Wing leading edges in glass fibre reinforced PPS save 20% of weight for the Airbus A340-500/600. 9 Inboard lower access panels in carbon fibre reinforced PPS. 9 Carbon and Kevlar reinforced epoxy components for Helios, an unmanned aircraft that flies up to 25 000 m altitude. Its 75 m wingspan is longer than that of a Boeing 747 airliner and it weighs 700 kg. 9 Polycyanates: Electromagnetic and dielectric structures. 2.11.5 Shipbuilding, offshore, nautical sports The shipbuilding industry consumes 6% of the composites total, but is generally not listed in the thermoset consumption statistics. Composites are used for the construction of boats and ships from the dinghy to the mine hunter, ship superstructures and offshore oil rig elements and superstructures. 2.1 1.5.1. Composites in the shipbuilding sector

The glass fibre reinforced polyesters are commonly used, but the use of epoxy composites is growing in special ships and boats, in particular for racing, and for high-level sports... The interest in composites lies mainly in: 9 The possibility of moulding complex shapes of all sizes. 9 The ability to manufacture prototypes and small series. 9 The design freedom with the possibility of reinforcing specifically at desired places. 9 The aesthetics. 9 The durability: ageing resistance, non-rusting behaviour. 9 The mechanical performance. 9 The price/performance ratio. 9 The ease of maintenance. However, to achieve these goals it is necessary to take care with: 9 The choice of resins, reinforcements, fillers and other ingredients. 9 The exact application of the right formulations. 9 The manufacturing process" correct wetting of the reinforcements, absence of bubbles and other voids... 9 The gelcoat: correct application process, good adhesion to the substrate, adequate quality, suitable thickness... 9 The optimum hardening of the resin. 2.1 1.5.2. Composites in offshore oil rig construction

The possibilities for composites lie mainly in: 9 Weight reduction. 9 Anti-corrosion. 9 Reducing investment cost. 9 Operational cost cutting. 9 Safety. 81

Thermosets and Composites Weight reduction

Steel, the most common material for offshore construction, is denser than composites in the ratio of: 9 3.9 versus glass fibre reinforced epoxy. 9 5.1 versus carbon fibre reinforced epoxy. 9 5.8 versus Kevlar fibre reinforced epoxy. The possibilities of weight reduction by the use of composites instead of steel are less significant and can be roughly 15-30% in the most up-to-date cases. The weight of the oil rigs is appreciably reduced, making it possible to lighten the structures, which constitutes a significant asset for installations in deep water. The possibility of preferential orientation of the composite reinforcements leads to more design freedom than steel. Anti-corrosion

Corrosion is one of the main problems involved in steel use, H2S, CO2 and the chlorides associated with water and oxygen being particularly aggressive. The protection costs and the replacement of steel components represents roughly several billion dollars for the oil industry each year. The anti-corrosion properties of composites should thus generate significant savings. Reduced investment cost

Generally, the raw material cost is much higher for composites than for metals. So, the use of composites is only economically viable if the cost approaches that of the steel elements, either after installation or, in the worst case, at the end of life. The cost of a glass reinforced plastic part is currently 1.5-2.5 times that of carbon steel, but generally identical or lower than that of corrosionresistant steel. However, the installation costs are reduced (installation time can be divided by four, the means of transport and lifting are lighter) and the costs after installation are not more than: 9 60-90% compared to carbon steel. 9 40-80% compared to stainless steel. The lightness of the glass-reinforced plastics makes it possible to realize investment savings on the structures and the installed capacities of lifting. Operational cost savings

Due to corrosion resistance, parts remain operational during the entire project lifetime without needing frequent repairs and/or replacements. Indeed, direct maintenance costs are cut, expensive production pauses are reduced and operational times increase, with a great impact on the longterm profitability. 82

The plastics industry: economic overview

Safety The fireproofed glass-reinforced plastics behave well in the event of fire. The phenolic materials or special polyesters such as Modar are recommended for the most demanding applications. Moreover, experiments show that pipes, tanks and structures of glass-reinforced plastics can remain operational after certain hydrocarbon fires. The absence of the "hot" process used for steel welding also reinforces safety. The reduction of leaks due to corrosion results in a fall in the environmental contamination risks by anti-corrosive chemical substances. The glass-reinforced plastics, contrary to steels, do not generate sparks during impact events, contributing to safety improvements. 2.1 1.5.3. Barriers to composite use

Among the obstacles met by the glass-reinforced plastics as a technical material let us note: 9 The fact that the design criteria were implicitly worked out for steel. To take into account the anisotropy and the heterogeneity of materials, to study the damaging modes (beading, cracking after impact...) it is necessary to use calculation methods and software different from that used for steel. Consequently, they are less familiar to the engineering and design teams. The error margins and safety factors must be re-quoted. 9 The relative youth of these materials: it is necessary to systematically characterize the products and to take account of the spread of the results, not only the mean value. 9 Sensitivity to impact: to limit the exposure risks, it is useful to bring pipes together in pipe-galleries. 9 Large deformations under loading, creep: pipes, for example, must be supported by suitable devices. 9 Larger structure sizing. Examples of industrial or potential applications: 9 Polyurethane foam: seats, backrests, headrests, safety padding, mattresses, pillows for installation of boats, yachts... 9 RIM polyurethane: paddles. 9 Polyurethane elastomers: flexible coatings, coated fabrics for inflatable dinghies and lifeboats. 9 Unsaturated polyesters and their composites: shipbuilding from boats up to minesweepers including all types of race or pleasure boats, sailboards and surfboards, hulls of catamarans, hovercrafts, pilot boats; floating shopping-centre, dry-dock caissons, sluice gates. 9 Sandwich panels with foam core and glass fibre reinforced polyester skins: structures for offshore wellhead protection. 83

Thermosets and Composites

9 Fireproofed glass fibre reinforced polyester for offshore oil rigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors, gratings, handrails, duckboards, ladders. 9 Fireproofed glass fibre reinforced phenolic resins for offshore oil rigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors. 9 Epoxy composites" roofs and central hulls of race trimarans; ballasts and ballasting pipes for ships; piping and water tanks for fire safety systems of oil rigs; 25 m race monohulls, sailboards and race boats. 9 Epoxy sandwich composites: hulls of race boats, submarine elements. 9 Carbon fibre reinforced plastics for the America's Cup yachts. 9 Masts and booms of yachts. 2.11.6 Anti-corrosion equipment, mechanics, industry, tools The anti-corrosion market is the third largest for composites and consumes more than 10% of the total. The applications are as varied as are the thermosets and composites themselves. Some examples of industrial or potential applications are listed below: Anticorrosion

9 Unsaturated polyesters and their composites: gas washers, flue gas scrubbers, pipes and fittings for industrial sewage water, factory chimneys, chemical tanks, settling tanks. 9 Vinylester BMC: butterfly valves for water, acid and alkali solutions. 9 Epoxies and their composites: piping for desulphurization units of power stations, support profiles and coatings for vats; tubes for transport of suspended matter; piping for chemical and oil industry; fire protection systems for oil rigs; pipelines, seawater piping for nuclear or thermal power stations; cooling pipes for frozen water production units; high-length winding flexible pipes for oil prospecting; uncured inner lining for pipe renovation without trenching (the crosslinking is activated after the installation); proofing varnishes; tank and container inner coatings, enamels for household appliances, electrostatic powdering, fluidized bed coatings. 9 Polyimides: racks and handling cases for printed circuit board treatments. 9 Carbon fibre reinforced PEEK: wafer carriers. 9 DCPD: cell covers, sewage containment vessels, industrial drainage troughs. Anti-abrasion, sliding

9 Polyurethane elastomers: coatings, roller and cylinder coverings for paper and steel industries; lining of pump stators; solid tyres for forklift trucks, covering for travelling wheels of conveyors, escalators, 84

The plastics industry: economic overview

pulleys; guides for cables; anti-abrasion coatings and coverings for conveyors, pipes, sandblaster cabins, tanks of dump trucks for bulk transport, endless screws; bearings for looms, fire hose coating, elastic stamping cushions... Phenolic moulding powders: bearings. Polyimides" compressor rings, dry bearings, sliding plates, pump pads, joint seatings, guiding rollers of grinder bands, manipulator inserts for glass bottle demoulding. Compressor rings and bearings in carbon fibre reinforced thermoplastics (SUPreM). Bodies, formworks, frames of machines

9 RIM polyurethane: frames, formworks, hoods, panels, casings for machines, cases of humidifiers, cases of control monitors. 9 Glass fibre reinforced polyester: formworks, hoods, bonnets, panels, housings, casings for machines. 9 Pump housing in BMC. Tanks, containers, pipes

9 Unsaturated polyesters and their composites: high-pressure gas cylinders, pipes and fittings for industrial waste water, inner lining for pipe rehabilitation without trenching, tanks for chemicals, settling basins. 9 Epoxies and their composites: tanks for LPG, 0.5 up to 1000 litres compressed air tanks. Insulation, damping

9 Polyurethane foams: machine soundproofing, impact and vibration damping. 9 Melamine foams: soundproofing of machines, pumps, refrigerating units; insulating sleeves for vapour piping. 9 Polyimide foams" cryogenic applications. 9 Polyurethane elastomers: bearings, crane thrusts and travelling cranes. 9 Silicones: impact and vibration absorbers. Sealing, elasticity, flexibility

9 Polyurethane elastomers: hydraulic seals, bellows, seals, flue brushes for pipelines. 9 Phenolic moulding powders: axial joints. 9 Polyimides: compressor rings, pump pads. 9 Silicones: in-situ cast seals, high-temperature seals, cables for chemical or oil installations, tight and flexible joints, roller coatings, hot air sheaths, bellows, diaphragms, wires for control and monitoring circuits. 85

Thermosets and Composites

Transmission system

9

Polyurethane elastomers: couplings with teeth, plates or pins; conveying belts reinforced or not, drive belts notched or not, reinforced or not. 9 Polyimides: gears of variable speed transmissions, joint seatings.

Tools, prototypes, small series

9

RIM polyurethane: models, prototypes of mass production thermoplastic parts. 9 Epoxies: moulds for glass fibre reinforced polyester parts moulded by the hand lay-up process, synthetic polymer concretes, fixings, basis plates. 9 Silicones: moulds for the manufacture of decorative elements, casting of low melting point alloys, waxes, plastisols, polyurethanes, epoxies and unsaturated polyesters; matrices for the thermoforming process. 9 Epoxy syntactic paste for rapid tooling system (Vantico/Boeing process). Miscellaneous

9 Polyurethane elastomers: grinding stones and polishing discs. 9 Phenolic moulding powders: parts, cases and basis plates of gas meters. 9 Silicones: binders for refractory fillers in the manufacture of ablative products. 9 Carbon fibre reinforced thermoplastics (SUPreM): rapier wheel for looms. 9 Industrial paddle fan in long fibre reinforced thermoplastic (Verton). 2.11.7 Electricity, electronics

Electricity and electronics consume approximately 7% of thermosets and 16% of all composites. Thermosets have been in use for a long time, but they now have competition from thermoplastics. Some examples of industrial or potential applications are listed below: Structural applications

9 Unsaturated polyesters and their composites: dishes for satellite TV antennae, urban lampposts, cable shelves, frames of solar panels. 9 Epoxies and their composites: parabolic antenna elements, power semiconductor boxes, high-voltage insulating tubes for power lines, transformer rings, SF6 circuit breakers, coil supports, high-voltage insulators, fireproofed panels. 86

The plastics industry: economic overview

Cases, bodies, formworks

9 Unsaturated polyesters and their composites: electricity meter housing, low-voltage fuse boxes, low and medium-voltage boxes. 9 Phenolic moulding powders: cases, lids and base plates of switches, thermostats, electricity meters, gas meters. 9 Melamine and urea-formaldehydes: cases of electric distributors, electricity meters, regulators, distributors; housing of small electric motors, fuse and junction boxes, dimmer switches. 9 Outdoor electronic casings in glass reinforced thermoplastic (Tepex). Insulating parts

9 Unsaturated polyesters and their composites: supports of terminals, connectors, switch parts, housing and handles or soles of domestic irons, handles and buttons of grills and pressure-cookers; buttons. 9 Phenolic moulding powders: coil housing, basis plates, commutators, lamp sockets, switch parts, low-voltage engineering. 9 Melamine and urea-formaldehydes: low and high-voltage engineering, switches, low-voltage plugs and sockets, dimmer switches. 9 Epoxies and their composites" high-voltage insulators, printed circuit boards, LED encapsulation, overmoulding of coils, capacitor encapsulation; coating, encapsulation, impregnation of electric and electronic elements such as terminal plates, motors, transformers, and other components. 9 Polyimides: printed circuit boards usable up to 300 ~ bodies of generator coils, terminal plates and terminals, overmoulding of coils, insulating collar of chain saws, lamp bases, coil frames, connectors, insulation of rotor axis, parts of circuit breakers. 9 Silicones: seals and cables for external projectors, street lighting, medium and high-voltage insulation, semiconductor encapsulation; coating, casting, overmoulding, potting, encapsulation, filling of cards, circuit boards, and other components for electronics, data processing, electricity, aeronautics, space. 9 Syntactic foams: electronics encapsulation. Wire and cable insulation

9 Special polyurethane elastomers: telephone wire insulation. 9 Silicones: cables for outside projectors, street lighting, drying ovens, convectors, electric heating. Miscellaneous

9 Unsaturated polyesters and their composites: electromagnetic shielding. 9 Polyimides: air vents for slide projectors, discs of wiper thrusts, running wheel for microwave ovens, handles for electric ovens and other household appliances, part of spit-roasters. 87

Thermosets and Composites

9 Silicones: seals for solar panels. 9 Silicone foam for electronic component insulation. 9 Polycyanates: structural parts for radomes and other electromagnetic and dielectric applications. 9 Long carbon fibre reinforced polyamide (or other thermoplastics) provides electrical shielding. 9 Nickel-coated carbon fibre reinforced plastics provide electromagnetic interference (EMI) shielding. 2.11.8 Electric household appliances, refrigeration, office automation

Some examples of industrial or potential applications are listed below: Electric household appliances

9 Unsaturated polyesters and their composites: housing and handles or soles of domestic irons, handles and buttons of grills and pressurecookers. 9 Phenolic moulding powders: parts of domestic irons, handles and buttons of cookers; parts of toasters. 9 Polyimides: running wheels for microwave ovens, handles for electric ovens and other household appliances, parts of spit-roasters. 9 Silicones" proof seals for ceramic hobs, oven doors, connections for domestic irons, seals for washing machines and dishwashers, cables for tumble dryers and convectors, caps for TV anodes. Refrigeration

9

Polyurethane foams for thermal insulation of refrigerators, freezers and other refrigerating furniture. 9 Unsaturated polyesters and their composites: structural elements, bodies, roofs and doors for display units, refrigerated window displays, refrigerated mobile shops, refrigerated lorries and semitrailers, refrigerated vans and other vehicles, cold stores.

Office automation

9 Polyurethane foams: phonic, mechanical and thermal isolation; antistatic foams for electronics packaging. 9 RIM polyurethane: computer and video consoles; cases, hoods, housings, bodies of office machines, television sets, computers, cash registers. 9 Polyimides: sockets for photocopiers, parts for printers; paper/print drum separation arms and bearings for photocopiers; running wheels. 9 Silicones: roller flexible coverings for photocopiers, faxes, thermal printers; wire for computers, control and monitoring circuits. 88

The plastics industry: economic overview

2.11.9 Medical

The medical sector consumes 1% of composites and is not listed in the thermoset consumption statistics. However, it absorbs 7% of the total silicone consumption for uses linked to its harmless character, thermal resistance and sterilization behaviour. Some examples of industrial or potential applications are listed below: 9 Unsaturated polyesters and their composites: leg prosthesis, surgical corset, reconstructing plaster for tortoise shell. 9 Epoxies: artificial teeth for dentist training, vascular system naturalization of the kidney by resin injection, spectacle frames, encapsulation of cardiac stimulator, dental prosthesis, adhesives possibly conductive or transparent. 9 Silicones: valves for cephalic liquid, dummies, nipples, oxygen masks, blood transfusion tubes, caps for syringe, artificial ventricles, elements for pacemakers, plastic surgery, balls for valves, pharmaceutical stoppers, nozzles for artificial respiration apparatus, seals for dialysers, pistons for syringes, oxygen tubes, contact lenses. 9 Self-reinforced polymer implants by Bionx Implants. 9 Carbon fibre reinforced PEEK (Orthtek by Greene Tweed) for orthopaedics or trauma medicine. 9 Convertible wheelchairs in glass fibre reinforced thermoplastic (Tepex). 2.11.10 Sports and leisure

The sports and leisure sector consumes 8% of the total for composites, but is not listed in the thermoset consumption statistics. Polyurethanes are broadly used for damping, protection and shoe manufacture. Composites are often used for high-technology products and their applications in this sector continue to develop. Among the industrial or potential applications let us note: 9 Polyurethane foam: gym mat, balls, stuffing of rucksacks in foamcoated textiles. 9 RIM polyurethane: scale models, elements of structures and panels of juke-boxes. 9 Polyurethane elastomer: coated fabrics for waterproofed sports clothes, handles of ski sticks, and wheels of roller skates. 9 Unsaturated polyesters and their composites: fishing rods, swimming pools. 9 Epoxies and their composites: 3-ray wheels for race bicycles, suspension arm for high-tech bicycles, hoops for tents. 9 Carbon fibre reinforced plastics for tennis rackets, golf clubs, fishing rods. 89

Thermosets and Composites

9 DCPD for golfcart bodies and lawnmower housings. In the particular field of the shoe industry: 9 Polyurethane foam: soles for town or leisure shoes, ski boots, hockey, slippers for ski boots, shoe trees. 9 Polyurethane elastomers: soles of basic ski boots. Packaging Packaging consumes roughly 1% of the total for thermosets, but is not listed in the composite consumption statistics. 4% of North American polyurethane consumption, mainly rigid or semi-rigid foam, is absorbed by the packaging sector. Some examples of industrial or potential applications are listed below: o Polyurethane foams: flakes, chips, sheets, blocks are used for impact protection and damping in the packaging of various products such as cameras, electronic devices... o RIM polyurethane: structural packaging. o Unsaturated polyesters and their composites: high-tech or aesthetical packaging such as containers for nuclear industry, aeronautics and radomes; cases for double bass. o Halogen-free fire retardant SMC or BMC storage bins. o Urea-formaldehyde: decorative stoppers possibly with metallic aspect. o DCPD: Custom containers and pallets, structural packaging for engine storage and transportation. 2.11.11

decoration This sector is highly specific and is not displayed in the consumption statistics, but it shows the versatility of thermosets and composites. Some examples of industrial or potential applications are listed below: 9 Unsaturated polyesters and their composites: concrete for moulding of statues, knick-knacks and similar, blocks for sculpture, stainedglass windows, giant advertising articles, body and subjects for carrousels, play areas, leisure parks, theatre, cinema and TV decors. 9 Epoxies and their composites: sculptures by Delfino and other sculptors. 9 Silicones" moulds for the manufacture of elements of decoration, costume jewellery, curios, reproduction of statues and other works of art, moulding of footprints. 2.11.12 Art,

Miscellaneous applications 9 Polyurethane foams: sponges for cosmetic uses (powder puffs, eyeliner), paramedic (sponges for massage), domestic (toilet, scouring,

2.11.13

90

The plastics industry: economic overview

9

9

9 9

9

polish applicators), textile and clothing (shoulder pads, fabric lining for wall soundproofing); industrial (impregnation); hygiene (elastic belts for disposable nappies); paint rollers, polishing discs; air filtration: hoods, vacuum cleaners; liquid filtration; phonic damping, front panels of loudspeakers, lining of heavy masses. Unsaturated polyesters and their composites: buttons, scientific or electricity inclusions, sandable cements for metal or composite repairs; farm equipment, cabins of transformers, seat cockles, terrace coating, buffing wheels, careenages for race motorbikes, swimming pools. Melamines: tablewares, drink glasses, tooth glasses, knives, forks and spoons, "unbreakable" plates and cups, screw caps for food made of foodstuff grades, handles of domestic irons, buttons of lids, handles and buttons of pans, ashtrays. Urea-formaldehyde: Non-food parts of beautiful aspect, for example toilet seats, base plates of small household appliances. Aramid, glass or polyethylene fibre reinforced composites: ductile ballistic materials that absorb the projectile energy through deformation. Vinylester-based BMC for fuel cell plates.

2.12 Applications of the main thermoset and composite families 2.12.1 Polyurethane and polyurea Consumption

Polyurethane consumption represents 4% of the total for plastics or 31% of the total for thermosets. It progresses roughly at the same rate as plastics as a whole. Identified US consumption (Table 2.33) is divided into 43 % for flexible foams, 30% for rigid foams and 7% for the elastomers. Polyureas represent a small share of polyurethanes and are not indexed in the statistics. Examples of operational or development parts are listed below. Table 2.33

Polyurethane: US consumption in 2000 1000 t

%

1250

43

Rigid foam RIM

870

30

Binder, adhesive

320

11

Coating

260

9

Elastomers and sealants

200

7

Total

2900

100

Flexible foam

91

Thermosets and Composites

2.12.1.1. Foam application examples Furniture 9 Mattress, pillows, cushions of flexible foam, possibly multi-hardness. 9 Seats, backrests, armrests for chairs and armchairs. 9 Seats of foam with structural skin. 9 Decorative elements such as country-style exposed beams in polyurethane rigid foam. 9 Furniture parts in polyurethane rigid foam. Automotive and transport

9 9 9 9 9

9 9 9 9 9 9 9

Comfort, damping and protection. Seats, backrests and headrests. Headrests in polyurethane with cellular core (foamed with pentane, without CFC or HCFC), possibly decorated by in-mould-painting. Safety padding of instrument panels or sun visors. Steering wheels (possibly combined with airbag door) in polyurethane with cellular core (foamed with pentane, without CFC or HCFC), possibly decorated by in-mould-painting. Saddles of two-wheelers. Seats, backrests and headrests for high-speed trains. Energy-absorbing bumpers. Soundproofing. Rigid foams for thermal insulation of the heating ducts under frame of high-speed trains. Rigid foams for door fillings. Carpet underlay.

Building and civil engineering 9 Thermal insulation, soundproofing. 9 Heat insulation of roofs, walls, ceilings, floors. 9 Heat insulation of sandwich panels for industrial construction. 9 Insulation of refrigerating pipes, cold stores. 9 Half-shells for heating piping insulation. 9 Insulation of district heating pipes, oil tanks and pipelines. Packaging 9 Flakes, chips, sheets, blocks are used for impact protection and damping in the packaging of various products such as cameras, electronic devices... Industry 9 Machine soundproofing. 9 Impact and vibration damping. 92

The plastics industry: economic overview

Appliances

9

Thermal insulation of refrigerators, freezers and other refrigerating furniture. 9 Phonic, mechanical and thermal isolation. 9 Antistatic foams for electronics packaging. Shipbuilding

9

Seats, backrests, headrests, safety padding, mattresses, pillows for furnishing of boats, yachts...

Sports and leisure

9 9 9 9

Gym mat, balls, stuffing of rucksack in foam-coated textile. Soles for town or leisure shoes, ski boots, hockey, slippers for ski boots, shoe trees. Soles with integrated skin for town, safety, leisure shoes. Interior slippers with integrated skin for ski boots.

Miscellaneous

9

Sponges for cosmetic uses (powder puffs, eye-liner), paramedic (sponges for massage), domestic (toilet, scouring, polish applicators). 9 Textile and clothing (shoulder pads, fabric lining for wall soundproofing). 9 Industrial (impregnation); paint rollers. 9 Polishing discs. 9 Hygiene (elastic belts for disposable nappies). 9 Air filtration: hoods, vacuum cleaners; liquid filtration. 9 Phonic damping, front panels of loudspeakers, lining of heavy masses. 2.12.1.2. RIM application examples Automotive and transport

9

Fenders, roofs, sliding sunroofs, spoilers, bumper skirts for niche or medium output light vehicles or trucks. 9 Plane interior elements.

Building and civil engineering

9

Points of fence piles.

Packaging 9

Structural packaging.

Industry

9 Frames, formworks, hoods, panels, casings for machines; cases of humidifiers, cases of control monitors. 9 Models, prototypes of mass production thermoplastic parts. 93

Thermosets and Composites

Appliances 9 Computer and video consoles; cases, hoods, housing, bodies of office

machines, television sets, computers, cash registers. Furniture 9 Structures of seats and other furniture. Shipbuilding 9 Paddles. 9 Boat interior elements. Sports and leisure 9 Scale models, elements of structure and panels of juke-boxes. 2.12.1.3. Elastomer application examples Automotive and transport 9 Oil/gas separating membranes for shock absorbers, hydropneumatic

9

suspensions. Frame supports for 4WD, various bearings.

Building and civil engineering

9 9 9

Bushing for low-power tracked excavators. Blades or scrapers for snowploughs. Plates of polyurethane elastomer for gravel screens.

Electricity & electronics

9 9

Telephone wire insulation. Encapsulation of components.

Industry

9

9 9 9 9 9 9

Anti-abrasion: coatings, roller and cylinder coverings for paper and steel industries; linings of pump stators; solid tyres for fork-lift trucks; coverings for travelling wheels of conveyors, escalators, pulleys; guides for cables, anti-abrasion coatings and coverings for conveyors, pipes, sandblaster cabins, tanks of dump trucks for bulk transport, endless screws; bearings for looms, fire hose coating, elastic stamping cushions... Couplings with teeth, plates or pins. Conveying belts reinforced or not. Driving belts notched or not, reinforced or not. Hydraulic seals, bellows, seals, flue brushes for pipelines. Grinding stones and discs for polishing. Bearings, crane thrusts and travelling cranes.

Shipbuilding

9 94

Flexible coatings, coated fabrics for inflatable dinghies and lifeboats.

The plastics industry: economic overview

Sports and leisure

9 9 9

Coated fabrics for waterproofed sports clothes. Handles of ski sticks, wheels of roller skates. Soles of basic ski boots.

2.12.1.4. Coating and sealing application examples Automotive and transport

9

Paints and coatings for cars and planes in polyurethane or polyurea.

Building and civil engineering

9 9 9

Liquid polyurethane for waterproofing coatings for terraces, settling tanks, balconies, car parks, roofs, tunnels. Polyurethane cements for liquid seals for terraces, collective kitchens. Splashed polyurethane coatings for building restoration.

2.12.1.5. Polyurea Automotive & transport

9 9 9

Paints and coatings for cars and planes. Toothed belts in Kevlar reinforced polyurea (development). Body panels, doors, fenders in polyurea RIM.

Packaging

9

Decorative stoppers possibly with metallic aspect.

2.12.2 Unsaturated polyesters 2.12.2.1. Consumption

The consumption of unsaturated polyesters by the industrialized countries accounts for 13-21% of the total thermoset consumption and is approximately 2.7% of the total plastic consumption. According to the country, it has progressed or regressed slightly in the past few years. The shares, in percentages by transformation processes are summarized in Table 2.34. Table 2.34

Unsaturated polyesters: shares in % per process (estimations)

Composites

80

Hand lay-up, spray lay-up

18

SMC, BMC

40

Plates and sheets

6

Filament winding

7

Pultrusion

3

RTM

3 95

Thermosets and Composites Table 2.34

Unsaturated polyesters: shares in % per process (estimations)

Miscellaneous

3

Neat and filled resins

20

Concrete, marble

11

Gelcoat, coating

4

Miscellaneous

5

The distribution of unsaturated polyester composites by market varies greatly according to the different sources (Table 2.35). Table 2.35

Unsaturated polyester composites: shares in % per market (estimations)

Building and civil engineering

18-46

Industry

13-14

Electrical engineering, consumer goods

19-31

Transport

10-37

Unsaturated polyesters are the mass-production thermoset used for: 9 Favourable ratio of cost versus mechanical and thermal properties. 9 Fatigue behaviour. 9 Aesthetics, including automotive class A aspect. 9 Durability, corrosion resistance with its limits. 9 Design freedom, possibility of selective reinforcement, manufacture of very large parts and big volumes. 9 Manufacturing versatility allowing realization at reasonable costs from prototype to automotive parts. 9 Low investment costs of manual processes (hand lay-up). 9 Repairing possibilities. 9 Lightness of the large parts involving the ease of handling, transport, installation, disassembly in the building and civil engineering industry, for example. 9 Reduced maintenance. 9 Electric, phonic and thermal insulation. 9 Translucence. 9 Resistance to the continuous contact of water. 2.7 2.2.2. Applications

Examples of operational or development parts are listed below. Automotive

9

96

Shelters, ambulance cells, trailer or special vehicle bodies in SMC or hand lay-up.

The plastics industry: economic overview

9 9 9 9

Engine covers and sumps in B M C or SMC. SMC roof and side spoilers for truck cabins. Truck front panels in standard or low density SMC. SMC cabin steps with integrated segments of wheel housing for Mercedes trucks. 9 SMC rear floors: one SMC part replaces 40 steel ones. 9 Repair putty in SMC for body panels. 9 Bodies of niche or medium output vehicles in RTM, B M C or SMC. 9 Decklids in SMC for the Mercedes-Benz Coupe. 9 Particle filter systems in SMC ( B M W 3 and 5 series). 9 Roofs or fenders of 4WD in SMC. 9 Inner doors. 9 Body panels, roofs, doors of monospaces (people movers) in SMC or R T M class A. 9 Body panels, doors, rear doors, bonnets in SMC (possibly foamed) or ZMC. 9 B M C tailgate of the Volvo V70. 9 Pickup truck boxes in SMC. 9 Front-ends for mass production vehicles in SMC: integration of 30 functions, 1500 parts per day. 9 Caps, trunk lids, bodies of US sports cars: class A aspect, lightness, more economical than steel or aluminium for series up to 45 000 vehicles. 9 Lighter parts for monospaces; covers, hoods, trunk lids for convertible cars in glass bead and glass fibre resins. 9 Roofs for vans; cabins, cabin doors for farm tractors: more economical than steel or aluminium for limited series. 9 Bodies of niche vehicles, leisure cars, motor homes or caravans, trucks; cells of ambulances assembled on a monospace basis. 9 Engine hoods, front fenders, front panels for trucks: aesthetics, mechanical properties, durability, vibration damping. 9 Interior panels of doors for vans: good ratio cost/mechanical properties, output of 700 parts per day. 9 Trunk floors of light vehicles, supports of batteries, roof deflectors for trucks. 9 B u m p e r beams of mass production vehicles. Unidirectional glass fibres ensure a maximum reinforcement. 9 Bumpers, side protection of mass production vehicles: good ratio cost/ aspect/mechanical properties, output of 2500 parts per day. 9 Engine covers: resistance to hot engine oils, series of 500 000 parts per annum. 9 Inlet pipes for light vehicles: good balance of mechanical properties and thermal behaviour. 97

Thermosets and Composites

9 9

Spring leafs for vans: good ratio weight/mechanical properties/fatigue behaviour. Headlight reflecting housing for automotive.

Building and civil engineering 9 Boarding for buildings: suitability for the small series, durability (20year-old specimens are still operational). 9 Sloping roofs of petrol stations, modular roofs of stadiums realized by elements: suitability for the small series. 9 Protection for industrial facilities, mobile guardrooms: suitability for the small series. 9 External walls in sandwich panels with glass fibre reinforced unsaturated polyester skins and PSE core for prefabricated houses, mobile guardrooms: lightness, insulation, suitability for small series. 9 Gables of dormer windows, pediments for building entrances: suitability for small series. 9 Roofs and stained glass for churches" a 40-year-old church in north France is still operational. 9 Moulds for concrete elements. 9 Balconies, parapets, cornices, colonnades, interior partitions for building restoration: suitability for small series. 9 Architectural panels in lightened composites. 9 Profiles for doors and windows for factories, houses, buildings. 9 Fire-doors in fireproofed unsaturated polyester. 9 Portals of gardens in panels screwed on metal structures. 9 Prefabricated balconies for buildings, possibly fireproofed. 9 Prefabricated floors of balconies for buildings in a sandwich of fireproofed polyester with foamed cores. 9 Translucent or opaque roofs in standard sheets with gelcoat on the two faces to protect glass fibres. 9 Skylights in simple or double wall sheets, shutters for factories in sheets with gelcoat on the two faces to protect glass fibres. 9 Housings of waterproofed lights: low water absorption, dimensional stability guaranteeing long-term sealing. 9 Industrial lighting cases 2.5 m long" dimensional stability. 9 Pedestrian bridge 120 m long by 2 m wide: mechanical properties, durability, ease of installation (lightness) and maintenance. 9 Bridge 40 m long by 3 m wide for pedestrians, snow clearance motor devices and equipment up to 5 tonnes: mechanical properties, durability, half the heaviness of steel, much more resistant to corrosion. 9 Element of road toboggan: mechanical properties, weather resistant and reasonable cost. 98

The plastics industry: economic overview

9 9

9 9

9 9 9 9 9 9 9 9 9 9

9 9 9 9 9 9 9 9 9 9 9 9 9

Panels for soundproofing walls easier to handle than traditional materials such as concrete. Bridge floor beams in self-extinguishing composite: these beams, laid on the primary structure of the bridge, are easy to set up and to dismount. Fireproofed panels and structures for oil rigs: weight saving. Panels, sandwich structures for protection of underwater oil wellheads in glass fibre reinforced polyester with PE foam core: impact resistance, controlled buoyancy, weight saving. External cabinets for automatic devices for traffic lights, telephone relays" suitability for small series. Cover plates of buried gas meters: mechanical resistance, the plate must support the passage of people, wheelbarrows, motorbikes, etc. Roofs in composite sheets screwed on metal structures for rural shelters such as bus stops: simplicity, durability, low cost. Footbridges for maintenance of subway tunnels in pultruded composite: reduction of maintenance. Main sewers for buildings. Gratings for traffic piers. Gutters for surface water along motorways. Pipes and fittings for industrial wastewater from the semiconductor, mining, paper pulp industries... Chimneys for factories up to 7 m in diameter. Rehabilitation of pipes without digging trenches by use of un-cured soft tubes: the sheaths introduced into the drain for rehabilitation are laid on the inner wall by water, vapour or compressed air and are hardened by hot water, vapour or UV. Blades up to 12.5 m long for wind turbines: mechanical properties, weather and fatigue resistances. Masts up to 18 m high for flags. BMC roof tiles are lighter and more aesthetic than clay and concrete ones. Balcony modules in SMC. SMC gratings. SMC gas metering cabinets. BMC exterior spotlight housings: no paint or rust. Telegraph pole supports in SMC. BMC sinks and counter tops for kitchens. Frames in pultruded glass fibre reinforced polyester. Piping up to 10 m in diameter by filament winding. Chemical or wine tanks up to 10 m in diameter by filament winding. Telephone posts centrifugally moulded in self-extinguishing glass fibre reinforced polyester. 99

Thermosets and Composites

9

Cable shelves for the Channel Tunnel, in fireproofed acrylic pultruded sections. 9 Formworks, cofferings. 9 Bonnets, bodies, housings for equipment protection (elevators, ventilators, fans). 9 Roofs and weatherboardings of agricultural or industrial buildings, sporting equipment, general-purpose rooms, and churches in glass fibre reinforced polyester sheets, possibly corrugated or ribbed.

Shipbuilding, water sports

9

9

9 9 9 9 9

9 9

Shipbuilding from boats up to minesweepers including all the types of race or pleasure boats, sailboards and surfboards, hulls of catamarans, hovercrafts, pilot boats, floating shopping-centres, dry-dock caissons, sluice gates. Fireproofed glass fibre reinforced polyester for offshore oil rigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors, gratings, handrails, duckboards, ladders. Swimming pools. Hulls of catamarans in a sandwich with a foamed core: good performances rigidity/weight/impact behaviour. Hulls of hovercrafts, pilot boats, floating shopping centre (112 m long): design freedom, durability, aesthetics, reduced maintenance. Dry-dock caissons: design freedom, durability, weight, reduced maintenance. Lock gates: 25-60 mm thick, reduction from 50 to 60% of the weight compared to steel, reduction of maintenance. The accessories are in stainless steel to harmonize the durability of the metal and the composite. Sailboards, canoes, fishing boats, mass distribution boats. Sailboards in sandwich with PSE core.

Electricity, electronics

9 9

9 9 9 9 9 9 100

Electricity meter housing, low-voltage fuse boxes, low and mediumvoltage boxes. Supports of terminals, connectors, switch parts, housing and handles or soles of domestic iron; handles and buttons of grills and pressurecookers; buttons. Dishes for satellite TV aerials, urban lampposts, cable shelves. Urban lamppost housings: reduction of maintenance compared to painted metal, insulation. Cable shelves in pultruded profiles. Supports of terminals. Connectors. Tubes for scanner (1 m diameter).

The plastics industry: economic overview

9 .

Hoodings and soles of domestic irons, handles of grills and pressurecookers. Frames and supports of solar panels.

Industry, anticorrosion

. . 9 .

Vinylester-based B M C for fuel cell plates. Formworks, hoods, bonnets, panels, housings, casings for machines. Pump housings in BMC. Gas washers, flue gas scrubbers, pipes and fittings for industrial sewage water, factory chimneys, chemical tanks, settling tanks. 9 Vinylester BMC: butterfly valves for water, acid and alkali solutions. 9 Compressed-air tanks for fighter pilots, bottles for compressed gas from 0.3 up to 4 1 in fibres wound on a metal liner: this ensures an excellent barrier effect. 9 Fuel tanks for railcars. 9 Storage or transport fuel tanks. . Storage or transport tanks for foodstuffs, drinking water, wine: the resins and gelcoats must be adapted to the products in contact. 9 Storage or transport tanks for chemicals: the resins and gelcoats must be adapted to the products in contact. , Tanks up to 100 m 3 for amino acids. , Containers for part transports for the nuclear industry, aeronautics: good balance properties/price. 9 Drainage pipes D I N 40 up to 2000: good balance cost/weight/ corrosion/mechanical properties. Furniture

9 Baths, basins, sanitary ware, tubs: good balance aesthetics/corrosion resistance/mechanical properties, suitability for small series. It is possible to incorporate a bacterial protection into the gelcoat. 9 False marbles, onyx for sanitary ware in unsaturated polyester with specific fillers: aesthetics, durability. . Cabins or sanitary blocks. 9 Cabins and doors of public toilets: the polyester is not always sufficiently resistant to vandalism and in such cases is replaced by stainless steel. 9 Translucent roofs. . Traffic signs in glass fibre reinforced polyesters attached on a metal frame. 9 Benches of bus shelters in glass fibre reinforced polyesters attached on steel frame. . Public benches in BMC. 9 Parisian newspaper kiosks. 101

Thermosets and Composites

9 9 9 9 9 9

Seats for communities in glass fibre reinforced polyester screwed on metal frames. Urban telephone shelters, roofs of phone boxes. Urban dustbins from 240 up to 360 litres: high performance price/ mechanical properties/weather resistance. Old paper containers. Housing for cash dispensers: suitability for small series. Urban notice boards, signposts for motorways.

Appliances 9 Structural elements, bodies, roofs and doors for display units, refrigerated window displays, refrigerated mobile shops, refrigerated lorries and semi-trailers, refrigerated vans and other vehicles, cold stores. 9 Housing and handles or soles of domestic irons, handles and buttons of grills and pressure-cookers. 9 Refrigerated boxes of semi-trailers, bodies, roofs, doors of refrigerated vehicles in sandwich panels with foamed cores: heat insulation and rigidity. The stainless steel inner wall makes cleaning and disinfection easier. Transport 9 SMC window frames for high-speed train. 9 SMC pillars of Berlin S-Bahn. 9 Bumpers, energy-absorbing fenders in SMC. 9 SMC luggage racks for trains. 9 Seat frames in GMT, R T M or BMC. 9 Reflectors. 9 High-speed train noses. 9 Careenages for race motorbikes. 9 Cabins, doors, floors of funicular in a sandwich with P V C foam core. 9 Individual shelves for train passengers. 9 Heating insulation sheaths for trains in a sandwich with foamed core, one skin in glass fibre reinforced polyester and the other skin in stainless steel. Miscellaneous 9 Vinylester-based B M C for fuel cell plates. 9 Concrete for moulding of statues (Nikki de St Phalle), knick-knacks and similar, blocks for sculpture, stained-glass windows, giant advertising articles, bodies and subjects for carrousels, play areas, leisure parks in glass bead or fibre reinforced resins. 9 Cinema, theatre or television decors, dismountable scenes" design freedom, aesthetics, lightness and aptitude to manufacture prototypes or few units. 102

'1he plastics industry: economic overview

9 9 9 9

9

9 9 9 9 9 9 9

9 9 9

Decorative objects in foamed resins. Bodies of bumper cars: mechanical properties, aesthetics, suitability for small productions. Advertising bottles of 13.5 m realized in 12 elements assembled on a light alloy structure. Figurines up to 35 m high, decors, giant toboggans, beams of medieval houses for leisure and theme parks: aptitude to manufacture prototypes or a few units, lightness. Cars, planes and so on for carrousels: good balance of weight/ mechanical properties/aesthetics/ suitability for small production runs. Cases for double bass. Swimming pools in foamed resins. Leg prosthesis, surgical corsets, reconstructing plasters for tortoise shells. Sandable cements for metal or composite repairs. Farm equipment, cabins of transformers. Terrace coating, buffing wheels, swimming pools. High-tech or aesthetical packaging such as containers for nuclear industry, aeronautics and radomes; cases for double bass. Halogen-free fire retardant SMC or BMC storage bins. Fishing rods. Buttons, scientific or electricity inclusions.

2.12.3 Phenolic resins 2.12.3.1. Consumption

Phenolic resin consumption by the industrialized countries accounts for 12-22% of the total thermoset consumption and is approximately 2-4% of all plastic consumption. The phenolic resins have slightly regressed in recent years. A lot of applications are out of the remit of this book, such as adhesives, resins for foundry, paints etc. The shares, in percentages by markets, differ according to the source. Table 2.36 shows some examples. The phenolic resins, for the activities covered by this book, are thermosets of medium-scale production used for: 9 A reasonable price and a favourable ratio of the cost versus the high thermal properties. 9 The possibility of excellent fire classifications that make them appreciated matrices for applications in public transport and public buildings. 9 The durability and corrosion resistance with its limits. 9 The manufacturing versatility allowing realization at reasonable cost from prototypes up to mass production. 103

Thermosets and Composites Table 2.36

Phenolic resins: shares in % per market (estimations)

Moulding

17

Electricity

8

Electric household appliances

4

Automotive

3

Miscellaneous

2

Laminates

32

Adhesives

8

Others

43

. The thermal insulation. o The electrical insulation under certain limits. 2.12.3.2. Applications

Examples of operational or development parts are listed below. Automotive and transport

9 Parts of water pumps, ashtrays, drive pulleys in mineral and glass fibre reinforced phenolic moulding powders. 9 Automotive electrical applications in wood flour reinforced phenolic moulding powders. 9 Body elements, noses for high-speed trains (Eurostar), body elements for subway in SMC. 9 Station and rolling stock equipment for subways and other public transports in glass fibre reinforced phenolic resin satisfying the fire and smoke regulations. 9 Control consoles for Eurostar trains, elements for subway partitions and interior panels, elements for fast passenger ships in SMC. 9 Partition panels for high-speed trains in glass fibre reinforced phenolic resins satisfying the fire and smoke regulations. 9 Fireproofed glass fibre reinforced phenolic resins for offshore oilrigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors. 9 2-1itre experimental engine in glass fibre reinforced phenolic resin (the moving parts and the combustion chambers are in metal). Electricity

9 Commutators, rings in mica reinforced phenolic moulding powders. 9 Coil housings, low-voltage engineering. 9 Cases, bases and lids of switches, bodies of coils, cases of meters, base plates in mineral and glass fibre reinforced phenolic moulding powders. 9 Lamp sockets in mineral reinforced phenolic moulding powders. 104

The plastics industry: economic overview

9 9 9 9

Cases of lamps, parts of switches, low tension electrical engineering. Cases of meters and base plates in wood flour filled moulding powders. Parts, boxes and lids of switches, bodies of coils in cellulose or textile fibre filled moulding powders. Thermostats, electricity meters.

Electric household appliances

9

9

Parts for domestic irons; handles and buttons of cookers; parts of switches; screw caps, handles and buttons of cookeries; parts of toasters in mineral reinforced moulding powders. Parts for domestic irons; handles and buttons for cookers, handles and buttons for cookeries and saucepans in wood flour filled moulding powders.

Building and civil engineering

9

9

Safety shelters and floors of oilrigs, domes of public buildings, fire doors, firebreak panels, fireproofed hoardings for buildings, fireproofed opaque roofs in standard size sheets, decorative laminates, coatings for the interior of dwellings in glass fibre SMC. Floors and partitions of buildings, fire doors, shelters in glass fibre foamed SMC.

Miscellaneous

9 9 9 9 9 9

Bearings, parts, axial joints, cases and base plates of machines and fittings. Cases of thermostats, parts of water pumps, drive pulleys in mineral and glass fibre reinforced moulding powders. Screw caps in mineral or wood flour filled moulding powders. Axial joints, parts of gas meter, bearings in graphite filled moulding powders. Steering wheels in cellulose or textile fibre reinforced moulding powders. Ablative materials, heat shields of space capsules in silica fibre reinforced composites.

2.12.4 Melamine and urea-formaldehyde resins (amino resins)

2.12.4.1. Consumption

The amino resin consumption by the industrialized countries accounts for 17-36% of the total thermoset consumption and is approximately 3-6% of the overall plastic consumption. A large number of applications, up to as much as 95 %, are out of the remit of this book. The shares for moulded parts, in percentages by markets, differ according to the sources. Table 2.37 shows some examples. 105

Thermosets and Composites

The amino resins, for the activities within the scope of this work, are thermosets of small production used for: 9 The electric insulation properties. 9 Aesthetics. 9 The attractive ratio of the cost versus the mechanical and electrical properties. 9 The food-contact approvals of certain melamine grades. 9 The chemical behaviour, in particular with detergents. 9 The fire classifications of numerous grades. 9 The thermal insulation. Table 2.37

Amino resin moulded parts: shares in % per market (estimations)

Electricity

67

Dishes

22

Caps and lids

4

Buttons

3

Ashtrays

2

Others

2

Total

100

2.12.4.2. Applications Examples of operational or development parts are listed below. Electricity 9 High and low voltage electrical engineering, switches, distributor boxes, meter cases, regulator cases, hoodings of small electric motors, fuse boxes in cellulose-filled melamines. 9 High and low voltage electrical engineering, switches, cases in glass fibre reinforced melamine. 9 Low voltage electrical engineering, switches, cases, distributor boxes in wood flour filled melamine. 9 Low voltage electrical engineering, switches, distributor boxes, meter cases, regulator cases, hoodings of small electric motors in cellulose filled phenolic modified melamines. 9 Low voltage electrical engineering, switches, distributor boxes, meter cases, regulator cases, hoodings of small electric motors, fuse boxes in wood flour filled phenolic modified melamines. 9 Low voltage electrical engineering, switches, distributor boxes, meter cases, regulator cases, hoodings of small electric motors, fuse boxes in cellulose filled unsaturated polyester modified melamines. 9 Low voltage sockets and plugs, switches, adaptors, junction boxes, dimmer switches in cellulose filled urea-formaldehyde. 106

The plastics industry: economic overview

Household appliances 9 Crockery, dishes, drinking glasses, tooth glasses, knives, forks, spoons, "unbreakable" plates and goblets, screw caps in food-contact grades of cellulose filled melamines. 9 Medical articles of beautiful aspect in cellulose filled melamines. 9 Non food-contact parts of beautiful aspect, for example, toilet flaps, in cellulose filled urea-formaldehyde. 9 Handles of domestic irons, control buttons, panhandles, buttons of pan lids, ashtrays in cellulose filled melamines or phenolic modified melamines or unsaturated polyester modified melamines. 9 Panhandles, buttons of pan lids in mineral filled melamines. 9 Base plates for small household appliances in cellulose filled ureaformaldehyde. Packaging 9 Decorative screwed plugs in cellulose filled urea-formaldehyde. Building 9 Decorative acoustic flagstones, suspended baffles in melamine foam. 9 Panels and partitions: melamine foam with plaster, fibreboard, plywood, plastic or metal doubling. 9 Soundproofing of roll-shutter boxes in melamine foam. Industry 9 Soundproofing of pumps, refrigerating units in melamine foam. 9 Insulation sleeves for vapour piping in melamine foam. Automotive and transport 9 Ashtrays in melamine. 9 Hood and transmission soundproofing in melamine foam. 9 Soundproofing laminate in melamine foam with aluminium foils, nonwoven or fabrics. Soundproofing o Self-extinguishing urea-formaldehyde foams if the country regulations authorize it. Among the applications that are outside the framework of this book but that represent a significant portion of the consumption, we can list: 9 Adhesives and binders for laminates containing paper or wood such as Formica, plywoods. Only the external faces are in melamine, which has a more beautiful aspect but is more expensive, whereas the inner mass is in urea-formaldehyde resin. For shipbuilding plywoods, melamine that is more resistant to moisture is used. 9 Melamines are also used as binders for foundry sands and abrasive powders for abrasive grinding stones and papers. 9 Melamines are used as varnishes for the IMC process (In Mould Coating) to decorate SMCs. 107

Thermosets and Composites

2.12.5 Epoxide resins

2.12.5.1. Consumption

The consumption of epoxide resins by the industrialized countries accounts for 4-6% of the total thermoset consumption and is approximately 0.70.8 % of the total plastic consumption. The growth in consumption roughly follows or slightly exceeds the growth rate of the overall plastic consumption. The resin shares, in percentages by markets, differ according to the sources. Table 2.38 quotes some examples. Table 2.38

Epoxide resins: shares in % per market (estimations)

Anticorrosive and protective coatings

50

Composites and reinforced resins for electricity

13

Flooring, concretes

8

Composites and reinforced resins for various uses

7

Adhesives

7

Tools for casting, moulding

6

Miscellaneous

9

Total

100

The epoxide resins, for the activities within the scope of this work, are thermosets of good or high performances with corresponding prices and limited production. The cost of manufacture is high for certain processes. The epoxies are appreciated for specific uses because of: 9 The mechanical properties at room and high temperature. 9 The fatigue behaviour. 9 The chemical resistance. 9 The electric insulation properties including at high temperature. 9 The flexibility of design and manufacture of the composites. 9 The [weight/mechanical properties] ratio. 9 The thermal insulation. 2.12.5.2. Applications

The applications are always technical. Examples of operational or development parts are listed below. Anti-corrosive, anti-wear, protection properties

9

Conduits, tubes for desulphurization installations: mechanical and thermal behaviour. 9 Support profiles and coatings for digester vats. 9 Flues up to 180 ~ 108

chemical,

The plastics industry: economic overview

9 9 9 9 9 9

9 9 9 9

Piping for chemical and oil industry, oil refinery pipelines: chemical, mechanical and thermal behaviour (up to 130 ~ low pressure loss. Tubes for the transport of matter in suspension: an inner gelcoat improves the abrasion resistance. Fire protection networks for oil rigs: balance of corrosion/mechanical properties/low pressure loss. Water piping for nuclear or thermal power stations: Balance of corrosion/mechanical properties/low pressure loss. Cooling pipes for frozen water. Long windable conduits for oil prospecting" These relatively flexible conduits can be wound up after processing and then unwound for installation without, or with very few, junctions. They are intended for the transport of anti-corrosive and anti-paraffin additives. Lining for rehabilitation of conduits without digging trenches. Proofing varnishes. Inner coatings for tanks, vats and other containers. Enamelling of household appliances; electrostatic powdering or fluidized bed coating.

Aeronautical, space, armaments

9 9 9 9

Arms of centrifugal machine for pilot training. External kerosene tanks for helicopters. Cryogenic tanks for rockets. Breakable cap of the Aster container. This cap is intended for the sealing of pressurized containers and launching tubes. It must be torn by the passage of the projectile. The part must stand up to external attacks, tear under a limited load without ejection of fragments, and be lightweight with small overall dimensions. The solution of draping carbon/epoxy prepregs was selected for the possibility to locally intercalate very different materials according to the functions required. o Flaps for supersonic civil transport aircrafts. 9 Transmission rods for civil aircrafts. 9 Drifts for civil transport aircrafts. 9 Wing structural elements for civil transport aircrafts. 9 Aeronautical careenages. 9 Plane wheels. 9 Propellers for military or civil transport aircrafts. 9 Carrying pylons of 500 kg for fighters. 9 Salmons for propeller blade tips: a nickel coating ensures the abrasion resistance. 9 Coatings of helicopter blades. 9 Tank travelling wheels: a glass fibre reinforced epoxy instead of metal leads to a lightening of 25 %. 109

Thermosets and Composites

9 9

9 9

9

Electronic cases of missile launchers" dimensional stability, lightness and mechanical properties. Carbon and Kevlar reinforced epoxy components for Helios, an unmanned aircraft that flies up to a 25 000 m altitude. Its 75 m wingspan is longer than that of a Boeing 747 airliner and it weighs 700 kg. High-strength carbon fibre reinforced epoxy for empennages and floor beams of the Boeing 777 since 1991. Rods for Airbus: since 1994, Aerospatiale has produced stress transmission rods that equip certain sections of the Airbus planes. Made in epoxy resin and carbon fibres, they bring a weight saving of roughly 30% compared to their equivalent in metal, for a comparable cost. They are produced by filament winding on a hardened sand mandrel. Electronic device boxes for shooting stations: the structure has a complex shape, must be light and rigid and supports numerous mechanical, optical and electronic devices. It is moulded by R T M with epoxy resin on deformable carbon fabric preforms and various glass/ epoxy or carbon/epoxy inserts. After machining thermoplastic parts and metal inserts are added.

Electricity, electronics

9 9

9 9

9 9 9 9 9 9 9 110

Parabolic aerial elements in a sandwich with a core of PVC foam: dimensional and surface accuracy, lightness, rigidity, maintainability. 15 m diameter parabolic antenna: the parabola consists of 176 sandwich panels selected for their rigidity, dimensional accuracy and lightness. High-voltage insulator tubes for power lines: good balance of electrical properties/weather behaviour/mechanical properties. Power semiconductor boxes, transformer rings, SF6 circuit breakers, coil supports, high-voltage insulators, fireproofed panels: service temperature up to 155 ~ Bending hoops for ferrosilicon sheets of transformers: mechanical and electrical properties. Overmoulding of coils. Simple, 2D or 3D printed circuit boards: electrical properties/heat behaviour/mechanical properties. Frames of solar panels. Encapsulation of L E D and other electric and electronic elements. Impregnation of electric and electronic devices as terminal plates, motors, transformers. Capacitor and other component coatings.

The plastics industry: economic overview

Automotive

9 9 9 9 9 9

9

9

Drive shafts of vans, heavy lorries, racing cars by filament winding. Sports car bodies, frame-hull for amphibious vehicles: flexibility of design and manufacture, ratio of mechanical properties/weight. Wishbone suspensions for rally cars. Laminated springs for utility, 4WD, cars, sports cars: reduction of weight of up to 50% compared to metal. Coupling for trailers or caravans (the ball is made of metal). Insulation of ignition systems for top-of-the-range cars: an epoxy resin is cast between the ignition system and an external aluminium cartridge. Experimental engine: only the connecting rods and the linings are in metal. The weight saving is significant with, in addition, a reduction of the noise and fuel consumption. F1 hulls in epoxy/carbon fibres.

Building, furniture

9

9

9 9 9 9 9

9

9 9

Reinforcement of existing concrete structures by carbon fibre reinforced epoxy laminates. The plates weigh 5 kg compared with 94 kg for steel. The additional cost (times 10) is acceptable only for repairs in harsh environments. Stiffener plates to increase the performances of existing buildings or works: the increase in the mechanical properties by a low volume and weight of carbon fibre reinforced epoxy prepregs makes it possible to increase the supported loads. Fireproofed panels" the skin risking an exposure to fire is aluminium; the other skin is glass fibre reinforced epoxy resin. Sandwich panels for building exteriors. Partition sandwich for building interiors. Frontages in sandwich panels for airports, hospitals" a decorative face offers various aspect possibilities. Repairs of metal offshore oil rig structures by plate stiffeners in carbon fibre reinforced epoxy: lightness, ease of manufacture and hardening at the ambient temperature on the site compensate for the high price. Renovation of conduits without digging trenches by use of un-cured soft tubes (socks): the sheaths introduced into the pipe to repair it are applied on the inner wall by water, vapour or air under pressure and are hardened by hot water, vapour or UV. Rods and cables for steadying of TV antennas: mechanical properties and weather behaviour. Cables for pre-stressed concrete: balance of mechanical properties and weather resistance, weight up to four times lighter than steel. 111

Thermosets and Composites

9 9

Refilling of concrete cracks with epoxy resins. Contemporary furniture" beds, tabletops, cupboards, bedside tables.

Sports, shipbuilding, water sports 9 Roofs and central hulls of race trimarans, 25 m race monohulls, sailboards and race boats. 9 Ballasts and ballasting pipes for ships; piping and water tanks for fire safety systems of oil rigs. 9 Suspension arm for high-tech bicycles. 9 Tent hoops and poles: lightness, mechanical properties. 9 3-ray wheels for race bicycles (the rim is in aluminium for braking). 9 Race boat hulls in sandwich composite: rigidity and mechanical properties. 9 Elements for submarines: acoustic transparency, vibration damping, reduced maintenance. Medical, health

Adhesives, possibly conductive or transparent. Pacemaker coatings. Dental prostheses. Artificial teeth for dentists' training. Vascular system naturalization of the kidneys by resin injection. Spectacles frames. Tools

9 9 9 9 9

Moulds for hand lay-up moulding of glass fibre reinforced unsaturated polyester: more economic than metal, but with a more limited lifetime. Resin concretes. Sealing. Machine frames, base plates. Epoxy syntactic paste for rapid tooling system (Vantico/Boeing process). Fixings.

Glues and adhesives

9 9

Industrial adhesives, possibly conductive or transparent. Medical adhesives: biocompatible and sterilizable bicomponents.

Miscellaneous

9 9 9 9 112

0.5 to 1000 litre tanks for LPG, compressed air: inner sealing liner in metal. Cable cars and arms for cable transport in panels with honeycomb core: 42% weight savings. Surrounding joint of honeycomb structure in epoxy paste. Sculptures by Delfino and other sculptors.

The plastics industry: economic overview

2.12.6 Polyimides 2.12.6.1. Consumption

The consumption of polyimides by the industrialized countries is not listed in the economic statistics. It is estimated that the consumption growth rate slightly exceeds the rate for plastic consumption overall. The polyimides, for the activities covered in this book, are thermosets of very high performances with correspondingly high prices and processing costs and, consequently limited production. They are appreciated for very specific uses because of: 9 High retention of the mechanical properties across a broad range of temperatures, from-200 ~ up to +300 ~ and more for short periods. 9 The high thermal stability in long-term service allowing use up to 260 ~ in continuous service and 480 ~ for very short periods. 9 The interesting tribological properties: low friction coefficient and wear. 9 Stability of the electric insulation properties with temperature, except resistance to tracking. 9 The chemical resistance to numerous chemicals with, however, some limitations. 9 The resistance to high-energy radiations. 9 The limited vacuum degassing after drying. 9 The fatigue behaviour. 9 The fire-resistant grades. 2.12.6.2. Applications

The applications are always high-tech. The price and the difficulty of transformation limit the use of polyimides to well-targeted applications taking advantage of the high performances of these materials. Some examples of operational or development parts are listed below. Aeronautical and space

9

Bearings in self-lubricating polyimide to replace bronze, which wears out too quickly. The service life is multiplied by 15. Moreover, the expansion capacity makes it possible to replace the bearings by slipping them in place in 15 minutes instead of four hours. 9 Grooved couplings in self-lubricating polyimide for the drive of generators, hydraulic pumps and other equipment on military aircraft: the wear resistance is 50 times higher than for the lubricated traditional couplings and greasing is unnecessary. 9 Jet engine cones: a polyimide is selected for its high-temperature behaviour. 9 Hydraulic fluid tanks for jet engines: the selected carbon reinforced bismaleimide resin is 180 ~ long-term resistant. 113

Thermosets and Composites

9

Stiffeners of acoustical panels: the polyimide is chosen for its adaptability to the space environment. 9 Protection hoods: a reinforced polyimide is chosen for its mechanical and thermal properties. 9 Honeycombs in polyimide sheet structures (Nomex) for structural sandwich composites found in aircraft parts such as tail-fins, engine nacelles and helicopter blades. 9 Parts intended to function in a space vacuum, thermal and mechanical protection for aeronautics. 9 Empennages: these structural parts are subjected to high stresses and high temperatures because of the hypersonic flying conditions: aerodynamic loading, vibrations, kinetic heating. Temperatures are in the range of 130 ~ to 600 ~ according to the location. They are moulded by RTM with a resin bismaleimide of high thermal and mechanical performances reinforced with carbon fabrics and braids. 9 Spacers for engine acoustical panels. . Supports for satellite antennae. 9 Soundproofing and thermal insulation of missiles, planes and helicopters in polyimide foam. 9 Protection for equipment used on space shuttles in polyimide foam. 9 Cryogenic protection on satellites in polyimide foam. 9 Insulation of piping in polyimide foam. Automotive

9

Self-lubricated discs for windscreen wipers replacing lubricated ball bearings: the lubrication system is unnecessary, the assembly is simplified and can be automated; performances are improved. . Synchronization rings of heavy lorry gearboxes. 9 Base plates of cigar-lighters. . Bases of car lamps. 9 Heat shields in polyimide sheet structures (Nomex). 9 Insulation shields for spark plug leads in Nomex.

Office automation

9

Plate bearings for printers: reduced greasing, better wear resistance, reduction of the maintenance operations. . Cable guides for printer heads. The polyimide replaces ceramics, ruby or polyacetal. The tungsten wire passages are moulded. The estimated lifespan is 250 million characters against 100 million for polyacetal, leading to high cost savings in maintenance and reduction of the period of inactivity. 9 Parts for photocopiers, bearings, sockets... . Paper/print drum separation arms, and drive wheels for photocopiers. 9 Drive rollers. 9 Sliding parts, guiding rollers for high-speed printers and photocopiers.

114

The plastics industry: economic overview

Electricity 9 ,, 9 9 9 9 9 9 . , 9 . . 9 9 9 9 9

Insulating elements and spacers for electron accelerators. O v e r m o u l d of H classified m o t o r collectors. Printed circuit boards usable up to 300 ~ Bodies of generator coils. Terminal plates and terminals. Overmoulding of coils. Insulating collars for chain saws. L a m p bases. Coil frames. Connectors. Insulation of rotor axes. Parts of circuit breakers. Air vents for slide projectors. Drive wheels for microwave ovens. Handles for electric ovens and other household appliances. Parts for spit-roasters. Insulating elements and crossings for electric blowtorches. Insulating elements and spacers for cathode-ray tubes.

Industry 9 9 9

,,

, 9 , . ,, 9 9 9 9 9 .

H o n e y c o m b s in polyimide sheet structures (Nomex) for structural sandwich composites. Paper in polyimide for fire-resistant uses. Brakes on textile winding-machine: these friction elements stop the reels revolving at 1 0 0 0 0 r e v o l u t i o n s / m i n u t e in 15 seconds. The lifespan is doubled c o m p a r e d to the previously used steel with a 3050% reduction in cost. The m a i n t e n a n c e expenses are decreased. Piston rings of ethylene compressors. The lifespan is four times longer than for the laminated phenolic resin segments used previously, decreasing stoppages and m a i n t e n a n c e costs. Dry bearings in self-lubricated polyimide. Sliding plates in self-lubricated polyimide. Pump pads. Joint seatings. Guiding rollers of grinder bands. Manipulator inserts for glass bottle demoulding. Racks and handling cases for printed circuit b o a r d treatments. Cryogenic insulation in polyimide foams. Gears of variable speed transmissions. Self-lubricated guides for cast solid films replacing a roller in machined aluminium. Sealing disc of valve in an industrial F r e o n compressor. The t e m p e r a t u r e is 175 ~ and the frequency is 1750 cycles/minute. 115

Thermosets and Composites

9

9 9 9

Self-lubricating polyimide rings on polyamide casings: reduction of the friction and wear. Segments of air compressors. Toothed wheels. Seats of valves, piston rings for hydraulic installations for the chemical industry.

Vacuum technology

9

9 9

Sealing for high-vacuum installations usable up to 300 ~ without lubrication. The polyimides are more resistant, lighter and more economical than metal joints. Parts intended for high-vacuum service. Joints and linings for vacuum pumps.

Miscellaneous

9 9 9

Non-flammable scenery, coloured filter holders for studio and theatre spotlights, fire-resistant wallpaper in or including Nomex paper. Voice coil insulation for stereo loudspeakers including Nomex paper. Disposable cookware in Nomex paper.

2.12.7 Silicones 2.12.7. 1. Consumption

The silicone consumption by industrialized countries is not listed in the economic statistics and the figures differ widely according to different sources. Consumption is estimated to be of the order of 1% or 2% of the total plastic consumption and its progression exceeds the rate for plastics consumption overall. A great number of applications, up to 85%, are outside the remit of this book. The main producers are the USA, E U and Japan. Table 2.39 quotes some examples of consumption shares according to end use. Table 2.39

Silicones: shares in % per end use (estimations)

Elastomers & resins

15-45

Oils for anti-adhesion, non-stick surfaces, antifoaming, cosmetics...

55-85

Total

100

Table 2.40 quotes some examples of consumption shares per market. Five large industrial sectors consume 75 % of silicones. Table 2.40

Silicones: shares in % per market (estimations)

Distribution of the demandfor silicones in Europe 116

% du total

The plastics industry: economic overview

Table 2.40

Silicones: shares in % per market (estimations)

Building and civil engineering

18

Electricity and electronics

15

Mechanics

15

Chemical industry

14

Automobile

13

Medical

7

Aeronautics

5

Computers

3

Miscellaneous Total

10 100

Silicones, for the activities with which this work is concerned, are thermosets of high thermal performance and elastomers of high elastic behaviour. They are appreciated for specific uses because of: 9 The elasticity and the low compression set at high temperatures for the elastomers. 9 The flexibility and softness even at low temperatures for the elastomers. 9 The high retention of the physical and mechanical properties in a broad range of operating t e m p e r a t u r e s , - 5 0 ~ t o - 1 1 0 ~ and +150 ~ to 260 ~ in long-term service and more (350 ~ for short periods. 9 The weathering and resistance to UV, ozone, Corona effect. 9 The chemical resistance to numerous chemicals, with some limitations. The fluorinated grades provide good resistance to hydrocarbons and some solvents. 9 The anti-adhesive and non-stick properties. 9 The physiological inertness. 9 The excellent electric insulation properties. 9 The versatility of the processing methods including manual ones with very few investments for prototypes or industrial applications. 9 The fair [cost/performance] ratio. 2.12.7.2. Applications

The applications are always specific. The price and special properties limit the use of silicones to specific applications taking advantage of their unique performances. Some examples of operational or development parts are listed below. 117

Thermosets and Composites

Building and civil engineering 9 Sealing cements. 9 Safety cable sheathing for buildings or p o w e r stations. 9 Seals, joints for glazing. 9 A r c h i t e c t u r a l coated fabrics for roofs. Electricity, electronics, optoelectronics 9 Joints and cables for external projectors, street lightings. 9 Solar panel seals. 9 M e d i u m and high-voltage insulation: insulators and cables 9 S e m i c o n d u c t o r s encapsulation. 9 T r a n s l u c e n t coatings for electricity and electronics. 9 Flexible moulds for electricity and electronics c o m p o n e n t s . 9 Potting of electronic c o m p o n e n t s . 9 H e a t dissipation coatings or encapsulations for electronics. 9 Filling of modules, charts, circuits, components.., for electronics, computers, electricity, aeronautics, space, appliances, automotive. 9 Cables for drying ovens, convectors. 9 Cables for n e o n signs. 9 Casting syntactic foams for electronics. 9 Optical fibre sheaths. 9 Keypads. Electric household appliances

9 9 9 9 9 9 9

Cast seals for ceramic hobs, ovens. Sealing adhesives for domestic iron connections. Seals for dishwashers. Cables for t u m b l e dryers, convectors. A n o d e caps for television sets. Bellows for drink dispensers. Tubes for coffee machines.

Mechanical industry 9 Seals cast in situ. 9 H i g h - t e m p e r a t u r e seals. 9 Cables for chemical plants. 9 Cast m o u l d i n g parts in small series and prototypes. 9 Shock and vibration absorbers. 9 Tight and flexible joints. 9 Binders of refractory fillers for the m a n u f a c t u r e of ablative materials. 9 Roller covering for handling of hot products such as coating machines. 9 Soft covering for wheels of packing machines. 9 H o t air sheaths. 9 Wire coatings for control circuits. 118

The plastics industry: economic overview

9 9

Bellows, diaphragms. Flexible keyboards for machine control panels.

Tools for moulding, casting

9 9 9 9 9 9 9 9 9 9

Moulds for plaster, stucco, reconstituted stone, c e m e n t and concrete mouldings. Moulds for decorative elements as such statuettes, furniture parts. Moulds for costume jewellery in low melting point alloys. Moulds for foundry waxes. Moulds for automotive instrument panels, shoes, imitation leathers in plastisols and polyurethanes. Moulds for ultra-high frequency moulding of PVC. Moulds for epoxies and u n s a t u r a t e d polyester laminates. Tools for prototypes and vacuum casting. Matrices or plungers for t h e r m o f o r m i n g of ABS, polystyrene, PVC. Cores for composite moulding by isostatic compression.

Medical, health, food appliances 9 Valves for cephalic liquid. 9 D u m m i e s , nipples. 9 Oxygen masks. 9 Catheters. 9 Body electrodes. 9 Tubes for transfusion. 9 Caps and piston for syringes. 9 Artificial ventricles. 9 E l e m e n t s for pacemakers. 9 Plastic surgery. 9 Balls for valves. 9 Pharmaceutical stoppers. 9 Anaesthesia tubing. 9 X-ray-opaque shunts. 9 Nozzles, masks, tubes for respiratory systems. 9 Dialyser seals. 9 Oxygen sheaths. 9 Contact lenses. 9 Prostheses. 9 Food-dispensing valves. Aeronautics 9 High t e m p e r a t u r e seals. 9 Connectors. 9 Shock and vibration absorbers. 9 External seals for windows, inspection hatches, doors. 9 Safety cables for aircraft. 119

Thermosets and Composites

Art, decoration

9 9 9 9

Moulds for plaster, stucco, reconstituted stone, cement and concrete mouldings. Moulds for decorative elements such as statuettes, furniture parts. Moulds for costume jewellery in low melting point alloys. Moulding of imprints, impressions.

Automotive and transport

9 9 9 9 9 9 9 9 9 9 9 9

Cables for vehicles" lighting, heating, de-icing. Caps for automotive ignition systems. Seals for engines. Radiator seals. Heavy lorry coolant hoses guaranteed for 1 million km. Expansion elements for oil leakage detectors. Cylinder head gasket. Ignition cables. Spark plug boots. Silicone-coated fabrics for airbags. Seals for train windows. Safety cables for trains, subways.

Office automation

9 9 9

Soft roller coverings for photocopiers, faxes, thermal printers. Wires for computers. Flexible keyboards for telephones, computers.

2.12.8 Polycyanates or cyanate esters 2.12.8. 1. Consumption

The consumption of cyanates in industrialized countries is very low and is not listed in the economic statistics. Cyanates are very high performance thermosets used as matrices for high-tech composites in the space and electricity industries. They are appreciated for very specific uses because of: 9 The possibility to use them at temperatures as low a s - 2 1 0 ~ 9 The high thermal stability in long-term service allowing their use from 176 ~ to 260 ~ in continuous service and more for very short periods. 9 The interesting electric properties. 9 The toughened grades. 9 The low moisture absorption. 9 The fatigue behaviour. 9 The fire-resistant grades. 9 The easier processing than polyimides. 120

The plastics industry: economic overview

9 The possibility of RTM and compression moulding. 9 The radiation resistance. 9 The low outgassing. 2.12.8.2. Applications

The applications are always very specific. The price limits the use of the cyanates to well-targeted applications taking advantage of their highly specific performances. Some examples of operational or development parts are listed below. Aeronautics

9 9 9

Structural elements for satellites. Structural elements for airframes and fuselages of aircrafts. Structures and flywheel systems for space in high level (80% volume fraction) carbon fibre reinforced polycyanates: cylinders are moulded by filament winding in sizes up to 25 mm wall thickness and 600 mm in diameter.

Electricity, electronics

9

Structural elements for electromagnetic devices.

radomes

and

other

dielectric

and

2.12.9 DCPD 2.12.9. 1. Consumption

The DCPD consumption by industrialized countries is not listed in the economic statistics. It is an emerging thermoset competing with polyurethanes. The DCPDs are general-purpose thermosets appreciated because of: 9 The fast cycles in RIM processing. 9 The possibility to manufacture big parts. 9 The possibility to produce small series. 9 The fair mechanical properties and the good ratio performance/ weight. 9 The impact behaviour up t o - 4 0 ~ 9 Aesthetics. 2.12.9.2. Applications

Some examples of operational or development parts are listed below. Automotive and transport

9 Fenders, roofs, sliding sunroofs, spoilers, bumper skirts for niche or medium output light vehicles or trucks. 9 After-market parts such as running boards for vans with moulded-in footstep. 121

Thermosets and Composites

Anti-corrosion 9

Sewage containment vessels.

9 9

Industrial drainage troughs. Cell covers.

Agricultural, garden and earth-moving equipment 9 9 9

Excavator housings. Tractor fenders for rear-wheels. Housings, engine hoods, grass baskets for lawnmowers.

Packaging 9 9 9 9

Custom pallets and containers. Protective over-packaging of drums and other containers. Structural packaging for car engines. Protection overmoulding.

Industry 9 Hoods, panels, casings for machines, cases of humidifiers, cases of control monitors. 9 E l e m e n t s for electrolysis cells. Shipbuilding 9 Boat interior elements. Sport and leisure 9

O o l f c a r t bodies.

2.12.10 Furane resins 2.12.10.1. Consumption The furane resin consumption by industrialized countries is not listed in the economic statistics. It is traditionally used as a binder for chemical-resistant cements and concretes. Some applications have developed in chemicalresistant laminates. Furane resins are special thermosets appreciated because of: 9 The high chemical resistance in non-oxidizing environments. 9 The t h e r m a l stability in long-term service allowing their use up to 150 ~ 9 The fire-resistant grades with a low smoke emission. 2.12.10.2. Applications For the activities of interest in this work, all the applications concern chemical resistance" 9 Cements and concretes. 9 Vessels for the chemical industry. 122

The plastics industry: economic overview

2.13 Application examples of the main reinforcements 2.13.1 Glass fibres 2.13.1.1. Consumption

Olass fibres account for an estimated 95% of the total fibre consumption

for polymer reinforcement. Glass fibres, for the activities within the scope of this work, are the most popular reinforcement, appreciated for numerous uses because of: 9 The excellent performance/cost ratio. 9 The high thermal resistance. 9 The insulating properties. 9 The relatively high elastic modulus of the order of 50-90 GPa, much higher than that of polymers, but lower than that of carbon fibre. 9 The low coefficient of thermal expansion. 2.13.1.2. Applications

Some examples of operational or development parts are listed below. Automotive and transport

9 Thermoplastic skin over a glass SMC frame for the tailgate of the Mercedes-Benz Class A. 9 For lighting, the metal reflectors that rusted have been total replaced by plastics and glass reinforced composites. 9 Door handles in glass reinforced composites. 9 Bumpers, glass reinforced composite inserts for energy-absorbing bumpers. 9 Frames of amphibious cars in epoxy/glass/carbon/Kevlar. 9 Cabins of heavy lorries in glass and Kevlar fibre reinforced composites. 9 Monocoque frames of special vehicles in glass reinforced composites. 9 Various crossbars (driving support, transmission, etc.), door reinforcements, leaf springs, commercial vehicle floors, trunks, luggage boxes, battery trays in glass reinforced composites. 9 Housing of rear view mirrors, back ventilation grids, front-ends (part integrating the grill and the headlight frame) in glass reinforced composites. 9 Doors in glass reinforced composites or hybrid materials. 9 Engine hoods, trunk lids, hatchbacks, tailgates in glass reinforced composites. 9 Frames of front and back seats, seat slides, instrument panels, consoles, package trays, parcel shelves and trays, glove compartments in glass reinforced thermoset composites or GMT. 123

Thermosets and Composites

9 9 9

9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 124

Glass reinforced thermoplastic composites for the body vertical panels of the Saturn by General Motors (1000 vehicles per day). Glass reinforced thermoplastic composites for the fenders of the Class A by Mercedes-Benz, the Scenic and Laguna by Renault. Front-ends of the Mini Cooper in long glass fibre reinforced polypropylene (Stamax). Front-ends in long glass fibre reinforced polypropylene (Compel). Instrument panel substrates in long fibre reinforced thermoplastic (Verton). Steering housing in long glass fibre reinforced polypropylene (Celstran). Proton battery trays in long glass fibre reinforced thermoplastic (Verton). Pedal supports of the Peugeot 405 in GMT. Hatchback doors, noise shields in GMT. GMT protection sheets beneath the engine. Front-ends in GMT. Bumper beams in GMT. Energy-absorbing bumpers, fenders in SMC. Seat frames in GMT, RTM or BMC. Shelters, ambulance cells, trailer or special vehicle bodies in glass fibre reinforced polyester, SMC or hand lay-up. Engine covers and sumps in BMC. SMC roofs and side spoilers for truck cabins. Truck front panels in standard or low density SMC. SMC cabin steps with integrated segment of wheel housing for Mercedes trucks. SMC rear floors: one SMC part replaces 40 steel ones. Repair putty in SMC for body panels. Bodies of niche or medium output vehicles in glass fibre reinforced polyester composites (RTM, BMC or SMC). Decklids in SMC for the Mercedes Coupe. Particle filter systems in SMC (BMW 3 and 5 series). Roofs or fenders of 4WD in glass fibre reinforced polyester composites, SMC. Body panels, doors, rear doors, bonnets in SMC (possibly foamed) or ZMC. BMC tailgate of the Volvo V70. Pickup truck boxes in SMC. Oil sumps in SMC. Inner doors in glass fibre reinforced polyester composites.

The plastics industry: economic overview

Building, civil engineering 9 Cornices, ornamental mouldings, sculptures in composites for hotels, casinos and buildings. 9 Tiles of 30 cm by 1.2 m in GMT. 9 BMC roof tiles, lighter and more aesthetical than clay and concrete ones. 9 Balcony modules in SMC. 9 Moulds in R T M for ceiling elements moulded in concrete. 9 SMC water gratings. 9 SMC gas metering cabinets. 9 BMC exterior spotlight housing: no paint or rust. 9 BMC sinks and counter tops for kitchens. 9 Frames in pultruded glass fibre reinforced polyester. 9 Industrial chimneys in glass fibre reinforced polyester. 9 Piping in glass fibre reinforced polyester up to 10 m in diameter by filament winding. 9 Chemical or wine tanks in glass fibre reinforced polyester up to 10 m in diameter by filament winding. 9 Telephone posts centrifugally moulded in self-extinguishing glass fibre reinforced polyester. 9 Telegraph pole supports in glass fibre reinforced polyester (SMC). 9 Cable shelves for the Channel Tunnel, in fireproofed acrylic pultruded sections. 9 Formwork, coffering in glass fibre reinforced polyester. 9 Bonnets, bodies, housings for equipment protection (elevators, ventilators, fans) in glass fibre reinforced polyester. 9 Roofs and weatherboardings of agricultural or industrial buildings, sports equipments, general-purpose rooms, and churches in glass fibre reinforced polyester sheets, possibly corrugated or ribbed. 9 Sluice gates in glass reinforced composites. 9 Desulphurization chimneys in glass reinforced vinylester and epoxy. 9 All-purpose bridge in glass reinforced plastics. 9 Gratings, duckboards in pultruded profiles for beaches and piers allowing the circulation of trucks. 9 Windows in pultruded glass reinforced profiles in the U S A and Canada. 9 Pillars and beams in pultruded glass reinforced tubes filled with concrete. 9 Pedestrian bridge (120 m long) in pultruded composites of continuous glass fibre mat reinforced polyester. 9 Cable shelves in glass reinforced pultruded profiles. 9 Handrails for building site in glass reinforced pultruded profiles. 9 Gratings, duckboards made with glass reinforced pultruded profiles. 125

Thermosets and Composites

9

Sloping roofs of petrol stations in pultruded 40% glass fibre reinforced polyester profiles.

Mechanics, industry

9 9

9 9 9 9 9 9 9 9 9 9

Pump housing in BMC. High-pressure gas cylinders made of glass reinforced composite. GRP pipes and fittings for industrial waste water, inner lining for pipe rehabilitation without trenching. GRP tanks for chemicals, settling basins. GRP tanks for LPG, 0.5-1000 litres compressed air tanks. Glass reinforced composite moulds for polyester parts moulded by the hand lay-up process. Synthetic polymer concretes, and fixings made of GRP. Base plates in GRP. Industrial paddle fans in long fibre reinforced thermoplastic (Verton). Formworks, hoods, bonnets, panels, housings, casings for machines in glass fibre reinforced polyester. Gas washers, flue gas scrubbers, pipes and fittings for industrial sewage water, factory chimneys, chemical tanks, settling tanks in GRP. Butterfly valves for water, acid and alkali solutions in vinylester BMC.

Furniture

9 9

9 9 9 9 9 o

Cabins or sanitary blocks in glass fibre reinforced polyester or cellulose fibre reinforced phenolic resin and melamine gelcoat. Cabins and doors of public toilets: the glass reinforced polyester is not always sufficiently resistant to vandalism and in such cases is replaced by stainless steel. Translucent roofs in glass fibre reinforced polyesters. Traffic signs in glass fibre reinforced polyesters attached on metal frames. Benches of bus shelters in glass fibre reinforced polyesters attached on steel frames. Public benches in BMC. Parisian newspaper kiosks in glass fibre reinforced polyesters since 1982. Seats for communities in glass fibre reinforced polyester screwed on metal frames.

Miscellaneous

9 Fuel cell plates in vinylester-based BMC. 9 Convertible wheelchairs in glass fibre reinforced thermoplastic (Tepex). 9 Glass reinforced sandable cements for metal or composite repairs. 9 Farm equipment, cabins of transformers, seat cockles, buffing wheels, careenages for race motorbikes in GRP. 126

The plastics industry: economic overview

9 9 9 9

9

9 9

Swimming pools in glass reinforced composites. Leg prosthesis, surgical corset, reconstructing plaster for tortoise shell in GRP. Giant advertising articles, bodies and subjects for carrousels, play areas, leisure parks; theatre, cinema, and TV decors in GRP. Structural elements, bodies, roofs and doors for display units, refrigerated window displays, refrigerated mobile shops, refrigerated lorries and semi trailers, refrigerated vans and other vehicles, cold stores in GRP. High-tech or aesthetical packaging such as containers for the nuclear industry, aeronautics, and radomes, cases for double bass in GRP. Halogen-free fire retardant SMC or BMC storage bins. Fishing rods in GRP.

Electricity, electronics 9 Parabolic aerial elements, power semiconductor boxes, high-voltage insulating tubes for power lines, high-voltage insulators in GRP. 9 Fireproofed panels in GRP. 9 Printed circuit boards in GRP. 9 Outdoor electronic casings in glass reinforced thermoplastic (Tepex). 9 Electricity meter housings in GRP. 9 Low-voltage fuse boxes, low and medium-voltage boxes in GRP. 9 Supports of terminals, connectors, switch parts in GRP. 9 Housing and handles or soles of domestic irons, handles and buttons of grills and pressure-cookers, buttons in GRP. 9 Dishes for satellite TV aerials in GRP. 9 Urban lampposts in GRP. 9 Cable shelves in GRP. 9 Frames and supports of solar panels in GRP. Shipbuilding

9

9 9 9

9

Shipbuilding from boats up to minesweepers including all the types of race or pleasure boats, sailboards and surfboards; hulls of catamarans, hovercrafts, pilot boats, floating shopping-centres in GRP. Dry-dock caissons, sluice gates in GRP. Masts and booms of yachts in GRP. Fireproofed glass fibre reinforced polyester for offshore oil rigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors, gratings, handrails, duckboards, ladders. Fireproofed glass fibre reinforced phenolic resins for offshore oil rigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors.

Transport 9 SMC window frames for high-speed trains. 127

Thermosets and Composites

9 9 9

SMC pillars of Berlin S-Bahn. SMC luggage racks for trains. Glass reinforced composites for various coach parts of high-speed trains weighing 23 % of the total mass. 9 Station and rolling stock equipment for subways and other public transport in glass fibre reinforced phenolic resin satisfying fire and smoke regulations. 9 Reflectors in glass fibre reinforced polyester. 9 High-speed train noses in glass fibre reinforced polyester. 9 Partition panels for high-speed trains in glass fibre reinforced phenolic resin satisfying fire and smoke regulations. Aeronautics, armaments

9 9

Blades of helicopter tail rotors in glass and carbon reinforced epoxy. Tubular bangalore torpedoes for mine clearing, mine detecting probes in thermoplastic prepregs (Towflex). 9 Camouflage supporting structures, telescopic cable rod sets, lattice masts and other lightweight structures in thermoplastic prepregs (Towflex). 9 Tank travelling wheels: a glass fibre reinforced epoxy instead of metal leads to a lightening of 25 %. 9 High-pressure gas cylinders for oxygen storage: Aerospatiale Missiles markets such parts with a 0.3-4 litres capacity for 210-325 bars operating pressures. Initially, these parts were intended for nitrogen storage and were manufactured from aluminium inner liners without welds on which a composite glass/epoxy was wound. The storage volume compared to the mass of the bottle ranges from 200 to 300 1/ kg. Currently, cylinders with thin stainless steel inner liners are produced for oxygen storage used by fighter pilots. Stored volumes reach 400 1/kg. 9 Structural parts for radomes and other electromagnetic and dielectric applications in glass reinforced polycyanate composites. 2.13.2 Aramid fibres 2.13.2.1. Consumption

The consumption of aramid fibres for polymer reinforcement is estimated at less than 5 % of the total. The aramid fibres, for the activities within the scope of this work, are appreciated for specific uses because of: 9 The higher reinforcement than glass fibres with 10% weight saving. 9 The balance of performance/weight/cost. 9 The better impact behaviour than carbon fibre. 9 The insulating properties. 128

The plastics industry: economic overview

2.13.2.2. Applications

Some examples of operational or development parts are listed below. 9 Frames of amphibious cars in epoxy/glass/carbon/Kevlar. 9 Ductile ballistic materials in aramid fibre reinforced composites, which absorb the projectile energy while stretching. 9 Coffee tables with plates in Kevlar reinforced composites attached on a metal frame. 9 High-pressure gas cylinders for space use: filled with helium under several hundred bars, they are used in the propulsion systems of space vehicles and launchers. To gain a 30% to 50% mass reduction compared to metal cylinders, while optimizing the costs, Aerospatiale uses a thin metal inner liner for the sealing. This is used as the mandrel to manufacture the structural envelope by filament winding of Kevlar or carbon fibres which ensures mechanical resistance. The carbon fibres make it possible to save 10% in mass compared to Kevlar. For an operating pressure of 400 bars, the capacities are of 300 1. 9 Kevlar and carbon reinforced epoxy components for Helios, an unmanned aircraft that flies up to a 25 000 m altitude. Its 75 m wingspan is longer than that of a Boeing 747 airliner and it weighs not more than 700 kg. 9 Cabins of heavy lorries in glass and Kevlar fibre reinforced composites. 9 Satellite antenna reflectors: these reflectors are made of sandwich hulls carbon/aluminium honeycomb or Kevlar fibre/ Kevlar honeycomb. 9 Cable cars in epoxy/Kevlar/honeycomb (Nomex). 2.13.3 Carbon fibres 2.13.3.1. Consumption

Carbon fibre consumption for polymer reinforcement is estimated at less than 5 % of the total for all fibres. C a r b o n fibres, for the activities within the scope of this work, are appreciated for specific uses because of their: 9 High mechanical performances. 9 Fatigue behaviour. 9 High dielectric and thermal conductivity. 9 Lower density than glass fibres. 9 Low coefficient of friction. 9 Low coefficient of thermal expansion. 2.13.3.2. Applications

Some examples of operational or development parts are listed below. 129

Thermosets and Composites

Aeronautics, space, armaments

9 9 9

9

9

9

9

9

9

130

Blades of helicopter tail rotors in glass and carbon reinforced epoxy. Inboard lower access panels in carbon fibre reinforced PPS. Fuselage panels: Aerospatiale is developing a fuselage panel (1.6 m by 2 m) in carbon fibre reinforced PEEK. This thermoplastic composite is made of a skin reinforced locally in the window zone. A metallized latticework is integrated on the external face for protection against lightning and the other dielectric discharges. Empennages: these structural parts are subjected to high stresses and elevated temperatures because of the hypersonic flying conditions: aerodynamic loading, vibrations, kinetic heating. Temperatures are in the range of 130-600 ~ according to the location. They are moulded by RTM with a resin bismaleimide of high thermal and mechanical performances reinforced with carbon fabrics and braids. Electronic device boxes for shooting stations: the structure has a complex shape, must be light and rigid and supports numerous mechanical, optical and electronic devices. Produced at an output of 75 parts per month, they are moulded by RTM with epoxy resin on deformable carbon fabric preforms and various glass/epoxy or carbon/epoxy inserts. After machining, thermoplastic parts and metal inserts are added. High-pressure gas cylinders for space use: filled with helium under several hundred bars, they are used in the propulsion systems of space vehicles and launchers. To gain a 30% to 50% mass reduction compared to metal cylinders, while optimizing the costs, Aerospatiale uses a thin metal inner liner for the sealing. This is used as the mandrel to manufacture the structural envelope by filament winding of Kevlar or carbon fibres which ensures mechanical resistance. Carbon fibres make it possible to save 10% in mass compared to Kevlar. For an operating pressure of 400 bars, the capacities are of 300 1. Rods for Airbus: since 1994, Aerospatiale has produced stress transmission rods that equip certain sections of the Airbus planes. Made in epoxy resin and carbon fibres, they bring a weight saving of approximately 30% compared to their equivalent in metal, for a comparable cost. They are produced by filament winding on a hardened sand mandrel. Arms of centrifugal machines for pilot training, external kerosene tanks for helicopters, cryogenic tanks for rockets made in carbon fibre reinforced composites. Breakable cap of the Aster container: This cap is intended for the sealing of pressurized containers and launching tubes. It must be torn by the passage of the projectile. The part must stand up to external attacks, tear under a limited load without ejection of fragments, and

The plastics industry: economic overview

be lightweight with small overall dimensions. The solution of draping carbon/epoxy prepregs was selected for the possibility to locally intercalate very different materials according to the functions required. 9 Carbon and Kevlar reinforced epoxy components for Helios, an unmanned aircraft that flies up to a 25 000 m altitude. Its 75 m wingspan is longer than that of a Boeing 747 airliner and it weighs not more than 700 kg. 9 Electromagnetic and dielectric structures in carbon fibre reinforced polycyanate composites. 9 Structural parts for satellites, missiles, aeronautics, fuselage and airframe elements in carbon fibre reinforced polycyanate composites. 9 Jet engine cones: a carbon fibre reinforced polyimide is selected for its high temperature behaviour. 9 Hydraulic fluid tanks for jet engines: the selected carbon reinforced bismaleimide resin is 180 ~ long-term resistant. 9 Stiffeners of acoustical panels: the carbon reinforced polyimide is chosen for its adaptability to the space environment. 9 Protection hoods: a carbon reinforced polyimide is chosen for its mechanical and thermal properties. 9 Parts intended to function in a space vacuum, thermal and mechanical protection for aeronautics in carbon reinforced polyimides. 9 Blades of helicopter tail rotors in glass and carbon reinforced epoxy. 9 Satellite antenna reflectors made of sandwich hulls carbon/aluminium honeycomb or Kevlar fibre/Kevlar honeycomb. 9 Polarizer for Mirage 2000: double sandwich selected was made of epoxy/carbon/honeycomb/carbon/honeycomb/glass. Automotive

9 9

Frames of F1 racing cars in carbon fibre reinforced composites. Frames of amphibious cars in epoxy/glass/carbon/Kevlar.

Miscellaneous

9 9

9 9 9

Compressor rings and bearings in carbon fibre reinforced thermoplastics (SUPreM). Compressor rings, dry bearings, sliding plates, pump pads, joint seatings, guiding rollers of grinder bands, manipulator inserts for glass bottle demoulding in carbon-reinforced polyimides. Coffee tables with plates in carbon fibre reinforced composite attached on metal frames. Roofs and central hulls of race trimarans, 25 m race monohulls, race boats in carbon fibre reinforced composites. 3-ray wheels for race bicycles, suspension arms for high-tech bicycles, hoops for tents in carbon fibre reinforced composites. 131

Thermosets and Composites

9

Racks and handling cases in carbon fibre reinforced composites for printed circuit board treatments. 9 Sockets for photocopiers, parts for printers, paper/print drum separation arms and bearings for photocopiers; running wheels in carbon fibre reinforced composites. 9 Air vents for slide projectors, discs of wiper thrusts, running wheels for microwave ovens in carbon fibre reinforced composites. 9 Compressor rings, pump pads in carbon fibre reinforced composites. 9 Gears of variable speed transmissions, joint seatings in carbon fibre reinforced composites. 2.13.4 Sustainable natural fibres 2.13.4.1. Consumption

The natural fibre consumption for polymer reinforcement is not known but is increasing. Natural fibres, for the activities within the scope of this work, are appreciated for general-purpose uses because of: 9 The environmental and ecological criteria. 9 Geopolitical motivations. 9 The fair mechanical performances. 9 The fair balance of weight/performances/cost. 2.13.4.2. Applications

Some examples of operational or development parts are listed below. 9 Scooter bodies, letterboxes made from polyester reinforced with coconut, banana and jute fibres in India. 9 SMC and BMC from polyester and jute or sisal or palm fibres in the USA. 9 Truck parts from rubbers, polyurethanes and thermoplastics reinforced with coconut, jute, banana or cotton fibres. 2.13.5 Other fibres and reinforcements

Each fibre has highly specific properties and applications. The consumptions are very low. Some examples of operational or development parts are listed below. 9 Polyethylene fibre reinforced composites" ductile ballistic materials that absorb the projectile energy while stretching. 9 Polyethylene fibre (Dyneema by DSM) reinforced composites for anti-ballistic products such as safety cockpit doors for Boeing 737 or 757 and others. 9 Ablative materials" composites of silica fibre reinforced phenolic matrix. These materials have a low thermal conductivity and density lower than 1.65. 132

The plastics industry: economic overview

9

Ablative materials: felts of silica fibres bound by an organic matrix. Of very low density (0.25), they present high insulating characteristics and good ablation behaviour. 9 Radomes and other elements requiring transparency at high service temperatures in quartz and fibreglass polycyanate prepregs. 9 Specific aeronautic elements, for example the wings of the F 14 by Grumman in boron fibre composites. 9 Lightened sports goods in boron/carbon fibre (Hy-Bor) composites. 9 Submicronic gears or connectors in whisker reinforced composites. 9 ESD parts in steel reinforced composites. 2.13.6 Self-reinforcing polymers

The self-reinforcing polymers are emerging but are promising. Some examples of operational or development parts are: 9 Underbody parts in self reinforced polypropylene (Curv) for the Audi A4. 9 Self-reinforced polymer implants by Bionx Implants. 2.13.7 Sandwich composites

Sandwich composites are used for general-purpose and high-tech parts. They are appreciated because of: 9 Very low densities. 9 High rigidity in flexion. 9 Good distribution of stresses without weak points. 9 High thermal insulation. Some examples of operational or development parts are listed below. Aeronautics, space

9 9 9 ,

9

Satellite solar panels: the structure is a sandwich composite with a honeycomb core and glass fibre reinforced epoxy resin facings. Satellite antenna reflectors: these reflectors are made of sandwich hulls carbon/aluminium honeycomb or Kevlar fibre/Kevlar honeycomb. Polarizer for Mirage 2000: the selected double sandwich was made of epoxy/carbon/honeycomb/carbon/honeycomb/glass. Careenages for Atlantique2: the sandwich composite is made of a honeycomb core with glass and Kevlar fibre reinforced epoxy skins treated to favour the electrostatic discharges. Helicopter rotor blades: since 1970, Aerospace and MBB have made them of sandwich composites of foam or honeycomb cores and glass or carbon reinforced skins with metal for the leading edges. The ends of the Super-Puma rotor blades are equipped with a dismountable salmon of complex shape moulded in carbon/epoxy. This salmon is 133

Thermosets and Composites

9

9 9 9

coated with nickel constituting a good protection against rain erosion and lightning. ATR72 jib cowls: these aerodynamic parts, slightly loaded, are made of a sandwich composite with a closed cell foam core covered with very thin carbon skins. It is R T M moulded with a profit of 30% compared to a traditional prepregs solution. Wall, ceiling and flooring sandwich panels. Soundproofing sandwich panels. Storage bins in sandwich composites.

Automotive, transport 9 Bus, tram, intercity train bodies in sandwich composites. 9 Floors of isothermal semi-trailers in laminated sandwich reinforced with a plywood core. 9 Body parts in sandwich composite with epoxy foam core and two steel skins. 9 Safety transparent sandwich composites for glazing: polyvinyl butyrate or ionoplast core and two glass skins. 9 Sandwich panels with polyurethane or PVC foam cores for thermal insulation of semi-trailers, containers, isothermal and refrigerating vehicles. The skins are in glass fibre reinforced polyester composites or metal foil. 9 Ceilings, outer and corridor sidewalls, toilet modules, sliding doors, luggage racks, folding tables, seats made of sandwich composites for high-speed trains. 9 Sandwich composites for drivers' cabs, bottom and covering panels of high-speed trains. 9 Cable cars in epoxy/Kevlar/honeycomb (Nomex). Building 9 False ceilings in sandwich composites. 9 Doors in sandwich composites. 9 Frontages of Heathrow Airport in sandwich Aerolam from Ciba (honeycomb aluminium with two epoxy/glass fibre skins), and Seville hospital in Trespa panels from Hoechst. 9 Frontages in a sandwich made of polyurethane or PVC foam core and skins of fire-resistant glass fibre reinforced polyester. The panels are attached on a steel framework. 9 Panels in a sandwich of expanded polystyrene core with composite skins. 9 Sandwich panels from foamed polyester inlaid with fine gravel or sand on one face. 9 Light partitions in sandwich composites based on phenolic resins for public buildings subjected to severe fire standards. 134

The plastics industry: economic overview

9

Light structural floors in sandwich composites.

Furniture

9

Decorative laminates with filled phenolic resin cores and decorative skins in amino resins for professional furniture" superstores, office automation and industry. 9 Decorative laminates with filled phenolic resin core and decorative skins in amino resins for kitchen, bathroom and other home or communal furniture (hospitals, schools, sports and social equipment). 9 Complete furniture of an exceptional room (Brochier room) of a famous hotel is a sandwich of Aerolam from Ciba (aluminium honeycomb with two epoxy/glass fibre skins). 9 Hollow signposts of bus stops in glass fibre reinforced polyesters filled with polyurethane foam injected in situ. Shipbuilding

9 9 9

Epoxy sandwich composites: hulls of race boats, submarine elements. Mega yachts 40 m long in sandwich composites. Sandwich panels with foam cores and glass fibre reinforced polyester skins: structures for offshore wellhead protection.

2.13.8

Hybrids

The hybrid technique is appreciated because of: 9 The simplicity of the processing methods. o The low processing costs. 9 The high degree of functional integration. 9 The removal of assembly and finishing operations. Some examples of operational or development parts are listed below. Aeronautics, space

9

o

o 9

9

Helicopter rotor bosses: the hemispherical laminated system made of alternating metal and elastomer layers makes it possible to save 65 % of the price and 50% of the mass compared to the traditional mechanical solution. Directional jet pipes: the chosen technical solution to ensure mobility is to articulate the jet pipes thanks to a flexible hemispherical laminate made of metal and elastomer layers. Plane wheels: the selected hybrid design comprises metal and epoxy/ carbon composites. Propellers blades of Transall: the hybrid design comprises a base tulip in steel, a polyurethane foam core, a carbon fibre braiding, an external skin in Kevlar and an epoxy resin moulded by the R T M process. High-pressure gas cylinders for space use: filled with helium under several hundred bars, they are used in the propulsion systems of space 135

Thermosets and Composites

vehicles and launchers. To save from 30% to 50% of the mass compared to metal cylinders, while optimizing the costs, Aerospatiale uses a thin metal inner liner for the sealing. This is used as a mandrel to manufacture the structural envelope by filament winding of Kevlar or carbon fibres that ensures mechanical resistance. The carbon fibres make it possible to save 10% on mass compared to Kevlar. For an operating pressure of 400 bars, the capacities are of 300 1. High-pressure gas cylinders for oxygen storage: Aerospatiale Missiles markets such parts with a 0.3-4 litres capacity for 210-325 bars operating pressures. Initially, these parts were intended for nitrogen storage and were manufactured from an aluminium inner liner without welds on which a composite glass/epoxy was wound. The storage volume compared to the mass of the bottle ranges from 200 to 300 1/kg. Currently, cylinders with thin stainless steel inner liners are produced for oxygen storage used by fighter pilots. Stored volumes reach 400 1/kg. Automotive

9

9 9 9

Engines (Polimotor, Ford projects) in hybrid composites of glass reinforced phenolic resin or epoxy and metal for the combustion chambers, cylinders and pistons. Footbrake pedals in metal/plastic hybrid. Frame-hull of concept car in composite/aluminium hybrid. Front-end in hybrid of glass bead filled PA6 and stamped metal.

Building, civil engineering

9

9

Incinerator chimney in hybrid of stainless steel with a liner in sandwich of glass fibre reinforced polyester and a core of polyurethane foam. Load-bearing panels for individual construction, Azurel by Dow made of wood and expanded polystyrene hybrid.

2.14 Applications of the main processing methods The RIM, sandwich and hybrid techniques were examined earlier in sections 2.12.1.2, 2.13.7 and 2.13.8. 2.14.1

Thermoplasticcomposites

The consumption of thermoplastic composites is increasing rapidly, competing with the SMC/BMC processes. Its share in the total composite consumption is roughly estimated at 25 %. These materials are appreciated because of: 9 The ability to mass-produce small to medium part sizes. 9 The application versatility from general-purpose to high-tech uses. 9 The recycling possibilities. 136

The plastics industry: economic overview

9 The high level of functional integration. 9 The final costs. Some examples of operational or development parts are listed below. Aeronautics, armaments

9 Tubular bangalore torpedoes for mine clearing, mine detecting probes in thermoplastic prepregs (Towflex). 9 Aileron jack hood for Airbus plane: its principal function is aerodynamic and the stresses are moderate. The part is thermoformed from a blank cut out in a pre-consolidated reinforced thermoplastic sheet. In spite of the high cost of this thermoplastic, the specific process implemented by Aerospatiale for this application leads to a 50% cost reduction compared to the use of a thermoset prepreg. 9 Camouflage supporting structures, telescopic cable rod sets, lattice masts and other lightweight structures in thermoplastic prepregs (Towflex). 9 Inboard lower access panels in carbon fibre reinforced PPS. 9 Fuselage panels: Aerospatiale is developing a fuselage panel (1.6 m by 2 m) in carbon fibre reinforced PEEK. This thermoplastic composite is made of a skin reinforced locally in the window zone. A metallized latticework is integrated on the external face for protection against lightning and other dielectric discharges. Automotive, transport

9 Vertical body panels of the Saturn by General Motors (1000 vehicles per day). 9 Fenders of the Class A by Mercedes-Benz, the Scenic and Laguna by Renault. 9 Front-ends of the Mini Cooper in long glass fibre reinforced polypropylene (Stamax). 9 Front-ends in long glass fibre reinforced polypropylene (Compel). . Instrument panel substrates in long fibre reinforced thermoplastic (Verton). 9 Steering housing in long glass fibre reinforced polypropylene (Celstran). 9 Proton battery trays in long glass fibre reinforced thermoplastic (Verton). 9 Front-ends in hybrid of glass bead filled PA6 and stamped metal. 9 Pedal supports of Peugeot 405 in GMT. 9 Frames of front and back seats, seat slides, instrument panels, consoles, package trays, parcel shelves and trays, glove compartments in GMT. 9 Hatchback doors, noise shields in GMT. 137

Thermosets and Composites

9 9 9 9

Protection sheets beneath the engine in GMT. Front-ends in GMT. Seat frames in GMT. Bumper beams in GMT.

Miscellaneous

9 9 9 9 9 9 9 9 9

Tiles of 30 cm by 1.2 m in GMT. Electrical shielding in long carbon fibre reinforced polyamide (or other thermoplastics). Outdoor electronic casings in glass reinforced thermoplastic (Tepex). Compressor rings and bearings in carbon fibre reinforced thermoplastics (SUPreM). Wafer-carriers in carbon fibre reinforced PEEK. Industrial paddle fans in long fibre reinforced thermoplastic (Verton). Rapier wheels for looms in carbon fibre reinforced thermoplastics (SUPreM). Convertible wheelchairs in glass fibre reinforced thermoplastic (Tepex). Orthopaedic or trauma medicine devices in carbon fibre reinforced P E E K (Orthtek by Greene Tweed).

2.14.2 SMC, BA,fC, ZMC

These are the main processes with a share of the total composite consumption roughly estimated as close to 40%. These processes are appreciated because of: 9 The ability for mass production. 9 The large part sizes. 9 The final costs. Some examples of operational or development parts are listed below. Automotive, transport

9 9 9 9 9 9 9 9 9 9

138

Shelters, ambulance cells, trailer or special vehicle bodies in glass fibre reinforced polyester, SMC. Roof and side spoilers in SMC for truck cabins. Truck front panels in standard or low density SMC. Cabin steps with integrated segment of wheelhousing in SMC for Mercedes trucks. Rear floors: one SMC part replaces 40 steel ones. Pickup truck boxes in SMC. Oil sumps in SMC. Decklids in SMC for the Mercedes Coupe. Particle filter systems in SMC ( B M W 3 and 5 series). Roofs or fenders of 4WD in glass fibre reinforced polyester composites, SMC.

The plastics industry: economic overview

9 9 9 9 9 9 9 9 9

Body panels, doors, rear doors, bonnets in SMC (possibly foamed) or ZMC. Window frames in SMC for high-speed trains. Pillars in SMC for the Berlin S-Bahn. Energy-absorbing bumpers, fenders in SMC. Luggage racks in SMC for trains. Bodies of medium output vehicles in glass fibre reinforced polyester composites (BMC or SMC). Engine covers and sumps in BMC. BMC tailgate of the Volvo V70. Seat frames in BMC.

Building, civil engineering

9 9 9 9 9 9 9

Balcony modules in SMC. Water gratings in SMC. Gas metering cabinets in SMC. Telegraph pole supports in glass fibre reinforced polyester (SMC). Sinks and counter tops in B M C for kitchens. Roof tiles in BMC, lighter and more aesthetical than clay and concrete ones. Exterior spotlight housings in BMC: no paint or rust.

Miscellaneous

9 9 9 9

Storage bins in halogen-free fire-retardant SMC or BMC. Public benches in BMC. Butterfly valves for water, acid and alkali solutions in vinylester BMC. Fuel cell plates in vinylester BMC.

2.14.3 RTM

This process is used, at a rough estimation, for less than 10% share of all composites. The R T M process is appreciated because of: 9 The ability for medium-sized production runs. 9 The large part sizes. 9 The medium investment and labour costs. Some examples of operational or development parts are listed below. 9 A T R 7 2 jib cowls: this aerodynamic part, slightly loaded, is made of a sandwich composite with a closed cell foam core covered with very thin carbon skins. It is R T M moulded with a profit of 30% compared to a traditional prepreg solution. 9 Empennages: this structural part is subjected to high stresses and elevated temperatures because of the hypersonic flying conditions: aerodynamic loading, vibrations, kinetic heating. Temperatures are in the range of 130-600 ~ according to the location. It is moulded by 139

Thermosets and Composites

9

9 9 9

RTM with a resin bismaleimide of high thermal and mechanical performances reinforced with carbon fabrics and braids. Electronic device boxes for shooting stations: the structure has a complex shape, must be light and rigid and support numerous mechanical, optical and electronic devices. Produced at an output of 75 parts per month, it is moulded by RTM with epoxy resin on deformable carbon fabric preforms and various glass/epoxy or carbon/epoxy inserts. After machining, thermoplastic parts and metal inserts are added. Bodies of niche or medium output vehicles in glass fibre reinforced polyester composites. Seat frames in RTM. Moulds in RTM for ceiling elements moulded in concrete.

2.14.4 Hand lay-up and spray lay-up These techniques are used to process approximately 15 % of the total for composites. These processes are appreciated because of: 9 The virtually unlimited part sizes. 9 The high wall thickness. 9 The ability to handle production from the prototype up to 1000 parts. 9 The low investment costs. Some examples of operational or development parts are listed below. Shipbuilding

9

9

9 9 9

Shipbuilding from boats up to minesweepers including all the types of race or pleasure boats, sailboards and surfboards; hulls of catamarans, hovercrafts, pilot boats, floating shopping-centres. Dry-dock caissons, sluice gates. Safety shelters, explosion-proof panels for offshore oil rigs in fireproofed glass fibre reinforced polyester. Safety shelters, explosion-proof panels for offshore oil rigs in fireproofed glass fibre reinforced phenolic resins. Swimming pools.

Automotive, transport 9 Shelters, ambulance cells, trailer or special vehicle bodies, prototypes or small series, in hand lay-up composites. 9 Cabins of heavy lorries, prototypes or small series, in glass and Kevlar fibre reinforced composites. 9 Monocoque frames of special vehicles in composites. 9 Engine hoods, trunk lids, hatchbacks, tailgates, prototypes or small series, in composites. 9 High-speed train noses in glass fibre reinforced polyester. 140

The plastics industry: economic overview

Building, civil engineering

9 9 9

Cornices, ornamental mouldings, sculptures in composites for hotels, casinos and buildings. Formwork, coffering in glass fibre reinforced polyester. Bonnets, bodies, housings for equipment protection (elevators, ventilators, fans) in glass fibre reinforced polyester.

Mechanics, industry

9 Settling basins. 9 Moulds for polyester parts moulded by the hand lay-up process. 9 Base plates. 9 Formworks, hoods, bonnets, panels, housings, casings for machines in glass fibre reinforced polyester. Furniture

9 9

9 9

Cabins or sanitary blocks in glass fibre reinforced polyester. Cabins and doors of public toilets: the polyester is not always sufficiently resistant to vandalism and in such cases is replaced by stainless steel. Traffic signs in glass fibre reinforced polyester attached on metal frames. Parisian newspaper kiosks in glass fibre reinforced polyester since 1982.

Miscellaneous

9

Farm equipment, cabins of transformers, seat cockles, buffing wheels, careenages for race motorbikes. 9 Giant advertising articles, bodies and subjects for carrousels, play areas, leisure parks; theatre, cinema, and TV decors. 9 High-tech or aesthetical packaging such as containers for the nuclear industry, aeronautics, and radomes, cases for double bass. 9 Fireproofed panels. 9 Electricity meter housings.

2.14.5 Pultrusion

The share for this process is less than 10% of the total composite consumption. This process is appreciated because of: 9 The unlimited part lengths. 9 The high wall thickness. 9 The low labour costs. Some examples of operational or development parts are listed below. 9 Gratings, duckboards in pultruded profiles for beaches and piers allowing the circulation of trucks. 9 Windows in pultruded profiles in the U S A and Canada. 141

Thermosets and Composites

9 9

Pillars and beams in pultruded tubes filled with concrete. Cable shelves for the Channel Tunnel, in fireproofed acrylic pultruded sections. 9 Pedestrian bridge (120 m long) in pultruded composites of continuous glass fibre mat reinforced polyester. 9 Cable shelves in pultruded profiles. 9 Handrails for building sites in pultruded profiles. 9 Gratings, duckboards in pultruded profiles. 9 Sloping roofs of petrol stations in pultruded 40% glass fibre reinforced polyester profiles. 2.14.6

Filament winding

Filament winding is used to process approximately 10% all composites. This process is appreciated because of: 9 The possibility to arrange the fibres to obtain the optimum reinforcement. 9 The broad diameters. 9 The fair wall thickness. 9 The possibility of medium production. Some examples of operational or development parts are listed below. 9 Piping up to 10 m in diameter by filament winding. 9 Chemical or wine tanks up to 10 m in diameter by filament winding. 9 Rods for Airbus: since 1994, Aerospatiale has produced stress transmission rods that equip certain sections of Airbus planes. Made in epoxy resin and carbon fibres, they bring a weight saving of roughly 30% compared to their equivalent in metal, for a comparable cost. They are produced by filament winding on a hardened sand mandrel. 9 Drive shafts of vans, heavy lorries, racing cars by filament winding. 9 Structures and flywheel systems for space in high level (80% volume fraction) carbon fibre reinforced polycyanates: cylinders are moulded by filament winding in sizes up to 25 mm wall thickness and 600 mm in diameter. 9 High-pressure gas cylinders for space use" filled with helium under several hundred bars, they are used in the propulsion systems of space vehicles and launchers. To save 30-50% mass compared to metal cylinders, while optimizing the costs, Aerospatiale uses a thin metal inner liner for the sealing. This is used as a mandrel to manufacture the structural envelope by filament winding of Kevlar or carbon fibres ensuring mechanical resistance. Carbon fibres make it possible to save 10% mass compared to Kevlar. For an operating pressure of 400 bars, the capacities are of 300 1. 142

The plastics industry: economic overview

2.14.7

Prepreg applications

This process is used for less than 10% of all composites. The prepregs are appreciated because of: 9 The possibility to arrange the fibres to obtain the optimum reinforcement. 9 The possibility to locally intercalate very different materials according to the functions to be ensured. 9 The broad size range. 9 The fair wall thickness. 9 The possibility of production from prototype to small series. Some examples of operational or development parts are listed below. 9 Breakable cap of the Aster container: This cap is intended for the sealing of pressurized containers and launching tubes. It must be torn by the passage of the projectile. The part must perform well against external attack, tear under a limited load without ejection of fragments, and be lightweight with small overall dimensions. The solution of draping carbon/epoxy prepregs was selected for the possibility to locally intercalate very different materials according to the required functions. 9 Stiffener plates to increase the performances of existing buildings or installations: the increase in the mechanical properties by a low volume and weight of carbon fibre reinforced epoxy prepregs makes it possible to increase supported loads. 9 Radomes and other elements requiring dielectric transparency at high service temperatures in quartz and fibreglass polycyanate prepregs. 9 Frames of F1 racing cars in epoxy/carbon prepregs. 9 Tubular bangalore torpedoes for mine clearing, mine detecting probes in thermoplastic prepregs (Towflex). 9 Camouflage supporting structures, telescopic cable rod sets, lattice masts and other lightweight structures in thermoplastic prepregs (Towflex). 2.14.8

Centrifugal moulding

Centrifugal moulding accounts for approximately 10% of all composite processing. This process is appreciated because of: 9 The possibility to obtain large diameter pipes, up to 5 m. 9 The two smooth faces. 9 The absence of voids. Some examples of operational or development parts are listed below. 9 Pipes up to 5 m in diameter. 9 Telephone posts centrifugally moulded in self-extinguishing glass fibre reinforced polyester. 9 Down pipes. 143

2.14.9 Continuous sheet moulding

This process accounts for approximately 10% of the total for composites. Sheet production is the only application. Some examples of operational or development parts are listed below. 9 Corrugated and ribbed roof sheeting. 9 Transparent sheeting using a special polyester resin with refractive index equal to that of the glass fibre. 9 Decorative sheeting.

References Website [1] spmp.sgbd.com Papers [2] E Pardos, Antec 2002, p. 2736 [3] E Szabo, International Polymer Science and Technology, Vol. 28, No.ll, (2001), p.T/1 [4] E Pardos, Antec 1999, p. 3034 [5] Modern Plastics, Resins Report 1995, 1996, 1997, 1998, 1999, 2000 [6] Industrie franqaise des mat~riaux composites, Ministbre de l'l~conomie, (May 2002)

Chapter 3

Basic criteria for the selection of thermosets

Thermosets and Composites

3.1 Evaluation of plastic properties The property measurement methods are standardized and only allow comparisons: the test specimens are produced under the best possible conditions, the deleterious factors are isolated to avoid any synergy, the duration of tests is inevitably limited, etc. In real life, this is almost always not the case and the results found in any literature will have to be verified, checked, interpreted and corrected with safety margins. Lastly, it is necessary to take account of the dispersion of the results and, particularly for the composites, of the property anisotropy. 3.1.1 Thermal behaviour

A temperature rise causes two different phenomena: 9 Immediate physical effects: o Decay of the modulus and other mechanical and physical properties, physicochemical softening. o Dimensional stability: reversible thermal expansion and, eventually, irreversible shrinkage and warpage. 9 Long-term effects: o Physical: more or less irreversible creep and relaxation. o Chemical: irreversible degradation of the material, decrease of the mechanical properties, even after a return to the ambient temperature. The maximum service temperatures depend on the duration of service time and the possible simultaneous application of mechanical stresses. A fall in temperature has only physical effects: 9 Increase in the modulus and rigidity. 9 Reduction in the impact resistance; the material can become brittle. 9 Eventually, crystallization for semi-crystalline polymers. Conventional heat measurements are: 9 Continuous use temperature. 9 U L temperature index. 9 Heat deflection t e m p e r a t u r e - HDT. 9 Vicat softening temperature. 9 Accelerated ageing. Continuous use temperature (CUT)

The continuous use temperature is an arbitrary temperature resulting from general experience and observation. It is the maximum temperature that an unstressed part can withstand for a very long time without failure or loss of function even if there is a significant reduction in the initial properties. This subjective value is not measurable and is deduced from ageing test interpretations and information collected in the technical literature. 146

Basic criteria for the selection of thermosets

UL temperature index

The temperature index, derived from long-term oven-ageing test programmes, is the maximum temperature that causes a 50% decay of the studied characteristics in the very long term. The U L temperature index depends on: 9 The grade 9 The thickness of the tested samples 9 The characteristics studied.

Influence of the grade For two grades of mineral-filled Nylon 66, of the same thickness and for the same properties, the U L temperature indexes are 65 ~ and 80 ~ For three grades of epoxy resins, of the same thickness and for the same properties, the U L temperature indexes are 160 ~ 170 ~ and 180 ~

Influence of the thickness The U L temperature indexes increase with the thickness of the samples. For example, for a defined polymer grade, the U L temperature indexes are: . 200 ~ for a 2.1 mm thickness. 9 50 ~ for a 0.4 mm thickness.

Influence of the studied characteristics There are three categories in the U L temperature indexes: . Electrical properties only. 9 Electrical and mechanical properties, impact excluded. 9 Electrical and mechanical properties, impact included. For the same grade in the same thickness, the three indices can be identical or different. Table 3.1 displays some examples. Like all the laboratory methods, the temperature index is an arbitrary measurement that must be interpreted and must constitute only one of the elements of judgement. Table 3.1

Examples of UL temperature indices

Thickness Electrical, mechanicalproperties, Electrical, mechanicalproperties, Electricalproperties (mm) includingimpact (~ excluding impact (~ (~ Melamine

1.6

150

150

150

Polyurethane

0.8

50

120

120

Polyimide

0.1

200

200

240

Heat deflection temperature (HDT)

The H D T is the temperature at which a standard deflection occurs for defined test samples subjected to a given bending load and a linear increase in temperature. The stresses usually selected are 0.46 MPa ( H D T B) or 1.8 MPa ( H D T A) and must be indicated with the results. In any case the polymer cannot be used under this load at this temperature. 147

Thermosets and Composites

Vicat softening temperature

The Vicat softening temperature is the temperature at which a standard deflection occurs for defined test samples subjected to a given linear temperature increase and a compression loading from a defined indenter of a specified weight. This load used is often 10 N (Vicat A) or 50 N (Vicat B). They must be indicated with the results. In any case the polymer cannot be used under this compression load at this temperature. Accelerated ageing

Conventional accelerated ageing tests consist in exposing defined samples to controlled-temperature air in ovens protected from light, ozone and chemicals, for one or more given times. The degradation is measured by the variation of one or several physical or mechanical characteristics during the ageing. The variations of impact resistance, hardness, tensile or flexural strength are the most frequently studied. Accelerated ageing is an arbitrary measurement that must be interpreted and must constitute only one of the elements of judgement: 9 Under identical conditions, the properties do not all degrade at the same rate. 9 It is impossible to establish a direct relationship between the accelerated ageing of a part and its real lifespan. For an unknown polymer, the results of accelerated ageing must be compared with those obtained on a known polymer of a very similar formula. 3.1.2 Low temperature behaviour

There are many methods to test the low temperature behaviour. It is necessary to distinguish: 9 The short-term tests: brittle point, low temperature impact test, low temperature rigidity, and elastic recovery for elastomers such as silicone. 9 The long-term tests, crystallization tests, which make it possible to detect a slow crystallization by the evolution of the hardness with time. Brittle point

The - very fuzzy - definition of the brittle point is based on a more or less sudden reduction in the impact resistance or the flexibility. The indicated values must be carefully considered. 9 Low temperature impact tests: cooled samples are subjected to a conventional impact test. Generally, the most used temperatures are -20 ~ ~ or -40 ~ 9 Low temperature brittleness or toughness: the samples are cooled at a temperature far lower than the supposed temperature of brittleness, then they are gradually warmed up. At each selected step temperature, the test specimens are subjected to a specified impact. The temperature 148

Basic criteria for the selection of thermosets

at which specimens deteriorated or failed is the "brittle point". In some other tests, the lowest temperature to which specimens can be cooled without deterioration is regarded as the limiting t e m p e r a t u r e of "toughness" or "no brittleness". Low t e m p e r a t u r e film flexibility: the film or sheet is rolled up on a specified m a n d r e l at one or several temperatures. Rigidity in torsion: "Clash & Berg" "Gehman" tests

These tests are based on the evolution of the static or dynamic torsion modulus when the t e m p e r a t u r e decreases. Results can be: 9 Plotted versus the temperature. 9 Expressed as the value of the modulus for specified temperatures. 9 R e c o r d e d as the t e m p e r a t u r e s for which the modulus is 2, 5, 10, 100... times higher than that m e a s u r e d at r o o m t e m p e r a t u r e . Crystallization test

The crystallization test consists in measuring the evolution of hardness at a specified t e m p e r a t u r e over several weeks. This m e t h o d is of special interest for those polymers that can slowly crystallize at service temperatures. 3.1.3 Mechanical properties

A lot of current characteristics are deduced from the stress/strain curves. Figure 3.1 shows the case of two tensile behaviours: 9 One for a brittle polymer, where the break arises immediately after the yield point or coincides with it. 9 The other for a ductile polymer, where the b r e a k is far from the yield point. Yield point Ip, ~'Brea k imit of elasticity

~ '

4 Break

"Limitof elasticity Strain

-~

Figure 3.1. Tensilebehaviour of polymers

149

Thermosets and Composites

Although resulting from low-speed tests, these curves give results only under instantaneous loads whereas in real life the parts are exposed to long-term stresses or strains. In this case, it will be necessary to refer to the long-term mechanical properties. Conventional mechanical measurements are: 9 Elastic modulus 9 Yield point o Stress and strain at yield 9 Ultimate stress and strain 9 Impact test. The loading types generally now used are: 9 Tensile 9 Flexural 9 Compression. In this case, it is generally a unidirectional compression. Bulk compression is rarely measured, except for modelling. Elastic modulus

The elastic modulus is the slope of the tangent at the origin of the stress/ strain curve. The tensile or compression modulus is often called Young's modulus whereas the torsion modulus is often called shear modulus or Coulomb's modulus. Yield point

The yield point is the first point of the stress/strain curve for which one notes an increase in the strain without an increase in the stress. Parts must always operate well below this point during service. Stress and strain at yield

Stress and strain at yield are the values of the stress and strain corresponding to the yield point. Ultimate stress and strain

Ultimate stress and strain, or stress and strain at break, are the values corresponding to the breaking of the samples. Interlaminar shear strength (ILSS)

The interlaminar shear strength (ILSS) is the value of the shear strength producing a delamination between two composite layers along the plane of their interface. The measurement is made by a three-point deflection test with the supports very close together. Impact test

The impact tests measure the energy absorbed during a specified impact of a standard weight striking, at a given speed, a test sample clamped with a suitable system. The hammer can be a falling weight or, more often, a pendulum. In this case, the samples can be smooth or notched. The results 150

Basic criteria for the selection of thermosets

depend on the molecular orientation and the degree of crystallization of the material in the sample, its size, the clamping system, the possible notch and its form, the mass and the speed of striking. The values found in the literature, even for instrumented multi-axial impact (ISO 6603-2:2000), can be used only to help choose and do not replace tests on real parts. The Izod and Charpy impact tests are mostly used. A defined pendulum strikes the specimen sample, notched or not, clamped with a defined device. The absorbed energy is calculated and expressed: 9 In kJ/m2: the absorbed energy divided by the specimen area at the notch. 9 J/m: the absorbed energy divided by the length of the notch, which is also the thickness of the sample. There is no true correlation between the various methods. The notched impact tests tend to measure the notch sensitivity rather than the real impact strength of the material. It corresponds better to the parts with sharp edges, ribs and so on. Hardness The most usual test methods are:

. 9 9 9 9

Shore A for soft polymers. Shore D for hard polymers. I R H D , International Rubber Hardness. Rockwell R, M and others. Ball indentation.

3.1.4 Long-term mechanical properties

Plastics have a viscoelastic behaviour that increases with the temperature: their properties are a function of the duration of load application. Creep

Creep is the time-dependent strain induced by a constant mechanical loading. The strain is a function of the stress level, the time for which the stress is applied, and the temperature. The results can be presented graphically in various ways by combining these three parameters or in a quantified form: the creep modulus. The creep modulus for a specified stress, time and temperature is the value of the stress divided by the strain measured after the selected time. Relaxation

Relaxation is the time-dependent stress resulting from a constant strain. The stress is a function ofthe strain level, the application time, and the temperature. The results of tests at a defined temperature can be presented as the curve of the load versus the time or the curve of the stress retention versus the time. 151

Thermosets and Composites

The stress retention for a defined time and temperature is the quotient of the actual measured stress by the original stress at time zero.

Fatigue The repeated mechanical loading of a polymer leads to a speedier failure than an instant loading. The Wohler curves or SN curves plot the level of stress or strain (S) leading to failure after N cycles of repeated loading. The results depend on the stress type and level, the frequency, the surrounding temperature, and the geometry of the sample. We must note that the temperature of the material rises under the dynamic loading with the usual consequences, such as modulus reduction and ageing. 3.1.5 Long-term light and UV resistance

Polymers are organic materials and are sensitive to natural or artificial UV sources. This is of the first importance for outdoor exposure of nonprotected parts and for some industrial applications such as electrical welding, photocopier light exposure devices... The tests can be done by exposure, under quite precise conditions (angle of incidence, positioning, temperature, water vapour, surface water...): 9 To the natural light of the sun, or 9 To the radiation of xenon lamps (Xenotest, WeatherOmeter) or others. The effects of ageing appear mainly in three ways: 9 Mechanical property degradation. 9 Modification, for the clear grades, of aspect and colour, chalking, yellowing, browning, discoloration... 9 Surface crazing and cracking. The interpretation of the results is difficult because of: 9 Climate diversity. 9 The risks of industrial or domestic pollution in real life. 9 The lack of correlation between artificial and natural ageing. 9 The different degradation kinetics of the various properties. 3.1.6 Chemical resistance by immersion or contact

The action of a chemical on a plastic can induce three concomitant phenomena: 9 Absorption of the liquid by the plastic, which leads to a swelling of the part. 9 Extraction by the liquid of some material components (plasticizers in particular, antidegradants, monomers and oligomers, colorants). This extraction can reduce the apparent swelling of the part, or even lead to a retraction. 152

Basic criteria for the selection of thermosets

9

Pollution of the liquid by the immersed polymer: desorption of particles and ingredients. The tests themselves consist in immersing the sample in the liquid under consideration for a given time at a given temperature. The generated effects can be highlighted in several manners" 9 Evaluation of the volume, weight or dimension swelling of the sample. 9 Percentage of extracted materials. 9 Degradation of the mechanical characteristics, either immediately, or after drying. For these tests, the service liquids (solvent, oil, hydraulic fluid, acid, base...) can be used but, to ease the establishment of specifications and comparative tests, one often uses reference solvents, oils, fuels. The most current are I R M 901,902 or 903 oils (which replace A S T M 1, 2 and 3 oils), fuels or solvents A S T M A, B, C. Environmental stress cracking (ESC)

When a plastic in air is subjected to a stress or a strain below its yield point, cracking can occur after a very long duration. The simultaneous exposure to a chemical environment under the same stress or strain can lead to a spectacular reduction of the failure time. The accelerated cracking in this way corresponds to the "Environmental stress cracking" (ESC). 3.1.7 Electrical properties

Polymers 9 The 9 The 9 The

are naturally insulating and can be characterized by: volume resistivity and surface resistivity dielectric strength arc resistance.

The volume resistivity- ASTM D257 and IEC 93

The volume resistivity is the electrical resistance of a polymer sample of unit area and unit thickness when electrodes put on two opposite faces apply an electrical potential across it. The volume resistivity is expressed in ohm.cm. 9 Insulating polymers must have a resistivity higher than 10 9 ~/cm. 9 Conductive polymers must have a resistivity lower than10 5 ~/cm. The surface resistivity- ASTM D257 and IEC 93

The surface resistivity is the electrical resistance between two electrodes put on the same face of a polymer sample. The surface resistivity is expressed in ohm (or more rarely in ohm per square). The dielectric strength

The dielectric strength is the maximum voltage before breakdown divided by the thickness of the sample. It is expressed in kV/mm. 153

Thermosets and Composites

The arc resistance

The arc resistance is the time necessary to make the polymer surface conductive by action of a high voltage, low current arc. It is expressed in seconds.

Gas permeability The determination of the gas permeability under given conditions of pressure and temperature is based on the measure of the gas flow rate through a polymer membrane of defined size. The permeability is expressed in mZ/Pa.s. The gas permeability depends on the chemical nature of the polymer and the gas (air, nitrogen, CO 2, moisture...). For the same polymer, the results are often very different depending on the gases. 3.1.8

Flammability The fire behaviour depends, initially, on the nature of the polymer. However, the use of fireproofing agents, special plasticizers and specific fillers can modify this behaviour very significantly. The tests relate to: 9 The tendency to combustion: U L 94 ratings, oxygen index. 9 The smoke opacity. 9 The toxicity and corrosivity of the smoke. 3.1.9

UL 94 ratings

The UL94 ratings provide basic information on the material's ability to extinguish a flame, once ignited. The positioning of the sample (horizontal: H; or vertical: V), the burning rate, the extinguish time and dripping are considered. The main categories are: 9 V 0 : the most difficult to burn, extinguished after 10 s, no drips. 9 VI: extinguished after 30 s, no drips. 9 V2: extinguished after 30 s, flaming particles or drips permitted. 9 5V: extinguished after 60 s, flaming particles or drips permitted. 9 HB: Burning horizontally at a 76 mm/min maximum rate. The U L rating depends on the exact grade and the sample thickness. For the same grade of epoxy resin the U L ratings are" 9 HB for a 1.5 mm thickness. 9 V0 for a 6 m m thickness. Oxygen index

The oxygen index is the minimum percentage of oxygen in an atmosphere of oxygen and nitrogen that sustains the flame of an ignited polymer sample. 154

Basic criteria for the selection of thermosets

Smoke opacity

The smoke opacity is measured by the optical density. 3.1.10 Optical properties

The most usual optical properties are: 9 Light absorption" the percentage of light absorbed by the polymer versus the incident light. 9 Light transmission: the percentage of light transmitted through the polymer versus the incident light. 9 Haze is induced by light scattering within the polymer. A water haze can be caused by absorbed moisture. 9 Gloss: capacity of the polymer surface to reflect light in given directions.

3.2 ISO standards concerning polymer testing The silicones and soft polyurethanes are tested with elastomer standards; some thermosets are used as adhesives and sealants. Consequently, the following standards mainly concern plastics and composites but also adhesives and elastomers. 3.2.1 Moulding of test specimens

ISO 294-2:1996 P l a s t i c s - Injection moulding of test specimens of thermoplastic materials- Part 2: Small tensile bars ISO 295:1991 Plastics - Compression moulding of test specimens of thermosetting materials ISO 1268-3:2000 Fibre-reinforced plastics- Methods of producing test p l a t e s - Part 3: Wet compression moulding 3.2.2 Mechanical properties Tensile properties

ISO 37:1994 Rubber, vulcanized or thermoplastic- Determination of tensile stress-strain properties ISO 527-1:1993 Plastics- Determination of tensile p r o p e r t i e s - Part 1: General principles ISO 527-2:1993 Plastics- Determination of tensile p r o p e r t i e s - Part 2: Test conditions for moulding and extrusion plastics ISO 527-3:1995 Plastics- Determination of tensile properties - Part 3: Test conditions for films and sheets ISO 527-4:1997 Plastics- Determination of tensile p r o p e r t i e s - Part 4: Test conditions for isotropic and orthotropic fibre-reinforced plastic composites 155

Thermosets and Composites

ISO 527-5:1997 Plastics- Determination of tensile properties - Part 5: Test conditions for unidirectional fibre-reinforced plastic composites ISO 1798:1997 Flexible cellular polymeric m a t e r i a l s - Determination of tensile strength and elongation at break ISO 1926:1979 Cellular plastics- Determination of tensile properties of rigid materials ISO 4587:1995 Adhesives - Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies ISO 5893:2002 Rubber and plastics test e q u i p m e n t - Tensile, flexural and compression types (constant rate of traverse) - Specification ISO 6237:1987 Adhesives-Wood-to-wood adhesive bonds-Determination of shear strength by tensile loading ISO 6922:1987 Adhesives - Determination of tensile strength of butt joints Flexural properties ISO 178:2001 Plastics- Determination of flexural properties ISO 1209-1:1990 Cellular plastics, r i g i d - Flexural t e s t s - Part 1: Bending test IS O1209-2:1990Cellularplastics,rigid--Hexuraltests-Part2 :Determination of flexural properties ISO 3597-2:1993 Textile-glass-reinforced p l a s t i c s - Determination of mechanical properties on rods made of roving-reinforced r e s i n - Part 2: Determination of flexural strength ISO 5893:2002 Rubber and plastics test e q u i p m e n t - Tensile, flexural and compression types (constant rate of traverse) - Specification ISO 6721-3:1994 P l a s t i c s - Determination of dynamic mechanical p r o p e r t i e s - Part 3: Flexural v i b r a t i o n - Resonance-curve method ISO 6721-5:1996 P l a s t i c s - Determination of dynamic mechanical properties - Part 5: Flexural v i b r a t i o n - Non-resonance method ISO 14125:1998 Fibre-reinforced plastic c o m p o s i t e s - Determination of flexural properties Compression properties ISO 844:2001 Rigid cellular plastics - Determination of compression properties ISO 3386-1:1986 Polymeric materials, cellular flexible- Determination of stress-strain characteristics in c o m p r e s s i o n - Part 1: Low-density materials ISO 3386-2:1997 Flexible cellular polymeric m a t e r i a l s - Determination of stress-strain characteristics in c o m p r e s s i o n - Part 2: High-density materials ISO 5893:2002 Rubber and plastics test e q u i p m e n t - Tensile, flexural and compression types (constant rate of traverse) - Specification 156

Basic criteria for the selection of thermosets

ISO 7743:1989 Rubber, vulcanized or t h e r m o p l a s t i c - Determination of compression stress-strain properties ISO 13362:2000 Flexible cellular polymeric materials - Determination of compression set under humid conditions Shear properties ISO 1827:1991 Rubber, vulcanized or t h e r m o p l a s t i c - Determination of modulus in shear or adhesion to rigid plates - Quadruple shear method ISO 1922:2001 Rigid cellular plastics- Determination of shear strength ISO 4587:1995 A d h e s i v e s - Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies ISO 6237:1987 Adhesives - Wood-to-wood adhesive bonds Determination of shear strength by tensile loading ISO 6238:2001 Adhesives - Wood-to-wood adhesive bonds Determination of shear strength by compressive loading ISO 6721-6:1996 Plastics - Determination of dynamic mechanical properties - Part 6: Shear vibration - Non-resonance method ISO 6721-8:1997 P l a s t i c s - Determination of dynamic mechanical p r o p e r t i e s - Part 8: Longitudinal and shear v i b r a t i o n - Wave-propagation method ISO 6721-10:1999 P l a s t i c s - Determination of dynamic mechanical p r o p e r t i e s - Part 10: Complex shear viscosity using a parallel-plate oscillatory rheometer ISO 9311-2:2002 Adhesives for thermoplastic piping s y s t e m s - Part 2: Determination of shear strength ISO 9653:1998 A d h e s i v e s - Test method for shear impact strength of adhesive bonds ISO 9664:1993 Adhesives - Test methods for fatigue properties of structural adhesives in tensile shear ISO 10123:1990 Adhesives - Determination of shear strength of anaerobic adhesives using pin-and-collar specimens ISO 11003-1:2001 A d h e s i v e s - Determination of shear behaviour of structural a d h e s i v e s - Part 1: Torsion test method using butt-bonded hollow cylinders ISO 11003-2:2001 A d h e s i v e s - Determination of shear behaviour of structural a d h e s i v e s - Part 2: Tensile test method using thick adherends ISO 13445:1995 Adhesives - Determination of shear strength of adhesive bonds between rigid substrates by the block-shear method ISO 14129:1997 Fibre-reinforced plastic c o m p o s i t e s - Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by the plus or minus 45 degree tension test method ISO 15108:1998 Adhesives - Determination of strength of bonded joints using a bending-shear method 157

Thermosets and Composites

ISO 15310:1999 Fibre-reinforced plastic c o m p o s i t e s - Determination of the in-plane shear modulus by the plate twist method Torsion properties

ISO 458-1:1985 Plastics - Determination of stiffness in torsion of flexible m a t e r i a l s - Part 1: General method ISO 458-2:1985 Plastics - Determination of stiffness in torsion of flexible materials - Part 2" Application to plasticized compounds of homopolymers and copolymers of vinyl chloride ISO 4663:1986 R u b b e r - Determination of dynamic behaviour of vulcanizates at low frequencies - Torsion pendulum method ISO 6721-2:1994 P l a s t i c s - Determination of dynamic mechanical properties - Part 2: Torsion-pendulum method ISO 11003-1:2001 A d h e s i v e s - Determination of shear behaviour of structural a d h e s i v e s - Part 1" Torsion test method using butt-bonded hollow cylinders Interlaminar properties

ISO 3597-4:1993 Textile-glass-reinforced p l a s t i c s - Determination of mechanical properties on rods made of roving-reinforced r e s i n - Part 4: Determination of apparent interlaminar shear strength ISO 14130:1997 Fibre-reinforced plastic c o m p o s i t e s - Determination of apparent interlaminar shear strength by short-beam method ISO 15024:2001 Fibre-reinforced plastic c o m p o s i t e s - Determination of mode I interlaminar fracture toughness, GIC, for unidirectionally reinforced materials Hardness

ISO 48:1994 Rubber, vulcanized or t h e r m o p l a s t i c - Determination of hardness (hardness between 10 I R H D and 100 I R H D ) ISO 868:1985 Plastics and ebonite - Determination of indentation hardness by means of a durometer (Shore hardness) ISO 2039-1:2001 P l a s t i c s - Determination of h a r d n e s s - Part 1: Ball indentation method ISO 2039-2:1987 Plastics - Determination of hardness - Part 2: Rockwell hardness ISO 2439:1997 Flexible cellular polymeric m a t e r i a l s - Determination of hardness (indentation technique) ISO 6123-1:1982 Rubber or plastics covered rollers - Specifications - Part 1: Requirements for hardness ISO 7267-1:1997 Rubber-covered rollers - Determination of apparent h a r d n e s s - Part 1: I R H D method ISO 7267-2:1986 Rubber-covered r o l l e r s - Determination of apparent h a r d n e s s - Part 2: Shore-type durometer method 158

Basic criteria for the selection of thermosets

ISO 7267-3:1988 Rubber-covered r o l l e r s - Determination of apparent hardness- Part 3: Pusey and Jones method ISO 7619:1997 R u b b e r - Determination of indentation hardness by means of pocket hardness meters

Impact testing ISO 179-1:2000 Plastics- Determination of Charpy impact propertiesPart 1" Non-instrumented impact test ISO 179-2:1997 Plastics- Determination of Charpy impact p r o p e r t i e s Part 2: Instrumented impact test ISO 180:2000 Plastics - Determination of Izod impact strength ISO 974:2000 Plastics - Determination of the brittleness temperature by impact ISO 2897-1:1997 Plastics- Impact-resistant polystyrene (PS-I) moulding and extrusion m a t e r i a l s - Part 1" Designation system and basis for specifications ISO 2897-2:1994 Plastics- Impact-resistant polystyrene (PS-I) moulding and extrusion m a t e r i a l s - Part 2: Preparation of test specimens and determination of properties ISO 6402-2:1994 Plastics- Impact-resistant acrylonitrile/styrene (ASA, AES, ACS) moulding and extrusion materials, excluding butadienemodified m a t e r i a l s - Part 2: Preparation of test specimens and determination of properties ISO 6603-1:2000 Plastics- Determination of puncture impact behaviour of rigid plastics - Part 1" Non-instrumented impact testing ISO 6603-2:2000 Plastics- Determination of puncture impact behaviour of rigid plastics - Part 2: Instrumented impact testing ISO 7765-1:1988 Plastics film and s h e e t i n g - Determination of impact resistance by the free-falling dart m e t h o d - Part 1" Staircase methods ISO 7765-2:1994 Plastics film and s h e e t i n g - Determination of impact resistance by the free-falling dart m e t h o d - Part 2: Instrumented puncture test ISO 8256:1990 Plastics- Determination of tensile-impact strength ISO 9653:1998 A d h e s i v e s - Test method for shear impact strength of adhesive bonds ISO 11343:1993 A d h e s i v e s - Determination of dynamic resistance to cleavage of high strength adhesive bonds under impact conditions - Wedge impact method ISO 13802:1999 Plastics - Verification of pendulum impact-testing machines - Charpy, Izod and tensile impact-testing ISO 14631:1999 Extruded sheets of impact-modified polystyrene (PS-I) Requirements and test methods 159

Thermosets and Composites

3.2.3 Thermomechanical properties HDT

ISO 75-1:1993 P l a s t i c s - Determination of temperature of deflection under l o a d - Part 1: General test method ISO 75-2:1993 P l a s t i c s - Determination of temperature of deflection under l o a d - Part 2: Plastics and ebonite ISO 75-3:1993 P l a s t i c s - Determination of temperature of deflection under load - Part 3: High-strength thermosetting laminates and long-fibrereinforced plastics Vicat softening temperature

ISO 306:1994 P l a s t i c s - Thermoplastic m a t e r i a l s - Determination of Vicat softening temperature (VST) Low temperature

ISO 812:1991 Rubber, vulcanized- Determination of low-temperature brittleness ISO 974:2000 Plastics - Determination of the brittleness temperature by impact ISO 1432:1988 Rubber, vulcanized or thermoplastic- Determination of low temperature stiffening (Gehman test) ISO 2921:1997 Rubber, vulcanized- Determination of low-temperature characteristics- Temperature-retraction procedure (TR test) Crystallization

ISO 6471"1994 Rubber, vulcanized- Determination of crystallization effects under compression ISO 3387:1994 R u b b e r - Determination of crystallization effects by hardness measurements ISO 6471:1994 Rubber, vulcanized- Determination of crystallization effects under compression ISO 11357-3:1999 Plastics- Differential scanning calorimetry (DSC) Part 3" Determination of temperature and enthalpy of melting and crystallization ISO 11357-7:2002 Plastics- Differential scanning calorimetry (DSC) Part 7: Determination of crystallization kinetics 3.2.4 Long.term properties Accelerated ageing

ISO 188:1998 Rubber, vulcanized or thermoplastic- Accelerated ageing and heat resistance tests ISO 2440:1997 Flexible and rigid cellular polymeric m a t e r i a l s Accelerated ageing tests 160

Basic criteria for the selection of thermosets

ISO 6914:1985 Rubber, v u l c a n i z e d - Determination of ageing characteristics by measurement of stress at a given elongation ISO 9142:1990 Adhesives - Guide to the selection of standard laboratory ageing conditions for testing bonded joints Creep

ISO 899-1:1993 Plastics- Determination of creep b e h a v i o u r - Part 1: Tensile creep ISO 899-2:1993 Plastics- Determination of creep b e h a v i o u r - Part 2: Flexural creep by three-point loading ISO 2285:2001 Rubber, vulcanized or thermoplastic- Determination of tension set under constant elongation, and of tension set, elongation and creep under constant tensile load ISO 7616:1986 Cellular plastics, r i g i d - Determination of compressive creep under specified load and temperature conditions ISO 7850:1986 Cellular plastics, r i g i d - Determination of compressive creep ISO 8013:1988 Rubber, v u l c a n i z e d - Determination of creep in compression or shear ISO 10066:1991 Flexible cellular polymeric materials- Determination of creep in compression Compression and tension set

ISO 815:1991 Rubber, vulcanized or thermoplastic- Determination of compression set at ambient, elevated or low temperatures ISO 1856:2000 Flexible cellular polymeric materials - Determination of compression set ISO 2285:2001 Rubber, vulcanized or thermoplastic- Determination of tension set under constant elongation, and of tension set, elongation and creep under constant tensile load Relaxation

ISO 3384:1999 Rubber, vulcanized or thermoplastic- Determination of stress relaxation in compression at ambient and at elevated temperatures Fatigue and dynamic mechanical properties

ISO 6721-4:1994 P l a s t i c s - Determination of dynamic mechanical properties- Part 4: Tensile vibration- Non-resonance method ISO 6721-9:1997 P l a s t i c s - Determination of dynamic mechanical properties - Part 9: Tensile vibration- Sonic-pulse propagation method ISO 3385:1989 Flexible cellular polymeric materials - Determination of fatigue by constant-load pounding ISO 4666-1:1982 Rubber, v u l c a n i z e d - Determination of temperature rise and resistance to fatigue in flexometer testing- Part 1" Basic principles 161

Thermosets and Composites

ISO 4666-2:1982 Rubber, v u l c a n i z e d - Determination of temperature rise and resistance to fatigue in flexometer t e s t i n g - Part 2: Rotary flexometer ISO 4666-3:1982 Rubber, v u l c a n i z e d - Determination of temperature rise and resistance to fatigue in flexometer t e s t i n g - Part 3: Compression flexometer ISO 6943:1984 Rubber, vulcanized- Determination of tension fatigue ISO 8659:1989 Thermoplastics valves - Fatigue s t r e n g t h - Test method ISO 9664:1993 A d h e s i v e s - Test methods for fatigue properties of structural adhesives in tensile shear ISO 15850:2002 Plastics- Determination of tension-tension fatigue crack p r o p a g a t i o n - Linear elastic fracture mechanics (LEFM) approach Light resistance ISO 4582:1998 P l a s t i c s - Determination of changes in colour and variations in properties after exposure to daylight under glass, natural weathering or laboratory light sources ISO 4892-1:1999 P l a s t i c s - Methods of exposure to laboratory light s o u r c e s - Part 1: General guidance ISO 4892-2:1994 P l a s t i c s - Methods of exposure to laboratory light s o u r c e s - Part 2: Xenon-arc sources ISO 4892-3:1994 P l a s t i c s - Methods of exposure to laboratory light s o u r c e s - Part 3: Fluorescent UV lamps ISO 4892-4:1994 P l a s t i c s - Methods of exposure to laboratory light s o u r c e s - Part 4: Open-flame carbon-arc lamps 3.2.5 Fluid contact behaviour

Chemical behaviour ISO 175:1999 P l a s t i c s - Methods of test for the determination of the effects of immersion in liquid chemicals ISO 4661-2:1987 Rubber, v u l c a n i z e d - Preparation of samples and test pieces - Part 2: Chemical tests ISO 6252:1992 Plastics- Determination of environmental stress cracking (ESC) - Constant-tensile-stress method ISO/TR 7620:1986 Rubber materials - Chemical resistance Gas, humidity and vapour permeability ISO 1663:1999 Rigid cellular plastics - Determination of water vapour transmission properties ISO 2556:1974 Plastics - Determination of the gas transmission rate of films and thin sheets under atmospheric pressure - Manometric method ISO 6179:1998 Rubber, vulcanized or thermoplastic- Rubber sheets and rubber-coated fabrics - Determination of transmission rate of volatile liquids (gravimetric technique) 162

Basic criteria for the selection of thermosets

ISO 15105-1:2002 Plastics - Film and sheeting - D e t e r m i n a t i o n of gastransmission r a t e - Part 1" Differential-pressure m e t h o d ISO 15106-1:2003 Plastics - Film and sheeting - D e t e r m i n a t i o n of water vapour transmission rate - Part 1: H u m i d i t y detection sensor m e t h o d ISO 15106-2:2003 Plastics " F i l m and sheeting - D e t e r m i n a t i o n of water vapour transmission r a t e - Part 2: Infrared detection sensor m e t h o d ISO 15106-3:2003 Plastics - Film and sheeting - D e t e r m i n a t i o n of water vapour transmission r a t e - Part 3: Electrolytic detection sensor m e t h o d

3.2.6 Electrical properties ISO 1853:1998 Conducting and dissipative rubbers, vulcanized or t h e r m o p l a s t i c - M e a s u r e m e n t of resistivity ISO 2878:1987 Rubber, vulcanized - Antistatic and conductive p r o d u c t s - D e t e r m i n a t i o n of electrical resistance ISO 2882:1979 Rubber, v u l c a n i z e d - Antistatic and conductive products for hospital use - Electrical resistance limits ISO 2883:1980 Rubber, v u l c a n i z e d - Antistatic and conductive products for industrial use - Electrical resistance limits ISO 3915:1981 Plastics- M e a s u r e m e n t of resistivity of conductive plastics 3.2.7 Oxygen index, flammability, smoke generation

ISO 4589-1:1996 Plastics - D e t e r m i n a t i o n of burning behaviour by oxygen i n d e x - Part 1: Guidance ISO 4589-2:1996 Plastics - D e t e r m i n a t i o n of burning behaviour by oxygen i n d e x - Part 2: A m b i e n t - t e m p e r a t u r e test ISO 4589-3:1996 P l a s t i c s - D e t e r m i n a t i o n of burning behaviour by oxygen i n d e x - Part 3: E l e v a t e d - t e m p e r a t u r e test ISO 5659-1:1996 P l a s t i c s - Smoke g e n e r a t i o n - Part 1: Guidance on optical-density testing ISO 5659-2:1994 P l a s t i c s - Smoke g e n e r a t i o n - Part 2: D e t e r m i n a t i o n of optical density by a single-chamber test I S O / T R 5659-3:1999 P l a s t i c s - Smoke g e n e r a t i o n - Part 3: D e t e r m i n a t i o n of optical density by a dynamic-flow m e t h o d ISO 11907-1:1998 P l a s t i c s - Smoke g e n e r a t i o n - D e t e r m i n a t i o n of the corrosivity of fire effluents - Part 1: Guidance ISO 11907-2:1995 Plastics - Smoke g e n e r a t i o n - D e t e r m i n a t i o n of the corrosivity of fire effluents - Part 2" Static m e t h o d ISO 11907-3:1998 P l a s t i c s - Smoke g e n e r a t i o n - D e t e r m i n a t i o n of the corrosivity of fire effluents - Part 3: D y n a m i c decomposition m e t h o d using a travelling furnace ISO 11907-4:1998 Plastics - Smoke g e n e r a t i o n - D e t e r m i n a t i o n of the corrosivity of fire effluents - Part 4: D y n a m i c decomposition m e t h o d using a conical radiant heater 163

Thermosets and Composites

ISO 13774:1998 Rubber and plastics hoses for fuels for internalcombustion engines - Method of test for flammability 3.2.8

Optical properties

ISO 1600:1990 Plastics - Cellulose acetate - Determination of light absorption on moulded specimens produced using different periods of heating ISO 13468-1:1996 P l a s t i c s - Determination of the total luminous transmittance of transparent m a t e r i a l s - Part 1: Single-beam instrument ISO 13468-2:1999 P l a s t i c s - Determination of the total luminous transmittance of transparent m a t e r i a l s - Part 2: Double-beam instrument ISO 14782:1999 Plastics - Determination of haze for transparent materials

3.3 Material selection The first step is to prescribe specifications in an objective way: 9 An undervaluation of the constraints leads to problems during the use. 9 An overvaluation involves an overcharge due to the selection of materials that are too powerful and expensive, and due to part oversizing. The following factors, among others, must be examined: 9 Targeted lifespan, end of life criteria. 9 Temperature: extremes and average. 9 Environment: outdoor exposure, light, moisture, ozone, corrosion, radiations... 9 Physical properties: transparency, thermal and electrical conductivity, gas permeability, tribological properties... 9 Mechanical properties: instantaneous, permanent or cyclic stresses, impact... 9 Chemical properties: risks of polymer corrosion, risks of environmental pollution by the plastic, food contact, desorption of the ingredients in the space vacuum, pollution of chemical and electrochemical baths, migration... 9 Electrical properties: influence of moisture, temperature and ageing. 9 Dimensional tolerances. 9 Weight. 9 Price: does not only have to be considered per kilogram, but also according to the fundamental properties. The total cost at the end of the lifetime, taking account of the expenses of assembly, maintenance, etc., is the true element of judgement. It is necessary to remember that the combination of several factors often has a synergistic effect: a plastic resistant to a chemical in the absence of mechanical stress and at ambient temperature can quickly crack under load and be more or less quickly degraded in the event of a temperature rise. 164

Basic criteria f o r the selection o f t h e r m o s e t s

Once the specification is established, a first pre-selection of the materials having the required minimal properties can be made using the graphs. For the selected polymer families, one will then refer to the corresponding monographs to determine those that satisfy all the points of the specifications. It is imperative that the final selection is made with the assistance o f a polymer specialist.

3.4 Precision of the moulded parts Plastics are different because of their morphology, structure, rheology, etc. The geometry of a part and the complexity of the corresponding mould vary. Consequently, the tolerances of a part depend on: 9 Polymer type. 9 Part geometry. 9 Processing concerns. 9 Acceptable cost. For example, the NF T 58000 standard classifies: 9 The various plastic families into five categories according to the expected precision of the dimensions. 9 In each plastic category, there are four classes of precision: o Normal tolerances: normal checking of the processing and other means. o Reduced tolerances: rigorous checking of the processing and other means. o Precision tolerances: reinforced checking, use of special machines and tools, skilled workers, selection of the parts. o Exceptional precision tolerances. The costs increase with the required precision. Table 3.2, as an example, shows the tolerances for parts of 10, 100 and 1000 mm length for the "normal" and "precision" classes. The same standard also fixes the tolerances for: 9 Angles, skins, ovalizations, ejection marks... 9 Shrink marks (for thermoplastics). Table 3.2

Examples of part tolerances for normal and precision classes Size

Tolerance class N o r m a l Precision

mm

Filled or neat ABS, amorphous PA, PC, PESU, amorphous PET, PMMA, PPO, PS, PSU, rigid PVC, SB, SAN. Filled PA 6, 66, 6/10, 11, 12; PBTP, PETP, POM, PPS.

+ mm

+ mm

10

0.20

0.07

100

0.50

0.20

1000

2.90

1.25 165

Thermosets and Composites

Table 3.2

Examples of part tolerances for normal and precision classes Size

Tolerance class N o r m a l Precision

mm

Mineral filled EP, MF, PF, UP.

Neat CA, CAB, CAP, PA 6, 66, 6/10, 11, 12; crystalline PBTP, PETP; POM (<150 mm), EPDM modified PP. Filled ETFE, PP, plasticized PVC Shore D>50. High hardness TPE: PEBA, COPE, TPU. Filled PF and MF, prepregs.

Neat ETFE, FEP, PE, PFA, PP, plasticized PVC Shore D<50.

TPE hardness Shore D<50.

+ mm

+ mm

10

0.20

0.07

100

0.50

0.20

1000

2.90

1.30

10

0.20

0.09

100

0.60

0.29

1000

4.40

1.90

10

0.20

0.09

100

0.60

0.29

1000

4.40

1.90

10

0.20

0.11

100

0.87

0.41

1000

6.50

2.90

3.5 Schematic comparison of thermoset and composite properties The following graphs and tables make it possible to visualize quickly some significant characteristics and to roughly position certain thermosets and composites with respect to each other. The goal is only to make a first, very approximate pre-rating. The reader must then consult the detailed monographs: 9 To check the information whose graphical display may involve errors and approximations 9 To seek results on other families and other grades that do not appear in the graphs for lack of space. It must be recalled that: 9 The visualized values for the unidirectional composites are those of the most favourable direction. 9 The procedures applied to thermosets are sometimes non-standard and this can affect the results recorded to some degree. 9 The indicated values are often examples that are not representative of the whole of the subfamily and are given purely as an indication. 9 In certain cases, the subfamily and commercial names of the grades specify only the reinforcement or the principal filler whereas a secondary filler may be present in significant quantities and can influence the characteristics in a surprising way at first sight if one forgets this detail (this is the case for the SMC, filled phenolic resins...). 166

Basic criteria for the selection of thermosets

9

The thermosets are very often used with reinforcements. Some of them considerably modify the properties. It will be necessary to be careful with the interpretation of the following graphs and to allot the property share to each component, matrix or reinforcement. Table 3.3 relating to the various glass fibre reinforced unsaturated polyesters clearly shows the importance of the reinforcement. 9 Lastly, be careful with the scales used as some are logarithmic. Let us reminder ourselves that the goal of the following figures is only to make a first, very approximate, pre-rating. Table 3.3

Mechanical property examples for different glass reinforcements

Tensile strength (MPa)

Impact resistance

Premix

20-140

1-25

SMC

50-150

7-22

Mat

60-200

20-100

Fabric

170-270

100-190

UD profile

400-1000

Examples of transparent or very translucent thermosets Some thermosets are used in their transparent or very translucent forms: 9 Usually as unsaturated polyesters for sheeting. 9 More rarely used are: polyurethanes, epoxies, silicones.

Examples of Poisson's ratios Poisson's ratios depend on: 9 The thermoset chemical composition. 9 The reinforcements. 9 The testing direction with regard to the reinforcements. For example, for a carbon fibre reinforced epoxy the values are 0.27 to 0.34 in the fibre direction and 0.8 to 0.9 in the perpendicular direction. 9 The temperature. Table 3.4 shows some examples of Poisson's ratios. Table 3.4

Some examples of Poisson's ratio

UP/GF

0.24

Alkyd resin

0.17

Diallyl phthalate

0.27

Phenolic resin EP/CF UD

0.20-0.24 Fibre direction Perpendicular direction

0.27-0.34 0.8-0.9

PI neat

0.4

PI/GF moulding

0.4 167

Thermosets and Composites

Silicone H V R Silicone resin Fluorosilicone PI glass fabric PI/CF PI/GF moulding PI neat Silicone RTV EP/GF SMC EP/CF UD EP/aramid fibre UD EP glass fabric Silicone foam Cy neat

n

PF/GF moulding EP filled, moulding PF/GF SMC UP filled, moulding PF organic filled UP/GF mat UP/GF BMC UP SMC MF filled EP neat UP cast MF modified P U R Sh A PUR Sh D PUR RIM

II

PUR foam UF cellulose

II

16o Figure 3.2.

168

260 oC

Continuous use temperature examples, ~

3oo

Basic criteria for the selection of thermosets

PI/GF moulding

m

PI neat EP/CF UD EP/GF SMC PF/GF SMC PI/CF

m

EP/aramid fibre UD

m

EP glass fabric PF/GF moulding UP SMC MF filled UP/GF mat UP/GF BMC EP filled, moulding UP filled, moulding MF modified PF organic filled PUR SRRIM UF cellulose EP neat UP cast PUR RIM PUR Sh D

|

PUR Sh A

|

Silicone H V R

m

PUR foam

m

Fluorosilicone

m

Silicone RTV

m

Silicone foam

o

16o

2oo

3oo

460

~ Figure 3.3. H D T A examples, ~ 169

Thermosets and Composites

m

PI glass fabric UP glass roving

m

EP glass fabric

m

Silicone resin U P / G F BMC

m

U P / G F SMC UD MF filled UP SMC 10/50 GF PF/GF moulding UP filled, moulding P I / G F moulding

m

PF/GF SMC MF modified EP filled, moulding UP glass fabric

m

EP/CF U D PF moulding UP/GF mat

m

UF cellulose

m

PI/CF PI neat

m

Silicone H V R m

PF organic filled

m

UP/GF SMC foamed

m

Fluorosilicone

m

EP/Aramid fibre U D

P U R Sh D

UP cast Silicone RTV EP neat P U R Sh A Cy neat

m

PUR RIM EP foamed PUR SRRIM Silicone foam P U R foam

m

0

1

g/cm 3

Figure 3.4. Density examples, g/cm 3 170

Basic criteria for the selection of thermosets

EP/CF U D

I I

Pi/CV U p

UP/CF fabric EP/GF fabric or roving

I

EP/CF SMC

I

PI/CF

I

EP/GF SMC UP/GF SMC U D

I

PF/GF SMC PI/GF moulding PI neat

I

UP/GF SMC 35/50 GF UP/GF SMC 10/30 GF

I

MF modified EP foamed EP neat EP filled, moulding MF filled

I

UP/GF SMC foamed

I

UP filled, moulding

I

PI glass fabric PF filled UP cast

I

UF cellulose

I

PF moulding

I

Silicone resin P U R RIM P U R cast P U R structural foam Silicone H V R Silicone RTV

I

Fluorosilicone !

100

0.01

Figure 3.5.

MPa

, P U R foam 10000

Tensile strength examples, MPa 171

Thermosets and Composites

PUR Sh A Silicone H V R Silicone RTV Fluorosilicone PUR foam PUR Sh D Silicone foam PUR RIM UP cast EP neat UP filled, moulding PUR SRRIM PI neat Cy neat UP/GF BMC UP aramid EP filled, moulding PF organic filled UP/GF SMC UD

m

UP/GF mat UP glass fabric UP CF fabric

n

UP SMC 10/30 GF UP glass roving EP/GF SMC EP/Aramid fibre UD EP glass fabric PI/CF EP/CF UD MF filled UP SMC 35/50 GF UF cellulose PI/GF moulding PF/GF moulding PF moulding MF modified 0.1

Figure 3.6. 172

i

i

10

1000 %

Elongation at break examples %

Basic criteria for the selection of thermosets

i

EP/CF U D EP/CF SMC

m m

EP/GF SMC U P / G F Fabric or roving

i

PI/CF

m

UP SMC PUR SRRIM

i

PI/GF moulding

i

U P / G F mat

i

PF/GF SMC PI neat PF/GF moulding MF filled

i

EP neat EP foamed

l

Cy neat EP filled, moulding

i

UP filled, moulding MF modified UP cast

I

UF cellulose UP/GF BMC

I

PI/GF fabric PF organic filled P U R RIM P U R Sh A Silicone H V R P U R foam Fluorosilicone Silicone RTV Silicone foam

io

10'00 MPa

Figure 3. 7. Flexural strength examples, MPa 173

Thermosets and Composites

m

EP/CF UD EP/aramid fibre UD EP glass fabric UP/CF fabric

I m m m

PI/CF EP/GF SMC UP/GF SMC UD UP/GF roving or fabric MF filled

m m

UP SMC 35/50 GF

m

PF/GF moulding UP SMC 10/30 GF

m m

PI/GF moulding EP filled, moulding MF modified

m

PUR SRRIM UP/GF SMC foamed

m

UP/GF mat

m

UP/GF BMC UF cellulose

m

PF/GF SMC

m

PF organic filled UP filled, moulding PI neat EP foamed

m

PI glass fabric UP cast

m

Cy neat EP neat P U R Sh D P U R RIM P U R structural foam PUR Sh A Silicone H V R Silicone RTV P U R foam Fluorosilicone Silicone foam

mm !

0.0

m

0.1

10.0

GPa

Figure 3.8. Flexural Modulus examples, GPa 174

1000.0

Basic criteria for the selection of thermosets

m

EP/CF U D

I

P F / G F moulding

I

MF filled

m

EP/CF SMC

l

U F cellulose

l

PF organic filled

I

PI/CF

II

MF modified

II

U P / G F fabric or roving PI neat

n

PI/GF moulding

II

E P / G F SMC

n

U P / G F mat

n

UP cast

I

UP filled, moulding

i

PI/GF fabric

n

PUR RIM P U R structural foam

//

EP foamed

m

P U R foam !

i

1000

10 MPa

Figure 3.9.

Compression strength examples, MPa 175

Thermosets and Composites

EP/GF SMC

II

UP/GF mat PUR SRRIM EP/CF SMC

II

UP/CF fabric PI/GF fabric UP/GF SMC UP/aramid fibre PF/GF moulding MF filled PI/GF moulding UP/GF BMC P U R RIM UP cast EP toughened

m

EP/GF moulding PI/CF PF organic filled PI neat

m

MF modified

II

UP filled, moulding EP syntactic foam

m i

10

!

!

i

100

1000

10000

Index

Figure 3.10. 176

Notched impact strength examples, Index without unit

Basic criteria for the selection of thermosets

120

100

~ I ~

i/GF ~GF

F

60

20-

0 50

|

i

i

i

100

150

200

250

~

Figure 3.11.

Heat modulus retention examples, % 177

Thermosets and Composites

Figure 3.12. Fatigue examples, Index without unit versus cycle numbers 178

Basic criteria for the selection of thermosets

Silicone resin Silicone H V R PI neat PI/GF moulding

m

EP neat

m

EP filled, moulding PUR RIM PUR foam

l

PI moulding

I

UP cast

I

Silicone RTV

m

PUR U P / G F BMC

l

Fluorosilicone UPSMC

m l

UP filled, moulding

m

UF cellulose Silicone foam MF filled

m

PF organic filled

m m

MF modified

m

PF/GF moulding PI graphite UP antistatic EP Aluminium powder

i

i

1

10

i

IO0

log(resistivity) Figure 3.13. Resistivity examples, loglo(ohm cm) 179

Thermosets and Composites

PUR

m

UP cast

II

Silicone HVR

II

MF modified

m

Silicone resin

m

PF/GF moulding

m

MF filled EP neat PF organic filled

m

PI/GF moulding

m

PI neat

II

Fluorosilicone

m

Silicone RTV

m

EP filled, moulding

m

PI moulding

II

UF cellulose

II

UP/GF BMC

II

UP SMC PI graphite EP Aluminium powder

m

Silicone foam

m !

1

UP antistatic !

i

i

10

100

1000

kV/mm

Figure 3.14. 180

Dielectric rigidity examples, k V/mm

Basic criteria for the selection of thermosets

MF modified PF/GF moulding PF organic filled MF filled

m

EP Aluminium powder

m

UF cellulose UP cast EP filled, moulding PUR EP neat PI/GF moulding PI moulding Silicone foam Silicone RTV PI graphite Silicone H V R

II

Fluorosilicone

I/

PI neat

m

Figure 3.15.

Silicone resin

!

i

10

1000

IE-4

Dielectric loss factor examples, 10 --4

181

Chapter 4

Detailed accounts of thermoset resins for moulding and composite matrices

Thermosets and Composites

For easier reading, certain elements of earlier chapters are repeated in the opening remarks on each material family and in the sections on "Applications". However, for the latter the reader should refer to Chapter 2 for the most complete and up-to-date information. Unless otherwise specified, the units used in the property tables at the end of each account are: g/cm 3 Specific mass or density % Shrinkage Absorption of water % after 24 h of immersion Tensile strength MPa % Elongation at break Tensile modulus GPa Flexural strength MPa Flexural modulus GPa Compression strength MPa Notched impact strength ASTM D256 J/m oC H D T B (0.46 MPa) oC H D T A (1.8 Mea) o C Continuous use temperature o C Glass transition temperature oC Brittle point Thermal conductivity W/m.K Specific heat cal/g/~ 10-5/oc Coefficient of thermal expansion Volume resistivity ohm.cm 10-4 Loss factor Dielectric strength kV/mm Arc resistance S

4.1 Polyurethanes, polyureas (PUR) Polyurethanes are obtained by the reaction between polyols and isocyanates. They are of diverse chemical natures and applications. Polyols can be polyester or polyether types, the formulation is highly versatile, the polyurethanes can be hot or cold crosslinked and one- or two-shot processed. They yield soft or hard solid parts, or foams of greater or lesser density, which may be soft, rigid or microcellular. Consequently, the properties vary significantly according to the grades and final morphologies and structures. Some have a rigidity of the same order as ABS, whereas others are very flexible foams. Generally, compared with polyethers, the polyesters present: 9 The best hydrocarbon behaviour. 9 A greater sensitivity to water and hydrolysis. 184

Detailed accounts of thermoset resinsfor moulding and composite matrices

9

A more limited resistance to ageing with some exceptions, as we see in Section 4.1.2. Polyureas, obtained by the reaction of amines and isocyanates, also cover the whole range of hardnesses and are, generally, more resistant to water. Unless otherwise specified we will not make a distinction between the various subfamilies. Only the foams will be given special attention as they present particular properties due to their morphology: 9 Decrease in the mechanical properties due to the low quantity of polymer and the high proportion of gas. 9 Weaker chemical resistance due to the highly divided state of the polymer. The thin cell walls immediately absorb liquids and gases. Millable rubbers and TPU are not treated here. 4.1.1 General properties Advantages

A broad range of moduli from very flexible to rigid materials, liquid state of suitable grades, ease and diversity of the processing methods, ability to manufacture rigid or flexible foams, attractive price/property ratios, fair oil and fuel behaviours, fair or good mechanical and thermal resistances for suitable grades, possibilities of transparency and fireproofing. Drawbacks

Sensitivity of the polyester types in particular to hydrolysis, acids and bases, sometimes limited resistance to ageing, natural combustibility, limited continuous use temperature for some grades, rather slow processing. Special grades

Flexible, coatings, resistant, resistant,

rigid, cold or hot castable, RIM, SRIM, flexible or rigid foams, electric applications, fireproofed, high performances, heat improved light and hydrolysis stabilities, transparent, chemical low temperature uses.

Cost

The costs are, generally, of the order of ~3-12 per kilogram. Processing

Casting, coating, encapsulation, impregnation, foam, spraying, RIM, SRIM, putting, centrifugation. Applications [see Chapter 2 for further information]

Consumption Polyurethane consumption represents 4% of the total plastic consumption or 31% of the total for thermosets. It grows at roughly the same rate as for plastics as a whole. Identified US consumption is divided 185

Thermosets and Composites

into 52% for flexible foams, 35% for rigid foams and 13% for the RIM and elastomers. Polyureas represent a small share of polyurethanes and are not indexed in the statistics. Examples of operational or development parts are listed below. Foam application examples

Furniture: mattresses, pillows, cushions, seats, backrests, armrests, seats with structural skin, decorative elements, parts in polyurethane rigid foam. Automotive, railway, shipbuilding and other transportation: comfort, damping and protection; seats, backrests and headrests, safety padding of instrument panels or sun visors, steering wheels (possibly combined with airbag door), saddles of two-wheelers, energy absorbing bumpers, soundproofing, carpet underlays, rigid foams for thermal insulation, door fillings. Building and civil engineering: thermal insulation, soundproofing; heat insulation of roofs, walls, ceilings, floors, sandwich panels, refrigerating pipes, cold stores, district heating pipes, oil tanks and pipelines. Packaging: Flakes, chips, sheets, blocks are used for impact protection and damping in the packaging of various products such as cameras, electronic devices. Industry: Machine soundproofing, impact and vibration damping. Appliance: Thermal insulation of refrigerators, freezers and other refrigerating furniture; phonic, mechanical and thermal isolation; antistatic foams for electronics packaging. Sports and leisure: Gym mats, balls, stuffing of rucksacks in foam-coated textile; soles for town or leisure shoes, ski boots, hockey; slippers for ski boots. Miscellaneous: Sponges for cosmetics, paramedical, or domestic uses; textile and clothing applications; paint rollers, polishing discs; elastic belts for disposable nappies; air filtration, phonic damping, front panels of loudspeakers, lining of heavy masses. RIM application examples

Automotive and transport: fenders, roofs, sliding sunroofs, spoilers, bumper skirts for niche or medium output light vehicles or trucks; aircraft interior elements. Building and civil engineering: Points of fence piles. Packaging: Structural packaging. Industry: Frames, formworks, hoods, panels, casings for machines; cases of humidifiers and control monitors; models, prototypes of mass production thermoplastic parts. Appliances: Computer and video consoles; cases, hoods, housing, bodies of office machines, television sets, computers, cash registers. Furniture: Structures of seats and other furniture. 186

Detailed accounts of thermoset resins for moulding and composite matrices

Shipbuilding: Paddles, boat interior elements. Sports and leisure: Scale models, elements of structure and panels ofjukeboxes. Elastomer application examples Automotive and transport: oil/gas separating membranes for shock absorbers, hydropneumatic suspensions, frame supports for 4WD, various bearings. Building and civil engineering: bushings for low-power tracked excavators, blades or scrapers for snowplough, plates of polyurethane elastomer for gravel screens. Electricity & electronics: telephone wire insulation, encapsulation of components. Anti-abrasion: coatings; roller and cylinder coverings for paper and steel industries; linings of pump stators; solid tyres for fork-lift trucks; coverings for travelling wheels of conveyors, escalators, pulleys; guides for cables; anti-abrasion coatings and coverings for conveyors, pipes, sandblaster cabins, tanks of dump trucks for bulk transport, endless screws; bearings for looms; fire hose coating; elastic stamping cushions. Industry: couplings with teeth, plates or pins; conveying belts, driving belts; hydraulic seals, bellows; flue brushes for pipelines; grinding stones, discs for polishing; bearings, crane thrusts and travelling cranes. Shipbuilding: flexible coatings, coated fabrics for inflatable dinghies and lifeboats. Sports and leisure: coated fabrics for waterproofed sports clothes; handles of ski sticks, wheels of roller skates, soles of basic ski boots. Coatings and sealing application examples Automotive and transport: paints and coatings for cars and planes in polyurethane or polyurea. Building and civil engineering: liquid polyurethane for waterproofing coatings for terraces, settling tanks, balconies, car parks, roofs, tunnels; polyurethane cements for liquid seals for terraces, communal kitchens; splashed polyurethane coatings for building rehabilitation. Polyurea Automotive & transport: paints and coatings for cars and aircraft, toothed belts in Kevlar reinforced polyurea, body panels, doors, fenders in polyurea RIM. 4.1.2 Thermal behaviour The continuous use temperature in an unstressed state, as indicated by the producers, generally varies from 80 ~ to 130 ~ 187

Thermosets and Composites

The UL temperature indices of specific grades ranges from 70 ~ (or even 50 ~ to 120 ~ for the electrical and mechanical properties, excluding impact. After a long ageing time, 1800 hours at 70 ~ the polyether-based type performs better than that based on polyester: 9 Tensile strength retention: polyether 25 %, polyester 5 % 9 Elongation at break retention: polyether 95%, polyester 0%. On the other hand, Figures 4.1 and 4.2 show the property retentions of two polyurethane elastomers after ageing for 7 days at air temperatures of 50 ~ up to 150 ~ In this case, the polyester type performs better than the polyether type. These results relate to four grades only and cannot be generalized. At low temperatures, the behaviour can be acceptable down t o - 5 5 ~ or even less.

Figure 4.1. Polyurethane: Ageing for 7 days. Tensile strength retention versus temperature of ageing

Figure 4.2. Polyurethane: Ageing for 7 days. Elongation at break retention versus temperature of ageing 188

Detailed accounts of thermoset resins for moulding and composite matrices

For the same elastomer grades as above: 9 The brittle points vary f r o m - 7 0 ~ t o - 3 8 ~ 9 The glass temperature by DSC measurements f r o m - 5 5 ~ t o - 2 2 ~ 9 The glass t e m p e r a t u r e by D T M A m e a s u r e m e n t s f r o m - 3 1 ~ to -14 ~ These results relate to two grades only and cannot be generalized. 4.1.3 Optical properties

Transparent grades are marketed. The refractive indexes, for specific grades, range from 1.5 to 1.6. 4.1.4 Mechanical properties

The mechanical properties are generally good: tensile strength, high tear and abrasion resistances. However, some grades have more limited characteristics. Rigidities and hardnesses are extremely variable, allowing a vast choice from high flexibility to the rigidity of ABS. The abrasion resistance of polyurethane makes it a first-class material for anti-wear parts and coatings. Creep

Although for thermosetting resins creep behaviour is variable, it should not be forgotten that many grades have very low moduli that involve high strains for moderate loading. Compression set

Despite their crosslinking, the compression set of the polyurethane elastomers is often rather high. For example, after 24 hours of compression, the compression sets of soft polyurethane elastomers are in the ranges: 9 From 5% to 40% at 70 ~ 9 From 12% to 78% at 100 ~ 9 From 54% to 100% at 140 ~ These results relate to a few grades only and cannot be generalized. 4.1.5 Ageing Dynamic fatigue

The dynamic fatigue strength can be fair or good for certain grades if one takes care to limit the strains by restricting the stresses to values in connection with the low modulus. Weathering

Some grades can be sensitive to light and hydrolysis and will behave more or less well in climates with strong sun and/or high moisture. The 189

Thermosets and Composites

mechanical properties decrease and the white or clear grades turn yellow or brown. U V and hydrolysis stabilization provide additional protection. Chemicals

Resistance to moisture and hot water is often limited. Figure 4.3 displays examples of tensile strength curves versus the immersion time in hot water. The superiority of the selected polyether is more obvious as the temperature rises.

45

0

40

......

..~ ......

35

"-~_ "~

-"O-v

30

-_ ether 50~

- - -"(3

25

15

~

10

~

- -0-

- ester 50~

-~

ether 70~

- -[-'! - - ester 70~

I-I

5

~

o o

Figure 4.3.

,

"'O

,

,

,

2

4

6

8

10

...

,

weeks

12

Polyurethane: examples of tensile strength retention versus immersion time in hot water

These results relate to two grades only and cannot be generalized. Acids and bases accelerate hydrolysis. Behaviour with organic chemicals is generally acceptable: resistance to oils and gasoline allows use in the automotive industry. Table 4.1 displays examples of property variations after immersion of elastomeric polyurethane in ASTM C fuel for 72 hours at 50 ~ These results relate to two grades only and cannot be generalized. T a b l e 4.1

P o l y u r e t h a n e s : e x a m p l e s o f p r o p e r t y variations after i m m e r s i o n in A S T M C fuel for 72 h

at 50~

Ester type

Ether type

T e n s i l e strength r e t e n t i o n , %

52

31

E l o n g a t i o n at b r e a k r e t e n t i o n , %

65

35

S h o r e A h a r d n e s s variation, S h A

-11

-15

48

88

Swelling, %

Table 4.2 gives some general indications that would have to be verified by consultation with the producer of the selected grades and by tests under operating conditions. 190

Detailed accounts of thermoset resins for moulding and composite matrices Table 4.2

Polyurethanes: chemical behaviour

Chemicals Acetic acid

Concentration

Temperature,~

Ester

Ether

50%

50

n

1

100%

20

1

n

Acid for battery

Unknown

20

n

n

Amines

Unknown

Acetone

A m m o n i u m hydroxide Aniline Bases Benzene

20

n

n

10%

20

n

1

100%

20

n

n

Unknown

20

n

1 to n

100%

20

n

n

Butane

100%

20

S

S

Butanol

100%

50

1

n

C a r b o n disulphide

100%

20

1

n

C a r b o n tetrachloride

100%

20

1

1

Unknown

20

n

1

Chlorine water Dibutylether

100%

20

1

1

Dibutylphthalate

100%

20

1

1

Dibutylsebacate

100%

20

n

n

Dichloroethane

100%

20

1

Dichloroethane

100%

50

n

Diethyleneglycol

100%

20

1

Diethyleneglycol

100%

100

n

1

Diethylether

100%

20

1

1

Dioctylphthalate

100%

100

S

S

96%

50

1

Unknown

93

n

n

Solution

20

n

n

37%

20

n

n

Freon

100%

20

S to n

S to n

Fuel A S T M B

100%

20

S

1

Fuel A S T M C

Ethanol Ethylene glycol Formic acid Formaldehyde

100%

20

1

1

Hydrochloric acid

20%

50

n

1

Hydrochloric acid

36%

20

n

n

H y d r o g e n peroxide

30%

20

1

1

Isooctane

100 %

20

S

S

Isopropanol

100%

50

1

191

Thermosets and Composites

Table 4.2

Polyurethanes: chemical behaviour

Chemicals

Concentration

Temperature,~

Ester

Ether

1

1 n

Kerosene

100%

50

M e t h y l ethyl k e t o n e

100%

20

1

Mineral oil

100%

20

S

Naphta

100%

50

l

Unknown

20

1

1

10%

50

n

n

100%

100

S

S

Oil A S T M 3

100%

100

S

1

Oil for t r a n s f o r m e r

100%

20

S

S

50%

20

S

S

Perchloroethylene

100%

20

1

n

Petrol

100%

20

S

1

Natural gas Nitric acid Oil A S T M i or 2

O z o n e 50 p p h m

Petrol spirit

100%

20

S

S

Unknown

20

n

n

60%

50

n

n

Potassium hydroxide

Solution

20

n

n

Potassium p e r m a n g a n a t e

Solution

20

n

n

Propane

100%

20

1

1

Pydraul f9

Phenol Phosphoric acid

100%

20

n

n

Sodium hydroxide

10%

60

S

S

Sodium hydroxide

10%

90

n

n

Conc

Hot

n

n

20%

20

n

n

Tetrachlorethane

100%

20

1

n

Tetrachloroethylene

100%

20

n

n

Toluene

100%

20

1

n

Trichloroethylene

100%

20

n

n

Trichloroethane

100%

20

1

n

Vapour

100%

100

n

n

V e g e t a b l e oil

100%

20

S

S

W h i t e spirit

100%

20

S

Xylene

100%

50

1

Strong oxidizing acids Sulphuric acid

S: satisfactory; 1: limited; n: n o t s a t i s f a c t o r y Conc: c o n c e n t r a t e d s o l u t i o n

192

Detailed accounts of thermoset resins for moulding and composite matrices

Fire resistance

Fire resistance is naturally weak but can be improved to reach the VO rating for certain foams. 4.1.6 Electrical properties Special grades are proposed for electrical applications such as the insulation of printed circuits, wires and cables and component encapsulation. Moisture absorption can cause resistivity to fall appreciably.

4. f .7 Joining

Welding is useless as for all the thermoset resins. Only adhesives chosen following rigorous tests are permitted for joining. The parts should not be subjected to high stresses. Primer applications allow good adherence to metals. Foams Unlike industrial solid polymers, which are processed as carefully as possible to avoid the formation of bubbles, vacuoles etc., alveolar materials result from the desire to introduce, in a controlled way, a certain proportion of voids with the aim of: 9 Increasing flexibility: very soft seals. 9 Improving the thermal or phonic insulating character: foams for building. 9 Making damping parts: foams for packaging, automotive and transport safety parts. 9 Reducing material weight while preserving the structural properties: lightweight automotive or industry parts. 9 Producing greater or lesser permeability to liquids and gases: filters, absorbing sponges... The alveolar materials consist of a polymer skeleton surrounding the cells, which may be closed or partially or completely open to neighbouring cells or the outside. The intrinsic properties come from those of the polyurethane with: 9 A reduction in the mechanical properties due to the small quantity of material and the strong proportion of gas. 9 A reduction in the chemical behaviour due to the highly divided nature of the material. The thin cell walls immediately absorb liquids and gas and are rapidly damaged. Figure 4.4 plots the tensile strength versus the density for various polyurethanes of various subfamilies from very light foams to fully dense materials. These results relate to only a few grades and cannot be generalized. 4.1.8

193

Thermosets and Composites

Figure 4.4. Examples of polyurethane foams: tensile strength versus density

The polyurethanes are used for the manufacture of all the types of foams: 9 Flexible, semi-rigid, rigid. 9 With closed or open cells. 9 For damping, insulation, filtration, absorption. 9 With integral skin: foam whose non-alveolar skin was completely preserved. 9 Structural: foam whose mechanical properties are sufficient to enable it to durably ensure the solidity of the part or to contribute to the resistance of the unit in which it is integrated. 9 Structural with integral skin. 9 Reinforced with mineral or glass fibres. Compared with polyether foams, polyester foams generally present: 9 A better mechanical resistance. 9 The best behaviour with hydrocarbons. 9 A greater sensitivity to water and hydrolysis. 9 A better soundproofing ability. 9 A better damping capacity. 9 A more limited resistance to ageing. Rigid foams have a glass transition temperature above 20 ~ whereas flexible foams have a glass transition temperature below the ambient temperature, which explains their flexibility. Polyureas are used for the manufacture of flexible and rigid foams as well as structural foams by reaction-injection (RIM). They have better water resistance than polyurethanes. Integral skin foams The core is microcellular and the skin is dense. Moulding makes it possible to obtain technical parts: 9 With complex shapes. o With 5-30 mm thickness walls. 9 Integrating reinforcements or inserts. 194

Detailed accounts of thermoset resins for moulding and composite matrices

Structural foamed polyurethane Table 4.3 shows characteristic examples of foam and dense polyurethane: the flexural modulus ratios are of the same order, but the tensile ratios are lower for the foamed material. However, for a moderate density decrease, the polyurethane can work as a structural material. Table 4.3

Characteristic examples of structural foams and dense polyurethanes

P UR properties Foamed Density, g/cm 3

Dense

Ratio ofproperty/density Foamed

Dense

0.6

1.1

1

1

Flexural modulus, GPa

0.950

1.5

1.6

1.4

Tensile strength, MPa

21

76

35

69

Elongation at break, %

7

10

Flexural strength, MPa

19

70

32

64

7

9

Coefficient of thermal expansion, 10-5/K

Rigid, semi-rigid a n d flexible foams

Foams of low density can be flexible or rigid, with open or closed cells. Rigid foams: with a majority of closed cells, rigid foams are obtained starting from polyethers. They have excellent heat insulation properties across a broad range of temperatures (-30 ~ to +70 ~ Semi-rigidfoams: the compression stresses are far lower than for the rigid foams. Flexible foams: with a majority of open cells, they are obtained starting from polyesters or from polyethers. Their densities are between 10 and 60 kg/m 3. They can have applications in furnishing or as cores of sandwich panels. Table 4.4 compares some characteristics of rigid, semi-rigid and flexible foams of the same density magnitude: 9 The stresses for 10% or 40% compression are very different according to the foam type. 9 The elongations at break range from a few percent to 400%. Table 4.4

Characteristic comparison of various polyurethane foams

Density, kg/nfl

30-50

50-70

Density, g/cnfl

O.030-0. 050

O.050-0. 070

0.140-0.300

0.300-0.600

0.200

0.400

0.022-0.027

0.029-0.035

Rigid foam 10% compression stress, MPa

Tensile strength, MPa Thermal conductivity, W/(m.K)

195

Thermosets and Composites Table 4.4

Characteristic comparison of various polyurethane foams

Semi-rigidfoam 40% compression stress, MPa

0.019-0.070

Tensile strength, MPa

0.160-0.180

Thermal conductivity, W/(m.K)

0.030

Elongation at break, %

60

Flexiblefoam 40% compression stress, MPa

0.003-0.004

Tensile strength, MPa

0.120--0.150

Elongation at break, %

110-400

Foams can be processed by secondary processing methods. According to the rigidity, the polyurethane foams can be: 9 Cut out with a saw (with or without teeth) or press stamped. 9 Drilled or milled. 9 Stuck with adhesives. 9 Thermoformed. Precautions for use

In certain countries, the materials used in furnishing, building, transport, etc. must satisfy fire standards or regulations that are not met by ordinary polyurethane grades. There are special fireproofed grades that may possibly meet these requirements. It is compulsory to check these grades according to local regulations. 4.1.9 Specific ISO standards concerning polyurethanes Raw materials

ISO/TR 9372:1993 Plastics- Basic materials for polyurethanes - Determination of the amounts of 2,4- and 2,6-isomers in toluenediisocyanate by infrared spectroscopy ISO 14896:2000 Plastics - Polyurethane raw materials - Determination of isocyanate content ISO 14897:2002 Plastics- Polyols for use in the production of polyurethane Determination of water content (available in English only) ISO 14898:1999 Plastics- Aromatic isocyanates for use in the production of polyurethane - Determination of acidity ISO 14899:2001 Plastics- Polyols for use in the production of polyurethane Determination of basicity ISO 14900:2001 Plastics- Polyols for use in the production of polyurethane Determination of hydroxyl number 196

Detailed accounts o f thermoset resins for moulding and composite matrices

ISO 17710:2002 Plastics- Polyols for use in the production of polyurethane Determination of degree of unsaturation by microtitration (available in English only) Applications

ISO 5423:1992 Moulded plastics footwear- Lined or unlined polyurethane boots for general industrial u s e - Specification ISO 5999:1982 Polymeric materials, cellular flexible- Polyurethane foam for load-bearing applications excluding carpet underlay- Specification ISO 6910:1992 Moulded plastics footwear- Lined or unlined polyurethane industrial boots with general-purpose resistance to animal fats and vegetable oils- Specification ISO 6915:1991 Flexible cellular polymeric materials- Polyurethane foam for laminate u s e - Specification ISO 7617-3:1988 Plastics-coated fabrics for upholstery- Part 3: Specification for polyurethane-coated woven fabrics ISO 8096-2:1989 Rubber- or plastics-coated fabrics for water-resistant clothing- Specification- Part 2: Polyurethane- and silicone elastomercoated fabrics ISO 8873:1987 Cellular plastics, rigid- Spray-applied polyurethane foam for thermal insulation of buildings- Specification 4.1.10 Trade name examples

Adiprene, Allrim, Baydur, Bayfill, Bayfit, Bayflex, Baymer, Baytec, Caradate, Caradol Chemothane, Desmodur, Desmopan, Dunlopillo, Eccoseal, Flexothanne, Instapack, Irathane, Isorob, Isothanne, Kapex, Napter, Rectipack, Rezolin, RIM T2L, Robetanche, Robfill, Robflex, Rutapur, Voranol, Witcothane 4.1.11 Property tables

Tables 4.5 to 4.11 relate to examples only and cannot be generalized. Table 4.5 Castable polyurethanes: property examples Hardness Process Density Shore

g/cm3

TS

EB

FM

Brittle point

HDTA

CUT

CS

MPa

%

GPa

~

~

~

%

Shrink Rebound %

%

Shore A grades 27A

C

1.05

30A

C

1.25

5-10 1

330

350

47A

C

1.05

6

1000

53A

C

1.2

58A

H

6

390

11

480

80

85 -70

8

80 197

Thermosets and Composites

Table 4.5

Castable polyurethanes: property examples

Hardness Process Shore 62A

Density g/cm3

H

TS

EB

FM

MPa

%

GPa

18

470

63A

C

1.05

7

700

63A

C

1.1

11

500

Brittle point

HD T A

CUT

~

~

~

-70

65A

C

1.3

5

225

80

C

1.34

5

170

110

77A

C

1.1

14

600

80A

C

1.1

14

400

20

800

1.3

24

300

30

580

9

50

80A

H C

83A

H

85A

C

1.36

90A

H

31

450

92A

H

37

380

94A

H

27

290

95A

H

34

400

48D

H

34

400

Shrink Rebound

%

%

45

70A

83A

CS

% 86

0.3 0.2

-90

45

50

35

45

130 -70 130 -70

27

40

31

40

69 -70

40

40

40

40

Shore D grades -70

58D

H

57

320

40

62D

H

44

290

36

73D

H

60

210

77D

C

1.6

20

78D

C

1.1

38

82D

C

83D

C

1.2

85D

C

1.3

-60

1.5

40

45

5 2.6

50

65

0.4

50

0.3

55

0.4 80

0.5

Examples of electrical and thermal properties U L temperature index

~

50-85

Coefficient of thermal expansion

10-5/~

Resistivity, dry at 23 ~

ohm.cm

1012-1015

Resistivity, wet at 23 ~

ohm.cm

101~

Dielectric constant 50 Hz to 0.1 MHz

10-20

a2

2.3-7

Loss factor, 50 Hz to 0.1 MHz

10.4

100-600

Dielectric rigidity

kV/mm

15-140

C, H: Cold, H o t processing; TS: tensile strength; EB" elongation at break; FM: flexural modulus; CUT: continuous use t e m p e r a t u r e ; CS (compression set): 22 h at 70 ~ shrinkage; R e b o u n d : r e b o u n d resilience 198

Shrink: linear

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.6

RIM elastomer polyurethanes: examples of properties

Shore hardness Density, g/cm 3 Shrinkage, % Water absorption, 24 h, % Tensile strength, MPa Elongation at break, %

80 to 90 A

45 to 55 D

65 to 75 D

76D

1.1

1.04

1.04

1.1-1.13

1.2-1.4

0.85

0.8-0.9

13-16

16-25

26-29

40-50

300-360

200-250

80-150

9-14

3.3

60-77

Flexural strength, MPa Flexural modulus, GPa

0.03-0.07

0.1-0.4

0.6-1

1.4-2 35

Compression strength, MPa 675

Notched impact, J/m

243-648

49

HDT A (1.8 MPa), ~

<37-90

HDT B (0.46 MPa), ~

37-115

UL temperature index, ~

75-85

Coefficient thermal expansion, 10-5/~

5-6

6-8

6

9

Resistivity, ohm.cm

1014-1015

Dielectric constant

3-3.5 V0 to 5VA

UL94 fire rating Reinforced grades 15% glassfibres

15-25% mineralfilled

1.14

1.15-1.26

Shrinkage, %

0.6-0.7

0.3-0.7

Shore hardness, D

60-70

60-64

Tensile strength, MPa

20-27

19-29

Elongation at break, %

75-200

96-150

Flexural modulus, GPa

0.7-1.2

0.9-1.5

Notched impact, J/m

160--430

150-243

Reinforcement Density, g/cm 3

Coefficient thermal expansion, 10-5/~

2.7

199

Thermosets and Composites

Table 4.7

RIM structural foam polyurethanes: examples of properties

Shore hardness, D

28-46

55-70

81

Density, g/cm 3

0.24-0.4

0.5-0.65

0.88 0.7-0.9

Shrinkage, % 4-9

14-22

Elongation at break, %

7

7-10

Flexural strength, MPa

6-14

23-39

63

Flexural modulus, GPa

0.2-0.5

0.7-1.2

1.6

3-8

14--31

42

70-85

100

Tensile strength, MPa

Compression strength, MPa HDT B (0.46 MPa), ~

33

4-5

Coefficient thermal expansion, 10-5/~ Resistivity, ohm.cm

1014--1015

Dielectric constant

2.7 V0 to 5VA

HB

UL94 fire rating

Examples of SRRIM: Structural reinforced RIM Glassfibres

15-20%

Shore hardness, D

43-50

Density, g/cm 3

0.4--0.6

Shrinkage, %

0.1-0.2

55-60%

1.6-1.7

Tensile strength, MPa

17-23

154-259

Elongation at break, %

2-11

1.8-2

Flexural strength, MPa

37-47

151-438

Flexural modulus, GPa

1.2-1.6

7-15

Notched impact, J/m

350

350-1600

HDT A (1.8 MPa), ~

80-98

213- >220

Coefficient thermal expansion, 10-5/~

0.8-1.5

0.8

200

Detailed accounts of thermoset resins for moulding and composite matrices Table 4.8 Rigid polyurethane foams: examples of properties Foamsfor energy absorption Density, kg/m 3

48

55

72

Density, g/cm 3

0.048

0.055

0.072

Water absorption, 24 h, %

25

2-18

9

Tensile strength, MPa

0.2

0.3

0.4

Compression stress at 10% strain, MPa

0.1

0.1-0.2

0.2

30

50

>70

0.14

0.3

0.6

80

100

120

Moisture permeability, (no unit)

1400

1100

900

Thermal conductivity, W/m.K

0.029

0.031

0.035

Foamsfor building insulation Density, kg/m 3 Compression stress at 10% strain, MPa Temperature for shrinkage <3%,~

Sprayed

Sheets Density, kg/m 3

30

Compression stress at 10% strain, MPa

0.100-0.150

0.200

Thermal conductivity, W/m.K

0.022-0.027

0.020-0.022

85

90

___5

___4

Closed cells, % Dimensional stability, 48 h at 70 ~

%

Table 4.9 Semi-rigid polyurethane foams: examples of properties Density, kg/m 3

21-30

80-100

130-160

Density, g/cm 3

0.02-0.03

0.08-0.1

0.13-0.16

Tensile strength, MPa

0.1-0.2

0.2-0.3

0.3

Elongation at break, %

35-60

50-54

35

0.01-0.04

0.04-0.05

Compression stress at 50% strain, MPa

201

Thermosets and Composites

Table 4.10 Flexible polyurethane foams: examples of properties Flexible foams for furnishing >_25

Density, kg/m3 Density, g/cm 3

0.025

Tensile strength, MPa

>0.075 >160

Elongation at break, % Compression set, 22 h, 70~

<8

90% strain, %

<5

Set after 250 000 cycles in compression, %

Harsh uses

Severe uses

Normal uses

Seats Examples

Tensile strength, MPa Elongation at break, % Compression set, 22 h, 70 ~

75 % strain, %

Tensile strength after 16 h at 140 ~ Tensile strength after 3 h at 105 ~

MPa 100% RH, MPa

Pillows

Public furniture or transport

Private furniture or automotive

Bedding

0.050

0.050

0.050

100

150

150

8

10-12

10-15

0.035

0.035

0.035

0.035

0.035

0.035

Flexible foams for automotive Density, kg/m3

I8-21

25-28

30-34

Density, g/cm3

0.020

0.027

0.032

Tensile strength, MPa

0.120

0.150

0.150

130

400

110

0.004

0.0025

0.006

Elongation at break, % Compression stress at 40% strain, MPa

General purpose flexible foams Density, kg/m3

27

48

0.027

0.048

Tensile strength, MPa

0.13--0.2

0.13-0.24

Elongation at break, %

110-140

105-155

Compression stress at 50% strain, MPa

0.04-0.05

Density, g/cm 3

202

Detailed accounts of thermoset resins for moulding and composite matrices Table 4.11 Polyurea properties: examples Reinforced orfilled rigid polyurea Reinforcement orfiller

20% glassfibres

20% glassflakes

Body elements Density, g/cm 3

15% glassfibres Bumpers

1.1-1.15

1.2

1.12

Tensile strength, MPa

30

33

22

Elongation at break, %

65

12

100

Flexural modulus, GPa

1.4-2

1.3-1.5

0.5-1

HDT A (1.8 MPa), ~

130-160

Coefficient of thermal expansion, 10-5/~

4-6

4-5

5-7

Front end Reinforcement orfiller

15% glassfibres

18% glassfibres

1.12

1.15

1.12

Tensile strength, MPa

18

22

42

Elongation at break, %

150

50

10

Flexural modulus, GPa

0.3-0.5

0.8-1.4

1.2-3

120

190

5

2-3

Density, g/cm 3

HDT, ~ Coefficient of thermal expansion, 10-5/~

7-9

15% carbonfibres

Neat polyurea Glazing encapsulation Density, g/cm 3 Shore hardness, D Tensile strength, MPa

1.05-1.1 50-55 17

Elongation at break, %

300-400

Flexural modulus, Gpa

0.05-0.1

Coefficient of thermal expansion, 10-5/~

14-15

4.2 Unsaturated polyesters (UP) Unsaturated polyesters are obtained by the reaction between di-acids or anhydrides containing a proportion of double bonds and a diol or glycol. The mixing of saturated and unsaturated acids, their type, the nature of the diols and the versatility of the recipes lead to diverse chemical natures: 9

Ortho or isophthalic acids with various types of alcohols,

9

Vinylesters, 203

Thermosets and Composites

9 Bisphenolics, 9 Diallylphthalates, etc. The processing conditions vary: 9 Hot or room-temperature curing 9 With or without post-cure. The unsaturated polyesters can be modified, for example with: 9 Melamines: UP/MF 9 Isocyanates... Consequently, the neat unsaturated polyester resins have varied properties that filling and reinforcement diversify even more to lead to a very broad range of characteristics and uses. Unless otherwise specified, the indications that follow relate to the most current types. The unsaturated polyesters are the first-class matrix for general-purpose, mass-produced composites with a good technical level, generally with glass fibre reinforcement: shipbuilding, automotive and railway bodies, anticorrosive, electricity, tanks, etc. Generally, compared to unsaturated polyesters, the vinylesters are: 9 More resistant to hydrolysis and a great number of chemicals. 9 More heat resistant. 9 More creep resistant. 9 Tougher and more resilient. 9 More expensive. 9 Less used. 4.2.1 General properties Advantages Attractive price/property ratios, good mechanical and electrical properties, fairly good heat and creep behaviours, aesthetics, choice of rigidities, resistance to a great number of chemicals, resistance to light, weathering and water in spite of surface deteriorations; possibilities of transparency and food contact for suitable grades, broad range of colours, ease of some manual processing methods, possibility of lightening by controlled foaming, suitability for the manufacture of very large composite parts (shipbuilding). Drawbacks

Natural flammability, significant shrinkage of the current grades, industrialization and reproducibility difficulties for some processes, limited behaviour to bases, acids and boiling water except for special grades; decomposition by oxidizing strong acids, attack by some solvents. Special grades Hand and spray lay-up moulding, impregnation, SMC, BMC, TMC, ZMC..., compression, injection, pultrusion, filament winding, centrifugation, long or 204

Detailed accounts of thermoset resins for moulding and composite matrices

short glass fibre reinforcement, for thin or thick parts, for shipbuilding, for gelcoat; more or less reactive, more or less thixotropic, food contact, foamed, controlled damping, low shrink, low profile, fireproofed, pre-accelerated, rigid, semi-rigid, flexible, high elongation at break, high or very high transparency, improved light or hydrolysis or heat stability, low emission of styrene or environment friendly, cold hardening, hot hardening, toughened, light colour, resistant to cracking... For casting, encapsulation, inclusion, cements, concretes, for large blocks, buttons, moulds. Vinylester grades for chemical and heat resistance. Cost The costs are generally of the order of: 9 Less than ~2 up to ~6 per kilogram for unsaturated polyester grades. 9 ~3 to ~8 per kilogram for vinylester grades. Processing Hand and spray lay-up moulding, compression, injection, transfer, SMC, BMC, TMC, ZMC..., RTM, infusion, pultrusion, filament winding, centrifugation, impregnation, casting, encapsulation, inclusion, machining, coating. Certain processes such as hand and spray lay-up moulding, inclusion, casting, encapsulation are manual. Applications [see Chapter 2 for further information]

Consumption Unsaturated polyester consumption in industrialized countries accounts for 13-21% of the total thermoset consumption and is approximately 2.7% of the total plastic consumption. According to the country, consumption has grown or declined slightly in the last few years. The main application markets are: 9 Building and civil engineering 9 Industry 9 Electrical engineering, consumer goods 9 Transport. Examples of operational or development parts are listed below.

Automotive 9 Bodies and parts, from mass production to small series or even a single unit: passenger cars, 4WD, monospaces, trucks and lorries, utilities, buses; sports, recreational, special vehicles; caravans, motorhomes... 9 Bodies of niche or medium output vehicles, body panels, rear floors, decklids, roofs, fenders, doors, inner doors, bonnets, tailgates, frontends for mass production vehicles, caps, trunk lids, bodies of sports 205

Thermosets and Composites

cars; roofs for vans; bumper beams and side protection of mass production vehicles; spring leafs for vans. 9 Particle filter systems, engine covers and sumps; supports of batteries; headlight reflecting housing. 9 Truck front panels, roof and side spoilers for truck cabins, engine hoods, front fenders; pickup truck boxes; shelters, ambulance cells, trailer or special vehicle bodies. 9 Cabins, cabin doors for farm tractors.

Building and civil engineering 9 Boarding for buildings, sloping roofs of petrol stations, modular roofs of stadiums, protection for industrial facilities, mobile guardrooms, external walls in sandwich panels, prefabricated houses, gables of dormer windows, pediments for building entrances, roofs and stained glass for churches, roof tiles. 9 Roofs and weatherboarding of agricultural or industrial buildings, sporting equipment, general-purpose rooms. Balconies, floors of balconies, parapets, cornices, colonnades, interior partitions for building restoration; architectural panels, profiles for doors and windows for factories, houses, buildings; exterior spotlight housings. Sinks and counter tops for kitchens. Fire-doors in fireproofed unsaturated polyester. Portals of gardens, translucent or opaque roofs, skylights in single or double wall sheets, shutters for factories, housings of waterproofed lights, industrial lighting cases; footbridges for maintenance of subway tunnels. Pedestrian bridge; 40 m bridge for pedestrian traffic, snow clearance motor devices and equipment up to 5 tonnes; bridge floor beams, elements of road toboggans, panels for soundproofing walls. External cabinets for automatic devices for traffic lights, telephone relays; cover plates of buried gas meter, roofs of rural shelters of bus stops; frames, formworks, cofferings, bonnets, bodies, housings for equipment protections. Main sewers for buildings, pipes and fittings for industrial waste water coming from the semiconductor, mining, paper& pulp industries; rehabilitation of pipes without digging trenches by the use of uncured soft tubes. Piping up to 10 m in diameter, chemical or wine tanks up to 10 m in diameter. 9 Gratings, gratings for piers with truck traffic, gutters for surface water along motorways; cable shelves for the Channel Tunnel in fireproofed acrylic pultruded sections. Chimneys for factories up to 7 m in diameter. 206

Detailed accounts of thermoset resins for moulding and composite matrices

9 Blades up to 12.5 m length for wind turbines, masts, telephone posts, telegraph pole supports. 9 Fireproofed panels and structures for oil rigs, sandwich structures for protection of underwater oil wellheads. 9 Moulds for concrete elements.

Shipbuilding, water sports 9 Shipbuilding from dinghies up to minesweepers including all the types of race or pleasure boats, sailboards and surfboards, hulls of catamarans; hovercrafts, pilot boats, floating shopping-centres, drydock caissons, sluice gates. 9 Fireproofed glass fibre reinforced polyester for offshore oil rigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors, gratings, handrails, duckboards, ladders. 9 Swimming pools. 9 Sailboards, canoes, fishing boats, dinghies of mass distribution. Electricity, electronics 9 Electricity meter housing, low-voltage fuse boxes, low and mediumvoltage boxes, supports of terminals, connectors, switch parts, housing and handles or soles of domestic iron; handles and buttons of grills and pressure-cookers; buttons. Dishes for satellite TV aerials, urban lampposts, cable shelves, frames and carcasses of solar panels, tubes for scanners (1 m in diameter). 9 Vinylester fuel cell plates. 9 Electricity inclusions. 9 Fuel cell plates. Industry, anticorrosion 9 Formworks, hoods, bonnets, panels, housings, casings for machines; pump housings, gas washers, flue gas scrubbers, pipes and fittings for industrial sewage water, factory chimneys, chemical tanks, settling tanks. 9 Butterfly valves for water, acid and alkali solutions. 9 Compressed-air tanks, fuel tanks for railcars; storage or transport tanks for fuel, foodstuffs, drinking water, wine, chemicals. 9 Drainage pipes DIN 40 up to 2000. 9 Containers for part transports for the nuclear industry, aeronautics. Furniture 9 Baths, basins, sanitary wares, tubs; cabins or sanitary blocks; false marbles, onyx for sanitary. 9 Cabins and doors of public toilets. 9 Translucent roofs. 207

Thermosets and Composites

9

Traffic signs, urban notice boards, signposts for motorways, benches of bus shelters, public benches, Parisian newspaper kiosks, urban telephone shelters, roofs of phone boxes, housing for cash dispensers. 9 Seats for communities. 9 Urban dustbins, old paper containers.

Appliances 9

9

Structural elements, bodies, roofs and doors for display units, refrigerating window displays, refrigerated mobile shops, refrigerating lorries and semi-trailers, refrigerated vans and other vehicles, cold stores. Housing and handles or soles of domestic irons, handles and buttons of grills and pressure-cookers.

Transport 9

9 9 9 9 9 9

High-speed train noses; cabins, doors, floors of funiculars in sandwich. Window frames for high-speed trains, pillars of Berlin S-Bahn. Bumpers, energy-absorbing fenders. Luggage racks for trains, seat frames, individual shelves. Reflectors. Careenages for race motorbikes. Heating insulation sheaths for trains.

Art, decoration, publicity, leisure parks 9

Concrete for moulding of statues (Nikki de St Phalle), knick-knacks and various items, blocks for sculpture, stained-glass windows. 9 Giant advertising articles, bodies and subjects for carrousels, play areas, leisure parks in glass beads or fibre reinforced resins. 9 Cinema, theatre or television decors, dismountable scenes. 9 Figurines up to 35 m high, decors, plays; cars, planes and so on for carrousels; giant toboggans, beams of medieval houses for leisure and theme parks. 9 Decorative objects in foamed resins.

Packaging 9

High-tech or aesthetical packaging such as containers for nuclear industry, aeronautics, and radomes; storage bins, cases for double bass.

Miscellaneous 9 9

Sandable cements for metal or composite repairs. Leg prostheses, surgical corsets, reconstructing plasters for tortoise shells. 9 Terrace coating, buffing wheels, swimming pools. 9 Fishing rods. 9 Scientific inclusions. 208

Detailed accounts of thermoset resins for moulding and composite matrices

4.2.2 Thermal behaviour

Initial behaviour

The H D T A (1.8 MPa) are very variable according to the type of resin and the reinforcements used: 9 30 ~ for a neat flexible grade, 9 Up to more than 200 ~ for a rigid reinforced grade. Although unsaturated polyesters are thermoset resins, moduli can decrease rather rapidly when the temperature rises: 9 For example, for a given neat current grade, the flexural modulus falls by 50% between 20 ~ and 80 ~ 9 On the other hand, for another given glass fibre reinforced grade, the flexural modulus retention is much higher: o At 93 ~ 66% retention o At 121 ~ 43% retention o At 149 ~ 27% retention Figure 4.5 shows the tensile modulus retention expressed as a percentage versus the testing temperature for two composites with identical reinforcements, but different vinylester matrices. The slight increase of the retention is, perhaps, promoted by a postcure. These results relate to few grades only and cannot be generalized.

120% 100% 80%

%

%

60%

%

40% 20%

~ 0% 0

|

|

|

i

|

|

i

,

20

40

60

80

100

120

140

160

Figure 4.5. Vinylester composites. Tensile modulus retention versus testing temperature

Long-term behaviour

The continuous use temperatures in an unstressed state generally vary from 90 ~ up to 140 ~ Higher temperatures can be withstood for shorter times, especially for the heat-resistant grades such as vinylesters. 209

Thermosets and Composites

The UL temperature indices of specific grades range from 105 ~ to 180 ~ for the electrical and mechanical properties including impact. These results relate to the tested grades only and cannot be generalized. Figures 4.6 and 4.7 demonstrate the great ageing differences over nearly two years between two vinylester composites with the same reinforcements, but two different matrices (A and B): 9 For the A matrix, the half-lives (50% retention of flexural strength) vary from 10 to 20 months between 204 ~ and 160 ~ 9 For the B matrix, the half-lives are very short at 182 ~ and 204 ~ and are approximately the same as A at 160 ~

Figure 4.6. Vinylester composite (A) ageing at 160, 182, 204 ~ Examples of flexural strength retention versus time (month)

Figure 4. 7. Vinylester composite (B) ageing at 160, 182, 204 ~ Examples of flexural strength retention versus ageing time (month)

Low temperature behaviour

The glass transition temperatures are high, for example 90-210 ~ Polyester resins and composites are often used at low temperatures in automotive, building, and refrigerating industries. 210

Detailed accounts of thermoset resins for moulding and composite matrices

4.2.3 Optical properties

Transparent and colourless grades are available, used for the manufacture of cover plates or scientific or electric components or technical inclusions. The refractive indexes, for specific grades, are in the range 1.52-1.56. For transparent glass fibre reinforced composites, the grades with low refractive indexes near to that of glass (1.548) are preferred. 4.2.4 Mechanical properties

The mechanical properties, rigidity, impact resistance and creep are very variable according to the grades and the reinforcements. However, generally, the behaviour is satisfactory and allows many mechanical applications as composite matrices. Figures 4.8, 4.9 and 4.10 indicate the general evolution of the main mechanical properties of the resins and composites as the fraction and the length of fibres increase. The aim of these graphs is only to illustrate a principle and they are not graduated. For more precise data see the tables at the end of Section 4.2.

v

Figure 4.8. Unsatured polyester. Tensile strength versus % and length of fibres

Figure 4.9. Unsatured polyester. Tensile modulus versus % and length of fibres 211

Thermosets and Composites

Figure 4.10. Unsatured polyester. Notched impact versus % and length of fibres

Friction

Generally, polyesters are not used for friction parts. Creep

Creep is highly dependent on the reinforcements and load. For the two following examples concerning the same composite, the sets are doubled when the load increases by 50%: 9 0.2% after 1000 hours under a stress of 14 MPa that is a creep modulus of 7 GPa. 9 0.4% after 1000 hours under a stress of 21 MPa that is a creep modulus of 5.250 GPa. In another example (after Amoco data, Bulletin GTSR-127), two beams, one cast and the other pultruded, are tested with a 3-point bending method for more than 100 days and the deflections are studied versus testing time (see Figure 4.11). These two examples are not comparable because all the conditions are different (matrix, reinforcement, process, loading) and that leads to highly dissimilar results: the more loaded beam bends less than the less loaded one.

Figure 4.11. Unsatured polyester: Examples of creep deflection (mm) versus testing time (hours)

All these results prove that each composite grade must be tested before use. 212

Detailed accounts of thermoset resins for moulding and composite matrices

Dimensional stability The moulding shrinkage is difficult to control with some processes, making mass production difficult. Post shrinkage depends on the resin, the reinforcements and the hardening cycles. It can be negative. 4.2.5 Ageing

Dynamic fatigue The dynamic fatigue behaviour is generally quite acceptable, but depends on the reinforcements and the matrix. The two following examples concern composites with different matrices and reinforcements: . For a given glass fibre reinforcement and resin: 107 cycles for a given load . Different glass fibre reinforcement and resin: 1 0 6 cycles for 50% of this load In other tests (after Amoco data, Bulletin IP-81), the range of endurance strengths (Figure 4.12) in cyclic loading of samples immersed in water is very broad according to the type of unsaturated polyester (iso- or ortho polyesters) and the number of cycles.

Figure 4.12. Unsatured polyester: Examples of endurance strengths versus the number of cycles in water

Weathering Unsaturated polyesters are broadly used in those applications where longtime weathering is implied: automotive, shipbuilding, building. For a judicious choice of grades, a suitable hardening and an adapted gelcoat used for the protection of fibres and composites, the mechanical properties remain at an acceptable level and the slight yellowing can be controlled. Preliminary tests, taking account of the particular conditions of use, are necessary. 213

Thermosets and Composites

Chemicals

Resistance to moisture and hot water is generally good and is improved for special so-called "hydrolysis stabilized or resistant" grades. Degradation by boiling water can be significant. Table 4.12 (after Amoco data, Bulletin IP-93) displays some performance retention data versus the immersion times and temperatures for two unsaturated polyesters and one vinylester. The vinylester performs better than the two unsaturated polyesters, which have very different behaviours. Table 4.12

Unsaturated polyester: performance retention after immersion in hot water

Flexural strength, MPa

Flexural modulus, GPa

Barcol hardness

1O0 h boiling water Resin

Polyester A

PolyesterB

PolyesterA

PolyesterB

PolyesterA

PolyesterB

Initial

17

18

0.6

0.6

45

45

Retention after 100 h, water 100 ~ (%)

70

20

80

50

90

90

Resin

PolyesterA

Vinylester

Initial

Polyester A 17

Vinylester PolyesterA 22

0.6

Vinylester 0.5

45

39

Retention after 100 h, water 100 ~ (%)

70

90

80

90

90

90

8760 h water at 71 ~ Polyester

Vinylester

Polyester

Vinylester

Polyester

Vinylester

Initial

16

22

0.8

0.9

52

48

Retention after 8760 h water 71 ~

81

63

84

88

98

98

Many anti-corrosive, anti-acid, anti-alkali grades have an improved chemical resistance. These improvements are specific and each particular case will have to be subjected to an examination. The oxidizing acids break up unsaturated polyesters. The other acids and bases have variable effects, often limited. The unsaturated polyesters are attacked by aromatic hydrocarbons, chlorinated ketones, esters and solvents, but are resistant to aliphatic hydrocarbons and alcohols. In the following list, there appear, by way of examples, a certain number of chemicals that could, after satisfying preliminary tests, be transportable and storable in anti-corrosive polyester resin composite vessels. 9 More or less dilute solutions of hydrochloric, sulphuric, nitric, phosphoric acids; acetic acid, vinegar, fatty acids. 9 Bleaching agents. 9 Alcohols. 9 Alums. 214

Detailed accounts of thermoset resins for moulding and composite matrices

9 Ammonia. 9 Beer, wine, fruit juice. 9 Drinking water, seawater; domestic, urban or industrial aqueous effluents. 9 Products for water treatment. 9 Acrylic emulsion. 9 Fertilizer. 9 Acid smokes. . Gas oil, oils. . Glycols. 9

H2S.

9 . 9 9

Vegetable oils. Milk, whey. Sugar syrup. Saline solutions.

9

S O 2.

Many food grades exist. F/re resistance

The oxygen indices (21 for example) and fire behaviour classifications are naturally weak but can be highly improved by the addition of fireproofing agents, making it possible to reach the V0 UL94 rating. The other properties can be more or less affected. 4.2.6 Electrical properties

The insulating properties are good and allow many electric applications. However, dielectric rigidity can reach relatively low values. Antistatic grades are marketed with surface and transverse resistivities notably lowered. The unsaturated polyesters are used in the manufacture of electromagnetic shieldings. 4.2.T loining

Welding and joining with solvents is useless for all the thermosetting resins. Only adhesives chosen following rigorous tests are permitted for joining. The parts should not be subjected to high stresses. After cleaning by abrasion or/and with solvents, polyesters can be stuck with epoxy adhesives, polyurethanes, cyanoacrylates or acrylic resins whose performances are compatible with the operating conditions. Primers and specific adhesives have been developed for joining to metals. Decoration

Oelcoats and paints are extensively used for the decoration and the protection of the aspect parts for automotive, shipbuilding, building, 215

Thermosets and Composites

appliances, etc. applications. The unsaturated polyesters are also used for the realization of sculptures, stained glass, inclusions etc. Bulk colouring is frequently used. 4.2.8 Specific ISO standards concerning polyesters Raw materials

ISO 584:1982 Plastics- Unsaturated polyester resins - Determination of reactivity at 80 ~ (conventional method) ISO 2114:200(Plastics(polyestelresins)andpaintsandvarnishes(binders) Determination of partial acid value and total acid value ISO 2535:2001 Plastics - Unsaturated-polyester resins - Measurement of gel time at ambient temperature ISO 2554:1997 Plastics - Unsaturated polyester resins - Determination of hydroxyl value ISO 3521:1997 P l a s t i c s - Unsaturated polyester and epoxy r e s i n s Determination of overall volume shrinkage ISO 3672-2:2000 Plastics- Unsaturated-polyester resins (UP-R) - Part 2: Preparation of test specimens and determination of properties ISO 4615:1979 P l a s t i c s - Unsaturated polyesters and epoxide r e s i n s Determination of total chlorine content ISO4901:1985 Reinforced plastics based on unsaturated polyester r e s i n s - Determination of residual styrene monomer content ISO 14848:1998 Plastics- Unsaturated-polyester r e s i n s - Determination of reactivity at 130 ~ ISO 15038:1999 P l a s t i c s - Organic-perester crosslinking agents for unsaturated-polyester thermosetting m a t e r i a l s - Determination of activeoxygen content Designation system and powder moulding compounds

ISO 3672-1:2000 Plastics- Unsaturated-polyester resins (UP-R) - Part 1: Designation system ISO 14530-1:1999 P l a s t i c s - Unsaturated-polyester powder moulding compounds (UP-PMCs) - Part 1: Designation system and basis for specifications ISO 14530-2:1999 P l a s t i c s - Unsaturated-polyester powder moulding compounds (UP-PMCs) - Part 2: Preparation of test specimens and determination of properties ISO 14530-3:1999 P l a s t i c s - Unsaturated-polyester powder moulding compounds (UP-PMCs) - Part 3: Requirements for selected moulding compounds 216

Detailed accounts of thermoset resins for moulding and composite matrices

4.2.9 Trade name examples

AMC, Ampal, Atlac, Atlas M, Beetle polyesters, Civic, Crestomer, Crystic, Derakane, Envirotec, Enydyne, Leguval, Maxguard, Menzolit BMC and SMC, Modar, Norsodyne, Norsomix, Palapreg, Palatal, Premi-Glas, Procore, Resatherm, Rutaform, Synolite, Verkid, Vestopal. 4.2.10 Property tables

Tables 4.13 to 4.20 relate to examples only and cannot be generalized. Table 4.13 Unsaturated polyester unreinforced resins for casting and moulding, matrices for composites: examples of resin properties

Density, g/cm 3

Standard, neat

Flexible, neat

1.1-1.4

1.1-1.3

Shrinkage, % Water absorption, 24 h, %

Fireproofed unreinforced 1.2-1.4 0.05-2

0.1-0.6

Shore hardness, D

0.2-2.5

0.01-2.5

84-94

Barcol hardness

35-60

20-30

35-50

Tensile strength, MPa

25-90

4-45

40-90

Elongation at break, %

1.5-4

10-300

1.5-4

Tensile modulus, GPa

2-4.5

Flexural strength, MPa

50-125

Flexural modulus, GPa

3-4.5

2-3

2-3.5

3-4.5

Compression strength, MPa

150-180

Notched impact D 256, J/m

10-25

25-400

Notched impact, kJ/m e

5-15

10-20

5-12

HDT A (1.8 MPa), ~

50-150

30-90

70-95

CUT unstressed, ~

90-140

90-140

90-140

Thermal conductivity, W / m K

0.1-0.4

0.1-0.5

0.1-0.5

Specific heat, cal/g/~

0.3-0.4

0.2-0.4

Coefficient thermal expansion, 10-5/~

6-12

6-12

2-10

Surface resistivity

1012

1012

1012

Volume resistivity, ohm.cm

1015

1015

1015

Dielectric constant

3-7

3-7

3-7

20-1000

20-1000

20-1000

15-45

15-45

15-45

Loss factor, 10-4 Dielectric strength, kV/mm

217

Thermosets and Composites

Table 4.13 Unsaturated polyester unreinforced resins for casting and moulding, matrices for composites: examples of resin properties Standard, neat

Flexible, neat

Fireproofed unreinforced

Arc resistance, s

60-200

60-200

60-200

Oxygen index, %

21-30

21-30

25-40

General chemical properties Light

Good behaviour. Possible slight surface attack with yellowing. Weathering-resistant grades.

Weak acids

None to light attack

Strong acids

Attack. Acid-resistant grades.

Bases

Attacked to a greater or lesser degree according to the nature, concentration and temperature.

Solvents

Resistant to alcohols, aliphatic hydrocarbons. Attacked by aromatic hydrocarbons, ketones, esters, chlorine containing. Generally fair resistance to moderately hot water. Attacked by boiling water.

Water Food contact

Possible

CUT: continuous use temperature in an unstressed state

Table 4.14 properties

Vinylester neat resins for casting and moulding, matrices for composites: examples of resin Standard, neat

Heat resistant, neat

Toughened, rubber modified

Density, g/cm 3

1.1-1.12

1.1-1.2

1.13

Barcol hardness

35

40

40

81-90

68-73

70

Tensile strength, MPa Elongation at break, %

5-6

3-4

8

Tensile modulus, GPa

3-4

3-4

3.1

Flexural strength, MPa

120-140

125-133

135

Flexural modulus, GPa

3-4

3-4

3.2

Compression strength, MPa

110-115

125-130

86

Compression modulus, GPa

2-3

2-3

2

Notched impact D 256, J/m

22

11

250

HDT A (1.8 MPa), ~

100-125

145-150

80

Glass transition, ~

125-185 5-6

7

Coefficient thermal expansion, 10-5/~

6-7 General chemical properties

Generally, better behaviour than unsaturated polyesters notably versus heat and chemicals 218

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.15

Filled or short fibre reinforced unsaturated polyesters (UP): examples of resin properties

Matrix

UP, antistatic

UP

UP

UP modified, melamine

Filler

Unknown

Textilefibre

Short glassfibre

Cellulose

Density, g/cm 3

1.7-1.73

1.7-1.8

1.9-2.1

1.7-1.9

Shrinkage, %

0.1-0.15

0.01-0.2

0.01-0.1

0.01-0.4

60-80

60-100

60-90

3-3.5

3-4.5

2-3

100-130

160-250

120-140

Tensile strength, MPa

30-62

Flexural strength, MPa

90-140

Flexural modulus, GPa

9-11

Notched impact, kJ/m 2 HDT A (1.8 MPa), ~

>200

Coefficient thermal expansion, 10-5/~

1.8-2

Surface resistivity

107

1011

1012

101~

Volume resistivity, ohm.cm

101~

1014

1015

1014

Dielectric rigidity, kV/mm

1-2 140-150

150-180

120-130

V0

HB to V0

HB to V0

Arc resistance, s

130-140

Oxygen index, %

30-32

UL94 rating

General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. If the fillers are adapted, the chemical properties are the same as the polyester matrix.

Table 4.16

Fire retardant vinylester resins: examples of resin properties

Density, g/cm 3

1.3-1.4

Barcol hardness

40

Tensile strength, MPa

70-75

Elongation at break, %

5

Tensile modulus, GPa

3-4

Flexural strength, MPa

120-125

Flexural modulus, GPa Compression strength, MPa

4 110-120

Compression modulus, GPa

2-3

Notched impact ASTM D256, J/m HDT A (1.8 MPa), ~

11-16 100-115

Coefficient thermal expansion, 10-5/~ Oxygen index, %

6-7 30-41

General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. If the fillers are adapted, the chemical properties are the same as the vinylester matrix. 219

Thermosets and Composites

Table 4.17 Unsaturated polyester BMC: examples of composite properties 7

10-20

22-28

18 Fire retardant, halogen free

Density, g/cm 3

1.76

1.7-1.9

1.76-1.95

1.95

Shrinkage, %

0.02

0.01-0.2

-0.06-0.15

0.18

0.1-0.2

0.1-0.2

0.1-0.2

0.1-0.2

30--40

30-35

Glassfibre, % level

Water absorption, 24 h, % Tensile strength, MPa Flexural strength, MPa

55

40-135

90-115

90

Flexural modulus, GPa

5.5

7-11

9-11

9

HDT A (1.8 MPa), ~

>200

>200

>200

>200

Specific heat, cal/g/~

0.26-0.34

0.26-0.34

0.26-0.34

2

2

2

2

Surface resistivity

1012

1012

1011

1011

Volume resistivity, ohm.cm

1014

1014

1015

1014

4

4

Coefficient thermal expansion, 10-5/~

Dielectric constant Dielectric rigidity, kV/mm

10-15

10-15

10-15

10-15

Oxygen index, %

34

22-45

22-32

80

UL94 rating

V0

HB to V0

HB to V0

V0

Table 4.18

Unsaturated polyester SMC: examples of composite properties Standard grades

Glassfibre, % level

10-20

25-30

32-40

50%

Density, g/cm 3

1.7-1.8

1.7-1.9

1.77-1.84

1.63

0.05-0.15

-0.1-0.18

-0.08-0.1

0.01

0.3-0.7

0.1-0.2

Shrinkage, % Water absorption, 24 h, %

0.1-0.7

Tensile strength, MPa

48-110

Elongation at break, %

80-110

1.6-2

Tensile modulus, GPa

10-12.5

Flexural strength, MPa

90--120

150--210

210-420

200

Flexural modulus, GPa

6-8

7.5-14

11-15

11-16

220

Detailed accounts of thermoset resins for moulding and composite matrices Table 4.18 Unsaturated polyester SMC: examples of composite properties Standard grades Glassfibre, % level HDT A (1.8 MPa), ~

10-20

25-30

32-40

50%

>200

>200

>200

>200

0.26-0.34

0.26-0.34

Glass transition, ~ Specific heat, cal/g/~ Coefficient thermal expansion, 10-5/~

140-210 0.26-0.34 2

1.6-2.3

2

2

Surface resistivity

1012

1011

1012

1011

Volume resistivity, ohm.cm

1014

1014

1014

1014

10-15

10-15

Dielectric constant

4

Dielectric rigidity, kV/mm

10-15

10-15

Oxygen index, %

22-24

22-27

HB to V2

HB to V2

UL94 rating

Specialgrades Glassfibre, % level Density, g/cm 3 Shrinkage, %

Unknown UD

20-33, foamed

1.8

1.3-1.43

1.84-2.1

1.95

--0.03-0.3

-0.08-0.12

-0.04-0.1

0.04

0.5-0.7

0.2-0.3

0.1-0.2

Water absorption, 24 h, %

Unknown, 25fire retardant, fire retardant halogenfree

Tensile strength, MPa

92-285

40-71

51

40-50

Flexural strength, MPa

230-750

60-150

130-200

120

Flexural modulus, GPa

14-22

4.5-12

11

5.5

HDT A (1.8 MPa), ~

>200

>200

>200

>200

Specific heat, cal/g/~

0.26-0.34

0.26-0.34

0.26-0.34

Coefficient thermal expansion, 10-5/~

1.1-1.5

1.7-2

2

2

Surface resistivity

1011

1011

1011

1012

Volume resistivity, ohm.cm

1014

1014

1014

1014

4

4

4

10-15

10-15

10-15

Dielectric constant Dielectric rigidity, kV/mm Oxygen index, %

22

22

50-78

45-50

UL94 rating

HB

HB

V0

V0

221

Thermosets and Composites

Table 4.19

Other glass fibre reinforced unsaturated polyesters: examples of composite properties

Matrix

Unsaturated polyester

Unsaturated polyester

Acrylate urethane

mat

mat

mat

Glassfibre, % level

20-30

40-50

33

Density, g/cm 3

1.3-1.5

1.5-1.75

Tensile strength, MPa

65-90

130-170

112-131

2

2

2-3

Tensile modulus, GPa

5-7

9-10

6-7

Flexural strength, MPa

115-145

180-220

206-218

Flexural modulus, GPa

5-7

9-11

6-7

110-135

165-200

145-174

Reinforcement

Elongation at break, %

Compression strength, MPa Compression modulus, GPa

5-6

ILSS, MPa

24

Notched impact D 256, J/m HDT A (1.8 MPa), ~ Thermal conductivity, W/m.K

1410-1420 >200

>200

0.14-0.19

0.2-0.3

3-4

2-2.4

Coefficient thermal expansion, 10-5/~

Matrix

>200

Unsaturated polyester

Unsaturate d polyester

Unsaturated polyester

Acrylate urethane

Reinforcement

Fabric

Fabric

Roving

Roving

Glassfibre, % level

40-50

50-60

70-80

50

Density, g/cm 3

1.5-1.75

1.6-1.85

1.9-2.1

Tensile strength, MPa

200-240

240-275

400-800

260-300

2

2

2

1.6-2

Tensile modulus, GPa

10-14

14-18

21-26

17-20

Flexural strength, MPa

220-260

260-300

400-500

380-410

Flexural modulus, GPa

10-14

14-18

10-12

150-180

180-200

220-240

Elongation at break, %

Compression strength, MPa Compression modulus, GPa

13

ILSS, MPa

28-29

Notched impact D 256, J/m HDT A (1.8 MPa), ~ Thermal conductivity, W/m.K Coefficient thermal expansion, 10-5/~ 222

1300-1470 >200

>200

>200

0.19-0.25

0.25-0.31

0.37-0.41

1.8-2.2

1.6-1.8

1.2-1.4

>200

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.20

Aramid and carbon fibre reinforced acrylate urethane: examples of composite properties

Matrix

Acrylate urethane

Acrylate urethane

Reinforcement

Aramid fibre

Carbon fibre fabric

Fibre, % level

40

50

250-260

500-540

Elongation at break, %

2.2

1.4-2

Tensile modulus, GPa

12

42

Flexural strength, MPa

340-360

360-375

Flexural modulus, GPa

10-11

20-25

Compression strength, MPa

150-170

140-150

Compression modulus, GPa

13

33

ILSS, MPa

20

21

470-500

710-780

Tensile strength, MPa

Notched impact D 256, J/m

4.3 Phenolic resins (PF) Phenolic resins formaldehyde:

are

obtained

by the

reaction

of tri-phenols

and

9

In an acidic medium: a first step leads to a thermoplastic that is reticulated in a second step by a curing agent or hardener (hexamethylenetetramine). These resins are called PF2 resins, novolac or "two step". The reaction produces ammonia. The moulding powders most frequently used are of this PF2 type.

9

Reaction in an alkaline medium yields products known as: PF1 resins, resols or "one step". They are crosslinked by heating. The reaction produces water vapour instead of ammonia. They are used for laminating and less frequently for moulding.

The phenolic resins are filled with materials of very diverse natures: short or long glass fibres, glass beads, wood flour, mica, cellulose, cotton, fabrics, rubber, graphite, P T F E , m o l y b d e n u m sulphide... The filler level can be as high as 75%. They are also used as a composite matrix. Consequently their properties and uses cover a very broad range. The designation of some phenolic moulding powders is normalized by several standards such as ISO 800 (see Table 4.21). 223

Thermosets and Composites Table 4.21

Designation examples of some phenolic moulding powders after ISO 800

Generalpurpose, wood-flour filled PFIA1

General purpose, ammonia free

PF1A2

General purpose, ammonia free, improved electrical properties

PF2A1

General purpose

PF2A2

General purpose, improved electrical properties

Heat resistant, glassfibre reinforced PF2Cx

Beware: the old PF2C1, PF2C2, PF2C3 were asbestos filled. The use of asbestos is now forbidden.

Impact res#tant, cotton filled PF2D1

Good impact resistant

PF2D2

High impact strength

PF2D3

Very high impact strength

PF2D4

The highest impact strength

Mica-filled phenolic moulding powders PF2E1

Low loss factor

The same ISO 800 specifies specific characteristics of certain phenolic moulding powders. Table 4.22 shows some examples. Table 4.22

Examples of characteristics of certain phenolic moulding powders after ISO 800

PF1A 1

PF1A2

PF2A 1

PF2A2

Flexural strength, MPa

60

60

70

70

Charpy impact ISO 179, kJ/m 2

1.3

1.3

1.5

1.5

Izod impact ISO 180, J/m

13

13

13

13

HDT A (1.8 MPa), ~

120

110

140

140

Volume resistivity, ohm.cm Dielectric rigidity at 90 ~

10 l~

108

MV/m

3.5

Dissipation factor, 10-4 Water absorption, mg Free ammonia, %

0.1 60

60

60

60

0.02

0.02

PF2D 1

PF2D2

PF2D3

PF2D4

Flexural strength, MPa

55

55

55

55

Charpy impact ISO 179, kJ/m 2

2.5

3.5

6

12

Izod impact ISO 180, J/m

25

35

60

120

HDT A (1.8 MPa), ~

135

140

140

140

Water absorption, mg

80

150

150

150

224

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.22

Examples of characteristics of certain phenolic moulding powders after ISO 800 PF2E1

Flexural strength, MPa

50

Charpy impact ISO 179, kJ/m 2

1.5

Izod impact ISO 180, J/m

15

HDT A (1.8 MPa), ~

160

Volume resistivity, ohm.cm

1012

Dielectric rigidity at 90 ~

MV/m

5.8

Dissipation factor

0.03

Arc resistance, s

175

Water absorption, mg

20

4.3.1 Generalproperties Advantages

Attractive price and price/property ratios, very good heat resistance, high glass transition temperature, good creep behaviour, good mechanical properties, resistance to a great number of chemicals such as most common solvents, weak acids, natural oils, fats, greases, petroleum products, and automotive fluids; resistance to light and weathering in spite of slight surface deteriorations. Fire r a t i n g s - in a fire, relatively low amounts of smokes at a relatively low level of toxicity are produced by specific grades. Usable as a matrix for composites. Drawbacks

Opaque, dark colours, significant shrinkage, unusable for food contact, low arc resistance except special grades, water or ammonia degassing, low resistance to bases except special grades, decomposition by oxidizing strong acids, limited flexibility, low elongation at break. Special grades

Apart from the ISO specified grades, there are numerous others. They are classified according to the type of application, formulation, properties: 9 Compression, transfer, injection, machining, impregnation, coating for stratification, foam, agglomeration (grinding stones and abrasives), preimpregnated, SMC, RTM, pultrusion, filament winding, centrifugation, alcohol or aqueous solution to penetrate and saturate paper and other similar substrates. 9 Long or short glass fibre reinforced, for thin or thick parts, toughened, tribological compounds with graphite, MoS 2 or PTFE; very highly filled (75%), excellent compressive strength, exceptional heat resistance, dimensional stability, very low thermal expansion, fireproofed, UL listed, low flexural modulus for clipable fixtures, more or less thixotropic, low shrink... 225

Thermosets and Composites

Cost

Phenolics are very cost-effective engineering materials ranging from less than ~2/kg for most grades to ~8/kg for glass reinforced specific grades. Processing

Compression, transfer, injection, machining, impregnation, coating for stratification, foam, agglomeration (grinding stones and abrasives), preimpregnated, BMC, SMC, RTM, pultrusion, filament winding, centrifugation, alcohol or aqueous solution to penetrate and saturate paper and other similar substrates Applications [see Chapter 2 for further information]

Consumption The consumption of phenolic resins by the industrialized countries accounts for 12-22 % of total thermoset consumption and is approximately 2-4 % of the plastic total consumption. The demand for phenolic resins has slightly declined in recent years. A lot of applications are outside the scope of this book, such as adhesives, resins for foundry, paints etc. Among the consumption identified as relevant to this discussion, the relative shares of the various applications are in the range: Moulding 9 50% for electricity: boxes, elements of connection, plugs and sockets etc 9 25 % for household and electric household appliances: handles, various parts 9 15 % for the automobile: heads of coils, cases of heating, parts of brake systems 9 10% miscellaneous: stops, knobs, pinions, tribological parts... Other applications: 9 40% stratification, plywood, agglomerated, impregnated paper 9 12% foundry 9 8% adhesives 9 3% abrasives 9 3% paintings 9 2% brake linings 9 32% miscellaneous. Examples of operational or development parts are listed below.

Automotive and transportation 9 Mechanical applications: parts of water pumps, water pump housings, disc brake parts, disc brake calliper pistons, power-assist braking components, drive pulleys, accessory drive pulleys, multi V pulleys, toothed pulleys and tensioners, transmission components, oil filter adapters, impellers, thermostat housings, water inlets & outlets, ABSactivating parts, ashtrays. 226

Detailed accounts of thermoset resins for moulding and composite matrices

9

Electrical applications: solenoids, starter motor commutators, alternator sliprings, commutators. 9 Safety parts: Body elements as noses for high-speed trains (Eurostar); body elements, station and rolling stock equipment for subway and other public transport; control consoles for Eurostar trains; partitions and interior panels, elements for fast passenger ships. . Fireproofed glass fibre reinforced phenolic resins for offshore oilrigs: safety shelters, floors, explosion-proof panels, pultruded profiles for bearing floors. 9 2-1itre experimental engine in glass fibre reinforced phenolic resin (the moving parts and the combustion chambers are in metal).

Electricity 9

9

Commutators, rings, coil housings, low-voltage engineering, cases, bases and lids of switches, cases of meters, base plates, lamp sockets, lamp cases, thermostats, electricity meters, special lamp holders, circuit breaker parts. EMI shielding.

Household appliances 9

Parts for domestic irons, handles and buttons of cookers, parts of toasters. 9 Screw caps, handles and buttons of cookers, pan handles and knobs. 9 Wheels for ovens.

Building and civil engineering 9 Fireproofed domes, boardings, opaque roofs of public buildings; fire doors, firebreak panels. 9 Decorative laminates, coatings for interior of dwelling, floors and partitions of buildings, shelters. 9 Safety shelters and floors of oilrigs.

Aeronautics o Electrical motors in aeroplanes, satellites, rockets. 9 Ablative materials, heat shields of space capsules.

Laminates, plywood, paper o 9 9 o o

Electrical and decorative laminates. Wood composites, plywood and particleboards. N E M A electrical laminates. Clutch facings. Filtration products.

Miscellaneous 9 Bearings, parts, axial joints, cases and base plates of machines and fittings. 227

Thermosets and Composites

9

9 9 9 9 9 9 9

Anti-friction and friction products. Parts of gas meters, steering wheels. Abrasive wheels, grinding wheels and coated abrasives. Foundry moulds and cores. Foam insulation. Adhesives and glues. Rubber tackifiers. Coatings and varnishes.

4.3.2 Thermal behaviour

Initial behaviour

Glass transition temperatures are high, ranging from 170 ~ to 200 ~ and 300 ~ with proper post curing. Consequently, the modulus retentions are excellent at high temperatures. The H D T A (1.8 MPa) range from 110 ~ to 180 ~ for the organic filled grades and 150 ~ up to 230 ~ for the mineral or glass fibre filled grades. The moduli vary little with the temperature rise: for example, for four given grades: . For one the tensile modulus does not vary significantly between 20 ~ and 120 ~ 9 For another example, the flexural modulus at 150 ~ is 13 GPa for a short glass fibre reinforced grade and 17 GPa for a long glass fibre reinforced. . For the last one, the flexural modulus retention is 92% at 149 ~ The strength retentions are also good but slightly different: 9 81% for compressive strength at 121 ~ 9 75% for flexural strength at 149 ~ These results relate to few grades only and cannot be generalized. Long-term behaviour

Some phenolic resins are heat resistant: in the absence of stresses, the continuous use temperatures range from 100 ~ to 170 ~ with, for example, 25 000 hours lifespan for temperatures of 130-150 ~ The typical U L use temperature index is 150 ~ but is extended to 180 ~ for some grades. Figures 4.13 and 4.14 show the performance retention of some BMCs during ageing in hot air: 9 For the tensile strength at temperatures from 150 ~ to 225 ~ (Figure 4.13) for one grade: the half-life is around 1000 hours at 225 ~ or 3000 hours at 200 ~ 9 For the modulus at 225 ~ (Figure 4.14) for two other grades: the halflife of the order of 1000 hours to 1700 hours according to the grade. 228

Detailed accounts of thermoset resins for moulding and composite matrices

Figure 4.13. Example of phenolic BMC ageing at 150 ~ up to 225 ~

Tensile retention versus time

Figure 4.14. Example of ageing of two phenolic BMC: Modulus retention versus time at 225 ~

For short durations, the service temperatures can be much higher, especially if the parts are postcured. The temperatures for a 24-hour service vary from 150 ~ according to the grades.

to 260 ~

4.3.3 Optical properties

The phenolic resins are opaque, often black or dark coloured. Frequently, the parts have a brilliant surface. 4.3.4 Mechanical properties

The mechanical properties are good: strong rigidity, very good heat retention of the properties, very good creep behaviour. Some special grades with a lower flexural modulus (6 GPa) have the possibility of making clipable fixtures with preservation of the high temperature resistance. The impact behaviour depends greatly on the fillers and modifiers. 229

Thermosets and Composites

Friction The phenolic resins exist in special self-lubricating grades filled with PTFE, graphite or molybdenum disulphide for friction parts with low dry-friction coefficients (static and dynamic). The highly graphite-filled phenolic resins are thermally conductive, and antistatic or EMI as well. Creep Creep is very weak, for example" lower than 0.1% after 1000 hours under a load of 14 MPa for a given grade; that is, a creep modulus of 14 GPa. For comparative tests for the same duration, the creep modulus at 23 ~ under 14 MPa load depends on the filler: 9 Glass fibre: 17 GPa 9 Mineral filler: 14 GPa 9 Cellulose: 14 GPa. These results relate to few grades only and cannot be generalized. Dimensional stability The moulding shrinkage and the moisture absorption depend on the grade, notably the filler: the mineral or glass bead filled and glass fibre reinforced products give the best results. 4.3.5 Ageing

Dynamic fatigue The dynamic fatigue strength depends on the filler and the grade: 9 Glass fibre: 106 cycles for a given load. 9 Cellulose: 1 0 4 cycles for half the same load. 9 Wood flour: 1 0 4 cycles for 40% of the same load. These results relate to few grades only and cannot be generalized. Weathering The light resistance is fair in spite of a risk of surface deterioration. Chemicals Generally, the phenolic resins are more or less chemically resistant depending on the nature of the phenolic resin, the filler type, the exact composition of the fluids, the temperature and other constraints. After a pre-selection it is necessary to carry out extensive tests in the service conditions before the final selection. The following results relate to specific grades only and cannot be generalized: 9 The resistance to moisture and hot water is good except for highly filled grades with hygroscopic materials like wood flour. Special grades for hot and wet climates are available. 230

Detailed accounts of thermoset resins for moulding and composite matrices

9

Strong and oxidizing acids decompose phenolic resins. Other acids are without effect or have a special surface action. 9 The bases attack the phenolic resins to a greater or lesser degree according to their concentration. Alkali-resistant grades are used for the textile industry and dyeing. 9 The behaviour with organic chemicals is generally acceptable, especially for the mineral filled grades and allows uses such as stoppers, and parts in contact with brake fluid or pyralene. 9 Typical exposures include gasoline, alcohol, oil, glycol, brake fluid, various hydrocarbons, and also weak acids and bases. o Certain phenolic resins are specified for the protective inner lining of tanks that are used for bulk transfer of acids and other corrosive chemical products. 9 Phenolics are resistant to aromatic or aliphatic, polar or non-polar common organic solvents, aqueous salt solutions, halogenated organics such as carbon tetrachloride or trichloroethane, and automotive fluids such as brake fluid, antifreeze, glycol. Table 4.23 displays some examples of phenolic resin chemical behaviour at room temperature. Table 4.23

Examples of phenolic resin chemical behaviour at room temperature Immersion time, Tensile Modulus Weightgain, Surface attack days retention,% retention, % %

Water Water

365

75

80

Acids Sulphuric acid 35 %

42

2.2

Moderate

Nitric acid 10%

42

-0.9

Moderate

Hydrochloric acid 10%

42

-2.4

Moderate

Unspecified mineral acid

365

52

60

Unspecified organic acid

365

78

82

79

90

1.8

Strong

0.1

No change

Salt solution Saturated salt solution

365

Base Sodium hydroxide 10%

42

Hydrocarbons Kerosene and fuels

365

Toluene

42

96

93

231

Thermosets and Composites

Table 4.23

Examples of phenolic resin chemical behaviour at room temperature

Immersion time, T e n s i l e Modulus Weightgain, Su~Caceattack days retention,% retention, % % Oxygenated solvents Alcohol

365

Acetone

42

45

45 0.1

No change

0.2

No change

Chlorinated solvents Unspecified chlorinated solvent

365

Trichloroethylene

42

96

95

Fire resistance

The oxygen indices, weak with combustible fillers such as cotton, can reach values of 50 and a U L V0 rating for the mineral filled moulding powders, or even 98 for BMC highly filled with fireproofing agents. Being infusible, thermosets do not drip while burning. In a fire situation, phenolic resins produce a relatively low amount of smoke at a relatively low level of toxicity. In a typical oxidative atmosphere phenolic resins have a high char yield. In an inert atmosphere at very high temperatures, phenolic resins will result in a structural char that contributes to structural integrity. These fire characteristics of phenolic resins are used in structural composites, heat shields and other ablative materials. 4.3.6 Electrical properties

Hygroscopic fillers are detrimental to the insulating properties. The dielectric losses involve the heating by high frequency (HF). This is a pre-fieating method for compressed powders for transfer moulding. Mica increases dielectric rigidity and decreases the loss factor. Arc resistance is naturally low but is improved for some special grades. 4.3.7Joining

Welding and joining with solvents is useless as for all the thermosetting resins. Only adhesives chosen following rigorous tests are allowed for joining. The parts should not be subjected to high stresses. After cleaning by abrasion and/or with solvents, the parts can be stuck with adhesives whose performances are compatible with the operating conditions. Primers and specific adhesives have been developed for joining to metals. 232

Detailed accounts of thermoset resins for moulding and composite matrices

Decoration

Painting is used for the decoration and protection of parts where aspect is important. 4.3.8 Foams

Unlike the more-usual dense industrial polymers, which are processed as carefully as possible while avoiding the formation of bubbles, vacuoles etc., the alveolar materials (foams) result from the desire to introduce, in a controlled way, a certain proportion of voids with the aim of improving the thermal or phonic insulating character. The alveolar materials consist of a polymer skeleton surrounding the cells, which may be closed or partially or completely open to neighbouring cells or the outside. The intrinsic properties ensue from those of the phenolic resin with: 9 A reduction in the mechanical properties due to the small quantity of material and the high proportion of gas. 9 A reduction in the chemical resistance due to the highly divided nature of the material. The thin cell walls immediately absorb liquids and gases and are rapidly damaged. 4.3.9 Specific ISO standards concerning phenolic resins Raw materials

ISO 119:1977 Plastics- Phenol-formaldehyde mouldings- Determination of free p h e n o l s - Iodometric method ISO 120:1977 Plastics- Phenol-formaldehyde mouldings- Determination of free ammonia and ammonium compounds - Colorimetric comparison method ISO 172:1978 Plastics- Phenol-formaldehyde m o u l d i n g s - Detection of free ammonia ISO 308:1994 Plastics- Phenolic moulding m a t e r i a l s - Determination of acetone-soluble matter (apparent resin content of material in the unmoulded state) ISO 8618:1995Plastics-Liquidphenolicresins-Conventionaldetermination of non-volatile matter ISO 8619:1995 Plastics - Phenolic resin p o w d e r - Determination of flow distance on a heated glass plate ISO 8974:2002 Plastics - Phenolic resins - Determination of residual phenol content by gas chromatography ISO 8975:1989 Plastics - Phenolic resins - Determination of pH ISO 8987:1995 Plastics - Phenolic resins - Determination of reactivity on a B-transformation test plate 233

Thermosets and Composites

ISO 8988:1995 Plastics - Phenolic resins - Determination of hexamethylenetetramine c o n t e n t - Kjeldahl method and perchloric acid method ISO 8989:1995 Plastics - Liquid phenolic resins - Determination of water miscibility ISO 9396:1997 Plastics - Phenolic resins - Determination of the gel time of resols under specific conditions using automatic apparatus ISO 9397:1995 Plastics - Phenolic resins - Determination of freeformaldehyde c o n t e n t - Hydroxylamine hydrochloride method ISO 9771:1995 Plastics - Phenolic r e s i n s - Determination of the pseudoadiabatic temperature rise of liquid resols when cured under acid conditions ISO 9944:1990 P l a s t i c s - Phenolic r e s i n s - Determination of electrical conductivity of resin extracts ISO 10082:1999 Plastics - Phenolic resins - Classification and test methods ISO 11401"1993 Plastics - Phenolic resins - Separation by liquid chromatography ISO 11402:1993 Plastics - Condensation resins - Determination of free formaldehyde ISO 11409:1993 Plastics - Phenolic resins - Determination of heats and temperatures of reaction by differential scanning calorimetry ISO 14849:1999 Plastics- Phenol-formaldehyde mouldings- Determination of free ammonia and ammonium c o m p o u n d s - Indophenol method

Phenolic resins: Designation system, specifications and powder moulding compounds ISO 800:1992 P l a s t i c s - Phenolic moulding m a t e r i a l s - Specification ISO4896:1990 P l a s t i c s - Melamine/phenolic moulding m a t e r i a l s Specification ISO 4898:1984/Add 1:1988 Phenol-formaldehyde cellular plastics (RC/PF) ISO 14526-1:1999 P l a s t i c s - Phenolic powder moulding compounds (PF-PMCs) - Part 1" Designation system and basis for specifications ISO 14526-2:1999 P l a s t i c s - Phenolic p o w d e r moulding compounds (PF-PMCs) - Part 2: Preparation of test specimens and determination of properties ISO 14526-3:1999 P l a s t i c s - Phenolic p o w d e r moulding compounds (PF-PMCs) - Part 3: Requirements for selected moulding compounds

Melamine~phenolic: designation system, specifications and powder moulding compounds ISO4896:1990 P l a s t i c s - Melamine/phenolic moulding m a t e r i a l s Specification ISO 14529-1:1999 Plastics - Melamine/phenolic powder moulding compounds (MP-PMCs) - Part 1: Designation system and basis for specifications 234

Detailed accounts of thermoset resins for moulding and composite matrices

ISO 14529-2:1999 P l a s t i c s - Melamine/phenolic powder moulding compounds (MP-PMCs) - Part 2: Preparation of test specimens and determination of properties ISO 14529-3:1999 P l a s t i c s - Melamine/phenolic powder moulding compounds (MP-PMCs) - Part 3: Requirements for selected moulding compounds 4.3.10 Trade name examples

Bakelite, Norsophen, Resinol, Rutaphen, Vyncolit. 4.3.11 Property tables

The following results shown in Tables 4.24 to 4.29 relate to examples only and cannot be generalized. See also Table 4.22. Table 4.24 Examples of glass fibre reinforced phenolic moulding powders Standard & highfilled

High strength

Low modulus

Density, g/cm 3

1.7-2.1

1.6-1.8

1.4

Shrinkage, %

0.1-0.6

0.2-0.3

0.4-0.6

Water absorption, 24 h, %

0.05-0.1

0.1-0.2

0.15

Tensile strength, MPa

40-100

70-130

40-60

Elongation at break, %

0.2-0.4

0.6-1

0.5-0.6

Tensile modulus, GPa

13-30

14-19

5-7

Flexural strength, MPa

60-190

200-270

100-140

Flexural modulus, GPa

15-25

14-17

4.5-6.5

Compression strength, MPa

190-380

250-320

180-210

Rockwell hardness, M

110-120

Notched impact, kJ/m 2

2-16

Unnotched impact, kJ/m 2 Ratio modulus 80~

~

%

H D T A (1.8 MPa), ~

150-230

Continuous use temperature, ~

120-170

Max. temperature for 24 h service, ~

160-210

Thermal conductivity, W/m.K

0.5-0.7 1.2-3

Dielectric constant Dielectric loss factor,10 -4

10-12

180-210

170-190

155-190

140-160 150-180

1.5-4

3-6

1011-1012

Surface resistivity Volume resistivity, ohm.cm

3-5

13-20 100

H D T C (8 MPa), ~

Coefficient thermal expansion, 10-5/~

3.5-6.5

1010-1013

1011

4-8 300-1000 235

Thermosets and Composites

Table 4.24 Examples of glass fibre reinforced phenolic moulding powders Standard & high filled Dielectric rigidity, kV/mm

High strength

Low modulus

10-30

30

Arc resistance, s

125-200

175

UL94 fire rating

V1 to V0

V0

H B to V1

Hybrid GF &glass beads

110 halogen~ee

Rubber toughened

1.7

1.6-1.8

1.5-1.7

0.4-0.5

0.2-0.6

0.1-0.3

Density, g/cm 3 Shrinkage, % Water absorption, 24 h, %

0.15

Tensile strength, MPa

70-90

70-80

90-100

Elongation at break, %

0.65-0.8

0.8-1

1.1-1.3

Tensile modulus, GPa

12-15

10-11

9-10

Flexural strength, MPa

190-210

130-150

160-180

Flexural modulus, GPa

12-14

12-13

12-13

290-330

250-300

250-300

3.5-5

2.5-3.5

4-5

190-210

190-210

Compression strength, MPa Notched impact, kJ/m 2 Unnotched impact, kJ/m 2

12.5-14.5

I-IDT A (1.8 MPa), ~

170-190

HDT C (8 MPa), ~

140-160

Continuous use temperature, ~

140-150

140-185

Max. temperature for 24 h service, ~

160-230

200-260

1.5-2

1.5-2

Coefficient thermal expansion, 10-5/~

2-5

Surface resistivity

10 l0

Volume resistivity, ohm.cm

1012

Dielectric loss factor, 10-4 Dielectric rigidity, kV/mm

30

Arc resistance, s

125

UL94 fire rating

V1 to V0

109-1011

1010-1012

1000-3000

500-1500

20-25

25-30

V0

V0

Chemical behaviour: indicated general chemicalproperties are subject to the compatibility of thefillers and reinforcements with the ambient conditions. Light

Superficial browning

Weak acids

None to slight attack

Strong acids

Superficial attack; decomposition by strong oxidizing acids

Bases"

More or less marked attack according to the bases and the concentrations: special alkali resistant grades are marketed

Organic solvents

Generally good resistance

Food contact

No

236

'

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.25 Examples of mineral filled phenolic moulding powders Mica

Rubber toughened Regrindscrapfilled

Density, g/cm 3

1.4-1.8

1.3-1.4

1.5-1.6

Shrinkage, %

0.2-0.9

0.6-1

0.3-0.6

Water absorption, 24 h, %

0.1-0.5

0.4-1

Tensile strength, MPa

30-70

20-30

Elongation at break, %

0.1-0.5

Tensile modulus, GPa

8-20

Flexural strength, MPa

40-70

50-60

3-6 90-110

Flexural modulus, GPa

8-9

Compression strength, MPa Notched impact, kJ/m 2

250-300 1.5-6

3-9

1.8-2.2

HDT B (0.46 MPa), ~ HDT A (1.8 MPa), ~

190-210 150-220

110-120

170-190

Continuous use temperature, ~

120-160

110-130

120-140

Max. temperature for 24 h service, ~

160-210

150

200-245

Thermal conductivity, W/m.K

0.5-0.7

Specific heat, cal/g/~

0.3-0.4

0.3-0.4

2-7

5-7

2.5-3

109-1011

109-1011

200-1500

900

2000-5000

Dielectric rigidity, kV/mm

10-20

10

10-15

Oxygen index, %

35-50

UL94 fire rating

V1 to V0

HB

V0

Coefficient thermal expansion, 10-5/~ Resistivity, ohm.cm Dielectric constant Dielectric loss factor,10 -4

101~ 4-9

Table 4.26 Examples of organic filled phenolic moulding powders Woodflour

Textile

Cellulose

Density, g/cm 3

1.3-1.5

1.3-1.5

1.35-1.45

Shrinkage, %

0.5-0.9

0.3-1.2

0.6-0.8

Water absorption, 24 h, %

0.1-0.5

0.2-1.2

0.5-0.7

Tensile strength, MPa

25-60

25-60

<1

1-4

Tensile modulus, GPa

Elongation at break, %

6-10

6-10

7-10

Flexural strength, MPa

50-100

40-80

70-90

Flexural modulus, GPa Compression strength, MPa Rockwell hardness, M

6-8

7-10

200-250

170-205 100-110 237

Thermosets and Composites

Table 4.26 Examples of organic filled phenolic moulding powders Notched impact, kJ/m 2

Woodflour

Textile

1.5-4

2.5-15

Notched impact D 256, J/m

16-37

H D T B (0.46 MPa), ~

180-220

H D T A (1.8 MPa), ~

110-200

120-180

165-205 150

Continuous use temperature, ~

110-140

100-140

Max. temperature for 24 h service, ~

150-210

150-210

Thermal conductivity, W/m.K

0.3

0.3

0.2-0.4

0.3-0.4

2-5

4-5

Resistivity, ohm cm

109-1013

109-1011

Dielectric constant

4-9

4-9

100-3000

500-2500

Specific heat, cal/g/~ Coefficient thermal expansion, 10-5/~

Dielectric loss factor,10 -4

Cellulose

Dielectric rigidity, kV/mm

8-25

8-20

Oxygen index, %

25-45

25-32

UL94 fire rating

HB to V0

HB to V1

0.3-0.4

3.5-4.5 101~

11-16

Table 4.27 Examples of tribological phenolic moulding powders (after Vynco) Lubricating additive Density, g/cm 3 Shrinkage, % Water absorption, 24 h, %

Graphite

MoS2

PTFE

1.7

1.7

1.7

0.15-0.25

0.2-0.3

0.3-0.4

0.1

0.15

0.15

Tensile strength, MPa

50-70

75-85

50-60

Elongation at break, %

0.4-0.5

0.7-0.8

0.6-0.7

Tensile modulus, GPa

17-20

11-14

9-12

Flexural strength, MPa

130-140

160-180

130-150

Flexural modulus, GPa

13-16

11-14

9-11

160-190

270-300

220-240

2.5-4

2.5-4

2.5-4

6-8

9-11

7-9

H D T A (1.8 MPa), ~

200-220

170-190

170-190

H D T C (8 MPa), ~

175-195

150-170

150-170

1.5-4

2-5

2-5

Compression strength, MPa Notched impact, kJ/m 2 Unnotched impact, kJ/m 2

Coefficient thermal expansion, 10-5/~ Volume resistivity, ohm.cm

1012-1013

Dielectric rigidity, kV/mm

30

Arc resistance, s UL94 fire rating

238

V0

30

125

175

V1 to V0

V1 to V0

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.28

Glass fibre reinforced phenolic SMC and BMC: examples of properties SMC

Density, g/cm 3

Fireproofed BMC

1.6-1.8

Tensile strength, MPa

100

Flexural strength, MPa

130-170

77-86

6-10

7-8

4-7

5.5-6

Flexural modulus, 23 ~

GPa

Flexural modulus, 150 ~

GPa

Flexural modulus, 175 ~

GPa

5-5.5

H D T A (1.8 MPa), ~

>200

>250

Oxygen index, %

50-90

98-99

UL94 fire rating

V0

V0

Ageing: 2500 h in hot air 150 ~

modulus retention, %

90

175 ~

modulus retention, %

70-80

200 ~

modulus retention, %

40-75

200 ~

strength retention, %

10-35

Table 4.29

Phenolic foam: examples of properties

Density, kg/m 3 Stress to 10% compression, MPa Creep 48 h, 80 ~ Creep 7 days, 70 ~

30

40

60

0.060

0.100

0.250

20 kPa in compression, %

<5

40 kPa in compression, %

<5

Force to failure under bending, N Thermal conductivity, W/m.K Dimensional variation after 48 hours at 70 ~

%

15

25

35

0.020-0.035

0.020-0.035

0.037

2

2

2

4.4 The amino resins: melamine (MF) and urea-formaldehyde (UF) Melamines are obtained by the reaction of melamine and formaldehyde to yield: 9 Moulding powders filled with materials of very diverse natures: glass fibres, wood flour, cellulose, cotton, mineral products, mixtures of organic and inorganic materials. They can be modified by other resins such as phenolics or unsaturated polyesters. Consequently their properties and uses can vary greatly. 9 Unhardened moulding sheets for compression moulding. 9 Aqueous solutions for adhesives and impregnation. The urea-formaldehydes are obtained by reaction of urea and formaldehyde. The moulding powders are currently of reduced use and the number of commercially available grades is limited. The indications, which follow, remain general. 239

Thermosets and Composites

4.4.1 General properties

Advantages Aesthetics, beautiful aspect, brilliancy, clear colours, scratch- and abrasionresistant surface; good electrical properties including arc resistance, fairly good mechanical properties ("unbreakable" dishes); generally good behaviour in the presence of many organic chemicals (notably the detergents); self-extinguishing grades (UL ratings); food-contact grades for the melamines which, moreover, offer a better water and moisture resistance than the urea-formaldehydes; more attractive price for urea-formaldehydes. Drawbacks

Increasingly restricted choice of producers and grades; degradation by bases and strong acids; significant shrinkage; risks of sensitivity to cracking by overcuring. The urea-formaldehydes are less resistant to moisture than melamines and cannot be used for food contact. Melamines are more expensive than urea-formaldehydes.

Specialgrades They are classified according to the formulation, properties or type of application: . Cellulose, mineral, glass fibre, wood flour, organic/mineral mixed fillers... 9 Food contact, reduced water absorption, improved electrical properties, arc resistant, high temperature, low sensitivity to cracking, fireproofed... 9 IMC surface coating for SMC. Some reinforced melamines are supplied in sheet form for compression moulding. Cost

Melamines and urea formaldehydes are very cost-effective polymers ranging from: 9 ~1.5-5/kg for the melamines. 9 ~ l - 3 / k g for given urea-formaldehyde grades.

Processing Compression, transfer, injection, casting stratification, varnishing, gluing, foaming.

moulding;

impregnation,

Applications [see Chapter 2 for further information] The amino resin consumption of industrialized countries accounts for 17-36% of the total thermoset consumption and is approximately 3-6% of the total plastic consumption. A large number of applications, sometimes up to 95 %, are outside the framework of this book. For the moulded parts, the two main markets are electricity and dishes. Examples of operational or development parts are listed below. 240

Detailed accounts of thermoset resins for moulding and composite matrices

Electricity 9

High and low voltage electrical engineering, switches, distributor boxes, meter cases, regulator cases, hoodings of small electric motors, fuse boxes in melamines. 9 Low voltage electrical engineering, switches, distributor boxes, meter cases, regulator cases, in phenolic or polyester modified melamines. 9 Low voltage sockets and plugs, switches, adaptors, junction boxes, dimmer switches in urea-formaldehydes.

Household appliances 9

Crockery, dishes, drinking glasses, tooth glasses, knives, forks, spoons, "unbreakable" plates and goblets, medical articles of beautiful aspect, screw caps in food-contact grades of melamines. 9 Non food-contact parts of beautiful aspect, for example toilet flaps, in urea-formaldehyde. 9 Handles of domestic irons, control buttons, panhandles, buttons of pan lids, ashtrays in melamines or phenolic modified melamines or unsaturated polyester modified melamines. 9 Base plates for small household appliances in urea-formaldehyde.

Packaging 9

Decorative screwed plugs in urea-formaldehyde.

Building 9 o

Decorative acoustic flagstones, suspended baffles, panels and partitions, soundproofing of roll-shutters boxes in melamine foam. Self-extinguishing urea-formaldehyde foams if the country regulations authorize them.

Industry o

Soundproofing of pumps, refrigerating units; insulation sleeves for vapour piping in melamine foam.

Automotive and transport 9 Ashtrays in melamine. 9 Hood and transmission soundproofing in melamine foam. o Soundproofing laminate in melamine foam with aluminium foils, nonwovens or fabrics.

Fibre o

BASF has developed a heat and flame resistant fibre "Basofil", which is actually produced by MLM.

Soundproofing 9

Multilayer composites such as melamine foam/PVC sheet/melamine foam acting as sound blocker and sound absorber. 241

Thermosets and Composites

A m o n g the applications that are outside the framework of this book, but which represent significant consumption, are: 9 Adhesives and binders for laminate containing paper or wood such as Formica, plywoods. Only the external faces can be in melamine, which has a more beautiful aspect but is more expensive, whereas the inner mass is in urea-formaldehyde resin. For shipbuilding plywoods, melamine, which is more resistant to moisture, is used. 9 The melamines are also used as binders for the foundry sands and the abrasive powders for the abrasive grinding stones and papers. 9 The melamines are used as varnishes for the IMC process (in mould coating) to decorate the SMCs. 4.4.2 Thermal behaviour Initial behaviour

The H D T A (1.8 MPa) range from: 9 110 ~ to >200 ~ for melamines. 9 120-220 ~ for unsaturated polyester modified melamines. 9 140-220 ~ for phenolic modified melamines. 9 110-145 ~ for urea-formaldehydes. The heat property retentions are generally acceptable, for example: 9 A given melamine retains 65% of its flexural modulus at 120 ~ 9 A n o t h e r reinforced glass fibre V0 grade retains 47% of its flexural modulus at 240 ~ The curve in Figure 4.15 shows an example of modulus retention according to the temperature for a glass fibre reinforced V0 grade.

Figure 4.15. Glass fibre reinforced melamine: example of modulus retention versus temperature

These results relate to a few grades only and cannot be generalized. 242

Detailed accounts of thermoset resins for moulding and composite matrices

Long-term behaviour

The continuous use temperatures in an unstressed state range from: 9 80-150 ~ for melamines 9 70-100 ~ for urea-formaldehydes. Typical U L temperature indices are: 9 130-150 ~ for melamines 9 150 ~ for phenolic modified melamines 9 100 ~ for urea-formaldehydes. For short durations, service temperatures can be much higher. Low temperature behaviour

The resistance to cold impact can pose problems for temperatures such as -50 ~ but for many grades the notched impact resistance does not vary significantly between 20 ~ and -40 ~ For the melamine foam a - 6 0 ~ low temperature service is claimed. 4.4.3 Optical properties These materials are inherently transparent with, as an example, a refractive index of 1.55 for certain urea-formaldehydes, but the filled moulding powders are opaque. 4.4.4 Mechanical properties Mechanical properties are generally fair with acceptable heat performance retentions. Moduli, hardnesses, abrasion and scratch resistances are generally high but depend on the fillers and modifiers. Elongations at break are weak. Certain grades can have a tendency to crack, especially in the event of overcure. Friction

Melamines and urea-formaldehydes are not particularly intended for the realization of friction parts. Dimensional stability

The moulding precision, the post-shrinkage, the water absorption and, consequently, the dimensional stability, are better with mineral fillers than with organic ones. The post-moulding shrinkage can be neutralized by a postcure. 4.4.5 Ageing Weathering

Generally, melamines behave acceptably although there can be a slight attack. The urea-formaldehydes are sensitive to moisture and therefore melamines are preferable for outside use. 243

Thermosets and Composites

Chemicals

Resistance to water is clearly better for melamines than for ureaformaldehydes making them more desirable for shipbuilding plywoods. The behaviour with dilute bases and weak acids is generally good though strong bases and acids attack them. The behaviour with organic products is generally acceptable, with good resistances to aliphatic and aromatic hydrocarbons, chlorinated solvents, acetone, ethanol, esters, ethers. Table 4.30 gives some general indications, which would have to be verified by consultation with the producer of the selected grades and by tests under operating conditions. Table 4.30

Melamines: chemical behaviour examples

Product

Time, days

Level, %

Temperature,~

Swelling, % Tensileproperty retention

Acetic acid

365

5

20

1

Acetone

365

100

20

2

Acetone

30

100

20

0

Benzene

365

100

20

2

Carbon tetrachloride

365

100

23

1

Dichloroethane

365

100

20

1

Ethanol

365

90-100

20

1

Ethylacetate

365

100

20

2

Heptane

365

100

23

1

Hydrochloric acid

365

8-10

20

9

Motor oil

365

100

23

1

Nitric acid

365

10

23

13

Oleic acid

365

100

23

1

Sodium hydroxide

365

10

23

2

Sulphuric acid

365

35

23

19

Toluene

365

100

23

1

Water

365

100

20

3

0

Fire resistance

Generally, fire behaviour is acceptable. Many grades are U L 94 V0 classified, sometimes for a thickness as low as 0.25 mm. The oxygen indices often range from 38 to 45 or even much more, for example 95, but are weaker with combustible fillers like cotton. 244

Detailed accounts of thermoset resins for moulding and composite matrices

Thermosets, being infusible, do not drip while burning. In a fire situation, melamine resins produce a relatively low amount of smoke at a relatively low level of toxicity. 4.4.6 Electrical properties

The electric applications are numerous, due to the good insulating properties, the arc resistance and the fire ratings. Melamines and urea-formaldehydes remain insulating, especially for the mineral filled grades, after exposure to moisture or water, as the following figures illustrate: 9 Resistivity after 24 hours water immersion: >108 to >10 l~ . Dielectric constant, 1 kHz after 4 days at 20 ~ 85 % RH: 6- 20 9 Loss factor, 1 kHz after 4 days at 20 ~ 85% RH: <0.1 to <0.5 Hygroscopic fillers are detrimental to the insulating properties. The dielectric losses involve the HF-heating.

4.4.7Joining Welding and joining with solvents are useless as for all the thermosetting resins. Adhesives, following rigorous tests, allow joining. The parts should not be subjected to high stresses. After cleaning by abrasion and/or with solvent, the parts can be stuck with adhesives whose performances are compatible with the operating conditions. 4.4.8 Foams

Unlike the usual industrial dense polymers, which are processed as carefully as possible while avoiding the formation of bubbles, vacuoles etc., the alveolar materials (foams) result from the desire to introduce, in a controlled way, a certain proportion of voids with the aim of improving the thermal or phonic insulating character. The alveolar materials consist of a polymer skeleton surrounding the cells, which may be closed or partially or completely open to neighbouring cells or the outside. The intrinsic properties ensue from those of the melamine with" e A reduction in the mechanical properties due to the small quantity of material and the high proportion of gas. 9 A reduction in the chemical resistance due to the highly divided nature of the material. The thin cell walls immediately absorb liquids and gases and are rapidly damaged. Table 4.31 shows that the acid resistance of the foam is lower than that of the solid melamine. 245

Thermosets and Composites

Table 4.31

Melamine foams: characteristic examples

Density

kg/m 3

8.5-11.5

Continuous use temperature

~

150

Thermal conductivity at 10 ~

W/m.~

<0.035

10% compression stress

MPa

0.005-0.020

Compression strength (at 40%)

MPa

0.007-0.020

%

10-30

MPa

> 0.120

%

>10

Compression set after 72 h, 50 % compression, 23 ~ Tensile strength Elongation at break Non-aggressive chemicals after 28 days at room temperature

Aliphatic and aromatic hydrocarbons such as fuel, toluene. Alcohols such as methanol, ethanol, butanol; ethyletherglycol, glycerine. Acetone, butylacetate, diethylether.

Aggressive chemicals after 28 days at room temperature

10% and more mineral acids. Some diluted or concentrated organic acids.

A flexible foam with open cells was developed for its soundproofing and thermal qualities. Its very low density, flexibility, good acoustic absorption qualities, good thermal stability and natural fire resistance characterize it. Table 4.31 presents an example of the properties. These foams can be: 9

Processed by hot moulding, cutting, milling.

9

Laminated with non-woven material, fabric, aluminium foil by joining, pasting.

4.4.9 Specific ISO standards concerning amino resins

ISO 4614:1977 Plastics - Melamine-formaldehyde Determination of extractable formaldehyde ISO4896:1990 P l a s t i c s Specification

mouldings

-

Melamine/phenolic moulding m a t e r i a l s -

ISO 11402:1993 Plastics - Condensation resins - Determination of free formaldehyde ISO 14527-1:1999 P l a s t i c s - Urea-formaldehyde and urea/melamineformaldehyde powder moulding compounds (UF- and U F / M F - P M C s ) Part 1: Designation system and basis for specifications ISO 14527-2:1999 P l a s t i c s - Urea-formaldehyde and urea/melamineformaldehyde powder moulding compounds (UF- and U F / M F - P M C s ) Part 2" Preparation of test specimens and determination of properties 246

Detailed accounts of thermoset resins for moulding and composite matrices

ISO 14527-3:1999 Plastics- Urea-formaldehyde and urea/melamineformaldehyde powder moulding compounds (UF- and UF/MF-PMCs)Part 3: Requirements for selected moulding compounds ISO 14528-1:1999 Plastics- Melamine-formaldehyde powder moulding compounds (MF-PMCs) - Part 1: Designation system and basis for specifications ISO 14528-2:1999 Plastics- Melamine-formaldehyde powder moulding compounds (MF-PMCs) - Part 2: Preparation of test specimens and determination of properties ISO 14528-3:1999 Plastics- Melamine-formaldehyde powder moulding compounds (MF-PMCs) - Part 3: Requirements for selected moulding compounds ISO 14529-1:1999 P l a s t i c s - Melamine/phenolic powder moulding compounds (MP-PMCs) - Part 1: Designation system and basis for specifications ISO 14529-2:1999 P l a s t i c s - Melamine/phenolic powder moulding compounds (MP-PMCs) - Part 2: Preparation of test specimens and determination of properties ISO 14529-3:1999 P l a s t i c s - Melamine/phenolic powder moulding compounds (MP-PMCs) - Part 3: Requirements for selected moulding compounds ISO 15373:2001 Plastics- Polymer dispersions- Determination of free formaldehyde 4.4.10

Trade n a m e

examples

Melamines: Bakelite MF and MP, Basofil, Basotect, Isom6ca, Melopas, Melwite, Remel, Resart, Ultrapas MA and MZ. Urea-formaldehyde: Bakelite UF, Basopor, Pollopas, Rutaphen, Ultrapas HZE. 4.4.11 Property tables

The following results in Tables 4.32 to 4.35 relate to examples only and cannot be generalized. See also Table 4.31. Table 4.32

Melamines: characteristic examples

Filler

Mineral

Glassfibre

1.7-2

1.5-2.1

1.5-1.7

1.5-1.7

Shrinkage, %

0.3-0.6

0.1-0.6

0.5-1.3

0.5-1.3

Water absorption, %

0.1-0.2

Density, g/cm 3

Shore hardness, D Barcol hardness

Cellulose

Woodflour

0.1-0.8 95 70-80 247

Thermosets and Composites

Table 4.32

Melamines: characteristic examples

Filler

Mineral

Ball indentation hardness, MPa

250-480

Glassfibre

Cellulose

Woodflour

250-410

230-320 40-80

Tensile strength, MPa

20-40

35-70

30-90

Elongation at break, %

0.3-0.5

0.6-1.5

0.6-1

Tensile modulus, GPa

10-13

Flexural strength, MPa

70-90

Flexural modulus, GPa

10-13

7-11

10-11

60-180

80-130

70-120

11-20

8-10

8-9

250-300

250-300

1.3-2

1.3-2

Compression strength, MPa Notched impact, kJ/m 2 Ratio modulus 120 ~

1.5-2 ~

%

57

HDT B (0.46 MPa), ~

66 180- >210

190-210

HDT A (1.8 MPa), ~

150-200

170-310

120-210

140-180

Continuous use temperature, ~

110-150

130-160

80-130

80-130

0.3-0.5

0.4-0.5

Thermal conductivity, W/m.K

0.7

Specific heat, cal/g/~ Coefficient thermal expansion, 10-5/~ Resistivity Dielectric constant Dissipation factor, 10.4 Dielectric strength, kV/mm Arc resistance, s

0.4 1-4 1011-1013

3-5

1010--1012 1010-1013

6-11

4-5 1010-1012

7-10

7-9

400-1700

100-500

100-3000

1,000-3000

14-16

14-29

12-20

15-20

120-200

140-180

110-140

115-125

40-95

42-45

38-41

V0

HB to V0

V0

Oxygen index, % UL94 fire rating

1-3

V0

General chemicalproperties Light

Possible slight attack

Weak acids

Fair to limited resistance

Strong acids

Attack

Weak bases

Fair resistance

Strong bases

Attack

Organic solvents

Generally good behaviour with aliphatic, aromatic, chlorinated solvents, acetone, ethanol, esters, ethers

Food contact

Possible for specific grades

248

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.33

Phenolic modified melamines: Characteristic examples

Filler

Woodflour

Cellulose Organic& inorganic Organic

Density, g/cm 3

1.5-1.7

1.5-1.7

1.5-1.7

1.5-1.7

Shrinkage, %

0.4-1.2

0.5-1.3

0.5-1.4

0.5-1.4

Ball indentation hardness, MPa

250-300

250-300

250-300

40-80

45-85

40-60

40-55

0.9-1.1

0.4-0.8 6-8

Tensile strength, MPa Elongation at break, % Tensile modulus, GPa

10-11

10-11

7-8

Flexural strength, MPa

80-135

90-130

90-110

Flexural modulus, GPa

7-9

7-9

6-8

200-250

200-250

150-200

1.5-2

1.5-2

1.5-2.7

HDT B (0.46 MPa), ~

190-220

190-210

220-240

HDT A (1.8 MPa), ~

160-180

160-180

180-220

140-150

Continuous use temperature, ~

80-130

80-130

110-140

80-150

Thermal conductivity, W/m.K

0.4-0.6

0.4-0.6

0.6-0.7

0.3-0.4

Compression strength, MPa Notched impact, kW/m2

Specific heat, cal/g/~

1.5-2

0.3-0.4

Coefficient thermal expansion, 10-5/~ Resistivity

6-8

3-5

3-4

101~

Dielectric constant

1010-1012

1-4

1-4

1010-1012

7-9

7-9

5-8

5-8

1000-3000

1000-4000

200-1500

200-600

15-25

15-20

8-30

8-13

Arc resistance, s

115-130

125-135

Oxygen index, %

38-41

42-45

35-40

UL94 fire rating

V0

V0

V0

Dissipation factor, 10-4 Dielectric strength, kV/mm

130-180

General chemicalproperties Light

Possible slight attack

Weak acids

Fair to limited resistance

Strong acids

Attack

Weak bases

Fair resistance

Strong bases

Attack

Organic solvents

Good behaviour with aliphatic, aromatic, chlorinated solvents, acetone, ethanol, esters, ethers

249

Thermosets and Composites

Table 4.34

Filled unsaturated polyester modified melamines: characteristic examples

Density, g/cm 3

1.7-1.9

Shrinkage, %

0.1-1

Ball indentation hardness, MPa

150-350

Tensile strength, MPa

45-55

Elongation at break, %

0.6-0.8

Tensile modulus, GPa

9-10

Flexural strength, MPa

60-110

Flexural modulus, GPa

9-11

Notched impact, kJ/m 2

2-3

HDT B (0.46 MPa), ~

220-250

HDT A (1.8 MPa), ~

120-220

Continuous use temperature, ~

110-140

Resistivity

1010-1014

Dielectric constant

6-7

Dissipation factor, 10-4

500-1500

Dielectric strength, kV/mm

20-25

Arc resistance, s

120-130

UL94 fire rating

HB to V0

Table 4.35

V0 cellulose filled urea-formaldehyde moulding powder: characteristic examples

Density, g/cm 3

1.5

Shrinkage, %

0.9-1.1

Water absorption, %

0.4-0.8

Ball indentation hardness, MPa

260-350

Tensile strength, MPa

30-40

Elongation at break, %

0.5-1

Tensile modulus, GPa

6-10

Flexural strength, MPa

80-100

Flexural modulus, GPa

6-10

Compression strength, MPa

>200

Notched impact, kJ/m 2

1.3-2

HDT A (1.8 MPa), ~ Continuous use temperature, ~

250

110-145 70-80

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.35

V0 cellulose filled urea-formaldehyde moulding powder: characteristic examples

Thermal conductivity, W/m.K

0.3-0.4

Specific heat, cal/g/~

0.4

Coefficient thermal expansion, 10-5/~

3-5

Resistivity

10 l~

Dielectric constant

6-10

Dissipation factor, 10-4

200-<1,000

Dielectric strength, kV/mm

12-16

Arc resistance, s

80-150

UL94 fire rating

V0

Generalchemicalproperties Water

More sensitive to water, hot in particular, than melamines

Light

Possible slight attack

Weak acids

Fair to limited resistance

Strong acids

Attack

Weak bases

Fair resistance

Strong bases

Attack

Organic solvents

Good behaviour with aliphatic, aromatic, chlorinated solvents, acetone, ethanol, esters, ethers

Food contact

No

4.5 Epoxides or epoxy resins (EP) The epoxy resins are obtained by reaction of a multi-epoxy monomer and a diamine or anhydride hardener. The multi-epoxy monomers are often diepoxy. The most up-to-date one is D G E B A but D G E B D is also used. The tri- or tetra- epoxy, T G A P or T G M D A for example, and some phenolic novolac resins reacted with epichlorhydrin are used for high performance composites. The hardeners are often aliphatic, cycloaliphatic or aromatic diamines and more rarely anhydrides. Generally: 9 The aliphatic amines lead to low curing temperatures and low glass transition temperatures. 9 The aromatic amines lead to higher curing temperatures and higher glass transition temperatures. The various types of epoxy monomers, the nature of the hardener and the versatility of the recipes provide diverse chemical natures, forms, processes and properties. 251

Thermosets and Composites

The epoxides can be: 9 Liquid resins for wet lay-up, casting, repairing... 9 Solid resins used in solution for making prepregs. The processing conditions are varied: 9 One or two components 9 Hot or room-temperature curing 9 With or without post-cure. 4.5.1 General properties

The property range is very broad and it is not possible to make a rigorous classification. As an example, the continuous use temperature can vary from 70 ~ up to 200 ~ in the extreme cases. The following information will inevitably be general and, unless otherwise specified, will relate to the most current grades. Advantages

Good mechanical properties, broad range of moduli, good thermal resistance of certain grades, resistance to numerous organic solvents and other chemicals, good electrical properties, aptitude for adherence on a large variety of substrates, good high-energy radiation behaviour, selfextinguishing grades, food contact grades, possibility of transparency, diversity of the processing methods some of which are easy to use, capacity for the manufacture of high-performance composites. Drawbacks

Often long and energy-expensive production cycles, health & safety considerations during manufacture, relatively high prices justified by the properties, limited heat resistance for certain grades, risks of chalking during light exposure. Special grades

Liquid, one or two components, cold or hot curing, with or without postcure; cast, compression, transfer or injection moulding; impregnation, stratification, filament winding, encapsulation, coating, varnishing; syntactic foams, prepregs; for electronics, tools, repairs...Transparent, food contact, fireproofed, flexible, high heat resistance, expandable. Cost

Generally, the costs are of the order of a few euros to more than 4920 per kilogram. Processing

The epoxies can be mono or bi-component, hot or cold curing with possibly a postcure. 252

Detailed accounts of thermoset resins for moulding and composite matrices

The main processing methods are: compression, transfer, injection mouldings, casting, putting, encapsulation, impregnation, stratification, filament winding, machining, varnishing, powdering.

Applications [see Chapter 2 for further information] Consumption The epoxy resin consumption by the industrialized countries accounts for 4-6% of the total for thermosets and is approximately 0.7-0.8% of the total plastics consumption. The consumption growth roughly follows or slightly exceeds the rate for plastics consumption overall. The main application markets are anticorrosive and protective coatings, composites and reinforced resins for electricity, flooring and concretes, composites and reinforced resins for various uses. The applications are always technical. Examples of operational or development parts are listed below.

Anti-corrosive, anti-wear, protection properties 9 Conduits, tubes for desulphurization installations; support profiles and coatings for digester vats; flues up to 180 ~ piping for chemical and oil industry; tubes for the transport of matter in suspension; fire protection networks for oil rigs; water piping for nuclear or thermal power stations; cooling pipes for frozen water. 9 Long winding conduits for oil prospecting; lining for rehabilitation of conduits without trenching; proofing varnishes; inner coatings for tanks, vats and other containers. 9 Enamelling of household appliances; electrostatic powdering or fluidized bed coating.

Aeronautical, space, armaments 9 External kerosene tanks for helicopters; cryogenic tanks for rockets; breakable cap of the Aster container, flaps for supersonic civil transport aircraft; transmission rods, drifts, wing structural elements for civil aircraft; aeronautical careenages, plane wheels; propellers for military or civil transport aircrafts; carrying pylons for fighters; salmons for propeller blade tips; coatings of helicopter blades, arms of centrifugal machine for pilot training. 9 Tank travelling wheels, electronic cases of missile launchers, components for unmanned aircraft; electronic device boxes for shooting stations.

Electricity, electronics 9 Parabolic aerial elements, 15 m diameter parabolic antenna. 9 High-voltage insulator tubes for power lines; power semiconductor boxes, transformer rings, SF6 circuit breakers, coil supports, high253

Thermosets and Composites

voltage insulators, fireproofed panels, bending hoops for ferrosilicon sheets of transformers; overmoulding of coils. Simple, 2D or 3D printed circuit boards, encapsulation of LED and other electric and electronic elements, frames of solar panels. Impregnation of electric and electronic devices such as terminal plates, motors, transformers; capacitor and other component coatings.

Automotive 9 9 9 9

Drive shafts, wishbone suspensions for rally cars; laminated springs for utility, 4WD cars, sports cars. F1 hulls, sports car bodies, frame-hulls for amphibious vehicles. Coupling for trailers or caravans; insulation of ignition system for top-of-the-range cars. Experimental engine.

Building, furniture 9

9 9 9 9

Reinforcement of existing concrete structures, stiffener plates to increase the performance of existing buildings or construction works; repairs of metal offshore oil rig structures by plate stiffeners. Fireproofed panels, outside and inside sandwich panels for building; frontages for airports, hospitals. Rehabilitation of conduits without digging trenches by the use of uncures soft tubes. Rods and cables for securing TV antennae, cables for pre-stressed concrete. Contemporary furniture: beds, tabletops, cupboards, bedside tables.

Sports, shipbuilding, water sports 9 9 o 9 9

Roofs and central hulls of race trimarans, 25 m race monohulls, sailboards and race boats. Ballasts and ballasting pipes for ships; piping and water tanks for fire safety systems of oilrigs. Suspension arms, 3-ray wheels for high-tech bicycles. Tent hoops and poles. Elements for submarines: acoustic transparency, vibration damping, reduced maintenance.

Medical, health 9 9 9 9 9 254

Adhesives, possibly conductive or transparent. Pacemaker coatings. Dental prostheses, artificial teeth for dentists' training. Vascular system naturalization of the kidneys by resin injection. Spectacle frames.

Detailed accounts of thermoset resins for moulding and composite matrices

Tools 9 Moulds for hand lay-up moulding of glass fibre reinforced unsaturated polyester, resin concretes, syntactic paste for rapid tooling system (Vantico/Boeing process), sealing. 9 Machine frames, base plates, fixings. Glue and adhesives 9 Industrial adhesives, possibly conductive or transparent. 9 Medical adhesives: biocompatible and sterilizable bi-component. Miscellaneous 9 0.5 to 1000 litre tanks for LPG, compressed air. 9 Cable car bodies and arms for cable transport. 9 Surrounding joint of honeycomb structure in epoxy paste. 9 Sculptures by Delfino and other sculptors. 4.5.2 Thermal behaviour

For all the properties it is necessary to remember the versatility of epoxies. Initial behaviour

The H D T A (1.8 MPa) range from: 9 45 ~ for neat flexible grades. 9 To 300 ~ for composites or high-filled grades such as those based on aluminium powder for tool making. Typical glass transition temperatures range from 90 ~ to 140 ~ but can reach temperatures as low as 0 ~ or as high as 150 ~ ~ The property retention when the temperature rises is generally acceptable but depends on the matrix, the nature and level of fillers and reinforcements, and the type of property. As examples, for various grades: 9 70% modulus retention at 120 ~ 9 67% compression strength retention at 121 ~ 9 54% flexural strength retention at 149 ~ 9 49% flexural modulus retention at 149 ~ Long-term behaviour

The continuous use temperatures in an unstressed state generally vary from 70 ~ up to 200 ~ As an indication, though numerous exceptions exist, we give an arbitrary classification of the continuous use temperatures according to the manufacturing process: 9 Cold cast without postcure" 70-90 ~ 9 Cold cast with postcure: 90-120 ~ 9 Hot cast: 110-!70 ~ 9 Moulding: 110-200 ~ 255

Thermosets and Composites

Higher temperatures can be withstood for shorter times, especially for the heat-resistant grades. The peak service temperatures are up to 280 ~ The UL temperature indices of specific grades range from 90 ~ to 170 ~ for the electrical and mechanical properties, including impact. Generally: 9 Liquid resins and coating powders range from 90 ~ to 130 ~ 9 Moulding powders and SMCs range from 130 ~ to 170 ~ Figure 4.16 shows, for a high heat-resistant grade, an example of the lifespan for a 70% flexural strength retention versus temperature. The 25 000 hour-service temperature is approximately 160 ~ ~

Figure 4.16. Heat resistant epoxide: example of lifespan for 70% flexural strength rentention versus temperature

Figure 4.17 shows, for a higher heat-resistant grade, an example of the half-life (50% of tensile strength retention), plotted as the natural log, versus the inverse of the absolute temperature (T) multiplied by 1000. The results are correctly simulated by an Arrhenius law with a predicted 25 000 hour-service temperature of approximately 202 ~

Figure 4.17. Epoxide: example of LN(half-life in days) versus IO00/T en ~ 256

Detailed accounts of thermoset resins for moulding and composite matrices

These results only relate to the tested highly heat-resistant grades and cannot be generalized. Some epoxides can thus be classified among the thermostable polymers but other grades cannot. Low temperature behaviour

The typical glass transition temperatures range from 90 ~ to 140 ~ but can reach temperatures as low as 0 ~ or as high as 150 ~ ~ According to the grade and the operating conditions, the service low temperatures range f r o m - 5 0 ~ ~ to cryogenic temperatures. These results relate to a few grades only and cannot be generalized. 4.5.3 Optical properties

Transparent grades are marketed with refractive indexes in the 1.5 to 1.6 range. They are used in special applications such as: 9 Electronics: visual monitoring of encapsulated components. 9 Medical: adhesives. , Optics: transparent joining or coating of quartz, glass or plastics components (optical fibre). 4.5.4 Mechanical properties

The mechanical properties are generally good: tensile strength, high tear and abrasion resistances. However, some grades whose other characteristics are optimized can have relatively weak mechanical properties. Rigidities and hardnesses are extremely variable allowing a vast choice from highly flexible to rigid. The epoxy composites occupy the place of choice for highly technical applications: aeronautics and space for example. If the most current grades have Shore hardnesses higher than 80D, the flexible ones can go down to 60D, whereas certain transparent resins have hardnesses comparable with those of plasticized P V C - 60 Shore A, for example. The retention of the properties at elevated temperature is often acceptable. Friction

Generally, epoxides are not used for the friction parts. Creep

Creep is highly dependent on the matrix, reinforcements and load. Generally, creep is very suitable for the grades intended for mechanical applications. For a given glass fibre reinforced epoxy composite, the strain is 2% after 1000 hours at 120 ~ under a 21 MPa load, that is, a 1 GPa modulus. 257

Thermosets and Composites

Figure 4.18 gives two examples of creep curves for moulding powder parts for the electric industry. The load is unknown.

Figure 4.18. Epoxide: example of creep versus time at 20 ~ and 80 ~

For another grade, a silica-filled epoxy resin, the creep moduli under a 23 MPa tensile loading are plotted on the graphs of Figure 4.19. The initial instantaneous modulus is 10 GPa.

Figure 4.19. Epoxide: example of creep modulus versus time at 23 ~ and 85 ~

After 10 hours, creep moduli are correctly simulated versus time by logarithmic equations: 9 At 23 ~ creep modulus =-0.5081 * In(time in hours) + 9.05 9 At 85 ~ creep modulus = -0.4473 * In(time in hours) + 5.5 These results relate to few grades only and cannot be generalized. 258

Detailed accounts of thermoset resins for moulding and composite matrices

Dimensional stability The shrinkage is generally limited, the coefficients of thermal expansion are often moderate or low, the creep is fair to good, and the alterations by heat and moisture exposure are limited, as the following examples show for a specific moulding compound for electric applications: 9 5.0% weight loss after 5000 hours at 180 ~ 9 0.3% length change after 3000 hours at 180 ~ 9 0.1% length change after 3000 hours at 40 ~ and 98% RH. These results relate to a few grades only and cannot be generalized.

4.s.s Ageing

Dynamic fatigue Composites with suitably selected epoxy matrices have a good dynamic fatigue behaviour, allowing their use in aeronautics and automotive structural parts: suspensions, drive-shafts... Figure 4.20 presents two examples of SN (maximum stress in MPa versus number of fatigue cycles) curves.

Figure 4.20. Epoxide dynamic fatigue: examples of SN curves. Maximum stress versus cycle numbers

For this example, in the tested measurement domain, the SN curves are correctly simulated versus time by logarithmic equations as suggested by ASTM D671: 9 Maximum stress =-6.167 * In(cycles) +240.6 9 Maximum s t r e s s - - 6 . 5 1 4 4 * In(cycles) +220 For a glass fabric reinforced epoxy composite, the fatigue resistance is notably different, as the SN curve of Figure 4.21 shows. 259

Thermosets and Composites

Figure4.21. Glassfabricreinforcedepoxycomposite:Exampleofdynamicfatigue'SNcurveslnaximum stress versus cycle numbers

For this example, in the tested measurement domain, the SN curve is correctly simulated versus time by logarithmic equations: 9 Maximum stress =-30.557 * In(cycles) +542.03 These results relate to a few grades only and cannot be generalized.

High-energy radiation

Certain epoxies have good resistance to high-energy radiation. For example, the properties of a given grade are still suitable after 500 MRad exposure to gamma rays. This is an example only and it should not be generalized.

Chemicals

Resistance to water is generally good, allowing use as a matrix for composites intended for the manufacture of pipes for district heating networks. The behaviour with weak acids and bases is generally good, but there is a greater or lesser risk of attack by the strong acids and bases. Behaviour with organic materials is generally good, with exceptions such as ketones and certain chlorinated solvents. Table 4.36 displays some results concerning general assessments, aspect and weight change percentages after immersions for one month to more than one year at ambient temperature for given grades, which are not necessarily representative of all the epoxies. 260

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.36

Epoxies: examples of chemical behaviour at room temperature

Duration, days

Conc.,%

Acetic acid

Long

10-15

Acetic acid

365

10

Acetone

Long

100

Acetone

90

Estimated Swelling,% Aspect behaviour 1 to S No ch. n 1-1.3

Acetonitrile

Long

100

n

Acetyl chloride

Long

100

1

Alcohols

Long

100

1

Aluminium chloride

Long

Solution

S

Aluminium sulphate

Long

Unknown

S

Ammonium hydroxide

Long

10

S

Ammonium hydroxide

Long

30

1

Ammonium sulphate

Long

50

S

Amyl acetate

Long

100

1

Antimony chloride

Long

10

S

ASTM1 oil

Long

100

S

ASTM2 oil

Long

100

S

ASTM3 oil

Long

100

S

Barium chloride

Long

Saturated

S

180

100

n

Benzyl chloride

Long

100

1

Bromine liquid

Long

100

n

Butanol

Long

100

1

Butyl acetate

Long

100

1

Calcium chloride

Long

Unknown

S

Carbon sulphide

Long

100

1

180

100

S

Cellosove acetate

Long

100

n

Chlorinated solvents

Long

100

1

Chlorobenzene

Long

100

1

Chloroform

Long

100

1

Chromic acid

Long

Unknown

n

Citric acid

Long

Benzene

Carbon tetrachloride

10

1

1

No ch.

S 261

Thermosets and Composites

Table 4.36

Epoxies: examples of chemical behaviour at room temperature

Duration, days

Conc.,%

Copper sulphate

Long

Unknown

S

Cyclohexane

Long

100

S

Cyclohexanol

Long

100

S

90

100

Dichloroethylene

Long

100

n

Diethyl amine

Long

100

n

Diethyleneglycol

Long

100

S

Dimethylformamide

Long

100

n

Dioctylphtalate

Long

100

S

Dioxan

Long

100

1

Ethanol

Long

96

S

Ethanol

Long

Unknown

1 to S

Ethanol

180

90-100

Dichloroethane

Estimated Swelling,% Aspect behaviour

1

1

Ethyl acetate

180

100

n

Ethyl chloride

Long

100

n

Ethylene glycol

Long

100

1

Ethylene glycol 93~

Long

Unknown

n

Fluorine

Long

100

n

Formaldehyde

Long

37

S

Freon 11

Long

100

1

Freon 113

Long

100

1

Freon 115

Long

100

1

Freon 12

Long

100

1

Freon 13bl

Long

100

1

Freon 21

Long

100

1

Freon 22

Long

100

1

Freon 32

Long

100

1

Fuel

Long

100

1

Furfural

Long

100

n

Glycerol

Long

100

S

Heptane

180

100

Hexane

Long

100

262

1

1 S

No ch.

No ch.

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.36

Epoxies: examples of chemical behaviour at room temperature

Duration, days Hydraulic oil

Conc.,%

Estimated Swelling,% Aspect behaviour

30

0.1-0.2

Hydrochloric acid

180

6-10

S

Hydrochloric acid

Long

37

1 to S

Hydrogen peroxide

Long

30

1

Iron(III) chloride

Long

Unknown

S

Isooctane (fuel a)

Long

100

S

Isopropanol

30

Isopropanol

Long

100

S

30

Lactic acid

Long

90

S

Lead acetate

Long

10

S

Magnesium chloride

Long

Unknown

S

Mercury chloride

Long

Unknown

S

Methanol

Long

100

1

Methylene chloride

Long

100

n

Methyl ethyl ketone

Long

100

n

Methyl ethyl ketone

30

Motor oil Nickel chloride

Long

0.1-0.2

1-0.2 100

S

180 Long

1 Unknown

No ch.

S

Nitric acid

90

10

Nitric acid

Long

75

n

Nitrobenzene

Long

100

n

Oleic acid

180

100

S

Oxalic acid

Long

Unknown

S

Paraffin oil

Long

100

S

Perchloroethylene

Long

100

1

Petrol

Long

100

S

Phenol

Long

Unknown

n

365

35

Phosphoric acid

No ch.

0.2-0.3

Kerosene

Mineral oil

1

1

1

No ch.

No ch.

Potassium cyanide

Long

Unknown

S

Potassium fluoride

Long

Unknown

S 263

7 hermosets and Composites

Table 4.36

Epoxies: examples of chemical behaviour at room temperature

Duration, days

Conc.,%

Estimated behaviour

Potassium hydroxide

Long

45

S

Potassium sulphate

Long

Unknown

S

Propanol

Long

100

S

Propionic acid

Long

100

1

Pyridine

Long

Unknown

n

Sea water

Long

100

S

Silver nitrate

Long

Unknown

S

Unknown

S

Skydrol

30 Long

Sodium carbonate

Long

10

1

Sodium chloride

Long

25

S

Sodium cyanide

Long

Sodium hydroxide

Long

10

Sodium hydroxide

90

10

Sodium hydroxide

Long

55

Sodium nitrate

Long

Styrene

Unknown

S 1 1

Unknown

S 1

Long

100

180

c. 20

Sulphuric acid

Long

10

S

Sulphuric acid

Long

96

n

Sulphuric acid

180

35

Long

100

90

100

Trichloroethylene

Long

100

n

Triethanolamine

Long

Unknown

S

Triethylamine

Long

Unknown

S

Vegetable oil

Long

100

S

365

100

Water 100~

Long

100

S

White spirit

Long

100

S

Zinc chloride

Long

Unknown

1

Water

1

1 1 1

1

S: satisfactory; 1: limited; n: not satisfactory Long: the duration is undefined but is of the order of years; No ch.: no change 264

No ch.

S

Sulphuric acid

Toluene

Aspect

-0.2

Sodium borate

Tetrachloroethane

Swelling,%

No ch.

Detailed accounts of thermoset resins for moulding and composite matrices

Fire resistance

The oxygen indices are naturally low (26 for a mineral and glass fibre filled grade) with a HB U L 94 rating. The fireproofed formulas make it possible to reach, for example: 9 V0 in 1.6 mm thickness 9 An oxygen index of 45. 4.5.6 Electrical properties The electric applications are numerous, including high-voltage insulation. For the appropriate grades, the electrical properties remain stable across a broad range of temperatures, humidities and media. For example, for a given grade, no significant variations are observed for: 9 Arc resistances after 3000 hours at 40 ~ and 98% RH. 9 Dielectric rigidity and arc resistance after 180 days in a transformer oil. 9 A permittivity increasing from 6 to 8 after 1000 hours at 80 ~ and 95 % RH. Finally, electrolytic corrosion and sensitivity to cracking by overcuring are weak.

4.5.7Joining Welding and joining with solvents are useless as for all the thermosetting resins. Adhesives alone, chosen after rigorous tests, allow joining. The parts should not be subjected to high stresses. After cleaning by abrasion and with solvent, the epoxies can be stuck with epoxy adhesives, polyurethanes, cyanoacrylates or acrylic resins whose performances are compatible with the operating conditions. 4.5.8 Foamed epoxies and syntactic foams Slightly foamed epoxy resins are used for structural applications. Artificial balloons or spheres can be added to make syntactic foams. Structural foamed epoxies

Contrary to usual industrial solid polymers, which are processed as carefully as possible to avoid the formation of bubbles, vacuoles etc., the alveolar materials result from the desire to introduce, in a controlled way, a certain proportion of voids with the aims: 9 To reduce the part weight while preserving the structural properties. 9 To reduce the density. 9 To improve damping and insulating properties. These alveolar materials consist of a thick polymer skeleton surrounding a few closed cells. The density is slightly reduced. 265

Thermosets and Composites

The intrinsic properties ensue from those of the epoxide with: 9 A slight reduction in the mechanical properties due to the small fraction of gas. 9 A slight reduction in the chemical behaviour due to the slight division of the material. The cell walls absorb liquids and gases and are more rapidly damaged. Apart from the conventional applications, let us report a process developed by Core Products for the reinforcement of automotive structures. In this concept of structural foam, expandable preforms are installed in the metal hollow structures before painting. During the final cooking of the paints they expand and reinforce the structures to improve the impact classification. These foams can also contribute to the phonic damping. Syntactic foams

Syntactic foams are composites made up of micro-balloons or hollow macrospheres bound into a plastic matrix with properties that make them ideal for use in offshore exploration and production. Syntactic foams are used: 9 For insulation of offshore equipment. They have the ability to withstand use at ocean depths of 3000 m and beyond for 30 years. 9 In electronics equipment, where they act as structural parts, thermal barriers and dielectric materials for microwave and RF applications. Hollow macrospheres are made from glass or graphite fibre reinforced epoxy resins. 4.5.9 Specific ISO standards concerning epoxides Raw materials

ISO 3001:1999 Plastics - Epoxy compounds - Determination of epoxy equivalent ISO 3521:1997 P l a s t i c s - Unsaturated polyester and epoxy resins Determination of overall volume shrinkage ISO 3673-1:1996 Plastics- Epoxy r e s i n s - Part 1: Designation ISO 3673-2:1999 Plastics - Epoxy resins - Part 2: Preparation of test specimens and determination of properties ISO 4597-1:1983 P l a s t i c s - Hardeners and accelerators for epoxide resins - Part 1: Designation ISO 4615:1979 P l a s t i c s - Unsaturated polyesters and epoxide r e s i n s Determination of total chlorine content 266

Detailed accounts of thermoset resins for moulding and composite matrices

ISO4895:1997 P l a s t i c s - Liquid epoxy r e s i n s - Determination of tendency to crystallize ISO 7142:1984 Binders for paints and varnishes - Epoxy resins - General test methods ISO 7327:1994 Plastics- Hardeners and accelerators for epoxide resins Determination of free acid in acid anhydride ISO 9702:1996 Plastics - Amine epoxide hardeners - Determination of primary, secondary and tertiary amine group nitrogen content ISO 21627-1:2002 Plastics- Epoxy r e s i n s - Determination of chlorine c o n t e n t - Part 1: Inorganic chlorine ISO 21627-2:2002 Plastics- Epoxy r e s i n s - Determination of chlorine c o n t e n t - Part 2: Easily saponifiable chlorine ISO 21627-3:2002 Plastics - Epoxy resins - Determination of chlorine c o n t e n t - Part 3: Applications

ISO 3673-1:1996 Plastics- Epoxy resins- Part 1: Designation ISO 3673-2:1999 P l a s t i c s - Epoxy r e s i n s - Part 2: Preparation of test specimens and determination of properties ISO 14654:1999 Epoxy-coated steel for the reinforcement of concrete ISO 14655:1999 Epoxy-coated strand for the prestressing of concrete ISO 14656:1999 Epoxy powder and sealing material for the coating of steel for the reinforcement of concrete ISO 15252-1:1999 Plastics - Epoxy powder moulding compounds (EPPMCs) - Part 1: Designation system and basis for specifications ISO 15252-2:1999 Plastics- Epoxy powder moulding compounds (EPPMCs) - Part 2: Preparation of test specimens and determination of properties ISO 15252-3:1999 Plastics- Epoxy powder moulding compounds (EPPMCs) - Part 3: Requirements for selected moulding compounds

4.5.10 Trade name examples

Amoco epoxy, Araldite, Cytec epoxy, Devcon epoxy, Eccocoat, Eccolite, Epikote, Epon, Epotek, Neonite, Rezolin, Rogers epoxy, Rutapox, System Three, Tactix, Union Carbide epoxy.

4.5.11 Property tables

Tables 4.37 to 4.43 relate to examples only and cannot be generalized. 267

Thermosets and Composites

Table 4.37 Examples of moulding and cast epoxides: general properties Flexible for moulding

Neat EP for casting

1-1.4

1.1-1.4

0.1-0.8

0.1-0.4

Density, g/cm 3 Shrinkage, % Water absorption, 24 h, %

0.1-0.15

Tensile strength, MPa

10-70

20-90

Elongation at break, %

20-70

3-10

Tensile modulus, GPa

0.01-1.5

0.8-3

Notched impact D 256, J/m

124-270

Notched impact, kJ/m 2

20-30

Shore hardness, D

65-89

HDT A (1.8 MPa), ~

45-120

45-200

90

70-170

CUT unstressed, ~ Brittle temperature, ~

1-6

-80--55

Thermal conductivity, W/m.K

0.17

Specific heat, cal/g/~ Coefficient thermal expansion, 10-5/~ Volume resistivity, ohm.cm Dielectric constant Loss factor, 10-4

0.2-0.3

0.2-0.3

2-10

4-7

1012-1017

1012-1017

3.5-5

3-5

100-500

20-500

Dielectric strength, kV/mm

16-20

Arc resistance, s

45-190

UL94 fire rating

HB

HB

General chemical properties Light

Risk of surface chalking

Weak acids

Fair resistance

Strong acids

Risk of attack with certain acids

Weak bases

Fair resistance

Strong bases

Risk of slight attack

Organic solvents

Generally resistant with exceptions such as chlorinated solvents and ketones

Food contact

Possible

CUT: Continuous use temperature

268

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.38 Examples of epoxide matrices for composites: general properties

Type

120/140~

140/180~

Density, g/cm 3

1.1-1.4

1.1-1.4

1.1-1.4

Shrinkage, %

0.1-0.4

0.1-0.4

0.1-0.4

Water absorption, 24 h, %

0.1-0.15

0.1-0.15

0.1-0.15

Tensile strength, MPa

70-90

75-91

40-77

Elongation at break, %

5-13

5-7

1-6

Tensile modulus, GPa

3-4

3

2.5-3.2

Flexural strength, MPa

110-155

125-150

80-160

54-70

58-75

ILSS, MPa Notched impact, kJ/m 2

1-6

CUT unstressed, ~

70-120

100-140

110-170

Glass transition temperature, ~

70-136

122-155

143-225

0.17

0.17

0.17

0.2-0.3

0.2-0.3

0.2-0.3

4-7

4-7

4-7

1012-1017

1012-1017

1012-1017

20-500

20-500

20-500

16-20

16-20

16-20

45-190

45-190

45-190

Thermal conductivity, W/m.K Specific heat, cal/g/~ Coefficient thermal expansion, 10-5/~ Volume resistivity, ohm.cm Loss factor, 10-4 Dielectric strength, kV/mm Arc resistance, s General chemicalproperties Light

Risk of surface chalking

Weak acids

Fair resistance

Strong acids

Risk of attack with certain acids

Weak bases

Fair resistance

Strong bases

Risk of slight attack

Organic solvents

Generally resistant with exceptions such as chlorinated solvents and ketones

Food contact

Possible

CUT: Continuous use t e m p e r a t u r e

269

Thermosets and Composites Table 4.39

Examples of filled and reinforced moulding epoxides: general properties

Glassfibres

Glassfibres and mineralfillers

Long glassfibres

1.5-2

1.85-2

1.75

Shrinkage, %

0.1-0.8

0.2-0.8

0.1-0.4

Tensile strength, MPa

40-140

50-100

90

Elongation at break, %

<2

<1

<1

Flexural strength, MPa

50-200

80-160

180

Flexural modulus, GPa

10-30

10-18

16

Notched impact D 256, J/m

20-60

20-40

300

Rockwell hardness, M

100-112

100-112

HDT A (1.8 MPa), ~

120-260

120-250

150

CUT unstressed, ~

150-230

180-230

200

Reinforcement

Density, g/cm 3

140

Glass transition temperature, ~ Thermal conductivity, W/m.K Coefficient thermal expansion, 10-5/~ Volume resistivity, ohm.cm

0.2-0.5

0.6-1.2

0.5

1-4

1.8-3

2.8

1014-1015

1014-1015

1015

Dielectric constant

4.2-6.1

Dielectric strength, kV/mm

13-15

15

Oxygen index, %

26-45

32

Fillers

Mineral

Silica

Aluminium powder

Density, g/cm 3

1.1-2.3

1.6-2

1.4-1.8

Shrinkage, %

0.05-0.8

0.05-0.1

0.1-0.5

Water absorption, 24 h, %

0.1-0.5

0.04-0.1

0.1-3

Tensile strength, MPa

10-90

49-91

20-90

Elongation at break, %

0.5-4

1-3

0.5-3

Tensile modulus, GPa

2-8

Flexural strength, MPa

40-120

270

56-98

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.39

Examples of filled and reinforced moulding epoxides: general properties

Fillers Notched impact D 256, J/m

Mineral 20-50

Silica

Aluminium powder

16-24

Notched impact, kJ/m 2

1-10

Rockwell hardness, M

85-120

85-120

55-85

H D T A (1.8 MPa), ~

60-260

70-288

85-300

CUT unstressed, ~

70-170

100-170

90-200

0.4-0.8

0.6-1

2-4

0.5-0.6

Brittle point, ~ Thermal conductivity, W/m.K Specific heat, cal/g/~ Coefficient thermal expansion, 10-5/~ Volume resistivity, ohm.cm Dielectric constant

2-8

-80--55 0.2-1 0.2-0.5 0.6--6 1012-1017

<10

3-6

Loss factor, 10-4

80-900

> 1000

Dielectric strength, kV/mm

10-20

0.4-8

Arc resistance, s

50-300

UL 94 fire rating

HB to V0

Chemical behaviour: indicated general chemicalpropertiesare subject to the compatibility of thefillers and reinforcements with the ambient conditions. Light

Risk of surface chalking

Weak acids

Fair resistance

Strong acids

Risk of attack with certain acids

Weak bases

Fair resistance

Strong bases

Risk of slight attack

Organic solvents

Generally resistant with exceptions such as chlorinated solvents and ketones

Food contact

Possible

CUT: Continuous use t e m p e r a t u r e 271

Thermosets and Composites Table 4.40 Examples of unidirectional epoxide composites: general properties

Type of epoxide

180~

120~

Reinforcement

Carbonfibres

Carbonfibres

Reinforcement weight, %

65

65

65

65

Test direction

Parallel

Transverse

Parallel

Transverse

Density, g/cm 3

1.6-1.7

1.6--1.7

1.5-1.67

1.5-1.67

Tensile strength, MPa

1760-2840

30-80

1470-3040

30-76

Elongation at break, %

0.5-1.7

0.5-1

0.5-1.7

0.6-1

Tensile modulus, GPa

125-330

6-8

135-390

5-9

Flexural strength, MPa

910-1810

Flexural modulus, GPa

120-320

Compression modulus, GPa

125-320

Compression strength, MPa

780-1570

740-1570

ILSS, MPa Poisson's ratio CUT unstressed, ~ Thermal conductivity, W/m.K

70--110

70-110

0.3-0.34

0.8-0.9

0.27-0.34

170

170

110

110

2.9-50 reinforcement direction 0.6-1.1 perpendicular direction

Coefficient thermal expansion, 10-5/~

-0.04-0.09

3.75

-0.04-0.09

Reinforcement

Aramidfibres

Test direction

Parallel

Density, g/cm 3

1.37

Tensile strength, MPa

1450

Tensile modulus, GPa

87

HDT A (1.8 MPa), ~

<250

CUT unstressed, ~ CUT: Continuous use temperature

272

150-190

3.75

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.41 Examples of epoxide composites: general properties

Reinforcement

SMC

SMC

Woven reinforced

Glassfibre

Carbonfibre

Glass woven

Density, g/cm3

1.9

Shrinkage, %

0.1

0.1

Water absorption, 24 h, %

1.4

1.6

140-245

280-350

Elongation at break, %

0.5-2

0.5-2

Tensile modulus, GPa

14-28

70

Flexural strength, MPa

350-490

500-665

Flexural modulus, GPa

14-21

35

Compression strength, MPa

140-210

210-280

Notched impact D 256, J/m

1600-2160

800-1080

55--65

55-65

HDT A (1.8 MPa), ~

288

288

<250

CUT unstressed, oc

130-230

130-230

150-190

1.2

0.3

Tensile strength, MPa

Barcol hardness

Coefficient thermal expansion, 10-5/~

400

24

Chemical behaviour: indicated general chemicalproperties are subject to the compatibility of thefillers and reinforcements with the ambient conditions. Light

Risk of surface chalking

Weak acids

Fair resistance

Strong acids

Risk of attack with certain acids

Weak bases

Fair resistance

Strong bases

Risk of slight attack

Organic solvents

Generally resistant with exceptions such as chlorinated solvents and ketones

Food contact

Possible

CUT: Continuous use temperature

273

Thermosets and Composites

Table 4.42

Examples of foamed epoxides: general properties

Resin Reinforcement

<1 O0 ~

<1 O0 ~

<1 O0 ~

None

Glassfibre

Glassfibre

0

38

38

1.06

1.05

Reinforcement weight, % Density, g/cm 3 Flexural strength, MPa

11-13

130

136

Flexural modulus, GPa

0.4-0.5

6.8

6.6

10-12

12

Compression strength, MPa

7-8

ILSS, MPa Glass transition, ~

80-127

80-127

80-127

Fireproofed resin

<100~

<100~

<100~

none

Glassfibre

Glassfibre

0

40

40

1.4

1.45

Reinforcement Total filler weight, % Density, g/cm 3 Flexural strength, MPa

10-11

220

230

Flexural modulus, GPa

0.8-1

9.4

9.5

Compression strength, MPa

13-15 17

18

128-134

128-134

ILSS, MPa Glass transition unstressed, ~

128-134

Chemical behaviour: the division of the material induces a slight reduction in the chemical resistance and the indicated general chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. Light

Risk of surface chalking

Weak acids

Fair resistance

Strong acids

Risk of attack with certain acids

Weak bases

Fair resistance

Strong bases

Risk of attack

Organic solvents

Generally resistant with exceptions such as chlorinated solvents and ketones

Food contact

Possible

274

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.43 Examples of epoxide syntactic foams: general properties Density, g/cm 3

0.7-1

Shrinkage, %

0.3-1

Water absorption, 24 h, %

0.2-1

Tensile strength, MPa

15-30

Tensile modulus, GPa

3-5

Flexural strength, MPa

35-50

Flexural modulus, GPa

3-5

Compression strength, MPa

69-104

Notched impact D 256, J/m

8-13

Notched impact, kJ/m 2

0.5-1.5

HDT A (1.8 MPa), ~

90-120

Thermal conductivity, W/m.K

0.15-0.25

Chemical behaviour: the division of the material induces a slight reduction in the chemical resistance and the indicated general chemical properties are subject to the compatibility of the microballoons and macrospheres with the ambient conditions. Light

Risk of surface chalking

Weak acids

Fair resistance

Strong acids

Risk of attack with certain acids

Weak bases

Fair resistance

Strong bases

Risk of attack

Organic solvents

Generally resistant with exceptions such as chlorinated solvents and ketones

Food contact

Possible

4.6 Polyimides (PI) The polyimide resins are obtained in two ways: 9 BMI or aminobismaleimides or addition polyimides" reaction of a diamine and a bismaleimide to make a prepolymer that is then cured by an excess of diamine. This type is particularly convenient for the manufacture of thick parts. 9 Condensation polyimides or SP-polyimides: solvent phase reaction of an aromatic tetra-acid with a diamine. Despite the thermoplastic form they are infusible and generally insoluble. Consequently, the producer can only mould this type. It is particularly convenient for the manufacture of thin parts and films, coatings... 275

Thermosets and Composites

All the polyimides are thermostable. They do not melt before decomposition at high temperature. In thermogravimetric analysis, the decomposition starts at over 400 ~ The properties are not differentiated enough to be treated separately. However, one of the methods leads to products of higher thermal resistance, but with more limited processing. Polyimides are high-performance technical polymers mainly used for their short and long-term thermal stability. 4.6.1 General properties

Advantages Very good short and long-term heat stability allowing continuous use up to 260 ~ and peak service up to 480 ~ according to the duration and the grades; good mechanical properties, limited creep, low coefficient of friction and high abrasion resistance of the friction grades; resistance to numerous organic chemicals, stability of the electrical properties according to the temperature, resistance to high-energy radiation, limited vacuum outgassing after moisture elimination. The polyimides are typical polymers for very high performance applications. Drawbacks The high prices, often long and energy-expensive production cycles, difficulties of processing, health & safety considerations during manufacture are justified by the high performances. The light stability, arc resistance and base and acid behaviours can be limited. Special grades They can be classified according to the processing method, specific properties, targeted applications: 9 For specific processing: compression, transfer, injection moulding; prepregs, filament winding; impregnation, stratification, encapsulation, varnishing. 9 Reinforced or modified grades: glass or carbon fibres, glass beads; high, medium or low flow; for crystallization... 9 For specific applications: self-lubricating filled with graphite, graphite and fibres, PTFE etc.., for friction parts; for electronics. The semi-products are, for example: blanks, films, filaments, rods. Cost It is very difficult to give explicit prices because certain grades are marketed in finished parts or blanks for machining only. The prices range from 4E50 to ~E150 per kilogram for raw materials and much more for films, filaments, rods, blanks and parts. 276

Detailed accounts of thermoset resins for moulding and composite matrices

Processing The main processing methods are: machining, compression, transfer, injection mouldings; encapsulation, impregnation, stratification, filament winding, varnishing, sintering. For condensable polyimides, the current processing methods are applicable only by the polyimide producer that sells finished parts, blanks, rods, sheets, films... Machining is an important method to process the polyimide blanks. Applications [see Chapter 2 for further information] Consumption The consumption of polyimides by industrialized countries is not listed in the economic statistics. It is estimated that the growth in consumption slightly exceeds the rate of total plastic consumption. The applications are always high-tech. The price and the difficulty of transformation limit the use of polyimides to well-targeted applications taking advantage of the high performance of these materials. Some examples of operational or development parts are listed below. Aeronautical and space 9 Bearings, grooved couplings in self-lubricating polyimide. 9 Jet engine cones, hydraulic fluid tanks for jet engines, stiffeners of acoustical panels, spacers for engine acoustical panels, protection hoods, empennages, supports for satellite antennas. 9 Honeycombs. 9 Parts intended to function in space vacuum. 9 Soundproofing and thermal insulation of missiles, planes and helicopters; cryogenic protections on satellites, piping insulation, protections for embarked equipments in polyimide foams. Automotive 9 Self-lubricated discs for windscreen wipers, synchronization rings of heavy lorry gearboxes. 9 Base plates of cigar-lighters, bases of car lamps. 9 Heat shields, insulation shields for spark plug leads in polyimide sheet. Office automation 9 Plate bearings for printers, cable guides for printer heads; bearings and sockets for photocopiers; sliding parts and guiding rollers for high-speed printers and photocopiers... 9 Paper/print drum separation arms, drive wheels for photocopiers, drive rollers. Electricity, electronics 9 Insulating elements and spacers for electron accelerators and cathode-ray tubes. 277

Thermosets and Composites

9 9 9 9 9

9

Overmoulding of motor collectors, bodies of generator coils, overmoulding of coils, coil frames, insulation of rotor axis. Printed circuit boards usable up to 300 ~ Terminal plates and terminals, lamp bases, connectors, parts of circuit breakers. Insulating collars for chain saws, insulating elements and crossings for electric blowtorches. Drive wheels for microwave ovens, handles for electric ovens and other household appliances, parts for spit-roasters, air vents for slide projectors. Syntactic foams for microwave and RF applications.

Industrial 9 Honeycombs for structural sandwich composites. 9 Paper for fire-resistant uses. 9 Brakes on textile winding-machine, pump pads, joint seatings, manipulator inserts for glass bottle demoulding, gears of variable speed transmissions, toothed wheels. 9 Piston rings of ethylene compressors, dry bearings, sliding plates, guides for cast solid films in self-lubricated polyimide. 9 Guiding rollers of grinder bands, sealing discs of valves in an industrial Freon compressor, segments of air compressors. Racks and handling cases for printed circuit board treatments, valve seats, piston rings for hydraulic installations for the chemical industry. Cryogenic insulation in polyimide foams. Vacuum technology 9 Seals and other parts for high-vacuum installations usable up to 300 ~ without lubrication. 9 Joints and linings for vacuum pumps. Miscellaneous 9 Non-flammable scenery, coloured filter holders for studio and theatre spotlights, fire-resistant wallpaper, voice coil insulation for stereo loudspeaker in or including Nomex paper. 9 Disposable cookware in Nomex paper. 9 Microspheres for syntactic foams. 4.6.2 Thermal behaviour

Initial behaviour

The H D T A (1.8 MPa) are always high, over 250 ~ and up to 360 ~ according to the polyimide and the reinforcement. Typical glass transition temperatures are 300 ~ and more. 278

Detailed accounts of thermoset resins for moulding and composite matrices

The property retention when the temperature rises is generally excellent but depends on the matrix, the nature and level of fillers and reinforcements and the base property. As examples, for various grades: 9 57% compressive strength retention at 240 ~ 9 60-85% even 90% modulus retention at 250 ~ C. 9 50-85% tensile strength retention at 250 ~ 9 44% flexural strength retention at 250 ~ 9 55% flexural modulus retention at 250 ~ 9 54-68% flexural strength retention at 260 ~ 9 52-61% flexural modulus retention at 260 ~ Figure 4.22 shows three examples of flexural modulus retention versus temperature. These results relate to the tested grades only and cannot be generalized.

Figure 4.22. Polyimides: Examples of flexural modulus retention versus temperature

Long-term behaviour

Behaviour at high temperature depends on duration. The continuous use temperatures in an unstressed state are generally 250/260 ~ but in some cases can go down to 180 ~ Higher peak temperatures, up to 480 ~ can be tolerated. Figure 4.23 shows three examples, for three different polyimide grades, of the half-lives (50% mechanical performance retention) in hours versus the air temperatures indicated in ~ The results are correctly simulated by an Arrhenius law with a predicted 25 000 hour-service temperature of approximately 165-235 ~ For the highly heat-resistant epoxies discussed earlier, the predictions were 160200 ~ For higher temperatures, 300 ~ and more, the polyimides clearly perform better than epoxies. 279

Thermosets and Composites

Figure 4.23. Polyimides: Examples of half-life versus temperature

The gathering of these results and others leads to the model: Half-life = 4E+06*exp(-0.028*t) where half-life is in hours and t in ~ (R2 = 0.8683, where R is the regression coefficient) That is an approximately 181 ~ predicted 25 000 hour-service temperature. N A S A is developing a special polyimide (PETI-5) for the High Speed Civil Transport (Mach 2.4) whose lifespan is more than 60 000 hours at 177 ~ with excellent property retention at this temperature. Low-temperature behaviour

The behaviour is good at low temperatures also, allowing use f r o m - 6 0 ~ t o - 2 5 0 ~ according to the grades and the stresses. As films, certain polyimides remain functional at cryogenic temperatures, -269 ~ for example. These results relate to tested grades only and cannot be generalized. 4.6.3 Optical properties

Generally, thick parts are opaque and yellow to brown. Certain films are transparent with, for given grades, a 1.66 to 1.7 refractive index. 4.6.4 Mechanical properties

The mechanical properties are generally good at ambient and high temperature: tensile and flexural strength, tear and abrasion resistances. Friction

Special grades with low coefficient of friction and low wear rate are especially developed for tribological applications. They can be filled with graphite and possibly carbon or aramid fibres, PTFE, molybdenum sulphide. 280

Detailed accounts of thermoset resins for moulding and composite matrices

The PV limit can be average or high. Table 4.44 gives some examples for PV ranging from 0.09 to 4 MPa.m/s but values definitely higher, up to thousands MPa.m/s, are quoted for certain sources with very high wear. Table 4.44 Polyimides: examples of tribological properties P V (MPa.m/s)

Pressure,P (MPa)

Velocity,V (m/s)

Coefficientoffriction

0.09

Wearrate after 1000 h (mm)

0.1-0.3

0.15

0.3

0.5

0.1-0.3

0.04-0.5

0.24

0.4

0.6

0.1-0.3

Unknown

0.33

0.3

1.1

0.1-0.3

0.1-2.1

0.35

0.35

1

0.1-0.2

0.2-0.8

0.35

14

0.025

0.2-0.3

Unknown

0.875

Unknown

Unknown

0.12-0.24

Unknown

3.5

Unknown

Unknown

0.08-0.12

Unknown

4

1

4

0.07

Unknown

1252

Unknown

Unknown

0.08

80

25 000

Unknown

Unknown

Unknown

1.5-30

Figure 4.24 illustrates the evolution of the friction coefficient of a given polyimide grade versus temperature under a pressure of 14 MPa and a velocity of 2.5 cm/s, that is, a 0.35 MPa.m/s PV.

Figure 4.24. Polyimides: Examples of coefficient of friction

versus temperature

Creep The creep is low even at elevated temperatures, for example 2.8% after 1000 hours under a 17 MPa load at 300 ~ that is, a 608 MPa creep modulus. 281

Thermosets and Composites

Figure 4.25 presents, for a given grade, some examples of the evolution of the creep modulus for various conditions of load and temperature. These results only relate to tested grades and cannot be generalized.

Figure 4.25. Polyimides: Examples of creep modulus (MPa) versus time (hours)

Dimensional stability The shrinkage is generally limited, the coefficient of thermal expansion is often moderate or low, the creep is good but, on the other hand, the absorption of water or moisture can be relatively significant. Thus dimensional stability in a dry atmosphere is good, but can be degraded in water or in the presence of moisture. Figure 4.26 illustrates the differences in linear dilation of a given grade according to the hygroscopicity of the ambient atmosphere.

Figure 4.26. Polyimides: Examples of lineic dimensional variation versus time (days) 4.6.5

Ageing

Dynamic fatigue The polyimides resist high cyclic loadings. If the application is designed with a given strain amplitude it will have to be remembered that elongation at break is low. 282

Detailed accounts of thermoset resins for moulding and composite matrices

Figure 4.27 displays examples of SN curves for two grades: maximum stress for 107 cycles in traction/compression at 30 Hz frequency, versus the temperature.

Figureq.27. Polyimides:TwoexamplesojSNcurve~naximumstress(MPa)versusloadingcyclenumber

Figure 4.28 shows two examples of curves of the maximum stress for 107 cycles in traction and compression at a frequency of 30 Hz, versus the test temperature. These results relate to tested grades only and cannot be generalized.

Figureq.28. Dynamicfatigueofpolyimide:Twoexamplesofmaximumstress(MPa)versustemperature

Weathering Weathering can cause some property decreases such as strength and elongation at break. Preliminary tests are necessary for the exterior exposed parts. Figure 4.29 shows two examples of the retention of tensile strength and elongation at break for a film exposed to the WeatherOmeter. 283

Thermosets and Composites

Figure 4.29. Polyimide: Tensile strength and elongation retentions versus WeatherOmeter exposure time (h) High-energy radiation

Certain polyimides resist high-energy radiation well. For example, the properties of given grades are still suitable after exposure to 10 9 and 101~ Rad. These results are examples only and they cannot be generalized. Chemicals

The polyimides absorb water and moisture to greater or lesser degrees. This plasticizes them, involving immediate decreases in characteristics in the range of 10-25%, depending on the grades and the conditions. In long runs, the action is more significant and the type of polyimide is of prime importance. As examples, for two given grades, tensile strength retentions after immersion in boiling water are: 9 55% after 500 hours for one grade. 9 77% after 3000 hours for the other. The following swellings were noted for four different grades: . 1.5% after 7 days in boiling water. 9 0.1-2% after 300 days in ambient air at 50% RH. . 0.5% after 300 days in ambient air at 100% RH. Generally, the weak acid behaviour is good at ambient temperature, but limited at higher temperature. Resistance to strong acids and bases is poor even at ambient temperature. The behaviour with organic materials is generally good, except for alkaline products (amines, for example) and certain particular chemicals such as metacresol and hot nitrobenzene, which cause significant swelling (75-85 %, for example). Table 4.45 displays some results concerning general assessments, strength decreases and weight change percentages after immersion for one month to more than one year at ambient temperature for given grades, which are not necessarily representative of all the polyimides. 284

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.45

Polyimides: examples of chemical behaviour at room temperature

Duration, days Acetic acid

7

Conc.,%

Estimated Swelling,% Strength behaviour decrease

5

0.8

Acetic acid

Long

10

1

Acetic acid

100

20

Acetic acid

Long

>96

1

Acetaldehyde

Long

100

S

Acetic anhydride

Long

100

S

Acetone

Long

100

S

Acetonitrile

Long

100

S

Acetophenone

Long

100

S

Acetyl chloride

Long

100

S

Aluminium chloride

Long

Sol

S

Aluminium sulphate

Long

Unkn.

S

Amines

Long

Unkn.

n

1.2

5

Ammonium hydroxide

7

10

n

1

23

Ammonium hydroxide

100

10

n

1.8

32

Ammonium hydroxide

Long

Ammonium sulphate Amyl acetate

Conc

n

Long

50

S

Long

100

S

Amyl alcohol

Long

100

S

Aniline

Long

100

n

Antimony chloride

Long

10

S

ASTM1 oil

Long

100

S

ASTM2 oil

Long

100

S

ASTM3 oil

7

100

0

ASTM3 oil

Long

100

S

Barium chloride

Long

Satur.

S

Benzaldehyde

Long

100

S

Benzene

Long

100

S

Benzyl chloride

Long

100

S

Benzyl alcohol

Long

100

S

Boric acid

Long

Unkn.

S

Bromine (liquid)

Long

100

1

285

Thermosets and Composites

Table 4.45

Polyimides: examples of chemical behaviour at room temperature

Duration, days

Conc.,%

Estimated behaviour

Butanol

Long

100

n

Butyl acetate

Long

100

S

Butyl amine

Long

Unkn.

S

Butyl chloride

Long

100

S

Calcium chloride

Long

Unkn.

S

Carbon sulphide

Long

100

S

Carbon tetrachloride

Long

100

S

Cellosove

Long

100

S

Chlorine water

Long

Unkn.

1

Chlorobenzene

Long

100

S

Chloroform

Long

100

l

Chromic acid

Long

Unkn.

n

Citric acid

100

40

Citric acid

Long

10

Copper sulphate

Long

Unkn.

S

Cresol

Long

100

S

Cyclohexane

Long

100

S

Cyclohexanol

Long

100

S

Cyclohexanone

Long

100

S

Cyclohe xylamin e

100

1

Long

100

1

Diethylene glycol

Long

100

n

Dimethyl formamide

Long

100

l

Dioctyl phthalate

Long

100

S

Dioxan

Long

100

S

30

100

Ethanol

Long

96

Ethanol

Long

Unkn.

n

Ether

Long

100

S

Ethyl acetate

Long

100

S

Ethyl chloride

Long

100

S

Ethylene glycol

Long

100

n

286

1.1

4

1.1

3

S

Diethyl amine

Engine oil 200~

Swelling, % Strength decrease

30 S

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.45

Polyimides: examples of chemical behaviour at room temperature

Duration, days

Conc.,%

Fluorine

Long

100

1

Formaldehyde

Long

37

l

Formic acid

100

10

Formic acid

Long

85

Freon

7

Estimated Swelling,% Strength behaviour decrease

1.3 n

100

0.2

Freon 12

Long

100

S

Furfural

Long

100

S

Glycerol

Long

100

n

Grease

Long

Unkn.

S

Hexane

Long

100

S

Hydraulic fluid

Long

100

S

Hydrobromic acid

Long

48

n

Hydrochloric acid

100

20

l

Hydrochloric acid

Long

36

n

Hydrochloric acid

5

0.6

37

Long

40

n

Hydrogen peroxide

Long

30

n

Isooctane (fuel a)

Long

100

S

Isopropanol

Long

100

n

Kerosene

Long

100

S

Methanol

Long

100

n

Methyl ethyl ketone

Long

100

S

Mineral oil

Long

100

S 1

7

10

Nitric acid

100

20

Nitric acid

5

70

20-26 1.1

n

Oxalic acid

Long

Unkn.

1

Perchloroethylene

Long

100

1

Petrol

Long

100

S

Phenol

Long

Unkn.

1

Phosphoric acid

Long

85

1

30

Hydrofluoric acid

Nitric acid

6

4 60

n

287

Thermosets and Composites

Table 4.45

Polyimides: examples of chemical behaviour at room temperature

Duration, days

Conc.,%

Potassium carbonate

100

30

0.8

3

Potassium hydroxide

100

10

1.6

3

Potassium hydroxide

Long

45

n

Potassium permanganate

Long

20

n

Potassium sulphate

Long

Unkn.

S

Propanol

Long

100

n

Pyridine

Long

Unkn.

n

Sea water

Long

100

S

Silicone oil

Long

Unkn.

S

Silver nitrate

Long

Unkn.

S

Sodium borate

Long

Unkn.

S

Sodium chloride

Long

25

S

Sodium cyanide

Long

Unkn.

S

Sodium hydroxide

7

Estimated behaviour

10

20-30

Sodium hydroxide

Long

10

n

Sodium hydroxide

Long

55

n

Styrene

Long

100

S

Sulphuric acid

90

1

Sulphuric acid

7

10

Sulphuric acid

100

Sulphuric acid

Long

Textile detergent

7

2-4

18

n

1

12-31

20

n

0.9

70

n

0.2-2

Long

100

S

Trichloroethylene

Long

100

S

Water

Long

100

S

White spirit

Long

100

S

Xylene

Long

100

S

100

10

1.1

S: satisfactory; 1: limited; n: not satisfactory Long: the duration is undefined but is of the order of years Conc: concentrated solution; Satur: saturated solution; Sol: Solution; Unkn.: Unknown 288

3

1

Toluene

Zinc chloride

Swelling, % Strength decrease

4

Detailed accounts of thermoset resins for moulding and composite matrices

Vacuum outgassing

After elimination of moisture, the vacuum outgassing of certain polyimides is sufficiently low to be usable in space. Fire resistance

The oxygen indices are in the range of 30 to 53. Specific formulations make it possible to obtain V0 UL 94 fire rating. 4.6.6 Electrical properties

The insulating properties basically depend on the filler: graphite filled grades can have resistivity values as low as 100 ohm/cm. For the insulating grades, electrical properties except arc resistance are good and remain relatively stable with changing temperature. As an example, for a given grade, between 50 Hz and 106 Hz, and between 25 ~ and 200 ~ the following variations are quoted: 9 4.7 to 5 for the permittivity 9 0.003 to 0.018 for the loss tangent. On the other hand, the resistivity is definitely influenced more and, for another grade, decreases from 1016 to 10 a2 when the temperature increases from ambient to 260 ~ whereas in another example, the resistivity changes from 1017 at 38 ~ to 1011 at 315 ~ 4.6.7

Joining

Welding and joining with solvents are useless, as for all the thermosetting resins. Adhesives alone, chosen following rigorous tests, allow joining. The parts should not be subjected to high stresses. After cleaning by abrasion and with solvents, the polyimides can be stuck with a polyimide, epoxy or acrylic resin adhesive whose thermal resistance is compatible with the operating conditions. 4.6.8 Foamed polyimides and syntactic foams Polyimide resins are: 9 Foamed to obtain very lightweight foams. 9 More rarely filled with artificial balloons or spheres to make syntactic foams. Flexible foams

Contrary to typical industrial dense polymers, which are processed as carefully as possible to avoid the formation of bubbles, vacuoles and other inclusions, the alveolar materials result from intentionally introducing, in a controlled way, a certain proportion of voids with the aims" 9 To increase flexibility. 289

Thermosets and Composites

9 To improve the thermal or phonic insulating character. 9 To make damping parts. The alveolar materials consist of a polymer skeleton surrounding the cells, which may be closed or partially or completely open to neighbouring cells or to the outside. The intrinsic properties come from those of the polyimides with: 9 A reduction in the mechanical properties due to the small quantity of solid material and the high proportion of gas. 9 A reduction in the chemical behaviour due to the strong division of the material. The thin cell walls immediately absorb liquids and gases and are rapidly damaged. The polyimide foams are flexible and have a very low density (7 kg/m3), associated with good fire behaviour, a broad service temperature range and good soundproofing and thermal insulation qualities. These materials are sensitive to diluted strong bases, concentrated salts and acids. Other foams have densities varying from 15 to 250 kg/m 3. These foams find applications in:

Aeronautics, space, armaments, shipbuilding 9 Soundproofing and thermal insulation of missiles, planes and helicopters. 9 Protection of material embarked on space shuttles. 9 Cryogenic protection on satellites. 9 Piping insulation. Industrial 9 Cryogenic applications. Syntactic foams

Syntactic foams are composites made up of micro-balloons or hollow macrospheres bound into a plastic matrix. The polyimide syntactic foams are used in specific electronic equipment for microwave and RF applications. They act as structural, dielectric and heat barrier materials. Micro-balloons can be made of polyimides for special applications. 4.6.9 Trade name examples

Actymid, Aurum, Compimide, Cuming C-Stock, Duratron, Imidex, Kapton, Kerimid, Kinel, Meldin, Neopreg, Nolimid, Nomex, Sintimid, Upilex, Upimol, Vespel, Willmid. 4.6.10 Property tables

Tables 4.46 to 4.51 relate to examples only and cannot be generalized. 290

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.46 Thermoset polyimides for moulding: property examples Neat

Glassfibre reinforced

40% glass fibres

65% glass fibres

1.4-1.5

1.5-1.9

1.6

1.9

0.1-1

0.1-0.6

Water absorption, 24 h, %

0.4-1.3

0.4--0.9

0.6

0.5

Rockwell hardness, M

110-120

115-126

Tensile strength, MPa

30-160

40-160

45-50

120-160

1

0.5-1

Tensile modulus, GPa

3-10

7-32

Flexural strength, MPa

45-250

90-350

Flexural modulus, GPa

3-10

7-21

5-8

17-21

180-240

100-180

130-230

0.4

0.4

Density, g/cm 3 Shrinkage, %

Elongation at break, %

Compression modulus, GPa

3

Compression strength, MPa

133-230

Poisson's ratio Notched impact D 256, J/m H D T A (1.8 MPa), ~ CUT unstressed, ~

35-800

55-800

>300

>300

320

330

180-250

180-250

200-250

200-250

Glass transition, ~ Thermal conductivity, W/m.K Coefficient thermal expansion, 10-5/~

250-350

300 0.2-0.5

0.3-0.5

0.3

0.5

1.5-5

1-5

1.5-3

1.4

Minimum service temperature, ~

-250 - -60

Volume resistivity, ohm.cm

1014-1016

Dielectric constant

-100 - -60 1015-1016

1014-1015

3-5

3--4

4-5

Dissipation factor, 10-4

10--400

150

90

Dielectric strength, kV/mm

10-22

Graphite + aramid fibres

MoS2 + PTFE

Graphite + MoS 2

Friction

Friction

Friction

Arc resistance, s

Limited

Oxygen index, %

36--44

Filler

Graphite

Specific applications Density, g/cm 3

1.4-1.6

1.65

1.4

1.4-1.5

Shrinkage, %

0.3-0.6

0.1-0.2

1

0.2-0.6

Water absorption, 24 h, %

0.1-0.6

0.6

0.3-1.3

0.3-1.2

Rockwell hardness, M

100-110

94

113-115

95-110

291

Thermosets and Composites

Table 4.46 Thermoset polyimides for moulding: property examples Filler

Graphite

Graphite + aramid fibres

MoS 2 + PTFE

Graphite + MoS 2

30-65

30

10-35

30-40

Elongation at break, %

1-6

0.3-0.4

0.5-1

<1

Tensile modulus, GPa

3-8

8

2.4

Flexural strength, MPa

80-90

60

40-50

55-90

Flexural modulus, GPa

6-8

7-8

2-3

4-5

Compression strength, MPa

110-140

80-90

80-140

110-155

Notched impact D 256, J/m

14-45

35

14-16

14-17

H D T A (1.8 MPa), ~

310-360

>300

>300

360

CUT unstressed, ~

180-260

200-260

180-250

180-250

Glass transition, ~

300

300

300

300

1.4-5

0.4-0.5

0.2-0.3

0.7-0.9

1-4

2.4-3.3

5-7

2.5

Tensile strength, MPa

Thermal conductivity, W/m.K Coefficient thermal expansion, 10-5/~ Minimum service temperature, ~ Volume resistivity, ohm.cm

- 2 5 0 - -60

102-103

103-104

1012-1014

Dielectric constant

14

3-4

Dissipation factor, 10-4

50

110-160

Dielectric strength, kV/mm

10

18-19

Oxygen index, %

36-50

30

General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. I f the fillers are adapted, the chemical properties are the same as the polyimide matrix. Light

Limited behaviour, preliminary tests necessary

Weak acids

Limited behaviour with hot acids

Strong acids

Limited to temperature

Bases

Attacked to a greater or lesser degree according to the nature, concentration and temperature

Solvents

Good general behaviour. Resistance to ethers, aromatics, esters. Attacked by certain alcohols, hot metacresol and nitrobenzene

Water

Generally, water absorption plasticizes polyimides. Possibly attacked by boiling water

Industrial fluids

Good resistance to the hydraulic fluids, kerosene, oils for gear boxes, Freon, silicone oils

CUT: continuous use t e m p e r a t u r e in an unstressed state 292

poor

behaviour

even

at

ambient

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.47 Condensation polyimides for moulding: property examples Density, g/cm 3

Neat

Neat TP

30% glassfibre

30% carbon fibre

1.33-1.43

1.33

1.56

1.43

Shrinkage, %

0.8-0.9

0.4-0.5

0.2

Water absorption, 24 h, %

0.2-0.4

0.2-0.3

0.2-0.33

Rockwell hardness, M

92-102

104

105

168

233

Rockwell hardness, E Tensile strength, MPa

47 70-140

92 90

Elongation at break, %

8-9

Tensile modulus, GPa

2-3

Flexural strength, MPa

96-200

135

246

326

Flexural modulus, GPa

3-3.5

2.9

9-10

19-20

Compression modulus, GPa

2-4

3.2

Compression strength, MPa

110-280

190-195

210

120

108

Poisson's ratio Notched impact D 256, J/m Notched impact, kJ/m 2

3

2

12

21

0.4 80-90 17

H D T A (1.8 MPa), ~

235-300

242

247

CUT unstressed, ~

180-250

180-250

180-250

Glass transition, ~

315

Thermal conductivity, W/m.K

0.1-0.4

Coefficient thermal expansion, 10-5/~

4.5-5.6

Volume resistivity, ohm.cm Dielectric constant

5

3-4 18-36

Dielectric strength, kV/mm

20-22

Oxygen index, %

44-53

15% graphite + 10% PTFE

15% MoS 2

Friction

Friction

1.4-1.6

1.6

3.3

15% graphite

40% graphite

1.4-1.5

1.6-1.7

Specific applications

Water absorption, 24h, %

0.49 0.6-4.7

1014-10 ~6

Dissipation factor, 10-4

Density, g/cm 3

0.37 1.7-5.3

0.2

0.14

0.2

0.23

Rockwell hardness, M

82-94

68-78

69-79

75-100

Tensile strength, MPa

62-66

48-54

44-52

55-56

Elongation at break, %

4-6

2-3

3-6

4

Flexural strength, MPa

90-110

70-130

70

Flexural modulus, GPa

3-4

4-5

3

Compression modulus, GPa

2-3

3-4

1-2

Compression strength, MPa

100-140

90-110

77-105 293

Thermosets and Composites

Table 4.47 Condensation polyimides for moulding: property examples 15% graphite

40% graphiie

15% graphite + 10% PTFE

15% MoS 2

43

38

Friction

Friction

CUT unstressed, ~

180-260

200-250

200-250

180-260

Thermal conductivity, W/m.K

0.4--0.9

0.9-2.1

0.4-0.8

2.3-4

3.8

2.3-3

Specific applications Notched impact D 256, J/m H D T A (1.8 MPa), ~

Coefficient thermal expansion, 10-5/~ Volume resistivity, ohm.cm

360

1012-1013

Dielectric constant

13-14

Dissipation factor, 10-4

53-106

Density, g/cm 3

Thermoplastic PI Neat

Thermoplastic PI Friction

1.33

1.51

Rockwell hardness, M Rockwell hardness, E

37 47

Tensile strength, MPa

92

107

Elongation at break, %

90

3

Flexural strength, MPa

135

96

Flexural modulus, GPa

2.9

6

Notched impact, kJ/m 2

80

H D T A (1.8 MPa), ~

262

Coefficient thermal expansion, 10-5/~ Dielectric constant

5

2.5-6.2

3.3

6.6

PV limit, MPa.m/s

17 (lubricated)

Coefficient of friction

0.09

General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. I f the fillers are well adapted, the chemical properties are the same as the polyimide matrix Light

Limited behaviour, preliminary tests necessary

Weak acids

Limited behaviour with hot ones

Strong acids

Limited to poor behaviour even at ambient temperature

Bases

Attacked to a greater or lesser degree according to the nature, concentration and temperature

Solvents

Good general behaviour. Resistance to ethers, aromatics, esters. Attacked by certain alcohols, hot metacresol and nitrobenzene

Water

Generally, absorbed water plasticizes polyimides. Possibly attacked by boiling water

Industrial fluids

Good resistance to hydraulic fluids, kerosene, oils for gear boxes, Freon, silicone oils

CUT: continuous use t e m p e r a t u r e in an unstressed state 294

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.48 Undefined polyimides for moulding: property examples Neat

Density, g/cm 3

1.3-1.4

Shrinkage, %

40% glassfibres Aramid fibres and beads + MoS 2 + PTFE

Friction

1.6

1.4

1.4-1.7

0.3-0.6

0.8-1

0.1-0.6

Water absorption, 24 h, %

0.2-0.3

0.2

Rockwell hardness, M

92-120

Tensile strength, MPa

72-86

80

30

20-55

Elongation at break, %

7-8

1

1

0.3-4

Tensile modulus, GPa

3-4

2-11

Flexural strength, MPa

110

45

Flexural modulus, GPa

8

3

55

35

80

Notched impact D 256, J/m Ratio tensile modulus or strength 250 ~ H D T A (1.8 MPa), ~

~

%

50

14-40 50-85

360

>300

>300

>300

CUT unstressed, ~

180-260

225

<225

180-260

Glass transition, ~

300-365

300

290

300-365

Thermal conductivity, W/m.K

0.15-0.4

0.3

0.25

0.2-0.8

4-6

3

3.8-5

2-7

Coefficient thermal expansion, 10-s/~ Minimum service temperature, ~ Volume resistivity, ohm.cm Dielectric constant

-250 - -60

-250 - -60

1014-1016

1015

3-5

4.1

Dissipation factor, 10-4

10-400

Dielectric strength, kV/mm

10--22

Arc resistance, s

Limited

Oxygen index, %

36-53

103-1014 3.3

3-14 50-200

14

19

10--19

<45

<45

30-40

295

Thermosets and Composites

Table 4.49

Polyimides for laminates: property examples Neat polyimide

Density, g/cm 3 Tensile strength at 23 ~

1.2-1.3 MPa

80-100

Tensile strength at 180 ~

MPa

50-70

Tensile strength at 200 ~

MPa

40-60

Tensile modulus at 23 ~

GPa

3.5-4.5

Tensile modulus at 180 ~

GPa

2.5-3

Tensile modulus at 200 ~

GPa

2-3

%

2-3

Elongation at break at 23 ~ Elongation at break at 180 ~

%

2-3

Elongation at break at 200 ~

%

2-5

Laminates

Carbonfibre UD Tested in fibre direction

Density, g/cm 3

Glassfibre 1.9-2

Water absorption, 24 h, %

0.3

Barcol hardness, M

70

Tensile strength at 23 ~ Tensile strength at 240 ~

MPa

1210-1450

MPa

Tensile modulus at 23 ~

GPa

Flexural strength at 23 ~

MPa

Flexural strength at 240 ~ Flexural modulus at 23 ~

1000-1300 115-120 1850"

MPa

Compression strength at 240 ~ Compression modulus at 23 ~ Compression modulus at 240 ~

MPa MPa GPa GPa

117"

14-28

1400

70-140

800 128 120

ILSS, MPa

14-15

Notched impact D 256, J/m CUT unstressed, ~

700 180-250

Coefficient thermal expansion, 10-5/~ * A t 90~ flexural strength is 53 M P a at 23 ~ and 29 M P a at 240 ~ 23 ~ and 5 G P a at 240 ~ 296

70-140

1240"

GPa

Compression strength at 23 ~

50-350

1 flexural modulus is 7 G P a at

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.50 Polyimide foams: property examples Density, kg/m 3 Service temperatures, ~ Thermal conductivity, W/m.K

7

15-250

-195 - +260

-195 - +300

0.042

Compression load to 40 %, MPa

0.005-0.009

0.015-0.050

Tensile strength, MPa

0.050

0.050-0.250

Tensile strength after 1000 h at 260 ~

0.025

Oxygen index, %

43

Table 4.51 Polyimide films: property examples Density, g/cm 3

1.33-1.42

Tensile strength, MPa

100-230

Tensile strength at yield, MPa

70

Elongation at break, %

70-110

Tensile modulus, GPa

2-3

UL94 fire rating

V0

Opticalproperties

Haze, %

0.1

Light transmission, %

64

Refractive index

1.7

4.7 Silicones or polysiloxanes (MQ, PMQ, PVMQ, VMQ or SI) and fluorosilicones (FMQ, FVMQ or FSI) Silicones are obtained by hydrolysis of chlorosilanes. According to their functionalities, they lead to: 9 Oils and greases, reactive or unreactive, which are not taken into account in this book. 9 Elastomers, liquid or solid, for processing with standard elastomer methods including vulcanization. The moduli are very low and the vulcanizates are elastic. 9 Resins for processing by thermosetting injection and coating. The higher rigidities are of the order of some other plastics. For an elastomer, the general formula is of the type: R

I (~ Si~

O ~)n

I R 297

Thermosets and Composites

The replacement of carbon by silicon in the backbone leads to essential characteristics such as thermal resistance, but the pendent groups also influence the final properties. These groups can be: 9 Methyl: high heat resistance, high compression set, limited lowtemperature flexibility. 9 Vinyl: ease of curing, lower heat resistance and mechanical properties. 9 Phenyl: the highest heat resistance with good low-temperature flexibility. The silicones can be modified epoxy or acrylate. Industrial silicones are diverse: 9 Castable, ambient temperature curable, one component: one-part RTV (room temperature vulcanizing) 9 Castable, ambient temperature curable, two-component" RTV bicomponent 9 Liquid silicone rubber (LSR), hot curing: LSR processed by LIM (liquid injection moulding) 9 Millable, hot curing: silicones HTV or HV (high temperature vulcanization) or HVR (high viscosity rubber) 9 Resins for hot and high-pressure injection or for coating. The fluorosilicones are characterized by their good behaviour with hydrocarbons and other automotive fluids. The majority of silicones and fluorosilicones are thermostable polymers of specialized or highly specific applications. 4.7.1 General properties Advantages

Very good stability of the properties across a broad range of temperatures, long-term heat stability, low-temperature flexibility, good electrical properties, ease of some manual or semi-automatic processes, good light and weathering behaviour, resistance to numerous chemicals especially for the fluorosilicones, water repellence, possibility of transparency, physiological inertness of suitable grades. Drawbacks

Rather high prices justified by performance, limited mechanical properties, low rigidity of the majority of grades, limited resistance to bases and strong acids, poor behaviour with numerous solvents for the silicones, risks of reversion in confined atmosphere or for very thick parts, high permeability to gases, attacked by high-pressure water vapour, low thickness of the parts obtained with the moisture curable mono-component grades, high coefficient of expansion for the neat grades, corrosivity of the acid curable grades, industrialization and reproducibility difficulties with certain processes. 298

Detailed accounts of thermoset resins for moulding and composite matrices

Special grades They can be classified according to the type of processing, specific properties, targeted applications: 9 For specific processing: one-part, two-part, RTV, LSR, injection resins, millable or HVR, syntactic or expanded foams, heat curing, fast curing, thixotropic. 9 For specific properties: neutral or anti-corrosive, fireproofed, transparent, good adhesion without primer; resistant to reversion, moisture, chemicals, harsh environment; high and low temperatures, high thermal dissipation, non-curable for special cements. 9 For specific applications: thick parts, electrical and electronic, ablative materials. Cost The price is of the order of ~12-100 per kilogram. Processing The resin and elastomer compounds based on resin, liquid and millable elastomers are extruded, calendared or, more often, moulded by traditional compression, transfer or injection processes. The other forms of presentation are processed by more particular methods. For the bicomponent materials it is necessary to correctly mix the two parts to the indicated precise proportions. This operation, in certain cases, can be performed manually. Both liquid and pasty monocomponent and compounded bicomponent silicones can be processed by LIM, casting, low-pressure extrusion- often starting from a simple cartridge but also with more or less automated and robotized guns. Special equipment makes it possible to simultaneously realize dosage, mixing and injection or extrusion. Certain cements are applicable with a spatula. Monocomponent silicones exposed to ambient air have a limited pot-life as do the bicomponent materials after mixing. Moisture curable grades make it possible to produce only limited thicknesses, as moisture cannot penetrate beyond a certain depth. As an example, the reticulation of a 3 mm thickness part requires 24 hours for a given grade. Some grades do not cure and thus remain plastic. Applications [see Chapter 2 for further information]

Consumption The silicone consumption of industrialized countries is not listed in the economicstatisticsandthefiguresdifferalotaccordingtothesources.Thetotal consumption is estimated in the order of 1-2 % of the total for plastics and its progression exceeds the rate ofthe total plastics consumption. A great number of applications, as much as 85 %, are outside the framework of this book. 299

Thermosets and Composites

The consumption is divided between several markets: building and civil engineering, electricity and electronics, mechanics, chemical industry and automotive are the main ones, but also medical, aeronautics, computers... The applications are always specific. The price and the special properties limit the use of silicones to well-targeted applications taking advantage of their unique performances. Some examples of operational or development parts are listed below.

Building and civil engineering 9 9 9 9 9

Sealing cements. Safety cable sheathing for buildings or power stations. Seals, joints for glazing. Architectural coated fabrics for roofs. Carpet backing in low-flammability foamed silicone for institutional building.

Electricity, electronics, optoelectronics 9

9

9 9 9 9 9 9

Medium and high-voltage insulation; joints and cables for external projectors, street lighting; cables for drying ovens, convectors, neon signs; solar panel seals. Translucent coatings for electricity and electronics, potting of electronic components; heat dissipation coatings, encapsulation of semiconductors and other components for electronics. Flexible moulds for electrical and electronic components. Filling of units, charts, circuits, components.., for electronics, computers, electricity, aeronautics, space, appliances, automobiles. Casting syntactic foams for electronics. Optical fibre sheaths. Keypads. Binders for "mica paper".

Electric household appliances 9 9 9 9 9

Cast seals for ceramic hobs, ovens; sealing adhesives for domestic iron connections, seals for dishwashers. Cables for tumble dryers, convectors. Anode caps for television sets. Bellows for drink dispensers. Tubes for coffee machines.

Mechanical industry 9 Seals cast in situ, high-temperature seals, tight and flexible joints. 9 9

3O0

Cables for chemical plants, wire coatings for control circuits. Cast moulding parts in small series and prototypes, shock and vibration absorbers.

Detailed accounts of thermoset resins for moulding and composite matrices

9 9 9 9 9 9 9 9

Roller covering for handling of hot products such as coating machines, soft covering for wheels of packing machines. Hot air sheaths. Bellows, diaphragms. Flexible keyboards for machine control panels. Binders of refractory fillers for the manufacture of ablative materials. Foamed seals for handling vacuum pads. Silicone foam coated adhesive tapes. Protection in silicone foam coated glass fibre or aluminium sheets.

Tools for moulding, casting 9

Moulds for plaster, stucco, reconstituted stone, cement and concrete mouldings; moulds for decorative elements such as statuettes, furniture parts, costume jewellery in low melting point alloys; foundry waxes. 9 Moulds for automotive instrument panels, shoes, imitation leathers in plastisols and polyurethanes; moulds for ultra-high frequency moulding of PVC; moulds for epoxies and unsaturated polyesters laminates. Tools for prototypes and vacuum casting. Matrices or plungers for thermoforming of ABS, polystyrene, PVC. Cores for composite moulding by isostatic compression. Heat-insulating laminates for mould insulation.

Medical, health, food appliances 9

9 9 9 9 9 9 9

Dummies, nipples, pharmaceutical stoppers; oxygen masks; nozzles, masks, tubes for respiratory systems; caps and pistons for syringes; dialyser seals, X-ray opaque shunts. Catheters, tubes for transfusion; anaesthesia tubing, oxygen sheaths. Balls for valves, valves for cephalic liquid; food dispensing valves, body electrodes. Artificial ventricles, elements for pacemakers, plastic surgery. Contact lenses. Prostheses. Moulds including f o a m f o r food. Room temperature foaming silicone for prosthetics.

Aeronautics 9 High temperature seals, connectors, shock and vibration absorbers. 9 External seals for windows, inspection hatches, doors. 9 Safety cables for planes. 9 Ablative materials. 9 Laminates for interior fixtures. 9 Seating and cushioning in low-flammability foamed silicone. 301

Thermosets and Composites

Automotive and transport 9 Cables for lighting, heating, de-icing; ignition cables, spark plug boots; safety cables for trains, subways. 9 Seals for engines, radiator seals, cylinder head gaskets, caps for automobile ignition systems. 9 Heavy lorry coolant hoses. 9 Expansion elements for oil leakage detectors. 9 Silicone coated fabrics for airbags. 9 Seals for train windows. 9 Jaguar XJ6 soundproofing with a foam-in-place silicone. 9 Seating and cushioning in low-flammability foamed silicone for commuter trains and other mass transport. Office automation 9 Roller soft coverings for photocopiers, faxes, thermal printers. 9 Wires for computers. 9 Flexible keyboards for telephones, computers. 4.7.2 Thermal behaviour

Initial behaviour

The majority of the silicones are flexible elastomers and the HDTs are not adapted. The variation of properties is generally relatively weak in the service temperature range. Figure 4.30 displays, for a given grade, examples of the retention of tensile strength and elongation at break in percentage versus the testing temperature.

Figure4.30. Silicone'Exampleso~ensil~trengtkandelongatiorntbreakretentionsversustemperature 302

Detailed accounts of thermoset resins for moulding and composite matrices

The property retention at temperature t is calculated as follows: Property at temperature t Property at 20 ~ Long-term behaviour Almost all silicones and fluorosilicones are thermostable polymers. However, some grades, notably R T V ones, while being heat-resistant, cannot be classified in this category. The continuous use temperatures in an unstressed state are roughly 150260 ~ Higher temperatures up to 350 ~ can be tolerated during shorter times. The UL temperature indices, for the tested materials, range from 105 ~ to 240 ~ For electric cables, continuous use temperatures of 250 ~ up to 300 ~ are claimed. For R T V silicones, examples of continuous use temperatures in an unstressed state (CUT) and peak temperatures are respectively: 9 One-part RTV/CAF: 110/220 ~ (CUT) and <260 ~ (peak) . Two-part RTV: 180/260 ~ (CUT) and <260/315 ~ (peak). As an example, for a millable elastomer, lower continuous use temperatures are calculated from the graph in Figure 4.31.

Figure 4.31. Silicone: Examples of half-life versus temperature

The following Arrhenius law correctly simulates the results: Half-life = 3E+06*exp(-0.0272*t) with half-life in hours and t in ~ (R2= 0.9308), giving an approximately 176 ~ predicted 25 000 hour-service temperature. Let us remember that for highly heat-resistant epoxies the predictions were 170-200 ~ and for polyimides 165-235 ~ 303

Thermosets and Composites

In other examples concerning cable sheathing, the property retentions after 10 days at 200 ~ are very variable according to the grade and the considered property: 9 Tensile strength retention: 57-78% 9 Elongation at break retention: 22-70% 9 Tear resistance retention: 40-100% The most sensitive property is the elongation at break, which is very important if the cable moves during use. These results relate to tested grades only and cannot be generalized. Lastly, some problems can be encountered with high-pressure vapour and with reversion in a confined atmospheres or in the mass of thick parts. Low-temperature behaviour

The flexibility is good at low temperatures allowing use to -50 ~ to -115 ~ according to the grades and stresses. As examples" 9 H T V for cables coating:-60 9 One-part RTV, low hardness:-110 to-50 9 One-part RTV, high hardness:-70 to-50 9 Two-part RTV, low hardness:-115 to-50 9 Two-part RTV, high hardness:-100 to-50 These results relate to the tested grades only and cannot be generalized. 4.7.3 Optical properties

Transparent grades are available with, for given grades, a 1.41 to 1.49 refractive index. 4.7.4 Mechanical properties

Silicone elastomers are not intended for the manufacture of structural parts because of their mechanical characteristics, but they are used for their flexibility, their elasticity or their damping behaviour. The tensile strength is particularly low for the RTV. The resistances to abrasion and tearing are limited. The silicone resins have higher mechanical performances. Non-curable grades remain plastic with high creep. Friction

Silicones are not used for friction parts, but they often have good antiadherence properties. Creep, compression set

Certain grades have a propensity to creep, especially the non-curable grades. In any event, the low or very low moduli of most grades make it necessary to be vigilant during the calculation of the supported stresses. 304

Detailed accounts of thermoset resins for moulding and composite matrices

The compression sets of the elastomers vary strongly according to the grades and the conditions of post-curing, as shown in the following examples of compression sets after 22 hours at 175 ~ 9 Low hardness LSR: 15 % after post-curing, 65 % before post-curing . Low hardness millable silicone rubber: 15% after post-curing, 40% before post-curing. The graphs in Figure 4.32 plot the compression sets of the same silicone: 9 postcured and non-postcured, versus the compression time at 150 ~ 9 postcured and non-postcured, versus the compression time at 175 ~ These results only relate to tested grades and cannot be generalized.

Figure 4.32. Silicone: Examples of compression sets versus time

Dimensional stability

Shrinkage is difficult to control with certain processes, which makes massproduction delicate. The coefficients of thermal expansion are high, but the moisture and water absorptions are very low. 4.7.s Ageing Dynamic fatigue

The dynamic fatigue resistance is good for certain grades if the loading is adapted to the weak modulus. As an example, a judiciously selected film can be subjected to repeated foldings after a 1500 hours ageing at 180 ~ 305

Thermosets and Composites

Weathering Silicones are resistant to light and weathering. They are the materials of choice for long-lasting external applications. Corrosivity

Acid reticulation grades can cause corrosion of metals by contact. Neutral or non-corrosive grades avoid this drawback. Chemicals

Resistance to moisture and hot water is generally good. However, highpressure water vapour can cause their deterioration. The behaviour with weak acids and bases is good. Strong bases and acids attack silicones and fluorosilicones. With organic solvents, the resistance of the fluorosilicones is definitely better than that of silicones, which generally show poor resistance. The fluorosilicones have good resistance to mineral oils, oil products, aliphatic solvents, and are not so good with aromatic solvents. On the other hand, they have poor resistance to chlorinated solvents and ketones. It should be noted that in the event of redrying, silicones often recover a large part of their initial properties. Table 4.52 presents generally the nature of the silicone polymers and the general indications concerning the chemical behaviour. However, it will be necessary to carry out tests before choosing a material for a given use. Table 4.52

Silicones and fluorosilicones: examples of chemical behaviour

Concentration, %

Temperature,~

Estimated behaviour Silicone

Accumulator acid

Fluorosilicone

Unknown

20

n

Acetic acid

50%

50

1

Acetic acid

>96%

70

1

1

Acetaldehyde

100%

20

S

n

Acetone

100%

20

1

n

Ammonia gas

100%

60

1

n

A m m o n i u m hydroxide

100%

20

n

A m m o n i u m hydroxide

Conc

20

S

Aniline

100%

100

S

S

A S T M 1 oil

100%

100

S

S

A S T M 2 oil

100%

100

S

S

A S T M 3 oil

100%

100

1

S

Sat

100

S

B enzaldehyde

100%

100

S

1

Benzene

100%

20

n

1

Barium hydroxide

306

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.S2

Silicones and fluorosilicones: examples of chemical behaviour

Concentration, %

Temperature,~

Estimated behaviour Silicone

Fluorosilicone

Butane

100%

20

n

S

Butanol

100%

50

1

S

Butyl acetate

100%

20

n

n

Butyraldehyde

100%

20

1

n

C a r b o n disulphide

100%

20

n

S

C a r b o n tetrachloride

100%

20

n

1

Chloroform

100%

20

1

1

40%

50

n

1

Chromic acid Cyclohexane

100%

20

n

1

Dibutyl phthalate

100%

20

1

1

Dibutyl sebacate

100%

20

1

1

Dichloroethane

100%

20

n

1

Dichloroethane

100%

50

n

n

Diethyl ether

100%

20

n

n

Diethyl ether

100%

20

n

n

Diethylene glycol

100%

20

1

S

Dioctyl phthalate

100%

100

1

S

Dioctyl sebacate

100%

20

96%

50

S

1

Ethanol

1

Ethyl acetate

100%

20

n

n

Ethyl chloride

100%

20

n

S

Ethylene

100%

20

E t h y l e n e chloride

100%

20

1

1

E t h y l e n e glycol

Unkn.

93

S

S

Fluid 101

Unkn.

100

1

S

Formaldehyde

37%

20

S

F o r m i c acid

Sol

20

1

1

F o r m i c acid

Sol

70

n

n

Freon

100%

20

S to n

Fuel

100%

20

n

Fuel + 15% alcohol

S

20

1 1

Fuel A S T M B or C

100%

20

n

Heptane

100%

20

n

Hexane

100%

20

n

1

1

307

Thermosets and Composites

Table 4.52

Silicones and fluorosilicones: examples of chemical behaviour

Concentration, %

Temperature,~

Estimated behaviour Silicone

Hydrochloric acid

20%

Hydrofluoric acid Hydrogen peroxide Isooctane

Fluorosilicone

50

n

40%

20

n

90%

20

S

1

100%

20

n

1

Isopropanol

100%

20

S

1

Isopropanol

100%

50

l

1

Kerosene

100%

50

n

S

Liquid oxygen

100%

Methane

100%

20

n

Methanol

100%

20

S

S

Methyl ethyl ketone

100%

20

n

n

Methylene chloride

100%

20

n

1

Naphta

100%

50

n

1

Natural gas

Unkn.

20

1

1

Unkn.

l 1

Nitric acid

10%

50

n

Nitric acid

65 %

20

n

100%

20

n

60%

50

S

Propane

100%

20

1

1

Silicone oil

100%

20

1

S

Skydrol 500

100%

70

1

1

Perchloroethylene Phosphoric acid

Sodium hydroxide

n

10%

90

n

Strong oxidizing acids

Conc

Hot

n

n

Sulphur dioxide (dry)

100%

20

1

1

20%

20

n

Tetrachloroethane

Sulphuric acid

100%

20

n

n

Tetrachloroethylene

100%

20

n

1

Toluene

100%

20

n

1

Transformer oil

100%

20

1

S

Trichloroethane

100%

20

n

1

Trichloroethylene

100 %

20

n

1

Unknown

20

S

S

Weak acids

S: satisfactory; 1: limited; n: not satisfactory Long: the d u r a t i o n is u n d e f i n e d but is of the o r d e r of years. Conc: c o n c e n t r a t e d solution; Satur: s a t u r a t e d solution; Sol: solution; Unkn.: U n k n o w n

308

Detailed accounts of thermoset resins for moulding and composite matrices

Fire resistance

Certain resin and elastomer silicone compounds are classified U L 94 V0. The oxygen index is generally in a range of 23 to 35. Generally, they have an inherent low toxicity and low smoke emission level. The fluorosilicones naturally behave better than silicones but contain fluorine. Silicones are used for the manufacture of ablative materials. 4.7.6 Electrical properties

The insulating properties are very good and explain the numerous electrical and electronic applications. 4.7.7Joining

Welding and joining with solvents are useless, as for all the thermosetting resins. Adhesives alone, chosen after rigorous tests, allow joining, after cleaning by abrasion and with solvent. The joined parts should not be subjected to high stresses. 4.7.8 Foamed silicones and syntactic foams

Silicone resins are: 9 Foamed to obtain lightweight foams. 9 More rarely filled with artificial balloons or spheres to make syntactic foams. Flexible foams

Contrary to typical industrial dense polymers, which are processed as carefully as possible to avoid the formation of bubbles, vacuoles, etc., the alveolar materials result from intentionally introducing, in a controlled way, a certain proportion of voids with the aims: 9 To increase flexibility. 9 To improve the thermal or phonic insulating character. 9 To make damping parts. The alveolar materials consist of a polymer skeleton surrounding the cells, which may be closed or partially or completely open to neighbouring cells or to the outside. The intrinsic properties come from those of the silicones with: 9 A reduction in the mechanical properties due to the small quantity of solid material and the high proportion of gas. 9 A reduction in the chemical behaviour due to the strong division of the material. The thin cell walls immediately absorb liquids and gases and are rapidly damaged. 309

Thermosets and Composites

These flexible foams have a broad service temperature range, a low density, a low flammability, an inherent low toxicity and low smoke emission levels and are chosen for specific applications such as: 9 Cushioning, fire blocking, insulation and gasketing in the mass transit, aerospace, automotive, industrial and institutional markets. 9 Vacuum cups, suction cups, rectangular vacuum pads for handling. 9 Foam seating in commuter trains and other mass transports. 9 Silicone foam coated adhesive tapes, foam coated fibreglass or aluminium sheets for heat-resistant protection. 9 Moulds for food. 9 Jaguar XJ6 soundproofing: a foam-in-place silicone is injected at some judicious points of the body. 9 A two-component silicone foaming at room temperature is proposed for prosthetics. Table 4.53 shows an example of foam properties. Table 4.53

Silicone foam: property examples

Density, g/cm 3

0.2

Tensile strength, MPa

0.17

Elongation at break, %

60

Service temperature range, ~ Compression set, compressed 50% for 22 hours at 100 ~

- 5 0 - +200 %

5

Dielectric constant

1.3

Arc resistance, s

123

Oxygen index, %

34

Syntactic foams

Syntactic foams are composites made up of micro-balloons or hollow macrospheres bound into a silicone matrix. The silicone ones have very specific applications for electronics. 4.7.9 Specific ISO standards concerning silicones

ISO 8096-2:1989 Rubber- or plastics-coated fabrics for water-resistant clothing - Specification - Part 2: Polyurethane- and silicone elastomercoated fabrics ISO 14949:2001 Implants for s u r g e r y - Two-part addition-cure silicone elastomers (available in English only) 4.7.10 Trade name examples

Bisco, CO HRlastic, Eccofoam SIL, Eccosil, Elastosil R HTV, L R & RTV. Fluorosilicone, Fluorosilicone sealant, Kolfocon, Magnifoam, Perm, 310

Detailed accounts o f thermoset resins for moulding and composite matrices

Permufocon, Powersil, Rhodorseal, Rhodorsil CAF, Rhodorsil Mix & Fix, Rhodorsil RTV, RTV Fluorosilicone, RTV Silicone, Semicosil, Silastic RTV, Silbione, Silicon Molding Compounds, Silicosehl, Silopren, Sterafocon, Wilofocon. 4.7.11 Property tables

The results in Tables 4.54 to 4.62 relate to examples only and cannot be generalized. Table 4.54

Silicone resins for electronics and optics: property examples Silicone resins for electronics

Density, g/cm 3

1.8-1.9

Shrinkage, %

0.4-0.7

Water absorption, 24 h, %

0.1

Shore hardness, D

40-50

Tensile strength, MPa

25-35

CUT unstressed, ~

<260

Peak temperature, ~

350

Thermal conductivity, W/m.K

0.5-0.8

Coefficient thermal expansion, 10-5/~ Minimum service temperature, ~

1.5-5 ..........................................

~5--~0

Volume resistivity, ohm.cm

1015

Dielectric constant-

3-4

Dissipation factor, 10-4

.................

10-30 Silicone-acrylate resins for optics

Density, g/cm 3

1.1-1.13

Water absorption, %

1.3-1.6

Shore hardness, D

83-88

Light transmittance (>400 nm) with UV absorber (200-400 nm)

>95 %T <0.2%T

Refractive index, n D

1.46-1.47

Wetting angle (sessile drop) Oxygen permeability (Fatt Units, 32 ~ Residual monomer, % Cytotoxicity Ocular irritation

<25 ~ <30 ~ 11-54 <0.5 Non-toxic Non-irritating

CUT: Continuous use temperature at unstressed state 311

Thermosets and Composites

Table 4.55

Glass fibre reinforced silicone resin laminates: property examples

Rockwell hardness, M

105

Tensile strength, MPa

140

Flexural strength, MPa

210

Flexural modulus, GPa

11

Compression strength, MPa

350

Notched impact D 256, J/m

700

CUT unstressed, ~

220

Thermal conductivity, W / m . K

0.3

Coefficient thermal expansion, 10-5/~

0.7

Dielectric constant

4.5

Dissipation factor, 10-4

180

Arc resistance, s

240

UL94 rating

HB

Table 4.56

HVR silicones: Property examples Low hardness

Medium hardness

Cable sheathing

Cable sheathing Super heat resistant

Density, g/cm 3

1.1-1.2

1.2-1.4

1.6-1.7

1.2-1.3

Shore hardness, A

35-50

60-80

65-70

60-70

Tensile strength, MPa

7-12

6-12

3.5-9

9-11

Elongation at break, %

350-800

150-600

100-200

300-600

CUT unstressed, ~

180-250

200-260

250

300

-110--50

-110--50

--60

-60

Minimum service temperature, ~ Resistivity, ohm.cm Dielectric constant

1014-1016

1014-1016

1014-1015

1015

3

3

3-4

3-4

Loss factor, 10-4

4-17

2-100

10-100

40

Dielectric strength, kV/mm

22-27

20-25

20-25

22-30

Oxygen index, %

23-30

23-30

30

28

CUT: Continuous use t e m p e r a t u r e at unstressed state General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. l f the fillers are adapted, the chemical properties are the same as the silicone matrix. Light

Good behaviour

Weak acids

Good behaviour

Strong acids

Poor resistance

Weak bases

Good behaviour

Strong bases

Poor resistance

312

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.56

HVR silicones: Property examples Low hardness

Medium hardness

Cable sheathing

Cable sheathing Super heat resistant

Solvents

Generally poor resistance but after redrying, silicones often recover a large part of their initial properties

Water

Generally, good resistance but possibly attacked by highpressure water vapour

Food contact

Suitable grades

Table 4.57

LSR silicones: property examples Low hardness

Medium hardness

Carbon filled conductive LSR

Density, g/cm 3

1-1.1

1-1.1

1.1

Shore hardness, A

20-35

40-70

40-50

Tensile strength, MPa Elongation at break, % Compression set 22 hours at 175~ Rebound resilience, % Thermal conductivity, W/m.K

%

4-9

4-9

4-6.5

450-1000

250-850

400-500

20

20-25

50

50--60

0.2-0.4

Volume resistivity, ohm cm

1015

1015

Dielectric constant

3-4

3-4

Dissipation factor, 10-4

25

25-35

Dielectric strength, kV/mm

22-25

22-27

Oxygen index, %

23-28

23-28

10-102

CUT: Continuous use temperature at unstressed state General chemicalproperties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. I f the fillers are adapted, the chemical properties are the same as the silicone matrix. Light

Good behaviour

Weak acids

Good behaviour

Strong acids

Poor resistance

Weak bases

Good behaviour

Strong bases

Poor resistance

Solvents

Generally poor resistance but after redrying, silicones often recover a large part of their initial properties

Water

Generally, good resistance but possibly attacked by highpressure water vapour

Food contact

Suitable grades

313

Thermosets and Composites

Table 4.58

RTV silicones: property examples Two-part Low hardness

Two-part Medium hardness

1-1.5

1-1.5

0.1-0.8

0.1-0.8

8-35

40-70

1.8-7.5

2.5-7

Elongation at break, %

200-700

100-350

CUT unstressed, ~

180-260

180-260

Peak temperature, ~

260-315

260-315

Thermal conductivity, W/m.K

0.2-0.4

0.2-0.4

15-27

15-27

-115 - -50

-100 - -50

1012-1015

1012-1015

1-4

1-4

Dissipation factor, 10-4

2-200

2-200

Dielectric strength, kV/mm

15-20

15-20

One-part Low hardness

One-part Medium hardness

Density, g/cm 3

1-1.3

1.1-1.4

Shrinkage, %

0.3-1

0.3-1

Shore hardness, A

15-35

40-70

Tensile strength, MPa

0.6-3.5

2-4.5

Elongation at break, %

180-700

120-240

CUT unstressed, ~

110-220

125-220

<260

<260

0.2-0.3

0.2-0.3

15-27

15-27

-110 - -50

-70 - -50

1013-1015

1013-1015

2-4

2-4

Dissipation factor, 10-4

5-100

5-100

Dielectric strength, kV/mm

10-20

10-20

Density, g/cm 3 Shrinkage, % Shore hardness, A Tensile strength, MPa

Coefficient thermal expansion, 10-5/~ Minimum service temperature, ~ Volume resistivity, ohm.cm Dielectric constant

Peak temperature, ~ Thermal conductivity, W/m.K Coefficient thermal expansion, 10-5/~ Minimum service temperature, ~ Volume resistivity, ohm.cm Dielectric constant

CUT: C o n t i n u o u s use t e m p e r a t u r e at unstressed state

314

Detailed accounts o f thermoset resins for moulding and composite matrices

Table 4.59

Silicone elastomers for electronics Epoxy modified silicone

Thermal dissipating silicone

1.2-1.9

1.9-2.4

Density, g/cm 3 Shrinkage, %

0.5

Shore hardness, A

68-70

70-80

Tensile strength, MPa

4-40

3-5

Elongation at break, %

10-60

85-100

190

200-260

0.2-0.3

0.5-1.5

CUT unstressed, ~ Thermal conductivity, W/m.K

Table 4.60

Silicone foams: property examples

Density, g/cm 3

Expanded R T V siliconefoam

Expanded R T V silicone foam

Syntactic silicone foam

0.13

0.2

0.3-0.75

Water absorption, 24 h, %

0.1

Shore hardness, A

< 55

Tensile strength, MPa

0.17

0.7-5

Elongation at break, %

60

100-300

CUT unstressed, ~

200

200

Peak temperature, ~ Thermal conductivity, W/m.K

260 0.045

0.05-0.15

Coefficient thermal expansion, 10-5/~

3

Minimum service temperature, ~ Volume resistivity, ohm.cm

-50

-60

1.3

1-2

1012

Dielectric constant

1

Dissipation factor, 10-4

10

Dielectric strength, kV/mm

2

100-200

Arc resistance, s

123

Oxygen index, %

34

Table 4.61

Fluorosilicone resins for optics: property examples

Density, g/cm 3

Fluo rosili cone-acrylate

Fluo rosilicone

1.12-1.15

1.14-1.15

Water absorption, %

0.6-0.7

<1.5

Shore hardness, D

81-86

84-86

>95 %T <0.2%T

>95 %T <0.2%T

Light transmittance (> 400 nm) with UV absorber (200-400 nm)

315

Thermosets and Composites

Table 4.61

Fluorosilicone resins for optics: property examples Fluorosilicone-acrylate

Refractive index, n D Wetting angle (sessile drop)

1.44-1.46

1.43-1.46

19 ~ - < 25 ~

<10 ~ - < 25 ~

30-90

25-50

<0.5

<0.5

Oxygen permeability (Fatt Units, 32 ~ Residual monomer, % Cytotoxicity Ocular irritation

Table 4.62

Fluorosilicone

Non-toxic

Non-toxic

Non-irritating

Non-irritating

Fluorosilicone elastomers: property examples Low hardness

Hot cured fluorosilicone

Density, g/cm 3

1.4

1.3

Shore hardness, A

35

47

Tensile strength, MPa

2

4

Elongation at break, %

175

300

CUT unstressed, ~

260

205

Tensile strength retention after: 14 days at 204 ~ 3 days at 225 ~

%

68

%

81

Coefficient thermal expansion, 10-5/~

15

Minimum service temperature, ~

-57

-70

Volume resistivity, ohm.cm

1013

1013

Dielectric constant

6-7

5-6

Dissipation factor, 10-4

60

30

Dielectric strength, kV/mm

13

19

General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. I f the fillers are adapted, the chemical properties are the same as the silicone matrix. Light

Good behaviour

Weak acids

Good behaviour

Strong acids

Poor resistance

Weak bases

Good behaviour

Strong bases

Poor resistance

Solvents

Generally, much higher resistance than silicones. Good behaviour with oils. Fair resistance to aliphatic hydrocarbons. Attacked by chlorinated solvents and ketones.

Water

Generally, good resistance but possibly attacked by highpressure water vapour

316

Detailed accounts of thermoset resins for moulding and composite matrices

4.8 Polycyanates or cyanates esters (Cy) Cyanate ester resins are obtained from aromatic prepolymers containing highly reactive cyanate functional groups that cyclotrimerize exothermically to form triazine ring structures which result in a tightly crosslinked structure. The polycyanates are very specific resins used as composite matrices in space and electrical industries. 4.8.1 Generalproperties Advantages

Elevated service temperatures, fatigue behaviour, low outgassing suitable for space hardware, good mechanical properties, fire resistance of suitable grades, good behaviour in wet medium, low-temperature behaviour, low or controlled dielectric constant and loss factor, radiation resistance, reduced microcracking during thermocycling, fair coefficient of thermal expansion, easier processing than polyimides, possibility of RTM and compression moulding. Drawbacks

Unusualness of the product, high-temperature and long-cycle processing, price. Special grades

They can be classified according to the type of processing, specific properties, targeted applications: 9 For specific processing: UD manufacture, prepregs, filament winding, RTM, adhesive films, syntactic foams, syntactic films, two-component. 9 For specific properties: toughened, super heat-resistant, fire resistant, low or controlled dielectric constant, low outgassing, minimal microcracking during thermocycling, low moisture absorption, low shrinkage, low-temperature curing, electrostatic dissipation, low viscosity, modified tack, epoxy modified. 9 For specific applications: electricity and electronic, aeronautics and space. Cost

The costs are estimated in the region of 4E60 and more per kilogram. Processing

Laminating, compression moulding, filament winding, RTM, vacuum bag, syntactic foaming. Applications [see Chapter 2 for further information]

Consumption The consumption of cyanates by the industrialized countries is very low and is not listed in the economic statistics. 317

Thermosets and Composites

The cyanates are thermosets of very high performances used as matrices for high-tech composites in space and electricity industries. The applications are always very specific. The price limits the use of the cyanates to well-targeted applications taking advantage of their highly specific performances. Some examples of operational or development parts are listed below.

Aeronautics 9 9 9 9

Structural elements for satellites, airframes and fuselages of aircraft and missiles; struts, secondary structures, housing. Structures and flywheel systems for space. Optical benches for telescopes. High thermal conductivity materials for thermal management of space electronic packages, heatpipe panels, radiators.

Electricity, electronics 9 9

Structural elements for radomes electromagnetic devices. RF and microwave equipments.

and

other

dielectric

and

Syntactic foams 9

Low or controlled dielectric constant for component encapsulation.

4.8.2 Thermal behaviour

Initial behaviour

Glass transition temperatures are very variable ranging from 140 ~ to 370 ~ according to the grades, curing process and the moisture content: 9 For a defined grade, the glass transition temperature increases from 50 ~ during post cure. 9 A low-temperature curing grade with a cure time of less than 5 minutes at 80 ~ has a glass transition temperature of about 140 ~ 9 A specially designed resin has a glass transition temperature of 220 ~ after 10 seconds cure. Figure 4.33 plots an example of glass transition temperatures versus water content. For four examples, the mechanical property retentions, expressed in percentage of the room temperature values, depend on the reinforcement, varying between: 9 92-98% at 6 0 ~ 9 87-88% at 135 ~ 9 78-86% at 176 ~ 9 70-80% at 260 ~ These results relate to tested grades only and cannot be generalized. 318

Detailed accounts of thermoset resins for moulding and composite matrices

300

o

o 200 .,~

4

100

0

Water, % 0

1

2

Figure 4.33. Polycyanates: Examples of glass transition temperature versus water content

Long-term behaviour

The behaviour at high temperature depends on the duration. The continuous use temperatures in an unstressed state generally range from 176 ~ up to 260 ~ according to the grades, curing process and the moisture content. Higher peak temperatures can be tolerated. Low-temperature behaviour

The low-temperature behaviour is also good, allowing use t o - 2 1 0 ~ according to the grades and the stresses. 4.8.3 Mechanical properties

The mechanical properties are generally good at ambient and high temperature (tensile, flexural, compressive strengths) and allow structural applications in the composite forms for the advanced techniques: space, electronics, electricity. For two tested grades, in the absence of voids and bubbles, the water level has little effect on the mechanical performances, as seen in Figure 4.34. For high water levels, the bubbles and voids are too numerous and it is not possible to measure tensile strengths and other mechanical properties. 200 ~ ~ ?

.... C I ?

~ZI

:C

ii

~i

Z

~ i 84 84184184184184184184184184184184184184184 if: % i i s :::7/ 84 :~!

i

~

A 100

A

~,

A

AAk

04 0

Water, % 1

Figure 4.34. Polycyanates: Examples of tensile strength versus water content 319

Thermosets and Composites

Friction

The polycyanates are not especially intended for tribological applications. Creep

The creep is low enough to allow structural functions at high temperatures. Dimensional stability

The shrinkage is generally limited, the coefficient of thermal expansion is rather low, the creep is good, and the absorption of water or moisture is limited. Consequently, the dimensional stability is generally good. 4.8.4 Ageing Dynamic fatigue

The polycyanates resist cyclic loadings, which allows structural functions at high temperatures. High-energy radiation

Certain polycyanates are resistant to high-energy radiation. Vacuum outgassing

The vacuum outgassing of certain grades is sufficiently low to be usable in space. Fire resistance Fire retardant and low smoke emission grades are marketed. 4.8.5 Electrical properties The permittivities are, for example, 2.6 to 3 for frequencies of 2 GHz to 18 GHz with low loss factors of 50 * 10-4 to 60 * 10-4. These properties can be controlled by the choice of the fillers and reinforcements. The electrical applications are one of the main markets.

4.8.6 Syntactic foams Syntactic foams are composites made up of micro-balloons or hollow macrospheres bound into a plastic matrix. The polycyanate syntactic foams are used in specific electronic equipment for microwave and RF applications. They are available in both low-loss versions as well as controlled-loss versions. A few o f them are low-temperature curing (120 ~ and low shrink. They act as structural, dielectric and heat dissipating materials for applications such as: 9 High performance core structures, spacecraft, radomes, antennae; antenna pattern shaping. 9 Low or controlled dielectric constant encapsulation. 9 Specular attenuation. 9 Honeycomb edge fill and potting. 320

Detailed accounts of thermoset resins for moulding and composite matrices

Table 4.63 displays some property examples of polycyanate syntactic foams. Table 4.63 Polycyanate syntactic foams: property examples Density, g/cm 3

0.2-0.3

Tensile strength, MPa

2-7

Compressive strength, MPa

3-8

Coefficient of thermal expansion, 10-5/~

1.3

Glass transition temperature, ~

175-205

Continuous use temperature unstressed, ~

135-177

Peak temperature, ~

Up to 250

Dielectric constant at 10 GHz

1.2-3

Loss tangent at 10 GHz, 10 -4

40-4000

4.8.7 Trade name examples

Bryte Cyanate Ester, Cuming Cyanate Ester Syntactic, COI CE, Dow Polycyanate, FiberCote Cyanate Ester, Nippon Mitsubishi Granoc, YLA RS Polycyanates. 4.8.8 Property tables

The results in Tables 4.64 and 4.65 relate to examples only and cannot be generalized. Table 4.64 Polycyanate composites: property examples Reinforcement Tensile strength, MPa

Glassfibre

Carbonfibre

Quartz

395

410-2500

800-850

Tensile strength, MPa 90 ~ Tensile modulus, GPa

28-45 23

Tensile modulus, GPa 90 ~

70-476

30

5-6

Flexural strength, MPa

650

600

Flexural modulus, GPa

23

30

Compression strength, MPa

450-490

Compression modulus, GPa

25

Coefficient thermal expansion, 10-5/~

225-1100

630

63-400

30

-0.1-0.1

Dielectric constant 9 GHz

3.2

Dissipation factor at 9 GHz, 10-4

50

CUT: continuous use t e m p e r a t u r e in an unstressed state * transverse direction for U D and other anisotropic composites 321

Thermosets and Composites Table 4.65

Neat polycyanates: property examples 176~ service temperature

Toughened Hightemperature

Density, g/cm 3

1.2

1.2

Tensile strength, MPa

80

60-80

Elongation at break, %

2.5-5

Tensile modulus, GPa

3

3.5

Flexural strength, MPa

100-130

120--130

Flexural modulus, GPa

2.5-3.3

3.5

Compression strength, MPa

322

Compression modulus, GPa

3.5

CUT unstressed, ~

176

>176

280

Glass transition, ~

200-254

161-254

370

5

4-5

5

Coefficient thermal expansion, 10-5/~ Minimum service temperature, ~

to -210

Dielectric constant 2 GHz to 18 GHz

2.7

2.6-2.8

3.2

Dissipation factor, 10-4

50

50-60

50

CUT: continuous use t e m p e r a t u r e in an unstressed state

4.9 Other thermosets 4.9.1 Dicyclopentadiene (DCPD)

The DCPD resins are obtained by the metathesis reaction of purified dicyclopentadiene containing catalysts in one part and co-catalysts in a second part. This polymer targets the manufacture in medium series of large parts by reaction injection moulding (RIM). 4.9.1.1. General properties Advantages

Good mechanical properties, including impact strength at -40 ~ low specific gravity of 1.03, fairly good resistance to acids and bases; low viscosity of the raw material allowing fast production cycles in RIM process of complex shapes with large thickness variations, suitable for the manufacture of large and thick parts, class-A finish. Drawbacks

Restricted distribution, limited number of grades, reduced usable processes, relatively high coefficient of linear thermal expansion. Eventual odour caused by residual DCPD monomer can be reduced by more complete polymerization. SpeciaI gra des

For in-mould coating, VO, non-halogen flame-retardant, new catalysts. 322

Detailed accounts of thermoset resins for moulding and composite matrices

Cost It is very difficult to provide explicit prices because of the restricted distribution. They evolve roughly in the range of ~5 to 7 per kilogram. Processing The main processing method is RIM but some developments concern R T M and centrifugal casting. Applications [see Chapter 2 for further information]

Consumption D C P D consumption is not listed in the economic statistics. It is estimated that the consumption progression exceeds the rate of total plastic consumption. The applications are focused on: 9 Large parts up to 3 m long, 2 m wide, 1 m high, surface areas up to 13 m 2, thickness up to 30 cm weighing from 5 kg up to 500 kg for production volumes ranging from 2000 to 30 000 parts per year. 9 Exterior parts with class-A finish for automotive, transport, heavyvehicles working in harsh environments. 9 An alternative to fibre reinforced plastics (FRP). Replacement of spray-up glass fibre reinforced unsaturated polyester leads to weight saving without additional cost. o Although D C P D has a lower tensile modulus than FRP, it is more flexible and better resists impact damage. D C P D has a notched Izod impact of the order of 400 J/m at room temperature and 100 J/m at -40 ~ It also has a good chemical resistance. o The low mould cavity pressure of 1 to 3 bar translates to low pressure requirements for the moulds. Production moulds are typically machined in aluminium, nickel shell or cast aluminium. Prototype parts can be moulded in epoxy/polyester moulds. 9 An alternative to engineering thermoplastics whose mechanical properties are similar with weight savings and no additional cost in large parts weighing 10-100 kg, surface area in 1 m 2 range, which is the upper end for cost and size capability for standard injection moulding. Cycle times are typically 4 ~ minutes. Injection time is about 10-20 seconds, and cure time is about 1-2 minutes. Unlike most thermoplastics, D C P D can be moulded in parts up to 30 cm thick. Some examples of operational or development parts are listed below.

Automotive 9

Exterior parts with class-A finish for niche vehicles, tractors, tonneau covers for pick-up trucks, fenders for John Deere farm tractors; heavyvehicle exterior components such as roofs, hoods, side-chassis and roof fairings; vertical extenders, sun visors, bumpers, lower bumper air dams, fenders, and door skins for agricultural and construction vehicles, articulated dump trucks. Weight examples: a hood weighs 323

Thermosets and Composites

,,

9

about 60 kg; a bumper, 15 kg; fairings, 10 kg each; side extenders, 5-10 kg apiece; a sun visor, 5-10 kg; and roof fairing, 30-40 kg. Auto bumpers for brand-new car models or niche vehicles. Nissan and Toyota use D C P D to mould bumper fascias when volumes are smaller and then switch to TPO as production volumes grow. Rail and freight components.

Electricity, electronics 9

Large electronic cabinets measuring around 300 1.

Industrial 9 9 9 9

Corrosion-resistant covers for chlorine/caustic reactor cells around 3 m by i m by i m weighing from 250 to 500 kg. Unreinforced pipes. Large fittings for water pipes. Large (200 kg) water-treatment vessels.

Packaging 9 Trays for carrying automotive engines, transmissions, and aftermarket parts. 9 1000 and 1500 1 containers for hazardous wastes. 9 Custom containers and pallets.

Housing equipment 9 9

Residential bathroom units, sink basins, bathtub pans, draining floor pans and ceiling materials. Combined septic tanks.

Sports, leisure and gardening equipment 9

Lawnmower housings, engine hoods, grass baskets, golfcart bodies.

4.9.1.2. Thermal behaviour and ageing Initial behaviour

The H D T A (1.8 MPa) are moderate, for example 105-115 ~ Typical glass transition temperatures are 138 ~ and more. Long-term behaviour

The behaviour at high temperature depends on the duration. The continuous use temperatures in an unstressed state are generally 110 ~ but higher peak temperatures can be tolerated. Low-temperature behaviour

The behaviour is good at low temperatures with notched Izod impact of more than 100 J/m at -40 ~ for general-purpose grades. These results relate to tested grades only and cannot be generalized. Fire resistance

Fire-retardant grades are marketed, some are halogen-flee. 324

Detailed accounts of thermoset resins for moulding and composite matrices

Chemicals

The acid and base behaviour is good. 4.9.1.3. Mechanical properties

The mechanical properties are generally good at ambient temperatures. Friction

The DCPDs are not especially intended for tribological applications. Dimensional stability

The shrinkage and the absorption of water or moisture are generally limited but the coefficient of thermal expansion is rather high. 4.9.1.4. Electrical properties

DCPD is insulating and absorbs little water. 4.9.1.5. Joining

Machining is easy and it is possible to mould around inserts. The majority of glues are suitable and the choice depends on the application. A simple solvent cleaning is generally sufficient. 4.9.1.6. Trade name examples

Metton, Pentam, Telene 4.9.1.7. Property tables

The results in Table 4.66 relate to examples only and cannot be generalized. Table 4.66

Dicyciopentadiene: property examples

Generalpurpose DCPD Density, g/cm 2

1.03

Fire retardant VO

1.03

1.2

Shrinkage, %

0.9

0.7

Water absorption, %

0.12

Shore hardness, D

84

Rockwell hardness, R

114

Tensile strength at yield, MPa

46

Tensile modulus, GPa

47

45

1.9

2

Tensile elongation at yield, %

4

5

4

Flexural strength at 5 % strain, MPa

75

70

74

1.8-1.9

2

2

58

58

330

460

400

140

106

53

Flexural modulus, GPa Compression strength, MPa Notched Izod impact at 23 ~ Notched Izod impact at -40 ~

J/m J/m

325

Thermosets and Composites Table 4.66

Dicyclopentadiene: property examples

GeneralpurposeDCPD Shear strength, MPa

49

Poisson's ratio at 23 ~

0.41

Poisson's ratio at -40 ~

0.36

H D T A (1.8 MPa), ~

Glass transition temperature, ~ Coefficient thermal expansion, 10-5/~

Fire retardant VO

0.39

0.39

115

108-120

105

165

>138

8

8.8

Volume resistivity, ohm.cm

1016

Dielectric constant

2.5

Dissipation factor, 10-4

81

Dielectric strength, kV/mm

31

UL94 fire rating

HB

V0

4.9.2 Furans

The furan resins are obtained by homopolymerization from furfuryl alcohol or by copolymerization with formaldehyde. This polymer targets the anticorrosion market and sand binding for foundries. The structural parts and composite applications are very modest. 4.9.2.1. General properties Advantages

Excellent resistance to strong alkalis and acids containing chlorinated organics but not suitable for oxidizing chemicals such as chromic or nitric acids, peroxides or hypochlorites. Drawbacks

A very restricted use in structural applications as composites, requires special techniques that differ from those used with polyester and epoxy. Special grades

For spray-up, filament winding, fire-retardant. Processing

The main processing method is spray-up moulding. Consumption

Furan consumption is not listed in the economic statistics and the part moulding is a tiny share of the total consumption. Applications

The main applications are outside the framework of this book: 9 Foundry core manufacture by sand binding. 326

Detailed accounts of thermoset resinsfor moulding and composite matrices

9 Anticorrosive linings, mortars, cements and grouts. For the relevant applications, the furan resins are used for: 9 Anticorrosive inner liners reinforced with glass fibre for anticorrosive vessels, fittings and so on. Core and external layers are made of reinforced epoxy, unsaturated polyester, vinylester processed by spray-up or filament winding to ensure the structural functions. 4.9.2.2. Properties and ageing Mechanical properties

Generally, the mechanical properties are modest and the structural functions are ensured by other means. In the composite inner liners, the glass fibre levels are often low to have the maximum anticorrosive effect. Consequently, the mechanical performances are rather low. Heat behaviour

The high-temperature behaviour depends on the duration. Generally, the continuous use temperatures in an unstressed state are in the range of 100 ~ to 120 ~ Chemicals

Furan resins are claimed to have excellent resistance to strong alkalis and acids containing chlorinated organics but are not suitable for oxidizing chemicals such as chromic or nitric acids, peroxides or hypochlorites. 4.9.2.3. Trade name examples

Hetron 800, QuaCorr 1001, 1300, 1329, 1340.

References Technical guides, newsletters, websites 3M, Akzo Plastics, Allied Signal, Allrim, Amcel,Amoco, Arco Chemical,Astar, Atochem, Bakelite GmbH, BASE Bayer, BF Goodrich, BIP, Bisco, BP Chemicals, Bryte, Ceca, Celanese, Ciba, Cray Valley, Culver City Corp, Degussa, Devcon, Dow, DSM, Du Pont de Nemours, Dynamit Nobel, Eleco, Emerson & Cumming, EMS, Epotecny, Exxon, Ferro, Ferruzzi, FiberCote, Framet Futura, General Electric Plastics, General Electric Silicones, Hexcel, Hoechst, Htils, ICI, Irathane, Isomeca, Kommerling, La Bak61ite, Loctite, Lohmann,Mecelec,Menzolit,Mitsui Chem,Monsanto,Montedison,Naphtachimie,Neste, Nief Plastic, Nippon Mitsubishi, Nonacor, Norflys, Orkem, Owens Corning, Perstop, Phillips Petroleum, PPG, PRW, Raschig, Recticel, Rhodia, Rh6ne Poulenc, Rohm, Scott Bader, Shell, Sika, Sintimid, SNIA Tecnopolimeri, SNPE, Solvay, Stratime, Symalit, Synres, Synth6sia, T2L, Technochemie GmbH, Telenor, Thieme, Toray, Tramico, Tubize Plastics, Tubul am, Ube, Union Carbide, Uniroyal,Vetrotex,Vyncolit,Wacker,Wilson Fiberfil,YLA.

Reviews [1] [2] [3] [4]

Plastics Additives & Compounding (Elsevier Science) Modern Plastics Encyclopaedia (McGraw-Hill Publications) Modern Plastics International (Canon Communications LLC, Los Angeles, CA, USA) Reinforced Plastics (Elsevier Science)

327

Chapter 5

Thermoset processing

Thermosets and Composites

The uncured thermosets are in a solid, liquid or pasty state that leads to specific processing methods, as shown in Figure 5.1. The processes used for the thermoplastics are modified for the thermosets because: 9 It is necessary to heat for a sufficient time after shaping to crosslink the thermoset so that it solidifies, gains cohesion and good final properties. 9 Extrusion is used with specific polymers such as silicone elastomers. Pultrusion is used for composite processing. 9 The irreversible formation of a three-dimensional network during hardening makes the thermosets unavailable for thermoforming, and welding. Boiler-making is very limited. Several thermoset processing methods are used for composites and are also examined in Chapter 6.

Thermosets ]

Solid

]

[[

Liquid or pasty

Compressionmoulding

I

-~

Casting

-~

Transfer moulding

[

-~ LIM - Liquid injectionmoulding

-~

Injection moulding

[

- • R- Reaction I M injectionmoulding

-~

Extrusion

[

-~

Rotationalmoulding

-~

Composites

[

-~

Foaming

-~

Composites

Figure 5.1. Thermoset processing methods

5.1 Solid thermoset processing Thermosets in a solid form can be moulded by three different methods: 9 Compression 9 Transfer 9 Injection. In all cases: 9 The part sizes are limited by the mould size and the press power. 9 The parts are isotropic if the material is isotropic. 9 The whole surface of the part is well finished. 9 Each mould cavity has the shape of the part to mould corrected by the shrinkage coefficient of the material at the moulding temperature.

330

Thermoset processing

In the three cases, the suitably compounded resin with its hardener and other ingredients is heated to induce" 9 Plasticizing, which allows compaction and shaping. During this operation it is necessary to control the heating and the duration so that developing hardening does not prevent shaping. 9 The chemical reaction of hardening, which will lead to solidification, cohesion and development of the optimal final properties. Excessive heating can cause degradation, which will result in a mechanical property decrease after reaching an optimum. The parts can be postcured after de-moulding. A few thermosets, such as silicone elastomers, can be also extruded. 5.1.1

Compressionmoulding

The required quantity of thermoset is compressed at high pressure into the hot cavity space between the two parts of the mould: 9 The matrix, attached to the lower plate of the press 9 The stamp, fixed to the upper plate of the press. Figure 5.2 shows the principle of compression moulding.

Figure 5.2. Principle of the compression moulding 331

Thermosets and Composites

The contact with the hot mould plasticizes the material, which, by the pressure applied, takes the form of the cavity. The prolongation of the heating causes the reaction of hardening, which leads to part solidification and allows de-moulding. Certain additional operations can be necessary: 9 Possible drying of the resin at a low enough temperature so that hardening doesn't start. 9 High-pressure preforming into pastilles to ease feeding the mould. 9 Pre-heating of the pastilles immediately before mould feeding to improve the temperature homogeneity within the bulk parts and to accelerate the hardening. 9 Outgassing at the beginning of moulding if the material produces gases. 9 Finishing and deflashing of the parts. The heat-insulating properties of polymers cause some problems: 9 The temperature of the mould is slowly transmitted within the thermoset. If the part is rather thick, the hardening of the surface is highly advanced by the time hardening starts within the bulk. 9 If there are broad thickness variations, the thin walls crosslink much more quickly than the thick walls, making them susceptible to warping. 9 Moulding by compression is particularly unfavourable if there is a big temperature difference between the temperatures of the pastilles and the mould walls. Any gases produced during curing must be allowed to escape or they will induce internal stresses. Compression moulding: 9 Yields low output rates. 9 Needs few investments: the mould and press are relatively inexpensive. 9 Needs high labour costs. 9 Is consequently suited for small and medium outputs. 9 Is not especially intended for thick parts because of the low thermal conductivity of the polymers. 9 Risks inducing voids and internal stresses if some released gas cannot escape. 9 Does not adapt well to the use of inserts. 9 Often needs a finishing step. 5.1.2 Compressiontransfermoulding Here, the compression mould is preceded by a heated chamber (transfer chamber) in which one deposits the desired quantity of preheated material. This is then driven out in the compression mould by a ram. The transfer chamber can feed several cavities, which simplifies mould feeding. 332

Thermoset processing

Figure 5.3 shows the principle of the compression transfer moulding. The residence time in the transfer chamber increases the thermoset temperature before its entry into the cavity of the compression mould. The high pressure due to the transfer from the chamber to the mould cavity produces mechanical work, which plasticizes the material and homogenizes its temperature. Consequently, compared to compression moulding, transfer moulding has certain advantages: 9 The quality of thick parts is particularly improved. 9 Production rates are generally higher. 9 Suitability for medium outputs. 9 Inserts are easy to use due to the plasticizing effect of transfer when the moulding starts. 9 Improvement of the tolerances in the closing direction if the design of the mould and its closing is suitable.

Figure 5.3. Principleof the compression transfer moulding 333

Thermosets and Composites

9

Reduction of the finishing operations if the design of the mould and its closing is suitable. On the other hand, transfer moulding presents some drawbacks: 9 More expensive special presses allowing independent actuating of the transfer plunger and the closing/opening of the mould. 9 In certain cases, material flow during transfer can deteriorate the structure of the material if the crosslinking reaction has started. This involves a reduction in the impact strength, but this is often counterbalanced by the better homogeneity of the material. The output rates, mould and press prices, and labour costs of transfer moulding are halfway between compression and injection moulding. 5.1.3 Injection

moulding

An injection moulding machine, see Figure 5.4, comprises three principal parts: 9 An extruder with a heating device for resin plasticizing or melting. The screw design and the temperatures depend on the injected material. Some thermosets with poor flow require a forced feeding system. 9 A ram system allowing introduction under high pressure of the dosed material into the mould. On some types of injection machine, the screw also acts as the ram. 9 A mould with a heating device to allow the hardening reaction, which will give part solidification and allow its release from the mould. The mould can be mono or multi-cavity. Figure 5.4 shows the principle of injection moulding.

Figure 5.4. Principle of the high-pressure injection moulding 334

Thermoset processing

In addition to the advantages of transfer moulding, injection ensures the automation of the feeding step. Injection moulding" 9 Permits total automation of the process and high output rates. 9 Has the highest mould and press prices. 9 Has the cheapest labour costs. 9 Normally, removes the need for finishing. 9 Is suited for mass production. 9 The optimization of the moulding parameters can be difficult and part warpage and shrinkage are sometimes difficult to predict. 9 Apart from the particular cases of resins filled with fibres and other acicular or lamellar fillers, the parts are isotropic. 5.1.4 Extrusion

Extrusion is the shaping of a plastic by pushing the plasticized or melted material through a die, and possibly a punch forming an air-gap, having roughly the form of the final section of the profile. The whole of the necessary equipment constitutes an extrusion line, which includes: 9 The extruder, see Figure 5.5, generally with a rotating screw that pushes, heats, plasticizes, homogenizes and pressurizes the material before it passes through the die. 9 The die and possibly the punch, which will give the desired form to the material flow. 9 The curing device, which heats the profile to cure it. 9 Ancillary equipment including cooling equipment and the pulling device that ensures the drive of the cooled section. Figure 5.5 shows the principle of extrusion.

Figure 5.5. Principle of the extrusion 335

Thermosets and Composites

5.2 Liquid thermoset processing Thermosets in liquid form can be moulded by: 9 Simple casting 9 Liquid injection m o u l d i n g - LIM 9 RIM 9 Foaming 9 Rotational moulding 9 Composite processes. One or two steps are involved, according to whether the thermoset is of one- or two-part type: 9 For this step, it is necessary to mix the resin and the hardener correctly in the right proportions, mixing either by batch manually or using an industrial mixer, or continuously using dosing mixers. 9 Crosslinking to create a three-dimensional network irreversibly. It can be hot or room temperature cured and the products can possibly be heated before moulding to accelerate the cycles and to allow the use of resins of higher viscosity. Parts can be subsequently post-cured after de-moulding. 5.2.1 Casting The liquid resin is cast by simple gravity without pressure in the open or closed mould, possibly containing a reinforcement. For batch processes, it is often necessary to deaerate the entrained air. The main advantages and drawbacks of simple liquid resin casting in an open or closed mould are: 9 The part sizes are limited by the mould size. 9 Reinforcements can be arranged in the mould before casting. 9 The parts are isotropic with neat resin or with isotropic reinforcements. 9 The aspect is finished for one part surface for open moulding, for the whole part surface for closed moulding. 9 A finishing step is often essential. 9 The moulds are cheap and there is no press. 9 The labour costs are high. 9 The output rates are low. 9 The process is suited for small and medium outputs. 5.2.2 Liquid injection moulding (LIM) The process principle is similar to injection moulding but the equipment is different. The main advantages and drawbacks of LIM are: 9 The total automation of the process and the high output rates. 9 The high mould and press prices. 336

Thermoset processing

9 The cheapest labour costs. 9 Normally, removal of the finishing step. 9 The suitability for medium and mass production. 9 The possible difficulty to optimize the moulding parameters and to predict the part warpage and shrinkage. 9 The part isotropy, apart from the particular cases of resins filled with fibres and other acicular or lamellar fillers. 5.2.3 Reaction injection moulding (RIM)

An injection unit doses and mixes the thermoset resin and catalyst. The mix is discharged under pressure, through an injection cone, into the closed mould. The injection pressure is not negligible and the moulds must be rather rigid and resistant. The precision of the cavity and the quality of its surfaces govern the precision and finish of the parts. In the alternative method, R R I M - Reinforced Reaction Injection Moulding, the resin is reinforced with fibres. Figure 5.6 shows the principle of RIM. In the RIM process, dosage and mixing are automated but the investments for machines and moulds are heavier than for casting.

Figure 5.6. Principle of the RIM: Resin Injection Moulding 337

Thermosets and Composites

The main advantages and drawbacks of the low-pressure R I M or R R I M injection moulding processes are: 9 The limited part sizes according to the mould size. 9 The possibility to arrange the reinforcements in the mould before injection. 9 The isotropy of the parts with neat resin or isotropic reinforcements. 9 The excellent aspect quality for the whole part surface. 9 The necessity to have pressure-resistant moulds, which are more expensive than for casting. 9 The investment in a press and a mixing/injection unit. 9 The moderate labour costs. 9 The suitability for medium range outputs. 5.2.4 Rotational moulding

The centrifugal force induced by the rotation of the mould is used to splash the resin on the inner side of the mould. Figure 5.7 shows the principle of rotational moulding for a cylindrical tank. This process is suitable, for example, for liquid D C P D . In principle: 9 The right amount of the compounded resin is filled in the closed mould, which is possibly heated. 9 The mould is rotated uni- or bi-axially possibly in an oven. 9 After hardening, the mould is cooled and the part is de-moulded. Advantages of the process: 9 The external part face is generally smooth with good surface details. 9 The mould and tool costs are rather moderate. 9 The investments are reasonable. 9 The process is convenient for short and medium production runs.

Figure 5.7. Principlofh~otational moulding of a cylindrical tank 338

Thermoset processing

Disadvantages of the process: 9 Discontinuity. 9 The choice of resin is limited. 9 Relatively slow. 5.2.5 Foaming

Generally, lightweight foams are produced by a few specialists on specific equipment with customized methods including the addition of blowing agents or gas injection. The structural foams are more widespread and are processed on less specific equipment by expansion in situ of blowing agents. Syntactic foams are composites made up of micro-balloons or hollow macrospheres bound into a plastic matrix. 5.2.6 Composite processes

The processes are numerous and differ in their technical and economic possibilities, for example: 9 Atmospheric moulding processes: hand lay-up, spray lay-up 9 Liquid moulding: RRIM, RTM, impregnation, infusion... 9 Solid-state moulding: compression and injection, SMC, BMC, ZMC... 9 Prepreg systems 9 Bag moulding 9 Filament winding 9 Centrifugal moulding 9 Continuous sheet manufacture 9 Pultrusion 9 Sandwich composites... Some composite processes allow the manufacture of unlimited size parts but for the others, as for thermoset moulding, the sizes are limited by: 9 The equipment power 9 The sizes of moulds, dies, autoclaves, winding machines, presses, bags, pultrusion machine... The processing of composites is detailed in Chapter 6.

5.3 Thermoset machining Practically all the rigid thermosets are more or less easily machined by almost all the metal or wood machining methods after some degree of adaptation of the tools and processes: 9 Sawing, drilling, turning, milling, tapping, threading, boring, grinding, sanding, polishing, engraving, planing... 339

Thermosets and Composites

9

The low thermal conductivity and the decrease of the mechanical characteristics at elevated temperature limit the machining temperature and it is necessary to cool and reduce the tool feed motion. 9 Machining damages the surface and it is sometimes necessary to make a coating. 9 For the anisotropic parts, machining can be more difficult in certain directions. 9 Carbon and glass fibres are very abrasive and quickly wear away highspeed steel tools. For intensive use, carbide or diamond tools are more suitable. Machining is suited for: 9 Prototypes and low output of complex parts made from blanks whose mould could be simplified. 9 Correction of parts with tight tolerances. 9 Thick parts.

5.4 Thermoset assembly Welding and solvent joining do not apply to the thermosets because of the crosslinking. 5.4.1 Adhesive

bonding

Joining using adhesives does not present particular difficulties and is used to assemble thermosets with plastics, composites or metals. Joining avoids the damage of the parts by drilling and allows an excellent distribution of the stresses. The parts can have structural functions if the adhesive is correctly chosen, and if one takes care: 9 To make the adhesive joints work in shear and not in peeling. 9 To have a sufficient surface stuck to bear the efforts. 9 To prepare surfaces well. In all cases, it should be r e m e m b e r e d that a permanent or cyclic loading is more detrimental than an instantaneous one. All types of adhesives are usable, for example: 9 H o t m e l t adhesives: The molten adhesive wets the surfaces of the plastics to be assembled and interlocks them while solidifying again on cooling. It is necessary for the materials to be assembled to tolerate the temperature of the molten adhesive. Joining is sensitive to the temperature which involves the melting of the adhesive joint. However, some hot-melt adhesives crosslink after joining and become less sensitive to heat. 9 N o n - r e a c t i v e s o l u t i o n a d h e s i v e s : The solvent wets the surfaces to be assembled, then evaporates involving the cohesion of the parts to be assembled by the adhesive joint. The heat behaviour is generally 340

Thermoset processing

moderate. If the solvent swells the materials to be assembled, there can be migration of materials and subsequent cracking by residual internal stress relaxation. Reactive adhesive: After wetting the surfaces to be assembled, there is polymerization of the adhesive joint. The heat behaviour can be better than with the preceding methods. 5.4.2 Mechanical assembly Clink and spring work, clamping, snap-fit

The impact strength of certain plastics allows their assembly by stretching as click-and-spring work, clamping, snap-fit, etc. To make this task easy, the assembly angle must be weak, generally lower than 30 ~ and the strain must be much lower than the elastic limit. Riveting

If the rivet is not of the same material as the part, it can later induce stresses by differential thermal expansion. Two techniques of riveting are used: 9 Hot: pre-heating of the rivet, and then crushing of the head. 9 With ultrasound: properties and durability are generally better. Screwing

Autotapping screws: the screw type, the diameter of the hole that receives the screw and the tightening torque depend on the plastic used. Repeated screwing and unscrewing are not advised. To a first approximation, and as examples, it is sometimes stated that: 9 The external diameter of embossing must be double the external diameter of the screw. 9 The length of the threads engaged in the embossing material must be twice as long as the external diameter of the screw. 9 Embossing should not be located on a welded line and the screw should not engage totally. The use of inserts allows repeated screwing/unscrewing, higher tightening torques and limits the risks of failures. Press fitting

Subject to a correct calculation of the diameters, the press fitting of metal and plastic parts gives good results. Durability is conditioned by the creep behaviour of the plastic. The metal elements must be round, smooth, clean and the metal must be compatible with the selected plastic. Embossing must be distant from weld lines and the moulding must be particularly careful to limit the residual stresses. 341

Chapter 6

Composites

Thermosets and Composites

6.1 Definitions The composite materials treated here are made of: 9 A thermoset or thermoplastic matrix or binder 9 A nonmiscible reinforcement closely bound to the matrix or the binder: fibres of high aspect ratio (length versus diameter), wires, mats, fabrics, foams, honeycombs, plywood and so on. The hybrids combine plastics or composites with other materials such as metal, wood, etc. Plastics filled with talc or other powders are not taken into account in this book. The composite properties depend on: 9 The matrix 9 The reinforcement 9 The adhesion between matrix and reinforcement. The reinforcement, as its name indicates, bears the stresses. When these reinforcements are not randomly distributed, which is often the case, the properties are anisotropic, being enhanced in the reinforcement direction. The matrix or binder ensures the cohesion of the composite, distributes and damps the impacts or stresses to protect the composite from the environment. The cohesion of the matrix and reinforcements can be damaged, even in the bulk, by moisture or chemical surface attack. The fluids can propagate to some depth by absorption and wicking: consequently it is important to protect the reinforcements from direct contact with the external environment by applying a resistant gelcoat. Composite processing can obtain practically all part shapes including: plane or warped surfaces; profiles; hollow parts; bulky parts; sheets, slabs and plates; parts with inserts, etc. Faced by the diversity of plastic composites and their fast evolution, the information here is deliberately general and treats the most widespread cases only. It will be essential for the designer to work in close cooperation with the producers and manufacturers to fix his final choice. 6.2 Reminder of some basic principles When designing composites, it is necessary to respect some essential rules: 9 Choose the reinforcement according to the loads: if the part properties must be 3D-isotropic, adopt a random reinforcement. If a 2D isotropy is sufficient it is possible to use a balanced woven or mat reinforcement. 9 Lay up the reinforcements according to the stresses so that they really withstand the loads: the planes of the reinforcements will be parallel to the tensile stresses, and perpendicular to the shear, flexural or compressive stresses. 344

Composites

9

Choose one or two gelcoats (if the two faces do not have the same functions) resistant to the environment and able to protect the matrix. 9 Choose a matrix compatible with the ambient conditions of use. 9 Take care to preserve the matrix or its gelcoat after moulding. If machining, polishing, or anything else damages it then remake a protective coating. 9 Proscribe the finishing treatments with products or temperatures incompatible with the matrix. Among the other elementary rules, we will quote" 9 Avoid significant thickness variations and maintain those within reasonable limits by arranging reinforcing ribs if the mechanical stresses are too high. By way of examples, we give the current thickness for some composite parts below: o 1.5 to 3 mm: casings for electric household appliances and electricity supply, automobile body parts. o 3 to 4 mm: sanitary elements. o 4 to 5 mm: hulls of boats, furniture supports. 9 Avoid sharp angles. 9 Draw sufficient draft angles to be able to demould. 9 Take care with the embossing and insert hole solidity, which could then be zones of maximum stresses. The processing methods will be selected according to the importance of the series, part sizes and targeted properties. Table 6.1 suggests some processes according to the part sizes and production outputs. These few elementary concepts are a simple reminder and we should remember that: 9 Computing software specifically developed for composites as available. 9 It is imperative that the part design and the processing study be done with the manufacturer who will manufacture the part. Table 6.1

Examples of the suggested process choice versus the part characteristics

Part size, max area in m 2

Thickness, mm

Output, units

Method

Examples o f parts

Limited

Limited

Mass production >10 000

High pressure injection

Electric & electronic parts

Up to 4

Limited

Medium output

Stamping

Automobile parts

Up to 5

1 to 6

Mass production

Hot compression moulding mats and preforms

Car body elements

Up to 5

2 to 10

Mass production

Hot compression moulding prepregs

Car body elements

1000 to 250 000

RRIM

Housings

200 to 10 000

Resin injection

Car body elements

Up to 10 Up to 15

i to 10

345

Thermosets and Composites

Table 6.1

Examples of the suggested process choice versus the part characteristics

Part size, max area in

Up to 15

m 2

Thickness, mm

Output, units

Method

Examples ofparts

3 to 10

500 to 20 000

Low temperature & pressure compression moulding

Car body elements

<5000

Autoclave

Aeronautics elements

Centrifugal moulding

Tubes, pipes

Up to 20 Up to 30

3 to 15

Limited section

3 to 20

Continuous

Pultrusion

Profiles

Limited section

1 to 4

Continuous

Continuous impregnation

Roof sheeting

Diameter up to 25 m with specific equipment*

1 to 10 and more

Low to medium outputs

Filament winding

Pressurized tanks

Virtually unlimited,

Unlimited, often

<1000

Hand lay-up

Ships

<300

2 to 10

Virtually unlimited

Unlimited, often 2 t o 10

<1000

Spray lay-up

Mine hunters

*Manufacture using specific material developed for a particular part

6.3 Composite mechanical performances according to the reinforcement type Although the reinforcements are intended to bear the loads, the matrices play a significant role in composite failure by damping sudden stress variations, by distributing the loads and by protecting the reinforcements. 6.3.1 Reinforcement by randomly distributed short fibres

Depending on the rigidity and the ductility of the matrix, when a stress is applied to a short glass fibre reinforced composite the following steps can be observed: 9 Cracking initiation of the resin around the fibres . Progressive loss of fibre/matrix cohesion 9 Propagation of cracks in the matrix 9 Rupture of fibres 9 Fibre stripping. All other things being equal, the composite strength increases with fibre length above a critical threshold up to a maximum, as shown in schematic in Figure 6.1. 346

Composites

performance

Fibre length Figure 6.1. Schematic curve of a performance versus fibre length

6.3.2 Reinforcement by arranged continuous fibres

The purpose of the following remarks is not to propose a calculation m e t h o d - excellent computer software programs exist for t h a t - but to show the broad strength range according to the composite structure and the service conditions. These examples cannot be used for design calculations. 6.3.2.1. Unidirectional reinforcement

The resistance of the composite in the reinforcement direction can be roughly estimated starting from a simple rule of mixtures, if the matrix transmits the load completely until failure: 13 = Vfibr e * 13 fbre + Vmatrix * 13matrix

where Vfibre and Vmatrix are the volume fractions of fibres and matrix; cyfibre and ~matrix are the strengths of fibres and matrix. For example, for a unidirectional (UD) epoxy resin/carbon fibre composite where Vfibre and Vmatrix " - 0 . 5 , 13matrix = 80 MPa, and 13fibre = 3530 MPa, the predicted strength is: cy = (0.5 * 3530)+ (0.5 * 80)= 1805 MPa The experimental result is 1760 MPa. In the transverse direction, the strength will be much lower, and at best equals that of the matrix. In the last example, the strength measured in the transverse direction is really 80 MPa. To play its role until failure, the matrix must have an elongation at break better than that of the reinforcement, that is to say: 347

Thermosets and Composites

9 9 9

3 to 5% for glass fibres 0.5 to 2% for carbon fibres 2 to 4% for aramid fibres.

6.3.2.2. Reinforcement with two orthogonal layers

For the reinforcement direction of one or other layer, the calculation method is the same as in the last example. For the thickness direction, the modulus of the reinforcement being very much higher (20 times for example) than that of the matrix, the matrix between the reinforcement layers is subjected to significant deformations that is sometimes qualified as "amplified strain". 6.3.3

General approximate method for strength estimation

Again, these examples cannot be used for design calculations. PPG in its Introduction to glass fibre reinforced composites proposes a calculation method for the strength estimate based on four principles: 9 Evaluation of the "contribution of glass fibres to strength" 9 Use of a coefficient (z assigned to the form of the reinforcement 9 Use of a coefficient [3 determined by experiments according to the length of fibres 9 Application of the law of mixtures. Evaluation of the "contribution of glass fibres to strength"

Taking into account the fragility of the fibre to abrasion, the risks of glass fibre breaking during processing etc., the contribution of glass fibres to the strength of the composite is fixed at a maximum of 2300 MPa in the most favourable case of a matrix with high elongation at break (3.5 to 5 %). For matrices of lower elongations, the contribution of glass fibres to the strength of the composite is reduced, for example: 9 2000 MPa for a matrix with 3% elongation at break 9 1750 MPa for a matrix with 2.5% elongation at break 9 1500 MPa for a matrix with a maximum 2% elongation at break. A n additional reducing coefficient of 0.9 or 0.95 can be assigned to the fabrics according to their armour or treatments such as those intended to remove size. Use o f a reduction factor assigned to the reinforcement form and loading direction

Some values of (z are given as examples according to the reinforcement and the relative direction of stresses: 9 1 for U D reinforcement and loading in reinforcement direction 9 0 for U D reinforcement and loading in orthogonal direction 9 0.5 for bi-directional reinforcement and loading in a reinforcement direction 348

Composites

9 9

0.25 for bi-directional r e i n f o r c e m e n t and loading at 45 ~ to the r e i n f o r c e m e n t directions 0.2 for multidirectional r e i n f o r c e m e n t in space.

Use of a coefficient 13 determined by experiments according to the fibre lengths Examples of coefficient [3 are indicated for neat and filled matrices: 9 0.25 for 10 m m fibre length and a filled matrix 9 0.45 for 30 m m fibre length and a filled matrix 9 0.6 for 30 m m fibre length and a neat matrix 9 0.55 for 50 m m fibre length and a filled matrix 9 0.65 for 50 m m fibre length and a neat matrix.

Application of the law of mixtures The law of mixtures is classically applied by replacing the strength of fibres by their [contribution to the strength] of the composite and by taking account of the and [3 coefficients: (Y = ~ * ~ * Vfibre* (y fibre + Vmatrix* (y matrix

Here (Yfibre is the [contribution to strength] of the glass fibres and not their strength.

Examples 1. Glass fabric reinforced unsaturated polyester composite

The weight fraction of fabric is 65 % Vfibr e = 0.46 Vmatrix = 0 . 5 4

= 0.5 in warp or weft direction The [contribution to strength] of glass fibres is valued at its m i n i m u m , that is 1500 M P a (Ymatrix = 8 0 M P a

cy = 0.5 * 0.46 * 1500 + 0.54 * 80 = 388 MPa This value significantly exceeds the value range r e c o r d e d in the literature but remains an indicative value, over-estimated, but usable in the absence of other, m o r e precise information. The law of mixtures can also be applied to the m o d u l u s leading to a calculated result of 18 GPa, which is in the value range met in the literature. 2. BMC glass fibre reinforced unsaturated polyester Vfibr e = 0 . 2 Vmatrix = 0 . 4 1 349

Thermosets and Composites

Length of fibres is 12 mm leading to a coefficient 13of 0.31 (x = 0.2 because the distribution of fibres is multidirectional in space (Ymatrix "- 6 0 M P a

The elongation at break of the resin is 2%, thus the minimal value of 1500 MPa is used for the [contribution to strength] of the glass fibres. = 0.2 * 0.31 * 0.20 * 1500 + 0.41 * 60 = 43 MPa This result is within the range recorded in the literature.

6.4 Composite Matrices At the outset of the composites industry, the matrices were unsaturated polyesters. Then other thermosets were developed but a few years ago the manufacture of thermoplastic composites began and its development is now faster than that of thermoset-based composites. At present, the plastic consumption for matrices is roughly estimated at: 9 75% of thermosets. The unsaturated polyester share is estimated at 85%, that of epoxies 10%, and the remaining 5% for all the other thermosets. 9 25% of thermoplastics, particularly polypropylene but also polyester and advanced thermoplastics such as polyetherimide, PEEK, etc. The properties of the thermosets are treated in detail in the previous chapters of this book but for the reader's ease we will briefly recall the most interesting characteristics from a matrix viewpoint. 6.4.1 Thermosets Unsaturated polyesters

Unsaturated polyester (UP) is the typical matrix for mass-produced composites with fairly good performances, but it is also used in some hightech composites. Advantages

Interesting price/property ratios; good mechanical and electrical properties; fairly good heat and creep behaviours; aesthetics; resistance to a great number of chemicals; resistance to light, weathering and water in spite of surface deteriorations; possibilities of transparency and food contact for suitable grades; broad range of colours, ease of some manual processing methods; possibility of lightening by controlled foaming; aptitude for the manufacture of very large composite parts (shipbuilding). Drawbacks

Natural flammability (but fire retardant grades); significant shrinkage of the current grades (but low-shrink grades are also marketed); 350

Composites

industrialization and reproducibility difficulties for some processes; limited behaviour to bases, acids and boiling water except for special grades; decomposition by the oxidizing strong acids; attack by some solvents.

Special grades Hand and spray lay-up moulding, impregnation, SMC, BMC, TMC, ZMC, compression, injection, pultrusion, filament winding, centrifugation; long or short glass fibre reinforcement, for thin or thick parts, for shipbuilding, for gelcoat, more or less reactive, more or less thixotropic, food contact, foamed, controlled damping, low shrink, low profile, fire-proofed, preaccelerated, rigid, semi-rigid, flexible, high elongation at break, high transparency, improved light or hydrolysis or heat stability, low emission of styrene or ecological, cold hardening, hot hardening, toughened, light colour, very high transparency, resistance to cracking, etc. For casting, encapsulation, inclusion, cements, concretes; for large blocks, buttons, moulds; vinylester grades for chemical and heat resistance. Examples of uses

Shipbuilding, automobile body elements, building roof sheeting, electrical applications, tanks, cisterns, pipes, industrial applications. Phenolic resins

Phenolic resins (PF) are used in public transport and building, oilrigs and shipbuilding because of their good fire behaviour. Advantages

Fire ratings and relatively low amount of smoke at a relatively low level of toxicity for specific grades; interesting price and price/property ratios; very good heat resistance; high glass transition temperature; good creep behaviour; good mechanical properties; resistance to a great number of chemicals including most common solvents, weak acids, natural oils, fats, greases, petroleum products and automotive fluids; resistance to light and weathering in spite of slight surface deteriorations; usable as matrix for composites. Drawbacks

Opaque, dark colours; unusable for food contact; low arc resistance except special grades; water or ammonia degassing; low resistance to bases except special grades; decomposition by oxidizing strong acids; limited flexibility; low elongation at break. Special grades Compression, injection, impregnation, coating for stratification, preimpregnated, SMC, RTM, pultrusion, filament winding, centrifugation; 351

Thermosets and Composites

alcohol or aqueous solution to penetrate and saturate paper and other similar substrates. Long or short glass fibre reinforced, for thin or thick parts, toughened, exceptional heat resistance, dimensional stability, very low thermal expansion, fire-proofed, UL listed, more or less thixotropic, low shrink... Examples of uses

Fire-proofed elements for building, mass transport, electricity and electronics.

Epoxies Epoxies (EP) are almost exclusively used in high-tech composites in the form of high performance hot-curing grades. The properties depend on the hardener and the curing process. Table 6.2 displays, in round figures, examples of composite properties with identical reinforcement (65 % glass fibre). Table 6.2

Examples

of

epoxy composite p r o p e r t i e s v e r s u s hardener and cure processing Cyclo aliphatic amine

Cyclo aliphatic amine

Acid anhydride

24 h at 23 ~ 2 h at 110 ~

1 h at 80 ~ 1 h at 110 ~

4 h at 80 ~ 6 h at 150 ~

Tensile strength, MPa

- 400

- 400

- 400

Flexural strength, MPa

- 600

- 600

- 650

- 20

- 20

- 20

- 70

- 70

- 90

+

++

++

Electrical properties

+

+

++

Chemical

+

++

++

Hardener Curingprocess

Tensile modulus,

GPa

A g e i n g 7 2 h in w a t e r a t 1 0 0 ~ Flexural strength retention, Thermal

behaviour

properties

%

Advantages

Good mechanical properties; broad range of moduli; good thermal resistance of certain grades; resistance to numerous organic solvents and other chemicals; good electrical properties; aptitude for adherence on a large variety of substrates; good high-energy radiation behaviour; selfextinguishing grades, food contact grades; possibility of transparency; diversity of processing methods, some of which are easy to use, aptitude for the manufacture of high-performance composites. Drawbacks

Often long and energy-expensive production cycles; hygiene prevention during manufacture; relatively high prices justified by the properties; 352

Composites

limited heat resistance for certain grades; risk of chalking during exposure to light.

Special grades They can be classified according to the type of processing, specific properties and targeted applications: 9 For specific processing: impregnation, stratification, filament winding, encapsulation, coating, varnishing, syntactic foams, prepregs 9 Specific properties: transparent, food contact, fire-proofed, flexible, high heat resistance, expansible 9 For specific applications: electronics, tools, repairs... Examples of uses

High performance composites reinforced with glass, Kevlar or carbon fibres; high-pressure tanks; blades of helicopters; empennages of planes; fan blades of wind-tunnels; high-voltage insulators; pipes for hot water and powders.

Polyimides Polyimides (PI) are exclusively used in high-performance composites, especially in the form of prepregs.

Advantages Very good short- and long-term heat stability allowing continuous use up to 260 ~ and peak service up to 480 ~ according to the duration and the grades; good mechanical properties, with limited creep; low coefficient of friction and high abrasion resistance of the friction grades; resistance to numerous organic chemicals; stability of electrical properties according to the temperature; resistance to high-energy radiations; limited vacuum outgassing after moisture elimination. The polyimides are the typical polymers for very high performance applications. Drawbacks

High prices, often long and energy-expensive production cycles, difficulties of processing, and hygiene prevention during manufacture are justified by the high performances. The light behaviour, the arc resistance and the base and acid behaviours can be limited.

Special grades They can be classified according to the type of processing, specific properties, targeted applications: 9 For specific processing: prepregs, filament winding; impregnation, stratification, encapsulation, varnishing 9 Reinforced or modified grades: glass or carbon fibres, glass beads; high, medium or low flow; for crystallization 353

Thermosets and Composites

For specific applications: self-lubricating filled with graphite, graphite and fibres, PTFE etc.; for friction parts; for electronics. Examples of uses

Aeronautics, space, parts of engine, panels, electronics, pinions.

Polycyanates Polycyanates (Cy) are exclusively used in high-performance composites. Advantages

Elevated service temperatures; fatigue behaviour; low outgassing suitable for space hardware; good mechanical properties; fire resistance of suitable grades; good behaviour in wet environment; low-temperature behaviour, low or controlled dielectric constant and loss factor; radiation resistance; reduced microcracking from thermocycling; fair coefficient of thermal expansion; easier processing than polyimides; possibility of RTM and compression moulding. Drawbacks

Unusualness of the product; high-temperature and long cycle processing; price. SpeciaI grades

They can be classified according to the type of processing, specific properties, targeted applications: 9 For specific processing: UD manufacture, prepregs, filament winding, RTM, film adhesives, syntactic foams, syntactic films, two components 9 For specific properties: toughened, super heat-resistant, fire resistant, low dielectric constant, low outgassing, minimal microcracking during thermocycling, low moisture absorption, low shrinkage, lowtemperature curing, electrostatic dissipation, low viscosity, modified tack, epoxy modified. 9 For specific applications: electricity and electronics, aeronautics and space. Examples of uses

Aeronautics, space and electronics. Polyurethanes

Polyurethanes (PUR) are of various natures and their properties vary in a significant way according to the grades. They are very often processed by RRIM or SRIM. Advantages

Broad range of moduli from very flexible to rigid materials; liquid state of suitable grades; ease and diversity of the processing methods; interesting 354

Composites

price/property ratios; fair oil and fuel behaviours; fair or good mechanical and thermal resistances for suitable grades; possibilities of transparency and fire-proofing. Drawbacks

Sensitivity to hydrolysis, acids and bases of the polyester types particularly; sometimes limited resistance to ageing; natural combustibility; limited continuous use temperature for some grades; rather slow processing. Special grades They can be classified according to the type of processing, specific properties, targeted applications: 9 For specific processing: cold or hot castable, RIM, SRIM, flexible or rigid foams, coatings 9 Specific properties: flexible, rigid, fire-proofed, high performances, heat resistant, improved light and hydrolysis stabilities, transparent, chemical resistant, low-temperature uses 9 Specific applications: wear-resistant parts, medical uses, electricity, electronics, adhesives, sealing. Silicones

Silicones and fluorosilicones are sometimes impregnation in the manufacture of composites.

used for glass fibre

Advantages

Very good stability of the properties across a broad range of temperatures; long-term heat stability; low-temperature flexibility for the elastomers; good electrical properties; ease of some manual or semi-automatic processes; light and weathering behaviour; resistance to numerous chemicals especially for the fluorosilicones; water repellence; possibility of transparency; physiological inertia of suitable grades. Drawbacks

Rather high prices justified by the performances; limited mechanical properties; low rigidity of the elastomers; limited resistance to bases and strong acids; poor behaviour with numerous solvents for the silicones; risks of reversion in confined atmosphere or for very thick parts; high permeability to gases; attacked by high-pressure water vapour; high coefficient of expansion for the neat grades; corrosivity of the acid curable grades; industrialization and reproducibility difficulties with certain processes. Special grades

They can be classified according to the type of processing, specific properties, targeted applications: 355

Thermosets and Composites

9 For specific processing: one-part, two-parts, RTV (Room Temperature Vulcanizing), injection resins, LSR for LIM, millable or HVR (High Viscosity Rubber), syntactic or expanded foams, heat curing, fast curing, thixotropic 9 For specific properties: neutral or anti-corrosive, fire-proofed, transparent, good adhesion without primer; resistant to reversion, moisture, chemicals, harsh environment, high and low temperatures, high thermal dissipation, non-curable for special cements 9 For specific applications: thick parts, electricity and electronic, ablative materials. Schematic comparison of thermoset matrix properties

The graphs in Figures 6.2.a and 6.2.b present in a schematic way a classification of the various thermoset matrices according to mechanical and thermal properties. These classifications are subjective and highly debatable.

Figure 6.2.a Thermoset matrices: Examples of mechanical properties

Figure 6.2.b Thermoset matrices: Examples of thermal properties 356

Composites

The choice of the matrix also influences the processing methods, as shown in the examples in Table 6.3. Table 6.3

Suggestions for the choice of processes versus thermoset nature

UP

PF

VE

EP

lay-up

*

*

*

*

Spray lay-up

*

*

*

*

RTM

*

*

*

(*)

*

*

*

*

*

*

*

*

*

*

*

*

(*)

*

*

*

*

Hand

and RIM

Filament

winding

Pultrusion Continuous

stratification

Prepregs 9 Suitable;

PUR

PI

Cy

Si

*

*

*

(*) used rarely

6.4.2 Thermoplastics

It is necessary to distinguish: 9 Short glass fibre reinforcement: the main thermoplastics are proposed in such grades. 9 Mat and continuous glass fibre reinforcements: theoretically all the thermoplastics are usable in these forms, but up to now the developments have concentrated on polypropylenes (PP), polyamides (PA), thermoplastic polyesters (PET); PEEK, polyetherimide (PEI) and polyphenylene sulfide (PPS) are used for high-performance applications. They are presented in a range of forms from stampable sheets to pellets, prepregs, ribbons, impregnated or coated continuous fibre rods. More rarely (as in the case of PA 12, for example), the thermoplastic is provided in liquid form. The thermoplastics can be classified according to their distribution in: 9 Commodities: polyethylene (PE), PP, PVC, polystyrene (PS). 9 Technical thermoplastics: PA, polyacrylic (PMMA), polyacetal (POM), polycarbonate (PC), polyphenylene oxide (PPO) or polyphenylene ether (PPE), thermoplastic polyesters- PET, PBT. Reinforced cellulosics are scarcely used. 9 Specialty thermoplastics: polysulfone (PSU), PPS, fluoroplastics, PEEK, PEI, polyamide imide (PAl), liquid crystal polymers (LCP). suppression of the condensation or reticulation or polymerization step; easier recycling and welding possibilities but these advantages are often disrupted by the reinforcement. The general properties are those of the basic polymer with a high reinforcement effect. A d v a n t a g e s versus thermosets:

357

Thermosets and Composites Drawbacks: reversibility of thermoplasticity for heat applications; lower creep resistance than thermosets; disadvantages of the basic polymer.

Uses

The short glass fibre reinforced grades are used for all sorts of injected parts. The mat and continuous glass fibre reinforced grades have specific uses: 9 Mass production parts: bumpers, soundproofing shields, cross-pieces, inserts for dashboards, seat frames, containers, welding helmets, ventilator housings, base of lawnmowers, taping of pipes, pipelines, tanks, long fibre reinforced injected parts. 9 Technical products with PEEK, PPS, PEI etc. matrix for aeronautics and other high-tech applications. The properties of the main thermoplastics are highlighted below. Polyethylene (PE) Advantages

Low cost; easy to process; chemical inertia; good impact strength; low water absorption; low density; high insulating properties even in wet environment; low coefficient of friction; suitable grades for food contact. Drawbacks

Limited UV resistance; risks of environmental stress cracking; heat and creep sensitivity; low rigidity; high shrinkage, difficult gluing. Cost

Ranges roughly from < g l up to ~2 per kg.

Polypropylene (PP) Advantages

Good mechanical properties at ambient temperature; price; ratio cost/ performances; chemical inertia; low absorption of water; low density; good electrical insulating properties even in wet environment; impact and fatigue behaviour for suitable grades and stresses; special grades for food contact. Drawbacks

Risks of sensitivity to UV; limited impact strength of some grades; lowtemperature and creep behaviour; low rigidity; difficult gluing. Cost

Ranges roughly from < ~1 up to ~2 per kg. Polyvinyl chloride (PVC)

Mechanical properties are very different according to whether the PVC formulation is rigid or plasticized. 358

Composites

Advantages

Rigid PVC: rigidity at ambient temperature; low cost; chemical resistance except some solvents; possible food contact and transparency; naturally fire-retardant; dimensional stability, easy to weld and stick. Flexible PVC: characteristics depend broadly on the formulations; flexibility; improved low-temperature behaviour; fire-retardant grades; low cost; possible food contact and transparency; easy to weld and stick. Drawbacks

Environmental standards, regulations and suspicions handicap the development of the PVCs. Rigid PVC: natural UV sensitivity but special grades benefit from longtime outdoor exposure guarantees; sensitivity to heat, creep, aromatic or chlorinated hydrocarbons, esters and ketones; low-temperature brittleness; high density; toxicity and corrosivity of smoke in fires; less easy injection. Flexible PVC" natural UV sensitivity but special UV-stabilized grades; higher sensitivity to heat, creep and chemicals; high density; higher flammability if plasticizers are flammable; toxicity and corrosivity of smoke in fires. Cost

Ranges roughly from < ~E1 up to 4E2 per kg.

Polystyrene Polystyrene (PS) can be modified, for example: 9 polystyrene acrylonitrile: SAN 9 acrylonitrile butadiene styrene: ABS 9 acrylonitrile styrene acrylate" ASA. Advantages

PS: low cost, transparency, rigidity, impact grades, dimensional stability, food contact grades, insulating properties, easy to weld and stick. SAN: High rigidity, better chemical resistance, glossy surface, scratch resistance. ABS: Better impact and low-temperature behaviours, better chemical resistance similar to SAN. ASA: Better weathering resistance. Drawbacks

PS: Sensitivity to UV, low temperatures, impact (apart from butadiene modified grades), solvents, heat; readily flammable with dripping and dense black smokes; sometimes difficult machining. SAN: like PS but more difficult processing; a little higher cost. 359

Thermosets and Composites

ABS: like SAN but opaque except copolymers; lower chemical resistance; higher cost. Cost

The 9 9 9 9

price ranges are roughly: < ~E1 up to 4E2 per kg for PS ~ 2 up to ~3 per kg for SAN. ~E2 up to 4E4 per kg for ABS. 4E3 up to 4E5 per kg for ASA.

Polyamides Advantages

Good mechanical properties; dynamic fatigue behaviour; tribological properties; low coefficient of friction; good heat and cold behaviours; resistance to numerous chemicals such as usual hydrocarbons, oils, greases, solvents and oil products. PA 6-6 and 6: Good ratio price versus mechanical performances and fatigue resistance; heat and cold behaviours; friction behaviour (coefficient and wear); resistance to oil products and solvents; very high impact strength of special grades. PA 11 and 12: Flexibility; better behaviour at low temperature; less sensitive to water and moisture. Drawbacks

Water sensitivity and swelling; limited weathering resistance needing protection for outdoor use; significant shrinkage; limited fire ratings except special grades. PA 6-6 and 6: Highly hygroscopic. Too dry an atmosphere makes them brittle but an excess of moisture causes swelling, plasticization and a reversible decrease of the mechanical and insulating properties. Saturation swelling can reach 10%. PA 11 and 12: Lower rigidity and heat behaviour. Cost

The costs are roughly: 9 ~E3 UP to ~E5 per kg for PA 6 and 66 9 4E7 up to ~E12 per kg for PA 11 and 12.

Thermoplasticpolyesters The most common are polyethyleneterephthalate (PET) and polybutyleneterephthalate (PBT). Their properties are relatively similar except for the higher crystallinity of PBT. 360

Composites

Advantages

Good mechanical and electrical properties; rigidity; fair creep behaviour; fatigue resistance; low moisture absorption; broad range of continuous use temperature-60 ~ up to 130 ~ UHF transparency. Drawbacks

Sensitivity to water above 60 ~ limited fire behaviour except special grades; limited weathering resistance needing protection for outdoor exposure; medium chemical resistance. Cost

This is roughly of the order of: 9 ~3 up to ~5 per kg for PET 9 ~4 up to ~6 per kg for PBT. Polyacrylics- PMMA Advantages

Transparency; high UV and weathering resistance; gloss and colour stability; fair mechanical properties, rigidity and creep behaviour at ambient temperature; insulating properties notably arc resistance; food contact for suitable grades. Drawbacks

Low impact strength; sensitivity to heat except acrylic-imides; environmental stress cracking; attacked by some common solvents. Cost

The range is roughly: 9 ~2 up to ~5 per kg for PMMA 9 ~4 up to ~6 per kg for acrylic-imides. Polyacetal- POM

The polyacetals are homo- or co-polymers. Advantages

Good ratio cost/mechanical properties; elasticity; fair creep resistance and fatigue behaviour; low moisture uptake; heat and cold behaviours; tribological properties (coefficient and wear); oil and solvent resistance; high impact strength of suitable grades. Drawbacks

High shrinkage due to the high crystallinity; high coefficient of thermal expansion; sensitivity to light; flammability except special grades; opaque, attacked by strong acids, and for certain grades by weak acids and bases; density is a little high. 361

Thermosets and Composites

Cost

The cost is roughly: 9 g3 up to g5 per kg for general-purpose grades 9 g4 up to ~6 per kg for tribological grades. Polycarbonate Advantages

High transparency; high mechanical and insulating properties; natural high impact strength; fair creep and fatigue resistances; low shrinkage and moisture uptake; broad range of service temperatures-100 ~ to +135 ~ food contact and sterilization for suitable grades. Drawbacks

Sensitivity to light, weathering and hydrolysis needing protection for outdoor exposure; flammability except special grades; attacked by bases, oils, chlorinated solvents, ketones; price. Cost

9 roughly ~3 up to ~7 per kg. Polyphenylene oxide (PPO) and polyphenylene ether (PPE)

Almost always used as alloy with polystyrene or polyamide. The latter leads to a better heat resistance. Advantages

Good ratios for cost versus mechanical and electrical properties, and fair creep resistance at room temperature; low moisture absorption, fair heat and cold behaviours; moisture and hot-water resistances; low shrinkage. Drawbacks

Flammability except special grades; attacked by hydrocarbons, oils, chlorinated solvents, strong mineral acids; cost; high friction coefficient. Cost

9 roughly ~4 up to ~7 per kg.

Phenylenepolysulfide The properties of PPS are strongly influenced by the degree of crystallinity, which is optimized with hot processing and after annealing. Advantages

Good mechanical and electrical properties, rigidity, good creep behaviour, fatigue resistance, and broad range of service temperatures-196 ~ up to 200/240 ~ low shrinkage and moisture uptake; good chemical resistance; good fire behaviour. 362

Composites Drawbacks

Sensitivity to notched impact; price. Cost

9 roughly ~5 up to ~10 per kg.

Fluoroplastics The fluoroplastics can be classified into three categories: 9 Perfluoroplastics: PTFE, polytetrafluoroethylene FEP, perfluoropoly (ethylene propylene) PFA, perfluoro-alkoxy 9 Fluorochlorinated: PCTFE, polychlorotrifluoroethylene. 9 Partially fluorinated: ETFE, ethylene-tetrafluoroethylene. PVDF, polyvinylidene fluoride.

Advantages PTFE: Exceptional chemical resistance; high heat and cold behaviour; high heat and wet insulating properties; UV, light and weathering resistances; low coefficient of friction, anti- adherent; flexural dynamic fatigue endurance; high resistance to fire; food contact and medical grades; very low water absorption. PFA: Injection and extrusion grades with the same advantages as PTFE. FEP: Injection and extrusion grades with the same advantages as PTFE but a little lower performance: 200 ~ maximum continuous use temperature instead of 260 ~ PCTFE, ETFE: The same advantages as PTFE but lower performance: 150 ~ maximum continuous use temperature instead of 260 ~ PVDF: Excellent weathering resistance; other advantages similar to PCTFE and ETFE; piezoelectric properties. Drawbacks

All these polymers incorporate high halogen levels that are environmentally harmful. PTFE" Creep and abrasion sensitivity; impossible injection and extrusion by conventional processes; high dimensional variation at glass transition temperature (19 ~ high cost; high density; very difficult to stick; corrosive and toxic smoke generated in fires. PFA: The same drawbacks as PTFE except injection and extrusion possibilities; very high cost. FEP: The same drawbacks as PTFE except injection and extrusion possibilities; very high cost. ETFE, PCTFE, PVDF: The same drawbacks as PTFE except injection and extrusion possibilities; high cost and lower resistance to heat and chemicals. 363

Thermosets and Composites

Cost

The 9 9 9 9 9 9

costs are PTFE: FEP: PFA: ETFE: ECTFE: PVDF:

roughly: ~14upto~20perkg ~30 up to ~50 per kg ~40 up to ~50 per kg ~40upto~45perkg ~50 up to ~80 per kg ~18 up to ~25 per kg.

Polysulfone

Some PSU derivative are also marketed as 9 Polyethersulfone- P E S U - more heat resistant than PSU 9 Polyarylsulfone. Advantages

Good mechanical and electrical properties, fair creep resistance, fatigue behaviour, fair shrinkage; fair moisture uptake; heat and cold behaviours with a broad range of continuous use temperature -100 ~ to +150/180 ~ optical and U H F transparency; food contact and sterilization for suitable grades. Drawbacks

Sensitivity to light needing protection for outdoor exposure; flammability except special grades; attacked by aromatic hydrocarbons, chlorinated solvents, ketones; cost. Cost

The cost are roughly: 9 PSU: ~ 8 up to ~15 per kg 9 PESU: ~10 up to ~20 per kg. Poly,e there the rke tone

Advantages

Good mechanical, chemical and electrical properties; rigidity, good creep resistance, fatigue behaviour, fair moisture uptake, fair shrinkage; heat behaviour with continuous use temperature up to 250 C, high-energy radiation behaviour. O

o

Drawbacks

Sensitivity to light needing protection for outdoor exposure; cost justified by the performances. Cost

9 364

Roughly ~60 up to ~90 per kg.

Composites

Polyetherimide Advantages

Good mechanical and electrical properties, rigidity, fair moisture uptake, fair shrinkage; heat behaviour with continuous use temperatures up to 170/ 180 ~ naturally resistant to UV, light, weathering; naturally fire resistant; optical and U H F transparency; food contact and sterilization for suitable grades. Drawbacks: Sensitivity to some chemicals; cost justified by the performance.

Cost

9 roughly ~13 up to ~14 per kg. Polyamide imide Advantages

Good thermo-mechanical and electrical properties rigidity, impact strength, fatigue endurance; heat behaviour with continuous use temperatures f r o m - 1 9 6 ~ up to +220 ~ tribological properties for suitable grades. Drawbacks

Sometimes difficult processing; high cost justified by the performance. Cost

9 roughly *El5 up to ~25 per kg. Liquid crystal polymers Advantages

Good thermo-mechanical, chemical and electrical properties; rigidity; gamma irradiation resistance; U H F transparency; good creep resistance and fatigue behaviour; low moisture uptake; low shrinkage; heat behaviour; fire resistance; low coefficient of thermal expansion. Drawbacks

Cost justified by the performance; particular mould and part design; density; anisotropy. Cost

9 roughly *El2 up to ~50 per kg. Schematic comparison of thermoplastic matrix properties

Figures 6.3 to 6.6 compare the main mechanical and thermal properties of the main neat thermoplastics. 365

Thermosets and Composites

Figure 6.3. Neat thermoplastic matrices: Examples o f continuous use temperatures at unstressed state

366

Composites

Figure 6.4. Neat thermoplastic matrices: Examples of H D T A (1.8 MPa), ~ 367

Thermosets and Composites

LCP PPS GF/mineral PAI PEEK PEI PET POM PSU PS PVC R I G I D PESU PPO PC PBT P M M A IMPACT PS IMPACI" P O M IMPACT ABS IMPACT PA 66 IMPACT

m

PE-HD

II

PTFE

II

PA 11 or 12 I I PP IMPACT BE PE-LD PVC F L E X I B L E

0

i

l

i

i

i

i

2

4

6

8

10

12

GPa Figure 6.5. Neat thermoplastic matrices: Examples of tensile modulus, GPa

368

Composites

LCP PEI PEEK SAN PSU PA 6 PA 66 PC POM PPS PA 11/12 PET PMMA PPO PVC RIGID PS PVDF ETFE CA ABS IMPACT PCTFE PE-HD PP Co PS IMPACT PVDC PFA PTFE FEP PVC PLASTICIZED PE-LD

m i

0

2'0

4'0

6'0

8'0

100

120

140

160

180

2OO

MPa

Figure 6.6. Neat thermoplastic matrices: Examples of tensile strength, MPa 369

Thermosets and Composites

6.4.3 Influence of the matrix on the composite properties

Table 6.4 displays some examples of properties obtained with various matrices for two types of reinforcements. Table 6.4

Example properties for composites with two reinforcements: matrix effects

30% glass mat reinforced composite with matrix

UP

PP

Density, g/cm 3

1.4

1.14

Tensile strength, MPa

100

90

Tensile modulus, GPa

6

4.5

Continuous use temperature unstressed, ~

145

130

Heat deflection temp. (HDT) A (1.8 MPa), ~

190

150

65% glassfabric reinforced composite with matrix

UP

EP

PI

Density, g/cm 3

1.9

1.9

Tensile strength, MPa

300

400

Tensile modulus, GPa

15

24

Interlaminar shear strength, index

100

160

Cyclic fatigue, maximum stress for 107 cycles, MPa

40

80 to 170

Continuous use temperature unstressed, ~

130

150 to 190

200 to 300

HDT 1.8 MPa, ~

190

Up to 250

300

Price, index

100

150

6.5 Reinforcements The most common reinforcements currently used are: 9 Fibres and sets containing fibres 9 Foams 9 Flat materials: honeycomb, wood, plywood. Nanofillers are also being developed. Examples of specific ISO standards concerning reinforcements

ISO 1043-2:2000 Plastics- Symbols and abbreviated t e r m s - Part 2: Fillers and reinforcing materials ISO 3344:1997 Reinforcement products - Determination of moisture content. 6.5.1 Fibres

Glass fibres are the most commonly used accounting for 95% of the consumption of fibres for plastic reinforcement. Aramid and carbon fibres account for most of the remaining 5 %. 370

Composites

N u m e r o u s other fibres have specific uses: 9 Steel fibres and steel cords 9 Mineral fibres such as boron, quartz and whiskers 9 Natural fibres such as jute, flax and so on 9 Textile fibres such as nylon and polyester 9 Industrial fibres such as PE, P T F E and P B O In hybrid reinforcement, two or m o r e types of fibres are used in the same composite. The graph shown in Figure 6.7 plots the strength versus the modulus of some typical fibres. Note the very special p e r f o r m a n c e of the whiskers.

Figure 6.7. Fibres: Examples of tensile strength versus modulus

The performances of a given fibre and its cost govern its use in composites: 9 Whiskers and boron fibres for very specific composites 9 C a r b o n fibres for advanced composites o A r a m i d fibres for intermediate composites 9 Glass fibres for general-purpose composites o Nylon and other textile fibres for flexible composites 9 Steel fibres for tyres, conveyor belts, E S D c o m p o u n d s 9 P E for antiballistic composites 9 Sustainable fibres for economic and e n v i r o n m e n t a l reasons. The practical goals of the fibre reinforcement are: 9 To increase the modulus and strength 9 To improve the heat deflection t e m p e r a t u r e ( H D T ) 9 To reduce the tendency to creep u n d e r continuous loading 9 To save costs by decreasing the material cost used to obtain the same stiffening. The main difficulties are" 9 The risk of shortened length of the fibres broken during the processing. 371

Thermosets and Composites

Anisotropy due to fibre orientation and settling. With some processes, this is an advantage: the right placement of the fibres permits reinforcement at specific points in the right direction. Cost savings by fibre reinforcement

To cut raw material costs without any change in the stiffness or strength, it is possible to reduce the wall thickness by using a reinforced grade of the same matrix. Figure 6.8 plots the reinforcement ratios for short glass fibre reinforced polyamide (PA-GF) versus neat polyamide for six important characteristics calculated versus density and material cost. These characteristics are tensile strength, tensile and flexural modulus, impact strength, H D T A and B. For example, the flexural modulus (FMw) is computed versus density (d) as below: FMwPA_GF = FMpA_GF/dpA_GF f o r P A - G F

and FMwp A - F M p A / d p A for neat PA The reinforcement ratio for performance/weight - (FMwPA_GF)/FMwp A Except for the H D T B (reinforcement ratio - 1), all the other reinforcement ratios are greater than 1, up to nearly 4 for the modulus. To replace a PA with a wall thickness of 2 mm, it is possible to use a PAGF of wall thickness: 1.43 mm for the same tensile strength and save 14% of the weight and 11% of the material cost. 0.7 mm for the same modulus and save more than 50% of the weight and the material cost.

Figure 6.8. Fibres:Examples of reinforcement ratios for short glass fibre reinforced PA6

372

Composites

Examples of specific ISO standards concerning the fibre reinforcement

ISO 1889:1997 Reinforcement yarns - Determination of linear density ISO 1890:1997 Reinforcement y a r n s - Determination of twist ISO 2113:1996 Reinforcement fibres - Woven f a b r i c s - Basis for a specification ISO 2113:1996/Cor 1:2003 ISO 3344:1997 Reinforcement products- Determination of moisture content ISO 4602:1997 R e i n f o r c e m e n t s - Woven f a b r i c s - Determination of number of yarns per unit length of warp and weft ISO 10122:1995 Reinforcement materials - Tubular braided sleeves - Basis for a specification ISO 10371:1993 Reinforcement m a t e r i a l s - Braided t a p e s - Basis for a specification ISO 15100:2000 P l a s t i c s - Reinforcement f i b r e s - Chopped strands Determination of bulk density 6.5.1.1. Glass fibres for polymer reinforcement

The glass fibres are made from glass spun in the melt state. They are then assembled and protected by sizing with organic or silane materials. They exist in various grades: 9 E-glass: the general-purpose grade that represents more than 90% of the reinforcement fibres 9 R - or S-glass with high mechanical performances, good fatigue resistance, high thermal and moisture behaviours. The principal applications relate to aeronautics, space, sports, leisure, armament, and antiballistic ,, D-glass with high dielectric properties, transparent to electromagnetic waves. The principal applications relate to the manufacture of radomes, electromagnetic windows and high-tech printed circuit boards 9 C - and ECR-glass with enhanced acid resistance 9 AR-glass, alkali resistant, particularly intended for the reinforcement of concrete. Table 6.5 displays the average compositions and main features concerning the glass fibres used in polymer reinforcement. All the glass fibres have in common: 9 High thermal resistance 9 Insulating properties, with unfortunate consequences on the electrostatic discharge 9 Elastic modulus in the range 50-90 GPa, much higher than the polymer but lower than carbon fibres 9 Low coefficient of thermal expansion 9 High density 9 Brittleness under high stresses during processing 9 Abrasive properties harmful for tools. 373

Thermosets and Composites Table 6.5 Average composition and main property examples of the three main types of glass fibres used in polymer reinforcement

E-glass

R-glass

D-glass

High performance~cost ratio

High mechanical performance

Low dielectric loss

Silica

53 to 57

58 to 60

72 to 75

Alumina

12 to 15

23 to 26

Calcium and magnesium oxides

22 to 26

14 to 17

Analysis examples, %

Boron oxide

5 to 8

Up to 23

Others

Applications

Market share of the reinforcementfibres

General-purpose

Aeronautics & space Sports & leisure Antiballistic

Radome EM windows Printed circuit boards

90

<10

<10

Table 6.6 displays examples of the mechanical and physical properties of the three most important glass fibre types. Glass fibres are used in various forms for the reinforcement of polymers: 9 Chopped or milled glass fibres: 0.1 to 20 mm length, 5 to 25 microns in diameter, aspect ratio from 4 to 4000. These fibres are dispersed into the polymers. 9 Yarns: a defined number of filaments are brought together with a slight twist. 9 Plied yarns: a defined number of yarns are brought together with a slight twist. . Texturized and voluminized products: an air stream leads to the formation of loops in overfed continuous filament and imparts bulk. 9 Rovings" a large number of filaments are brought together. 9 Mats: chopped fibres (50 mm) are held together with a binder soluble in styrene to form a sheet. 9 Continuous filament mats: sheet of continuous filament felt with a binder soluble in styrene. 9 Stratipregs or prepregs: roving impregnated with a resin, often an epoxy. 9 2D reinforcing products: mats, woven or knitted fabrics, braidings from yarns or rovings. 9 3D reinforcing structures. Glass fibres are generally chosen for: 9 The versatility of the sizing that leads to good compatibility with all polymers. 9 The high specific mechanical performances. 374

Composites Table 6.6

Typical mechanical and physical properties of various glass fibres

E-glass

R-glass

D-glass

2.6

2.5

2.14

Moisture absorption, %

<0.1

<0.1

<0.1

Tensile strength of virgin fibres, MPa

3500

4400

2500

2000 to 2600

3500

1650

Tensile modulus, G P a

70

85

55

Elongation at break, %

4

4.8

4.5

Density, g/cm 3

Tensile strength of impregnated fibres, MPa

Poisson's ratio

0.18

Thermal properties % residual tensile strength after 24 h at 200 ~

98

100

% residual tensile strength after 24 h at 300 ~

82

91

% residual tensile strength after 24 h at 400 ~

65

77

% residual tensile strength after 24 h at 600 ~

0

Coefficient of thermal expansion, 10-S/K Thermal conductivity, W / m K Specific heat, cal/g. ~

0.5

0.4

0.35

1

1

0.8

0.19

kJ/(kg.K)

0.8

Dielectricproperties Resistivity, ohm.cm

1012 to 1015

Dielectric constant @ 1 M H z

6.5

6

3.8

Permittivity @ 1 MHz, 10 -4

15

19

5

Dielectric strength, kV/mm

10 to 100

9

The dimensional stability due to the coefficient of thermal expansion and the low water absorption. 9 The low cost of the raw material. 9 The cost saving possibilities at constant performances. 9 The insulating properties. 9 The incombustibility of a mineral material. 9 The chemical resistance of the glass. 9 The insensitivity to putrefaction. 9 The thermal conductivity. Nevertheless, their use in polymers produces some constraints because of: 9 The lack of surface conductivity for electrostatic discharge. 9 The need to employ wear-resistant materials for the equipment parts exposed to the reinforced polymer. 375

Thermosets and Composites

The special design of the equipment and parts to eliminate or reduce settling of the fibres and abrasion wear. Examples of the characteristics of some reinforced glass fibre plastics

9

Reinforcement with chopped glass fibres dispersed in the polymer matrix. The properties depend on: o The fibre content o The aspect ratio (length versus diameter) e The sizing of the fibres to enhance the adhesion to the matrix o The real length of the fibres in the final part o The quality of the fibre dispersion o The anisotropy in the final part. 9 Reinforcement with continuous filaments, rovings, fabrics and so on. The properties depend on: o The fibre content o The form of the glass fibre reinforcement (filament, roving...) e The orientation of the glass fibres o The adhesion of the fibres to the matrix o The anisotropy in the final part. Table 6.7 shows some examples of the modulus and the strength reinforcement ratios for various reinforced thermoplastics and thermosets. The reinforcement ratio is the performance of the reinforced polymer divided by the performance of the neat polymer. Table 6.7 Examples of reinforcement ratios based on tensile strength and modulus of various reinforced polymers

Polyamide

Polycarbonate

Unsaturated polyester

Glassfibre

Strength

Modulus

None

1

1

Dispersed short GF

2.2

5

Dispersed long GF

3.3

6.7

None

1

1

Dispersed short GF

2.1

3.3

None

1

1

BMC

3.4

3.7

SMC

6

3.7

Fabric reinforcement

5

4.6

Unidirectional reinforcement

20

23

Effect of short glass fibre on material cost

The addition of short glass fibres has two effects: 9 The cost of the raw material is: 376

Composites

o Increased for the cheapest polymers o Decreased for the most expensive ones. 9 The blending induces a roughly constant supplementary cost. In the end, the cost can be: 9 Increased by 35% for PET 9 Decreased by 35% for an LCP. Figure 6.9 shows examples of cost ratios [costs of short glass fibre reinforced thermoplastics/costs of the neat thermoplastics] versus costs of the neat grades.

Figure 6.9. Ratios [Costs of short glass fibre reinforced thermoplastics~neat thermoplastics] versus costs of the neat grades

Examples of specific ISO standards concerning glass fibre reinforcement ISO 1172:1996 Textile-glass-reinforced p l a s t i c s - Prepregs, moulding compounds and l a m i n a t e s - Determination of the textile-glass and mineral-filler c o n t e n t - Calcination methods ISO 1268:1974 P l a s t i c s - Preparation of glass fibre reinforced, resin bonded, low-pressure laminated plates or panels for test purposes ISO 1887:1995 Textile glass- Determination of combustible-matter content ISO 1888:1996 Textile glass- Staple fibres or filaments- Determination of average diameter ISO 2078:1993 Textile g l a s s - Y a r n s - Designation ISO 2558:1974 Textile glass chopped-strand mats for reinforcement of plastics - Determination of time of dissolution of the binder in styrene ISO 2559:2000 Textile g l a s s - Mats (made from chopped or continuous strands) - Designation and basis for specifications ISO 2797:1986 Textile g l a s s - R o v i n g s - Basis for a specification 377

Thermosets and Composites

ISO 3341:2000 Textile glass - Yarns - Determination of breaking force and breaking elongation ISO 3342:1995 Textile glass - Mats - Determination of tensile breaking force ISO 3343:1984 Textile glass- Y a r n s - Determination of twist balance index ISO 3374:2000 Reinforcement products - Mats and fabrics Determination of mass per unit area ISO 3375:1975 Textile glass - Determination of stiffness of rovings ISO 3597-1:1993 Textile-glass-reinforced p l a s t i c s - Determination of mechanical properties on rods made of roving-reinforced r e s i n - Part 1: General considerations and preparation of rods ISO 3597-2:1993 Textile-glass-reinforced p l a s t i c s - Determination of mechanical properties on rods made of roving-reinforced r e s i n - Part 2: Determination of flexural strength ISO 3597-3:1993 Textile-glass-reinforced p l a s t i c s - Determination of mechanical properties on rods made of roving-reinforced resin - Part 3: Determination of compressive strength ISO 3597-4:1993 Textile-glass-reinforced p l a s t i c s - Determination of mechanical properties on rods made of roving-reinforced r e s i n - Part 4: Determination of apparent interlaminar shear strength ISO 3598:1986 Textile g l a s s - Yarns - Basis for a specification ISO 3616:2001 Textile g l a s s - Chopped-strand and continuous-filament m a t s - Determination of average thickness, thickness under load and recovery after compression ISO 4603:1993 Textile glass - Woven fabrics - Determination of thickness ISO 4604:1978 Textile glass - Woven fabrics - Determination of conventional flexural stiffness- Fixed angle flexometer method ISO 4606:1995 Textile glass - Woven f a b r i c - Determination of tensile breaking force and elongation at break by the strip method ISO 4900:1990 Textile g l a s s - Mats and f a b r i c s - Determination of contact mouldability ISO 5025:1997 Reinforcement products - Woven fabrics - Determination of width and length ISO 8516:1987 Textile glass - Textured yarns - Basis for a specification ISO 9163:1996 Textile glass- R o v i n g s - Manufacture of test specimens and determination of tensile strength of impregnated rovings ISO 9353:1991 Glass-reinforced p l a s t i c s - Preparation of plates with unidirectional reinforcements by bag moulding. Trade name examples

The trade names are numerous and only a selection are quoted here: Araton, Assemblofil, Beta, Chopvantage, Creel-Pak, D-Glass, Fiberglas, G-Glass, Glasslon, Maxichop, Microlith, Miraflex, Q-Fiber, Silenka, Silione, Tufrov, Vetrotex, Vitron. 378

Composites

6.5.1.2. Carbon fibres (CF) for polymer reinforcement

The production of carbon fibres is based on the pyrolysis of organic fibres or precursors. The main starting materials are polyacrylonitrile (PAN) and pitch (coal tar or petroleum asphalt). They can be classified according to their mechanical performances: 9

High tenacity

9

High modulus

9

High modulus and improved tenacity.

Or according to their applications, for example: 9

General purpose

9

Aeronautics

9

Aeronautics and high modulus.

According to the process and the grades, the characteristics fluctuate as we can see in Table 6.8. Table 6.8

Examples properties of various carbon fibres

PAN carbonfibres

High tenacity

Density, g/cm 3

1.8

1.7 to 2

1.7 to 1.8

Tensile strength, MPa

High modulus; improved tenacity Mechanical properties

High modulus

3500 to 6400

3400 to 4700

2700 to 5500

Elasticity modulus, G P a

230 to 300

340 to 640

290 to 390

Elongation at break, %

1.5 to 2.2

0.5 to 1.4

0.7 to 1.9

-0.038 to -0.056

-0.073 to -0.11

-0.06 to -0.1

8 to 33

38 to 167

21 to 113

0.18 to 0.19

0.17

0.17 to 0.18

Thermalproperties Coefficient of thermal expansion, 10-5/K Thermal conductivity, W/m.K

Specific heat, cal/g. ~

Electricalproperties Resistivity, ohm.cm

1.4 to 1.7"10 -3

Pitch carbonfibres

Generalpurpose Aeronautics Mechanical properties

0.7 to 1.1"10 -3

0.7 to 1.2"10 -3 Aeronautics & high modulus

Density, g/cm 3

2.12 to 2.15

2.12 to 2.15

2.16 to 2.20

Tensile strength, MPa

2600 to 2900

3600 to 3700

3700 to 3800

640 to 790

620 to 790

790 to 900

0.4

0.5 to 0.6

0.4 to 0.5

140 to 220

220 to 260

5 to 7"10-6

2 to 4"10-6

Elasticity modulus, G P a Elongation at break, %

Thermalproperties Thermal conductivity, W/m.K

140 to 220

Electricalproperties Resistivity, ohm.cm

5 to 7"10 -6

379

Thermosets and Composites

Intended for high-performance applications because of their cost, carbon fibres have excellent mechanical properties but are sensitive to impact and abrasion. They are used for their interesting characteristics, such as: 9 High tensile strength 9 High modulus 9 High creep resistance 9 High fatigue resistance 9 High dielectric conductivity 9 High thermal conductivity 9 Lower density than glass fibre 9 Low coefficient of friction 9 Low coefficient of thermal expansion. On the other hand, their drawbacks are" 9 Low impact strength 9 Low abrasion resistance 9 High cost. Carbon fibres are used in various forms for polymer reinforcement: 9 Short fibres dispersed in the matrix 9 Yarns, rovings, stratipregs or prepregs, mats, 2D and 3D reinforcing structures. As for glass fibres, reinforcement with continuous fibres leads to the highest performances. Compared to short glass fibres, short carbon fibres yield higher reinforcement ratios for the modulus and tensile strength but the impact strength decreases. Table 6.9 shows examples of: 9 The modulus and the strength reinforcement ratios for various carbon fibre reinforced thermoplastics and thermosets. The reinforcement ratio is the performance of the reinforced polymer divided by the performance of the neat polymer. 9 Enhancement ratios of carbon fibres versus glass fibres. The data used here are the ratios of a property for a carbon fibre reinforced composite (CFRP) versus the same property for the glass fibre reinforced composite (GFRP). Examples of specific ISO standards concerning carbon fibre reinforcement

ISO 10119:2002 Carbon f i b r e ISO 10548:2002 Carbon f i b r e ISO 10618:1999 Carbon fibre resin-impregnated yarn ISO 11566:1996 Carbon f i b r e single-filament specimens 380

Determination of density Determination of size content - Determination of tensile properties of Determination of the tensile properties of

Composites

Table 6.9

Examples of reinforcement ratios of CFRP and enhancement ratios versus GFRP

Reinforcement ratios based on tensilestrength and modulus of various carbon fibre reinforcedpolymers

PEEK

PPS

Epoxy

Carbon fibre

Strength

Modulus

None

1

1

30% dispersed short CF

2.3

4.4

40% dispersed short CF

2.7

5.4

None

1

1

40% dispersed short CF

2.4

6.5

None

1

1

SMC

3.9

23

Unidirectional reinforcement

20

70

Enhancement ratios obtained with short carbonfibre instead of glassfibre in a thermoplastic matrix Property CF composite~property GF composite Modulus

1.5 to 2.7

Tensile strength

1.2 to 2.1

Impact strength

0.7 to 0.9

Creep modulus

3.8 to 6.7

Creep stress

1.6 to 1.7

Fatigue resistance (10 6 cycles)

1.2

ISO 11567"1995 Carbon fibre - Determination of filament diameter and cross-sectional area ISO 13002:1998 Carbon fibre - Designation system for filament yarns Trade name examples

Selected carbon fibre trade names are: Besfight, Dialead, Filkar, Fortafil, Grafil, Granoc, Panox, Pyrofil, Pyron, Tenax, Thornel, Torayca 6.5. 1.3. Aramid fibres (Air) for polymer reinforcement

The most widespread and widely known are Kevlar and Twaron. AF are used especially in high and medium performance applications; they are also used with other fibres to make hybrid reinforcement. Table 6.10 shows examples of properties of Kevlar 29 and 49. Aramid fibres have high specific mechanical properties and are used for their interesting characteristics such as: 9 High tensile strength, particularly specific strength (engineering strength versus density) 381

Thermosets and Composites

Table 6.10

Example properties of various aramid fibres

Mechanical properties

Density, g/cm 3 Moisture level, % Tensile strength, MPa

Kevlar 29

Kevlar 49

1.44

1.44

4.5 to 7

3.5

2900

3000

Elasticity modulus, GPa

70

112

Elongation at break, %

3.6

2.4

Poisson's ratio

0.36

Thermal properties Continuous use temperature unstressed, ~

150 to 177

150 to 177

Coefficient thermal expansion, 10-5 K

-0.4

-0.5

Thermal conductivity, W/m.K

0.04

0.04

0.34

0.34

1013 to 1015

1013 to 1015

Specific heat, cal/g. ~

Electricalproperties Resistivity, ohm.cm

9 High modulus 9 High creep resistance 9 High fatigue resistance 9 Lower cost than carbon fibre 9 Lower density than glass and carbon fibres . Low coefficient of friction 9 Low coefficient of thermal expansion. On the other hand, their drawbacks are: 9 Higher cost than glass fibre 9 Moisture uptake 9 Sensitivity to U V and weathering 9 More limited thermal properties than glass and carbon fibres o High electrical resistance and a lack of surface conductivity for electrostatic discharge 9 More limited compression and flexural strengths 9 Difficult machining. A r a m i d fibres in various forms are used for polymer reinforcement: 9 Short fibres dispersed in the matrix 9 Yarns, rovings, stratipregs or prepregs, mats, 2D and 3D reinforcing structures. Short aramid fibres lead to intermediate reinforcement b e t w e e n those obtained with glass and carbon fibres. 382

Composites

As for the other fibres, reinforcement with continuous aramid fibres leads to the highest performances. Table 6.11 shows the enhancement ratios for aramid fibres versus glass fibres used in the same composite type. The enhancement ratios are the ratios of a property for an aramid fibre reinforced composite versus the same property for the glass fibre reinforced composite. Table 6.11 Examples of enhancement ratios obtained with incorporation of aramid fibres instead of glass fibres in a composite

Property AF composite/property GF composite Short aramid fibres instead of short glassfibres in a thermoplastic matrix Modulus

1.2

Tensile strength

1.1

Specific modulus

1.3

Specific tensile strength

1.2

Continuous aramid fibre instead of continuous glassfibre in a thermoset matrix Modulus

2

Tensile strength

1.04

Specific modulus

2.9

Specific tensile strength

1.4

Trade name examples The most well-known trade names are Kevlar and Twaron. 6.5.1.4. Comparison of the three main types of fibres

In all cases, carbon fibres lead to the highest mechanical performances compared to glass and aramid fibres. Nevertheless, their impact behaviour and price cut down their consumption. Glass fibres yield the cheapest composites but performances are more limited. Table 6.12 shows some examples of properties for epoxy U D and nylon matrix reinforced with short fibres of the three types. Table 6.12

Characteristic comparison examples of the three main fibres

Fibreproperties

E glass

Aramid

Carbon

2.6

1.44

1.7 to 2

Tensile strength, MPa

2000 to 3500

2900 to 3000

2000 to 6400

Tensile modulus, GPa

70 to 73

70 to 130

200 to 590

Strength/density

770 to 1350

2000 to 2080

1000 to 3760

Modulus/density

28

48 to 90

100 to 300

3 to 5

2 to 4

0.5 to 2

1012 to 1015

5"1015

10 -3

Density, g/cm 3

Elongation at break, % Resistivity

383

Thermosets and Composites Table 6.12

Characteristic comparison examples of the three main fibres

Epoxy UD compositeproperties Density, g/cm 3 Tensile strength, MPa

E glass

Aramid

Carbon

1.9

1.37

1.56

1400

1450

1400

Tensile modulus, GPa

42

87

130

Strength/density

750

1050

900

Modulus/density

22

63

83

Compression strength rating*

2

3

1

Flexural strength rating*

2

3

1

Impact strength rating*

2

1

3

Interlaminar shear strength rating*

1

3

2

Shear strength in a plane rating*

1

2

1

Tensile fatigue rating*

3

2

1

Cost rating

1

2

3

E glass

Aramid

Carbon

Density, g/cm 3

Shortfibre reinforcedpolyamide

1.29

1.19

1.23

Tensile strength, MPa

100

95

207

Tensile modulus, GPa

5.3

5.1

13

Elongation at break, %

5

6

Notched impact, arbitrary units

10

6

250

222

3

2

HDT A (1.8 MPa), ~ Coefficient thermal expansion, 10-5/K

250

* 1 = best rating; 3 = worst

Figure 6.10 shows schematically the relative positions (modulus versus strength) of some composites according to the nature and form of the fibres. These are examples with different reinforcement contents and forms and the comparison is not really representative of all the possibilities.

Figure 6.10. Glass, aramid, carbon fibre reinforced composites: Tensile modulus versus tensile strength examples 384

Composites

6.5.1.5. Sustainable natural vegetal fibres

Natural reinforcements have been used for a very long time: 9 Wood flour was one of the first fillers used with phenolic resin. 9 Wood shavings are used in wood particleboards. 9 Short cotton and other cellulosic fibres are commonly used in phenolic and melamine resins. There is a renewed interest in natural fibres as sustainable materials to replace industrial glass fibres in general purpose composites. Several reasons promote these ideas: 9 Environmental and ecological criteria 9 Economic considerations that lead some nations to give priority to local materials 9 Increasing plastic consumption that needs increasing quantities of glass fibres. Generally, compared to glass fibres, natural vegetal fibres offer advantages but also drawbacks, for example: 9 The outputs are sometimes a little weak, which limits development studies and industrialization. 9 Price is often attractive but there are exceptions and the performances/ price ratios are rarely favourable. 9 Density is always attractive. 9 Mechanical properties are lower but fair (see Table 6.13). 9 Recycling is theoretically easier. 9 Long-term effects of temperature, moisture and light are unfavourable. 9 Cost savings up to 60% are claimed when performances are not essential. Table 6.13 shows the properties of some sustainable fibres compared to glass fibres. Table 6.13

Properties of some sustainable fibres compared to glass fibres

Fibres

Glass

Flax

Price, % of GF price

100

Output, % of GF output

100

Density, g/cm 3

2.6

Tensile strength, MPa

3000

Jute

Sisal

130

20

20

20

70

280

40

10

1.5

1.3

1.5

1.2

350 to 1000 400 to 800

Coconut Ramie

500 to 600

175

400 to 900

Modulus, GPa

70

28

27

9 to 22

5

60 to 130

Elongation at break, %

2.5

3

2

2

30

4

Tensile strength/density

1150

230 to 670

300 to 600

300 to 400

150

270 to 600

Modulus/density

27

20

20

6 to 15

4

40 to 90

Tensile strength/price, % versus glass

100

10 to 25

70 to 130

80 to 100

30

Modulus/price, % versus glass

100

30

190

60 to 150

40 385

Thermosets and Composites

Other fibres claimed as usable are: 9 Cereal, corn, barley.., into matrices of PP, PE, ABS, PVC. Composite moduli are claimed in the range of 1.5 to 3 GPa for prices in the order of ,E0.75 to ,E3 per kg. Applications could be in packaging, toys, building and automobile. The properties of the polypropylene composites "Epitex" are, for example" o Density: 0.94 to 0.97 g/cm 3 o Flexural strength: 40 to 46 MPa o Flexural modulus: 2 to 2.6 GPa o Charpy impact strength: 9 to 40 kJ/m 2 9 Kenaf (hibiscus cannabinus) is used by Ford, Saab, Volvo for some interior trims. 9 A flax nonwoven is used by Opel, Renault, Citroen for interior trims. . Modified cotton wastes are patented by Impact Composite Technology to absorb styrene during unsaturated polyester processing. . Arboform, a composite of lignin, hemp and flax developed by the Fraunhofer Institute, is proposed to replace more traditional materials in the automotive industry. 9 The E A C Technologies Cy produces mats of flax, hemp or jute and composites made of flax or hemp or jute reinforced polypropylene. 9 Fasal or Fasalex are completely biodegradable materials of vegetal origin. Some properties are shown below: 1.2 to 1.4 o Density, g/cm 3 17 to 25 o Tensile strength, MPa 4to8 o Tensile modulus, GPa: 30 to 50 o Flexural strength, MPa: 4to6 o Flexural modulus, GPa: 0.5 to 1 o Elongation at break, %" o Charpy impact strength, k J / m 2 : 3 to 7 Possible applications are: o Interior architectural products such as floors, ceilings, walls... o Furniture such as skirting, doors, cladding, panels... o Technical profiles such as cable channels, supporting poles, fixing elements, vehicle components. Examples of industrial applications of natural reinforcements: 9 Scooter bodies, letterboxes made from unsaturated polyester reinforced with coconut, banana, and jute fibres in India. 9 SMC and BMC from unsaturated polyester and jute or sisal or palm fibres in the USA. 9 Interior automotive panels. 9 Truck parts from rubbers, polyurethanes and thermoplastics reinforced with coconut, jute, banana or cotton. 9 Building products: decking, fencing, siding and decorative trims. 386

Composites

9 9

Infrastructure: boardwalks, marinas and guardrails. Industrial and consumer applications: pallets, playground equipments, benches... The US natural fibre and wood composite market was estimated at 340 000 tons in 2001 rising to just over 450 000 tons in 2003, that is to say, roughly 1% of the total plastic consumption. Europe is not such an important market as the USA because of the lack of available wood by-products and the lack of end-uses. 6.5.1.6. Other mineral fibres

Other mineral fibres are used for very specific applications. Boron fibres and boron~carbon fibre hybrids

Boron fibres were used for specific aeronautic composites, for example in the wings of the F 14 by Grumman, for their structural properties. Now, because of their high cost, they are often replaced by carbon fibres. Boron fibres have high performances: 9 Thermal resistance 9 High modulus 9 High compression strength. They are generally used in the form of prepregs 70-fibres/30-matrix of epoxy, polyimide or phenolic resin. The boron/carbon fibre hybrids, Hy-Bor, are sometimes used in sports goods for their ability to provide thinner laminates and save weight for the same stiffness. Mineral fibres such as silica, quartz, ceramics

These fibres are used for their thermal properties combined with high mechanical performances. Unfortunately their price is prohibitive and applications are reduced to, for example, rocket motors. Stainless steel fibres

Stainless steel fibres are used for two main reasons: 9 Obtaining electrical conductivity. Short fibres are added to thermoplastics to obtain EMI, ESD or conductive grades. In certain composites, long or continuous fibres partially replace glass fibres. 9 Structural properties for flexible composites such as tyres, belts, etc. Whiskers

Whiskers are single-crystal fibres. They are very expensive and difficult to produce with only a few specific applications, for example, submicronic gears or connectors. 6.5.1.7. Other textile fibres

Other textile fibres - polyester, rayon, polyamide - have low moduli (see Table 6.14), which limits their plastic reinforcing power. They are used 387

Thermosets and Composites

particularly for the reinforcement of rubbers and soft plastics such as plasticized PVC. Brittle glass fibres would be broken under the high shear of rubber processing. Thermoplastic polyester fibres are also used in certain BMC where they lead to higher impact strength and abrasion resistance than glass fibres. The polyester non-woven materials are also used as surface veil. Table 6.14 compares various fibres with glass fibres. Table 6.14

Example properties of various fibres

Density

Tensilestrength

Modulus

Elongationat break

Melt temperature

g/crrfl

MPa

GPa

%

~

Nylon

1.16

1000

5.6

18

254

Polyester

1.38

1200

14

14

256

Glass

2.6

3000

70

2.5 to 5

750

Highly stretched PE

0.97

2600

120

4

149

Steel

7.7

2000

203

2

1500

6.5. 1.8. Industrial fibres Polyethylene fibres

Polyethylene fibres are handicapped by their low melting temperature. They are used for antiballistic products. PTFE fibres

PTFE fibres are used for tribological composites. PBO fibres

They are used for their temperature resistance and fire behaviour. 6.5.2 The different fibre forms used for reinforcement

During manufacturing, the filaments are sized with organic materials. Later in the process it may be necessary to desize. The spun filaments are assembled in strands, yarns, rovings that can be woven or knitted. One distinguishes: 9 Chopped or milled fibres: 0.1 to 20 mm length, 5 to 25 microns in diameter, aspect ratio from 4 to 4000. These fibres are dispersed into the polymers. 9 Strands: an assembly of filaments. 9 Yarns: a defined number of filaments are brought together with a slight Z or S-twist. 9 Plied yarns: a defined number of yarns are brought together with a slight twist. 9 Cabled yarns: a defined number of plied yarns are brought together with a slight twist. 388

Composites

9

Texturized and voluminized products: an air stream leads to the formation of loops in overfed continuous filament and imparts bulk. 9 Rovings: a large n u m b e r of filaments are brought together. 9 Mats: chopped fibres (50 m m ) are held together with a binder soluble in styrene to form a sheet. 9 Continuous filament mats: sheets of felt of continuous filaments with a binder soluble in styrene. 9 Stratipregs or prepregs: Rovings i m p r e g n a t e d with a resin, often an epoxy. These fibre products can be: 9 Woven: with a few differences, the technology is similar to textile weaving. 9 Braided to produce tubular sleeves. The obtained products are, for example: 9 2D reinforcing products: mats, woven or knitted fabrics, braidings from yarns or rovings. 9 3D reinforcing structures. 9 Fabrics. These are characterized by: o The weave pattern or crossing scheme of the warp (lengthwise) and weft (perpendicular to the warp) yarns. o The count or n u m b e r per centimetre of warp and weft yarns. o The yarn types. Influence of the reinforcement form on the composite properties

As the reinforcements have the structural role, their form is essential. Let us r e m e m b e r that: 9 For an example of U D continuous carbon fibre reinforcement, the tensile strength is 1760 MPa in the fibre direction and 80 M P a in the perpendicular direction. 9 The reinforcement obtained with a given level of a given type of fibres is a function of the length, the aspect ratio and the orientation of the fibres. 9 Unless otherwise specified, the mechanical properties are indicated for the favourable fibre direction but the engineering properties really depend on the stress direction. Table 6.15 displays the strength and modulus of a 60% glass fibre reinforced resin for various fibre forms. The properties are roughly: 9 Strength: 80 to 9 0 0 - a range of m o r e than 150% of the average value. 9 Modulus: 8 to 30 G P a - a range of more than 100% of the average value. Table 6.15

Mat

Example properties of a 60% glass fibre reinforced resin for different fibre forms

Strength, MPa

Modulus, GPa

200

15 389

Thermosets and Composites

Table 6.15

Example properties of a 60% glass fibre reinforced resin for different fibre forms

Balanced fabric

200 to 400

20

UD fabric, fibre direction

700 to 800

30

80

8

800 to 900

30

80

8

U D fabric, perpendicular direction U D roving, fibre direction U D roving, perpendicular direction

6.5.3 Foams for sandwich technology In a sandwich structure, the foam is used as the core with two skins of reinforced resin sheets firmly stuck on the foam to obtain high rigidity. The sandwich composite behaves as an I-beam: see Figure 6.11.

Figure 6.11. Schematic principle of a sandwich composite with foamed core

Sandwich composites are used in: General-purpose applications such as railway and road transport; body elements for isothermal or refrigerated vehicles; sports and leisure (skiing, cycling, hockey); nautical structural components; thermal and phonic insulation panels in building... 9 High-tech applications such as aeronautics, blades of wind turbines, competition sports, racing motorboats, shipbuilding... The core and the final parts can have any shape: parallelepipedic for a lot of sandwich panels, shaped parts for the hulls of boats or bumpers and so on. These lightweight composites have a superior stiffness/mass ratio with excellent thermal and phonic insulating properties. Foams can be flexible or rigid, with open or closed cells, reinforced or not. Their properties depend on: 9 The chemical nature of the polymer 9 The manufacturing process 9 The density 9

390

Composites

9 The cell morphology: open or closed, diameter, wall thickness, etc. The foams can be classified into four categories: 9 General-purpose foams: PVC, polyurethane, polystyrene. 9 For technical applications: Polyethylene, polypropylene, methacrylimide. 9 Specialty foams: polyetherimide, polysulfone. 9 Syntactic foams. The following information concerns foams for sandwich technology only and not foams used for packaging or insulation. Rigid PVC foams

PVC foams used as sandwich cores generally have: 9 Densities in the range of 30-700 kg/m 3 9 Closed cells 9 Crosslinked or linear structures. Often, the crosslinking improves the mechanical properties and chemical resistance, leading to a more rigid but perhaps more fragile sandwich composite than linear foam. The water or moisture permeability and absorption are low and the hydrolysis resistance is generally good. PVC is naturally fire resistant and an adequate formulation can improve its behaviour. However, the high chlorine level in PVC is released in the event of combustion and can involve corrosion during the processing, and the thermal behaviour is limited. Table 6.16 shows some examples of PVC foam properties. Table 6.16

Example properties of PVC foams Linear PVC foams

Density

kg/m3

60

90

140

Compression strength

MPa

0.380

0.900

1.600

Compression modulus

GPa

0.030

0.056

0.135

Tensile strength

MPa

0.900

1.400

2.400

Tensile modulus

GPa

0.030

0.050

0.090

W/m. ~

0.034

0.037

0.039

kg/m3

30

100

400

Maximum service temperature

~

70 to 80

70 to 80

70 to 80

Minimum service temperature

~

-200*

-200*

-200*

Compression strength

MPa

0.220

1.700

11.240

Compression modulus

GPa

0.012

0.125

0.500

Thermal conductivity

Crosslinked PVC foams Density

391

Thermosets and Composites Table 6.16

Example properties of PVC foams

Crosslinked PVC foams Density

kg/rrfl

30

1O0

400

Tensile strength

MPa

0.510

3.100

12.400

Tensile modulus

GPa

0.020

0.105

0.469

W/m. ~

0.03

0.04

0.06

%

0.1

0.06

0.02

Thermal conductivity Water absorption, 7 days, 40 ~ Poisson's ratio Coefficient of thermal expansion

0.32 10-5/~

4

3.5

2.2

* except mechanical stresses because the embrittlement occurs at higher temperatures

Examples of applications: 9 Sandwich panels: body structures of refrigerated lorries and similar vehicles; roofs of coaches; structural components; containers for maritime, road, railway and air transport; wagons to carry and store food onboard aircraft; shelters, bodies of military light machines. 9 Nautical structural components: hulls, decks, superstructures and partitions of motorboats; vessels for fishing or racing. 9 Structural and interior components for aeronautic, automotive and railway equipment: floors, radomes, bodies of buses and coaches (Neoplan), front end components, drivers' cabs, partition walls, luggage racks in high-speed trains. Polyurethane foams

Polyurethane foams can be flexible or rigid polyesters or polyethers. Compared to polyethers, polyester foams generally present: 9 Better mechanical resistance 9 Better capacity for soundproofing and damping 9 More limited resistance to ageing 9 Better behaviour with hydrocarbons 9 Greater sensitivity to water and hydrolysis. Table 6.17 shows some examples of polyurethane foam properties. Examples of applications: 9 Sandwich panels for containers or bodies of isothermal trucks (rigid foams), panels for frigorific rooms. o Cores for polyester boats, sailboards. 9 Walls of prefabricated dwellings. 9 Self-supporting panels. 9 Seats made of sandwich composite with foamed core and thermoplastic skins. 392

Composites Table 6.17

Example properties for polyurethane foams

Type

Soft

Density, kg/m 3

Semi-rigid

Rigid

20 to 30

30 to 70

10% compression stress, MPa

0.14 to 0.6

40% compression stress, MPa Tensile strength, MPa

0.02 to 0.07 0.100 to 0.160

0.14 to 0.18

200 to 300

35 to 60

Elongation at break, % Thermal conductivity, W/(m.K)

9 9

0.022 to 0.035

Soundproofing screens with foamed core and thermoplastic skins. Insulated doors or double doors for buildings, dwellings or offices.

Polystyrene foams

Generally, the properties of the polystyrene foams used for sandwich technology are: 9 Low densities, usually from 10-50 kg/m 3 9 Damping, thermal and acoustic insulating properties 9 Low permeability to water vapour, limited water absorption, good hydrolysis behaviour 9 Sometimes low mechanical properties depending on the processing method. 9 Limited or weak resistance to solvents and hydrocarbons, which limits the use with unsaturated polyesters 9 Naturally low fire resistance that can be improved by an adequate formulation. Table 6.18 shows some examples of polystyrene foam properties. Examples of applications: 9 Insulating panels for refrigerated warehouses and other cold storage. 9 Structural insulating panels. 9 Sea sailboards or surfboards with laminate skins of glass fibre reinforced unsaturated polyester or epoxy resins. 9 External panels of houses or buildings with laminate skins of glass fibre reinforced unsaturated polyester. Table 6.18 Example properties for polystyrene foams 10% compression stress

MPa

0.06 to 0.7

Compression strength for long-term service

MPa

0.015 to 0.45

Thermal conductivity

W/m. ~

0.027 to 0.038

Water absorption, 28 days

%

0.1 to 3 393

Thermosets and Composites

Decorating beams for the interior of houses with laminate skins of glass fibre reinforced unsaturated polyester. Polyethylene foams

Generally, the properties of polyethylene foams for sandwich technology are: Densities from 25-330 kg/m 3 Semi-rigid to flexible Closed cells Crosslinked or linear structure. Often, the crosslinking improves the mechanical properties and chemical resistance. Polyethylene foams have: 9 Suitable mechanical characteristics 9 Insulating and damping properties 9 Low permeability to water vapour, limited water absorption, good hydrolysis behaviour 9 A naturally low fire resistance that can be improved by an adequate formulation. Table 6.19 shows some examples of the properties of polyethylene foam. Examples of applications: 9 Panels and sandwich structures for protection of oil wellheads. 9 Multi-layer composites for damping, sometimes in combination with polypropylene foam. Some helmets, for example, are made of thermoplastic skins and a core of one layer of PE foam with a second layer of polypropylene foam. Table 6.19

Example properties for polyethylene foams

Density

kg/m 3

25 to 185

Thermal conductivity

W/m.K

0.034 to 0.067

10% compression stress

MPa

0.012 to 0.160

50% compression stress

MPa

0.080 to 0.33

Compression set, 22 h, 25 %

%

Tensile strength

MPa

Elongation at break

%

80 to 425

Water absorption, 7 days

%

< 1 to <2.5

Service temperatures

~

-80 to 100

2 to 13 0.140 to 3.9

Polypropylene foams

The typical properties of polypropylene foams for sandwich technology are" 9 Densities from 23-70 kg/m 3 394

Composites

9 9

Closed cells Crosslinked or linear. As with PE and PVC foams, the crosslinking often improves the mechanical properties and chemical resistance. Polypropylene foams have: 9 Suitable mechanical characteristics 9 Good resistance to multi-cycle impacts 9 Insulating and damping properties 9 Low permeability to water vapour, limited water absorption, good hydrolysis behaviour 9 A naturally weak fire resistance that can be improved by an adequate formulation. Table 6.20 shows some examples of polypropylene foam properties. The major application is in the damping cores of car bumpers. An interesting development originating from Neste and Norsk Hydro is a multi-layer coating for the insulation of high deep-water pipelines. The steel pipe is protected with a layer of solid thermoplastic, a core of polypropylene foam and a coating of solid plastic. All the layers are built up by cross head extrusion. Table 6.20

Example properties for polypropylene foams

Density

kg/m 3

Service temperatures

~

23 to 70 -40 ( o r - 8 0 ) to +120

10% compression stress

MPa

0.02 to 0.07

50% compression stress

MPa

0.11 to 0.56

Compression set, 22 h, 25 %

%

Tensile strength

MPa

0.2 to 1.2

Elongation at break

%

15 to 400

Thermal conductivity

W/m.K

Water absorption, 7 days

%

6 to 11

0.034 to 0.042 1 to 2.5

Styrene-acrylonitrile foam: "Core-Ceil" by A TC Chemicals

This rigid linear foam with closed cells was developed by A T C Chemicals Company to be used as the core in lightweight structural sandwich composites particularly intended for boatbuilding. SAN foams have: 9 Linear structure 9 Properties close to those for toughened crosslinked PVC 9 Better thermal stability than PVC 9 Thermoformability. Some property examples are: 9 Density: 58 to 210 kg/m 3 395

Thermosets and Composites

9 Compression modulus" 0.042 to 0.420 GPa 9 Compression strength: 0.6 to 4.3 MPa 9 Tensile modulus: 0.045 to 0.340 GPa 9 Tensile strength: 0.9 to 4.2 MPa 9 Thermal conductivity: 0.032 to 0.046 W/m.K. Application examples in boatbuilding: hulls, engine stringers, bulkheads, decks and superstructures. Polymethacrylimide: "Rohacell"by R~hm This rigid foam with closed cells was developed by the R6hm Company of the Htils group to be used as the core in lightweight structural sandwich composites particularly used in transport applications. Polymethacrylimide foams have: 9 A density range of 30-300 kg/m 3 9 Excellent mechanical properties with a high thermal stability 9 Good resistance to solvents used for the composites processing 9 Low thermal conductivity 9 High damping properties to impact 9 Low oxygen index, 19 to 20, which limits the fire resistance 9 A low X-ray absorption. Table 6.21 shows some examples of the properties of polymethacrylimide foam. Application examples: 9 Aeronautics: parts of Airbus, ATR, Eurocopter, Dassault, McDouglas Donnell; radomes 9 Car parts: Matra and Volvo. 9 Railway: two-stage version of the TGV; front-end of the Italian Pendolino 9 Medical: radiography tables (low X-ray absorption) 9 Naval: sports boats, yachts, catamarans, racing motorboats 9 Sports: parts for skis, rackets (Head, Dynastar, Atomic), wheels and frameworks of racing bikes. Table 6.21

Example properties for polymethacrylimide foams

Density

kg/m3

32

75

110

190

Compression strength

MPa

0.4

1.5

3

3.2 to 7.8

Tensile strength

MPa

1

2.8

3.5

8.5

Elastic modulus

GPa

0.036

0.092

0.160

0.380

Elongation at break

%

3.5

4.5

4.5

6 12 to 12.5

Flexural strength

MPa

Thermal conductivity

W/m.K

Dimensional stability

~

396

0.8

2.5

4.5

0.031

0.030

0.032

180

180

180

130

Composites Polyetherimide: "Airex R82" by Airex

This low-density foam with closed cells is associated with: 9 A high impact strength 9 Broad range of service temperatures:-194 ~ to 180 ~ 9 Good fire resistance 9 High thermal behaviour 9 Low water absorption 9 Attractive dielectric properties. Table 6.22 shows some examples of polyetherimide foam properties. Application examples: 9 Aeronautics: equipment for planes, radomes and communication systems 9 Automotive and transport" structures for railway and road vehicles 9 Industry: structures in temperature, cryogenic applications. Table 6.22

Examples of properties of polyetherimide foam

Density

kg/m 3

80

Compression strength (about 6 %)

MPa

0.950

Compression modulus

GPa

0.054

Flexural strength

MPa

1.8

Flexural modulus

GPa

0.052

Service temperature

~

Thermal conductivity

W/m. ~

-194 to +180 0.025

Polyethersulfone foams

The low-density specific foam named "Airex R80.90", specially developed by Airex, has: 9 Good fire resistance 9 High thermal behaviour 9 Transparency to radar frequencies. The "Ultratect foam" from B A S F is used as the core with glass fibre reinforced polypropylene skins for the sandwich rear seat backrest of the M3 CSL sports car by BMW. The weight saving is 50% versus a metal part. Table 6.23 shows some examples of polyethersulfone foam properties. The major application markets of this foam are sandwich structures for: 9 Aeronautics and aerospace 9 Transmissions and telecommunications (transparency to radar frequencies). 397

Thermosets and Composites Table 6.23

Examples of properties of polyethersulfone foams

Density

kg/m 3

90

Compression strength

MPa

0.790

Compression modulus

GPa

0.025

Flexural strength

MPa

1.5

Flexural modulus

GPa

0.045

Thermal conductivity

W/m. ~

0.039

Syntactic foams Syntactic foams are obtained by mixing hollow micro- or macro-balloons, generally made of glass but sometimes of polymer, directly with a resin of unsaturated polyester, vinylester, phenolic, epoxy, polyimide, polycyanate, polyurethane or silicone. Some extend this definition to all the composites with a foamed core. The viscosity of the resin must be low enough that the balloons remain unbroken during the mixing process. The exothermic peak of hardening should not involve the degradation of the matrix or the formation of internal stresses and microscopic cracks. If their manufacturing is conducted properly, the foams are isotropic, have good impermeability and attractive compression properties for a relatively low density. Table 6.24 gives examples of the properties of high performance syntactic foam with epoxy resin. Application examples include: 9 Insulation of pipes, pipelines and other offshore equipment. These foams have the ability to withstand usage at ocean depths of 3000 m and beyond for 30 years. 9 Buoyancy elements. 9 Cores of structure sandwiches with composite skins. 9 Electronic equipment for microwave and RF applications. Syntactic foams act as structural, dielectric and heat barrier materials. Table 6.24

Some typical properties of high performance syntactic foams

Density

kg/m 3

500

600

Uniaxial compression strength

MPa

44

90

Hydrostatic compression strength

MPa

60

120

Compression modulus

GPa

2

3

Flexural strength

MPa

28

38

Thermal conductivity

W/re. ~

0.12

0.13

398

Composites

Honeycombs Honeycombs are structures with hexagonal or cylindrical cells made from thin sheets of aluminium, aramid (Nomex), paper or extruded polypropylene. The dimensions of the cells are generally in the range of 5 mm to 10 mm. The two faces are covered with a firmly adherent composite (or sometimes metal) skin. Figure 6.12. shows an example of a sandwich panel made from an extruded polypropylene honeycomb core (from Tubulam, Bagneux, France). The density is low, 80 kg/m 3 or 140 kg/m 3 for example, with attractive mechanical properties but the skin adherence on the honeycomb section is delicate. Generally, the sandwich composites combine light weight, good flexural stiffness and good stress distribution without weak points. Tensile and compression properties, particularly punching, can be weak. 6.5.4

Figure 6.12. Example of sandwich panel made from an extruded polypropylene honeycomb core

Aramid honeycombs The aramid honeycombs, for example Nomex, generally have: , Fair impact behaviour except punching ,, Good electrical insulating properties 9 High ratio of flexural strength/weight 399

Thermosets and Composites

9 9 9 9

High cost Low lateral strength High moisture absorption needing a good waterproofing Limited tensile and compression strengths.

Aluminium honeycombs Aluminium honeycombs generally have: 9 Relatively attractive cost 9 High ratio of flexural strength/weight 9 Good damping properties 9 Electrical conductivity 9 Surface finish difficult to obtain 9 Limited tensile and compression strengths 9 Sensitivity to corrosion needing special anticorrosion treatments. The obtained composites can be used as structural elements in: 9 Aircraft and space industry: o Floors of planes; wall, ceiling and flooring panels; soundproofing panels. o Vertical stabilizers, blades of helicopters, radomes... o Satellite solar panels, satellite antenna reflectors, careenages for Atlantique2, helicopter rotor blades, ATR72 jib cowls... o Storage bins. 9 Automobile and transport: o Bus, tram, intercity train, cable car, caravan bodies. 9 Buildings and furniture" o Frontages of Heathrow airport o Lightweight structural floors o One-off range of furniture for an exceptional hotel room (Brochier room). 9 Shipbuilding" o Bulkheads, partitions, watertight bulkheads o Mega yachts 40 m length. 6.5.5 Plywood and wood

Wood based composites often use balsa, which has: 9 Relatively low density: 100 kg/m 3 and more 9 Attractive cost 9 Fair mechanical properties: o Compressive strength 5 to 20 MPa in grain direction 0.6 to 1.4 MPa in transverse direction o Compressive modulus 2 to 8 GPa in grain direction 0.1 to 0.4 GPa in transverse direction 400

Composites

o Flexural strength 6 to 17 MPa in grain direction 9 Good impact behaviour. 9 Fair thermal, acoustic and electrical insulation 9 Sensitivity to water and moisture needing a good waterproofing. Plywood is the cheapest wood-based material and offers: 9 Good mechanical properties 9 Good impact behaviour 9 Good ratio of mechanical properties/cost 9 Sensitivity to water and moisture needing a good waterproofing 9 Relatively high density. The composites obtained can be used in: 9 Shipbuilding: floor panels, decks, bulkheads, partitions, watertight bulkheads, fishing boats... 9 Road and railway transport: floors of refrigerated trailers or semitrailers, refrigerated vans, containers, etc. 6.5.6 Influence o f the core on

the sandwich properties

For 15 mm thick panels with glass fibre reinforced unsaturated polyester skins, the weights are roughly: 9 3 kg/m 2 for a 80 kg/m 3 honeycomb or foam. 9 4 kg/m 2 for a 140 kg/m 3 honeycomb or foam. 9 5 kg/m 2 for a balsa core. 9 8 kg/m 2 for a plywood core. Figures 6.13 and 6.14 compare sandwiches with a 13 mm core thickness and glass fibre reinforced unsaturated polyester skins.

Figure 6.13. Sandwich structure examples: Flexural strength versus density 401

Thermosets and Composites

4 ~g o

E -1,1

2

Density 0

I

I

I

I

I

I

I

I

I

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Figure 6.14. Sandwich structure examples: Flexural modulus versus density

6.5.7 Nanofillers

Nanofillers (see Figure 6.15) are made up of: 9 Elementary particles in platelet form with thickness of the order of a nanometre and diameter of the order of 100 nm. 9 Primary particles made by stacking several elementary particles. The thickness is about 10 nm. 9 Aggregates of numerous elementary particles. Figure 6.15 shows the schematic structure of nanofillers. To exceed the usual reinforcement offered by a filler and obtain a real nanocomposite it is necessary to destroy the primary particle structure: 9 Either completely, by dispersing the elementary particles into the macromolecules, giving a delaminated nanocomposite. 9 Or partially, by intercalating macromolecules between the elementary particles, giving an intercalated nanocomposite.

I

() () () ()

I

I

Elementary particles Figure 6.15. Schematic structure of nanofillers 402

Primary particles

I

Composites

Figure 6.16 shows the schematic structure of nanocomposites.

Delaminated nanocomposite

Intercalated nanocomposite

Figure 6.16. Schematic structures of nanocomposites

The most popular nanofiller is the natural layered silicate montmorillonite, which is subjected to specific treatments. The properties of the final nanocomposite depend on the nanocomposite treatments and the mixing efficiency. Table 6.25 displays examples of polyamide nanocomposite properties according to the processing method. Practically all polymers can be processed to make nanocomposites: 9 Thermoplastics: some polyamide and TPO nanocomposites are used in the automotive industry and there are experiments with saturated polyesters, acrylics, polystyrenes... 9 Thermosets: studies have been carried out on epoxides, unsaturated polyesters, polyurethanes... 9 Elastomers: studies on nitriles... The nanosilicates because of their high aspect ratio, high surface area and nanometric scale provide reinforcement at low levels of incorporation. Table 6.25 Property examples for polyamide nanocomposites processed by various methods Neat PA

PA nanocomposite Property

Reinforcementratios

Tensile modulus

GPa

2.7

3.3 to 4.3

1.2 to 1.6

Tensile strength at yield

MPa

64

69 to 85

1.1 to 1.3

Elongation at break

%

40

8 to 60

Not available

Izod notched impact

J/m

37

36 to 50

i to 1.3 403

Thermosets and Composites

The main nanocomposite properties are" 9 Mechanical performances between those of the neat polymer and short glass fibre reinforced grades 9 Higher H D T than neat polymer but lower than short glass fibre reinforced grades 9 Density much lower than conventional reinforced grades 9 Lower gas permeability 9 Better fire behaviour. Taking an industrial example (see Table 6.26), the reinforcement r a t i o s that is, the ratio of the nanocomposite performance versus that of the neat p o l y m e r - obtained with a nanosilicate level as low as 2% are noteworthy. For a very similar density, the nanocomposite has significantly better thermo-mechanical properties than the neat polyamide, as Table 6.26 shows. Table 6.26 Property examples of a 2% nanosilicate filled polyamide Property examples

Reinforcementratios

Density

g/cm 3

1.15

1

Tensile strength

MPa

100

1.25

Flexural modulus

GPa

3.9

1.3

H D T A (1.8 MPa)

~

140

1.9

6.6 Intermediate semi-manufactured materials Some materials are moulded or shaped with semi-manufactured products: the matrix and the reinforcement are already assembled before processing, for example: 9 SMC, bulk moulding compounds, prepregs for thermoset composites 9 GMT, prepregs for thermoplastic composites. 6.6.1 SMC, bulk compounds, prepregs

The SMC and BMC processes are the main processes used for composites, with a share in the total composite consumption estimated at about 40%. These processes are appreciated because of: 9 The ability for mass production 9 Design freedom 9 Ready-to-mould form 9 Formulation versatility: fire resistant grades, customizing to meet customer specifications 9 Bulk colouring that removes the need for painting 9 The possibility of class "A" aspect 9 Large part sizes . Final costs (up to 50% cost savings in comparison to cast aluminium). 404

Composites

For chopped fibre reinforcements, the properties depend on: 9 Fibre nature 9 Fibre level 9 Aspect ratio (length versus diameter) 9 The treatment of the fibres to enhance the adhesion to the matrix 9 Real length of the fibres in the final part 9 Quality of the dispersion of the fibres 9 Anisotropy in the final part. For the reinforcement with continuous filaments, rovings, fabrics and so on, the properties depend on: 9 Fibre nature 9 The form of the fibres (filament, roving...) 9 Fibre level 9 Orientation of the fibres 9 The adhesion of the fibres to the matrix 9 Anisotropy in the final part.

SheetMoulding Compound(SMC) Chopped glass fibres are impregnated with a stabilized uncured thermoset resin and shaped into a sheet protected on the two faces by plastic films that are removed before moulding. SMCs, compression moulded at high temperature, are convenient for the manufacture of all types of very diverse and complex parts. They have good mechanical properties, which are 2D isotropic. The continuous fibre reinforced grades are anisotropic but are tougher in the fibre direction. SMC cures after shaping by heating under pressure. The shelf life is limited in time and temperature because of the slow hardening of the resin. Figure 6.17 illustrates the principle of SMC manufacture.

Figure 6.17. Schematicmanufacturing of SMC 405

Thermosets and Composites

SMC with very high glass fibre levels are called H M C (High Modulus Compound) because of their superior properties. The general-purpose grade shrinkage is in a range from 0.2 % to 0.5 % but lower shrinkage grades are also marketed: 9 Low-shrink grades with 0.05% to 0.2% shrinkage 9 Low-profile or "zero shrink" grades with less than 0.05 % shrinkage. The most used resins are unsaturated polyesters but vinylester, phenolic or epoxy resins can also be used. The properties depend on the formulation and, particularly, on the reinforcement level and morphology. With a given level of glass fibres, the reinforcing effect and the creep behaviour: 9 Increase with the aspect ratio 9 Increase with the fibre length. With a given glass fibre morphology, the reinforcing effect and the creep behaviour: 9 Increase with the fibre level. Figures 6.18, 6.19 and 6.20 show the effect of glass fibre level on flexural strength, flexural modulus and impact resistance, for a given fibre morphology.

Figure 6.18. Example of the effect of glass fibre level on flexural modulus

In 9 9 9 9 406

Europe, SMC usage is: 40% in transport 40% in electricity & electronics 15% in building 5% in miscellaneous applications.

Composites

Figure 6.19. Example of the effect of glass fibre level on flexural strength

Figure 6.20. Example of the effect of glass fibre level on impact strength

Bulk Moulding Compounds- BMC and variants The bulk moulding compounds (BMC) are a puttylike mass of: 9

U n c u r e d matrix resin, stabilized and often filled with inert filler

9

C h o p p e d fibres or rovings as reinforcements

9

Typically 10% to 30% glass fibre levels

9

Glass fibre lengths in the range of 6 to 12 mm.

They are m a n u f a c t u r e d by continuous process or by batches in mixers. They are delivered in bulk or as sheets similar to SMC. The shelf life is limited in time and t e m p e r a t u r e because of the slow hardening of the resin. B M C cures after shaping by heating u n d e r pressure. 407

Thermosets and Composites

Premix or DMC- Dough Moulding Compound

D M C is a pasty mass of stabilized uncured and filled thermoset resin with chopped fibres or roving as reinforcements. The mechanical properties are lower than those of SMCs and prepregs. For example, after hot compression moulding, the same resin with the same glass level has tensile strengths of roughly: 9 35 MPa for a D M C 9 80 MPa for a SMC. B M C is a D M C containing a thickener that increases viscosity and improves the mould feeding. A M C - Alkyd Moulding C o m p o u n d - is a BMC in which the styrene is replaced by a diallylphthalate. T M C - Thick Moulding C o m p o u n d - is a B M C delivered in thick sheets. C I C - C o n t i n u o u s Impregnated C o m p o u n d - i s a continuous manufactured compound delivered in bulk. Z M C is a highly automated process patented by Saint Gobain. All the process stages are concerned: material, press, mould, finishing line. In Europe, BMCs are used: 9 43% in transport 9 42% in electricity & electronics 9 10% in buildings 9 5% in miscellaneous applications.

Prepregs Reinforcements in all shapes, such as fabrics, rovings, ribbons etc (made of aramid, glass or carbon fibres), are impregnated with uncured epoxy, unsaturated polyester or polyimide resins. The resin levels can be of the order of 30% up to 80%. In the most usual technology, the reinforcements: 9 Are impregnated by immersion in a bath of resin solution 9 Pass between rollers to squeeze out the excess resin 9 Are dried by evaporating the solvent in an oven to reach an intermediate stage of hardening (state B) 9 Are cooled and rolled up with a protection film so that they cannot adhere to themselves. In another impregnation technique, the reinforcement is assembled with a resin film and hot pressed. The prepregs cure after shaping by heating under pressure. Shelf life is limited in time and temperature because of the slow hardening of the resin. 4O8

Composites

Prepregs are generally used in advanced applications: aeronautics, space, electronics, sports, special automotive parts. They are also sometimes used in filament winding. 6.6.2 Glass mat thermoplastics (GMTs) and prepregs

GMTs are thermoplastic resin sheets or blanks reinforced with glass mat. Possibly, unidirectional continuous fibres can also be used. The blanks of this consolidated material can be shaped in steel tools by heating under pressure to a semi-molten state. The matrix is generally polypropylene (in more than 95 % of GMTs) or more rarely thermoplastic polyester. The parts have good mechanical properties but the creep behaviour is not as good as for thermoset composites. High-performance GMTs are being developed with matrices such as polyethersulfone, polyetherimide, polyamide-imide, PPS, PEEK. Two manufacturing processes, dry and wet, are in competition leading to some significantly different properties, particularly for the impact resistance. Dry process: A mat covered above and below by melted polymer is compacted by heating under pressure. Wet process: discontinuous fibres (of shorter length than in the dry process) and thermoplastic powder are mixed and suspended in water. They are bound in a sheet form before being dried and compacted. Because of the thermoplastic matrix, the shelf life is unlimited at room temperature. The graphs in Figures 6.21 and 6.22 display two examples of polypropylene GMT and two examples of thermoplastic polyester GMT. In each case note the differences between the impact resistances.

Figure 6.21. Polypropylene GMT examples: Thermal and mechanical property examples 409

Thermosets and Composites

Figure 6.22. Polyester GMT examples: Thermal and mechanical property examples

Prepregs Reinforcements of all forms (made of aramid, glass or carbon fibres) can be impregnated with thermoplastic resins to give prepregs. There are numerous variations for this technology, for example: 9 Twintex R PP is a roving composed of commingled E-glass and polypropylene filaments. It is suitable for filament winding and pultrusion. Consolidation is achieved by heating (180 ~ to 230 ~ under pressure. 9 Twintex T PP is a fabric woven with commingled E-glass and polypropylenerovings.Itissuitableforpressuremoulding.Consolidation is accomplished by heating (180 ~ to 230 ~ under pressure. 9 Twintex G PP is based on commingled E-glass and polypropylene rovings. Delivered in pellets, it is suitable for injection or extrusioncompression. Consolidation is again achieved by heating (180 ~ to 230 ~ under pressure. 9 Towflex is based on carbon, glass or aramid fibres impregnated with polypropylene, polyamide, PPS, polyetherimide, PEEK. Product forms include flexible Towpreg, woven fabric, braided sleeving, UD tape, chopped compression moulding compound, moulded plates, thermoformable laminates. 9 Tepex is delivered as sheets of 0.25 to 3 mm thickness based on carbon, glass or aramid fibres impregnated with polyamide or thermoplastic polyester. Fibre levels range from 35 % up to 85 %. 9 SUPreM: consolidated tapes or fabrics are made from continuous fibres impregnated with thermoplastic powder. The fibres can be glass, aramid, carbon, steel and the matrices are polyethylene, polyamide, PPS, polyetherimide, PEEK, thermoplastic polyimide, or fluorothermoplastic. High levels of fibres can be obtained, 65% in volume, for example. 410

Composites

9 9

Fulcrum is a unidirectional prepreg with fibre levels up to 70% in volume. "EMS hybrid yarns" or "Schappe preimpregnated yarns" are a combination of reinforcing fibres (glass, aramid or carbon) and polyamide 12. Because of the thermoplastic matrix, the shelf life is unlimited at room temperature but one must be careful of the creep tendency. 6.6.3 Examples of intermediate semi-manufactured composites

Table 6.27 and Figure 6.23 display some property examples for various thermoset and thermoplastic composites. These are examples, some other figures exist and the classification is arbitrary but, as already noted, the mechanical performances at room temperature are especially influenced by the nature, form and size of the reinforcements.

Table 6.27 Property examples for various intermediate semi-manufactured thermoset and thermoplastic composites Intermediate semi-manufactured thermoset composites

Neat resin Fibre, nature

BMC

SMC

UD

Glass

Glass

Carbon

Fibres, %

0

30 to 35

30

75

Tensile strength, MPa

50

40 to 70

140 to 240

1500 to 2500

Tensile modulus, G P a

5

10 to 17

14 to 28

30

Flexural modulus, G P a

4

10 to 14

14 to 21

25

Impact strength, index

1

40

Intermediate semi-manufactured thermoplastic composites

Shortfibres

LFR T

GMT

UD

% of glass

30

50

40

60 to 70

Tensile strength, MPa

42

165

100 to 250

350 to 450

Tensile modulus, G P a

4

10 to 11

5 to 8

15 to 75

11

6 to 10

3

5 to 10

Flexural modulus, G P a

Impact strength, index

1.1

General-purpose thermoplasticprepregs Pellets

Balancedfabric

Roving

% of glass

20 to 40

60

60 to 75

Tensile strength, MPa

85 to 120

350

700 to 800

Tensile modulus, G P a

5 to 9

15

28 to 38

Flexural strength, M P a

135 to 200

280

470 to 600

Flexural modulus, G P a

4 to 8

13

24 to 32 411

Thermosets and Composites Table 6.27 Property examples for various intermediate semi-manufactured thermoset and thermoplastic composites

Advancedfibre reinforcedthermoplasticprepregs Matrix

Fibres, nature Fibres, %

PEEK

PEEK

PA

Glass

Carbon

Carbon

Carbon

55 to 75

40

65

Tensile strength, MPa

980 to 1100

1570

2600

800 to 2800

Tensile modulus, G P a

43

78

150

63 to 245

Flexural strength, MPa

1100 to 1340

2000

Flexural modulus, GPa

44

120

Figure 6.23. Examples o f various intermediate semi-manufactured composites: Modulus versus strength

6.6.4 Advanced all-polymer prepregs or self-reinforced polymers

This new solution to recycling problems uses the same polymer for the matrix and the reinforcement. The first industrial development is C U R V by BP, a highly-stretched polypropylene fibre reinforced polypropylene delivered in sheets of 0.3 to 3 mm thickness. In addition to the polypropylene properties and the ease of thermoplastic processing, these materials have: 9 High mechanical performances including the impact strength . A low density 9 Suitability for recycling because of the absence of glass fibre 9 An attractive cost, 494 to 494.5 per kg. 412

Composites

Table 6.28 compares some self-reinforced polypropylene properties with those of other general-purpose solutions. The [property/density] ratios show that the self-reinforced polypropylene is comparable to the general-purpose GMTs with a much higher impact resistance ratio. The [property/volume cost] ratios show that the self-reinforced polypropylene has a much higher impact resistance ratio than general purpose GMTs and glass fibre reinforced thermoplastics but a slightly lower modulus ratio. Table 6.28 solutions

Examples of self-reinforced polypropylene properties compared to other general-purpose

Self-reinforced polypropylene

Neat polypropylene

GMT

Density

0.92

0.9

1.19

Tensile strength, MPa

180

27

70 to 100

Tensile modulus, GPa

5

1.1

4 to 6

4750

200

670

7500

brittle

brittle

Self-reinforced PP

GMT

Short GF reinforced PA

Tensile strength/density

195

60 to 84

100

Tensile modulus/density

5.4

4 to 5

5.5

5160

500 to 600

100 to 120

Self-reinforced PP

GMT

Short GF reinforced PA

Tensile strength/volume cost

40

20 to 40

30

Tensile modulus/volume cost

1.1

1 to 2

1.7

1050

100 to 300

20 to 40

Notched Izod impact D256 at 20 ~ Notched Izod impact D256 at -40 ~

J/m J/m

Examples of[property~density] ratios

Notched Izod impact D256/density

Examples of[property~volume cost] ratios

Notched Izod impact D256/volume cost

Other self-reinforced polymers are being developed. For example, P U R E is based on highly oriented co-extruded tapes of polypropylene and a consolidation binder. According to the f o r m - sheets, tapes or fabricsthe moduli are as high as 8 GPa or more. 6.7 Composite Processing The manufacturing processes differ according to whether the matrix is a thermoset or a thermoplastic. For thermosets: 413

Thermosets and Composites

9

It is necessary to heat for a sufficient time after shaping to crosslink the thermoset so that it solidifies, and gains cohesion and good final properties. 9 The irreversible formation of a three-dimensional network during hardening makes the thermosets unavailable for thermoforming, and welding. Extrusion is sometimes used for special thermosets such as silicones. For thermoplastics: 9 It is necessary to heat only during the shaping time to temporarily decrease the viscosity. By cooling, the thermoplastic composites recover their solid state and mechanical properties. 9 All the processing methods are used including extrusion, thermoforming and subsequently welding. Some of the following processes concerning thermoset composites are also examined in Chapter 5. 6.7.1 Thermoset composites There are numerous process methods with various alternatives. We propose one possible classification for the main processes: 9 Contact moulding: o Hand lay-up in open mould o Spray lay-up in open mould o Hand or spray lay-up in mould closed with a bag, either vacuum or pressure assisted o Compression moulding in closed two-part mould after hand or spray lay-up. 9 Transfer of liquid resin" o Casting and putting with chopped glass filled resin o RRIM, S R R I M o Infusion processes with one-part mould and a bag o RTM" resin transfer moulding with two-part mould, possibly vacuum assisted. 9 High pressure moulding o Compression moulding, cold or hot o Compression/transfer o Injection. . Prepreg draping 9 Filament winding 9 Centrifugal moulding 9 Continuous processes: o Pultrusion o Pullwinding, overbraiding o Continuous sheet moulding. 414

Composites

Hand lay-up onto open mould

Still in use today, this is the oldest process. It requires little investment, is entirely manual and is suitable for small series. The technique (Figure 6.24) consists in manually arranging reinforcements and resin deposits in successive layers onto a negative or positive mould: 9

Gelcoat: a layer of resin directly applied onto the mould intended to give a beautiful appearance, the surface colour and ensuring protection against ageing, chemical and mechanical attack.

9

Successive layers of resins and reinforcements (mats, fabrics, foams...). The reinforcement impregnation must be fair with a good wetting of the fibres by the resin and without formation of bubbles, blisters, etc.

9

Topcoat: final layer of resin intended to protect the composite on the opposite face to the gelcoat. This face is generally unaesthetic.

The reinforcement placement is manual and the resin is applied with a brush, a roller or a spray gun. Due to the resin shrinkage, it is necessary to design draft angles or to use a mould allowing the demoulding.

[Top co.tl

Layers of fabrics and ma,s

/ / /

I"~176 1

/ / / /

N~'ativ~ 7 7 ) r o T ' d /

/// Top coat[

~i

Layersof fabrics and mats impregnated by resin

oa,]

Figure 6.24. Principleof the hand lay-up moulding

415

Thermosets and Composites

Crosslinking is carried out at ambient temperature, at first in the mould for a sufficient time to obtain sufficient mechanical properties to allow the demoulding, then during storage in an unstressed state. Heating at limited temperature, 70 ~ for example, can accelerate this post-curing. Figure 6.24 shows the principle of hand lay-up moulding. Advantages of the process: 9 Inexpensive moulds and tools. The moulds can be built in glass fibre reinforced composites by the manufacturer. 9 Design freedom. 9 Suitability for very large parts such as mine hunters. 9 Suitability for very thick parts since it is possible to use as many layers of reinforcements and resin as desired. Moreover, it is possible to use specific reinforcements at particular points. o Particularly adapted for prototypes and small series, even for technical parts such as aeronautic components. 9 Possible partial automation. The process drawbacks are: 9 Slowness. 9 Environmental constraints according to national regulations. o Limitation of the number of parts, generally below 1000 parts per annum. 9 The influence of the experience and the dexterity of the workers. 9 High labour cost. 9 Rough, more or less regular, generally unaesthetic external face. Spray lay-up onto open mould

Spray lay-up is an alternative to hand lay-up in which a mixture of chopped glass fibre and resin is sprayed with a spray gun. To have high mechanical properties, fabrics and other reinforcements are manually arranged in successive layers. Due to the resin shrinkage, it is necessary to design draft angles or to use a mould that allows demoulding. Crosslinking is carried out at ambient temperature, first in the mould for a sufficient time to obtain sufficient mechanical properties to allow the demoulding, then during storage in an unstressed state. Heating at limited temperature, 70 ~ for example, can accelerate this post-curing. Advantages of the process are as for hand lay-up above, with the addition of:

9 Faster than hand lay-up. 9 Better automation opportunities than hand lay-up. 9 Output improvement compared to hand lay-up. Drawbacks of the process: 9 Investment in a special spray device to cut the roving, mix it with the resin and spray the mix. 416

Composites

o 9 9 o 9 o 9

Resin losses by spraying. Difficulty in obtaining regular thicknesses. Though faster than the hand lay-up, the process remains slow. Limitation of the series, generally below 1000 parts per annum. The influence of the experience and the dexterity of the workers. High labour cost. Rough, more or less regular, generally unaesthetic external face.

Hand lay-up or spray lay-up on core, without mould

A core is used to replace the mould. After the contact moulding of one face, the core can be removed if desired and hand lay-up or spray lay-up carried out onto the second face. Crosslinking is carried out at ambient temperature as above for hand or spray lay-up, again with the possibility of heating at limited temperature to accelerate post-curing. Vacuum bag moulding after hand or spray lay-up

After the composite has been manufactured (hand lay-up, spray lay-up, prepregs) onto its mould, an anti-adherent flexible sheet is applied onto it, and then a light vacuum is created by a suitable system (see Figure 6.25). The vacuum applies the sheet onto the laminate, which creates a compression of the composite and makes the free face more aesthetic. Heating can accelerate the hardening. Figure 6.25 shows the principle of vacuum bag moulding after hand or spray lay-up. Advantages of the process: 9 The upper face has a better finish. 9 The vacuum makes degassing easier and reduces bubbles and other voids.

Figure 6.25. Principle of the vacuum bag moulding after hand or spray lay-up 417

Thermosets and Composites

9 The possibility to cure in a heated oven to accelerate hardening. Disadvantages of the process: 9 More complex. 9 Additional investment required in vacuum device. 9 Necessity to tailor the bag according to the part and mould shapes. 9 Part size limited by the mould size. Pressure bag moulding after hand lay-up or spray lay-up

This process (Figure 6.26) resembles vacuum bag moulding but the vacuum is replaced by pressure. After the composite has been manufactured (hand lay-up, spray lay-up, prepregs) onto its mould: 9 An anti-adherent flexible sheet is applied onto it 9 The mould is closed with a reliable flat cover 9 Pressure is created by a suitable system. This pressure applies the sheet onto the laminate, which creates a compression of the composite and makes the free face more aesthetic. It is possible to combine vacuum and pressure: 9 First, vacuum is created in the bag to remove air, reducing bubbles and other voids 9 Then pressure is applied outside the bag to increase the compression of the laminate and improve material cohesion and mechanical properties. Figure 6.26 shows the principle of pressure bag moulding after hand or spray lay-up. Advantages of this process: 9 Improved finish of the upper face. 9 Better material cohesion. 9 Possibility to cure in a heated oven to accelerate the hardening.

Figure 6.26. Principle of the pressure bag moulding after hand or spray lay-up 418

Composites

Drawbacks of the process: 9 More complex. . Additional investment required in pressure device and more complex and resistant moulds. Necessity to tailor the bag according to the part and mould shapes. Part size limited by the mould size. Compression moulding in closed mould after hand or spray lay-up

There are two stages in this process" . First, two half-parts are hand or spray lay-up, one on a positive mould and the other on a negative mould. 9 Then, before hardening, the two half-parts are pressed together in a compression moulding press to stick them together (see Figure 6.27). Due to resin shrinkage, it is necessary to design draft angles or to use a mould that allows the demoulding. Crosslinking is carried out at ambient temperature, first in the mould for enough time to obtain sufficient mechanical properties to allow demoulding, then during storage in an unstressed state. Heating at limited temperature, 70 ~ for example, can accelerate this post-curing. Figure 6.27 shows the principle of press moulding after hand lay-up or spray lay-up. Advantages of the process: 9 The two surfaces are aesthetic if a gelcoat is used for each half-mould. ,, The pressure ensures a better cohesion of the composite, less bubbles and blisters. 9 Design freedom.

~, Figure 6.2Z

,.

i ///////////

Principle of the press moulding after hand lay-up or spray lay-up 419

Thermosets and Composites

9

Suitability for thick parts since it is possible to use as many layers of reinforcements and resin as desired. 9 Adapted for prototypes and small series. Drawbacks of the process: 9 Expense of two moulds for the hand lay-up and press investment. 9 Slower than hand lay-up or spray lay-up: there are two mouldings and a press step. Limitation of the part sizes by the press size. Limited output. The influence of the experience and the dexterity of the workers. High labour cost: there are two mouldings and the press step. The adherence between the two parts must be carried out satisfactorily. Risks of reinforcement moving. Casting or putting with filled resin

The filled liquid resin is poured into a closed two-part mould. The viscosity must remain sufficiently low to allow casting, which limits the fibre level and the fibre length. Reinforcements can be arranged in the mould before casting. The composite is cured into the mould at ambient temperature or in a heated oven to accelerate the hardening. This process is mainly used with liquid polyurethanes and silicones. Putting (spreading with putty resin) is sometimes used for electric and electronic insulation with epoxies. In this last case the material is often not removed from the mould. Advantages of this process: 9 Simplicity. 9 Low investment, cheap moulds. 9 Good appearance of the faces. 9 Possibility to cure in a heated oven to accelerate the hardening. Drawbacks of the process: 9 Part sizes are limited by the mould size. 9 Reinforcement limitation by the limited fibre length and level. 9 The labour costs are high. 9 The output rates are low. 9 The process is suited for small and medium outputs. Injection-reaction of reinforced resin - RRIM and SRRIM

In the injection-reaction processes: 9 An injection unit doses and mixes the reinforced thermoset resin and catalyst. 9 The mix is discharged under low pressure (0.5 MPa for example) through an injection cone, in the closed mould. 420

Composites

9

The two (or more) parts of the resin react together in the closed mould. The injection pressure is not negligible and the moulds must be rather rigid and resistant. The precision of the cavity and the quality of its surfaces govern the precision and finish of the parts. There are two main alternative methods: 9 RRIMReinforced Reaction Injection M o u l d i n g - the resin is reinforced with chopped glass fibres that are added to one of the resin parts. 9 SRRIMStructural Reinforced Resin Injection M o u l d i n g - dry reinforcements are placed in the mould before injection. Another alternative uses vacuum in addition to the injection pressure, which makes the degassing easier. Figure 6.28 illustrates the principle of SRRIM.

Figure 6.28. Principle of the SRRIM: Structural Reinforced Resin Injection Moulding

Advantages of the process: 9 Proportioning and mixing are automated. 9 Little skilled labour is required. 9 Possibility to place the reinforcements in the mould before injection. o Moderate labour costs. 9 Fair aspect quality for the whole part surface. 9 Suitability for medium range outputs. 421

Thermosets and Composites

Drawbacks of the process: 9 Investments required for injection machine and pressure-resistant moulds. 9 Risk of displacing the reinforcements. 9 The limited part sizes according to the mould size. 9 H o n e y c o m b s are not usable because the resin fills the cells. Infusion process, vacuum bag moulding, vacuum impregnation moulding, SCRIMP, RIFT, VARTM, RFI

There are two main infusion-based methods: 9 Infusion of a liquid resin that impregnates the reinforcements 9 Use of a resin film that is heat-melted to impregnate the reinforcements. Some of the infusion processes are patented. Infusion comprises several stages (see Figure 6.29)" 9 The dry reinforcements are manually placed in a mould. 9 A n anti-adherent airtight film or flexible sheet is applied onto it, and then vacuum is created by a suitable system. 9 The vacuum sucks in the liquid resin that impregnates and wets the reinforcements. 9 The vacuum applies the sheet onto the laminate which creates a compression of the composite and m a k e s the free face m o r e aesthetic. 9 Heating can accelerate the hardening. In the RFI (Resin Film Impregnation) alternative: 9 Films of solid resin are inserted b e t w e e n the reinforcements. 9 A n anti-adherent airtight film or flexible sheet is applied onto the mould. o V a c u u m is created by a suitable system to remove air. 9 The solid resin is melted by heating, and then impregnates and wets the reinforcements. 9 The resin is hot-cured. Figure 6.29 shows the principle of the infusion process.

Figure 6.29. Principle of the infusion process 422

Composites

Advantages of the process: 9 The upper face has a better aspect. 9 The v a c u u m makes the degassing easier and reduces bubbles and other voids. 9 The m o u l d has only one part; the u p p e r part is replaced by a less expensive bag. 9 The possibility to cure in a h e a t e d oven to accelerate hardening. Disadvantages of the process: 9 More complex. 9 It is essential to use very low-viscosity resins with risks of lower p e r f o r m a n c e in terms of final characteristics. 9 Additional investment required in vacuum device. 9 Necessity to tailor the bag according to the part and mould shapes. 9 Part size limited by the mould size. 9 H o n e y c o m b s are not usable because the resin fills the cells. R T M - Resin transfer moulding and other alternatives such as VARI, VacFIo

The principle is similar to infusion moulding but the whole mould is constructed of machined solid material. 9 The dry reinforcements are manually placed in the mould. Preforms can be used. 9 The mould is closed. 9 The liquid resin, injected u n d e r low pressure, impregnates and wets the reinforcements. 9 The composite is cured at ambient or elevated t e m p e r a t u r e . In the V A R I ( V a c u u m Assisted Resin Injection) process: 9 V a c u u m is created by a suitable system to r e m o v e air and m a k e the wetting and reinforcement impregnation easier. This process is developing well in general-purpose applications such as in aeronautics or other high-tech uses. Figure 6.30 shows the principle of V A R I . Advantages of the process: 9 Two beautiful faces, if gelcoats are applied onto the two half-moulds. 9 Fewer risks of bubbles, blisters, etc. 9 High fibre levels can be used. 9 M e d i u m labour costs. Drawbacks of the process: 9 More complex. 9 Risk of displacing the reinforcements. 9 R e i n f o r c e m e n t wetting may be difficult in specific spots. 9 Additional investments: two moulds, feeding and vacuum devices. 9 H o n e y c o m b s are not usable because the resin fills the cells. 423

Thermosets and Composites

I wc--o I

ISe""'"

"1

IWc "oo I

Figure 6.30. Principle of the V A R I - Vacuum Assisted Resin Injection

Cold compression moulding This process uses a press and two matched tools often constructed from composites. 9 A gelcoat is applied onto the tools. 9 The suitably shaped reinforcement is placed into the mould. 9 The necessary quantity of thermoset resin is poured into the mould. 9 The press closes the mould. . The resin cures without heating. The moulding pressure is low (some bars maximum) and the moulds are not heated. Consequently they can be relatively simple and cheap. Advantages of the process: . Fair appearance of the whole part. 9 No heating. . Intermediate outputs between contact moulding and hot compression moulding. ,, Improved compaction of the material. Drawbacks of the process: 9 Average outputs. 9 Average investments. Examples of applications: car, heavy lorry and caravan body elements; small boats; exterior panels for building, containers, baths, tubs, tanks... Hot compression moulding This process uses a press and two matched tools. There are three main alternatives" 9 Placement of an SMC preform into the heated mould. 9 Filling of the mould with a suitable quantity of BMC or other premix. 424

Composites

9

Wet process as for cold compression moulding: The necessary quantity of thermoset resin is poured into the mould containing the suitably shaped reinforcement. In all cases, heating accelerates the resin curing but makes the process more complex. Advantages of the process: 9 The production cycles are much faster and this process type becomes essential for mass production. 9 High compaction and very good mechanical properties with the continuous reinforcements such as SMC and prepregs. Drawbacks of the process 9 Higher investments in presses, rigid and heat-resistant moulds. 9 Need to prepare the reinforcements and lay them out suitably. Examples of applications 9 Automotive" bumpers, shields, doors and hood elements, roofs... 9 Electrical engineering: boxes, housings.

Compression-transfermoulding This process uses two matched tools and a special press equipped with a transfer-chamber and two rams: 9 One to transfer the material from the transfer chamber to the cavities of the mould 9 One to close the mould. This method is applicable to thermoset resins reinforced with discontinuous fibres. The material contained in the transfer chamber is transferred by the pressure of a ram into the cavities of the mould. The design of the machines and the moulds requires special consideration to preserve the fibres and their reinforcing action. Figure 6.31 shows the principle of compression transfer moulding. Advantages of the process: 9 Faster than compression moulding. 9 Lower labour cost. 9 Multiple cavities in the same mould. 9 Better material cohesion. Disadvantages of the process" 9 Limited reinforcement because of the need to use chopped fibre filled resins without continuous fibres. 9 Difficult mould design to preserve fibre lengths. 9 Investments: special press and relatively expensive moulds. 9 Slower process than high-pressure injection. Examples of uses 9 All technical parts from small to medium sizes and moderate reinforcement. 425

Thermosets and Composites

Figure 6.31. Principleof the compression transfer moulding

High-pressure injection moulding High-pressure injection is applicable to chopped fibre reinforced thermoplastics and thermosets including BMCs. The temperatures used are higher than 100 ~ and the pressures broadly exceed 100 bars. The injection moulding machines (see Figure 6.32) consist of: 9 A ram or screw extrusion machine, with suitable temperature control device which ensures the material plasticization and its transport towards the injection and metering unit, 9 A metering unit controlling the injected volume, 9 A press and a mould. This is: o Cooled for the solidification of a thermoplastic matrix. o Heated to ensure the hardening or cure of a thermoset matrix. There are several steps during processing: 9 The material is transported by the screw (Figure 6.32) or the ram (not shown in Figure 6.32) 426

Composites

Figure 6.32. Principleof the high-pressure injection moulding

9

The required volume of material is metered by a controlled translatory motion of the screw or the ram 9 The material stays in the mould long enough to cool the thermoplastics or cure the thermosets before demoulding. Figure 6.32 shows the principle of high-pressure injection moulding. The machines and the moulds must be specially designed to preserve the fibres and their reinforcing action. Advantages of the process: 9 High outputs, especially with multi-cavity moulds. 9 Moulding of complex parts with variations of thickness. 9 Very good size accuracy. 9 Excellent surface aspect. 9 Excellent cohesion of the material. Disadvantages of the process: 9 High investments for the presses. 9 Expensive moulds. 9 Difficult to preserve fibre lengths. 9 Need to limit the reinforcements to fibre lengths on the order of millimetres or a few centimetres. Examples of applications 9 Technical parts for electricity, industry... 9 Car parts: body elements, headlight parabolas, heating elements.

Prepreg draping Pre-impregnated rovings, tapes, tows, fabrics, cut to the right shape and size, are hand or machine laid-up onto a mould surface. 427

Thermosets and Composites

9

H a n d lay-up: it is possible to use all other types of reinforcements such as honeycombs or foams. All shapes, sizes and thicknesses are feasible. 9 A u t o m a t e d lay-up: there are numerous degrees of automation with more or less complex machines. Figure 6.33 displays the basic principle for an a u t o m a t e d tape placement. For t h e r m o s e t matrices, hardening occurs by v a c u u m or pressure moulding in oven, autoclave or m o r e rarely by electron b e a m irradiation.

Consolidationroller I ] Heatingdevice [ I Placementroller [

[

Incomingtape

ring device [

Previouslayers

]

Figure 6.33. Principle of an automated tape placement machine

Advantages of the process: 9 H a n d lay-up: e Design freedom. e Moulding of complex parts with variations of thickness. e Lower investments. 9 A u t o m a t e d lay-up: e Faster than hand lay-up. e Lower labour costs. e Better repeatability. Disadvantages of the process: 9 H a n d lay-up: e High labour costs. e Skilled labour required. e Risks of placement errors. o Slow. 9 A u t o m a t e d lay-up: o Heavy investments. o Skilled labour required. o Limited design possibilities. Examples of applications

428

Composites

9 9

Hand lay-up: prototypes, technical parts... A u t o m a t e d lay-up: aeronautics elements.

Filament winding, automated lay-up There are two main methods: 9 Wet lay-up: roving is on-line impregnated by immersion in a bath of resin before its placement by the machine. 9 Prepreg placement" the prepregs are directly laid-up by the machine. Continuous fibres or prepregs are wound up on a mandrel which turns on an axis. The fibres can be placed: 9 Perpendicular to the axis: circumferential winding or 90 ~ filament winding. 9 Parallel to the axis: 0 ~ filament winding. 9 Sloped at defined angle on the axis: helical winding. The mandrel can be recoverable, or can be integrated in the finished part, for example, in the inner liner of high-pressure tanks. Heating in oven or autoclave causes hardening. Although applied mainly to thermoset matrices, this process can also be used with some thermoplastic composites. On-site machines: for construction of very large tanks there are specific machines that build the tank on-site overcoming the transport problems. Figure 6.34 shows the principle of filament winding. Advantages of the process: 9 The reinforcement levels can reach 60% to 75%, even 80%, making it possible to obtain excellent mechanical characteristics. 9 The properties can be enhanced in chosen directions by modifying the winding angle. 9 Part sizes can be significant. 9 The process can apply to continuous fibre reinforced thermoplastics. Disadvantages of the process: 9 Heavy investments. 9 Limited design and shapes. 9 The reinforcement placement must be carefully calculated. Examples of applications: 9 High-pressure tanks with metal inner liner. 9 Tanks, silos, rail tankers. 9 Pipes, masts. 9 Car drive shafts. 9 Helicopter blades, wind turbines. 429

Thermosets and Composites

Figure 6.34. Principleof the filament winding

Centrifugal moulding The reinforcement, generally an on-line chopped roving, and the resin are projected inside a rotating mould. Thanks to the centrifugal force, the reinforced resin is laid out on the inner side of the mould. By its principle, 430

Composites

this process can be used only for parts that can be revolved, such as tubes, pipes, tanks. Advantages of the process: 9 The external part face is generally smooth, rich in reinforcements because of the centrifugal force and the higher density of the fibres. 9 For the same reasons the internal face is rich in resin which improves its impermeability and its corrosion resistance. Disadvantages of the process: 9 Discontinuity. 9 Relatively slow. Examples of uses: tubes, pipes, tanks. Pultrusion

In this continuous process: 9 The continuous reinforcements are suitably impregnated on-line with the resin. 9 The shape is obtained by going through a die. 9 The composite is crosslinked in an oven heated between 120 ~ and 150 ~ 9 A pulling group ensures the drive of the profile. Additional systems make it possible, subsequently, to curve the profile but the section form being given by the die is identical all over the length. This process is adapted to the realization of complex, hollow or full sections, with high mechanical characteristics thanks to the high unidirectional reinforcement levels. Figure 6.35 shows the principle of pultrusion.

Figure 6.35. Principleof the pultrusion 431

Thermosets and Composites

Advantages of the process: 9 Excellent mechanical properties in the profile axis. 9 Practically unlimited length. 9 Smooth surfaces except cut ends. 9 Continuous production. 9 Possibility of application to reinforced continuous thermoplastics. Disadvantages of the process: 9 Exclusively profile manufacturing. 9 Limited sizes in transverse section. 9 Unidirectional reinforcement. 9 Limited reinforcement choice. 9 Significant investments. Examples of applications: all rectilinear or curved profiles.

fibre

Pullwinding, overbraiding These processes combine two elementary techniques: 9 Filament winding or an interlacing reinforcement method of the textile industry such as braiding, 9 The pultrusion process. Figure 6.36 shows the manufacturing of a tube with two reinforcements wound on a mandrel, the resin impregnation, the pultrusion die and a heated oven. The same scheme is available for braiding instead of filament winding. Advantages of the process: 9 General: o Continuous o Low labour cost.

Figure 6.36. Principle of the pullwinding 432

Composites

9 o

Especially for the overbraiding technique Better impact behaviour than filament winding due to the interlacing of the reinforcements. o More complex shapes possible. Disadvantages of the process 9 Significant investments 9 Restricted shape possibilities. Application examples: 9 Aerospace: aircraft propeller blades, missile nose cones. 9 Recreational: Masts, skis, hockey sticks, golf shafts, paddles. Continuous stratification of plates and sheets, corrugated or ribbed plates

In this continuous process: 9 The reinforcements and the thermoset resin are laid out on a continuously unwinding film that supports them and acts as a mould. 9 After impregnation assisted by pressing rollers, a second film is applied onto the sheet. 9 Curing is carried out in an oven. Subsequently, shaping (corrugated or ribbed sheets) can be obtained before curing by passing through shaping rollers. Figure 6.37 shows the principle of continuous stratification.

Shaping rollers Resin

Oven

Film ~ - ~ Sheet Figure 6.37. Schematic continuous sheeting

Advantages of the process: 9 Continuity. 9 Low labour cost. Disadvantages of the process: 9 Significant investments. 9 Exclusively used for plates and sheets.

433

Thermosets and Composites

6.7.2 Thermoplastic composites Numerous processing methods described for thermoset composites are more or less suitable for thermoplastic composites, after some alterations. We propose one possible classification for the main processes: 9 Stamping and compression moulding of GMT sheets 9 High pressure moulding: o Injection o Composite insert moulding o Compression moulding o Compression/transfer o Extrusion-compression 9 Prepreg draping 9 Filament and tape winding 9 Continuous processes: o Pultrusion o Pultrusion-coextrusion. Stamping and compression moulding of GMT sheets Stamping or compression moulding at temperatures close to the melting point of the matrix can be used to produce parts made with GMTs: 9 The stamping technique is completely similar to the stamping of metal sheets: the pre-cut blanks are heated to their softening point near the melting temperature of the matrix and are quickly transferred into the tools mounted in a stamping press. 9 By compression moulding: o For fast compression moulding, the pressures are about 15 to 20 MPa with cycle times from 20 to 50 seconds. The shapes can be complex and the surface aspect is better. The creep is very significant. The minimal thickness is of the order of i mm. o Low-pressure compression moulding is carried out under much lower pressures (0.5 to 3 MPa) and at lower temperatures. The creep is less significant and the shape must be relatively simple and near that of the blank. The surface aspect is not so good but, on the other hand, the process allows a fabric to be laid on it to give a textile effect. For polypropylene GMT, which is the most commonly used: o The softening temperature can be of the order of 200 ~ o The demoulding temperature is about 100 ~ The main steps of this process are: 9 Storage of the pre-cut blanks 9 Heating of the blanks 9 Stamping. Automated transport devices handle the blanks and finished parts. Figure 6.38 shows the principle of stamping. 434

Composites

Figure 6.38. Principleof the stamping

Advantages of the process: 9 High outputs close to those obtained with metals. 9 Possibility of making large parts. 9 Low labour costs. 9 Attractive final prices. Disadvantages of the process" 9 Limited choice of matrices. 9 Heavy investments. 9 Limited shapes. Examples of uses: Automotive and transport: bumpers, crosspieces, inserts for dashboards, phonic shields, seat frames... Storage, handling: containers, tanks. Miscellaneous" welding helmets, ventilator shells, lawn mower bases.

Injection, compression, compression-transfer The principles are already described in section 6.7.1 above. Unlike for thermosets, the moulds are cooled to solidify the thermoplastic matrices. Advantages of the injection process: 9 High outputs, especially with multi-cavity moulds. 9 Moulding of complex parts with variations of thickness. 9 Very good size accuracy. 9 Excellent surface appearance. 9 Excellent cohesion of the material. Disadvantages of the process: 9 Need to limit the reinforcements to fibre lengths of the order of millimetres to a few centimetres. 9 High investments for the presses. 9 Expensive moulds. 9 Difficulty of preserving fibre lengths. 9 Part sizes limited by press sizes. 435

Thermosets and Composites

Examples of applications: 9 Automotive, electricity, industry, etc.: all elements of small or medium sizes.

Composite insert moulding, co-moulding It is possible to use thermoplastic composite inserts to" 9 Reinforce injected parts locally. A more lightweight part can be made by reinforcing it at specific spots with an insert of unidirectional composite manufactured, for example, by filament winding. 9 Obtain specific properties using, for example, a self-lubricating composite insert. Discontinuous fibre reinforced thermoplastic composites can also be overmoulded onto G M T sheets. Figure 6.39 displays the reinforcement of a bush with an inner unidirectional composite insert. The principle is the same for a bush with a self-lubricating insert.

Figure 6.39. Principle of the composite insert moulding

Extrusion-compression Two basic processes are combined: 9 The thermoplastic composite is heated and plasticized in a screw extrusion machine that feeds a mould. 9 The part is compression moulded into the cooled mould. Figure 6.40 shows the principle of the extrusion-compression process. Advantages of the process: 9 Possibility to use longer fibres than with the injection process. Disadvantages of the process: 9 Discontinuous fibres. 9 Limited choice of reinforcements. 9 Higher labour costs. 9 Specific equipment. 436

Composites

Figure 6.40. Principle of the extrusion-compression process

Prepreg draping

The process is similar to thermoset draping. The consolidation is obtained by heat and pressure: vacuum or pressure bag moulding, autoclave... Solidification requires cooling. Filament and tape winding

The process is similar to the thermoset process described above but a heating head replaces the impregnation one to ensure the preconsolidation. A post-consolidation can be obtained by heat and pressure: specific pressure device, vacuum or pressure bag moulding, autoclave... Solidification requires cooling. Pultrusion

The impregnation device of the thermoset machines is replaced by a heating device to soften the pre-impregnated rovings. Rollers consolidate the composite before passing through a cooled die to solidify the thermoplastic matrix. Pultrusion-extrusion

A thermoplastic is extruded onto the reinforcements impregnated with the thermoset resin before passing through the pultrusion die. 6.7.3 Sandwich composites

Let us remember that a sandwich structure is made up of: 9 A core of foam, wood, honeycomb... 437

Thermosets and Composites

9

Two skins of r e i n f o r c e d resin sheets firmly b o n d e d o n t o the core to o b t a i n high rigidity. T h e skins can be m a d e of r e i n f o r c e d t h e r m o s e t s , G M T s or metals. S o m e t i m e s t h e r e is only one skin that s u r r o u n d s the core completely. This is the case for sailboards, for example. 9 Subsequent edge protection. The curing of the adhesive bonding is carried out by heat and pressure: specific device, vacuum bagging, autoclave, press... The cores and the final parts can have any shape: parallelepipedic for a lot of sandwich panels, shaped parts for the hulls of boats or b u m p e r s and SO o n .

There are several problems to solve: 9 The shaping of the core" t h e r m o s e t and metal cores are generally machinable only. The linear foams are t h e r m o f o r m a b l e . 9 The gluing of the skins onto the core uses adhesives in film or liquid form. The small size of the h o n e y c o m b areas that are available for bonding makes it difficult. 9 Metal and other water or moisture-sensitive materials need the structural sandwich to be waterproofed. 9 Styrene or other solvent-sensitive foams must be protected. Figure 6.41 shows the principle of the sandwich structure. Several manufacturing methods are used: 9 Prefabrication of the two skins and joining on the two faces of the core. 9 Application of a skin in G M T on each face of the core. o H a n d lay-up or draping of the skins on the shaped core. 9 Injection of foam between the two prefabricated skins. o Use of an expandable polymer insert that expands during the paint setting.

Figure 6.41. Principle of the sandwich structure 438

Composites

Advantages of these processes: o Foams and honeycombs lead to excellent properties/weight ratios. Foams are cheaper than honeycombs and are developed in generalpurpose applications such as automotive and transport. Honeycombs have higher performance and are used in aerospace applications. . Plywood leads to very good properties/price ratios and better compression strength. Disadvantages of these processes: 9 The compression strength of the foam and honeycomb sandwich composites can be low. 9 With wood and honeycombs, it is difficult to make complex shapes. Examples of applications: 9 Automotive and transport, shipbuilding, mass distribution sports and leisure: the core is generally made of foams as PVC, polyethylene... and the skins are often glass fibre reinforced unsaturated polyester or GMT. 9 Aerospace, top-of-the-range sports and leisure: the core is generally made of honeycombs or high-performance foams and the skins are often carbon fibre reinforced epoxies or polyimides. 6.7.4 Finishing operations Surface finishing and painting The glass fibres at the composite surface are attack points and can, moreover, be used as wicks for fluid absorption from the surrounding medium. Parts without gelcoat or other coatings, IMC (In Mould Coating) for example, must be protected and can be decorated by painting, or more rarely by metallization. The surface of the composite must in general be prepared by mechanical or chemical treatment to ensure a good coating adherence: 9 Sandpapering with a very fine abrasive after puttying if necessary. Sandpapering with coarse or medium abrasive particles exposes the reinforcement fibres, which would allow them to be stripped off, and is unsuitable. 9 Degreasing with: o Alkaline detergents followed by efficient rinsing, o Or suitable non-aggressive solvents that do not deteriorate the matrix and are not absorbed by the matrix or the reinforcements. 9 Finally, surface treatment such as Corona discharge. The application of primers and finishings is advised to ease the paint bonding and to fill up the pores. Currently, the most common paints are polyurethanes, polyesters, polyepoxy and acrylic resins. 439

Thermosets and Composites

The nature of all the products and the temperatures of all the treatments will have to be compatible with the matrix and the reinforcements. Metallization Metallization can have decorative or technical goals, particularly: 9 Electrical conductivity for electromagnetic shielding 9 Abrasion resistance for nickelled salmons for helicopter blades... Several metallization techniques are usable after careful preparation of surfaces: 9 Painting with conductive paints (with silver or other metals). This is used for electromagnetic shielding. The paints containing oxidizable metals (copper, nickel, for example) will have to be protected with a varnish to ensure the durability of the conductivity. 9 Electroplating for decorative purposes. 9 Electroless plating for EMI shielding. 9 Vacuum metallizing. o Sputtering. 9 Zinc arc spray. 9 Zinc flame spray. o Ionic deposit: it is then necessary to apply a protective varnish onto the metal deposit. After some of these metallizing treatments it is necessary to apply a protective coating. The chemical products and treatments can degrade the composite's performance. Machining Practically all the rigid composites are more or less easily machined by almost all metal or wood machining methods after some degree of adaptation of the tools and processes: 9 Sawing, drilling, turning, milling, tapping, threading, boring, grinding, sanding, polishing, engraving, planing... 9 Other machining techniques can also be used, for example: o Laser cutting o Hyperbar fluid cutting. Some precautions must be taken: 9 Carbon and glass fibres are very abrasive and high-speed steel tools wear out quickly. For intensive use, carbide and diamond tools are preferable. 9 Machining destroys gelcoats if they exist. To avoid the risks of later attack, it is necessary to reapply a new gelcoat locally. 9 For anisotropic composites, machining cannot be carried out in any direction. Drilling, for example, can only be done perpendicularly to the layers. 440

Composites 9

The low thermal conductivity and the decrease of mechanical characteristics at high temperature limit the machining temperature and it is necessary to cool and reduce the tool feed motion. Machining is suited for: 9 Prototypes and low outputs of complex parts made from blanks whose manufacturing could be simplified. 9 Correction of parts with tight tolerances. Assembly Welding and solvent joining do not apply to the thermoset composites because of the crosslinking. With thermoplastic matrices, the reinforcement complicates these processes. Welding is not used very much. Adhesive bonding Bonding does not present particular difficulties except for polypropylene composites and is used to assemble composites with composites, plastics or metals. Adhesive bonding avoids damage of the parts by drilling and allows an excellent distribution of the stresses. The parts can have structural functions if the adhesive is correctly chosen, and if one takes care: 9 To make the adhesive joints work in shear and not in peel 9 To have a sufficient surface stuck to bear the loads 9 To prepare surfaces well. In all cases, it should be remembered that a permanent or cyclic loading is more detrimental than an instantaneous one. All types of adhesives are usable, for example: 9 Hot melt adhesives: the molten adhesive wets surfaces of composites and other substrates to be assembled and interlocks them while resolidifying on cooling. It is necessary for the materials to be assembled to tolerate the temperature of the molten adhesive. Joining is sensitive to temperature approaching the melt point of the adhesive joint. However, some hot-melt adhesives crosslink after joining and become less sensitive to heat. 9 Non-reactive solution adhesives: the solvent wets surfaces to be assembled, then evaporates involving the cohesion of the parts to be assembled by the adhesive joint. The heat behaviour is generally in an intermediate range. If the solvent swells the materials to be assembled, there can be migration of materials and subsequent cracking by residual internal stress relaxation. 9 Reactive adhesives: after wetting the surfaces to be assembled, there is polymerization of the adhesive joint. The heat behaviour can be better than with the preceding methods. Mechanical assembly 9 Click and spring work, clamping, snap-fit. The impact strength of certain composites allows their assembly by stretching as click-and441

Thermosets and Composites

spring work, clamping, snap-fit... For easy assembly, the assembly angle must be shallow, generally lower than 30 ~ and the strain must be much lower than the elastic limit. 9 Riveting: If the rivet is not of the same material as the part, it can later induce stresses by differential thermal expansion. Two techniques of riveting are used: o Hot: pre-heating of the rivet, then crushing of the head. o With ultrasound: generally properties and durability are better. 9 Screwing. Autotapping screws: the screw type, the diameter of the hole which receives the screw, and the tightening torque depend on the composite used. Repeated screwing and unscrewing is not advised. As a first approximation and as examples, it is sometimes stated that: o The external diameter of embossing must be double the external diameter of the screw. o The length of the threads engaged in the embossing material must be twice as long as the external diameter of screw. o Embossing should not be located on a welded line and the screw should not engage totally. o The use of inserts allows repeated screwing/unscrewing, higher tightening torques and limits the risks of failures. Press fitting: subject to correct calculation of the diameters, the press fitting of metal and composite parts gives good results. Durability depends on the creep behaviour of the material. The metal elements must be round, smooth and clean, and the metal must be compatible with the selected composite. Embossing must be distant from weld lines and the moulding must be particularly careful to limit the residual stresses.

6.7.5 Repairing composites A good professional can correctly repair the mass diffusion or intermediate-performance composites with a thermoset matrix. For the high-performance composites or sandwich structures, repairs, when they are possible, are always much more delicate. However, repair work is carried out in applications where safety is paramount such as in civil aircraft. There are several possibilities: 9 Carry out a cosmetic repair for minor damage. The appearance is fair but the composite is imperfectly protected. 9 Remake a gelcoat. The composite is correctly protected from the environment but the mechanical performance is not restored. 9 Rebuild the composite in situ. This is generally the best solution. The appearance is good, the composite is correctly protected from the 442

Composites

environment and the mechanical properties are satisfactorily restored. 9 Make a patch and bond it onto the damaged composite. This is a good solution if the patch is almost identical to the original composite and if the bonding is well carried out. The appearance can be good, the composite is correctly protected from the environment and the mechanical performances can be suitably restored. . Make a patch and bolt it on the damaged composite. This is a good solution if the patch has the same performance as the original composite and if the bolting doesn't weaken the composite. The composite is unaesthetic but is correctly protected from the environment and the mechanical performance can be sufficient. The surface is not smooth, which can disturb the flow of fluids. For the simplest cases of repair, the steps are: 9 Surface damage: o Cleaning, o Puttying, o Sandpapering, o Coating with gelcoat or paint. 9 Deep damage: o Removal of the layer soiled by the surrounding medium (for example, water for boats, chemicals for tanks), o In-situ re-stratification to replace the destroyed reinforcements, o Surface reconstitution as for surface damage.

6.8 Examples of composite characteristics 6.8.1 Basic principles

The reinforcement is the most important parameter in determining the mechanical properties. Table 6.29 suggests a classification example of the numerous reinforcement possibilities: 9 Approximately, the reinforcement performance of the fibres increases from the top to the bottom of the table. . There is no possible comparison between fibre, flat core and 3D preform reinforcements. The matrix is the most important parameter in determining the other properties: . Thermal behaviour, durability, chemical and fire resistance. 9 However, the matrix makes a significant contribution to the mechanical performance in nanocomposites and discontinuous fibre composites. The reinforcement~matrix adhesion is essential to the final properties. 443

Thermosets and Composites

Table 6.29

Classification of the main reinforcement possibilities

Morphology

Nature

Form

Arrangement

Nanofillers

Nanosilicates

Unit

Random

Fibre reinforcement Short fibres:

Glass fibres

Unit

Random

Aramid fibres

Unit

Random

Carbon fibres

Unit

Random

"Long" fibres:

Glass fibres

Unit

Random

"Continuous" fibres:

Natural fibres

Matted

Mat

Glass fibres

Matted

Mat

Interlaced

Woven, braided, etc.

Unit

Unidirectional

Matted

Mat

Interlaced

Woven, braided...

Unit

Unidirectional

Matted

Mat

Interlaced

Woven, braided, etc.

Unit

Unidirectional

Aramid fibres

Carbon fibres

Flat coresand 3D preforms Flat cores

Wood, plywood

Flat

Core

Foams

All shapes

Core

Honeycombs

Flat

Core

3D preforms

6.8.2 Nanocomposites

The reinforcement ratios are moderate but there are other advantages: 9 The low filler level leads to a small density increase. 9 It is possible to decrease the gas permeability. 9 Better fire-retardant behaviour. On the other hand: o Nanocomposites are newly developing materials. 9 The exfoliation is essential for efficiency but is difficult to obtain. Table 6.30 displays some examples of nanocomposite properties. 444

Composites Table 6.30

Examples of nanocomposite properties

Polyamide

Polypropylene

1.15

0.9

GPa

3.3 to 4.3

1.8 to 2.2

Tensile or flexural strength

MPa

69 to 92

35 to 46

Elongation at break

%

8 to 60

Izod notched impact

J/m

34 to 50

H D T A (1.8 MPa)

~

100 to140

Density

g/cm 3

Tensile or flexural modulus

6.8.3 Short fibre composites 6.8.3.1. Significant parameters

Practically all the properties are influenced by the addition of fibres. The significant parameters are" 9 Nature of the fibre. 9 Addition level. 9 Real sizes of fibres in the finished part, the aspect ratio particularly. 9 Homogeneity of the fibre distribution in the finished part. 9 Sizing, which governs the fibre/matrix adhesion. Effect of the fibre nature

Table 6.31 shows the properties of the same thermoplastic reinforced with the same level of the three main reinforcement fibres, illustrating the effect of the fibre nature. Table 6.31 Property examples of the same thermoplastic reinforced with the same level of the three main reinforcement fibres

Shortfibre reinforcedpolyamide

E glass

Aramid

Carbon

Density, g/cm 3

1.29

1.19

1.23

Tensile strength, MPa

100

95

207

Tensile modulus, GPa

5.3

5.1

13

5

6

250

222

3

2

1012

1013

Elongation at break, % H D T A (1.8 MPa), ~ Coefficient thermal expansion, 10-5/~ Resistivity, ohm.cm

250

106

Effect of the fibre level

Table 6.32 shows the properties of the same thermoplastic reinforced with increasing levels of the same short glass fibre. 445

Thermosets and Composites

Table 6.32 Property examples of the same thermoplastic reinforced with increasing levels of the same short glass fibre Glassfibre, % by weight

0

10

20

30

40

50

Density, g/cm 3

1.14

1.21

1.29

1.37

1.46

1.57

Water absorption, 24 h, %

1.3

1.2

1

0.8

0.7

0.6

7

4

3

2.5

2

1.5

H D T A (1.8 MPa), ~

75

232

250

255

255

255

Shrinkage, %

1.9

0.9-1.3

0.7-0.9

0.5-0.8

0.4-0.7

0.3-0.5

Strength, MPa

50-60

70-95

100-135

135-175

165-210

175-250

Modulus, GPa

1.5

2.4-3.2

4.2-5.3

6-7.5

8-10

9-13

Elongation at break, %

55

10

5

4

3

2.5

Izod notched impact, kJ/m 2

12

8

13

16

18

17

1013

1013

1013

1013

1013

1013

Coefficient thermal expansion, 10-5/K

Resistivity, ohm.cm

The effect of the fibre content varies for different properties: 9 Some of them obey a law of mixtures such as density and water absorption. 9 Others continuously decrease or increase as the fibre level increases. 9 The impact strength decreases for small levels and then increases. 9 The resistivity is quasi constant. Generally, the addition of fibres: 9 Increases the mechanical property retention when the temperature rises. 9 Improves the creep behaviour. 9 Can cause some anisotropy according to the fibre orientation. This leads, for example, to different shrinkage in different directions. 9 Increases viscosity and makes the processing more difficult. 6.8.3.2. Short glass fibres

Table 6'33 shows some basic property examples of short glass fibre reinforced thermoplastics and thermosets. In some cases the glass fibres are combined with mineral fillers. Table 6.33

Property examples of short glass fibre reinforced plastics

Thermoplastic matrices PP

PA

PC

PEEK

Density

g/cm 3

1.1-1.2

1.3-1.4

1.35-1.5

1.5

Tensile or flexural strength

MPa

40-70

100-160

90-160

150-180

Tensile or flexural modulus

GPa

4-8

5-9

6-10

9-12

Elongation at break

%

2-3

4-7

2-4

2-3

446

Composites Table 6.33

Property examples of short glass fibre reinforced plastics Thermoplastic matrices PP

PA

PC

PEEK

Izod notched impact

J/m

45-160

130-160

90-200

95-130

H D T A (1.8 MPa)

~

120-140

230-260

140-150

290-315

Coefficient of thermal expansion

10-5/~

2-3

2-3

2-4

1.5-2

Resistivity

ohm.cm

1016-1017

1012-1013 1015-10a6

1015-1017

Thermoset matrices UP

PF

MF

EP

2

1.7-2

1.5-2

2

Density

g/cm 3

Tensile or flexural strength

MPa

60-100

60-200

35-180

40-200

Tensile or flexural modulus

GPa

7-11

10-25

11-20

10-30

Elongation at break

%

1-3

1

1

1

H D T A (1.8 MPa)

~

160-250

150-250

170-310

120-260

Coefficient of thermal expansion

10-5/~

1.5-3

1.5-3

1-3

2-3

Resistivity

ohm.cm

1012

101~

1010-1012 1014-1015

6.8.3.3. Short carbon fibres

Table 6.34 shows the properties of the same thermoplastic reinforced with increasing levels of carbon fibres. As already seen, the effect of the carbon fibre content varies depending on which property is being considered: 9 Some of them obey a law of mixtures such as density and water absorption. 9 Others, tensile or modulus, increase as the fibre level increases. The strength reaches a ceiling but the modulus continuously increases. 9 The impact strength decreases for small levels and then increases. 9 The resistivity decreases significantly; for example, the resistivity of neat PA is roughly 1012 but that of PA6 with 30% CF is 102 (Table 6.35). Table 6.34 Property examples of the same thermoplastic (PA) reinforced with increasing levels of carbon fibres

Carbonfibre, %

Flexuralmodu~ GPa

Izodnotchedimpac~J/m

0

Tensi~swength, MPa 81

2.8

48

10

152

6.5

43

20

207

13

75

30

241

18

96

40

255

24

100

50

262

34

107 447

Thermosets and Composites

Generally, the addition of fibres: 9 Increases the mechanical property retention when the temperature rises. 9 Improves the creep behaviour. 9 Can cause some anisotropy according to the fibre orientation. This leads, for example, to different shrinkage according to the direction. 9 Increases viscosity and makes the processing more difficult. Where glass fibre is replaced by the same level of carbon fibre: 9 The modulus of a carbon fibre reinforced resin is roughly twice that of the same resin reinforced with the same weight of glass fibres. 9 The tensile strength is enhanced of 15 to 50%. 9 The impact strength of a carbon fibre reinforced resin is lower than that of a glass fibre reinforced resin, but the modulus is much higher. Table 6.35 shows some basic property examples of short carbon fibre reinforced thermoplastics. Table 6.35

Basic property example of short carbon fibre reinforced thermoplastics PPE

POM

PBT

PC

PA6 or 66

PA Ar

Carbon fibre, %

<20

20

30

30

30

30

Density, g/cm 3

1.2

1.46

1.41

1.31

1.26

1.34

Tensile strength, MPa

140

170

160

170

230

240

Tensile modulus, GPa

10

17

17

16

19

25

Izod notched impact, J/m

70

60

100-130

80-100

50

H D T A (1.8 MPa), ~

115-135

160

220

140

215-255

220

102

103

103

103

102

103

PSU

PESU

PEI

PPS

PEEK

LCP

Carbon fibre, %

30

20-30

25

30

30

30

Density, g/cm 3

1.36

1.45

1.37

1.46

1.44

1.5

Tensile strength, MPa

160

150-190

200

170

210

190-240

Tensile modulus, GPa

17

16

16

18

13-20

34

Izod notched impact, J/m

80

45-75

55

80-110

350-100

H D T A (1.8 MPa), ~

185

215

210

260

315

220

Resistivity, ohm.cm

10 2

10 2

104

102

105

103 tol0 4

Resistivity, ohm.cm

6.8.3.4. Short aramid fibres

The reinforcing effect is similar to that of glass fibres with some minor differences: 9 10% lower density. 448

Composites

9 Lower HDT. 9 Higher moisture take-up, similar to the neat resin. Table 6.36 shows some basic property examples of short aramid, glass and carbon fibre reinforced polyamide. Table 6.36

Basic property examples of short aramid, glass and carbon fibre reinforced polyamide

Shortfibre

Aramid

Glass

Carbon

1.19

1.29

1.23

Tensile strength, MPa

83 to 110

100

207

Tensile modulus, GPa

5.1

5.3

13

Density, g/cm 3

6

10

H D T A 1.8 MPa, ~

Charpy notched impact, kJ/m 2

222

250

230

Resistivity, Ohm cm

1013

1013

104

6.8.4 Long fibre reinforced plastics: LFRT and BMC

According to the nature of the matrix one distinguishes: ,, LFRT: Long Fibre Reinforced Thermoplastics, for example Celstan, Compel, Twintex, Verton. , BMC: with thermoset matrices, which were the original and remain the most used. Practically all the properties are influenced by the addition of fibres. The most significant parameters are: 9 Addition level. ,, Real sizes of fibres in the finished part, the aspect ratio particularly. . Homogeneity of the fibre distribution in the finished part. ,, Sizing, which governs the fibre/matrix adhesion. LFRT processing

9

Grades reinforced with fibres 10 mm long can be processed on conventional injection equipment by simply adapting the processes to preserve the fibres. 9 Grades reinforced with fibres 20 mm long and more cannot be processed on conventional equipment. It is necessary to use, for example, the extrusion/compression technique. The process is differs too much from conventional injection used for short glass fibre reinforced thermoplastics to measure the influence of fibre length only. BMCs are processed on special injection or compression equipment. Table 6.37 displays some basic property examples of long glass fibre reinforced polyamides and polypropylenes. 449

Thermosets and Composites

Table 6.37

Basic property examples of long glass fibre reinforced polyamides and polypropylenes

Polypropylenes Glassfibre weight

%

30

40

50

60

Density

g/cm3

1.12

1.22

1.34

1.59

Tensile strength

MPa

46-107

55-124

92-131

262

Tensile modulus

GPa

4-6.9

4.2-9

7.8-13.8

18.6

Notched Izod impact

J/m

213

265

295

295

40

50

60

Polyamides Glassfibre weight

%

30

Density

g/cm 3

1.36

1.45

1.56

1.69

Tensile strength

MPa

197

155-257

190-304

230-323

Tensile modulus

GPa

10.4

11.4-14.4

12.8-18.6

22-23.5

Notched Izod impact

J/m

270

213-373

347-621

375-670

The long glass fibres lead to: 9 Maximum values of the strengths and moduli of the same order as those obtained with short carbon fibres, definitely higher than for short glass fibres. 9 Attractive [impact strength/modulus] ratios. 9 A better retention of properties than with short glass fibres when the temperature increases. Table 6.37 shows some basic property examples of long glass fibre reinforced BMCs. 6.8.5 "Continuous" fibre

composites

In this category, not all the reinforcement fibres are truly continuous (certain SMC for example) but they all have a longer length than in the L F R T and BMC. The mechanical performances evolve with: o The fibre nature. 9 The fibre level. o The aspect ratio (length versus diameter) for the chopped fibres or the form of the fibres (filament, roving, fabrics...) for the truly continuous fibres. 9 The orientation and the quality of the fibre dispersion, the anisotropy in the final part. For example, the tensile strength of unidirectional composites can be greater than 2000 MPa in the fibre direction and less than 100 MPa in the transverse direction. 9 The treatment of the fibres to enhance the adhesion to the matrix. 9 The real length of the fibres in the final part. 450

Composites

Table 6.38 displays some basic property examples of glass fibre reinforced SMCs with unsaturated polyester, vinylester, phenolic and epoxy matrices. Basic property examples of long glass fibre reinforced BMCs Unsaturated polyester (UP) and vinylester matrices Glassfibre weight, % 7 10-20 22-28 18 Grade General General General FR purpose UP purpose UP purpose UP halogen-free UP Density, g/cm 3 1.76 1.7-1.9 1.76-1.95 1.95 Shrinkage, % 0.02 0.01--0.2 -0.06-0.15 0.18 Water absorption 24 h, % 0.1-0.2 0.1-0.3 0.1-0.2 0.1-0.2 Tensile strength, MPa 30-40 34-41 30-40 30-35 Flexural strength, MPa 55 40-135 90-115 90 Compression strength, MPa 110 Flexural modulus, GPa 5.5 7-11 9-11 9 Izod notched impact, J/m 267-417 HDT A (1.8 MPa), ~ >200 >200 >200 >200 Specific heat, cal/(g. ~ 0.26-0.34 0 . 2 6 - 4 ) . 3 4 0.26-0.34 Coefficient thermal expansion, 10-5/~ 2 2 2 2 Resistivity, ohm.cm 1012-1014 1012-1014 1012-1015 1011-1014 Dielectric constant 4 4 Dielectric rigidity, kV/mm 10-15 10-15 10-15 10-15 Oxygen index, % 34 22-45 22-32 46-80 UL94 rating V0 HB to V0 HB to V0 V0 GF GF GF GF reinforced reinforced reinforced reinforced vinylester, UP vinylester vinylester low density Glassfibre weight, % Unknown 25 22 25 Density, g/cm 3 2 1.91 1.72 1.43 Tensile strength, MPa 48 29 39 33 Flexural strength, MPa 114 92 100 91 Compressive strength, MPa 150 Flexural modulus 20 ~ GPa 21 12 12 10 150 ~ GPa 7.5 7.3 7.5 Notched Izod impact strength, J/m 188 Un-notched Izod impact strength, J/m 192 246 226 HDT A (1.8 MPa), ~ >260 Dielectric constant 4.3 Dielectric rigidity, kV/mm 14 FR GF reinforced phenolic resin VO Glassfibre weight, % 25 Flexural strength, MPa 77-86 Flexural modulus @20 ~ GPa 7-8 @150 ~ GPa 5.5-6 @175 ~ GPa 5-5.5 Un-notched Charpy impact, kJ/m 2 18-20 HDT A (1.8 MPa), ~ >250 Oxygen index, % 98-99 UL fire rating V0 Ageing for 2500 h in hot air @150 ~ modulus retention, % 90 @175 ~ modulus retention, % 70-80 @200 ~ modulus retention, % 40-75 451 @200 ~ strenght retention, % 10-35 Table 6.38

Thermosets and Composites

Table 6.39 gives some typical property examples of carbon fibre reinforced SMCs with epoxy matrices, while Table 6.40 displays some basic property examples of glass mat reinforced unsaturated polyesters. Table 6.39

Basic property examples of glass fibre reinforced SMCs

Unsaturated polyester matrix Glassfibre weight, % Density, g/cm 3 Shrinkage, % Absorption of water, 24 h, % Tensile strength, MPa Flexural strength, MPa Elongation at break, % Tensile modulus, GPa Flexural modulus, GPa HDT A (1.8 MPa), ~ Glass transition temperature, ~ Specific heat, cal/(g. ~ Coefficient thermal expansion,10-5/~ Resistivity, ohm.cm Dielectric constant Dielectric strength, kV/mm Oxygen index, % UL94 fire rating

10-20 1.7-1.8 0.05-0.15 0.1-0.7 90-120

6-8 >200 0.26-0.34 2 1012-1014 10-15 22-24 HB to V2 VO

25-30 1.7-1.9 -0.1-+0.18 48-110 150-210 1.6-2 10-12.5 7.5-14 >200 140-210 0.26-0.34 1.6-2.3 1011-1014

32-40 1.77-1.84 -0.08-+0.1 0.3-0.7 210-420

50 1.63 0.01 0.1-0.2 80-105 200

11-15 >200

11-16 >200

0.26-0.34 2 1012-1014

4 10-15 10-15 22-27 HB to V2 25% GF VO halogen free 1.95 0.04 0.1-0.2 40-50 120 5.5 >200 0.26-0.34 2 1012-1014

Density, g/cm 3 Shrinkage, % Absorption of water, 24h, % Tensile strength, MPa Flexural strength, MPa Flexural modulus, GPa HDT A (1.8 MPa), ~ Specific heat, cal/(g. ~ Coefficient thermal expansion, 10-5/~ Resistivity, ohm.cm

1.84-2.1 -0.04-+0.1 0.2-0.3 51 130-200 11 >200 0.26-0.34 2 1011-1014

Dielectric constant Dielectric rigidity, kV/mm Oxygen index, %

4 10-15 10-15 50-78 45-50 phenolic or epoxy resin Vinylester GF Phenolic GF 55 Unknown 1.8 1.6-1.8 190-220 100 330-360 130-170 160-190

89 Glass fibre weight, % Density, g/cm3 Tensile strength, MPa Flexural strength, MPa Compression strength, MPa 452

0.26-0.34 2 1011-1014 10-15

SMC with UD fibres 1.8 -0.03-+0.3 92-285 230-750 14-22 >200 0.26-0.34 1.1-1.5 1011-1014 4 22

Epoxy GF Unknown 140-245 350-490 140-210

Composites

Flexural modulus @20 ~ GPa @150 ~ GPa Izod notched impact, J/m HDT A (1.8 MPa), ~ Oxygen index, % UL rating

~nylester GF 15-17 1400 >200

Phenolic GF 6-10 4-7

Epoxy GF 14-21 1600-2160 288

>200 50-90 V0

Tables 6.41 to 6.47 display basic property examples of, respectively: glass mat thermoplastics (GMT); glass fabric and roving reinforced composites; thermoplastic prepregs; aramid reinforced unsaturated polyesters; carbon fabric reinforced unsaturated polyesters; aramid reinforced unidirectional composites in the fibre direction; and carbon reinforced unidirectional composites. Table 6.40

Basic property examples of carbon fibre reinforced SMCs with epoxy matrix

Shrinkage, %

0.1

Water absorption, 24h, %

1.6

Tensile strength, MPa

280-350

Flexural strength, MPa

500-665

Compression strength, MPa

210-280

Elongation at break, %

0.5-2

Tensile modulus, GPa

70

Flexural modulus, GPa

35

Izod notched impact, J/m

800-1080

Barcol hardness

55-65

HDT A (1.8 MPa), ~

288

Continuous use temperature, ~

130-230

Thermal expansion coefficient,10-5/~

Table 6.41

0.3

Basic property examples of glass mat reinforced unsaturated polyesters

Matrix

Unsaturatedpolyester

Unsaturatedpolyester

acrylateurethane

Glass mat weight, %

20-30

40-50

33

Density, g/cm 3

1.3-1.5

1.5-1.75

Tensile strength, MPa

65-90

130-170

112-131

Flexural strength, MPa

115-145

180-220

206-218

Compression strength, MPa

110-135

165-200

145-174

2

2

2-3

Elongation at break, %

453

Thermosets and Composites

Table 6.41

Basic property examples of glass mat reinforced unsaturated polyesters

Matrix

Unsaturated polyester

Unsaturated polyester

acrylate urethane

20-30

40-50

33

Tensile modulus, GPa

5-7

9-10

6-7

Flexural modulus, GPa

5-7

9-11

6-7

Glass mat weight, %

Compression modulus, GPa

5-6

Interlaminar shear strength (ILSS), MPa

24

Izod notched impact, J/m HDT A (1.8 MPa), ~ Thermal conductivity, W/mK Thermal expansion coefficient,10-5/~

Table 6.42

1410 >200

>200

0.14-0.19

0.2-0.3

3-4

2-2.4

>200

Basic property examples of glass mat thermoplastics (GMT) Glass mat reinforced polypropylene

Glass content, %

30

40

40

40

43

Density, g/cm 3

1.13

1.19

1.2

1.2

1.21

Tensile strength, MPa

70-85

77

95

105

250

Flexural strength, MPa

120

145

155

155

160

Elongation at break, %

3

4

3

2

2

Tensile modulus, GPa

5

5.8

7

4.8

8

Notched impact, kJ/m 2

54

10

HDT A (1.8 MPa), ~

153

154

165

156

158

170

170

170

170

170

1.4-2.9

2.7

2.7

2.7

2.6

Melting or softening point, ~ Coefficient of thermal expansion, 10-5/~

132

PET

PA

PPO

PC

Glass content, %

30

30

30

30

Density, g/cm 3

1.55

1.35

1.28

1.4

Tensile strength, MPa

110

73

125

160

Flexural strength, MPa

185

122

205

185

Elongation at break, %

3

3

7.4

6.8

7

8

50

55

Tensile modulus, GPa Un-notched impact strength, kJ/m 2

35-110

HDT A (1.8 MPa), ~

210

210

220

160

Melting or softening point, ~

256

215

290

230

Coefficient of thermal expansion, 10-5/~

1.5

454

Composites Table 6.42

Basic property examples of glass mat thermoplastics (GMT)

PEI

PPS

Glass content, %

30

Unknown

Density, g/cm 3

1.47

1.36-1.66

Tensile strength, MPa

190

160-370

Flexural strength, MPa

210

280-450

Tensile modulus, GPa

11

13

Un-notched impact strength, kJ/m 2

50

HDT A (1.8 MPa), ~

230

270

Melting or softening point, ~

Table 6.43

280

Basic property examples of glass fabric and roving reinforced composites

Unsaturatedpolyester and acrylate urethane % reinforcement

40-50 glass fabric

50-60 glass fabric

Density, g/cm 3

1.5-1.75

1.6-1.85

Tensile strength, MPa

200-240

240-275

260-300

400-800

Flexural strength, MPa

220-260

260-300

380-410

400-500

Compression strength, MPa

150-180

180-200

220-240

Elongation at break, %

50 glass roving

70-80 glass roving 1.9-2.1

2

2

1.6-2

2

Tensile modulus, GPa

10-14

14-18

17-20

21-26

Flexural modulus, GPa

10-14

14-18

10-12

Compression modulus, GPa

13

ILSS, MPa

28-29

Izod notched impact, J/m HDT A (1.8 MPa), ~ Thermal conductivity, W/mK Thermal expansion coefficient,10-5/~

1300-1470 >200

>200

>200

>200

0.19-0.25

0.25-0.31

0.37-0.41

1.8-2.2

1.6-1.8

1.2-1.4

Polyepoxies Reinforcement

Glassfabric

Density, g/cm 3

1.9

Tensile strength, MPa

400

Tensile modulus, GPa

24

HDT A (1.8 MPa), ~

<250

Continuous use temperature, ~

150-190 455

Thermosets and Composites Table 6.43

Basic property examples of glass fabric and roving reinforced composites

Polyimides %, reinforcement

60-70, glassfabric

Density, g/cm 3

1.9-2

Water absorption, 24h, %

0.3

Barcol hardness

70

Tensile strength, MPa

350

Flexural strength, MPa

70

Flexural modulus, GPa

28

ILSS, MPa

14-15

Izod notched impact, J/m

700

Thermal expansion coefficient,10-5/~

Table 6.46 polyester)

1

Basic property examples of carbon fabric reinforced acrylate urethane (unsaturated

%, reinforcement

50, carbonfabric

Tensile strength, MPa

500-540

Flexural strength, MPa

360-375

Compression strength, MPa

140-150

Elongation at break, %

1.4-2

Tensile modulus, GPa

42

Flexural modulus, GPa

20-25

Compression modulus, GPa

33

ILSS, MPa

21

Izod notched impact, J/m

Table 6.44

710-780

Property examples of thermoplastic prepregs

Thermoplastic

PP

PP

PET

Glassfibre, %

60

75

65

Density, g/cm 3

1.5

1.7

1.95

Tensile strength, MPa

350

420

440

Compression strength, MPa

160

140

410

Tensile modulus, GPa

15

21

25

HDT A (1.8 MPa), ~

159

159

257

456

Composites Table 6.45

Basic property examples of aramid reinforced acrylate urethane (unsaturated polyester)

%, reinforcement

40, aramid

Tensile strength, MPa

250-260

Flexural strength, MPa

340-360

Compression strength, MPa

150-170

Elongation at break, %

2.2

Tensile modulus, GPa

12

Flexural modulus, GPa

10-11

Compression modulus, GPa ILSS, MPa

20

Izod notched impact, J/m

Table 6.47

13

470-500

Basic property examples of aramid reinforced UD epoxy composite in the fibre direction

Density, g/cm 3

1.37

Tensile strength, MPa

1450

Tensile modulus, GPa

87

H D T A (1.8 MPa), ~

<250

Continuous use temperature, ~

150-190

6.8.6 Sandwich composites

The sandwich composites combine: 9

Light weight" densities are often less than 1 g/cm 3 compared to more than 1.5 g/cm 3 for the composites discussed above.

9

High flexural rigidity.

9

Medium to low tensile properties according to the tensile properties of the core. The tensile strength and modulus of a 100 kg/m 3 foam are roughly as low as 3 MPa and 0.1 GPa, respectively.

9

Good compression properties for cores made of honeycombs, wood and plywood. Low compression properties for foamed cores. The compression strength and modulus of a 100-kg/m 3 foam are roughly as low as 2 MPa and 0.1 GPa, respectively. On the other hand, pinpoint impact is distributed across the whole surface facing, providing it is sufficiently resistant.

Table 6.48 displays some examples of flexural modulus for sandwich composites. 457

Thermosets and Composites

Table 6.48

Basic property examples of carbon reinforced U D epoxy and polyimide composites Epoxy matrices

Testing direction

Fibre direction

Epoxy type

Transverse direction

180 ~

120 ~

180 ~

65

65

65

Fibre weight, % Density, g/cm 3

1.5-1.7

Tensile strength, MPa

1760-2840

1470-3040

Flexural strength, MPa

120 ~ 65 1.5-1.7

30-80

30-76

910-1810 780-1570

740-1570

Elongation at break, %

Compression strength, MPa

0.5-1.7

0.5-1.7

0.5-1

0.6-1

Tensile modulus, GPa

125-330

135-390

6-8

5-9

70-110

70-110

Flexural modulus, GPa

120-320

Compression modulus, GPa

125-320

ILSS, MPa Poisson's ratio

0.3-0.34

Thermal conductivity, W/mK Thermal expansion coefficient,10-5/~

0.27-0.34

2.9-50

2.9-50

0.6-1.1

0.6-1.1

-0.04-+0.09

-0.04-+0.09

3.75

3.75

Polyimide matrix Tensile strength, MPa

1210

Tensile modulus, GPa

115

Continuous use temperature, ~

6.8.7 F o a m e d

180-250

composites

6.8.7.1. Property e x a m p l e s o f RRIM, SRRIM

Table 6.49 lists some property examples of RRIM and SRRIM composites. Table 6.49

Flexural modulus and maximum load examples for sandwich composites Flexural modulus GPa

Facing

Core

Core density

Core thickness

Panel thickness

Flexural modulus,GPa

Unknown

Foam

0.1

12.7

Unknown

Foam

0.2

12.7

1.8

Unknown

Foam

0.4

12.7

2.5

Unknown

Foam

0.6

12.7

3.2

1.4

Unknown

Balsa

12.7

2.7

Unknown

Plywood

12.7

3.3

UP/glass mat

Foam

8

5

UP/light glass mat

Foam

4

5

UP/glass mat

Foam

4

8

UP/heavy glass mat

Foam

4

9

UP/light UD

Foam

4

12

UP/heavy UD

Foam

4

26

458

Composites

Table 6.49

Flexural modulus and maximum load examples for sandwich composites

Maximum load (N/m 2) between two supports 2 m apart Facings

Core

Aluminium

Core density

Core thickness

Foam

18

Panel thickness

Max. load, N/nil 330

Aluminium

Foam

28

600

Laminate

Foam

17

<100

Laminate

Foam

27

170

6.8.7.2. Foamed matrix composites

To reduce the weight of composites it is possible to foam the matrix. Table 6.50 displays some property examples of composites made of reinforced foamed matrices. Table 6.50

Property examples of RRIM and SRRIM composites

RRIM polyurethane Glassfibres, %

15

Density, g/cm 3

1.14

Shore hardness D

60-70

Tensile strength, MPa

20-27

Elongation at break, %

75-200

Flexural modulus, GPa

0.7-1.2

Izod notched impact, J/m

160-430

Thermal expansion coefficient,10-5/~

3

RRIM polyurea Reinforcement Reinforcement weight, % Density, g/cm 3 Tensile strength, MPa

Glassfibres

Glassfibres

Glassflakes

15

20

20

1.12

1.1-1.15

1.2

18-22

30

33

Elongation at break, %

100-150

65

12

Flexural modulus, GPa

0.3-1

1.4-2

1.3-1.5

5-9

4-6

HDT A (1.8 MPa), ~ Thermal expansion coefficient, 10-5/~

130-160 5-7

RRIM polyurea Reinforcement

Carbon fibres

Reinforcement weight, %

15

Density, g/cm 3

1.2

Tensile strength, MPa

42

Elongation at break, %

10

Flexural modulus, GPa

1.2-3 459

Thermosets and Composites Table 6.50

Property examples of RRIM and SRRIM composites

SRRIM polyurethane Glass fibre weight, %

15-20

55-60

Density, g/cm 3

0.4-0.6

1.6-1.7

Shore hardness, D

43-50

Tensile strength, MPa

17-23

154-259

Flexural strength, MPa

37-47

151-438

Elongation at break, %

2-11

1.8-2

Flexural modulus, GPa

1.2-1.6

7-15

350

350-1600

HDT A (1.8 MPa), ~

Izod notched impact, J/m

80-98

213->220

Thermal expansion coefficient, 10-5/~

0.8-1.5

0.8

6.8.7.3. Syntactic foams

Table 6.51 displays some property examples of syntactic foams. Table 6.51

Property examples of composites made of reinforced foamed matrices

Foamed unsaturated polyester SMC Glassfibre weight, %

20-33

Density, g/cm 3

1.3-1.43

Shrinkage, %

-0.08-+0.12

Water absorption, 24h, %

0.5-0.7

Tensile strength, MPa

40-71

Flexural strength, MPa

60-150

Flexural modulus, GPa

4.5-12

HDT A (1.8 MPa), ~

>200

Thermal expansion coefficient,10-5/~

1.7-2

Resistivity, ohm.cm

1011-1014

Dielectric constant

4

Dielectric rigidity, kV/mm

10-15

UL 94 fire rating

HB

Oxygen index, %

22

Glassfibre reinforcedfoamed epoxy composites Form of glassfibres, weight % Reinforcement weight, %

Chopped 38

Continuous Chopped Continuous 38

Grade

40

40

FR

FR

Density, g/cm 3

1.06

1.05

1.4

1.45

Flexural strength, MPa

130

136

220

230

Flexural modulus, GPa

6.8

6.6

9.4

9.5

ILSS, MPa

10-12

12

17

18

Glass transition temperature, ~

80-127

80-127

128-134

128-134

460

Composites

6.8.8 Hybrid composites

Each composite family has its advantages and drawbacks. Thus it is interesting to combine two composite families to benefit from their best properties and to mask their weaknesses. We choose the example of an association of: . An epoxy composite of high mechanical properties and 9

A phenolic composite having excellent fire-resistant behaviour and satisfying the severe public transport standards for smoke emission and toxicity. Table 6.52 compares the smoke behaviour (in identical units) for phenolic and epoxy resins compared against two other plastics. Table 6.52

Property examples of epoxy syntactic foams

Reinforcement

Glass balloons

Density, g/cm 3

0.7-1.0

Shrinkage, %

0.3-1.0

Water absorption, 24h, %

0.2-1

Tensile strength, MPa

15-30

Tensile modulus, GPa

3-5

Izod notched impact, J/m

8-13

Notched impact, kJ/m 2

0.5-1.5

H D T A (1.8 MPa), ~

90-120

Thermal conductivity, W/mK Table 6.53

0.15-0.25

Examples of smoke emission for selected plastics

Method Without flame

~YcTthflame

2

16

132-206

482-515

Vinylester resin

39

630

PVC

144

364

Phenolic resin Epoxy resin

Thanks to co-curing techniques, it is possible to simultaneously crosslink an epoxy and a phenolic resin. The epoxy prepreg is applied directly onto the honeycomb and then covered with phenolic prepreg. Both are cured simultaneously. This system is used, for example, in the production of the honeycomb sandwich structures for civil aircraft floors. Table 6.54 displays some property examples of fire-proofed epoxy and hybrid composite. 461

Thermosets and Composites

Table 6.54

Selected properties example of fire-proofed epoxy and hybrid composite Fire-proofed e p o x y

Co-cured EP/PF

Flexural strength

MPa

540

562

ILSS

MPa

42

45

Glass transition temperature

~

115

115

N

400

410

Peel strength of the honeycomb skin

6.8.9 Conductive composites

Composites can be rendered conductive, anti-static or resistant to EMI by several method, such as: . Metal coatings: application of sheets or strips of metal, metallization. 9 Addition of conductive ingredients in a sufficient quantity to exceed the threshold of percolation: metal powders, graphite, metal fibrils, carbon blacks. 9 Use of conductive reinforcements: metallized glass fibres, carbon fibres, steel fibres. The resistivities range from less than 1 ohm.cm up to 106 ohm.cm. The mechanical properties can be affected. Table 6.55 compares some properties of conductive and neat plastics.

Table 6.55

Examples properties of conductive and neat plastics Polypropylene

Fibres

None

Stainless steel

Carbon

Resistivity, ohm.cm

1017

10 3

10 3

30-40

41

41

1.3

1.4

4.3

ABS

PA66

PPO

Tensile or flexural strength, MPa Flexural modulus, GPa EMI grades compared to neat polymers Aluminium powder, %

0

40

0

40

0

40

1.1

1.57

1.1

1.48

1.1

1.45

Tensile strength, MPa

30--65

23-29

40-85

41

45-65

45

Elongation at break, %

3-60

2-5

150

4

2-60

3

1-3

2.5

1-3.5

5

2.5

5.2

6-10

4

5-14

2.2

3-8

1.1

100

95

85

190

110

110

Density, g/cm 3

Tensile modulus, GPa Thermal expansion coefficient, 10-5/~ H D T A (1.8 MPa), ~ 462

Composites

References Technical guides, newsletters, websites 3M, 3Tex, Airex, Alusuisse, Alveo, Asahi Fibre glass, Astar, Azdel, Baltek, BASE Bayer, Besfight, BF Goodrich, BFG Int, Bond Laminates, BP, Borealis, Bryte, Ciba, CO1 Materials, Cray Valley, Cytec, Diab, Dow, DSM, DuPont, EMS, European Alliance for SMC, Ferro, Fibre Glast, GE, Haufler, Haysite, Hexcel, Isosport, Jet Moulding Compounds, Lankhorst Indutec, LNP, MatWeb, MFC, Mitsubishi, Neste, Owens Corning, Parabeam, Plascore, PPG, PRW, Quadrant, Rhodia, R6hm, RTP, Sabic, Saint-Gobain, Scott Bader, Silenka, Sintimid, Soficar, SP Systems, Stratime Capello Systemes, Sulzer Composites, Symalit, Thermotite, Ticona, Toray, Tubulam, Twaron, Vetrotex, YLA, Zherco Plastics, Zoltek, Zyex. Reviews Plastics Additives & Compounding (Elsevier Science) Engineering & Manufacturing Solutions for Industry Composites (Ray Publishing, Wheat Ridge, CO 80033, USA) High Performance Composites (Ray Publishing) Modern Plastics (ModPlas.com) Reinforced Plastics (Elsevier Science) Techniwatch (CRIF) Papers [1] A. Garcia-Rejon et al. (Antec 2002, p. 410) [2] A.K. Bledzki, J. Gassan, M. Lucka, International Polymer Science and Technology, Vol 27, No. 8, (2000), p. T/75 [3] A.R. Bunsell, Fibre Reinforcements for Composite Materials, Elsevier [4] J. Klunder, Introduction to glass fibre reinforced composites, Second edition, (1993); available from: PPG Industries Fiber Glass bv, Mail Box 50, 9600 AB Hoogezand, The Netherlands

463

Chapter 7

Future prospects for thermosets and composites

Thermosets and Composites

The consumption of thermosets and composites is controlled by: 9 User market demand. 9 The ability to adapt these materials to the economic and technical market requirements and to propose technological advancements. 9 The capacity for innovation in terms of materials and processes. 9 Adaptability to the environmental constraints: recycling, sustainable matrices and reinforcements. The purpose of this exploratory study is to give background information on these various points.

7.1 The Laws and requirements of the market Apart from exceptional cases, any manufacturer is subject to general regulations induced by the economics of competition, customers' rights and requirements and the legislative arsenal. Figure 7.1 points out some of the main market constraints. While the majority of these points speak for themselves, others need to be restated.

Figure 7.1. Laws and requirements of the market 466

Future prospects for thermosets and composites

Reduction of production costs

Cost 9 9 9 9 9 9 9 9 9

prices are optimized by reductions in: The number of parts necessary to satisfy all the functions. Raw material costs. Weight of the parts. Investments. Payroll. Scrap. Manufacturing costs. Finishing costs. Joining and assembly costs.

Adaptability Customers' requirements, changing fashions and technological developments involve a shortening of product life cycles. The manufacturers thus turn to materials allowing fast and economic design and easy adaptation of the production equipment. Guarantee

The extension of warranty periods is viable only if the performance and the durability of the product make it technically possible. Operating cost

This depends on: 9 The costs of in energy, process fluids and others. 9 Maintenance expenses: simplification of maintenance and cleaning; reduction of repair and restoration operations. 9 Durability. User satisfaction

This is a combination of a multitude of objective or subjective parameters, for example: 9 Ease of use and maintenance 9 Reliability 9 Aesthetics. 9 Lack of noise and vibration in operation.

7.2 Thermoset and composite answers and assets The use of thermosets and composites makes it possible to satisfy some of the requirements listed above, provided all the players are involved from the beginning of the project and problems such as the process of transformation and downstream recycling are taken into account from the start of the design phase. The diagrams in Figures 7.2 and 7.3 propose general schemes of the services to involve and the parameters to be taken into account. 467

Thermosets and Composites

Design Project m a n a g e r

Marketing

M e c h a n i c s design office

Pricing office Environment department

Plastic design office

Styling

O&M department

Plastic design Mould maker

Plastic design office

O&M department

Moulder

I I

R h e o l o g y study

T h e r m a l study

Cost price Pricing office

I I

I I

O&M department

Testing Testing lab O&M department

I I I I

Quality insurance

I I

Processing

Figure 7.2. Design diagram

At the design stage it is necessary to seek: 9 The best performance/density/cost compromise giving the best cost with the lowest weight and sufficient performance levels to meet the requirements. Plastic/metal or plastic/wood/metal hybrid materials are sometimes excellent solutions. 9 Integration of the functions to reduce the number of parts and minimizes the costs of materials, processing, finishing, assembly/ joining and intermediate storage. 468

Future prospects for thermosets and composites

Draft scheme Characteristics Processing

I I

Style Cost

f

Functionality integration

Design Drawing and computing Characteristics Durability I

I Feasibility I Rheology/thermic/shrinkage Part conformity |

I [

Material cost II

[

Testing

I I I I

Environmental impact

I Processing method Finishing & assembly Recycling

Tool design

I I I I

Cycle time Cavity number Cost forecast

Cost price [ [

Processing cost

Control

I

] ]

Quality insurance

Figure 7.3. Project diagram

9 The design of the parts that optimizes the thicknesses and reduces weights and cycle times. 9 Processing methods that are adapted to the product, and that allow the series to be manufactured with the simplest tools and minimal investment. The combination of several techniques, for example extrusion or moulding and machining, can bring economic solutions. 9 The possibility of bulk colouring and in-mould decoration, which can simplify or avoid the finishing operations. 469

Thermosets and Composites

9 The simplest assembly and joining methods. At the manufacturingstep it is necessary to ensure: 9 The adequacy of the machines and tools for the parts to be manufactured and the materials to be processed, in order to ensure optimal properties and reduce waste. 9 Good maintenance of the machines and tools to ensure the accuracy of the size and geometry, combined with optimal properties, a minimum of finishing operations and a minimum of waste. 9 The reasonable use of quality assurance and strict procedures to make the production reliable and to limit wastes. Provided the design and manufacturing requirements are met, plastic components can offer: 9 Lower costs which, in certain cases, make it possible to develop new applications. 9 A light weight involving fuel savings for vehicles, reduced expenses for packaging and transport, decreased waste at the end of the product life. 9 Corrosion resistance decreasing the maintenance or renovation costs for boardings, roofs, etc and in composites. 9 Transparency for certain families and grades, such as unsaturated polyester glazings. 9 Better impact resistance than glass. 9 Greater design freedom than many traditional materials such as metals (realization of forms unrealizable with metals). 9 Reduction and miniaturization of parts by the integration of functions and co-transformation (combination of flexible and rigid parts or compact and cellular parts). 9 A faster adaptation of manufactured parts thanks to easier replacements and modifications of tools than with metals. 9 A shortened timeframe for design, development and manufacturing. 9 Aesthetic properties and versatility of surface aspects. 9 Possibility of bulk colouring. 9 Possibility of decoration to obtain traditional material appearances such as wood or metals. 9 Good thermal insulating properties allowing energy savings (building) and comfort improvement. 9 Good electrical insulating properties. 9 Damping properties: lower noise, improvements to comfort and safety (polyurethane foams for seating and so on). 9 Ease of handling and installation. On the other hand, it is necessary to be aware of the ageing, mechanical resistance and thermo-mechanical behaviour, which are different from 470

Future prospects for thermosets and composites

those of metals. The recycling of thermosets and composites presents some difficulties that are not generally solved in a satisfactory way. To achieve greater market penetration, thermosets and composites must enhance prices, performances, characteristics, productivity, ease of processing and recycling. Among the ways to success we can cite: 9 Improvement of the cost/performances ratios. 9 Improvement of the immediate and long-term characteristics, after use and ageing, for the conquest of structural parts. 9 Better thermal resistance. 9 Better weathering behaviour. 9 Enhancement of the colouring and surface appearance. 9 Improvement of the surface properties: scratch resistance, dusting, staining, tarnishing, chalking and so on. 9 Adaptability of the grades, which must satisfy the requirements of the market and develop specific properties, for example coefficient of friction, electrical conductivity, better combination of mechanical properties/thermal behaviour/electrical characteristics/ageing. 9 Availability of halogen-free fire-retardant grades. 9 Improvement of the adherence of paints, printing inks, adhesives. 9 Better low-temperature performances: the legal requirements are moving towards an increase in the impact resistances at low temperature with a ductile behaviour. 9 Ease of processing: improvement of the flow properties and the aptitude for injection lead to cycle time shortening and better productivity. 9 Improvement of the mould productivity: cooling, use of multiple cavities. 9 Automation of the process equipment. 9 Better control of the processes by statistical processing of the recorded parameters (SPC). 9 Development of new manufacturing methods. 9 On-line compounding to reduce costs and thermal degradation. 9 Hybrid combinations with non-plastic materials, for example: o Assembly of plastic panels onto a metal structure allowing very large objects to be obtained for extremely low investments. o Hollow glass fibre reinforced polyester elements filled with concrete to form rigid structures for modular dwellings. 9 Use of wastes and recycled materials to satisfy environmental requirements and lower the costs. 9 Management of recycling, which starts with the design reducing the diversity of the materials used, improving their compatibility, the marking of the parts and their dismantling ease. The subsequent waste collection, recycling and outlets require work on economical and technical issues. 471

Thermosets and Composites

7.3 Markets: what drives what? The forces driving development 7.3.1 Consumption trends

In round figures, after an average increase of 3 % per year during the 1990/ 2000 period, the consumption of thermosets might increase by up to 4 % per year during the next few years. The growth of the consumption of composites in industrialized countries is also approximately estimated at a few percent per year (see Table 7.1). Environmental regulations and trends favour: 9 Thermoplastic composites. 9 Sustainable materials. 9 Water-based or powder-based adhesives, coatings and so on. The preference granted to thermoplastics compared to thermosets and their composites stems from some inherent handicaps of the latter such as" 9 The relative scarcity of materials, equipment and manufacturers. 9 The additional curing step, consuming time and money. 9 The longer processing cycles. 9 Greater difficulty in recycling. Table 7.1 Annual growth (%) in major thermoset and composite consumption TheYmosets

Polyurethanes

4

Amino resins

3

Unsaturated polyesters

4

Phenolic resins

4

Epoxies

5

Combined total for the major thermosets

4

Composites Automobile & transportation

5

Corrosion protection

5

Shipbuilding

5

Electricity & electronics

4

Sports & leisure

4

Railway

4

Medical

4

Aeronautics

3

Building & civil engineering

2

Mechanics & industry

2

Combined total for composites

4

472

Future prospects for thermosets and composites

7.3.2 Requirements of the main markets

The 9 9 9 9

main expressed requirements are: Automotive: costs and recycling. Aeronautics" costs and durability. Electricity & electronics: costs, recycling, conductive polymers. Building and public works: durability with a 50-year objective, processing and cost. 9 Shipbuilding: durability, industrialized processing, and costs. 9 Sports & leisure: cost and low weight. 9 Railway: fire behaviour, cost, processing. 9 Medical: performance, biocompatibility, cost, processing. 9 Mechanical & industrial: cost, processing. For each market there are also underlying demands and the global requirement list can be estimated as follows" 9 Cost and [cost/performance] ratio. 9 Recycling and outlets. 9 Processing: the objectives depend on the market and cover all situations from fully automated processes for automotive mass production to unitary processes for prostheses. 9 Performance, including manufacturing possibilities from very small to giant parts. 9 Durability including aesthetics. The lifetime requirements vary from a few years to 50 years according to the market. 9 Light weight and [weight/performance] ratio. 9 Fire behaviour: halogen-free fire-retardant behaviour; low smoke emissions of low toxicity. 9 Electrical conductivity: from antistatic to metal conductivity.

7.4 Cost savings 7.4.1 Material costs

There are several ways to cut down material costs: 9 Choose a cheaper family with the proviso that the performances are of a sufficient level to satisfy the functions. 9 Use a reinforced grade to reduce the wall thickness and consequently the material weight. In ascending order of performance but also of cost, the most used reinforcements are: natural fibres, glass fibres, aramid fibres, carbon fibres. Carbon fibres, if their development leads to a substantial lowering of their cost, could solve many cost problems. 9 Increase the performances and costs to lead to a very substantial improvement in performances, particularly in the durability of the finished part, which reduces the number to manufacture and to recycle, and the associated costs. 473

Thermosets and Composites

7.4.2

Hybrids

The hybrid materials as defined and described in Chapters 1 and 2 above are developing because of the substantial cost cutting due to: 9 High function integration thanks to the plastic elements that allow integration of fixings, housings, embossings, eyelets, clips etc. avoiding: o The assembly of the integrated components. o The stacking of the dimensional defects of the integrated components. o Later operations of welding capable of causing deformations. . The combination of simple processes from plastic and metal technologies. Each material has its advantages and drawbacks. The hybrids that closely associate two or more families benefit from their best properties and mask their weaknesses. The polymer can often bring: 9 Aesthetics and style. 9 Global cohesion of all the components. o Damping. 9 Thermal and electrical insulation. The metals often bring: 9 Structural properties. 9 Impermeability. 9 Electrical conductivity. There are exceptions, such as high-pressure tanks, where the polymer composite provides the structural function. Several producers such as Bayer, Dow (LFT-PP concept), Rhodia (PMA and MOM processes) have developed their own hybrid technologies. A typical development is the front-end of recently introduced cars such as the Mini Cooper from BMW or Mazda 6 in which long glass fibre reinforced polypropylene is injected onto stamped metal. The weight saving is in the range of 30-35 % compared to traditional solutions with a high function integration. 7.4.3 Processing costs

Intensive processing research is based on several routes to reduce costs: 9 Globalization of the processing, from raw material to finishing. o Automation. , Industrialization. 9 Simplification. Some examples are listed below. 474

Future prospects for thermosets and composites

7.4.3.1. Example of compounding integrated on the process line

The integration of the compounding of long glass fibre reinforced thermoplastics on the process line is an example of the globalization and automation of the process. This technique brings cost savings and decreases the thermal and mechanical degradation by avoiding one step involving plasticization and re-heating of the material. In the principle, the glass fibres are chopped and added to the thermoplastic in a special extruder/mixer synchronized with the shaping processing equipment to feed it with plasticized, hot material. The economy is expected to be of the order of ~0.30 per kg and mechanical properties are improved. 7. 4.3.2. New or modified processes

Traditional processes can be modified to better industrialize the manufacturing of medium or short run manufacturing. A good example is Resin Transfer Moulding (RTM), which leads to numerous variations such as: D R I V (Direct Resin Injection and Venting); LRTM (Light RTM); RIRM (Resin Injection Recirculation Moulding); SCRIMP (Seeman's Composite Resin Infusion Moulding Process); V A R I (Vacuum Assisted Resin Injection); V A R T M (Vacuum assisted RTM); and VIP (Vacuum Infusion Process). In the thermoplastic composite field, the "Pressure Diaphorm Process" allows the processing of continuous fibre reinforced thermoplastic with low pressures. The press and the moulds (wood, composite or aluminium) can be about 70% cheaper. The process is convenient for short and medium runs in the range of 1000 up to 100 000 parts. 7.4.3.3. Integrating finishing in the process

In-mould coating with special gelcoats and in-mould decoration with films reduce the finishing operations. If the process and its operating conditions are suitable, the demoulded parts are finished. As an example, composite manufacturer Quadrant Plastics Composites is studying three solutions for the decoration of GMT body panels: 9 Coil-coated aluminium 9 PMMA-based films (Senotop) already used for the Smart City Coup6 roof. 9 PP-based films. 7.4.4 Low-cost tool examples

There are numerous solutions. We cite a selection. 9 The LCTC (Low Cost Tooling for Composites) process developed by Boeing for short run manufacturing of parts by the autoclave process combines the use of aluminium plates and honeycombs bonded with a RTV adhesive. The machining is carried out in two steps, partly 475

Thermosets and Composites

before adhesive curing and finally after cure before surface sealing. A cost saving of 35-50% is claimed. This technique has been used to produce 50-part runs. 9 The Modular Tooling Concept developed by Intellitec for aerospace RTM applications. The principle is to use" o Common mould base for several parts of homogeneous sizes. o Interchangeable cavity sets for each part. In the case of a helicopter project, two modular moulds could produce thirteen parts with a cost saving of 60% versus traditional tooling. 9 The RenTooling System uses an aluminium honeycomb and an epoxy paste to produce lightweight and stable tools. 9 Water-soluble tooling materials such as Aquacore or Aquapoured can be moulded and machined to make strong cores that are then eliminated by water washing. The machining of the moulds is highly simplified.

7.5 Material upgrading and competition 7.5.1 Carbon nanotubes (CNT)

Carbon nanotubes are hollow carbon cylinders with hemispherical endcaps of less than 1 nm to a few nanometres in diameter and several microns in length. The aspect ratios are in the order of 1000 and more. The elementary nanotubes agglomerate in bundles or ropes that are difficult to disaggregate. The main properties are: 9 Very high modulus of the order of 1000 GPa and more. 9 Very high tensile strength of 50 000 MPa and more. 9 A low density: 1.33 g/cm 3. 9 High electrical conductivities with a very high current density of the order of 109 A/cm 2. 9 High thermal conductivities of the order of 6000 W / m K . 9 Very high cost: ~1 million per kg in 2000. ~100 000 and more per kg in 2002. ~100 per kg expected in 2005. The CNT developments in the polymer field concern: 9 Polymer reinforcement. 9 Compounding with polymer to obtain extrinsic conductive polymers with nanotube levels lower than 1% to produce ESD, EMI compounds and ultra-fiat screens. 9 High thermally conductive polymers for electronics. Industrialization of these developments is foreseen in few years. 476

Future prospects for thermosets and composites

7.5.2 Molecular reinforcement

The concept of polymer reinforcement by monomolecular fibres is already old but many studies date from the last decade. The interest is particularly the very high aspect ratios and the levels of reinforcement with expected mechanical properties as high as: 9 50 GPa up to more than 400 GPa for the modulus, 9 1000 MPa up to more than 40 000 MPa for tensile strength. This is a difficult technique and today the best laboratory samples reach: 9 100 GPa up to 300 GPa for the modulus, 9 1000 MPa up to 3000 MPa for tensile strength. Industrialization is not currently foreseen. 7.5.3 Polymer nanotubes

The Max-Planck Institute has developed a process to manufacture polymer "nanotubes" with submicronic sizes of the order of hundreds of nanometres. The mechanical properties would be expected to be attractive. Industrialization is not yet in sight. 7.5.4 Nanofillers

The main problem with nanofillers is the need for complete exfoliation. Some special compounding techniques have been developed such as, for example, the ZSK M E G A compounder by Coperion Werner and Pfleiderer with a special screw configuration. Following GM and Toyota, Fiat projects new applications for nanocomposites in the form of PA fuel lines incorporating PA nanocomposite barrier layers from Ube. Fiat expects to launch this development on a new car model in 2003 or 2004. Ube developed the PA nanocomposite named "Ecobesta" to replace PVDF or other traditional barrier materials. The all-polyamide structure offers recycling advantages compared to traditional multi-material designs. It incorporates: 9 A P A l 2 outer layer; 9 A PA6/12 adhesive layer; 9 A PA6/66 barrier layer incorporating 2% nanoclay; 9 A PA6 inner layer in contact with the fuel. Ube produces the PA nanocomposites by the in-situ polymerization route. 7.5.5 Short fibre reinforced thermoplastics to compete with LFRT

Borealis has developed a high performance short glass fibre reinforced polypropylene (HPGF) family that has the technological and economical potential to replace long glass fibre (LFRT) in highly stressed parts for technical automotive applications. 477

Thermosets and Composites

The advantages of the L F R T products are offset by requirements to optimize the whole process chain including extruder screw design, processing parameters and mould design, thus needing higher investment and production costs. By contrast, the processing of H P G F compounds requires no additional investments as it utilizes standard injection moulding machines. The high performances of H P F G are due to a better coupling of fibre and matrix, and the properties are near those of the L F R T grades with some advantages: 9 Lower emissions, lower fogging and lower odour than L F R T grades. 9 Improved weldability, increased flowline and weldline properties. 9 Better fatigue behaviour. Xmod TM G30 grade containing 30% glass fibres shows, compared to a conventional 30% GF reinforced polypropylene: 9 A significant improvement of tensile modulus over a range of temperatures tested up to 140~ 9 Better impact behaviour. 9 Significantly increased tensile strength to 115-120 MPa. Compared to LFRT, H P G F brings: 9 Retained weldline strength over twice the value for L F R T grades. 9 Superior fatigue behaviour, as measured by fatigue crack growth rate. 9 Tensile strength in the 115-120 MPa range versus 125 MPa for an LFRT. 9 Slightly lower impact strength. These improved properties of H P G F grades make them suitable for use in the automotive industry, with the potential to replace metal or long glass fibre polypropylene: 9 Front-end carriers moulded in H P G F grades could be an economically better solution than those using L F R T polymers. 9 Dashboard carriers: low emission and fogging values are achievable with HPGF. 9 Pedal carriers: H P G F performs better than LFRT in weldline behaviour. 9 Air intake manifold applications. 9 Fan supports and shrouds, drive belt covers, blower wheel covers, bases for air filters, battery supports, engine covers and parts for the cooling system are further potential applications. 7.5.6 Thermoplastic and thermoset competition

There are numerous examples ranging from mass production, such as automotive applications, to the high-tech industry such as aeronautics. We mention two examples: 478

Future prospects for thermosets and composites

9

9

The use of BMC or glass fibre reinforced polyamide for engine covers: the two techniques are industrialized. One is predominant in the USA, the other in Europe and Japan. The main characteristics are roughly similar, as shown in Table 7.2. The use of glass and carbon fibre reinforced thermoplastics for aircraft elements.

Table 7.2

Property examples of BMC and glass fibre reinforced polyamide BMC

PA

10-30

30-43

Flexural strength, MPa

40-135

175-210

Flexural modulus, GPa

5-11

6-9

Glass weight, %

HDT A, ~ Melt temperature, ~ Izod notched impact, J/m Thermal expansion coefficient, 10-5/~

>260

248-251

Non-fusible

255-260

300-600

100-250

1.4-2

2-3

There are numerous studies and some industrialization of fibre reinforced engineering thermoplastic uses in aeronautics, for example" o Lockheed F-22: carbon fibre reinforced P E E K and PEI processed by SuperPlastic Diaphragm Forming (SPDF) technique. o Fairchild Dornier 328, a regional transport: carbon fibre reinforced PEI for flap ribs. o Airbus A340-500/600: glass fibre reinforced PPS for 3 m long components, carbon fibre reinforced PPS and honeycomb for inboard lower access panels. o Prototype fuselage panel by Cytec Fiberite: carbon fibre reinforced P E E K and PEI. o National Aerospace Laboratory investigations of the fibre reinforced LCPs. In all these cases, the cost and weight savings are significant. 7.5.7 3D reinforcements compete with 2D 2D reinforced composites have lower performance between the layers of fabrics and other 2D reinforcements. To enhance performances in all the directions, numerous 3D reinforcements have been developed. Several concepts are marketed, such as: 9 Woven 3D fabrics such as 3Weave Z Advantage by3Tex. 9 Stitched glass reinforcements such as Multimat or Multiaxials by Vetrotex. 9 Two glass decklayers bonded together by vertical glass piles such as Parabeam by Parabeam Industrie. 479

Thermosets and Composites

7.5.0 Carbon fibres compete with glass fibres

For many properties carbon fibres have better performances than glass fibres and are also lighter, although more expensive. However, the cost has been decreasing for several years and it is expected that, with their industrial development, this trend will continue. Currently the average price of a finished part incorporating carbon fibres is 50% higher than that of the finished part made with glass fibres, although the carbon fibre price is far higher than that of glass fibre. Zoltek anticipates that a price of ~12/kg could involve the use of carbon fibres in mass production. This is not unrealistic and the replacement of glass fibres in BMCs and SMCs for highly-loaded body components is foreseen. Today ~14/kg appears to be a sustainable prospect and leads to new developments. So: 9 Between 2000 and 3000 General Motors' "Commemorative Edition" Corvettes will be fitted with a carbon fibre reinforced epoxy resin bonnet for the 2004 model. This is the first time that carbon fibre has been used in original equipment for a painted exterior panel on a vehicle produced in North America: The bonnet: o Weighs almost 5 kg less than the glass fibre SMC o Has a similar thickness to stamped sheet metal o Has a Class A surface finish o Withstands the high temperatures of prime and paint ovens o Is fully cured in ten minutes at 150 ~ thanks to a quick-cure epoxy resin. Production combines automated and manual processing techniques. 9 In 2003, DSM launches a carbon fibre reinforced vinylester SMC for semi-structural and structural automotive parts that do not require a Class A surface finish. The SMC flows well and cycle times are similar to those of standard SMC. The specific weight and mechanical properties are significantly better. The compound was developed in cooperation with DaimlerChrysler. 9 Menzolit Fibron have presented (JEC 2003) an automotive body demonstrator made of an advanced SMC reinforced with carbon fibres leading to a weight saving of 60% versus steel with a highquality surface finish. 9 In the wind energy industry, all-carbon constructions are making their entry into the highly-stressed elements of large wind turbine blades, saving half of the weight of glass-reinforced elements and increasing the stiffness. The higher cost of carbon fibres is compensated by the low weight of carbon elements, which leads to a decrease in weight of all the other bearing components of the wind turbine. Glass/carbon hybrid lamination is also being investigated. 480

Future prospects for thermosets and composites

7.5.9 New

highperformancepolymers

Launching new polymers of medium-range performance is a difficult operation economically, as proved by the case of the aliphatic polyketones. New polymer families are rarely marketed but there are some examples where they provide improved thermal performances or, more exactly, a better balance of: 9 Thermal behaviour: with high-performance retention for short periods of high temperature for aeronautics applications such as skins of hypersonic aircraft, and/or long-term performances. 9 Ease of processing. 9 Lower final cost: composites can be less expensive than titanium after processing. Beside the bismaleimides (BMI), polyimides (PI) and cyanate esters are appearing, for example: 9 New polyimides such as PETI 5. 9 Benzocyclobutenes and their derivatives. 9 Polyetheramide resins (PEAR) from bisoxazolines and phenolic novolacs. 9 Phthalonitrile resins. 9 Phenolic triazine (PT). The benzocyclobutenes are already used in electronics but their applications in the structural field are in the course of investigation. Their functionalization would make it possible to reticulate them in a solid state to lead to an increased resistance and a better creep behaviour. They could also be used to modify existing thermoplastics such as polyamides, polyimides or LCP. The functionalization could also be used to initiate a reticulation at high temperature, which could improve the fire behaviour. NASA (NASA TechFinder), within the framework of its research into matrices for composites for the future High Speed Civil Aircraft (HSCT), tried out a panel of 200 oligomers of phenylethynyl with imide terminations (PETI). PETI-5, manufactured using components already available commercially, has excellent properties and a lifespan higher than 60 000 h (6.7 years) at 177 ~ PEAR, high performance polymer resins developed by Ashland, combine strength, chemical resistance, excellent thermal stability, low levels of toxic fumes and smoke when subjected to fire, electrical insulation properties and long fatigue life. Viscosity is low and P E A R accepts high fibre and filler loading. Adhesive characteristics are good compared with other materials. Consequently, P E A R is a candidate for the next generation of aircraft. Phthalonitrile resins were developed by the US Naval Research Laboratory (NRL). The cured resin exhibits good thermal and oxidative stability with useful long-term mechanical properties up to 371 ~ There is no indication of a glass transition up to 500 ~ The low melt viscosity of uncured resin allows it to be used in the RTM process. The low level of 481

Thermosets and Composites

toxic fumes and smoke when subjected to fire qualifies it for use inside submarines. The continuous use temperature is of the order of 300 ~ however, phthalonitrile can be used at much higher temperatures in applications such as missile structures, where the high temperatures exist for only a few minutes. To provide a comparison, high mechanical performance retention is claimed for carbon composites in short duration tests: 9 for epoxy resins at 150 ~ up to 200 ~ 9 for P E A R at 200 ~ up to 370 ~ 9 for BMI at 250 ~ up to 400 ~ 9 for phenolic triazine at 370 ~ up to 500 ~ 9 for phthalonitrile at 400 ~ up to 500 ~ 9 for new polyimides at 400 ~ up to 500 ~

7.6 The immediate future seen through recent patents Recent patents have been analysed by polymer type, reinforcement type, and material structure and process type. The selected patents do not relate to part manufacturing because of the difficulty of eliminating those relating to non-composite uses, for example, the use of melamines for adhesives or the use of glass fibres for insulation. 7.6.1 Analysis of patents by polymer type

The graph in Figure 7.4 positions the main thermosets compared to two frequently used thermoplastics, a commodity (polyethylene) and an engineering thermoplastic (polyamide).

Figure 7.4. Thermoset types: Recent patents for a same period 482

Future prospects for thermosets and composites 7.6.2 Analysis o f patents by reinforcement type

There are many patents concerning fibres but some relate to applications other than polymer reinforcement, for example building insulation. Figure 7.5 shows, for the same period, the recent patents per fibre type. Nanotubes and nanocomposites, particularly carbon nanotubes, are generating intense research activity whereas research is definitely weaker for nanofibres. Figure 7.6 shows, for the same period, the recent patents for the different nanotechnologies. Quartz fibre Boron fibre Silica fibre Aramid fibre Natural fibre Carbon fibre Glass fibre i

|

0

1000

Figure 7.5. Fibre types: Recent patents for a same period

Nanofibres

1 t

Nanocomposites

Nanotubes

I

0

1000

Figure 7.6. Nanoreinforcements: Recent patents 483

Thermosets and Composites

7.6.3 Analysis of patents by structure and process type

The analysis in this case is dubious because structures are confused with reinforcements and processes. For example, patents on films or other multi-layers spoil the laminate analysis. However, the high level of patents concerning nanocomposites and prepregs is obvious. On the other hand, the SMC/BMC patent level appears relatively low. The amount of patents concerning laminates, UD and filament winding seems to correspond to their level of distribution. Figure 7.7 shows recent patents, for the same time period, per composite structure and process. Lay-up Roving LFRP Mat i ,ent winding

II

Pultrusion

m

UD i RTM m SMC/BMC m Sandwich Prepreg Laminate locomposite Composites 0

Figure 7. 7.

500

Structures and processes: Recent patents

7.7 The immediate future seen through recent awards Recent awards from professional organizations, the professional press, engineers associations and so on reflect the most up-to-date technology. Among the numerous award-winning developments, we quote some examples: 9 Wing flap for regional and corporate aircraft (by Radius Engineering) made in carbon composite moulded by RTM. The elements are 3.6 m long and 0.7 wide. 9 Car rear floor of the Renault Megane 2 (by Inoplast) made in light SMC moulded in 1 minute. This concept leads to weight saving in the range of 25-30%, high design freedom and ease of dismantling. 484

Future prospects for thermosets and composites

9 9

9 9 9 9 9

9

9

9

9 9 9

9

Inlet manifold of the new eight-cylinder 7-series by B M W made of reinforced phenolic resin produced by Perstorp. Automotive body demonstrator (by Menzolit Fibron) made of an advanced SMC reinforced with carbon fibres leading to a weight saving of 60% versus steel with a high-quality surface finish. Tanks (by Covessa) capable of withstanding up to 100 bars made by welding three parts in glass fibre reinforced polypropylene (Twintex). Composite grid to replace steel reinforcement of precast concrete panels. Formula 1 shoes for Schumacher made in Nomex and carbon prepreg. The weight saving is 1.2 kg on each foot during 6g decelerations. Giant wind turbines: rotor 80 m in diameter, mast 120 m high. HTPC (Hybrid ThermoPlastic Composite) bumper beams made by Plastic Omnium are used on Pontiac Montana, Chevrolet Venture and Oldsmobile Silhouette by General Motors. Continuous woven fibres are overmoulded with a long or short fibre reinforced polypropylene to save weight (6 kg), enhance impact resistance (2040%) and integrate numerous functions such as reinforcement ribs. The process is fully automated. Rehabilitation of a steel truss bridge using a lightweight fibre reinforced composite deck. The dead load is reduced and the load ratings are doubled, allowing an increase of the maximum permissible weight. The cost saving is of the order of more than ~1 million. Controlled Energy Management Bumper Isolator (by Ford with LDM Technologies and Concept Analysis Corporation) includes a conical geometric design that enhances crash behaviour absorbing more energy in less space than polypropylene foam. Cost, weight, front and rear overhangs are reduced. Structural cargo boxes (by Ford with The Budd Company's Plastics Division) use an SMC instead of steel with a 20% weight reduction, elimination of the risk of the pickup bed rusting, and decrease in the number of pieces. Process to make powertrain throttle bodies with recycled polyamide from carpet (Ford with Visteon and Honeywell). Recycled plastic composite railroad crossties can save millions of trees, significantly reduce plastic landfill waste and cut maintenance costs. A plastic waste processor (by Carderock Division) has been developed to compress the Navy's plastic wastes into disks, solving the environmental and space problems from 600 kg daily plastic waste (20 m 3) per ship. Seaward International Inc and Carderock Division are developing a marine piling (The SeaPile) in structurally reinforced composite with a core made of these disks. Project to print organic transistors on plastic for electronic displays and circuits (by Sarnoff Corporation with DuPont de Nemours and 485

Thermosets and Composites

Company Central Research and Development). The goal is to develop materials, thin flexible plastic substrates, and methods for continuous high-resolution printing. 7.8 Environmental concerns 7.8.1 Recycling of thermosets and composites

From a practical point of view, the recycling of thermosets and composites is difficult and is constrained by: 9 The technical possibilities: the feasibility for handling mass quantities. 9 Economics: the final cost and the recyclate/virgin polymer cost ratio determine the success or failure of the method. 9 Environmental regulations" recycling must globally decrease the pollution balance versus tipping or landfill. 7.8.1.1. Collection and pre-treatment of wastes

The paths differ according to the source of the waste: 9 Manufacturing scrap" it is easy to sort and store them separately in good conditions (clean and dry). These wastes are not subjected to ageing and corrosion. 9 End-of-life products: this case is more difficult to treat. It is necessary to collect the products, to dismantle (if necessary) or to shred them before recycling. These pre-treatments are expensive. These wastes have been subjected for several years to ageing and corrosion and are often polluted. 9 Plastics incorporated into municipal solid wastes: these are burnt without special treatment. Figure 7.8 shows schematically the main paths leading to the recycling step.

I

Processing

I

Sorting

I

II I

Recycling

Collect

II unicipalso,i wastes ]

I

Sorting

I

I

Shredding

I Recycling I I ecycling I Figure 7.8. The waste collect and pretreatment

486

I Collect I Burning

Dismantling

Storage

I

I

Endoflif

Future prospects for thermosets and composites

7.8.1.2. The main recycling routes

The main recycling routes utilize: 9 Chemolysis" certain polymer families such as polyurethane are chemically depolymerized. This is the best recycling solution if the performances of the original material are to be recovered and if the recyclate is used in the same application. This is, technically and economically, a difficult method that is industrialized in few cases. 9 Mechanical recycling: shredding and grinding of polymer scraps allow a partial re-use in the original application but the recyclate level is low because of the decrease in performance. An extension of this principle is obtained by manufacturing other parts of lower performance, sometimes in another industry. 9 Solvent extraction of the polymer from shredder residue is only suitable for thermoplastics. 9 Thermolysis: gasification, pyrolysis.., to produce petrochemical feedstocks for steam-cracking or alternative fuels. 9 Co-combustion with municipal solid wastes. 7.8.1.3. Thermoset and composite specifics

The irreversible formation of a three-dimensional network during the curing of thermosets and the presence of fibres or other reinforcements are additional obstacles for waste recycling because it makes it impossible to: 9 Recover the original chemical state for thermosets. 9 Recover the original size of the reinforcements for all composites. The processing and/or the mechanical treatments involved in recycling break the fibres, foams, honeycombs, etc. 9 Return to the original properties. If we make the assumption that the difficulties of collecting, sorting, and cleaning are solved, some examples of recycling methods are listed below: 9 Polyurethanes can be recycled by: o Hydrolysis: The obtained monomers are identical to the original ones and can be reconverted into virgin polyurethane of the same performance as the original parts. o Glycolysis: The obtained monomers are different from the original ones and can only be used to partly replace virgin components in other types of polyurethanes. The virgin polyurethane obtained is different from the original material but the performances are satisfactory. 9 SMC and BMC can be recycled by mechanical shredding and grinding in three ways: o Micronized powders are added at the 5-15% level in new adapted formulations to replace mineral fillers. The density is slightly inferior and the performances are in a similar range. o Short fibre (few millimetres or less) recyclates used to reinforce polymers or concrete. 487

Thermosets and Composites

Long fibre (10 mm and more) recyclates used to reinforce polymers. 9 The rear leaf springs of utility vans made of continuous glass fibre reinforced epoxy are also recycled by mechanical shredding and grinding in two ways, to give either short fibre (few millimetres or less) or long fibre (10 mm and more) recyclates used to reinforce polymers. 9 The high mineral content of glass fibre reinforced plastics makes them a poor fuel because of the low organic content. However, they can be used in cement kilns where the glass goes into the raw materials and the matrix acts as fuel. 9 Unsaturated polyesters may be hydrolysed by high-temperature (300-500 ~ steam into phthalic acid, styrene, bituminous residue and glass fibres. For a given part, the adopted recycling solutions can belong to several categories of processes. For example, for bumpers out of SMC, six methods compete: 9 Grinding and re-use with virgin SMC. 9 Shredding and re-use of the fibrous recyclate to reinforce other polymers. 9 Shredding and re-use of the fibrous recyclate in the concrete industry. 9 Use in cement kilns. 9 Pyrolysis with production of gas, oils and tars. 9 Hydrolysis. o

7.8.1.4. Thermoset and composite recyclates: mechanical and calorific properties

The recycling treatments and the possible presence of pollution, paints or other surface products cause a reduction in the mechanical properties of recyclates, notably the impact strength and the ultimate characteristics. On the other hand, it is possible to upgrade the recyclate using additives or compatibilizing surface treatments. Table 7.3 (after figures from Owens Corning, N R C of Italy) shows the retention of certain properties versus the number of recycling cycles. Table 7.3 Processing and end-of-life scraps of glass reinforced polypropylene: property retention versus the number of recycling cycles

Retention, % Tensile strength Number of recycling cycles

488

Tensile modulus

Notched impact

Fibre length

Glassfibre reinforcedpolypropylene: Processingscraps

0

100

100

100

100

1

87

95

78

91

2

79

90

72

84

4

65

79

58

75

Future prospects for thermosets and composites Table 7.3 Processing and end-of-life scraps of glass reinforced polypropylene: property retention versus the number of recycling cycles

Retention, % Tensile

Bumpers

strength

Tensile modulus

Notched impact

Fibre length

Recycled end-of-life (10 years old) bumpers made of glassfibre reinforcedpolypropylene

New

100

100

100

Old

94

90

29

Recycled old

82

87

20

Recycled and upgraded old

91

90

74

For a high-performance glass fibre reinforced thermoplastic such as PEEK, the retention of modulus and strengths after two and four recycling cycles are in the ranges of 79-87 % and 76-84 %, respectively. Table 7.4 (after figures from Menzolit, SMC and Valcor) displays the effect of use of SMC/BMC recyclates on the properties of virgin SMC/ BMC or polypropylene. Table 7.4

Property retention (%) of BMC/SMC and polypropylene versus the level of BMC recyclate

Effect of BMC/SMC recyclate on

new BMCs and

SMCs

Recyclate, %

Tensile strength

Tensilemodulus

Notched impact

0

100

100

100

10

103

87-100

110-136

15

77-82

82-87

83-108

Effect of BMC/SMC recyclate on polypropylene compounds Neat

100

5% dough moulding compound (DMC) recyclate

100

100

69

150

31

5% glass fabric reinforced phenolic recyclate

109

290

61

24% surface treated DMC recyclate

109

172

31

24% surface treated glass fabric phenolic recyclate

235

283

96

Table 7.5 (after Neste) displays some calorific properties of plastic wastes compared to coal. The laminates and sandwich composites are handicapped by the low heat value and carbon content. Moreover, the laminates have a high ash content. Table 7.5

Comparison of the calorific properties of coal and plastic waste fuels

Coal

Polyethylene

Mixed plastics

Laminate

Sandwich

LHV (Low Heat Value)

25

40

32

17

19

Carbon

64

81

65

39

52

Ash

16

3

18

43

21 489

Thermosets and Composites

7.8.1.5. Recycling costs

In the most unfavourable case, the cost of recycling is a combination of the operations of collecting, dismantling, sorting, treatment and recycling. From an economic point of view, the cost assessment of the recyclate depends primarily on the price retained for the waste. The recycling cost is in the range of: . 4g0 per kg for a recyclate of processing scrap whose grinding cost balances the cost it would have been necessary to pay to eliminate it, 9 to more than ~gl.3 per kg if one has to take into account the combined costs of collecting, dismantling, sorting, grinding and recycling treatment. To decrease the dismantling and sorting costs of plastic parts it is necessary to anticipate these steps at the design stage: ,, To consider methods of assembly to make dismantling easier, 9 To standardize the plastics used. The monomaterial concept is attractive but is sometimes unrealistic for technical and economical reasons. As examples: 9 For a certain part with volumes of 3000 t/year, it was shown that the economic equilibrium was between 4g0.6 and 4g0.7 per kg for the recyclate. 9 For various methods and end-of-life products, the claimed costs vary in the range of @0.5 to 491 per kg. 9 For the solvent process, W i e t e c k - a commercial operator of a 4000 t f a c i l i t y - estimates that the process is economically viable for a polymer price exceeding ~gl per kg. 7.8.2 Sustainable standard and high-performance reinforcements

Natural reinforcements have been used for a very long time. 9 Wood flour was one of the first fillers used with phenolic resin. 9 Wood shavings are used in wood particleboards. 9 Short cotton and other cellulose fibres are commonly used in phenolic and melamine resins. The renewed interest in natural reinforcements may continue because: 9 Ecology is a sustainable policy. . The growing plastic consumption uses more and more glass fibres that the natural fibres can partly replace in general purpose composites. 9 Other industries processing natural fibres, such as the paper or flax industries, are seeking outlets for their by-products. 9 Natural fibres can bring specific properties. For example, a fibre developed by Impact Composite Technology absorbs the styrene in unsaturated polyester processing. 9 The development of new processing methods opens new applications such as the extrusion of "wood". 9 Biosynthesis allows production of high-tech reinforcements such as BioSteel. 490

Future prospects for thermosets and composites

Natural fibres were considered in sections 2.13 and 6.5 above, and we will only examine two prospective aspects of sustainable reinforcements here. "Extruded (or injected) wood": unlike the well-known phenolic resins reinforced with a low level of wood flour, "extruded or injected wood" is composed of a majority of cellulose (60% up to 90%, or even 95 %) and a small amount of polymer as binder. This binder can be synthetic or partially to totally natural. The US natural fibre and wood composite market was estimated at 340 000 tons in 2001 growing to just over 450 000 t in 2003, that is, roughly 1% of the total plastic consumption. According to Plastics Additives & Compounding, the market is predicted to grow to 635 000 t in 2006 or a 12% annual growth rate - dramatically higher than the average annual growth of plastics. Europe is not such an important market as the U S A because of the lack of available wood by-products and the lack of end-uses. Table 7.6 displays some properties of different "extruded or injected woods" compared to PVC. The value ranges are broad according to the various marketed techniques. As example, for an extruded wood grade with PVC binder a cost of 4E1 per kg is claimed. Table 7.6

Examples of properties of "extruded or injected woods" compared to PVC PVC

Density, g/cm 3

Extruded or injected wood

1.4

1.2-1.4

1.3-1.4

Tensile strength, MPa

35-50

17-25

10-22

26-38

Tensile modulus, GPa

2.4-4

4-8

1-5

1.9-2.2

Flexural strength, MPa

0.96-1

30-50

58-69

Flexural modulus, GPa

2.1-3.5

4-6

3

Elongation at break, %

2-30

0.5-1

0.3-0.7

3-7

25

Charpy impact strength, kJ/m 2 Izod notched impact, J/m

20-110

24-57

BioSteel high-performance fibres: Nexia Biotechnology develops and produces these fibres made out of silk proteins secreted by transgenic goats. 25 % lighter than Kevlar, the failure energy would be much higher. The targeted applications are: 9 Medical devices 9 Industrial or sports ropes, fishing lines and nets 9 Polymer reinforcement for ballistic protection such as soft body armour, competing with Kevlar fibres. 7.8.3 Sustainable and biodegradable components for matrices

Like the synthetic polymers, natural and biodegradable matrices are principally thermoplastics, such as the following examples: 491

Thermosets and Composites

9 Polylactic acid (PLA) 9 Polyglycolic acid (PGA) 9 Polycaprolactone (PCL) 9 Polyhydroxyalkanoate (PHA) 9 Polyhydroxybutyrate (PHB) 9 Starch and other natural derivates of uncertain formula. These thermoplastics can be processed in nanocomposites and fibre reinforced composites. For thermosets there are developmental or industrial examples driven by automotive and combine harvester manufacturers (John Deere, Ford, etc.) such as: 9 RIM polyurethane components derived from starch, vegetable oils, soya, etc. 9 SMC polyester with 25% corn and soy-derived materials 9 Bicomponent casting resins derived from sugar, colza, starch, castoroil, etc. 7.8.4 Examples of sustainable composites

Here we outline just a few examples of sustainable composites: 9 Polylactic acid (PLA) reinforced with kenaf fibres developed by NEC for personal computer housings. With a 20% level of kenaf fibres, the main properties compete with glass fibre reinforced ABS but the cost is 50% higher. The flexural modulus is over 4.5 GPa and the H D T reaches 120 ~ 9 PLA/montmorillonite nanocomposites with a better heat resistance, a doubled modulus and an easier processing than the neat PLA. 9 VTT, a Finnish research centre, is developing fully biodegradable composites based on PLA reinforced with flax and other natural fibres. These composites can be used indoors in a dry environment. Outdoors there is a risk of degradation but this is sometimes an advantage, such as for agricultural products; using biodegradable composites reduces disposal costs. The tensile strengths are in the range of 70-80 MPa for a 40% by weight level of flax fibres.

References Technical guides, newsletters, websites

Borealis, Business Wire, Menzolit, NASA, Naval Research Laboratory, Neste, PRW, Owens Corning, SMC, Valcor, Zoltek. Reviews [1] Plastics Additives & Compounding (Elsevier Science) [2] PRW Newsletter (PRW.com & European Plastics News) [3] Reinforced Plastics (Elsevier Science) [4] Techniwatch (CRIF) Papers Zoltek, User's Guide for Short Carbon Fiber Composites, (June 2000), Zoltek Companies Inc, St Louis MO 63044, USA, www.zoltek.com 492

Conclusion

Today, plastics are an industrial and economic reality competing with traditional materials and in particular metals, of which steel is the most important. Roughly 150 million tons of plastics are consumed annually, which is: 9 Intermediate between those of steel and aluminium in weight, that is, roughly a sixth of the consumption of steel and six times the consumption of aluminium for recent years. 9 Higher than those of steel and aluminium in terms of volume in recent years: roughly 1.4 times the consumption of steel and 16 times that of aluminium. 9 Lower than those of steel and aluminium if we reason in terms of equal rigidity: equivalent to roughly 1% of the consumption of steel and half that of aluminium. The growth of plastics is significantly higher than that of steel. No engineer or designer can be ignorant of plastics, but the decision to use a new material is difficult and important. It has both technical and economical consequences. It is essential to consider: 9 The actual penetration of the material category in the industrial area 9 The functionalities of the device to be designed 9 The characteristics of the competing materials 9 The abundance or scarcity of the material and the process targeted 9 The cost 9 The processing possibilities 9 The environmental constraints. The intrinsic mechanical properties of plastics and composites are different from those of conventional materials. 9 Expressed in the same units, the hardnesses of engineering materials cover a vast range broader than 1 to 100. Plastics are at the bottom end of the range but are of a wide diversity and offer decisive advantages compared to metals, glass, ceramics, wood and others. 9 The properties of unidirectional composites in the fibre direction can compete with those of current metals and alloys. The highest

Thermosets and Composites

performance engineering plastics compete with magnesium and aluminium alloys. . Polymers are electrical and thermal insulators but have high coefficients of thermal expansion. 9 Polymers are not sensitive to rust but are sensitive to thermooxidation and, for some, to moisture degradation. 9 Polymers present a more or less plastic behaviour under stresses, leading to lower modulus and ultimate strength retentions, and higher long-term creep or relaxation when the temperatures rise. Thermosets, because of the crosslinking, cannot melt but decompose without melting as the temperature increases. . Many polymers, including the commodities, are resistant to the chemicals usually met in industry or at home and displace the metals previously used for applications such as domestic implements, gas and water pipes, factory chimneys, containers for acids and other chemicals. To compensate for their handicaps in terms of properties compared to traditional materials, polymers have effective weapons" 9 Design freedom. 9 Manufacturing in small quantities or large series of parts of all shapes and all sizes, integrating multiple functions, which is unfeasible with metals or wood. . Possibility of selective reinforcement in the stress direction. 9 Weight savings, lightening of the structures, miniaturization. 9 Reduction of the costs of finishing, construction, assembling and handling. . Ease and reduction of maintenance operations. . Damping properties. . Aesthetics, the possibilities of bulk colouring or in-mould decoration to take the appearance of wood, metal or stone, which avoids or reduces the finishing operations. 9 Durability, absence of rust and corrosion (but beware of ageing). 9 Transparency, insulation and other properties inaccessible for metals. Plastics and polymer composites are much more expensive than metals, even more specialized ones such as nickel. As for the specific mechanical properties, the high densities of metals modify the classification of the various materials. According to the cost per volume, plastics are competitive. Only the very high performance plastics or composites are more expensive than metals.

494

Conclusion

The links created between the chains of the thermosets limit their mobility and possibilities of relative displacement and bring certain advantages and disadvantages: 9 Infusibility, barrier effects. 9 Better modulus retention when the temperature rises. 9 Better general creep behaviour. 9 Simplicity of the tools and processing for some materials manually worked or processed in the liquid state. 9 Slower processing cycles. 9 More difficult monitoring of certain processes. 9 More difficult recycling. 9 Impossible to weld. The main advantages of polymer composites are: 9 High mechanical properties. 9 The possibility of laying out the reinforcements to obtain the best properties in the direction of the highest stresses. 9 The possibilities of repair: a significant advantage of composites. The development of composites is hindered by the difficulties in recycling, attenuated in the case of the thermoplastic matrices. The hybrid materials are often a good solution to take advantage of plastics and one or several other conventional materials. This principle, in more or less complex versions, is applied to the front-ends of recent cars, footbrake pedals, aircraft wheels, car doors, etc. The final choice of the design team may result from many iterations concerning the functional properties, the environmental constraints, the possibilities to produce the part in the required quantities and the price. The price considered may just be the part cost but can also include assembling, delivery, set up and end of life costs, taking account of durability, the savings in maintenance, etc. The future of plastics is promising thanks to the research and development efforts with significant new patents. The goals for future development are diverse" 9 Improvement of the cost/performance ratios. 9 Improvement of the immediate and long-term characteristics, to conquer structural parts. 9 Better thermal resistance. 9 Better weathering behaviour. 9 Enhancement of the colouring and surface aspect. 9 Improvement of the surface properties. 495

Thermosets and Composites

Adaptability of the grades, which must satisfy the requirements of the market and develop specific properties and better combinations of properties. 9 Halogen-free fire retardant grades. 9 Improvement of the adherence of paints, printing inks, adhesives. 9 Better performance, particularly impact resistances, at low temperature. 9 Improved ease of processing. 9 Improvement of the mould productivity. 9 Automation of the process equipment. 9 Better control of the processes by SPC. 9 Development of new manufacturing methods. On-line compounding to reduce costs and thermal degradation. 9 Hybrid associations with non-plastic materials. 9 Use of wastes and recycled materials to satisfy the environmental requirements and lower the costs. 9 Management of recycling, starting with the design 9

All the developmental routes are being investigated: 9 New materials are being introduced, including: - new polymers. For example, Dow is starting to market cyclic resins developed by Cyclics Corp. and new reinforcements ranging from the more-or-less conventional to the highly sophisticated, such as carbon nanotubes. 9 Evolution of processing: globalization, automation, industrialization, simplification, low-cost tools. 9 Popularization of high-performance products such as carbon fibres and 3D reinforcements to compete with their 2D counterparts. 9 Sustainable standard and high-performance reinforcements, sustainable and biodegradable components for matrices, sustainable composites. 9 New combinations of known products or techniques such as the low weight reinforced thermoplastics (LWRT). -

The above comments are only a superficial overview of the immense possibilities of these young polymer materials that could be 'The Materials of the 21st Century'.

496

Index

A

C

accelerated ageing 148, 160 adaptability 467 additive costs 52 adhesive bonding 340, 441 aeronautics 109, 113, 119, 128, 121,133, 135, 137, 227, 253,277, 301,318 aerospace applications 77 ageing 189, 213, 230,243,259,282,305,320 agricultural equipment 122 airex r82 397 aluminium honeycombs 400 amino resins: melamine (MF) 239 analysis of patents 482-484 anti-abrasion 84 anti-corrosion 82, 84, 101,122, 207 equipment 84 anti-wear 108, 253 aramid fibres (AF) 128, 381 aramid honeycombs 399 arc resistance 154 armaments 76, 128, 130, 137, 253, 277,290 art 90, 120, 208 assembly 441 costs 61 ASTM D257 153 automated lay-up 429 automotive 63, 95, 111,114, 131,136, 205,226, 254, 277, 323 industry 63 awards 484

calorific properties 488 carbon fibres (CF) 129, 379, 483 hybrids 387 carbon nanotubes (CNT) 476 cases 87 casting 336, 420 centrifugal moulding 143, 4301 chemical 190,214,230,244,260,284,306,325,327 behaviour 162 resistance 152 clamping 341 Clash & Berg test 149 co-moulding 436 coating application 95, 187 coefficient 13349 cold compression moulding 424 collection of wastes 486 comfort 70 composite 49, 81, 68, 81 characteristics 443 insert moulding 436 matrices 350 mechanical performances 346 processing 25,359, 413 properties 370, 389 compounding integrated 475 compression 435 moulding 331,419 properties 156 set 161,189 transfer moulding 332, 425 conductive composites 462 consumption trends 48, 472 continuous sheet moulding 144 continuous stratification 433 continuous use temperature (CUT) 146 Core-Cell 395 corrosivity 306 cost 185,205,226,252, 276, 299,317,358,360, 362, 365 per volume of various materials 13 per weight of various materials 12 savings 372, 473 creep 151,161, 189, 212, 230, 257, 281,320 compression set 304

B basic principles 344, 443 bedding 74 biodegradable components for matrices 491 BMC 138, 404 body 65, 85, 87 boron fibre hybrids 387 brittle point 148 building and civil engineering 70, 92, 98,105,118, 136, 139, 206, 227, 300 building furniture 111,254 bulk moulding compounds (BMC) 407

Thermosets and Composites

crystallization 160 test 149 cyanate esters (Cy) 120, 317

D damping 65, 70, 85 decoration 90, 120, 208, 215,233,344 dicyclopentadiene (DCPD) 121,322 dielectric strength 153 dimensional stability 213,230, 243,259, 282, 305, 320, 325 dough moulding compound (DMC) 408 durability 10 dynamic fatigue 189, 213, 230, 259, 282, 305,320 dynamic mechanical properties 161

E earth-moving equipment 122 economic requirements 21 ecycling of polymers 29 effect of short glass fibre 376 effect of the fibre level 445 effect of the fibre nature 445 elastic modulus 150 elastomer application 94 187 electric household appliances 88, 105, 118, 300 electrical properties 153, 163, 193,215, 232, 245, 265,289, 309, 320, 325 electricity 86, 94, 104, 106, 115,207,227,241,253, 277,318,324 electronics 86, 94,100,110,121,127,207,253,277, 318,324 environmental concerns 486 environmental constraints 29 environmental requirements 22 environmental stress cracking (ESC) 153 epoxide resins 108 epoxides 251 epoxies 352 epoxy resins (EP) 251 european market 44 external elements 65 extrusion 335,436, 437

F fatigue 152, 161 fibre 241,370 composites 450 filament 437 winding 142, 429 filled resin 420 finishing operations 439 fire resistance 193, 215,232, 244, 265,289, 309, 320, 324 flammability 154, 163 flexible foams 195, 289, 309 flexural properties 156 fluid contact behaviour 162 fluoroplastics 363 fluorosilicones (FMQ, FVMQ or FSI) 297 498

foaom 193,233,245 application 92, 186 foamed composites 458 foamed epoxies 265 foamed matrix composites 459 foamed polyimides 289 foamed silicones 309 formworks 85, 87 frames of machines 85 friction 212, 230, 243, 257, 280, 304, 320, 325 furan 326 furane resins 122 furniture 74, 92, 94, 101,126, 135, 141,207

G garden equipment 122 gardening equipment 324 gas permeability 154, 162 gehman test 149 glass fabric 349 glass fibre plastics 376 glass fibres 123,373, 480 glass mat thermoplastics (GMTs) 409 global plastics industry 32 glue and adhesives 112, 255 GMT sheets 434 guarantee 467

H hand lay-up 140, 415,417, 418 HDT 160 health 112, 254, 119, 301 heat behaviour 327 heat deflection temperature (HDT) 147 high-energy radiation 260, 284, 320 high-performance reinforcements 490 high-pressure injection moulding 426 honeycombs 399 hot compression moulding 424 household appliances 107, 227,241 housing equipment 324 humidity 162 hybrid 16 135, 474 composites 461 materials 19 processing 28

IEC 93 153 immersion 152 impact test 150, 159 importance of the various processing modes 42 industrial fibres 388 industry 92, 94, 107, 115, 122, 241 infusion process 422 initial behaviour 209, 228,242, 255,278, 302, 318, 324, injection 420, 435 moulding 334

Index

insulation 85, 87 integral skin foams 194 interlaminar properties 158 interlaminar shear strength (ILSS) 150 intermediate semi-manufactured composites 411 materials 404 intrinsic mechanical properties 4 ISO standards 155, 196, 233, 246, 310, 380, 370, 373,377

method for strength estimation 348 mineral fibres 387 molecular reinforcement 477 moulding of test specimens 155 MQ 138

N nanocomposites 444 nanofillers 402, 477 nautical sports 81 new high performance polymers 481 new processes 475 north american market 47

L laminates 227 law of mixtures 349 leisure 94, 95,112, 254, 324 leisure parks 208 LFRT 449 light resistance 162 lighting 70 liquid crystal polymers 365 liquid injection moulding (LIM) 336 liquid thermoset processing 336 loading direction 348 long fibre reinforced plastics 449 long-term behaviour 209, 228, 243,255,279, 303, 319,324 long-term light 152 long-term mechanical properties 151 long-term properties 160 low temperature 160 behaviour 148, 210, 243,257, 280, 304, 319, 324, 475 low-cost tool 475

M machining 440 main composite families 91 "~ain processing methods 136 malP., recycling routes 487 main reinforcements 123 main thermoget- families 91 maintenance costs 61, 62 marketing requirements 22 market 472 shares 34, 36, 38 material costs 12, 473 selection 164 upgrading and competition 476 mechanical assembly 341,441 mechanical elements 67 mechanical industry 118, 300 mechanical properties 4, 149, 155, 189, 211,229, 243, 257, 280, 304, 319, 325, 327, 488 mechanics 126, 141 melamine 105,234 metal consumption 2 metallization 440

O office automation 88, 114, 120, 277, 302 offshore 81 operating cost 21,467 optical properties 155,164,189,211,229,243,257, 280, 304 optoelectronics 118, 300 outdoor furniture 75 overbraiding 432 oxygen index 154, 163

P packaging 90, 95, 107, 122, 208, 241,324 passenger compartment: 67 patents 482 PBO fibres 388 phenolic resins (PF) 103, 223,254, 351,434 phenylene polysulfide 362 plastic 20 consumption 2 costs 50 properties 146 plywood 227, 400 PMQ 138 polution 29 polyacetal (POM) 361 polyacrylics (PMMA) 361 polyamide 360, 365 polycarbonate 362 polycyanates 120, 317, 354 polyetheretherketone 364 polyetherimide 365,397 polyethersulfone foams 397 polyethylene (PE) 358 fibres 388 foams 394 polyimides (PI) 113, 275, 353 polymer composites 18,477 polymethacrylimide 396 polyphenylene ether (PPE) 362 polyphenylene oxide (PPO) 362 polypropylene (PP) 358 foams 394 polysiloxanes 138 polystyrene 359 foams 393 499

Thermosets and Composites

polysulfone 364 polyurea 91, 95, 187 polyurethane 91,184, 354 foams 392 polyvinyl chloride (PVC) 358 polyureas (PUR) 184 powder moulding compounds 216 pre-treatment of wastes 486 precision of the moulded parts 165 premix 408 prepreg applications 143 prepreg draping 427, 437 press fitting 341 primary processes 25 processing costs 54, 474 property of RRIM, SRRIM 458 protection properties 108, 253 PTFE fibres 388 publicity 208 pullwinding 432 pultrusion 141,431,437 PVMQ 138

R raw material 196, 216, 233, 266 costs 51 reaction injection moulding (rim) 337 reaction of reinforced resin 420 recycling 486 recycling costs 490 reduction factor 348 reduction of production costs 467 refrigeration 88 reinforcement 346, 347,348, 370 costs 53 form 348 relaxation 151,161 repairing composites 442 requirements of the market 466, 473 RFI 422 RIFT 422 rigid foams 195 rigid PVC foams 391 RIM application 93, 186 riveting 341 rohacel1396 rotational moulding 338 RRIM 420, 458 RTM 139, 423 S safety 83 sandwich composites 133, 437, 457 sandwich properties 401 sandwich technology 390 screwing 341 SCRIMP 422 sealing application 85, 95, 187 secondary processing 25, 27 self-reinforced polymers 133, 412 500

semi-rigid foams 195 shear properties 157 Sheet Moulding Compound (SMC) 405 shipbuilding 93, 100, 112, 122, 135,140, 207,254 short aramid fibres 448 short carbon fibres 447 short fibre composites 445 short glass fibres 446 SI 138 significant parameters 445 silicones 116, 355, 138 sliding 84 SMC 138 smoke generation 163 smoke opacity 155 snap-fit 341 solid thermoset processing 330 some weaknesses of the polymer materials 22 soundproofing 70, 107,241 space 76, 133, 135, 290 specific mechanical properties 7 sports 89, 93, 94, 95, 112, 254, 324 spray lay-up 140, 341,416, 417 spring work 341 SRRIM 420, 458 stainless steel fibres 387 street furniture 75 stress and strain at yield 150 structural applications 86 structural foamed epoxies 265 structural foamed polyurethane 195 structural parts 65 structure of the plastic processing industry 49 styrene-acrylonitrile foam 395 surface finishing and painting 439 surface resistivity 153 survey of main markets 63 sustainable components for matrices 491 sustainable composites 492 sustainable natural fibres 132, 385 sustainable standard 490 syntactic foams 266, 290, 310, 318, 320. 398, 460 T tape winding 437 technLal requirements 21 tensile properties 155 tension set 161 textile fibres 387 the fibre lengths 349 thermal and electrical properties 8 thermal behaviour 146, 187, 209, 228, 242, 255, 278, 302, 318, 324 thermomechanical properties 160 thermoplastic 357 composites 136, 434 matrix properties 365 polyesters 360 thermoset 16, 48, 322, 350 assembly 340

Index

composites 166, 414, 488 machining 339 matrix properties 356 processing 23 torsion properties 158 toxicity 29 trade name 197,217,235,247,267, 290, 310, 321, 325,327, 378, 381,383 transmission system 86 transport 63, 95,102, 104, 107, 120, 123,134, 137, 140, 208, 226, 241,302

V

U

W

UL temperature index 147 UL94 ratings 154 ultimate stress and strain 150 under-the-hood compartment 67 unidirectional reinforcement 347 unsaturated polyester 349 unsaturated polyesters (UP) 95,203, 350 urea-formaldehyde (UF) 239 urea-formaldehyde resins (amino resins) 105 UV resistance 152

water sports 100, 112, 207, 254 weathering 189, 213,230, 243,283,306 weight reduction 82 whiskers 387 wire and cable insulation 87 wood 400

VacFlo 423 vacuum bag moulding 417, 422 vacuum impregnation moulding 422 vacuum outgassing 289, 3200 vacuum technology 116, 278 vapour permeability 162 VARI 423 VARTM 422 vicat softening temperature 148, 160 VMQ 138 volume resistivity 153

Y yield point 150

Z ZMC 138

501