Flame Retardants for Plastics

Market Report





by

Peter Dufton

Flame Retardants for Plastics Market Report

by

Dr. Peter W. Dufton

July 2003

Rapra Technology Limited Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK Tel: +44 (0)1939 250383 Fax: +44 (0)1939 251118 http://www.rapra.net

The right of P.W. Dufton to be identified as the author of this work has been asserted by him in accordance with Sections 77 and 78 of the Copyright, Designs and Patents Act 1988.

© 2003, Rapra Technology Limited ISBN: 1-85957-385-1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means—electronic, mechanical, photocopying, recording or otherwise—without the prior permission of the publisher, Rapra Technology Limited, Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK.

Typeset, printed and bound by Rapra Technology Limited. Cover printed by LG Davis Design and Print Solutions, Birmingham.

Contents 1 Introduction.................................................................................................................................... 1

1.1 Background .............................................................................................................................. 1 1.2 The Report................................................................................................................................ 1 1.3 Methodology ............................................................................................................................ 2 2 Summary and Conclusions .......................................................................................................... 3

2.1 Materials................................................................................................................................... 3 2.2 End User Sectors ...................................................................................................................... 5 2.2.1 Automotive........................................................................................................................ 6 2.2.2 Electrical Appliances......................................................................................................... 6 2.2.3 Business Machines and Consumer Electronics ................................................................. 6 2.2.4 Building and Construction................................................................................................. 7 2.2.5 Furniture ............................................................................................................................ 7 2.2.6 Trends................................................................................................................................ 7 2.3 General ..................................................................................................................................... 7 2.3.1 Testing and Environmental Factors................................................................................... 7 2.3.2 Overview ........................................................................................................................... 8 3 Flame Retardants ........................................................................................................................ 11

3.1 General ................................................................................................................................... 11 3.2 Organic Halogen Compounds ................................................................................................ 12 3.3 Phosphorus Compounds......................................................................................................... 12 3.4 Antimony Trioxide................................................................................................................. 13 3.5 Alumina Trihydrate ................................................................................................................ 14 3.6 Magnesium Hydroxide........................................................................................................... 14 3.7 Zinc Borate............................................................................................................................. 15 3.8 Intumescent Materials ............................................................................................................ 15 4 Products and their Markets ........................................................................................................ 17

4.1 Organic Halogen Containing Materials.................................................................................. 17 4.1.1 Bromine Compounds....................................................................................................... 17 4.1.1.1 Dead Sea Bromine Group......................................................................................... 17 4.1.1.2 Great Lakes .............................................................................................................. 21 4.1.1.3 Albermarle................................................................................................................ 22 4.1.1.4 Ferro Corporation..................................................................................................... 24 4.1.1.5 Unitex Chemical Corporation .................................................................................. 24 4.1.2 Chlorine Compounds....................................................................................................... 24 4.2 Phosphorus Containing Compounds ...................................................................................... 25 4.2.1 Introduction ..................................................................................................................... 25 4.2.2 Polymer Modification...................................................................................................... 25 4.2.3 Red Phosphorus............................................................................................................... 25 4.2.4 Ammonium Polyphosphate ............................................................................................. 27 4.2.5 Phosphorus Oxynitride .................................................................................................... 27 4.2.6 Albermarle Corporation .................................................................................................. 27 4.2.7 Polymer Tailoring ........................................................................................................... 28 4.2.8 Akzo Nobel Chemicals.................................................................................................... 28 4.2.9 Great Lakes Chemical Corporation................................................................................. 28 4.2.10 Clariant .......................................................................................................................... 29 4.2.11 Other New Developments ............................................................................................. 30 4.3 Inorganic Minerals and Compounds ...................................................................................... 30 4.3.1 Antimony Trioxide.......................................................................................................... 30 4.3.2 Alumina Trihydrate (ATH) ............................................................................................. 31 4.3.3 Boron Compounds........................................................................................................... 32 4.3.4 Magnesium Hydroxide .................................................................................................... 35 4.3.4.1 Technology............................................................................................................... 35

4.3.4.2 Commercial Products ............................................................................................... 38 4.3.5 Other Inorganic Compounds ........................................................................................... 38 4.3.5.1 Iron Compounds ....................................................................................................... 38 4.3.5.2 Molybdenum Compounds ........................................................................................ 39 4.3.5.3 Tin Compounds ........................................................................................................ 40 4.3.5.4 Talc........................................................................................................................... 41 4.4 Other Materials....................................................................................................................... 41 4.4.1 Coatings........................................................................................................................... 41 4.4.2 Char Forming Polymers .................................................................................................. 42 4.4.3 Potassium Compounds .................................................................................................... 43 4.4.4 Melamine Compounds..................................................................................................... 43 4.4.4.1 Melamine Polyphosphate ......................................................................................... 43 4.4.4.2 Melamine Cyanurate (MC)....................................................................................... 44 4.4.5 Silicon Compounds ......................................................................................................... 45 4.4.6 Graphite ........................................................................................................................... 45 4.4.7 Glass Flake ...................................................................................................................... 47 4.4.8 Low Melting Glasses....................................................................................................... 47 4.4.9 Polymer Blends ............................................................................................................... 47 4.4.10 PTFE.............................................................................................................................. 48 4.4.11 Aluminium Flake........................................................................................................... 48 4.4.12 Hindered Amine Light Stabilisers ................................................................................. 48 4.4.13 Nanocomposites ............................................................................................................ 49 4.4.14 TSWB............................................................................................................................ 51 4.4.15 Noflan............................................................................................................................ 51 5 Polymer Families and Their Flame Retardancy........................................................................ 53

5.1 Polyolefins.............................................................................................................................. 53 5.1.1 Polyethylene .................................................................................................................... 53 5.1.2 EVA................................................................................................................................. 54 5.1.3 Polypropylene.................................................................................................................. 56 5.2 PVC ........................................................................................................................................ 57 5.3 Styrenics ................................................................................................................................. 59 5.4 Polyamides ............................................................................................................................. 60 5.5 Modified PPO (m-PPO) ......................................................................................................... 62 5.6 Polyurethanes ......................................................................................................................... 63 5.7 Thermosets ............................................................................................................................. 66 5.7.1 Unsaturated Polyesters .................................................................................................... 67 5.7.2 Epoxy Resins................................................................................................................... 69 5.7.3 Phenolics ......................................................................................................................... 71 5.7.4 PU Casting Systems ........................................................................................................ 71 5.7.5 Acrylic Resins ................................................................................................................. 71 5.7.6 Dicyclopentadiene ........................................................................................................... 72 5.8 Thermoplastic Polyesters ....................................................................................................... 72 5.9 Polycarbonates........................................................................................................................ 74 5.10 Other Thermoplastics ........................................................................................................... 75 6 Suppliers and the Consumption of FR Additives and Compounds....................................... 77

6.1 General Comments ................................................................................................................. 77 6.2 Suppliers................................................................................................................................. 78 6.2.1 Brominated Flame Retardants ......................................................................................... 79 6.2.2 Melamine......................................................................................................................... 80 6.2.3 Phosphorus Flame Retardants ......................................................................................... 80 6.2.4 Mineral Filler Flame Retardants...................................................................................... 81 6.2.5 Borate Flame Retardants ................................................................................................. 82 6.2.6 General ............................................................................................................................ 82 6.3 Consumption and Market Data............................................................................................... 82 6.4 Compounding for Flame Retardancy ..................................................................................... 87

7 End-User Market Sectors............................................................................................................ 89

7.1 Automotive............................................................................................................................. 89 7.2 Other Transport ...................................................................................................................... 90 7.3 Electrical Components ........................................................................................................... 91 7.4 Electronics Products............................................................................................................... 93 7.4.1 Telecommunications ....................................................................................................... 96 7.4.2 Consumer, Brown Goods ................................................................................................ 97 7.5 Electrical Cables..................................................................................................................... 98 7.6 Building and Construction ................................................................................................... 101 7.7 Upholstered Furniture and Textiles...................................................................................... 103 8 Fire Testing ................................................................................................................................ 105

8.1 Introduction .......................................................................................................................... 105 8.2 Specific Tests ....................................................................................................................... 105 8.3 Comparing Test Results ....................................................................................................... 107 8.4 Tests for Building Materials................................................................................................. 109 8.5 Cable Testing........................................................................................................................ 111 8.6 Mattress Tests....................................................................................................................... 111 8.7 Clothing Tests ...................................................................................................................... 112 9 Environmental and Regulatory Matters .................................................................................. 113

9.1 Fire Safety ............................................................................................................................ 113 9.1.1 European Standards for Television Sets........................................................................ 114 9.1.2 Brominated Flame Retardants ....................................................................................... 116 9.2 Brominated Flame Retardants .............................................................................................. 118 9.3 EU Directives ....................................................................................................................... 122 9.4 Recycling Matters ................................................................................................................ 124 9.5 Postscript .............................................................................................................................. 128 European Suppliers of Flame Retardants – Company Names and Addresses ..................... 133

Abbreviations and Acronyms..................................................................................................... 145

Flame Retardants for Plastics Market Report

1 Introduction 1.1 Background Flame retardant plastics play an important role in our society. They are used in cases where there is a requirement to protect people and property from a possible fire hazard. Together with other decisive fire prevention measures, such as structural design and the use of smoke detectors, the choice of materials is one of the basic decisions to be taken by developers and manufacturers of plastic parts. Attempts have been made over the years to harmonise the standards for flame retardant systems and to produce environmentally friendly products. These days all products must satisfy application-specific demands on preventative fire protection. Such demands are best fulfilled technically and economically by the use of flame retardants. These help to limit flame spread and heat release in incipient fires and frequently to prevent fires from starting in the first place. The appropriate type of flame retardant material is determined not only by the required flame resistance standard and the physical dimensions for the particular application but also by the family of polymers used. Countless applications require that the polymers used must exhibit ever higher levels of fire safety. The construction industry is a key one whereby all industrialised countries have their own complex system of fire tests and fire classifications. This is the main reason that building products still have to be tested and approved in each and every one. Since the early nineties, ‘Green’ parties in Germany and in several Scandinavian countries have invested considerable effort to try to ban halogenated flame-retardants, claiming that they may be a source of toxic halogenated dibenzodioxins and dibenzofurans. The spreading of many rumours and actions to introduce restrictions on brominated flame retardants have resulted in a major decrease in the use of flame retarded TV housings in the European market. As a consequence of several years of such practice, TVs have become the primary cause of domestic fires in Germany while in Sweden, the number of TV fires per million sets more than doubled during the period 1990-1995. This report provides information and comment on recent events in the environmental and legislative spheres, and covers some of the product developments in the various families of flame retardant chemicals available commercially for use with plastics resin formulations. Some longerterm ideas and potential areas of chemical development are also described. 1.2 The Report The report starts with an executive summary in Chapter 2 and is followed by a brief description of the different families of flame retardant materials and their uses in Chapter 3. The trends in materials developments and the products available in the marketplace are examined in Chapter 4. Chapter 5 covers most of the main plastics families and some of the methods used to make them flame retardant. Some producer-specific information is provided as well as more generic comments on plastics in commercial use. Chapter 6 reviews the supply chain and discusses the source of materials used by the resin suppliers and compounders. The market for flame retardant additives is discussed and some statistical data presented.

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Flame Retardants for Plastics Market Report

Chapter 7 briefly examines some major end uses. These cover • • •

Automotive; Other Transportation Electrical & Electronic Equipment, and Cables Building & Construction

Fire testing is discussed in Chapter 8 with fire safety, environmental issues and legislation covered in Chapter 9. 1.3 Methodology The study has been compiled from substantial desk research carried out on the subject of fire and polymeric materials. Opinions expressed are those of the author, unless otherwise indicated.

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Flame Retardants for Plastics Market Report

2 Summary and Conclusions 2.1 Materials No fundamentally new fire retardant (FR) systems have been developed in recent years. However, many improvements have been made to existing ones as a drive to halogen-free systems has stirred R&D teams. Such developments can prove very difficult in many cases on technical and cost grounds. New offerings from the ‘bromine’ companies are all formulated to achieve acceptance under the German ‘Chemical Banning’ Ordinance. That is, their potential emissions fall below the threshold limiting values for dioxins and furans set out therein. Although the mechanisms are not wholly understood, synergistic reactions are increasingly being used in the formulation of FR additives and multi-functional systems. This is quite likely to be a key area for developments in the future. In FR technology, synergistic effects do not simply produce more efficient systems. They also make it possible to reduce the amounts of other FR agents employed, and may often make a positive contribution towards delivering efficient flame retardancy within increasingly stringent FR regulations. A number of minerals have synergistic action with organic halogenated and phosphorated flameretardants and synergistic processes have also been observed in thermosets, between borates and other hydrated minerals. Incorporation of minerals in intumescent formulations makes it possible to manage better the morphology of the expanded structure that develops on exposure to flame. Growing experience is showing that, despite an apparent increase in material price, FRs used in judicious combinations can, in fact, reduce the cost of the compound, either by making large reductions in the active additive, or by offering multi-functional performance. The most important synergistic FR components currently are antimony oxide and halogen-donor compounds. Metal oxides and other metal compounds are also very promising, particularly in engineering thermoplastics compounds. Formulations with brominated FRs (BFRs) normally contain antimony trioxide as a synergist. However, because of the filament-like structure of antimony trioxide its dust is classified as a carcinogenic material and special measures for the protection of workers must be adopted. For this reason, dust-free systems are on offer that do not cause any problems when processed. Even so, formulations containing antimony trioxide often still have to be labelled. Another major trend in development is seen by the pelletisation of new antimony oxides blends. They extend the benefits of a one-pack system to flame retardants plus the non-dusting and feed benefits of a masterbatch. Antimony is relatively inexpensive and has been used in the past in large quantities as a flame retardant. It is a hazardous material and its use in most countries is controlled by relevant workplace regulations, and there is a trend towards replacing it, or reducing its use. It has an effective synergistic action with most types of halogenated FRs, especially in plasticised PVC compounds. In other polymers (not containing a halogen) a suitably chlorinated or brominated compounds needs to be present to achieve the required properties. A potentially good replacement in many systems is zinc sulfide, which until now has been considered for use as a pigment. New FR grades have been produced for use either alone or in synergistic compounds.

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Flame Retardants for Plastics Market Report

Pure talcs of fine particle size and high lamellar structure, in combination with a new generation bromine compound, make it possible to obtain optimum mechanical properties and fire resistance as well as a limitation on the emission of corrosive by-products. Good results have been recorded with polyolefins in synergy with bromine compounds, for applications such as connectors and appliances. The characteristics of the talc/polymer interface influence both the mechanical and ignition resistance properties of the compound. Increasing the nucleating effect produced by the mineral gives better adhesion of the polymer to the filler and a stronger reinforcing effect. Addition of melamine to mineral filler FRs in polypropylene (PP) generally improves their UL94 test behaviour, eliminating at the same time the after-glow phenomenon that is typical of mineral fillers used alone. Melamine also reduces the specific weight of FR PP, which results in an economic advantage and allows the use of relatively cheap inert fillers such as kaolin and talc which, used alone, do not show any flame retardant properties. With brominated FRs, a partial substitution with minerals makes it possible to improve certain of the mechanical properties and reduce opacity and corrosivity of the fumes generated, so reducing potential environmental hazards. Specially coated magnesium and aluminium hydroxides confer significantly increased combustion resistance and lower levels of smoke evolution, permitting large reductions in additive loading, without sacrificing flame retardant or smoke suppressant performance. Another change is anticipated, whereby foam and coverings for furniture may be drawn further into the legislative net in both Europe and North America. This would accelerate the usage of melamine and phosphorus compounds in foams. Brominated compounds will continue to hold much of the engineering plastics sector and thereby some dominance in the electrical and electronics (E&E) sector. They will continue to be the most significant products because they are the most cost effective (and efficient) solution to many plastics flame retardancy applications. The EU Waste Electrical and Electronic Equipment (WEEE) directive and its effect on recycling plus the debate about fire safety versus environmental issues (especially in domestic appliances) will continue to attract much attention. Borates represent a novel opportunity for synergism with both brominated and non-halogenated flame retardant products. Although known for many years, their time has now, perhaps, arrived as antimony trioxide has come under a cloud. For instance, to capitalise on this opportunity Albemarle, the leading BFR company, is collaborating with US Borax to develop new boraterelated technologies. Brominated FRs generate hydrogen bromide in the vapour phase, which then mops up free radicals generated in a fire, and so suppresses that fire. Borates form a glassy char that cost-effectively retards the dripping tendency of some FR treated thermoplastics. This is essential because such materials by themselves may fail certain flammability tests when they generate molten, flaming drops. Together, the borates and BFRs ‘are a force to be reckoned with’. R&D efforts in halogen-free FRs are often aimed at designing a protective closed barrier on the burning polymer surface to reduce heat and mass transfer to the combustion zone. In some polymer applications this can be achieved by the use of intumescent systems. However, these are not always suitable in other applications for reasons of water uptake, thermal stability or actual FR performance. Therefore, it is of interest to the material developer to have options available to control the structure of the burning polymer surface layer. In this layer no cracks should appear which could allow for the escape of volatile, ignitable gases and so sustain the combustion process.

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Flame Retardants for Plastics Market Report

Aluminium trihydrate (ATH) should continue to experience strong growth but there is much competition from mineral suppliers all anxious to launch special precipitated grades and those with new surface treatments to make them more effective. The drive is the requirement for lower loadings to preserve the balance of mechanical and physical properties for which the particular plastic system has been chosen. The treatment of hydrophilic ATH particles with hydrophobic coatings, such as fatty acids or silanes, provides for more uniform dispersion in the hydrophobic plastic resins. Refinements in magnesium hydroxide chemistry have been accomplished to enable that material to sensibly replace ATH in some higher temperature applications. The hydrated fillers only have an effect at high loadings with the well-known potential impairment of mechanical properties. By employing special surface treatments in conjunction with compatibility agents, manufacturers have in recent times managed to largely offset the negative effects. The current discussions across the plastics sector show a steady upwards trend in demand for reduced flammability, minimum smoke generation and low toxicity, yet with optical, mechanical or electrical properties still being retained. This can be quite difficult to master in technical terms, since these demands are contradictory in some measure and also because the matrix polymers display greatly dissimilar behaviour in the event of a fire, with PVC and polyethylene being good examples. Another trend in many applications is towards halogen-free products or at least to combinations which will permit a reduction in the percentage of halogen. Japanese patents have opened up the market for melamine compounds that can also be used in combination with other FRs such as magnesium hydroxide or even a filler like talc. All new innovations such as the increasing use of zinc compounds or borates contribute towards a safer and cleaner environment. Such developments show that, with a plethora of materials for use either alone or in combination, and an ever greater understanding of the scientific basis of fire and combustion, the industry offers meaningful solutions to the problems of health and the environment, and the cost/performance needs of processors and end-users. 2.2 End User Sectors Plastics compounded with FR additives may be used in a wide range of applications: • • • • •

electrical engineering transportation construction domestic appliances wider general industrial conditions

Each one of these sectors has established its own FR standards and specifications over the past decades, often with reference to local government regulations. As a result, every market segment has a large number of regulations and test procedures forcing materials developers to adapt their formulations to match customer requirements in order to meet the safety legislation of each relevant authority. In Germany, for example, these can differ from one Land to another. Currently, attempts are being made to harmonise standards, with the construction industry farthest along the route to finalise such procedures. Examples of standards are shown in Table 2.1.

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Flame Retardants for Plastics Market Report

Table 2.1 Examples of flame resistance standards Sector Test Evaluation Construction DIN 4102 (Germany) B1, B2 (vertical chimney) Electrical and appliance UL94 (USA) V-0, V-1, V-2, HB (vertical test), IEC 65 (Europe) (horizontal test), pass or fail Others e.g., Mining tests e.g., tunnel test

Fire protection requirements exist in the fields of E&E engineering, the construction industry, transportation, textiles and upholstery for furniture. More than 40% of FRs are utilised by the E&E sector and cables, especially for consumer electronics, business machines, household appliances and industrial applications. In the wake of European harmonisation, national fire requirements in the construction industry and rail-transport sector are gradually being replaced. By 2007, a new classification system and new test procedures for the fire behaviour of construction products will replace existing national systems within the EU. This means there will be more stringent requirements overall, calling for a reassessment of the plastics currently utilised. All the construction products introduced on a national basis will have to be tested according to the new test procedures, particularly the Single Burning Item (SBI) Test, involving a higher outlay on material and higher expenditure, since there are not generally any correlations with the existing national tests. The same applies for railway rolling stock, whose test procedures are currently harmonised on a national level and will become so at European level in future. In the case of international test procedures already introduced, changes are pointing towards an increasing level of fire protection.

2.2.1 Automotive Plans are afoot to have the low-level requirements of MVSS 302, which is a Bunsen burner test on horizontal specimens, upgraded, since, in the latest car models with their compact designs and electronic door locks, the outbreak of a fire needs to be delayed for longer than has been the case. In addition to this, the new 42V electrical systems will also place increased requirements on fire safety; perhaps up to UL94 V-0. The US National Highway Transportation Safety Administration plans to change its rear-impact test for cars from 30 to 50 mph. The implications for fire safety are huge, as they would affect fuel systems, interior as well as certain exterior components.

2.2.2 Electrical Appliances The Underwriters Laboratory adopted in 2001 new fire safety standards that are resulting in a major increase in the utilisation of FR chemicals. More than 40 other UL standards, governing thousands of goods, are directly affected, including hair dryers, toasters, power drills, and electric can openers. Manufacturers have two choices; to re-design their products or use fire-resistant outer casings. FR additives are seen by most as the more cost-effective solution.

2.2.3 Business Machines and Consumer Electronics Business machines and consumer electronics are likely to ‘merge’ into a single sector in the future, meaning that the low-level fire safety requirements currently in force in certain regional applications (TVs in Europe) will be superseded by much more stringent, and uniform, requirements.

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Flame Retardants for Plastics Market Report

2.2.4 Building and Construction The European Commission has been preparing for harmonisation of building regulations including the fire testing side of such controls. This has been proceeding for many years as preliminary work to the recently introduced Building Products Directive, which has been incorporated into the national legislation of all Member States. This has covered the harmonisation of fire tests and the classification systems resulting from them for combustible building products. Uniform fire test methods that are valid for the whole of the EU will be introduced in the near future.

2.2.5 Furniture The US Consumer Product Safety Commission (CPSC) agreed in 2001 to move to tougher, new safety standards for mattresses. California introduced its own laws for improved sleeping products. Equally, a consortium of companies and associations drafted federal legislation for higher safety levels in upholstered furniture.

2.2.6 Trends What are the current trends and innovations? First of all, demand for flame retardants will rise worldwide on account of stricter fire-safety levels. It will be spurred on inter alia by the harmonisation of fire protection requirements for products in the construction industry and for railway rolling stock within Europe, as well as through the introduction and implementation of fire regulations in newly industrialised countries, especially in Asia, with particular focus on China. The 42V power supply in cars and UL94 V-0 television sets in Europe will similarly contribute towards this trend. Over the medium term, US fire safety requirements could be imposed on upholstered furniture in the private sphere throughout the entire country, which would ensure a boom in the demand for flame retardants. Tried-and-tested flame retardant systems based on bromine compounds will continue to be used, with just a few exceptions, on account of their outstanding price-to-performance ratio. This is clear from printed circuits, where halogen-free reactive and additive FR systems are not able to displace the FR4 laminates based on tetrabromobisphenol-A (TBBA). Such is the case in Europe, at least. The situation could prove to be different in Asia, since the giants in the sector, such as Sony, have committed themselves to halogen-free printed circuits. In Europe and Asia, innovations in flame retardant plastics continue to be in the field of halogen-free systems. This is borne out by new developments such as nanocomposites in the cable field and in nanotechnology for PC/ABS blends. Over the medium term, all plastics will be available with halogen-free systems. It will then be possible to cover all the different requirements with the established and the new FR plastics and thus serve the market in an optimum fashion. 2.3 General

2.3.1 Testing and Environmental Factors Of particular importance is the SBI test, which will be used to test building products in future. In many cases, the fire safety requirements imposed on combustible materials will be more stringent than those of existing national tests, a fact that should well lead to greater demand for flame retardants of one sort or another. Similar considerations have been applied to other sectors. Railway rolling stock is an area for which harmonised fire tests are planned at European level. Another is electrical and electronic

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Flame Retardants for Plastics Market Report

engineering where international standards already apply to a great extent, but local variations may be required, considered or tolerated. An example is that of TV housings; provisions in the US and Asia are strict enough to necessitate the utilisation of flame retardants, whereas in Europe they are so lax that often flame retardants are no longer used. As far as environmental questions are concerned, FR systems tend to be assessed much more pragmatically and less emotionally and ideologically than before. Instead of whole groups of flame retardants being ‘written off’ as possessing general polluting potential, each FR is evaluated nowadays with regard to its environmental properties and a decision is taken as to its suitability for the intended application. This also applies to mechanical or material recycling, energy recovery and disposal. It ensures that the technically, economically and ecologically optimum FR system can be used in the application under review. The introduction of new fire safety standards and environmental regulations will mean a period of growth for the FR chemicals market and affect industries such as construction, electronics and transport. More stringent flammability standards are already being introduced, such as performance-based codes in the building industry, and voluntary actions that improve fire safety in consumer products. This has resulted in greater demand and changing requirements for flame retardants, favouring low smoke and fume products. The environmental impact of flame retardants has been under discussion by regulators and has resulted in increasing demand for more environmentally acceptable materials, which represents one of the biggest challenges for FR producers. The key driver for future growth will be fire safety and environmental regulations, which will demand the use of these chemicals in many more industries than before. This new legislation will also result in end-users changing the type of FR they buy to meet the latest specifications. This in turn will have a knock-on effect for the producers who will be forced to develop new products to keep pace and to serve the new markets and applications that will then be covered.

2.3.2 Overview Public safety issues, especially in the United States, have revealed a very poor record-keeping tendency with regard to fires in public places. The CPSC, the US Fire Administration, and the National Fire Protection Association issue annual estimates on fire losses. Around 400,000 domestic fires require fire-fighter response, which kill about 4,000 persons, with another 20,000 suffering severe injury. Some 70,000 fires involve electrical distribution and appliances, another 40,000 stem from furniture and mattress fires. The available statistics grossly underestimate the problem. For example, the federal government, which employs two million civilians in 8,300 buildings, has no data on even the largest fires on its own property. Also, and incredibly, there have been years in which large States such as Pennsylvania and California have not reported a single fire. Clearly this shows that the nationwide fire reporting systems are extremely inadequate. European countries are not much better, but even with partial data there are reportedly about 80,000 people severely injured in European fires each year. Of these, some 60,000 are hurt in their own homes. Many injuries result from TV fires. For all the criticism of FRs, not by scientists or even the environmentalists, but mainly by politicians, the European Commission acknowledges that there would be 20% more fire deaths in Europe if FRs were not being used. In the same vein, the UK reports that 1,860 lives have been saved in the last 10 years or so because of its safety standards for upholstered furniture, due to the use of FRs.

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Flame Retardants for Plastics Market Report

The marketplace is reflecting this need for action. Companies are responding with products that use FR additives for extra safety in a wide array of goods, including plastic outer casings and housings, candles, power cords, and so on. In the US, as mentioned before, TV housings are made flame-resistant. In Japan some of the major manufacturers are following suit. This has not been driven by any regulation. They want to ‘do the right thing’. This phenomenon is occurring across a range of goods, although seen, obviously as a marketing tool, it also covers an ethical reason as well. It would now appear that Green or Eco labelling that was weighted in favour of the environment, almost to the exclusion of all else, has now taken on board the need to consider fire safety in some measure. In various countries, there is an implicit acceptance that fire safety concerns must merit equal consideration with those for the environment, at the very least.

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Flame Retardants for Plastics Market Report

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Flame Retardants for Plastics Market Report

3 Flame Retardants This chapter gives the briefest of outlines of the different flame retardant families and their capabilities in protecting plastics compounds. A more comprehensive review of fire chemistry and the actions of the different types of flame retardant materials is to be found in the previous edition of this Rapra report, ‘Fire – Additives and Materials’, Rapra Technology Ltd., 1995. 3.1 General Protection against fire by the employment of flame retardants in plastics formulations must achieve at least one of several tasks during the course of a fire. These can briefly be stated as: • • • •

raising of the ignition temperature, reduction of the rate of burning, reduction of flame spread, and reduction, if not elimination, of smoke generation.

The most important flame retardant families are based on both organic and inorganic compounds. In principle, flame retardants act by interrupting the process of combustion in the solid and liquid phases of the substrate or in the gas phase. Their effect can be of a physical or chemical nature. Chemically acting flame retardants work best (bromo- and chloro-organic systems in the gas phase, phosphorus and nitrogen-containing systems in the condensed phase). Physically acting inorganic flame retardants based on metal hydroxides and salts have a weaker effect. The active species in fire retarding are the halogens, chlorine and bromine, phosphorus, and water. The performance of these primary flame retardants is enhanced by synergists: antimony, zinc and other metal salts. Some help to develop a protective char (e.g., phosphorus-based systems), separating the unburned polymer from the flame and heat source. Others change the flame chemistry by inhibiting free radical formation in the vapour phase (halogen-based systems). Still others release water upon heating (hydrated systems), quenching and cooling the combustion reactions. Proper choice of a flame retardant for optimum performance in a plastic depends on the thermal stability of the flame retardant and the decomposition temperature of the polymer. Ideally, the flame retardant should be activated at a temperature slightly below the decomposition temperature of the polymer. In this way, the flame retardant can promote char formation to reduce the amount of flammable fuel the polymer can generate, or it can mix with potentially flammable vapours to inhibit ignition or burning. In the case of a fire, the development of smoke is of equal importance to the flammability of the plastic. The important factors are density, toxicity and the corrosive effect of the smoke gases. Carbon black increases the density of the smoke gases, the main toxic elements of which are incompletely oxidised carbon, usually in the form of carbon monoxide gas. Crosslinked thermosets generally produce less smoke than most thermoplastics, rather, they tend to carbonise. The polymers that are highly resistant to heat will keep their aromatic or heterocyclic ring structure in the case of fire and carbonise into networks similar to graphite.

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Flame Retardants for Plastics Market Report

3.2 Organic Halogen Compounds The halogenated flame retardants may be bromine- or chlorine-based and can be classified as: (1) (2) (3)

halogenated paraffins chlorinated alicyclic compounds chlorinated and brominated aromatic compounds

Flame retardants containing bromine are twice as effective as those containing chlorine. However the price is higher and the UV resistance is lower. The products containing bromine are of aliphatic, cycloaliphatic, aromatic and aromatic-aliphatic type. Tetra-bromobisphenol A (TBBA) is condensed as a flame retardant in PC and expanded polystyrene (EPS). In phenolic and unsaturated polyester (UP) resins di- and tri-brominated phenols and tetra-bromophthalic anhydride serve as reactive components in the resin backbone. These materials, when used alone in plastics, provide a limited degree of flammability performance. The addition of antimony compounds greatly enhances their efficiency, allowing for lower loadings of the halogenated materials needed for equivalent performance. Several antimony derivatives are commercially available, with antimony trioxide being the most widely used. The polybrominated diphenyl ethers (decabromodiphenyl ether, octabromodiphenyl ether) have been the most widely used of the brominated materials. These additives are cost efficient and are the conventional choice for high-impact polystyrene, ABS, and other styrenics. However, their use has been under challenge for environmental reasons. Other brominated species that cannot generate dioxin species under any conditions are now more in favour than PBDEs. Halogens function by the formation of halides which inhibit the branching radical reactions that propagate a flame. In effect, they make the combustion process less efficient. A consequence of this mechanism is that polymers formulated with halogenated additives burn with a smoky flame. Moreover, the combustion products are acidic. This means that they are not normally the first choice for wire and cable applications. In addition, these materials have been under scrutiny in recent years regarding their toxicity; however, threatened legislation against these types of product does not appear to have had a great effect on the extent of their use. The advantages and disadvantages of this class of materials can be summarised as follows: Advantages • Effective at low concentration • Relatively little detrimental effect on physical properties • Easy incorporation and processing • Moderately priced materials

Disadvantages • Generally require a synergist • May be a skin and eye irritant during handling and processing • Release of toxic combustion products

3.3 Phosphorus Compounds Phosphorus-containing flame retardants include inorganic phosphates, insoluble ammonium phosphate, organophosphates and phosphonates, halophosphates and chlorophosphonates, phosphine oxides, and red phosphorus. The mechanism for flame retardancy varies with the phosphorus compound and the polymer type. A phosphorus containing flame retardant can function in the condensed phase, the gas phase, or concurrently in both phases.

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Important categories are the phosphate esters, extensively used in flexible PVC, modified polyphenylene oxide and some cellulosic polymers; and chlorinated phosphates, commonly used in polyurethane formulations. Some phosphorus compounds decompose in the condensed phase to form phosphoric or polyphosphoric acids. These can act as dehydration catalysts, reacting with cellulosics for example, to form a good char. Char yield is also increased with rigid polyurethanes. The polyphosphoric acid can also form a viscous molten surface layer or surface glass. This layer can shield the polymeric substrate from the flame (heat) and oxygen. Intumescence, which requires an acid such as phosphoric acid, results in a dense carbon char on the polymer surface protecting the substrate from heat and oxygen. Red phosphorus is also used as a flame retardant – disadvantages include high flammability and in the presence of heat and/or friction it can explode. In the presence of moisture it releases phosphine. However, red phosphorus has a number of advantages as a flame retardant – the material need only be added in fairly low concentrations of around 6-10%. At this addition level, the phosphorus has a negligible effect on physical properties. An overview of the advantages and disadvantages of the phosphorus-containing flame retardants is given below, but allowances must be made for the differences between the various classes within this group. Advantages • Effective at low concentration - organic types • Easy incorporation and processing • Relatively little detrimental effect on physical properties • Good UV stability • Low-moderate price materials

Disadvantages • Lack of permanency and hygroscopicity of inorganics • Potential health hazard during processing organics • Release of toxic combustion products from organics

3.4 Antimony Trioxide Certain antimony compounds function as synergistic flame retardants when used in conjunction with suitable halogenated organic compounds. When used alone the antimony compounds are essentially ineffective as flame retardants. Antimony trioxide is the most widely utilised. In its function as a flame retardant, antimony trioxide, in combination with an organic halogen compound, forms antimony trihalide and oxyhalide at flame temperatures. The antimony trihalide is the principal active agent and acts in both the flame phase and the solid phase to suppress flame propagation. The volatile antimony halide acts as a source of halogen radicals that react with flame free radicals through a reaction that is less exothermic than the uninhibited propagation reaction of oxygenated free radicals, thereby reducing the heat generated and as a consequence reducing the rate of thermal degradation of the plastic matrix. In the solid phase the antimony oxide promotes the formation of highly crosslinked carbonaceous char, which serves to insulate the substrate and to restrict the diffusion of volatiles in the flame. A broad range of halogenated flame retarding compounds can be used in conjunction with antimony trioxide, typically chlorinated paraffins and chlorinated cycloaliphatic compounds, brominated aromatic compounds and brominated phosphates. However, the major application for antimony trioxide in terms of consumption is in flexible PVC, where the chlorine available from the polymer is sufficient to provide the desired level of flame retardancy.

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The advantages and disadvantages of antimony trioxide are summarised below. Advantages • Effective at relatively low concentration, typically 3-6 wt%

Disadvantages • Requires halogenated compounds • Affects pigmentation and physical properties • Potential health hazard from dust • Increases smoke and afterglow • High cost

3.5 Alumina Trihydrate One of the most common approaches to fire-retarding a halogen-free polymer system has been the addition of high loadings of alumina trihydrate, which can undergo an endothermic dehydration by releasing 34.6 wt% water in the temperature range 220 to 250 °C. Low in cost and environmentally acceptable, it is used in applications where high filler content is technically possible and processing temperatures do not exceed 180 °C. To be fully effective as a flame retardant/smoke suppressant ATH has to be used at high loadings (typically 40 to 60% by weight) and it is therefore essential that consideration be given to the effect on polymer processing and physical properties. First used as a flame retardant in carpet backing, the largest tonnage of ATH now goes into glassreinforced unsaturated polyester and other thermosets. In wire and cable applications, ATH is used in PVC, low density polyethylene (LDPE), ethylene-propylene-diene terpolymer (EPDM) and ethylene-vinyl acetate copolymer (EVA). A range of grades is commercially available, varying from coarse ground materials to ultrafine precipitated materials. Recent studies have demonstrated that there are major advantages in using a combination of ATH and zinc borate in a variety of halogen-free polymer systems. The advantages and disadvantages of this class of materials can be summarised as follows: Advantages • Combined filler and flame retardant functions • Does not require halogens • Does not produce toxic gases • Suppresses smoke formation • Non-volatile and unaffected by water • Low cost • Non-toxic

Disadvantages • Requires high loadings • Affects physical properties and processing behaviour • Relatively low decomposition temperature

3.6 Magnesium Hydroxide Magnesium hydroxide, like alumina trihydrate, acts as a flame retardant and smoke suppressant. Like ATH, it functions by the release of water vapour at elevated temperature, which absorbs heat and dilutes the combustible gases. However, the major advantage of magnesium hydroxide over ATH is the higher decomposition temperature, 330-340 °C compared with 210-220 °C for ATH, meaning that compounds containing magnesium hydroxide can be processed at higher temperatures than those using ATH. Again high loadings, typically in the range 50-60%, are required to achieve desired levels of flame retardancy.

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The main opportunities for magnesium hydroxide are in PP applications, but it is also used in elastomeric cable compounds. One of the main limitations is its tendency to agglomerate in polymers, affecting processibility and performance. This is being overcome by the development of modified materials using surface coatings etc. 3.7 Zinc Borate Growing awareness of the smoke hazard posed when using antimony trioxide as a flame retardant has led to the development of products using zinc borates. The multifunctional zinc borate (2ZnO.3B2O3.3.5H2O) is an effective and economical fire retardant synergist of organic halogens in polymers. It has been used extensively as a flame retardant, smoke suppressant and afterglow suppressant. Zinc borate retains its water of hydration up to a temperature of 290 °C and releases 14 wt% water in the temperature range of 290 to 450 °C. In contrast to ATH, zinc borate promotes the formation of a strong residue in a burning polymer. This residue is fire resistant and can protect the unburned polymer from being exposed to high temperatures and further combustion. It has been demonstrated that the combination of zinc borate and ATH can be used as an effective flame retardant and smoke suppressant in halogen-free polymers such as EVA, polyethylene, EPDM, ethylene-ethyl acrylate copolymer (EEA), epoxy, and acrylics. In some polymers such as silicone rubbers, zinc borate used alone is very effective as a fire retardant. Zinc borates have also found uses in PVC formulations. They have been shown to be effective flame/smoke suppressants when used as partial replacements for the antimony oxide that is normally used in a typical flexible PVC cable jacket, for example. For flexible vinyl and PVC plastisol formulations, a half to two-thirds of the antimony trioxide can be replaced by zinc borate without loss of flame retardancy. If a small decrease in flame retardancy can be tolerated, all of the antimony trioxide can be replaced with zinc borate, leading to smoke reductions of up to 65%. The flame retardancy can be increased and smoke formation decreased by adding ammonium octamolybdate to the borate-containing formulations. 3.8 Intumescent Materials Intumescents function because, under fire conditions, they foam to produce an insulating carbon char which both protects the substrate from high temperatures and allows only a small proportion of polymer to be involved in the fire. Heat release can be controlled because the surface of the char nearest the flame will ablate, so absorbing energy. This contrasts with conventional flame retardants that absorb energy by endothermic chemical decomposition or liberation of water, or by altering the polymer’s surface chemistry to slow down oxygen access. Intumescents are said to have a key advantage over filler-type non-halogenated flame retardants in that they are effective at lower addition levels than traditional materials. For example, an intumescent based on ammonium polyphosphate will achieve the same level of protection at addition levels of 25 to 35 parts by weight (pbw) as a typical non-halogenated flame retardant, such as alumina trihydrate or magnesium hydroxide, at between 60 and 70 parts by polymer weight. Nitrogen-containing compounds based on melamine are used in a more restricted field (polyamide and polypropylene).

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4 Products and their Markets This chapter gives information about some of the flame retardant products on the market and discusses their applications in various plastics. Comments are made with regard to the eventual destinations and fitness-for-purpose of the materials. 4.1 Organic Halogen Containing Materials

4.1.1 Bromine Compounds Materials, like ABS and HIPS are widely used as housings for brown goods, IT and business machines. Unfortunately they burn easily but can be protected by the correct use of flame retardant science and technology. The starting point has always been to use brominated FRs plus antimony oxide as a synergist. However, these long-standing products do not often meet all of the requirements. Decabromodiphenyl ether is cost efficient in HIPS but has poor UV stability and is not melt blendable during injection moulding. TBBA is cost efficient and melt blendable in ABS but has low thermal stability, poor impact properties and may not meet UV stability standards. It also lowers heat distortion temperature. Many companies are developing new, more environmentally friendly brominated flame retardants.

4.1.1.1 Dead Sea Bromine Group Newer brominated materials from Dead Sea Bromine have been developed to allow the company non-polybrominated diphenyl ether (PBDE) options for a range of polymers, especially styrenic copolymers. Brominated epoxy oligomers (BEO) and modifications of this FR (MBEO) are diphenyl ether-free products used in high-impact polystyrene. The MBEO has more bromine. Their use allows for a significant improvement of the impact properties of HIPS. The BEO is designated F-2016 and has a bromine content of 50% with a softening range of 105-115 °C. The MBEO is called F-3014 with the higher bromine content of 56% and a slightly higher softening range of 113-127 °C. Both are formulated at around 14-16% loadings plus an antimony oxide synergist. They combine good to excellent UV stability with good melt flow properties during injection moulding but suffer from rather poor impact properties. F-2016 is used for UV stable ABS applications. F-2016 is a brominated epoxy oligomer with around 50% bromine and a molecular weight of 1600 designed to ensure optimal properties in styrenic copolymers. Brominated epoxy oligomers offer a combination of high flame retardant efficiency, UV stability, good mechanical properties and thermal stability. They are non-blooming due to their physicochemical properties and polymeric structure. The epoxy groups provide a good compatibility with the matrix of the plastic; and the oligomeric structure and its softening range are the main factors that limit the mobility of this particular flame retardant in styrenic copolymers. The low molecular weight of F-2016 has been chosen to provide better flow during injection moulding as well as good surface appearance. F-3020 is an end-capped brominated epoxy oligomer with 56% of bromine and a molecular weight of 2000. It has been developed to give a better compromise of UV stability and impact properties in styrenic copolymers than other brominated epoxy oligomers.

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Improvements have been made to FR-1806, a hexabromocyclododecane (HBCD), to provide better colour thermal stability for EPS while FR-1206HT can cope with higher temperatures for extruded polystyrene (XPS) and is also a cost efficient FR for HIPS and PP at V-2 rating under UL94 testing. FR-720, TBBA bis(2,3-dibromo)propyl ether, offers an efficient combination of aliphatic and aromatic bromine to meet UL94 V-2 with very low bromine content in HIPS and PP. It contains 68% of bromine. It is widely used for water discharge pipe to pass B1 class in DIN4102, and as lamp sockets to V-2 and V-0 under UL94. This melt blendable FR has optimal thermal stability but has a tendency to bloom in PP. 3-5 phr are required for V-2 with 1-1.5 phr of antimony trioxide and 14-18 phr for V-0 with 5-7 phr of antimony trioxide. Tris(tribromoneopentyl) phosphate with 70% of bromine is offered as FR-370. This combination of bromine content and phosphorus on occasions obviates the need for any antimony trioxide. Moreover, the position of the bromine in the molecule contributes to good thermal and light stability. It also reduces the problem of blooming and plateout. It is recommended for the production of seats and furniture for use under UV exposure. The melting point of 181 °C is advantageous compared with those of other FRs, and so allows a reduction of 10 to 20 °C in the processing temperature. 2-3 phr of FR-370 is the loading range for V-2 with 1-1.5 phr of antimony trioxide. Moreover V-2 can also be achieved in an antimony-free formulation containing 6% of FR370. The company believes FR-370 should open up new opportunities for PP in exposed sections. A special grade, FR-372 has been designed for PP fibre and textiles. The usual method of application is via a masterbatch containing 30-40% of flame retardant. This concentrate is then diluted in the PP to reach around 3-5% of FR-372 in the final composition. FR-1206HT contains 66.2% of bromine and can be processed at up to 240 °C at 2-3.5 phr loading in PP with around 1 part of antimony trioxide. Flame retardant systems based on decabromodiphenyl ether or its substitutes are often regarded as the safest ones to provide high standards of retardancy up to UL94 V-0 rating. FR-1210 contains 83% of bromine and these aromatic additives are recommended for situations when polypropylene is to be processed at over 230 °C. However, as PP’s ignition temperature is comparatively low, high loadings of such additives are necessary to reach V-1 or V-0 standard. Typical formulations contain 35 phr of FR additive plus around 12 phr of antimony trioxide. The total weight of functional additives present can be reduced by the use of 20% talc in the formulation. FR-1808, brominated trimethylphenyl indane, contains 73% of bromine. It has good thermal stability due to the aromatic linkage of the bromine.It is suggested for use in filled polypropylene compounds at levels of around 20-25 phr with magnesium hydroxide at loadings of 20 to 35% to give a UL94 V-0 rating. FR-1808 has a melting range of 240-255 °C, which has important beneficial effects on flow properties of the subsequent plastic compound. When processed above its melting range, FR-1808 behaves as a melt blendable flame retardant and has important benefits on properties such as impact strength and flow. It is recommended to carry out injection moulding at a temperature of at least 250 °C so that the FR-1808 is fully melted and to improve impact properties. The additive’s high melt flow and impact strength can give thinner wall parts and shorter cycle times. FR-1808 has undergone extensive toxicological and environmental testing. The tests have shown very low acute and repeated dose toxicity. In addition, the Fresenius Institute performed analyses on both the neat product and on gases evolved when simulating conditions in a municipal incinerator. The results indicate that FR-1808 poses no risk through any release of brominated dioxin or furan species.

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The main advantages offered by FR-1808 include a significant improvement in flame retardancy, with values of limiting oxygen index (LOI) up to more than 50 being achieved quite easily. In addition, good processing aid properties offer long spiral flow, all of which are especially useful for the production of thin-wall parts with glass-reinforced thermoplastics. Thermomechanical properties such as tensile, flex, impact and heat deflection temperature (HDT) are either maintained or improved and a fairly good comparative tracking index (CTI) is achieved. FR-1808 is particularly used in styrenics and engineering thermoplastics such as polyamide (PA) 66. Its good miscibility with styrenic copolymers has been explained by its total and irreversible amorphisation and the closeness of its glass transition temperature to that of polystyrene. It has a molecular weight of 707 and a decomposition temperature 50 °C lower than brominated polystyrene. A different FR is suggested for glass reinforced PP. This is poly(pentabromobenzyl acrylate) containing 70% of bromine, offered as FR-1025. The softening temperature of around 180 °C is optimal to provide both processing aid during injection moulding and high heat distortion temperatures under load. Around 40 phr of FR-1025 are suggested for 40 phr glass content with a quite high antimony trioxide presence, to obtain V-0 under UL94. The acrylate part of FR-1025 improves the compatibility between the glass fibre and the PP matrix to optimise impact and thermo-mechanical properties. FR-1210 can be used in PA6 applications, but it decomposes when applied in PA66. FR-1025 is particularly suitable for polyamides, PET and polybutylene terephthalate (PBT), with or without glass fibre reinforcement. As a result of its aromatic structure, high bromine content and good thermal stability, FR-1025 has inherent advantages over other halogenated FR additives offered for the same applications. Also polymers containing FR-1025 have good processibility. FR1025 is now produced by Dead Sea Bromine in a completely new facility that utilises the latest polymerisation techniques. This step was taken to support the very high growth rate of its use in engineering thermoplastics and has resulted in improved quality. Relative to other FRs, FR-1025 has advantages through its high effectiveness and its contribution to better workability of thin injection moulded parts, good impact strength, improved electrical properties and better thermal ageing. After 1,000 h of thermal ageing at 190 °C of glass reinforced PBT containing FR-1025, tensile properties are maintained above 50% of their initial value while non-flame retarded PBT would fail during this test. Similar effects of thermal stabilisation of PP by brominated flame retardants are observed during thermal ageing at 150 °C for 1 month; retention being around 60%. Connectors made with FR-1025 are found in patch cords for computers and in automotive electronics as well as in various inner parts of domestic appliances. It also exhibits special advantages in recycling since it is possible to add high amounts of reground old products (that contain FR-1025) to commercial PBT resins without loss of properties. Multi-layer epoxy laminates demand excellent electrical insulation and the high purity of FR-1524 (TBBA) used in their production. The flame retardant of choice for transparent, UV stable, polyester resin sheet for the building industry is FR-522, a brominated aliphatic diol that guarantees low discoloration of the sheets during long sun and light exposure. Other brominated FRs from Dead Sea Bromine are reactive types that should be compatible with any solvent system that is utilised as a polymerisation medium. So, aliphatic materials such as FR513 (in alcohol) and FR-522 (diol) have good solubility in the polyol or trichloropropylphosphate (TCPP) systems used for the production of polyurethane foams.

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Brominated polystyrene FRs are preferred when high values of tracking index are needed in polyamide applications. For other BFRs, such as the FR-1808 or FR-2400, tracking index value is improved by adding 10 to 20% of surface-treated magnesium hydroxide. Tris(tribromophenyl) cyanurate, known as FR-245, has been studied for utilisation in styrenic copolymers. It is a melt blendable material that combines good impact properties and UV stability in styrenic copolymers and their alloys. FR-245 is a joint development between Dead Sea Bromine and a Japanese company, Dai-Ichi Kogyo Seiyaku (DKS), and aims to offer a balance of properties that include high melt flow during injection moulding, excellent light stability, good impact strength, and high heat deflection temperature (HDT). The chemical structure of this cyanurate combines a 67 wt% aromatic bromine and a cyanurate segment to provide good FR efficiency and UV/light stability. FR-245 also contains 4% nitrogen. It has a melting point of 230 °C, and a molecular weight of 1067. Use of FR245 also enhances flow during moulding as it melts during the process. It is not related to diphenyl ether chemistry and is designed to be environmentally friendly with no risk of dioxin or furan formation. In both ABS and HIPS, FR-245 offers an excellent combination of melt flow, impact resistance and light stability. Recycling work on ABS flame retarded with FR-245 have shown that a loading of 50% scrap in virgin compound can undergo six recycling loops without any significant changes in tensile properties. It is used in styrenic copolymers for copy machine parts, TV and video casings and housings for kitchen hoods and similar devices. It is now preferred in PC/ABS alloys over phosphate derivatives if a high heat distortion temperature is required. Tribromoneopentyl alcohol (FR-513) is a reactive FR for applications in polyurethane foam materials and is recommended for non-leaching flexible foam applications such as combustion modified heat resistance (CMHR) products. It is also one of the preferred FRs for CFC-free rigid PU foam. Both in flexible and in rigid foams, systems based on FR-513 fulfil the highest fire safety requirements in Europe. A new range of products from Dead Sea Bromine was fully introduced in early 2002. The PR-5000 series have been aimed at providing the market with tailor-made fire safety solutions for particularly demanding applications. Some of the criteria met by them are: • • • • • •

Improved flame retardation properties and antimony trioxide-free systems, Long-term thermal and UV stability, Improved corrosion protection at high processing temperatures, Dust-free systems, Low smoke generation, Improved melt flow in injection moulding.

PR-5104 containing 66% bromine is a dust-free, 100% active FR masterbatch for engineering plastics. It is based on the company’s experience of high-molecular weight polymeric brominated FRs as carriers. This material provides good processibility, high temperature resistance and outstanding compatibility between fibre reinforcement and the resin matrix. PR-5127 is an aliphatic system with 63% bromine combining improved flame retardancy with colour thermal stability and corrosion protection in UL94 V-2 HIPS and PP applications. PR-5183 reaches class V-0 in UL94 without antimony trioxide in polyamide. It enables the compounds to exhibit a good tracking index and low smoke generation.

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PR-5371 contains 65% bromine and offers outstanding light stability. In PP compounds it can produce UL94 V-2 with <1% bromine and no antimony oxide. V-0 is reached with <6% bromine and 7.7% antimony trioxide.

4.1.1.2 Great Lakes PH 73FF is a free-flowing form of tribromophenol, used as a fire retardant intermediate. It is normally used to produce brominated epoxy oligomers for use in ABS and other engineering polymers. In its standard form, the chemical is a low melting-point solid that tends to compact. However, it is now available as a briquette that is both non-compacting and non-dusting. According to Great Lakes, another benefit from PH 73FF is that the briquettes stabilise the colour of the intermediate during transit and provide a more consistent colour in flame retardant products. Firemaster 2100 is a general-purpose brominated compound not based on diphenyl ether chemistry. It is supplied as a uniform white powder suitable for formulations requiring white or light-coloured products. Use is foreseen in applications such as TV cabinets, foam insulation, wire and cable, appliances and textiles. Great Lakes produces its brominated styrene polymers in a different way from its competitors. Competitive products are made by post-brominating the polystyrene polymer. This can be a difficult reaction and sometimes by-products are formed that can reduce thermal stability in the resultant material. To reduce the impurities, the competitors have developed additional steps that then improve the thermal stability, albeit not entirely. Great Lakes polymerises a brominated styrene monomer. This monomer can be either homo- or copolymerised. In this way, a variety of different products that vary in bromine content or in molecular weight, can be made to address specific performance needs of the customer. This route contains some inherent strengths but also weaknesses relative to competitive products. PDBS-80 was the first in the series. This material is a homopolymer of dibromostyrene that contains 59-60% bromine. Its primary applications are in high-temperature polyamides and polyethylene terephthalate (PET) because it has excellent flow characteristics and very good thermal stability. In addition, there are benefits of excellent colour retention. The main weakness of this approach is the bromine content relative to the competitive material. Today’s competition contains around 68% bromine. This can translate into a 2-3 parts difference in the load level needed in the protected polymer to give equivalent flame retardancy. This deficiency was remedied by the introduction of a series of homopolymers based on a new monomer containing 64-65% bromine. The first was Firemaster PBS-64, which is a homopolymer of a dibromo, tribromo styrene monomer. This is aimed also at high-temperature polyamides and the PET area. The molecules have been designed to retain excellent thermal stability and good flow properties. PBS-64 is especially effective in high temperature polyamides where high thermal stability, flow and colour stability are of prime importance, needed, for example, when making small electronic parts under fast cycling, high shear conditions. High thermal stability is also important when components are recycled at end-of-life, especially with regard to colour retention. However, PBS-64 is darker and more expensive than PDBS-80. A higher-weight version was developed for applications in PBT and regular PA6 and 66. PBS64HW is also a homopolymer of dibromo and tribromo styrene with ~64% bromine. The higher molecular weight helps give the best physical properties, although flow is compromised albeit not as low as the competitive brominated polystyrenes. PDBS-80 typically is used at 22 parts with 7 parts of antimony trioxide (ATO) to give V-0 in a 30% glass filled PA66, whereas PBS-64 and the brominated polystyrene use about two-thirds parts less and slightly lower levels of ATO.

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Table 4.1 shows a comparison of PDBS-80, PBS-64 and a competitor brominated polystyrene in a high-temperature polyamide resin. PBS-64HW does not feature, since it is not recommended for the high temperature PAs due to its lower flow, which is a critical property in such resins. Table 4.1 Comparison of brominated styrene polymers in 30% glass-filled HT polyamides Properties PDBS-80 PBS-64 BPS* % FR / % ATO 22/7 20/6.4 19.5/6.3 UL94, 1/32" (0.8 mm) V-0 V-0 V-0 Tensile strength (MPa) 160 168 150 Tensile elongation (%) 2.1 2.2 1.9 Izod impact (unnotched) (J/m) 560 651 507 * Competitive brominated polystyrene Source: Speciality Chemicals Magazine, reproduced with permission.

One of the deficiencies of brominated styrene polymer FRs is that they are not very compatible with the polyester or polyamide resins. Typically they are present as a discrete phase. It has been found that by using certain copolymers instead of homopolymers, the compatibility of this type of flame retardant can be improved. A new product called Firemaster CP-44B uses this technology. CP-44B is a copolymer of PBS64HW and glycidyl methacrylate (GMA). Typically, 0.25-1% of GMA is required to give this compatibility. The principal is that the copolymer has the ability to react with the acid end groups that exist in the polyamide and polyester resin to better disperse the product throughout the polymer phase. In addition, in some cases the level of synergist may be reduced yet still give the same level of FR performance. Another benefit of the new technology is an improvement in retained colours, but with a decline in flow. It is important to control the molecular weight and the percentage copolymer to maximise the compatibility effect without totally removing the flow advantage of these products. As they are expensive they would only be recommended where they offer an advantage or give properties not achievable by another product in the range. In many formulations using Firemaster CP-44B, the synergist level can be reduced by 20-30% and a strong V-0 performance still obtained. This is an advantage in a couple of areas. It can reduce the cost of formulating the product and can also help reduce specific gravity. Physical properties are comparable with PBS-64HW and competitive brominated polystyrenes. The copolymers are also particularly effective in unfilled polyester applications. CP-44B gives a strong V-0 result, while comparable levels of the competitive brominated polystyrene and PBS-64HW gave V-2 ratings. Firemaster CP-44B and its ‘companion’ 44C are highly compatible copolymers used in electromechanical devices, business machine parts, power tool housings and appliances.

4.1.1.3 Albermarle Albemarle offers a range of BFRs under its Saytex banner. Saytex CP-2000 is widely used for printed wiring boards laminates made from FR4 epoxies. It is reacted into the epoxy, so that there is no potential for leaching out of the resin. The FR meets the German Dioxin Rule. It is environmentally acceptable, thermally stable at high temperatures and does not disrupt resin properties when soldered. It can be used as an additive in ABS and also as a raw material in brominated epoxy oligomers in ABS and high impact polystyrene (HIPS).

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Saytex 8010 and Saytex BT-93 are diphenyl ether (DPE)-free and are not melt blendable. They have fair to excellent UV stability, but have limitations in impact and injection moulding properties. Saytex 8010 is not toxic, does not concentrate in bio-systems, meets the German Dioxin Rule, is effective at low loadings and does not disrupt resin properties. It is much more UV-stable than traditional products. Saytex BT-93 is also non-toxic and does not bioconcentrate. It meets the German Dioxin Rule and has excellent recycling properties. It is effective at low loadings so not affecting compound properties with again high UV stability. Saytex BT-93W is particularly useful in light coloured formulations. Saytex 102E meets the same criteria for utilisation in plastic compounds as the FR materials already mentioned. Albemarle offers a range of brominated polystyrene FRs, called Saytex HP-7010. Only in recent times has Albemarle, the source of Saytex brominated flame retardants, revealed more detail on the chemistry of some of their non-PBDE products. Saytex 8010 is ethane 1,2-bis (pentabromophenyl), or EBP, commercially available only from Albemarle. It was developed so that a brominated FR could be offered to the market that had a much-reduced likelihood to form dioxins or furans during any subsequent combustion. The key is the ethane bridge between the aromatic rings, versus an oxygen atom in decabromodiphenyl ether (decaBDPE). The spatial arrangement of the rings does not allow easy bond formation of the type necessary to produce dioxin or furan structures. EBP is a direct replacement for decaBDPE in many applications such as HIPS for electrical and electronic (E&E) products and offers performance benefits compared to the deca-compound in UV and thermal stability. It displays bloom resistance. UL94 V-2 is achieved with 8% EBP and 3% Sb2O3, while 12% EBP and 4% Sb2O3 is needed to reach a V-0 rating. Impact strength reduction compared to an untreated HIPS resin can be offset by the addition of around 3% of a styrene-butadiene-styrene (SBS) rubber impact modifier. For black E&E applications such as TVs the UV stability is no problem, but for lighter coloured goods this becomes an issue. An appropriate stabiliser and pigment presence is required. The presence of EBP also reduces the discoloration of HIPS after repeated cycles of regrind and further moulding and has little effect on mechanical, physical or flame retardant properties over this period. Saytex BT-93W can be used to flame retard PBT compounds for use in electrical connector applications. It is EBTBP, also called EBT for short, which is ethylene bis(tetrabromophthalimide). It is the only EBT on the market. It is compounded with antimony trioxide and provides excellent impact strength, tensile elongation and UV light stability. Typically an 11% loading is accompanied by 5% Sb2O3 to achieve UL94 V-0 rating. EBT also offers the best UV stability for HIPS at the V-0 level, where the most stringent colourfast requirements are imposed by OEMs. Both EPB and EBT can be used at lower loadings for a V-2 or in the Glow Wire Flammability Test (GWFT). However, other options exist that have a higher efficiency for V-2 or Glow Wire ratings. Saytex HP-900, hexabromocyclododecane (HBCD), or its stabilised version called BC-70HS, provides V-2 at a dosage of 3.3%.

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Flame Retardants for Plastics Market Report

Saytex HP-800 is tetrabromobisphenol A bis(2,3-dibromopropyl) ether and is also very efficient. 5% combined with 1% Sb2O3 typically results in V-2 or Glow Wire 960 °C rating at 1.6 mm. A new product for V-2 applications in both HIPS and PP is Saytex 2100. It has a bromine content of 70% and comes as a white powder or granules. In a stabilised form it can be processed at up to 240 °C in PP and 250 °C in HIPS. Typical loadings are 5% for V-2 HIPS or 4% for V-2 PP, plus 1% of Sb2O3 in each case. It provides good melt flow and impact strength, which are better than for EPB. It does not bloom from HIPS and shows less blooming from PP than other widely used FRs. Another new product is Saytex HP-7775. This is an extruded blend of brominated polystyrene (HP7010 from Albemarle) and Sb2O3 in a ratio of 77.5/22.5. It comes as dust-free, free-flowing granules. It provides outstanding thermal stability and electrical performance, making it ideal for polyamides and polyesters in electrical applications. It has excellent mechanical properties, flow, non-blooming and, not least, recyclability, all similar to the basic brominated polystyrene.

4.1.1.4 Ferro Corporation Responding to the need for thinner, smaller components in the electronics industry, Ferro Corp had developed an advanced brominated polystyrene flame retardant under their Pyro-chek name for high temperature glass-filled engineering polymers. Pyro-Chek 68Pbi is said to offer improved thermal stability and colour for high temperature applications. The product is suitable for both injection-moulded printed, circuit board mounted connectors as well as for compounders using larger extruders that operate at higher temperatures. The French unit of the company received much investment now enjoyed by the new owners, Albemarle. The facility houses a pilot plant facility which has been focussing on expansion of the portfolio for use in glass-filled polyamides and other grades for high temperature applications. Pyro-Chek 68Pbi was developed for use in high-temperature polyamide and polyamide-polyester alloys, but can also be utilised for faster compounding of PA66 in larger, hotter running, extruders. The material is available in powder and compacted form.

4.1.1.5 Unitex Chemical Corporation Unitex Chemical Corp. has entered the market with an identical product to Dead Sea Bromine's bromophosphorus product FR370. This is called Uniplex BAP 370. This particular FR is unique in that it frequently does not require any synergist present to provide good FR performance.

4.1.2 Chlorine Compounds Chlorinated fire retardants (CFRs) are utilised in polyamides, epoxies and PBT. The use of mixed synergists, that is antimony oxide plus another synergist, can lower the total loading of FR additives to the formulation. With glass-filled polyamide compounds where a higher processing temperature is sometimes required, the elimination of antimony oxide greatly improves the thermal stability of the formulations. Concerns about antimony oxide have led to a range of alternatives being explored across different families of polymer resins. Different zinc compounds and iron oxides have been found effective with CFR. Polyamide 66 formulations are UL94 V-0 down to 1.6 mm with 16% CFR, 4% zinc borate and 2% of either antimony oxide, zinc sulfide, zinc phosphate or zinc stannate. The most effective package is zinc borate with iron oxide. Here, only 12% CFR with 1.5% zinc borate and 1.5% iron oxide

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Flame Retardants for Plastics Market Report

gives a V-0 material. The latter formulation gives an electrical CTI result at only 350 volts. The best formulations for CTI have all zinc compounds as the synergists, giving 600 volts. Higher loadings are needed for glass filled polyamide compositions to achieve V-0 or V-1 in UL94 tests and the CTI levels drop to around 325-350 volts. Occidental Chemicals, or Oxychem, has long offered Dechlorane materials, one of which is designated Dechlorane Plus 25, sometimes just referred to as CFR. This contains 65% of chlorine and is a Diels-Alder adduct of hexachlorocyclopentadiene. 4.2 Phosphorus Containing Compounds

4.2.1 Introduction Most phosphorus based FRs tend to promote char formation, which gives several desirable benefits. The char is difficult to ignite, it acts as a barrier between polymer and flame, it restricts oxygen access, and it reduces the rate of heat generation. This works well for polyesters, PU and polyamides, but when it comes to styrenic polymers or polyolefins, there is often a need to combine phosphorus systems with other additives. Phosphorus chemicals can be compounded at up to 230 °C, comfortably higher than ATH. Also, moisture sensitivity is not a problem. However, although not ‘suffering’ from the problems that surround halogenated flame retardants, the view from outside the industry taken by environmentalists about the retardants based on phosphorus chemicals, may be influenced by the reputation of different organophosphorus chemicals in agriculture and other areas that have received somewhat adverse publicity.

4.2.2 Polymer Modification Flame retardants reacted with the polymer backbone usually provide protection at lower levels and thus have a smaller, usually malign, influence on the compound’s mechanical and physical properties. In the case of phosphorus-containing chemicals utilised for FR purposes, there exists a range of possibilities that are being explored. Vinyl and allyl phosphonates can be used as comonomers in addition polymers. Also, modifications of polymers with phosphorus-containing groups, such as phosphorylation of polyvinyl alcohol, leads to improvements in flame retardancy compared to the polymers themselves. Phosphorus-containing acrylates have adhesive properties as well as FR ones. Acrylates containing phosphonic acid groups have some interesting and encouraging properties. Other work has attached unsaturated phosphorus-containing compounds to unsaturated polyesters to improve their flammability. Such compounds enter into copolymerisation with the polyesters being modified at the curing stage. Glycol maleate phthalate polyester was copolymerised with a di-ester of methylphosphonic acid.

4.2.3 Red Phosphorus The safest and most convenient way of handling and processing red phosphorus (P-red), which is flammable in powder form, is the use of concentrates or masterbatches in a wide range of resin systems for a variety of applications. Quality standards are now being linked to the safety and environmental effects of the additives polymer compounds contain. Consequently the toxicity and environmental concerns about P-red have been under the spotlight recently.

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Flame Retardants for Plastics Market Report

Improved safety aspects as well as an upbeat classification for the product have given a boost to Pred chemistry in new applications. The material is now being introduced in polyolefin blends, HIPS and PBT, as examples. P-red is an active flame retardant as a single additive in nitrogen and/or oxygen containing polymers such as polyamides, polyesters, polyurethanes, epoxies, isocyanates and polycarbonates. It can be part of a package with carbon char-forming agents or metal hydroxides in olefins and styrenics. P-red is the most concentrated source of phosphorus, so it is an effective FR at a concentration between 2 and 10 wt% of the polymer resin. It is generally used for meeting highly demanding flammability requirements, reducing the formation of toxic smoke and providing good electrical properties, such as high CTI values, with good mechanical characteristics. Restrictions on its use are now only on the basis of colour, since it cannot be used for white or light coloured end products, but it is widely applicable for items from black to medium grey and some dark reds and browns. High thermal stability enables P-red to withstand an extrusion temperature of up to 320 °C without decomposing and be particularly suitable for polyamides. During combustion, the combination of the phosphorus with oxygen and nitrogen in the polymer produces intermediates that then recombine to make an extended char layer as the flame retardant proponent. It has been usual to microencapsulate and coat P-red, but even with this pre-treatment, the powder is still flammable and can become a hazard during handling. It is now more accepted to prepare Pred in masterbatches for a range of polymers. When P-red is completely encapsulated in a polymer matrix it cannot react with air or water. Improved techniques in the production process and increased expertise in compounding now prevent the possibility of forming phosphine, which in any case is rapidly oxidised to form harmless phosphates. In a fire or during waste incineration, P-red is easily oxidised to phosphorus oxides, which do not lead to phosphine production. The phosphorus oxides remain as polymeric phosphoric acid or phosphates in the bottom ash or can be removed in the flue gas treatment system of incinerators. The German Federal Environmental Agency defined P-red use as unproblematic (like ammonium polyphosphate (APP) and ATH) in its risk assessment report on the most commercially important FRs in August 2001. One company that is involved with P-red compounding is Italmatch Chemicals of Genova (Genoa), Italy. Developments by the company have increased the efficiency of stabilisation of the element to such an extent that they estimate that three orders of magnitude less formation of unwanted species, such as hydrogen phosphide or phosphoric acid, occurs during high temperature compounding or processing in the presence of high moisture. This change in the perception of P-red grades has been carried forward to new grades that increase the range of applications into previously under-considered resins. Loadings of 10-12% of Masteret 90450 from Italmatch in a 30% glass reinforced PBT achieve V-0 at 0.8 mm in UL94 and a CTI of 600V with maintained mechanical properties and hydrolytic stability of the compound, even in the most severe tropical conditions. P-red is also effective for unloaded polyolefins of all types. UL94 V-2 can be achieved at 3.2 and 1.6 mm and the formulation using grade M15460 B2XF at 7% is competitive against standard halogen-based systems as well as other halogen-free ones. After-burning time is short and B1 classification is possible in the German standard DIN 4102. However, FR activity is not sufficient to obtain V-2 in a talc filled compound.

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Flame Retardants for Plastics Market Report

In addition, P-red is effective with synergists to reach V-0 in polypropylene. It has to be used in combination with a nitrogen-containing compound at a total loading of 20-25%. The same approach can make HIPS compounds flame retardant to V-0 at 1.6 mm as the requirements for TV sets now demand at least a V-1 rating due to safety regulations becoming more stringent.

4.2.4 Ammonium Polyphosphate Ammonium polyphosphate (APP) is a fine-grained non-toxic white powder with average particle size of 8µm or 15µm depending on grade. It uses the intumescent effect for flame retardancy. The flame retardant material foams on exposure to heat or flames. The carbon foam layer protects the host polymer structure through its heat-insulating effect and reduces further oxygen access to the polymer fuel. This is generated by an acid dehydration of the polymer.

4.2.5 Phosphorus Oxynitride Phosphorus oxynitride (PON) is the name for a family of closely related materials that have been around for over 100 years. They are not well known but are thermally very stable and may be considered as future flame retardants and for intumescent formulations since PON is analogous to ammonium polyphosphate. It can be made from inexpensive starting materials such as ammonium phosphate, melamine phosphate or urea phosphate just by prolonged and intensive heating. Work in Belarus in collaboration with the Polytechnic University of Brooklyn has verified the claims for use in polyamide systems but has indicated a less successful outcome in PBT compounds. PON prepared by heating phosphoric acid with urea and melamine to 750 °C, is an efficient fire retardant additive for polyamide 6. It increases strongly the oxygen index (OI), and in combination with ferric oxide provides V-0 classification under the UL94 test. However, PON only slightly increases the OI of PBT, either alone or in combination with other additives, and has no effect on the UL94 performance. PON promotes extensive charring in both PA6 and PBT, so different mechanisms are believed to be at work in the two polymers. Upon thermal decomposition in the presence of PA6 and probably of water evolved from the polymer, PON transforms into polyimidophosphoric acid, which reacts with PA6 producing phosphoric esters. Intumescent char is formed by thermal decomposition of the esters. Thus PA6 is involved in the charring. In the case of PBT, the charring occurs because of retardation in the volatilisation of terephthalic acid fragments due to the formation of ammonium or amine salts. However, the preferential evolution of highly combustible aliphatic fragments observed at the initial stages of the thermal decomposition of PBT+PON probably works against the flame retardant effect provided by the char.

4.2.6 Albermarle Corporation Albemarle Corporation has introduced the first of their new NcendX range of halogen-free flame retardants, which widens their portfolio into phosphorus-based products. NcendX P-30, the company’s new non-halogenated FR for PC/ABS blends and modified PPO, comes from a new plant in the US. The new material is expected to be used in the market for halogen-free plastics used in office automation and computer equipment. It is regarded as an excellent complement to the company’s Saytex brominated products for this same market. P-30 is bisphenol A diphenylphosphate (BPADP).

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Flame Retardants for Plastics Market Report

NcendX P-30 offers excellent hydrolytic stability and low bloom for resin producers and compounders. It is a colourless liquid, ideal for colour-critical applications. It provides excellent UV stability, improves resin flow and has low volatility plus outstanding thermal stability.

4.2.7 Polymer Tailoring Sometimes phosphorus systems do not work as well with other additives as they do without. An example is the Antiblaze (formerly Amgard) NK and NP grades, which can be less effective with zinc borate-based smoke suppressants than without. The additive pentaerythritol has been known to cause problems in intumescent systems with the same grades. NK and especially NP, which are used typically with loadings up to 30% of resin weight, usually tint the product. Amine oxides form on the surface, but processing at lower temperatures can moderate the tendency. White shades can be produced by using fine grades of titanium dioxide. Colouration may also be reduced by adding antioxidants, such as a phosphite/phenolic blend, or a triazine hindered phenolic. Dispersion of NK and NP in polyolefins is not straightforward because of the polarity of these grades, so a silane coupling agent is recommended. The silane partially restores the elongation at break of PP, which can otherwise be drastically reduced by the FR, although impact strength as measured by Izod tests are maintained. The global manufacturing and marketing of Antiblaze NP and NK have been taken over from Rhodia Consumer Specialities by Polymer Tailoring.

4.2.8 Akzo Nobel Chemicals Fyrolflex RDP is a resorcinol bis(diphenyl phosphate). It is a liquid that is designed for use in engineering plastics such as polyesters, modified PPO as well as PC/ABS blends and HIPS. It has low volatility and good thermal stability, meaning it can outperform triaryl phosphates, such as triphenyl phosphate. Fyrolflex RDP is used either as a flame retardant or, in low doses, as a flow modifier. Fyrolflex BDP from Akzo Nobel Chemicals has been shown to exhibit higher thermal properties and hydrolytic stability than other aryl phosphates, and to provide similar or better fire retardant performance than RDP. It is a bisphenol A bis(diphenyl phosphate) compound that provides good physical properties in formulations based on PC/ABS, HIPS and polyphenylene oxide/HIPS blends. Upon thermal decomposition of the flame-retarded polymers, phosphorus tends to accumulate in the solid residue, a result which indicates that the primary FR action of BDP is most likely to be in the condensed phase. Akzo Nobel has expanded its production of Fyrolflex BDP. Fyrol BDP would appear to compete with Albemarle’s move into phosphorus-containing materials, called NcendX P-30. To replace the pentabromodiphenyl ether that has been used in furniture foam but is now to be phased out under current regulations, Akzo introduced an all-phosphorus FR for flexible polyurethane foam. Fyrol PNX contains 18% phosphorus, which permits a lower loading in the formulation.

4.2.9 Great Lakes Chemical Corporation For use in flexible polyurethane foam, Firemaster BZ-54 from Great Lakes Chemical Corporation is available. Compared with conventional chlorinated phosphate esters, it requires smaller loadings and has lower plasticisation effects. Foams incorporating BZ-54 show low scorching when using alternatives to freon-type blowing agents. It is also ideal when using flame bonding to prepare foam laminates.

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In addition Great Lakes has expanded its range of non-halogenated phosphorus-containing materials. New to the Reofos range are bis(4-aminophenyl) phenyl phosphate (BAPP), a bisphenol A diphosphate and 507, a butylated triaryl phosphate. Both of these materials are designed for use in polycarbonate/ABS and polyphenylene oxide (PPO)/HIPS mouldings, such as computer housings and monitors. The two Reofos additives are claimed to overcome the problem of stress cracking, plate-out and juicing often associated with the utilisation of flame retardants in polymer blends. They have a high degree of hydrolytic stability, which is increasingly important with the growth of component recycling. A more recent addition is Reofos NHP, a low-fogging additive for hot-moulded polyurethane (PU) foam for automotive seats. This material offers an alternative to chloroalkyl phosphates to meet the MVSS 302 standard. An intumescent flame retardant has been recently introduced by Great Lakes. CN 2626, Reogard 1000, is a nitrogen and phosphorus-containing FR aimed at injection moulded polypropylene. It is melt blendable at PP’s processing temperature and is said to increase the HDT of the compound. It is non-blooming, has good electrical properties and has a reduced tendency to absorb water. It is recommended for use in V-0 PP homopolymers and low PE-content copolymers for a range of E&E, appliance and mass transit applications.

4.2.10 Clariant Exolit flame retardants from Clariant do not use halogens to produce flame retardancy. They have a low smoke density and produce non-corrosive gases. Exolit materials can be combined with light stabilisers to provide good UV stability in flame-retarded plastics. The Exolit AP series for thermosets is used in combination with ATH to allow manufacturers to use UP and epoxy resins in lightweight components for trains and buildings. Exolit AP 750 is used in polypropylene injection moulding for the electrical and electronic sectors. When combined with hindered amine light stabiliser (HALS)-type UV stabilisers, it has good resistance to discoloration and embrittlement of FR-treated polypropylene items. External applications include stadium seating. Exolit AP 751 has been especially developed for glass-fibre reinforced PP. The addition of around 30% of AP 751 to a 20% glass by weight PP can achieve flame retardancy to UL94 V-0 level. Exolit AP 752 is a special grade with particularly low water solubility and high acid resistance, even at elevated temperatures. Exolit OP products are liquid phosphorus polyols for polyether flexible and slabstock moulded foams. They are used in the automotive sector as reactive fire retardants with low fogging values and high resistance to migration. Exolit OP 1311 (TP) is used for injection moulding nylons. This new grade yields a UL94 V-0 rating at 1.6 mm, at 15% content in a 25% glass filled compound. The additive is a white powder, which is heat stable up to 310 °C. Exolit RP products are effective red phosphorus-based materials for applications where the highest flame retardancy is required with the lowest amount of additive, and the properties of the polymer are to be impaired as little as possible. RP grades are available as concentrates to allow for easier processing. Clariant has introduced new products based on their phosphonic acid metal salt technology that has been under development for some time. This technology is aimed at engineering resins, the first of which has been polyamides, and can be added at around 15% loading. This makes it more cost effective than red phosphorus and even some brominated FRs used for the same applications.

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Flame Retardants for Plastics Market Report

4.2.11 Other New Developments Ferro Corporation purchased the phosphate ester business of Solutia in 2001 and incorporated the Santicizer plasticiser line into their own product range. Unitex Chemical has introduced Uniplex FRX 47-88, an alkyl diphenylphosphate FR plasticiser. This complements the existing Unitex offerings of Uniplex FRP 45, a brominated dioctylphthalate (DOP), and Uniplex FR 44-57, a brominated chlorinated DOP for low temperature plasticiser applications. Polyurethane-phosphate combinations are known to form flame retardant intumescent systems. However, the intumescent formulation cannot be permanent because of the water solubility of the phosphate. This problem could be solved by the technique of microencapsulation. Microcapsules of diammonium hydrogen phosphate (DAHP) with a PU shell are synthesised. Cotton fabrics can be coated with PU formulations that enclose the microcapsules and show a significant FR effect. 4.3 Inorganic Minerals and Compounds Some industrial minerals possess properties of flame retardancy and can be used in systems to replace chemically prepared flame retardants. Hydrated alumina, magnesium hydroxide and borates release water endothermically and create dilution in the gaseous phase, as is well-known. Several minerals have a synergistic effect on organic halogenated and phosphorus-containing flame retardants. In thermoset materials synergistic processes have also been observed, between borates and other hydrated minerals. Minerals can be incorporated into intumescent formulations to manage better the morphology of the expanded structure that develops on exposure to flame. With brominated flame retardants, a partial substitution with minerals can lead to an improvement of mechanical properties and reduce the opacity and corrosivity of the fumes generated. This in turn makes it possible to reduce the environmental hazards arising from the incineration of such fumes.

4.3.1 Antimony Trioxide Antimony trioxide is supplied as >99% purity white powder having specific gravity in the range 5.3 to 5.8. Some dusting does occur in the normal process of handling the material but the high specific gravity causes fairly rapid settling of the dust. Nevertheless, environmental regulations relating to dust problems associated with the use of antimony trioxide have promoted the introduction of nondusting grades, both of the damped and free flowing type. The impurities, typically iron and arsenic depending on the source, influence the colour of the oxide and may also affect the colour and stability of the plastic matrix. A major consideration in the selection of the appropriate grade of antimony trioxide to be used in any particular application is the effect of particle size on physical properties, dispersion and colour. A variety of grades are commercially available with average particle sizes in the range 0.3 µm (ultrafine) to 10 µm (coarse), with most companies offering intermediate grades specified as high tint (average particle size 1.3 µm) and low tint (average size 2.8 µm). The high tint grades produce a whitening effect at lower concentrations than the low tint grades and are therefore useful in light coloured compounds, since less white pigment is required. In dark coloured compounds the less expensive low tint grades are to be recommended since less colour pigment will be required. As expected the coarser the grade of the filler the greater is the detrimental effect on physical properties. The greatest effect is a reduction in the impact strength; the magnitude depends on both the particle size and the loading. As noted, antimony trioxide requires the presence of an organic halogen compound to be effective as a flame retardant, and, therefore, consideration must be given

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Flame Retardants for Plastics Market Report

to the effect this product has on colour and physical properties. In certain formulations the effect of the halogen compound may be predominant. Great Lakes has introduced new products based on antimony oxide. These are Fyrebloc 100 and Fyrebloc 101. These materials are 100% active flame retardant formulations using a halogenated FR carrier that has a high flow performance and excellent thermal stability. Because the carrier already incorporates bromine, subsequent formulations require less halogen than would otherwise have been necessary. These concentrates are pellets that eliminate the problem of dusting normally associated with antimony oxide, making them particularly suitable for use in pneumatic feeding systems. In essence these products have been introduced to make FRs easier to use. They allow faster production rates in compounding machinery due to their pre-dispersed nature.

4.3.2 Alumina Trihydrate (ATH) The flame retardancy mechanism of ATH is based on its thermal decomposition reaction. Between 200-400 °C ATH decomposes by giving off its chemically bound water and generating the corresponding aluminium oxide. This decomposition reaction is an endothermic (energy consuming) one. As a consequence, heat energy is removed from the burning zone. Generated steam cools the compound surface and dilutes the atmosphere immediately surrounding the surface by lowering the oxygen content and the concentration of burnable gases formed by thermal decomposition of the polymer matrix. The aluminium oxide formed has a high specific surface, which absorbs smoke and other, partially toxic, carbonised decomposition products. Processing aids affect resins containing metal hydrate FRs. In polypropylenes it would appear that fatty acid coatings are more effective than silane coatings as processing aids. Increasing amounts of metal stearate coatings provide processing benefits. The mix of reacted stearate and the addition of calcium stearate to the formulation is as effective as all other stearate coatings. They reduce the amount of work done on the resin during the mixing preparation and so reduce the degradation that takes place in the polymer. As may be expected, with increasing stearate content the final compound becomes less stiff and processing becomes easier. To allow ATH filler loads above 100 phr specially designed fillers are necessary. Unfortunately, fine fillers have very large surface areas that makes wetting quite difficult even with specific wetting and dispersing additives. However, judicious blending can prepare filler loads up to 300 phr with acceptable viscosities for moulding and pultrusion, for instance, with resins like dicyclopentadiene or modified methyl methacrylates. A blend with a broad particle size distribution from 1 up to 20 µm with a median of 4-8 µm could be used up to 300 phr and still give a low viscosity increase. It is important to have the correct wetting and dispersing additive in combination with an anti-settling additive. These should provide for optimal filler wetting plus a stable resin matrix to ensure long shelf life without sedimentation and/or viscosity increase, plus excellent air release from the mix on processing since large amounts of air tend to become entrapped during dispersion. Alcan Chemicals is one of the leading suppliers of alumina trihydrate, or aluminium trihydroxide as the company call their Baco ranges of fillers. They can be surface coated specifically for the polymer system under consideration. The Baco FRF range comprises general-purpose materials with median particle size ranging from 80 µm to 5 µm. The Baco FRF LV products give lower viscosity and range in particle size from 55 µm to 5 µm. Particle size distribution is closely monitored so that significantly higher loadings can be achieved than for the standard FRF grades. Much finer products are also available with median size well below 5 µm. These are the Baco Superfine and Baco Ultrafine products. The former cover materials with controlled surface areas from 4 to 11 m2/g and the latter from 15 to 35 m2/g. Each range can be offered as ‘E’ grades that

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Flame Retardants for Plastics Market Report

have been specifically prepared for electrical applications where low electrolyte levels are essential. Martinal aluminium hydroxide based mineral additives from Martinswerk are claimed to be environmentally friendly and have processing temperatures of up to 200 °C. For use in thermosetting plastics and elastomers, products with a medium particle size are recommended. These grades are produced by grinding coarsely precipitated aluminium hydroxide. Earlier developments of ATH products had concentrated on filler purity and electrical properties for the wire and cable industry, but more recent improvements have been in response to a growing importance of continuous compounding techniques. The very fine precipitated ATH fillers used in these applications have some drawbacks. Although the SG of ATH is 2.4, fine precipitated grades have much lower bulk densities. These low bulk densities in combination with strong attractive forces between the finely divided filler particles lead to poor flow properties and bridging. Poor flow ability and low bulk density restrict output rates on continuous compounding equipment because of bad conveying and dosing behaviour of the powder. Large volumes of air that are entrapped by the melt via low-density fillers have to be removed during compounding. The wire and cable industry, for instance, looks for formulations that are easily extrudable and show good physical properties. Low smoke, no halogen compounds are restricted in their extrusion speeds due to the high addition levels of ATH fillers needed to fulfil the FR requirements. Improvements to powder handling and rheological properties of the compound have been achieved by chemical post-treatments of precipitated ATH products. While giving the anticipated benefits in powder handling, mechanical and, more importantly, electrical properties have been detrimentally affected. In addition, the chemical nature of the various coatings utilised restricts the width of application of such products. Some suppliers have tried physical compaction. This leads to better handling but does nothing with respect to the consequent physical compound properties; especially melt viscosity which is so important for extrusion. One company has now commercialised a new generation of non-post treated fine precipitated ATH, which has excellent processing behaviour and provides outstanding final-compound properties. Especially notable are the low melt viscosities and high extrusion speeds achieved for cable manufacture. Customers had stated that inconsistent density was as much if not more of a problem than lower bulk density as such. The company, Nabaltec GmbH, already had a compacted product designated Apyral 40D. This gave better handling characteristics than a non-densified product Apyral 40E. However, Apyral 40D changed density during transfer to the compounding lines. The new generation as exemplified by Apyral 40CD does not show this drawback (CD stands for ‘consistent/constant density’ while D stands for ‘densified’). Apyral 40CD shows good discharge and metering properties as well as outstanding conveying and dust behaviour. Highly filled LSZH compounds with around 60% ATH produced with this new FR show very good mechanical properties, as well as outstanding melt flow and rheological properties. This performance is essential for wire and cable production and for the compounding sector as well.

4.3.3 Boron Compounds As multifunctional flame retardants, zinc borates can provide the following benefits in polymer systems:

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•

They can function as a flame retardant, smoke suppressant, afterglow suppressant and as an anti-tracking agent.

•

They can display synergistic/beneficial effect with other synergists or additives such as antimony oxide, ATH, magnesium hydroxide, red phosphorus and ammonium polyphosphate in both halogen-containing and halogen-free polymers.

•

The choice of optimal synergistic combination depends on the base polymer and halogen source used. That is additive vs. reactive approach and aromatic vs. aliphatic halogen source.

•

Zinc borates alone can function as flame retardants in some polymers.

Alcan Chemicals make and supply Flamtard Z, which is a series of zinc borate materials with surface areas from 10 to 15 m2/g. They are stable up to 290 °C and promote the formation of a char in the condensed phase. Flamtard Z grades have finer particle sizes than so-called standard zinc borates. Back in 1970, US Borax first showed that a unique form of zinc borate could be an effective flame retardant synergist in plastics and rubber formulations. Firebrake ZB, the company’s product has a molecular formula of 2ZnO.3B2O33.5H2O and is stable up to 290 °C, thus it can be used at high processing temperatures. Its refractive index of 1.58 is similar to most polymers, which means that it retains considerable translucency while allowing the use of lower pigment loadings. The material, as developed, is an effective synergist that is multifunctional and cost effective. It replaces antimony oxide and, by contrast, is a smoke suppressant, after-glow suppressant and antitracking agent. Polymer applications include PVC, polyamide, epoxy, polyolefins, polyesters, thermoplastic elastomers and rubbers. In halogen-containing systems, the usage level is in the range 3-25 pphr. In halogen-free systems, the recommended level is in the range 10-250 pphr, normally used in conjunction with ATH, magnesium hydroxide or a silicone polymer. In halogenfree systems the borate is usually formulated with alumina trihydrate, magnesium hydroxide or red phosphorus. Firebrake ZB has a typical particle size of 7 µm and has been used extensively as a partial replacement for antimony oxide in flexible PVC used for wall coverings, wire and cable, roof membranes, conveyor belts, carpet backing, vehicle upholstery, tarpaulins and tent fabrics. The fine-grade version, Firebrake ZB-Fine has a smaller particle size around 3 µm and has been used in polyolefin wire and cables plus electrical components. In PVC partial replacement of antimony oxide not only provides synergy for flame retardancy, but also improves smoke reduction, which can be enhanced by addition of ATH. Just as important, due to antimony oxides costing more, partial replacement by zinc borate can result in considerable savings on cost, usually between 30 and 60%. Total replacement of antimony oxide in the presence of a halogen containing system is possible. In polyamide, Firebrake ZB plus a compound like OxyChem’s Dechlorane Plus maintains a V-0 rating in the UL94 tests. In a halogen containing system, Firebrake ZB works as follows: during combustion, the zinc component of the material catalyses the decomposition of the halogen source to promote crosslinking and char formation. The borate component forms a glassy layer on the char to protect the char from being further oxidised, it prevents any afterglow combustion. This strong char can also prevent burning drips, and the water given off can cool the flame and promote the formation of a highly foamy and insulating char. The product also works in non-halogenated systems. It can be used with ATH, MgO, ammonium polyphosphate, silica, silicone polymers or melamine compounds in polyolefins, urethanes, polyamides and others. In the silicon containing systems, Firebrake ZB is understood to form a borosilicate glass at polymer combustion temperatures.

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Borates with zinc, calcium, magnesium, melamine or barium as the cation, combine char formation with endothermic decomposition as a dual mechanism that provides an efficient flame retardant system. Although the exotherm reduction is not as great as that achieved with ATH, there is enough endotherm to delay the initiation of the polymer exotherm by as much as 100 oC in some systems. It is this endothermic reaction in the polymer condensed phase and the formation of a glassy char that makes borate products good synergists with the fire retardant antimony trioxide. 80% of the boron from zinc borate remains in the char after PVC combustion. As seen above, boron compounds, specifically inorganic borates, are currently used in some plastic formulations as flame retardants but they are plagued by poor melt blendability, which weakens the polymers’ mechanical properties. Boronic acids are known to release water upon heating, leading to boroxine or boronic acid anhydride structures. These materials, if they contain more than one boronic acid functionality, may form a network polymer system. Specifically, they may form a boroxine network that could lead to high char formation upon burning. Work at South Carolina University has developed a method to make boronic acid flame retardants using a nickel catalyst and pinacol borane. Their use in polycarbonate results in V-0 rating in the UL94 flame test. Joseph Storey, part of Banner Chemicals offers zinc borates, which have good fire retardant properties with low toxicity, smoke suppression, anti-dripping and afterglow performance, comparable to other materials in terms of char formation. Up to 50% of antimony trioxide can be partially replaced in many halogenated systems. With alumina trihydrate, boron char formation provides integrity to highly filled halogen-free formulations. Smoke performance in phosphate systems can be improved using zinc borate. Recent work has shown that magnesium borate provides good surface spread-of-flame performance in PVC, suggesting the possibility of direct antimony replacement. A zinc-free borate has stability advantages in PVC sheeting. Melamine borate is another recent development and is used in phenolic composites to improve fire performance. Zinc borophosphate is also a new development for applications as a smoke and flame retardant in PVC. In recent years, due to the demand of high production throughput and thin-walled electrical parts, engineering plastics are being processed at increasingly higher temperatures. To meet the market demand of such plastics, US Borax has in recent times developed products to cope with greater temperatures than Firebrake ZB. Firebrake 500 is an anhydrous zinc borate (2ZnO.3B2O3) that is stable to at least 450 °C and Firebrake 415 (4ZnO.B2O3.H2O) that is stable to about 415 °C. Firebrake 500 is recommended for use in engineering plastics processed at above 300 °C, which is the upper limit of Firebrake ZB. It is reported to be an effective smoke suppressant in fluoropolymers for certain cable applications. This anhydrous material can replace antimony oxide completely in high temperature nylon applications. For aircraft applications Firebrake 500 is also reported to be effective in reducing the rate of heat release in polyether ketones and polysulfones. It is also claimed to enhance laser-marking quality of flame-retardant engineering plastics. Firebrake 415 has an unusually high onset of dehydration temperature of >415 °C. It is recommended for use in engineering plastics as a synergist of halogen sources. It can also be used as a smoke suppressant in flexible PVC. Firebrake 415, increasingly replacing magnesium hydroxide in an EVA formulation, can bring about a reduction in the rate of heat release. Keeping total loading at 60%, the more borate present, the greater the elimination of surface cracking in the resultant post-combustion residue. This prevents the escape of volatile gases and so reduces the quantity of combustible material from reaching the combustion zone. Firebrake zinc borates display an interaction with metal oxide particles resulting from dehydrating metal hydrates in flame retardant polyolefins. The interactions taking place show that surface

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fracturing, mechanical strength of the degrading residue as well as the viscosity of the degrading polymer surface can be significantly influenced by zinc borates. These phenomena should be useful when devising improved flame retarded polyolefin materials based on magnesium hydroxide FRs. The traditional use of zinc borates as a partial replacement for antimony trioxide and to increase CTI can be extended to polyamide 66 compounds that contain brominated FRs. Their benefits can expand to complete antimony trioxide replacement and improved melt stability during compounding and injection moulding. Firebrake ZB and a brominated polystyrene, such as Pyrochek 68PBI or Saytex HP-7010, can provide a highly flame retardant PA66 formulation containing 25% of glass fibre reinforcement, without the presence of any antimony trioxide. 24% loading of the brominated FR plus 7% of the zinc borate produce V-0 at 0.8 mm in the UL94 test, with a CTI of 450 volts. In general, the structure of borates is known to have anti-corrosive properties and secondary antioxidant properties in polymer FR systems. Possible benefits of these zinc borates in FR polyamide systems could be in reducing tool corrosion during compounding and moulding and imposing better oxidative degradation resistance. Borate structures are known to absorb infrared radiation with possible implications for laser marking properties of polymers. These properties have not been much explored and potentially open the way to wider applications for borate additives in polymer systems. Continuing work by Borax Co. has explored other ‘third-party’ additions to metal hydrate–borate combinations as FR packages. Silicone as an extra ingredient to a magnesium hydroxide and Firebrake ZB flame retarded EVA reduces the peak of heat release rate, for a total loading of 65%. It has been found that the residue for samples with zinc borate and the silicone is multicellular, rigid and hard compared to that with silicone and magnesium hydroxide alone. This shows how combinations of additives can be used to influence the morphology of the degrading residue and subsequently lower the peak rate of heat release. A small amount of Melapur 200 (melamine polyphosphate) with a metal hydrate leads to a strong reduction in the rate of heat release. The combination allows a lowering of the loading to 50% instead of 65% and still retains the same peak rate of heat release as with 65% magnesium hydroxide in EVA. The effect of Firebrake ZB has been shown to further reduce the overall level of heat release and create a hard, cellular protective structure. In vertical burn tests like UL94, however, this structure is not created and leads to a loss of classification. Current work is endeavouring to improve vertical burning behaviour of these formulations. Zinc borate (ZB) added to an ATH/nanoclay combination can convert a V-1 classification at 1.6 mm in UL94 to a V-0 rating. 5% of ZB replacing some of the 60% ATH present in EVA with 5% nanoclay has been reported.

4.3.4 Magnesium Hydroxide 4.3.4.1 Technology Magnesium hydroxide is an effective mineral flame retardant. Metal hydrate compounds provide effective flame retardance by several routes. First, they dilute the amount of fuel available to sustain combustion during a fire. They contain a significant amount of bound water (31% in the case of magnesium hydroxide) that is released at high temperatures (> 330 °C for Mg(OH)2) providing a blanket effect that limits the oxygen available for combustion. Magnesium hydroxide decomposes endothermically at about the same temperature as that at which the host polymer degrades during combustion, absorbing heat from the combustion zone, which reduces the prospect

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Flame Retardants for Plastics Market Report

of continued burning. It produces a char during burning that results in further flame retardant protection and less smoke generation. Magnesium hydroxide also generates a magnesium oxide coating during combustion, which deflects the flame’s heat away from the polymer or fuel source. It is also a good smoke suppressant. The addition of 9% to polystyrene reduces the maximum smoke density in the NBS Smoke Chamber from 2556 to 375. In a test on an EPDM compound, a mixture of 75% magnesium hydroxide and 25% ATH produced significantly less smoke than ATH alone in Smouldering Mode NIST (ASTM 2843) smoke chamber testing. Magnesium hydroxide is low in toxicity and non-corrosive compared with halogen or phosphorus containing compounds. Magnesium hydroxide has several advantages over ATH. It has a lower hardness, which results in longer processing equipment life. It produces more char than ATH, absorbs significantly more heat from the combustion zone and allows for processing at temperatures up to 100 °C higher. The latter can improve processing efficiency by increasing extrusion speeds and decreasing mould filling times. The main problem with the use of metal hydrates is the need for high loadings of the filler in the compound formulations. Up to 60% by weight is usual, with differing Oxygen Index values being obtained depending on the exact nature of the hydroxide employed. This may reflect particle size distribution, the presence of a coating or other factors. The main sectors for magnesium hydroxide use are in elastomers and thermoplastics, since they cause excessive thickening in the main thermoset application of unsaturated polyester systems. It is also much more expensive than ATH with which it shares comparable properties and flame retardancy, and so ATH will be preferred by processors wherever possible. As a result the principle opportunities are in applications where the extra thermal stability is essential, mainly in PP and polyamides. Polypropylene and polyamides have much more rigid particle size and shape requirements than thermosets. Specifically, the need is for a small particle size, with a low aspect ratio and minimal surface area. The particle size distribution should also allow for good packing, as indicated by a relatively low level of oil absorption in tests. Achieving such desired particle morphology has been the main aim of supplier process development since the 1980s. In principle, there are a variety of routes to generate a desirable form of magnesium hydroxide. These range from milling of naturally occurring forms, such as brucite, to precipitation and recrystallisation techniques. The target or guide is the property envelope of a typical finely precipitated ATH as shown in Table 4.2. Table 4.2 The effect of manufacturing processes on the morphology of magnesium hydroxide Average particle size Specific surface area (m2/g) (µm) Desired range 1-8 0.5-5.0 5 30 Milled Brucite 6 10 2 18 4 Precipitated magnesium hydroxide 12 50 2 6 1 Precipitated and hydrothermal 2 3 Hydration of specially made oxide 3-10 1-3 Source: R.M. Rothon, Flamemag International, reproduced with permission.

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This shows that only the hydrothermal and hydration techniques allow production of the optimum particle morphology and these are the ones now in commercial production. There are also purity considerations involved with the milled natural products and in the choice of oxide as the starting material for the hydration process. A major drawback, however, is that the suitable processes are the most expensive and, with the moderate scale of the sector this has led to the high prices of magnesium hydroxide. Metal hydrate FRs affect the polymer matrix in many ways. Firstly there is melt flow index (MFI). This is significantly reduced with increasing filler level. Tensile strength is also affected, but not nearly so much. The MFI of a 7 MFI polypropylene resin drops dramatically, above about a 45% addition level of magnesium hydroxide the MFI has dropped to 2.2. To achieve higher loadings without excess degradation of the polymer, then a higher MFI resin should be employed. To reach a 65% loading in an EVA system, which enables a high LOI of 40 to be achieved, then a resin with an MFI of over 100 is required. Efforts to make magnesium hydroxide more appealing for use in PP compounds have focussed on techniques for surface modification of fillers and the polymer resin to make compatibilisation better and so allow a higher level of mineral filler without sacrificing impact and other properties. Stearate coatings appear to be one route forward, giving increased melt flow and much increased impact properties for a 60% filled compound. Fatty acids are extensively used as surface treatment systems for particulate mineral fillers. As well as improved dispersion, reduced melt viscosity results in lower shear degradation. Mechanical properties are affected through fatty acid treatments. Fatty acids reduce adhesion between filler and matrix. In highly filled compositions this reduction usually leads to an increase in toughness accompanied by a decrease in ultimate strength, particularly in materials that do not yield or undergo strain-induced crystallisation. Unsaturated fatty acid oligomers, such as oligomerised oleic acid, are becoming increasingly available. Oligomer acids are claimed to be more effective than simple fatty acids for the treatment of ATH and magnesium hydroxide for use in FR polypropylene compounds. Ricinoleic acid, made from castor oil, is also said to be effective in this application. Another modification for FR PP compounds is an in situ interphase modification system based on phenylene bismaleimide (BMI). A 60% w/w filled PP so treated has a failure stress greater that that of the unfilled matrix and a failure strain almost matching the yield strain of the unfilled matrix. Flame retardant performance can be enhanced in some magnesium hydroxide protected systems by the incorporation of clay or talc. In a polyethylene formulation the addition of 60% magnesium hydroxide and 5% talc instead of 65% magnesium hydroxide, improved the V-0 rating from 3.2 mm to the thinner 1.6 mm level. More talc at the expense of further magnesium hydroxide dropped the V-0 rating back to 3.2 mm. Two routes to lowering costs have been reported. The first is to improve the FR efficiency of magnesium hydroxide so that less is required in a compound. One of the methods investigated is to incorporate small quantities of other metals during the hydrothermal process. This is said to aid char formation. Another has been to find co-agents to boost the performance. Japanese companies Kyowa Chemical and Kabushiki Kaisui KK have been involved in this work. The second route has been to improve the process economics to make the appropriate materials in the first place. Flamemag International has gone down this route and claim to have significantly improved their hydrothermal process. The proven success of one or more of these approaches is needed before there is a surge in consumption of magnesium hydroxide for flame retardant purposes.

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4.3.4.2 Commercial Products Martin Marietta Magnesia Specialties offers in-process coated magnesium hydroxide grades that facilitate processing and improve the physical properties of the final compounds. When coated in process, which reduces costs, the company puts a stearate coating on the hydroxide particles before they leave the production equipment. This differs from post-coating, which is done by coating the often-agglomerated particles, after their preparation. The Magshield coated products include standard and ultrafine grades with 1%, 2% and 3% stearate coatings, designated NB10, NB20 and NB30. Martin Marietta has a databank of formulations developed on both small and commercial sized plant, which enables a user to compound their Magshield products into polyolefins and polyamide systems. Martinswerk of Germany said that its Magnifin flame retardants have been specifically created for applications as flame retardant additives, compared with other magnesium hydroxides that have been manufactured from seawater with the pharmaceutical industry in mind. Magnifin is especially recommended for situations where low smoke emission and a high thermal stability are required from a halogen-free retardant. Specific filler surface has an increasingly beneficial effect across a range of properties. Limiting oxygen index has been shown to rise from 40 to 50 in an EVA formulation filled with 150 phr of magnesium hydroxide, as the filler particle surface area has gone from 5m2/g up to 10m2/g. Martinswerk has developed a proprietary coating for magnesium hydroxide that enhances various properties including flame retardancy. Coating of magnesium hydroxide particles with surface area of 5m2/g raises the LOI right up to 80. Albemarle now owns Magnifin products. Special grades, with a surface treatment, are now offered for polyamides. Magnifin H5 IV and Magnifin H10 IV are synthetic grades with a specific BET surface of 5 and 10 m2/g and a mean particle size of 1.45 m and 0.8 m respectively. They do not affect the colour of the product and are non-blooming fillers. The Magnifin products can contain around 10-15% glass fibre and about 30-55 wt% of flame retardant. Depending on the PA grade, a loading of about 55 wt% gives a V-0 rating at 1.6 mm. The special coating gives a better polymerfiller interaction and thus an improved performance. PA6 compounds, flame retarded with Magnifin, pass the glow wire test in accordance with IEC 695, part 2-1, at 960 °C. In another development, JM Huber Corp. has been granted a patent, US 5891090, for a flame retardant composition containing at least 25% magnesium hydroxide together with melamine and a trace of novolac. Compounders in the US, such as UVTEC Inc., have brought out metal hydrate concentrates under the name Safe FR. These concentrates are loaded with in excess of 70% magnesium hydroxide and find uses in polyolefin systems for wire and cable, building products market and in the E&E sector.

4.3.5 Other Inorganic Compounds 4.3.5.1 Iron Compounds Iron compounds have been tested as flame retardants. Commercial ABS polymers are very flammable, have a low limiting oxygen index (LOI) and produce large quantities of smoke. The addition of PVC (which is inherently flame retardant) to ABS has only a marginal effect on the low LOI and high smoke production of ABS. Work in this field has been carried out at Northumbria University in conjunction with Anzon. When iron peroxide was added to a range of ABS/PVC formulations, the LOI was increased, smoke reductions were significant and the amounts of char formed were increased dramatically. The possibility of producing flexible ABS/PVC blends, while still maintaining acceptable flame

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Flame Retardants for Plastics Market Report

retardant/smoke suppression characteristics was investigated. The addition of antimony oxide to phthalate plasticised blends gave the highest LOI values, while the iron compound generally gave the highest LOI values in phosphate plasticised blends. The iron-containing formulations also gave the best smoke suppression. A study of the relation between char formation and temperature in a number of ABS/chlorinated PVC blends showed that in the presence or absence of the smoke suppressor FeOOH there is a strong linear relation between char yield and the char formation temperature. The presence of the FeOOH had no effect on the linearity of the char/temperature relation and did not decrease the high values of the correlation coefficients. At all temperatures the char yield was increased when the amount of CPVC and FeOOH was increased, but the CPVC level in both the iron-free and ironcontaining blends was the most important factor controlling the char yield. The very significant smoke suppression effect of the FeOOH in the blends is explained in terms of iron/chlorine compounds formed in situ. The maximum smoke suppression effect was obtained at a blend chlorine content of about 20%. It was also shown that the char formation is directly related to smoke formation and suppression in these polymer blends.

4.3.5.2 Molybdenum Compounds Molybdenum and zinc containing compounds have been used as flame and smoke suppressants for a variety of polymers. These metal containing species normally act to assist the build-up of char on the polymer surface. This char is presumed to be the main method of flame retardancy. Halogenated systems form a large proportion of the market for molybdenum and zinc compounds. Although it is known that molybdenum can be vaporised by heating with HCl or HBr, most of the metal remains in the char of the burned polymers that contained the original fire retardant additive compounds. This is seen when char formation of PVC is increased when molybdenum is added at low levels. A char value of almost 10% with no additive becomes nearly 24% with 2 phr of MoO3. Over 90% of the molybdenum is found in the char. Likewise 63% of zinc from a zinc borate smoke suppressant remains in the char. This contrasts with just 5% of antimony found in char from a similar PVC compound containing antimony oxide. It would appear that the molybdenum acts as a kind of catalyst to convert PVC degradation species from becoming aromatic compounds (these burn to produce the familiar dense, dark smoke), into more linear aliphatic species or carbonaceous char. There can also be drawbacks with using some of the molybdenum and zinc-containing compounds just discussed. Molybdenum compounds can destabilise the colour of PVC sheet and flexible products and, under certain conditions, compromise dynamic heat stability. Zinc as borates, oxides or stannates can also reduce the thermal stability and thus restrict the loading levels that should be sensibly permitted. In demanding simultaneously low smoke applications with a high degree of flame retardancy, relatively high loadings of these additives are required and the compounder quickly comes across their stability limitations in halogenated polymers. Hydrated metal oxides reduce processibility and affect final physical properties at the levels required for flame and smoke suppression, an issue that is accentuated in non-halogenated FR polymers. Smoke suppression in rigid PVC can also be accomplished by the utilisation of a copper and molybdenum complex. A binary mixture of cuprous oxide and molybdenum trioxide reduces total smoke production, the average extinction area and smoke production rate. Increased char is formed and a reduced level of flammability in the PVC. CHARMAX LS and FR products from FVI Polymer Additives Group in the USA claim to have overcome some of these deficiencies. This has been achieved by the formation of stable complexes that have good dispersion characteristics in PVC and other polymers. The optimisation has been

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Flame Retardants for Plastics Market Report

accomplished via two routes. First, the flame retardant and smoke suppressant efficiency is increased by complexed elements being spread much more evenly through the polymer system in smaller amounts than the elements themselves could be if compounded into the polymer as standard products. These would be ammonium octamolybdate (AOM), zinc as zinc borate or oxide, etc. Second, the detrimental activity of individual elements is reduced by being tied up in the complex until thermal breakdown occurs at the elevated temperature of a real fire or fire test situation. CHARMAX LS are zinc-molybdenum complexes targeted as smoke suppressants in PVC wire and cable, PVC plastisols and rigid PVC products. LS Z4A is used in a simple PVC jacket formulation. Around 5% of such additives can replace up to 20% of AOM and reduce the afterglow sometimes seen with antimony oxide containing formulations. Also CHARMAX products are cheaper by weight than primary molybdenum and tin-based additives, AOM and zinc stannate, and lower loadings provide the required level of flame retardancy or smoke suppression that may be specified. The complexes may be used as partial of complete replacements for antimony oxides, whose price and supply has been unpredictable in recent times. Sherwin-Williams Chemical continues to develop molybdate-based smoke suppressants, used mainly in PVC compounds. In addition to its standard product, Kemgard 911C, a molybdenum/zinc complex, the company has introduced Kemgard PZC, which shows whiter colour and improved stability in plenum cable applications.

4.3.5.3 Tin Compounds Tin compounds, in particular (IV) tin oxide and zinc hydroxystannate have found applications as flame retardant and smoke repressant additives for halogen containing polymers. Like molybdenum, such tin compounds act predominantly in the condensed phase by a char-forming mechanism. However, at sufficiently high chlorine/tin ratios extensive vaporisation of tin may occur, so indicating a vapour-phase mechanism and allowing potential replacement of antimony trioxide in halogenated polymer compounds. Tin compounds such as zinc stannate are the alternative that most closely approaches a direct replacement for antimony oxide in halogen systems. They do come at a cost premium, however. Like molybdenum compounds, tin based ones have the key advantage of effective smoke suppressancy. Alcan Chemicals supply their Flamtard materials as alternatives to antimony trioxides for synergistic action in conjunction with various polymer systems. Flamtard H grades are used in halogenated polymer systems. They are thermally stable up to 200 °C and are particularly suitable for use with brominated polyesters, PVC and chlorinated PE. Flamtard S is thermally stable in all polymer systems. In the vapour phase, activity during combustion changes the flame chemistry to inhibit fire growth by removing chemical free radicals that support combustion. Additional effects in the condensed phase bring about changes not seen with traditional antimony trioxide systems. A hard carbonaceous char is formed that further retards the flame propagation and reduces the amount of smoke and carbon monoxide released during combustion. Surface effects on particulate matter can provide improved flame retardant properties. Alcan Chemicals has shown that surface chemistry can curtail some of the ever-increasing free radical reactions that occur prior to ignition. Alcan has found that by heating at lower temperatures for longer periods intermediate products are generated that exhibit significantly better flame retardant and smoke suppressant properties than either the stannate or hydroxystannate. This ‘slow roast’ provides a material with a bulk composition between that of the two. This intermediate outperforms either additive alone or any simple admixture. The following filled PVC compositions gave the test

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Flame Retardants for Plastics Market Report

results in Table 4.3 at an exposure level of 40 kW/m2: PVC DS7060 195 parts, dioctyl phthalate 81, epoxidised soyabean oil 10, ATH 75, Ultracarb 72, clay 75, stabiliser 10, tin additive 29. Table 4.3 Cone calorimeter results for filled PVC formulation Zinc Roasted ZHS hydroxystann ate (ZHS) Time to ignition (s) 84 86 Peak heat release rate (kW/m2) 87 78 Total smoke released 800 635 Average specific effective area (SEA) (m2/kg) 229 157 Source: Alcan Chemicals Limited, reproduced with permission.

Zinc stannate 75 122 1089 297

This suggests that the surface of flame retardants can be altered in ways that can improve their performance, particularly ignition performance. Other additive systems may benefit, such as crystalline ionic materials containing multiple cations such as calcium aluminate, zinc borate and calcium/magnesium carbonates. Further research is underway and this should yield useful information about the electron donor capabilities of certain materials and the role this plays in flame retardancy. Joseph Storey has introduced a zinc hydroxystannate flame retardant, which it found to be the closest non-toxic alternative to antimony trioxide in halogenated systems. The new material also has excellent smoke suppression properties. In halogen-free systems, tin char formation occurs, leading to reductions in filler loadings and improved physical properties.

4.3.5.4 Talc Work by the French company Talc de Luzenac, in conjunction with L’Ecole des Mines d’Als, has explored the area of industrial minerals as flame retardants. Emerging from the work in France is an awareness that in talc containing compounds characteristics of the interface between the talc and polymer influence the mechanical and ignition resistance of the material. Increasing the nucleating effect produced by the mineral gives better adhesion of the polymer to the filler and so a stronger reinforcing effect. This effect, which can be amplified by an increase of specific surface, leads also to improved fire properties as a result of the energy consumed to make the crystalline melt and the limitation of heat transfer produced by a layer of mineral particles of a strong specific surface ratio. The use of pure talcs of fine particle and high lamellarity index, in combination with a new generation bromohalogenated compound, makes it possible to obtain optimum mechanical properties and fire resistance as well as limitation of emissions of corrosive products, compared to traditional and more costly solutions. Specific talcs in the Luzenac range show high resistance to flame in polyolefins in synergy with bromine compounds, and are recommended for various applications, such as connectors in electrical installations and appliances. Talc has also been used in combination with magnesium hydroxide flame retardant. 4.4 Other Materials

4.4.1 Coatings Intumescent coatings, externally applied, have been available for many years, but originally only as somewhat rigid, thick layers that were unsatisfactory for flexible substrates in the paper and board industries.

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Flame Retardants for Plastics Market Report

Other sectors have initiated the search for products that are thinner, and plasticised enough to maintain their flexibility in use. These water-based products have been applied within the aerospace and shipbuilding sectors among others. Another technology is based on epoxy systems that are 100% solids. These are very water resistant in both fresh and salt water, and also resistant to most acids and alkalis. These coatings can be moulded, brushed, sprayed or applied as the user requires and are fire retardant and intumescent, producing low smoke in a fire. It has been shown that the resulting intumescent barrier is thick and spongy, and continues to grow even when knocked off the surface, and eventually will smother the fire. Such intumescence will exceed the original thickness of the coating by a thousand times. These two technologies have created a new opportunity for the effective treatment of aluminised polyester and other laminating materials, in addition to polyimide foam, materials that will shrink when subjected to heat. A very thin layer of the new coatings may be sprayed on, leaving a protected surface that is flexible, very light weight, and fire resistant. Typically, one litre of the epoxy-based coating at 40 µm thickness can cover nearly 40 square metres and still be effective. A fibreglass barrier cloth would burn through within one second, but by coating with an extremely thin coating of the intumescent formulation this burn-through may be delayed for more than seven minutes. A multi-layer system protected by the epoxy coating technique may survive for up to an hour or more, according to specialist company, Fire & Thermal Protection Engineers, Inc., of Petersburg, Indiana. Krona-FR is a fire retardant insulation material developed by Krona Industries and Fire & Thermal Protection Engineers. It combines portions of Krona insulation with material coated with an intumescent fire retardant. At 0.25" thick (~6 mm), Krona-FR is said to provide an R-15 rating of insulation. The coated material can be fibreglass, paper, basalt, cotton or synthetics. When the outer layer of Krona-FR is exposed to a flame, the intumescent coating activates immediately and protects the fibreglass that would normally disintegrate within two seconds. The intumescence combined with the melting fibreglass form a vitreous refractory silica that reportedly can withstand temperatures up to around 2200 °C. A new US company based in Hudson, Massachusetts has developed intumescent coatings and additives that enhance the fire properties of plastic and composite structures. Avtec Industries now offer Thermashield mastic coatings that can withstand temperatures in excess of 1200 °C for sustained periods. The coatings material is non-toxic and does not flake, peel or chip. It is resistant to water and chemical attack and is claimed to withstand multiple high-impact shocks.

4.4.2 Char Forming Polymers Generally, intumescent formulations contain three active ingredients: an acid source, such as ammonium polyphosphate; a carbonisation compound and a blowing agent. The first generation carbonisation agents used in intumescent systems for thermoplastics were polyols such as pentaerythritol, mannitol or sorbitol. Problems with this type of additive include migration/blooming of additives, water solubility of the additives and reaction with the acid source during processing of the formulations. There is little compatibility between the additives and the polymeric matrix and the mechanical properties of the polymer are then comparatively poor. Flame retardant intumescent formulations have been developed using charring polymers PA6, thermoplastic polyurethanes (TPUs), and hybrid clay-PA6 nanocomposites as carbonisation agents. The advantage of the concept is to obtain FR polymers with improved mechanical properties and to avoid the problem of migration and solubility of the additives. Polyvinyl alcohol (PVA) has been studied in a polyamide 66 based on the possibility of hightemperature acid-catalysed dehydration. The catalysis can be provided by the acid products of

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nylon hydrolysis, and the dehydration would promote the formation of intermolecular crosslinking and char. This has been called ‘synergistic carbonisation’, because the char yield and flame suppression parameters of the PVA/PA66 blend are significantly better than those of the pure polymers on their own. A pre-oxidised PVA via potassium permanganate achieved even better results. It was found that manganese chelate fragments act as catalysts for char formation. It is thought that polymeric char formers such as PVA, starch, glucose derivatives and polyfunctional alcohols may present a new trend in the global search for ecologically safe flame retardant systems.

4.4.3 Potassium Compounds Conventional organic systems are based on the acid catalysed dehydration of carbonifics such as dipentaerythritol. Metal oxides also have a use as catalytic flame retardants. For example, both antimony and tin have been used to impart flame retardancy to cellulosics without any assistance from halogen compounds. They appear to alter the condensed phase thermal degradation pathways in such a way that more non-volatile char and less flammable gases are generated. It has been found that low levels of potassium bicarbonate significantly modify the pyrolysis kinetics of a cellulose to yield more char. It has also been discovered that potassium carbonate enhances the charring of polymers containing pentaerythritol-silica combinations as flame retardants. This has led to the discovery of basecatalysed intumescence of potassium bitartrate. Combinations of potassium bitartrate and pentaerythritol show improved intumescence but carbon char oxidation by glowing combustion has remained a problem. Base catalysis is an attractive alternative to conventional acid-catalysed intumescent flame retardant systems as it could help to alleviate corrosion problems during polymer processing. Unfortunately, strongly basic residues also catalyse the oxidative destruction of the char-foam at high temperatures. The 3M Company has developed a flame retardant based on potassium perfluorobutane sulfonate (PSBK) for use in clear polycarbonate. PSBK is effective at 0.08 wt% compared to the 8-10 wt% levels typically used for brominated species.

4.4.4 Melamine Compounds Melamine-based flame retardants are a small but growing group of additives that are efficient and halogen-free. They are non-corrosive so reducing mechanical problems and with low toxicity, providing safe handling at all stages of production. They work through the heat-sink principle, the formation of non-combustible gases, specific chemical reactions and their contribution to the intumescent mechanism, forming a protective char. The heat-sink mechanism absorbs large quantities of energy through melting, sublimation and decomposition of the flame retarded formulation. This requires a fit between the polymer system and the flame retardant. Intumescence sees the flame retardant and the polymer form a stable char together, which protects the polymer from further flame propagation. The char builds up using significant amounts of the polymer and prevents further decomposition and the transformation of the polymer mass into gaseous products. Smoke reduction is a major advantage of intumescent flame retardant systems over standard halogenated systems. DSM (now Ciba) offers the Melapur range of melamine flame retardants.

4.4.4.1 Melamine Polyphosphate The main advantage of melamine phosphate (Melapur MP) is its low water solubility compared with ammonium-based phosphates. Applications range from thermoplastics to thermosetting resins.

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Melapur offers a melamine polyphosphate specifically for use in glass reinforced polyamide 66 compounds. Melapur 200 lowers the smoke emission compared to bromine based compositions. It gives a CTI of 350V and a corrosion behaviour much better than halogenated FRs, and there are improvements in gas emissions and smoke opacity. It is a char former with the polyamide. It is a white powder, providing new colour schemes for these materials. Formulations with 25-30 wt% of Melapur 200 in glass reinforced PA66 achieve a UL94 V-0 rating at a thickness of 1.6 mm. The balance between intumescence and thermal stability provides a processing window of up to 320 °C. It offers higher thermal stability than melamine cyanurate. Melapur 200 is expected to have a good share of the market for the protection of E&E goods. Melapur P46 is a synergistic formulation of nitrogen and phosphorus-containing compounds, developed for polyolefins, particularly polypropylene. An Italian company, Domus Industria Chimica SpA of Pedrengo, has developed a composition produced by reacting melamine with piperazine and phosphoric anhydride. It comprises piperazine diacid pyrophosphate, piperazine acid phosphate, melamine acid phosphate, melamine and possibly an alkaline phosphate. DuPont have patented a flame retardant composition based on melamine pyrophosphate, with or without zinc borate, for use in a number of thermoplastic resins (US Patent 5859099).

4.4.4.2 Melamine Cyanurate (MC) Good prospects seem likely to be fulfilled for melamine cyanurate (MC), which has appeared like a material-in-waiting, with a global consumption of around 15,000 tonnes. Development in Europe advanced quicker than elsewhere, mainly due to the presence of the raw materials in the region, with the major outlet being for polyurethane foam. The expiry of a Japanese patent for MC in polyamides should have an impact, but the most relevant development has been suitable compounding techniques. Whereas most FRs act by interfering with one of the three supports of combustion; heat, fuel and oxygen, MC acts on all three. In the initial stage it creates a heat sink by endothermic reactions and subsequent decomposition of melamine vapours. It provides only about 40% of the heat of combustion of hydrocarbons, and the combustion then generates nitrogen, which acts as an inert diluent. It can also retard the loss of other FR components, such as bromine and phosphorus, capturing these volatile components by the formation of salts while still showing FR activity at a later stage. Finally, it can also make a considerable contribution to the formation of char in the intumescent stage and a strong nitrogen/phosphorus synergistic effect is ascribed to the formation of N-P substances that remain in the char. These provide protection against further oxidation. It can also act as a blowing agent in the char, enhancing the barrier functionality of the char layer. Melamine cyanurate, Melapur MC, is less successful in glass filled polyamide compounds than Melapur 200, but works well in unreinforced PA66 or a mineral-filled formulation, achieving V-0 at 6-10% loading for the former, and at 13-15% in the latter. Melapur MC can be used also in epoxy and polyester resin mixes as well as in PET, styrenic compounds and polyolefins. Melapur MC can provide cost-effectiveness, good electrical and mechanical properties, as well as offering advantages in health and safety and colour performance.

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Melapur MC is regarded as a workhorse for standard polyamide compounds, since it cannot achieve V-0 due to lack of heat resistance in reinforced PA66 formulations. One of the other problems facing all users of MC is the intrinsically low bulk density that follows the requirement for a low particle size distribution. The solution is a free-flowing version designated as Melapur MC XL.

4.4.5 Silicon Compounds Work in Russia has shown that the use of elemental silicon plus tin chloride can enhance the flame retardancy of both polypropylene and polyamide 66 compounds. Silicon tetrahalides are formed in the gas phase of combustion and inhibit the chain reactions that develop in a fire. These silicon halides do not act like halogen hydrocarbons in the atmosphere so there is no likelihood of contributing to ozone depletion. At levels of 3% silicon and 2% SnCl2 very little hydrogen chloride gas is created and, in any case, it is consumed during the combustion that does take place. Work based in Hungary and France has been examining the claims for a siloxane compound to act as a synergist for the protection of polyolefins. Organoboroxo-siloxane (OBSi) is added with APP and pentaerythritol to polypropylene. The material appears to increase the viscosity of the polymer composition and provide some plasticity to the resultant intumescent char. The plasticity allows for better prevention of char cracking and so provides improved flame retardancy. The increased melt viscosity is created by the product of BSi-pentaerythritol, formed during the compound preparation, and the improved char plasticity is the result of products formed at high temperatures from BSi and APP.

4.4.6 Graphite A new type of intumescent additive is expandable graphite. This material has already found uses as a special effect pigment due to its metallic sheen and grey-black colour. Nord-Min has been developed by suppliers Nordmann Rassmann with flame retarding of plastics in mind. It is a halogen-free fire barrier additive from Chinese sources, based on natural graphite flakes with intercalated acids. Depending on the raw material and the acid treatment, the expansion rate is up to 250 times the original volume. Grades treated with sulfuric acid begin to expand at around 200 °C; with nitric or acetic acids, expansion starts at about 150 °C. This is too low for many technical thermoplastics and a key development is to raise the expansion point to the 300 °C mark. Nord-Min is regarded as a ‘fire barrier additive’, not a flame retardant, in that it only functions once a fire has commenced. It is often, therefore, used in synergy with other, conventional flame retardants. The intercalation process, having utilised acids, is followed by neutralisation with either ammonia or caustic soda. Final washing to remove all traces of these various water-soluble reagents is necessary to avoid any interactions during processing in, for example, PU foams. Graphite is a very soft material and has to be handled carefully. To avoid undue shear on the material it should be added last during any mixing process. Expandable graphite has been used in flexible PU foams for public transport seating, in trains, buses and aircraft. Applications in the automotive sector are being examined, as are its uses in rigid PU foam for insulating materials. Expandable graphite acts mainly in the condensed phase as a smoke suppressant and an insulator. Where the expanded carbon layers are too unstable, it is possible to combine the graphite product with other FRs, such as those mentioned above, to form intumescent layers to stabilise the foam.

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Expandable graphite can also work in the gas phase by releasing volatile matter and has a synergistic effect with other types of FRs that work by thermal decomposition. Normally Nord-Min is combined with halogen-free products, but it is possible to combine with halogen-containing ones as well. Graphites can be used alone as smoke suppressants giving a heat insulation effect but, for some applications, the expanded carbon layers are too unstable and other FRs, such as zinc borate, APP or ethylene diamine phosphate, can be used as stabilisers, to give a good span of properties and applications. Ucar Carbon Co of Cleveland, OH sells GRAFGuard expandable graphite flakes. Flame retardancy is promoted by inserting an expansion agent between the carbon layer planes, to form an insulating char layer when heated. The char layer provides a heat barrier, cuts off air and reduces the migration of decomposition products. A Swedish company has developed a wide-ranging product programme based on expandable graphite (EG). International Carbide Technology, or INCA AB, based in Bromma, Stockholm has been collaborating with Chin-Dow Ltd., and the Centre for Aviation and Space Technology, both in Taiwan. EG is very stable in normal conditions. However, when the temperature exceeds 200 °C the EG will expand rapidly up to several hundred times in volume. Owing to the fact that the vaporisation point of graphite is above 3000 °C, EG can sustain its integrity in the flame zone and provide better fire protection than many other substances. The expansion process of EG is a ‘mechanical’ rather than a ‘chemical’ process. When exposed to fire it creates a crosslinked carbon char and small porous holes on the surface of the char contribute to a better smoke suppressing performance. It is regarded as comparable to a carbon filter. At high temperatures, the EG only emits water vapour. The pH is neutral and stable. When used in a flexible PU foam, smoke and toxic fume emissions are greatly educed compared with untreated foam or ones with halogenated FRs present. When utilised in a polypropylene composition, the heat release rate is much lower than for a halogen- or a phosphate-based FR, with a much-reduced peak. In addition, EG prevents dripping of molten polymer, is environmentally friendly and does not migrate. The INCA programme includes fire retardants for rubbers, plastics and foams, covering polyolefins, polyurethanes and other types; plus expandable smoke seals, fire stop putties and sealants and intumescent coatings for metal, wood and GRP. Computer simulations on the use of EG in various plastics components for automotives have shown that for a fire started by a burning cigarette and the resultant spread there is, on average, a 20-30% increase in the time before the fire ignites surrounding materials and so generating a serious situation. Another test scenario shows an increase in ‘escape time’ from the cabin area, i.e., before flashover to a conflagration occurs, of 50%, from 30 seconds up to 45 seconds. The reduction of heat release rate and the prevention of dripping are the major properties offered by these EG products for the improvement of fire safety. Expandable graphite has potential as the flame retardant in polypropylene-flax composites under consideration for vehicle trim, along with other natural fibres, and also in building applications.

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4.4.7 Glass Flake A new glass flake manufactured in the UK is substantially thinner and more consistent than previously produced flake. A range of properties and performance benefits include an improvement in fire retardancy. Research and testing by Glassflake Limited and various customers in different industrial sectors has shown that the product, as used in rubbers, thermoplastics and thermosets, acts as an intumescent, that provides improved flame and fire retardancy properties and reduces drip and sag. Incorporation of the flake can reduce smoke density, add to melt strength and give rise to an intumescent charring effect. Glass flake materials performed excellently in smoke chamber testing. The materials have been successfully incorporated into PTFE blocks as a replacement for the more usual glass fibre used to produce a range of gaskets and bearings. Similarly, the glass flake has been formulated into coatings for rubber sheeting as used for packing applications, where the product adds to fire retardant characteristics, and in particular improves ‘hold up’ when exposed to a vertical spread of flame.

4.4.8 Low Melting Glasses Another type of additive has been developed from the concept of low-melting phases as polymer additives. In principle, low-melting glasses can improve the thermal stability and flammability characteristics of polymers by: •

Providing a thermal barrier for both undecomposed polymer and the char, if any, which forms as a combustion product.

•

Providing an oxidation barrier to retard oxidation of the thermally degrading polymer and its combustion char residue.

•

Providing a ‘glue’ to hold the combustion char together and give it structural integrity.

•

Providing a coating to cover over or fill-in voids in the char, thus providing a more nearly continuous external surface with a lower surface area.

In the 1980s a system for PVC was developed based on zinc, potassium and sodium sulfates. Lowmelting glassy systems containing other metals, such as calcium, caesium, nickel and cobalt were also tested. More recently silica gel combined with potassium carbonate has been found effective for a range of common polymers at only 10% loading. Polypropylene, polyamide, PMMA, and cellulose were found to be retarded and, to a lesser extent styrenic polymers. The efficacy of the additives in these inherently non-char-forming thermoplastics depends on the polymer, PP > PA66 > PMMA > PS. The proposed mechanism was the formation of a potassium silicate glass, but such a material should not form until the temperature reaches 725 °C; however, if sodium salts are present, this temperature drops to 400-500 °C.

4.4.9 Polymer Blends Another trend is the modification of the physical structure of a polymer system by employing blends of polymers. Some work on blends of polypropylene and ethylene-propylene copolymers has been shown to generate char, whereas PP alone does not. Oxidative degradation and a change in the kinetics of oxygen consumption by the blend have been found to provide a correlation between char yield and limiting oxygen index. A 2:1 ratio of PP to the copolymer generates 3.4% of char and increases LOI from 17 to 21. Such data indicate the solid-phase nature of the flame retardancy in these blends. A modification of the polymer morphology is believed to lead to a decrease in combustibility. Another common example is the use of PVC as a fire retardant in ABS.

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4.4.10 PTFE Small amounts of PTFE, added to several polymers that are flame retarded with antimony-bromine systems, can significantly improve their flame retardancy. The chemical reaction between PTFE and Sb2O3 leads to the evolution of volatile Sb-containing species which, however, are not responsible for the whole mechanism of flame retardancy as the improvement requires all components to be involved; the polymer, the bromine system and, of course, the PTFE. It has been found that SbF3 is the species of greatest interest since it is likely to be formed in high temperature reaction between PTFE and antimony trioxide. The combustion behaviour of ABS FR formulations containing SbF3 and PTFE separately has confirmed that the SbF3 may well be an active flame retardant agent in the systems. In its presence combustion is slowed down, yet a delay occurs before the flame is extinguished. As soon as combustion develops, the additional effect of the fluorine-containing compound is no longer significant and flame retardancy is due only to the bromine/antimony reactions. It is believed that SbF3 plays a role in increasing the molecular weight of the ABS chains, for example, catalysing the polymerisation of polybutadiene double bonds with an increase in thermal resistance of the material and so a reduced rate of fuel being fed to the flame front.

4.4.11 Aluminium Flake Silberline Limited a UK compounder that specialises in pigments has found a range of applications for aluminium flakes beyond pigmentation. One of them is that such flakes, perhaps surprisingly, cause ‘fire retardancy’ in polyethylene, polypropylene and polystyrene, have no effect in polycarbonates but accelerate combustion in polyamides.

4.4.12 Hindered Amine Light Stabilisers Ciba Specialty Chemicals has been adapting an existing light stabiliser technology to offer a flame retardant functionality. One of the company’s types of hindered amine light stabilisers shows some capability as a non-halogenated flame retardant, one example is Flamestab NOR 116. A UV stable N-alkoxy hindered amine additive containing no halogen offers flame retardancy at surprisingly low concentrations. It synergises with conventional bromine- and phosphoruscontaining FRs to provide improved performance in polyolefin fibre and moulding applications. N-Alkoxy hindered amines (NOR) were first introduced as non-interacting light stabilisers for flame retarded fibre and agricultural film applications. NOR hindered amines have low basicity and are in a more active oxidation state than conventional hindered amines. In the film applications, pesticides generate acidic species and deactivate conventional hindered amines. Similarly, hindered amines are deactivated by the thermal or photo generation of HBr from flame retardants resulting in inferior light stability. Studies encompassing brominated flame retardants, conventional HALS, and NOR HALS confirm that NORs perform significantly better than conventional light stabilisers in the presence of brominated FRs. It was thought earlier that the non-interactive nature of NOR HALS with the halogens present in FR additives positively influenced the performance. It was found that NORs alone provide flame retardancy in their own right. NOR-1, the first material tried by Ciba for this new role, did not always provide sufficient FR properties to pass appropriate fire tests. The NOR stabilisers appear to work alone in high surface area situations such as PP fibres, but not in mouldings without the presence of a conventional FR.

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NOR-1 as a synergist with brominated or phosphorus FRs can provide flame retardancy in moulded articles without antimony trioxide. V-2 formulations can be designed with lower levels of conventional flame retardants. It is easily melt processible and does not weaken the mechanical or physical properties of polyolefins, and also allows for safer use and recycling. Further work by Ciba has shown that a UL94 V-0 rating can be achieved with NOR-1 and a halogenated FR system. This rating was achieved with a three-component FR blend. The total loading of the FR additives was 14.5 wt%. The V-0 rating is achieved with significantly lower concentrations of the halogenated component and in the absence of antimony trioxide. V-2 is achieved with only around 4-6% total loading for halogenated additives and with 17% for a halogen free (phosphorus-based) system. There are expected to be V-0 non-halogenated systems containing NOR-1 for polypropylene mouldings in the future as the chemistries are explored and refined further. The lower levels of the additives and the absence of antimony trioxide provide better processibility, lower density, lower smoke emission and improved physical and mechanical properties. In addition, the new systems meet environmental goals and provide even safer use and recycling. Gabriel-Chemie, the Austrian masterbatch supplier, has reported on its ongoing developments, which have led to combination packages of additives for polypropylene formulations destined for outdoor applications such as stadium seating. Here attractive colour must be protected for UV stability and, as a public place, for fire hazard as well. Aromatic BFRs have great thermal stability, but high loadings may be necessary and they reduce the UV stability of PP. It is thought that bromine radicals are released by photo-activation. These radicals then can react directly with the UV stabiliser present and so deactivate the stabiliser. Aliphatic BFRs are advantageous in this regard; yet lack much thermal stability, so a careful choice must be made to match the converter’s chosen processing technique for the final product. Only HALS stabilisers for UV have long-term efficacy in polypropylene and so the company, in collaboration with Ciba Specialty Chemicals, has finally evolved a package. A multi-component system has been commercialised that contains a halogenated FR, light stabilisers and correct pigment regime for applications such as stadium seats. The system has been designated as the ‘PPSYS UVFR’ system of which no further details have been released to date.

4.4.13 Nanocomposites The increasing usage of nanocomposites, based on layered silicate, or clay, mineral fillers has led to examination of their effects on the flame retardancy of the resin systems that they reinforce. Work led by the National Institute of Standards & Technology in the US would suggest that the nanocomposites structures retain a reinforcing role during and after combustion by enhancing the performance of the carbonaceous char that forms during the process. The multi-layered carbonaceous-silicate structure may act as an excellent insulator and also a mass transport barrier, slowing the escape of the volatile products generated during decomposition. A similar structure has been found in the combustion residues of polyamide-6 and epoxy nanocomposites and also polypropylene modified with maleic anhydride. These all used less than 5% of montmorillonite clay (MMT). The delaminated versions of MMT-based nanocomposites also offer definite improvements in a variety of physical properties. The intercalated versions also offer reduced flammability, but with less improvement in the physical properties of the resultant composites. In some types of nanocomposites the nature and aspect ratios of the assembled silicate structures may affect their ability to resume a reasonably coherent structure during char formation. Such structures would be less effective in reducing movement of volatiles and ‘new’ fuel and so have a reduced flame retardancy capability. This latter phenomenon was found in some polystyrene nanocomposites that utilised fluorohectorite. PS composites using MMT did show a decrease in flammability.

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Early studies on silicate-polymer nanocomposites show that they have distinct advantages over traditional flame retardants in problem areas such as production of soot and carbon monoxide during combustion and the hampering of mechanical properties, as found with high loadings of other FR fillers. Relatively low concentrations, 2 to 5% of silicate, are necessary in nanocomposites, compared to the amount of additive used in traditional filler systems. This allows silicate-polymer nanocomposites to be processed by extrusion, injection moulding and casting in the same manner as unfilled polymers. Commercial advantages resulting from the low loading of added silicate are lower cost and ease of manufacturing a component. Nanocomposites are an environmentally friendly alternative to some types of flame retardants, as they contain no additional halogens, phosphates or aromatics above those contained in the chosen polymer resin. The silicate remains intact at very high temperatures. In addition, whereas many flame retardant compounds, particularly filler types, increase the carbon monoxide and soot levels produced during combustion, no similar increases have been observed with nanocomposites flame retardants. Polymer colours are not affected by the presence of these silicates and physical properties are, in many cases, improved as well. Highly interesting properties exhibited by polymer-layered silicate nanocomposites include their increased thermal stability and also their ability to promote flame retardancy at very low loadings. The formation of a thermally insulating and low permeability char to volatile combustion products caused by a fire is responsible for these improved properties. The low filler contents in nanocomposites that account for the dramatic improvement in thermal stability are highly attractive, since FR end-products can be made cheaper and be easier to process. Depending on the nature of the filler distribution within the matrix, the morphology of the nanocomposites can evolve from the so-called intercalated structure where a regular alternation of the layered silicates and polymer monolayers is observed, to the exfoliated (delaminated) structure where the layered silicates are randomly and homogeneously distributed within the polymer matrix. The easiest and technically most attractive way to produce these types of materials is to knead the polymer in the molten state with a modified layered silicate, such as montmorillonite. Compounding on different machines, such as a Buss ko-kneader or mills, still produces essentially the same morphology in the resulting nanocomposites. It has been shown that composites of clay and polyamide 6 can be prepared easily by melt blending. These nanocomposites have been shown to have an increase in mechanical properties by over 40% along with a significant reduction in flammability. Layered silicate clays like montmorillonite are being actively studied for their synergistic activity with well-known flame retardant materials. A number of patents have emerged in this area. It is known that standard FR materials often, in one way or another, degrade polymer properties while clays improve them. Taken together, a synergy is expected that may generate novel products in the years ahead. Optimisation of the polymer interaction with the surface of the clay plates would appear to be the key to obtaining the necessary dispersion of the nanoparticles in the polymer. The technology employs cationic compatibilisers such as alkyl ammonium surfactants. These surfactants penetrate between the clay platelets and are attracted to the excess negative charge embedded in the clay lattice. The negative charge results from an isomorphic substitution of a lower-charge metal cation for aluminium. Once separated, the platelets are ripe for penetration by molten polymer molecules, thereby producing homogeneous nanocomposites. The NIST in the US has recently developed the

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use of imidazolium cationics, which have better thermal stability than the alkyl ammonium surfactant treatments. One exciting aspect of these emerging nanocomposites systems is that about half of the commercial flame retardant can be removed and replaced with only 3-4% of nanoclay. This allows the use of about 10% more polymer. Not only does the undesirable reduction of physical properties sometimes produced by the flame retardant decrease, but the clay enhances stiffness and heat distortion properties as well. A commercially available layered silicate, Nanofil, is based on montmorillonite modified by dimethyl distearylammonium cations and offered by Süd-Chemie in Germany. An idea of the promise for these nanocomposite systems may be seen in the EUPEN work for cable jacketing and the announcement by General Motors and Montell (part of Basell) regarding their use in automotive door panels. The use of graphite in nanocomposites has been reported for polypropylene and polystyrene formulations. These are prepared by bulk polymerisation using potassium graphite. Although an increase in thermal stability is observed, there is no increase in mechanical properties. Polyamide/graphite nanocomposites can also be prepared by melt processing. If there is no acid present, a slight increase in thermal and mechanical properties is observed, while those containing acid show no change in thermal stability but a decrease in mechanical properties. A greater understanding of graphite/polymer nanocomposites is required before they can take a possible place alongside the better-understood clay-containing nanocomposites. Süd-Chemie has developed a new series of flame retardants in collaboration with Alcan Chemicals. These are a combination of Alcan's inorganic Flamtard AN and Süd-Chemie's nanoclays that offer advantages for the cable sector such as a lower dosage and higher extrusion output compared to existing products.

4.4.14 TSWB TSWB, a flame retardant additive from Avtec, see Section 4.4.1, is a sandy-coloured particulate material that may be mixed into various resins and applied to cured parts or incorporated directly into resin systems. About 20-35 wt% loading is suggested and the additive has been assessed in epoxy, vinyl ester, polyester and phenolic resin compositions. The key material cited is a glass- and ceramic-based system including other ingredients to tailor it for adhesion, flame retardance, flexibility and general compatibility. Avtec advise that it is important to work with their formulation engineers to tailor a system to the customer’s requirements, especially the chosen catalyst used to avoid any unwanted and unforeseen chemical reactions. The effect on viscosity is minimal until a 30% loading is reached. A bonus appears to be the enhancement of the appearance and overall aesthetics of moulded parts.

4.4.15 Noflan A new arrival is a spin-off from space technology in Russia. Noflan is being distributed by CFB, an Isle-of-Man company. Details available were very sparse, but the material is a white crystalline powder, soluble in water but microencapsulated and water repellent for normal use. It acts by forming a carbonised top layer on the polymer, reducing heat build-up and retaining decomposition products. It can be used with polyolefins, polyamides, acrylics plus thermoset polyesters and epoxies. Loadings are in the range of 14-20%, with 30% recommended for polyamides. LOI is 26 to 30%, rising to 35% for epoxies.

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The carbonised layer becomes quite ‘gas-tight’ and so Noflan does not release toxic substances when exposed to fire and can even reduce smoke and fumes. It has a melting temperature of 200 °C and is thermally stable up to 250 °C.

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5 Polymer Families and Their Flame Retardancy This chapter covers most of the main plastics families and some of the methods to make them flame retardant. Some producer-specific information is provided as well as more generic comments on the various plastics types in commercial use. 5.1 Polyolefins

5.1.1 Polyethylene Polyethylene ignites readily and melts and drips as it burns, leaving little or no residual char. The incorporation of flame retardants into polyethylene is made difficult by the crystallinity of the polymer, which impedes homogeneous distribution of the flame retardant and reduces its effectiveness. In the past, polyethylenes were generally flame-retarded with chloroparaffins and antimony trioxide. Frequently PVC or chlorinated polyethylene was also added. Nowadays cycloaliphatic (hexabromocyclododecane) and aromatic bromine compounds such as polybromodiphenyl ethers, and in particular decabromodiphenyl ether are used. Antimony trioxide is also used here as a synergist. Further possible additives include aluminium hydroxide, magnesium hydroxide and magnesium carbonate. Intumescent systems are increasingly promoted when a halogen free system is requested. The Chisso Corporation of Osaka, Japan has patented a flame-retardant resin laminate that includes a layer of polyolefin containing ammonium pyrophosphate and a nitrogen-containing organic compound. The laminate generates hardly any black smoke or toxic gas and has excellent appearance, printability, weathering and scratch resistance (US 583052). The Aicello Chemical Co. of Aichi, Japan has disclosed a flame retardant for polyolefins (US 5852082) consisting of melamine cyanurate, fine silica and a phosphoric acid ester. The material emits no hazardous gases on combustion or incineration, needs no extra costs for treating ash, and exhibits excellent flame resistance and strength. ICC Industries has examined the difficulty of maintaining a UL94 V-0 rating while optimising the impact strength of LLDPE. The research looked at the effect of the rotational moulding cycle on the properties. The composition included a small quantity of functionalised silicone additive along with antimony trioxide, PTFE and another flame retardant. Zotefoams has added new F grades to its LD-15 polyethylene foam range to meet the needs of the automotive and aerospace markets. The range of foams is the lightest available for crosslinked foam with a density of 15 kg/m3, some 30% lighter than any other polyolefin foam, and is made in LDPE and metallocene catalysed polyolefins. Grade MP15FR Grey has been developed to meet the specifications of the major aircraft manufacturers for smoke and toxic gas emission, as well as spread of flame. The specifications met by the grade include ABD0031 for Airbus Industrie, CAA8 for the Civil Aviation Authority and FAR for the Federal Aviation Authority. The material is specially formulated to impart improved tear strength, tensile strength and elongation properties. This results in a grade with enhanced toughness and abrasion resistance. The main applications are for insulation and seating areas. Grade LD15FM meets the car industry’s requirement for spread of flame in the FMVSS test at 3 mm thickness and above. Weight saving and cost benefits are also attractive to motor manufacturers.

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5.1.2 EVA Ethylene-vinyl acetate copolymers, usually known as EVA, are used in many applications, but especially for low voltage cables. These polymers are easily flammable and flame retardants are added to reduce their flammability. The classic solution is to incorporate aluminium hydroxide or magnesium hydroxide that develop endothermic reactions when heated. Nevertheless, large amounts have to be incorporated, often around 60% and this can lead to a loss of mechanical properties in the compound. Intumescent technology that works well with polypropylene has also been tried for EVA polymer systems. EVA and Exolit AP 750 at 30% addition levels develops an intumescent coating between 200 and 460 °C to give better thermal stability and good fire retardancy. Above 460 °C, however, the protection decreases. The presence of polyethylenic chains is observed in the intumescent coating up to 460 °C. Others who have investigated other phosphorus-retarded polymers have found the trapping of such chains in the ‘shield’. It was thought that these chains were responsible for the interesting properties of the char. In contrast, the formation of aromatic and/or polyaromatic structures in the intumescent shield is shown to occur from 300 °C upwards. The latter structures condense when the temperature increases (300 °C < T < 460 °C). A phosphocarbonaceous structure is formed in the shield; in particular the presence of P—O—C bonds with aromatic carbons that can yield good adhesion and resistance to the coating. Also, the formation of polyphosphoric acid-like species and H3PO4 can act as an additional protective glassy barrier at the surface of the coating, which reinforces the intumescent protection. Zinc borates are used as synergistic agents with ATH and magnesium hydroxide flame retardant formulations of EVA. Botax has carried out studies in France. It has been found that while the hydrated oxide flame retardants are decomposing to release their water molecules, ignition is thereby delayed. Once combustion occurs, the polymer forms a crosslinked network and a subsequent carbonaceous char. There is a reduction in the rate of heat release, when zinc borate additives are also present. It is believed that decomposition of the zinc borate molecules in the presence of the polymer leads to a vitreous phase, which renders the char more effective in suppressing combustion rate and also smoke particle generation. Further work by this French team has shown that the zinc borate slows the degradation of the polymer, allowing the creation of the observed vitreous protective layer which can act both as a physical barrier and a glassy cage for polyethylene chains. A group in Italy has been exploring strategies for the EVA compositions that are used as cable insulation. These have focussed on non-halogen systems. Attempts to increase char yield by promoting the amount of crosslinking of double bonds have utilised either deacetylation of vinyl acetate units or the dehydrogenation of ethylene sequences in the EVA. Palladium catalysed dehydrogenation has proved unsuccessful, but the oxidative route of thermally decomposing potassium permanganate appears promising. Organic peroxides fail to increase the rate of crosslinking of deacetylated units. Better results are obtained with the addition of an intumescent system. This is a combination of melamine phosphate and phosphate-phosphonate substituted trimethylamine. The EVA is shown to play a substantial role in the intumescence phenomenon, thus complementing the zinc borate work in France. Work by the cable company BICC General Cables and a local university in England have also been examining EVA compositions that include various fire retardant additives. A 26 wt% vinyl acetate content resin was the focus of the investigation. ATH is a popular additive in EVA compounds since they can take large quantities of fillers; however, the physical properties are modified by the 60% levels required to achieve worthwhile flame retardancy and when ignited such materials burn

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with strong incandescence. Such an exothermic phenomenon represents a potential risk because it may reignite the polymer some time after the extinction of the flame. Nitrogen- and phosphoruscontaining compounds are commonly utilised to provide suitable flame retardancy without the drawbacks of ATH. These are often melamine and derivatives or polyphosphate compounds such as APP. The mode of action of melamine appears to involve endothermic sublimation, acting as a heat sink, vapourphase dissociation and also self-condensation under suitable conditions. APP achieves its flame retardant effect by intumescence and char formation acting as a barrier to combustion reactions. Since ATH, melamine and APP have different modes of action in a fire situation, the BICC General programme has examined various combinations of these flame retardant additives in EVA. Formulations containing APP burned with the formation of intumescent carbonaceous chars, with EVA acting as a carbonisation agent. EVA materials containing 20% APP, plus a sufficient amount of ATH or melamine, were superior to the non-intumescent ATH and melamine containing formulations with regard to heat release rate, mass loss rate and smoke production. Melamine showed some smoke suppressant effect and significant CO reducing properties. However, melamine-EVA and melamine-ATH-EVA showed a very high heat release rate. It was found that oxygen played a favourable role in enhancing the char formation by encouraging active participation of the polymer matrix in the interaction with polyphosphoric acid. The materials based on the combinations of APP with a sufficient amount of ATH or melamine may be considered of interest for cable insulation based on EVA. These formulations burn with the formation of a protective intumescent char and were superior to non-intumescent ATH-EVA ones. The CO production for the APP-melamine containing EVA was also reduced to a marked degree by comparison with the ATH-EVA system. However, in the case of the APP-ATH-EVA formulation, the total CO yield increased to some extent by comparison with the ATH-EVA mixture. An acrylamide graft technique induced by plasma, developed in China, has been shown to increase the flame retardant and smoke suppressant properties of an EVA compound. Time to ignition was extended and char residue increased. This indicated that the –CONH2 side group in the grafted layer could not only be charred in the thermal degradation, but could also promote charring of the substrate polymer. The smoke density observed was lowered in the acrylamide-grafted EVA. Other amide containing formulations can provide useful improvements to the mechanical as well as fire properties of EVA compounds. These new intumescent formulations use PA6 and a PA6 clay nanocomposite hybrid as carbonisation agents. Work in both France and the US has shown that the clay allows the thermal stabilisation of a phosphoro-carbonaceous structure in the intumescent char which increase the efficiency of the shield and, in addition, the formation of a ‘ceramic’ that can act as a protective layer. Studies on various fillers in EVA compounds for comparison with ATH and magnesium hydroxide have found that hydrotalcite has promising FR effects. 50 wt% of hydrotalcite in EVA has a very low heat release rate and a low evolved gas temperature. The layered structure of hydrotalcite may provide an explanation. The formation of a char layer was observed, which retains an intumescent, fairly compact, surface during combustion conditions. The major approach now for EVA compounds, especially those designed for cable jackets, is the introduction of nano-clays to the mix. As little as a 3% loading of a nanofiller produces a marked effect on heat release. 5% of nanofiller reduces the peak heat release rate by almost 50% as well as shifting that peak towards longer time-lapse. The flame retardant properties are due to the formation of a char layer that acts as a firm insulating layer and dramatically reduces the emission of volatiles towards the flame front. The silicate layers not only play the active role in char

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formation, their presence also strengthens it and makes it more resistant to cracking. It was found that ATH could be reduced to only 45% of the composition. The reduction in the total amount of the fillers results in improved mechanical and rheological properties of typical EVA-based cable compounds.

5.1.3 Polypropylene Only about 1% of PP volume consumed employs any flame retardancy additives. Flame retardant applications for PP are proportionately much less important than for other resins such as styrenics and engineering thermoplastics; less than 5% of the total FRs consumption is used in PP. This is mainly due to the difficulty and cost in reaching the high standards of flame retardancy required in electronics and building industries with PP compounds. The cause of this difficulty is the high crystallinity and flammability of PP. FR PP applications are found in various fields such as electrical, covering lamp sockets, coil bobbins, connectors, TV yokes and, to a lesser extent wire and cable; pipes for water discharge; fibres in textile products; film and sheets for roofing. The addition of decabromophenyl ether plus antimony oxide is the current ‘standard’ method of adding some flame retardancy to polypropylene, but during burning there is a large increase in smoke density. It has been found that the addition of hydrated magnesium calcium carbonate dramatically reduces the smoke density and also improves the LOI slightly. So, combining these two flame retarding systems can make for a strongly flame retardant polypropylene compound without a serious increase in smoke density. Work in Italy by Montell (now part of Basell) and Turin University examined the optimum mix of melamine with other mineral fillers to obtain the best balance of properties. The addition of melamine to mineral FRs for polypropylene improves flammability behaviour as measured by UL94 and eliminates the afterglow phenomenon. However the melamine is not sufficiently thermally stable and requires special precautions in processing. It does, though, lower the compound density, which is an economic advantage and allows use of cheap inert fillers such as clay or talc. The LOI decreases with increasing amounts of melamine, and it was found that for all fillers tested 40% melamine to 25% mineral mixtures, totalling 60 phr by weight, showed the best compromise between LOI and UL94. Great Lakes have found that tetrabromobisphenol A bis (2,3-dibromopropyl ether) is an effective flame retardant for PP homo- and copolymers plus talc filled systems. It provides for UL94 V-2 rating and Glow Wire 850-960 °C requirements with additions of antimony trioxide in the compounded systems. Varying degrees of fire retardancy have been noted for PP formulations that contain APP as a char former, plus the presence of thermoplastic polyurethanes of different chemical compositions. The nature of the polyol employed to make the TPUs would appear to have a significant influence. The morphology of the intumescent material, its growth and eventual degradation can be well evaluated from the measurement of viscosity. The loss of the protective character, i.e., reduction of heat and mass transfers related to the superficial foam morphology, may be explained by change of the viscosity of the charred material under stress. Work in China has shown the synergistic effect of silicotungistic acid (SiW 12) on polypropylene flame retarded by an intumescent FR (NP28 phosphorus-nitrogen compound). The tungsten compound increased the thermal stability of the PP formulation at temperatures above 500 °C. The SiW12 could efficiently promote the formation of compact intumescent charred layers with phosphocarbonaceous structures.

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5.2 PVC Until very recently, almost all PVC cables were stabilised with lead salts. These gave good thermal stability and electrical resistance, with low water absorption. When the cable was required to have better flame resistance than inherent in PVC, a small part of the calcium carbonate filler was replaced by antimony trioxide. All such cables perform well and have done for many years. Now, however, the need to focus on ecotoxicity has caused the lead salts to be replaced by a non-heavy metal system, usually a calcium-zinc complex. Likewise, the role of antimony is being questioned and formulators have come up with other solutions. The traditional filler used in cables is calcium carbonate. Replacement of this by ATH, Mg(OH)2, magnesium carbonate or minerals in which these occur gives flame retardancy without increased hazard. Zinc borate provides a capability of smoke suppression. Where better fire resistance is required, part of the plasticiser may be replaced by a suitable grade of triaryl phosphate, with a very low toxicity. A study on a range of commercially available flame retardants and fillers in rigid PVC formulations was carried out by European Vinyls Corporation (EVC). Rigid PVC has a high inherent flame retardancy, but additional additives are needed to pass very severe fire regulations. The M1 classification of the French Building standard using the Epiradiateur Radiation Test is one such; and the forthcoming SBI test to be introduced under the EU Building Products Directive is believed likely to be another. The key requirement for PVC when it is eventually made to burn is the minimisation of the dark smoke levels emitted. Antimony, zinc and molybdenum compounds were incorporated as well as hydrated aluminium and magnesium fillers. The fire testing covered Limiting Oxygen Index, heat release parameters and smoke emission. General heat stability (integrity) and mechanical impact tests were also performed. It was found that zinc hydroxystannate (ZHS) gave the best overall fire performance. In the oxygen index test, formulations containing ZHS gave an average improvement in LOI of 18 units, which was the highest increase observed. In the cone calorimeter, ZHS gave the highest increase in time to ignition (6 min) and the greatest reduction in peak rate of heat release (80 kW/m2). The average reduction in smoke parameter was 79 MW/kg. There were no synergistic effects between ZHS and either of the fillers, ATH or magnesium hydroxycarbonate (MHC). However, there was found to be an interaction between ZHS and ATH that resulted in a significant increase in smoke emission. Also the formulation containing a combination of ZHS and ATH showed a significant reduction in time to decomposition in the thermal stability test, although ZHS had no effect on the heat stability of rigid PVC in combination with either of the other fillers. In terms of its effect on mechanical properties, ZHS gave an average improvement of 2.5 kJ/m2. Formulations containing ammonium octamolybdate (AOM) also showed good fire performance, particularly with respect to reductions in heat release rates and smoke emissions, although the increase in time to ignition was significantly lower than that for ZHS. However, AOM caused a reduction in the time to decomposition in the thermal stability test of 9 minutes, and a decrease in Charpy impact of 4 kJ/m2. It is also more expensive than ZHS. Zinc borate gave good performance as a smoke suppressant in the cone calorimeter, but was not as effective as either ZHS or AOM in reducing rates of heat release. Also it had no effect on time to ignition. It was not found to affect the heat stability of rigid PVC, unless used in combination with ATH. The grade of zinc borate used gave a reduction in whiteness of the test pieces and a reduction in impact of 7 kJ/m2.

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Antimony trioxide, widely used in PVC formulations, gave a reasonably good fire performance but, as expected, increased the smoke emissions detected. It was not found to affect the thermal stability of the rigid PVC, and had no effect on either the colour or impact properties of the extruded PVC. The flame retardant fillers, ATH and MHC, gave disappointing results in all the fire tests. It was concluded that at levels of 10 phr there were no benefits in replacing calcium carbonate with FR fillers. Neither were there any consistent synergistic effects between ATH or MHC and any of the flame retardants. Furthermore, ATH was found to depress the heat stability of the rigid PVC when used in combination with the FR additives, and MHC reduced impact strength by around 3 kJ/m2. The conclusion of the EVC work was that ZHS had excellent fire retardant and smoke suppressant properties in a rigid PVC compound, with no detrimental effects on key physical or mechanical properties; and so merited further detailed study for rigid PVC formulations. Further work on ZHS was carried out to determine the optimum level required. There was found to be a threshold loading of 3 phr of ZHS, which gave a dramatic increase in the time to ignition. It was concluded that it is essential to add a minimum level of 3 phr to realise the material’s ignition prevention capabilities. Increasing the addition level from 3 to 4 phr does provide some extra benefits in terms of reduced rate of heat release and reduced smoke generation, but, for these rigid PVC formulations, there is no advantage in adding more than 4 phr of ZHS. Ning and Guo of Sichuan University found that incorporating small quantities of zinc borate or ATH or both greatly increases the limiting oxygen index of rigid PVC and reduces the smoke density emitted from the PVC during combustion. Such additions also increase the char formation. The quantity of aromatic species released during combustion decreases whereas that of aliphatic by-products is seen to increase as a result of a series of crosslinking reactions during the combustion process. Another Chinese study found that copper and molybdenum oxides were influential in the smoke behaviour of burning PVC. Cu2O and MoO3 have different effects, with the molybdenum oxide increasing smoke generation, yet the combined oxides reduced smoke emission. In combination or individually, they effectively reduced smoke emission during hydrogen chloride elimination. It was proposed that the metal oxides promote crosslinking of PVC and stabilise the backbone. Synergism was observed that resulted in an increased char residue. The German Federal Institute for Materials Research & Testing has concluded that antimony oxide in plasticised PVC may be replaced to a certain degree by zinc sulfide. They studied 5% total loadings of the additives either alone or in mixtures. Synergism was observed for the mixtures. ZnS alone appeared to have no effect, yet a 50/50 mixture gave an equivalent flame retardancy as antimony oxide alone. Formulating lead-free flexible PVC containing Firebrake ZB (from Borax) with excellent heat stability is possible with Ca/Zn based stabilisers. An LOI of about 30 can be obtained with 30 phr of ATH and 6 phr of Firebrake ZB. These can be improved when part of the diisodecyl phthalate plasticiser is replaced by a phosphate plasticiser and calcium carbonate is present as an additional functional filler. Similar formulations, with magnesium hydroxide in place of ATH were compared. Results showed that the ATH/ZB combination provides an increased LOI over that containing Mg(OH)2 as well as increased time to ignition, a reduced rate of heat release and reduced smoke. The use of Rheofos 90, a phosphate ester plasticiser, as part of the formulation improves the flame retardancy even more. Firebrake ZB can replace antimony trioxide in flexible PVC formulations to improve smoke performance while maintaining good fire performance and good heat stability characteristics.

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Unplasticised PVC products such as pipes, windows and cladding do not contribute to fire propagation and most rigid formulations will pass most flame tests without the need for FR additives. However, the higher the level of organic additives such as impact modifiers and processing aids in a rigid PVC compound the less flame resistant it becomes. The EVC study used a lead-stabilised window profile formulation containing 7 phr of acrylic impact modifier. There may be cases where FR additives will be required in order to pass severe fire specifications, like the M1 classification of the French Building Standard using the Epiradiateur Radiation Test. Also, under the EU Building Products Directive there is now a move to harmonise national fire legislation and testing. The new ‘spread of flame’ test or SBI test may require some increase in the fire retardancy of current rigid PVC formulations. 5.3 Styrenics Styrenic copolymers such as HIPS and ABS are used widely for the production of TV housings, computers and office equipment. These polymers burn easily and so flame retardant systems have been evolved over the years that provide much improved performance under fire conditions. This has been achieved mainly by the use of brominated flame retardants with antimony trioxide as a synergist. At one time the main standard applied for flame retardancy in electrical goods was UL94 V-0 from the US. This standard requires that the plastic does not burn or drip under vertical exposure to the flame. In the early 1990s, under political pressure from Green parties and other environmental groups, some European producers started a ‘downgrading’ and are using the less severe standard IEC 65 that permits a slow horizontal burning of the plastics. European experts in flame retardancy and fire hazard chemistry consider this new tendency dangerous. TV sets can cause severe fire quite easily when made under these less stringent materials requirements. A massive TV recall by one manufacturer came after a series of fires in private dwellings; it appears that no flame retardant was utilised in many of the sets they sold into the European market. This trend in the European market is particularly unacceptable since several brominated FR systems are tailor-made for styrenic copolymers. Suppliers such as Dead Sea Bromine have introduced newer brominated systems that do not contain any of the brominated diphenyl ether types targeted for their potential toxic attributes when used as FRs in polymers. FR-1808 is a brominated indane containing 73% bromine and is suitable for application where good flow and good impact properties are needed. This combination of properties makes possible the use of short cycle times and enables production of large parts with thin sections. Other products of interest from the same company are the F-2000 and F-3000 series based on brominated epoxy oligomers. They are offered for applications requiring good UV and light stability. Their polymeric nature is the root of better efficiency as flame retardants. Their bromine content is between 50% and 55% and since they are melt processible, they do aid the injection moulding of compounds in which they are incorporated. These flame retardants have good thermal stability allowing processing temperatures above 260 °C. The producers of computers, printers, monitors, copiers and keyboards would all like to utilise environmental labels like the Blauer Angel (Blue Angel) or the ‘TCO99’ to their equipment. A feature common to all the award guidelines is that they largely exclude the use of plastics incorporating flame retardants that contain halogen. Apart from dispensing completely with flame-retardant materials, which will generally require at least design modifications to the products containing them, the growing importance of environmental labels has led to an increase in demand for polystyrenes with halogen-free FRs. Two

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products from Atofina provide suitable properties. Lacqrene 851 attains UL94 V-0 and a 5VA rating; and Lacqrene 852 gives a UL94 V-2 rating. Fine grades of antimony trioxide are utilised with brominated FRs to protect ABS formulations. A sub-micron particle size product is effective with TBBA or with bis (tribromophenoxy)ethane. The ATO product has little effect on impact properties and only a slight detrimental effect on flexural properties. A range of ABS blends with PVC was developed in the late 1980s for use in the business machine and consumer electronics sectors. The PVC brings UV stability and inherent flame retardancy to the blend, while ABS offers heat resistance, good impact strength and flow properties. The blending of a cheap, easily processible polymer, which is flame retardant, into a useful engineering material was regarded as a more efficient method of achieving appropriate levels of retardancy than the use of large quantities of expensive additives. 5.4 Polyamides Polyamides (nylons) melt and drip on ignition so that when held horizontally they tend to be selfextinguishing. However, the molten drips can continue to burn. Grades reinforced with glass or minerals tend to have increased burning rates. The first methods of providing flame retardancy consisted of bromine-based retardants plus an antimony synergist that continue to be utilised. However in recent decades nitrogen or phosphoruscontaining additives have been used, which promote char formation and so delay the combustion process. These range from elemental red phosphorus to various phosphate and phosphonate species of additive. Melamine compounds and most recently magnesium hydroxide are also increasingly used, especially when neither halogens or phosphorus-containing formulations are regarded as desirable. The use of injection moulded polyamides in many industries has increased over the years, and the need for flame retardancy has grown with this market. In the automotive industry reinforced polyamides have replaced metal components and another important sector is electrical connectors where a high tracking index (CTI) can be achieved. Several FR systems have come to the market from various sources. 58% are halogenated products preferred for their better thermal stability. 42% are non-halogenated types used when a high CTI is specified; these can be broken down into 22% red phosphorus products, 16% melamine cyanurate and the remaining 4% of magnesium hydroxide. As seen from the market share, red phosphorous is widely used and is cost efficient. A loading of around 7% gives classV-0 in glass-reinforced polyamide but processing conditions are critical to avoid auto-ignition with the subsequent production of highly toxic phosphine. Another major limiting factor of red phosphorus is that it is not possible to achieve light-coloured materials. The mechanism of flame retardant action of phosphorus-containing additives in aliphatic nylons is similar to their mode of action in other polymers. The phosphorus-containing additives seem to affect the processes occurring in the condensed phase. Phosphoric and related acids formed during combustion may catalyse dehydration or deamination of the nylons and promote char formation. These acids may form a thin glassy layer on the surface of the burning polymer, thus lowering oxygen diffusion and heat and mass transfer between the flame and the condensed phase. It has been shown that phosphoric acids react with nylons upon heating to give phosphoric esters, which are char precursors. Although phosphine oxides or esters or salts of phosphonic or phosphoric acids have been discussed as potential candidates for flame retardant nylons, it seems that only red phosphorus and melamine pyrophosphate are really used on an industrial scale.

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Polyamide compounds with reduced flammability may be produced by the introduction of melamine. 15-20% parts of melamine in PA6 gives suitable properties. These compounds have good mechanical and flammability characteristics, and have potential in many applications within electronic and automotive fields. Melamine cyanurate is another candidate for utilisation in polyamide compounds but it is restricted to unreinforced polyamides due to its limited thermal stability. A loading of 12% can give V-0 rating for UL94. There is also the possibility of some plate-out or blooming with MC. Melamine cyanurate powder, containing nearly 50% of nitrogen can be used as an additive to polyamide 6 at the melt stage before fibre spinning or plastics production. The addition of MC lowers the specific tenacity of the fibres but decreases the flammability. This latter effect is stronger in solid plastics than for fibres. A new polyamide material has been developed by the University of Massachusetts in Boston that has strong implications for the safety of aircraft. The polymer is called polyhydroxyamide (PHA), which decomposes into a rigid flame-resistant substance, polybenzoazole (PBO) when it is heated to around 200 °C. As it does so, it releases water vapour that helps to suppress a fire. Once PHA has decomposed into PBO, it remains strong enough to maintain its integrity and remain stable in temperatures of up to 900 °C. This should vastly improve the time period in which a structure such as an aircraft interior can retain its shape and allow evacuation before its eventual collapse. Bergmann Kunststoffwerk of Gaggenau, Germany, part of the PolyOne and designated Engineered Materials Europe within the group, has introduced a range of polyamide compounds that do not rely on halogens or phosphorus for flame retardancy, aimed at the electrical industry. Although non-halogen compounds have been around for some time, polyamide compounds for the electrical sector have often contained red phosphorus, particularly in reinforced grades. However, although this gives good flame retardant characteristics with good electrical properties, degradation in processing and environmental concerns have led to pressure from users to move away from these grades. They are still recommended where it is essential to maintain mechanical and electrical efficacy, especially Comparative Tracking Index. The new compounds are based on Bergamid PA 6, 66 and 66.6 copolymer. Examples are given in Table 5.1. Table 5.1 Flame retardant polyamide compounds from PolyOne UL94/ Comparative Base polymer Filler Example Glow Wire Tracking Index Test B700 600 V2/960C Bergamid PA6 — B700UF 600 V0/960C — B70G/Mi20UF 500 Glass/mineral V2/960C B70G15UF 600 V0/960C Glass Mu133 Bergamid — V2/960C 600 AB700UF PA66.6 Bergamid — V2/960C* 600 A700 PA66 Glass V0/960C 425 A700G30U SO ABO Tio-35 * no FR additive needed to achieve UL94 V2 Source: PolyOne Th. Bergmann GmbH

Notes UL Listed UL Listed

UL Listed UL Listed UL Listed

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Dechlorane Plus, with 65% chlorine content, has been used in polyamide applications for many years but has become superseded by newer FRs. It is very good for UV stable applications but is somewhat costly and has limitations with regard to its thermal stability. Brominated trimethylphenyl indane, seen as FR-1808 from the Dead Sea Bromine Group, is now finding increasing application as an alternative in polyamides. It has several inherent advantages as a result of its high bromine content, suitable thermal stability and melting range. It can be processed up to 300 °C and decomposes around 150 °C below the self-ignition temperature of PA66. When processed above its melting range, FR-1808 behaves as a melt blendable FR and has important beneficial effects on properties such as impact strength and flow. Enhanced flow is particularly crucial for electronic devices made of glass-reinforced polyamide, which are often designed with thin-wall dimensions. There are also cost advantages for moulders of polyamide parts, which come from the high bromine content and FR efficiency of FR-1808, and the processing aid effect during moulding that reduces cycle times and lowers power consumption. Production of thin-walled parts results in a reduction of weight and light coloured materials can be achieved if desired. Surface treated magnesium hydroxide is now offered as an alternative flame retardant for polyamides. Synthetic grades do not affect the colour of the product and are non-blooming fillers. Depending on the PA grade a loading of around 55 wt% gives a V-0 rating at 1.6 mm. The additive itself contains from 30 to 55 wt% of magnesium hydroxide. The special coating gives a better polymer-filler interaction and thus an improved performance. PA6 compounds, flame retarded with a product such as those from Magnifin, pass the glow wire test in accordance with IEC 695, part 21, at 960 °C. In today’s PA applications, miniaturisation of E&E components imposes higher thermal stress on the melts during injection moulding. In addition, the densification of conductive paths on electronic components due to miniaturisation demands increasing resistance against material degradation caused by electrical stresses. Resistance against degradation caused by electrical stresses is commonly classified by testing for Comparative Tracking Index (CTI). Historically, there appears to be a perception in the market that the benefits of zinc borates are mostly linked to CTI improvement of PA compounds containing a cyclo-aliphatic chlorinated FR such as Dechlorane. In glass-fibre reinforced PA66 compounds a brominated FR present with a zinc borate and no antimony trioxide can produce a high FR performance and also an improved CTI. So, PA compositions with a CTI >400 volts and a UL94 V-0 classification at 0.8 mm can be developed using Firebrake ZB as a single active FR synergist with a brominated polystyrene. These materials show improved thermal melt stability. Pyrochek 68 is a brominated polystyrene with 68% Br content with a high thermal stability but a high loading is needed because of its lower FR efficiency. Owing to its high softening range, PA compounds containing it have limited melt flow properties. It does however allow for a high CTI. 5.5 Modified PPO (m-PPO) Flame retardancy of m-PPO is improved by incorporating thermally stable phosphorus based additives, such as red phosphorus and organic phosphorus compounds like triphenyl phosphate, triphenyl phosphine and triphenyl phosphine oxide. The mechanism would appear to be gas phase activity rather than reactions in the condensed phase for all except red phosphorus where both are seen. Both triaryl phosphate and zinc borate are effective flame retardants in m-PPO, but not in HIPS. The m-PPO is a higher heat polymer than HIPS, with m-PPO processed at temperatures where

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HIPS undergoes degradation, despite the presence of HIPS in the PPO–HIPS blend alloy. Higher decomposition temperatures lead to different flame retardant chemistries. Zinc enhances the flame retardancy of triaryl phosphate in m-PPO, leading to the highest LOI values. Zinc powder, however, is coated with zinc oxide. Work has shown that zinc oxide enhances the decomposition of m-PPO. Thus a zinc coating (zinc arc spray) is perhaps more representative of the effect of zinc with triaryl phosphate than zinc powder, with the latter having a greater zinc oxide surface. In m-PPO the FR triaryl phosphate has a particular role in smoke formation. Zinc borate is an effective smoke and flame retardant with or without the presence of triaryl phosphate. With zinc borate, low heat release and smoke release m-PPO materials are possible. It is interesting that in the latter case, LOI values are low and the zinc borate deactivates triaryl phosphate in those materials that contain it. Since LOI only measures ease of extinction, it will not necessarily correlate with other flammability properties. In more recent times GE Plastics has upgraded their Noryl range of PS-modified polyphenylene oxide materials without recourse to halogens. Improved flame retardant properties are found in the new Noryl GTX 4110 series, which uses a proprietary flame retardancy system free from halogens and red phosphorus. The compound has high heat and chemical resistance. 5.6 Polyurethanes Rigid PU based foam insulation materials received a boost when a programme of work by IVPU, the German association for rigid PU foam makers, showed that compared to competing materials, the risk of smouldering and glowing with PU is very low. A study in 1998 examining ‘Fire risks of smouldering and glowing in thermal insulation materials in flat roofing’ involved mineral wool, rigid PU foam, wood fibre, and expanded perlite. Testing was carried out to DIN 4102 part 7A. UP rigid foam board – in building materials class DIN-4102-B – and with a thin mineral fleece facing on both sides, showed no evidence of risk as a result of mouldering or glowing. The risk with noncombustible rock wool insulation boards was found to be ‘immensely greater’ than the risk for moderately flammable PUR rigid foam insulation boards. Haloalkyl phosphate esters are well-established effective flame retardants for flexible polyether based PU foam. It is believed that the phosphate materials interact with the PU material to generate a phosphate related species that is the direct retarding agent. It was once thought that the ester decomposed under heat to phosphoric or polyphosphoric acids, but specific testing has not found the presence of any of these acids during careful pyrolysis of foams. Polyether foam carefully treated with a coating of free phosphoric acid was confirmed as receiving retardant properties, so it is surmised that with both commercial esters and the experimental acid each reacts with the foam to create the direct retarding species. Mica and ATH have shown good properties when incorporated into TPU compositions. Results indicate that 70-80 phr of ATH presents good flame retardancy. The use of mica does not impede the fire resistance behaviour of the composites where the ATH has had a surface treatment. The ‘traditional’ additive flame retardant added to PU rigid foam formulations is tris-(chloropropyl) phosphate. Now, however, customers, especially in Germany and Scandinavia are demanding FRs that are halogen-free and do not migrate. Ammonium polyphosphate, which is successful in flexible foams, has now been introduced for rigid PU foams to meet these requirements. Although ammonium polyphosphate is a solid, it can be easily dispersed in the polyol and is less abrasive than melamine and calcium carbonate. This makes it easy to use in the foaming process and meets the requirements of insulation materials within the building industry.

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Flexible moulded polyether foam is widely used in the transport, furniture and packaging sectors. In many cases flammability is of great importance and so the effects of suitable flame-retardant agents on such foams has been widely studied. One piece of work by Chestnut Ridge Foam in Pennsylvania, using Cone Calorimetry, studied the heat release characteristics of various combinations of commercially available additives, plus the CO emission and time to ignition. Unfortunately nearly all FR formulations generated more CO and smoke during the test programme compared with the basic foam. Halogenated phosphate ester compounds appeared to extend time to ignition by the greatest factor and also reduce the peak heat release rate by a substantial margin of 33%. The reduction rises to 43% with the addition of antimony oxide, but at the sacrifice of shorter ignition time and more CO. Silicone powder, in the form of an amine functionalised siloxane, also provides for a 40% reduction in peak HRR, with very low CO emission, but sacrificing time to ignition. The same company has developed a new generation of highly flame resistant open cell flexible PU/CR hybrid foam materials. The polyurethane and chloroprene are prepared using a ‘brand-new’ technology called Foam-One. This is a batch process for making flexible slabstock under variable pressure that may range from 1 psi to 25 psi. PU base foams are post-treated with a polychloroprene compound to obtain the hybrid grades. The technology enables the making of low-density foams without using auxiliary blowing agents such as methylene chloride. The process is utilised to incorporate a specifically designed fireretardant package into the base PU foams so that the post-treated foams easily meet all US federal requirements for aircraft seat cushion, contract furniture and mattresses for hostels, prisons, and other multi-occupancy public institutions, etc. They also satisfy naval and military standards as well. At Salford University in England a team has developed a powerful tool for examining behaviour in the so-called ‘dark flame’ region behind the flame front in polymer fires. Laser Pyrolysis generates combustion in polymer materials that it is now believed better represents real fire scenarios than previous, slower, techniques. Time-of-flight mass spectrometry then analyses the chemical species present over time both qualitatively and quantitatively. Interesting observations have emerged from the work on PU foam systems. Rigid foam formulations can vary in isocyanate index (amount and distribution of NCO groups) and the molecular weight of the polyols utilised. The flame retardancy of these materials has been shown to increase with increasing isocyanate index and weight fraction of isocyanate. Laser pyrolysis experiments show that the major volatiles evolved are dominated by monomer and oligomers of the polypropylene glycol used to form the foam, plus lower molecular weight species of which carbon dioxide appears to be a significant part. An increase in isocyanate index results in a reduction in the extent of monomer/oligomer evolution and an increase in the low molecular weight species. In phosphorus retarded rigid foam, the mechanism for the activity of the dimethyl methylphosphonate, added at a low percentage, is believed to be a reduction in the evolution of fuel from the foam material. Some workers in Taiwan have reported making flame retarding polyalkyl phosphate type polyols from ethylene glycol or 1,4-butanediol, and then reacting them with isocyanate to form polyurethanes. Solutia has patented cyclic phosphorus (1,3,2-dioxaphosphorinanemethan) amine compounds as flame retardants in polyurethanes (US 5844028). Changing methods to produce flexible foam, by the replacement of fluorocarbon blowing agents in many cases with carbon dioxide, have brought consequences for the choice of flame retardant

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additives for these newer formulations. In addition, the need to reduce automotive fogging has also brought a new perspective to these choices. With regard to fogging, relevant tests are conducted at increasingly high temperatures, which means manufacturers have to stop using volatile additives that condense on cool glass surfaces. When carbon dioxide is utilised, it is very difficult to use solid additives with CO 2 processing equipment. Although small quantities of extremely fine pigments may be used, solid flame retardants such as melamine and ammonium polyphosphate do not process satisfactorily. Automotive foams account for the largest flame retardant usage in flexible polyurethane foams in Europe. Halogenated FRs continue to be the choice for their best cost/performance ratio. The ‘standard’ FR for automotive foams is regarded as tris dichloropropyl phosphate (TDCP). Unfortunately, this additive doubles the fogging factor compared to no additive. A recent product from Great Lakes is an improvement, in that it only increases the fogging factor by one third. Firemaster BZ-54 is a liquid brominated benzoate ester, introduced as an alternative to pentabrominated diphenyl ether, which is to be phased out of use in Europe through legislation. BZ-54 has a significantly higher molecular weight than TDCP. The relative contribution of a FR additive to fogging will increase with the introduction of lowervolatility catalysts and polyols. As volatile FRs are found to be major contributors to fogging, they will in future be replaced in flexible foams by either higher molecular weight or reactive FRs. Halogenated FRs tend to be more effective than halogen-free types, since either a higher loading is needed or more expensive phosphorus-containing ones are needed. Different FR additives are used for furniture foam, where the only flammability requirements in Europe remain those in the UK and Ireland, to pass BS5852 source 5. The traditional approach to meet this standard has been tris monochloropropyl phosphate (TMCPP) and melamine combined. Efforts to remove solid melamine from these foams to improved physical properties continue; however, the relatively low cost of the combination has made melamine all but indispensable. This has to change with the introduction of the carbon dioxide blowing agent. Solids are particularly difficult to process on the appropriate machinery and melamine is especially difficult since large qualities are utilised and a coarse particle size is required for optimum FR performance. Melamine-free or ‘all liquid’ formulations are increasingly preferred, but halogen-free FRs will have limited use in furniture foams since higher addition levels are required to counter their lower efficiency. These levels, in turn, adversely effect foam physical properties and finally costs. The efficiency of APP in polyurethane coatings is well known as a fire retardant treatment. The addition of APP to PU accelerates the decomposition of the matrix but leads to an increase in the amount of high-temperature residue, whether under an inert or oxidative state. This stabilised residue acts as a protective thermal barrier during the intumescent fire retardancy process. Examination and analysis of the charring materials help to understand the carbonisation and intumescence process. It has been shown that the char resulting from PU consists of an aromatic carbonaceous structure that condenses and oxidises at high temperature. In the presence of APP, a reaction between the additive and the polymer occurs, which leads to the formation of a phosphocarbonaceous polyaromatic structure. Moreover, this char is strongly paramagnetic. Large radical species present, such as polyaromatic macromolecules, can trap free radicals, and so enhance the fire retardant performance of the PU/APP formulations. Polyurethane-modified polyisocyanurate (PIR) foams have a reputation for being the most flame resistant of the PU related foams used for insulation. They are increasingly being made from an aromatic polyester polyol (APP) and the isocyanate is most often MDI. Unlike polyurethanes, however, the amount of MDI is comparatively high. Isocyanate indices of 250 or higher are used

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with an excess of MDI, as much as 50% is typical. This excess can be made to react with itself to yield trimeric isocyanurate. It is this trimer that imparts the excellent FR properties to the rigid foam. The combustibility of PIRs is related to the release of volatile flammable products during the early stages of decomposition. Because PIR foams have outstanding thermal resistance, they are less apt to decompose and burn. Typical PU linkages decompose at ~200 °C, with char yields less than 20%. In contrast, the isocyanurate ring structures in PIR systems decompose at ~325 °C, with typical char levels of 50%. This char has low thermal conductivity and high resistance to oxidation. This means that that it not only protects the underlying material but, because the surface can withstand higher temperatures, it can re-radiate a large fraction of the incident heat load. While the trimeric isocyanurate structure gives PIR foams their thermal stability, char formation is also influenced by the polyol type. Consequently, the ideal polyol is one that promotes char formation through the urethane linkage. In addition, it has been found that char yields are directly related to the number of aromatic ring structures bonded into the polymer backbone. Accordingly, the choice of polyol in PIR and modified PIR systems is extremely important. This is the major reason for the rapid growth in the use of aromatic polyester polyols, or APPs. A further way of improving fire performance and also the dimensional stability of PIR foams is by incorporating glass fibres into the foam laminates. This technique was developed and patented in the US over 20 years ago, but the costs are higher than for PIR foams made with APPs. 5.7 Thermosets As a result of their three-dimensional crosslinked structures, thermosets do not soften or flow when burning. The tendency to form gaseous decomposition products is also less than with thermoplastics. Heat may cause surface charring that can prevent ignition. Unsaturated polyester resins and epoxy resin systems require flame retardants to meet the fire protection standards in the construction, transport and electrical industries where such resins are mainly used. The flammability of epoxy resins is greater than comparable thermosets since they have a reduced tendency to carbonise. After removal of an ignition source, once alight they continue to burn on their own. Phenolic resins have a great tendency to char thus reducing the formation of volatiles and so they extinguish if the ignition source is removed. The high nitrogen content of urea and melamine resins acts as an inherent flame retardant. Phosphorus-containing FRs influence the reaction that occurs in the condensed phase and so their effectiveness depends on the polymer structure. They are particularly effective in materials with a high oxygen content, like polyesters, polyurethanes, epoxies or cellulose. Ammonium polyphosphate and red phosphorus are excellent flame retardants for all types of thermoset resins. In most cases the combination of a phosphorus-based FR with ATH passes high levels of flame retardancy at relatively low filler loadings: ~50-70 phr compared to 150-250 phr using ATH alone. The low filler levels reduce the viscosity of the formulations and also the laminate density. Pultruded components for buildings and transportation systems are made by Exel (formerly Menzolit-Fibron) in Vörde, Germany. These are made flame retardant by a combination of APP with specially treated ATH that enables appropriate processing to occur, without the need for halogenated species being present.

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A new approach to render fibre-reinforced rigid composite materials flame retardant is undertaken by the utilisation of complex fibrous-intumescent chars. The use of flame retarded cellulosics fabric, surface coated with an interactive intumescent as an additional reinforcement in an otherwise conventional structure has been studied. Thermal analysis has shown that when heated, all components decompose by chemically interactive mechanisms leading to a char-bonded structure and the residual mass of char formed is higher than expected above 450 °C, even in the case where polyester resins are present. Not only are greater fractions of char formed above 450 °C but the chars formed are more resistant to oxidation than the respective components (resin, traditional fabric and coated cellulose). Thus composites comprising these various components will have significantly improved fire performance.

5.7.1 Unsaturated Polyesters The flammability of unsaturated polyester resins can be reduced by incorporating halogencontaining species. Reactive FRs of this type are hexachloroendomethylenetetrahydrophthalic (HET) acid or its anhydride, tetrabromophthalic anhydride or dibromoneopentyl glycol. Ethoxylated TBBA is also used as an additive with antimony oxide as a synergist. When halogenated resins do burn, they generate smoke and toxic fumes, which are unacceptable for some applications, especially in mass transit systems. ATH may be used in halogen-free formulations, yet to raise the fire properties of polyester compounds to match or better those of phenolics, high loadings of ATH are required. Disadvantages are the increase in resin viscosity for processing and an increase in density. However, suppliers have been introducing coated and other improved grades to address these concerns. The use of ATH is also limited when high glass contents, over 30%, are required. The levels of ATH necessary to pass some stringent specifications are so high that the component suffers a serious loss of mechanical properties. Polyester resin in which dicyclopentadienol (DCPD) is present as grafts on chain ends is more stable than those without. In a fire scenario, ignition takes place more or less at the same time in both cases. Material degradation, at first, takes place faster in the DCPD tipped resins. This lasts a brief period, as the consumed material becomes a char that keeps the subsequent rate of heat release at a lower level than pertains in the non-tipped versions for the remaining duration of a fire. No char is seen in the non-tipped resins. No other flame retardants were present in these formulations. The German company, Lurgi Zimmer, has patented a process for producing flame resistant polyesters that involves using carboxyphosphinic acid as a co-monomer (US Patent 5859173). Phosphorus compounds are often combined with silicon rather than nitrogen, as in European Patent 899301 from General Electric, in which a polyester moulding compound is flame retarded with an organoclay, a polymeric siloxane composition and a boron and phosphorus containing material. Phosphorus containing compounds offer another route to provide halogen-free flame retardancy in thermoset composites. Ammonium polyphosphate materials promote carbonaceous chars that are bound into a vitreous coating formed by the polyphosphate decomposition products. The smoke density emitted from such systems in a fire easily satisfies the requirements of the German Bundesbahn, the French Epiradiateur test for irradiated surfaces, and Airbus requirements for smoke and toxicity. Clariant has found that use of APP, such as Exolit AP422, and red phosphorus, Exolit RP65x family, in combination with ATH allows useful formulations to be prepared that meet these standards with relatively low loadings of fillers. These can be around 50-70 phr in place of the 150250 phr for ATH alone. The low viscosity of the resin mixes allows processing by all the conventional methods, such as RTM, hand lay-up, pultrusion etc.

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Exolit AP740 from Clariant is a recent ammonium polyphosphate blend that can be incorporated into gelcoats as well as the main polyester resin. For hand lay-up, spray techniques and RTM it is recommended to add AP 740 to the gelcoat, but is not necessary for SMC or pultrusion applications. By varying the polyphosphate content of a 30% glass fibre polyester composite, usually in a range from 30 up to more than 70 phr, fire tests of differing stringency, including those for German transportation requirements, may be passed. The Exolit grades of polyphosphate can also serve to provide UP-resin and epoxy-resin gelcoats with flame resistance and intumescent characteristics. The use of an intumescent gelcoat can very often enhance markedly the fire-safety of the component as a whole. The gelcoat, when thus flameretarded, can take on the major role of protection against fire. The layer of foam generated is not only a fire barrier, but prevents the heat from gaining access to the underlying layers. This makes it an interesting proposition for sandwich structures consisting of laminates and foam cores, which are often more difficult to flame-retard than the individual constituents. For components made by the RTM method, the use of intumescent gelcoats offers the possibility of adding less-effective liquid flame retardants to the laminating resin and adding solid additives to the gelcoat only. The composite consisting of laminate and intumescent gelcoat can comply with fire and smoke requirements, whereas the laminate with standard gelcoat would not. Such considerations lead to the possibilities of concentrating the flame retardant protection at critical locations of a design and so also allow glass fibres for strength and other additives for processing and fire protection to be married together for the overall improvement of the final products. It would also allow design applications for which GRP composites have not hitherto been possible or appropriate. The range of Exolit phosphate additives are becoming widely used in reinforced plastics designed for European railways. They allow the materials to pass various DIN German standards for flame and smoke retardancy such as DIN 4102: B1 and DIN 5510: S4 SR2 ST2, that previous halogenbased systems could not meet. Work in Poland has shown that zinc stannate and zinc hydroxystannate are the most efficient ignition and smoke retardants for GRP laminates, with antimony trioxide also being a good smoke suppressant. This appeared to be irrespective of the presence of other flame retardant additives. The resin systems also contained halogen additive or retardant components on the polyester backbone. The most well-known fire performance standard for composite and other materials in the UK building industry is BS 476, Parts 6 & 7. There are a number of ways in which resins can be modified to meet the ignition and flame propagation requirements of these standards, each with their benefits and limitations. Retardant fillers limit the processibility of resins and so limit the fibre content and structural performance. Also, some fillers may produce toxic fumes during a fire. Unfilled flame retardant resins rely on technology to incorporate chlorinated and brominated species on the unsaturated polyester resin chain. As a result many composites based on resins of these types can achieve Class 1 surface spread of flame ratings when tested to BS476 Part 7 and ignitibility resistance when tested to Part 6, which enables them to meet UK Building Regulations for use in the construction of non-combustible buildings. Requirements in other European countries can vary, although there is a general correlation between the various surface spread of flame tests. The French NFF-16-101 test requires an assessment of smoke and toxic fumes with the F (smoke) rating made up from three components: • • •

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Smoke density measurement; Opacity (light obscurity) measurement; Toxic fume measurement.

Flame Retardants for Plastics Market Report

Few unsaturated polyester resin-based laminates can achieve better than the F2 level with most only able to reach F3. However, in recent years, developments in resin technology have resulted in M1 (the best surface spread of flame requirement in the French test, which is equivalent to BS476 Part7 Class1), and F0 classifications with some filled resins (Scott Bader Crystic 343A). The major limitation is a maximum fibre content, by weight, of just 20%, which limits applications to semi- or non-structural components only. Hence, such materials can be used for many decorative internal components and cladding panels supporting their own weight. The introduction of the new common European legislation to reclassify all building materials should change nothing in terms of practical usage and specification for polyester composites, but just place all construction materials onto a common ‘register’. Mass transit systems now often employ polyester composites made with low smoke, low toxicity resins now on the market. One such is a Synolite resin system from DSM Composite Resins. It can be formulated with ATH as the sole flame retardant, from Martinswerk. The pultrusion process only allows for limited filler loads due to the large quantities of glass fibres that are incorporated. New formulations have been developed that use ATH and/or polyphosphates to achieve a high degree of flame retardancy with acceptable glass loadings. These have been successful in fulfilling standards required for building and construction as well as public transport applications.

5.7.2 Epoxy Resins Epoxy resins are usually flame retarded with bromine, either in the chain or as additives. Some novel ways of increasing the flame retardancy of epoxy resins have been explored in recent times. The major brominated flame retardant used with epoxy resins is TBBA. This is a reactive halogenated intermediate incorporated during resin preparation. However, other bromine containing species plus phosphorus containing monomers or curing agents may be reacted with the main epoxy resin components during polymerisation. The latter may be alkyl or aryl phosphates. The best appear to be phenyl phosphate derivatives. A large number of organic phosphorus compounds are available to provide flame retardancy. However, it is known that such additives do not generally provide sufficient protection in epoxy resins. They are not resistant to migration and affect the mechanical properties. As a consequence epoxies are often protected by bromine containing types. Flame retardant epoxy laminates are used often now in vehicle construction and for these Exolit AP 422 (Clariant) is available to provide flame-proofing properties. The new Exolit AP 750 is useful for epoxy coatings and gelcoats, with around 20-50 phr normally added. A team at Cheng Kung University (Taiwan) has found that a phosphorus containing reactive material produces less fumes and contributes to greater thermal stability than conventional systems containing TBBA. The material 2-(6-oxido-6H-dibenzo(c,e)(1,2)oxaphosphorin-6-yl)-1,4benzenediol, known as ODOPB, was converted into a phosphorus-containing epoxy material for use in an electronic encapsulation application. Later work by the same team compared ODOPB and bis(3-dihydroxyphenyl) phenyl phosphate (BHPP) as reactive flame retardants in o-cresol formaldehyde novolac epoxy resin. Since the ODOPB has a rigid, cyclic side chain structure, the resultant phosphorus-containing epoxy resin had a higher Tg, better flame retardancy properties, a higher modulus, and increased thermal

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stability compared with the conventional TBBA-containing epoxy and the linear, main chain BHPP epoxy resin. With ODOPB, a UL94 V-0 rating was obtained with a phosphorus content as low as 1.1% in the cured resins with no fumes or toxic gases detected. In contrast, 12% bromine is needed for the TBBA resin and 2.2% P with the BHPP approach. Another investigation in Taiwan has shown that the incorporation of silicon into epoxy resins provides an improvement of their flame retardancy. A silicon-containing oxirane, triglycidyl phenyl silane oxide (TGPSO) and the corresponding silicon-containing epoxy resins possess a higher char yield as well as higher LOI than commercial epoxy resins. Shell Oil has a patent covering the use of red phosphorus in a curable epoxy resin, US 5859097; and Hoechst have also disclosed phosphorus-based epoxy resin compositions in US 5854371. Another approach has been postulated in Taiwan, where a phosphorus-containing bisphenol is incorporated into naphthalene epoxy resins. A high Tg of 237 °C was obtained with a tetrafunctional naphthalene-containing epoxy and the use of a phosphorus-containing diol was better as a flame retardant than TBBA. Phosphorus-containing thermosets in air at 800 °C had a char yield of 11.5-22.2% whilst TBBA networks oxidatively decomposed with almost zero residue. It was concluded that the combination of a tetrafunctional naphthalene-containing epoxy resin with a cyclic phosphine oxide diol gave a high Tg and a high limiting oxygen index of 35. Alpha Owens-Corning offers a flame retardant vinyl ester resin that meets ASTM 84 Class 1 flame spread and smoke rating. The resin is a highly brominated bisphenol-A epoxy based vinyl ester. It provides a unique combination of good flame and smoke resistance and inherently good mechanical properties. The flexural strength of 34% glass composite is 5100 psi (35 MPa) and flexural modulus is 450 ksi (3.1 GPa). Epoxy resins can be made flame retardant with reactive halogen-free FRs attached to the polymer matrix. To achieve this the compounds must be miscible with commercial epoxy resins. Schill & Seilacher Struktol of Hamburg offer just such a material. Their reactive organophosphorus compound Struktol Polydis PD3710 can produce UL94 V-0 with 2-4% phosphorus in the polymer matrix. At the same time, a reduction in smoke density is achieved. This product is an example of what is termed a ‘combination compound’, based on cyclic organophosphorus chemistry, since it incorporates flame retardant properties with being a curing agent for the system. Indeed, it has toughening properties as well, making the compound a trifunctional entity. These combination compounds represent a modular system, in which the resin’s reactivity and subsequent properties can be adapted as appropriate. These may entail glass transition temperature, fire-smoke toxicity (FST) properties and toughness. Epoxy systems cured with combination compounds have low curing temperatures and improved FST properties. Because of the latency of the curing agent, combination resins offer the easy handling of one-component systems. This type of curing agent does not affect the basic viscosity of the resin used. The curing reaction can be triggered below 140 °C, whereas amine systems employed for aerospace composite primary structures require a temperature of at least 180 °C. These new combination curing agents have good handling properties in storage and processing. They can be stored at ambient temperatures; at which the compound is liquid and so can be metered and stirred easily. Because of the latent reactivity, it is possible to reduce curing temperatures and so reduce production costs.

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5.7.3 Phenolics Cellobond phenolic resins are available from Borden Chemicals in the UK. These resole resins are made with an excess of formaldehyde to produce a water-based polymer capable of crosslinking or curing purely by the application of heat. A range of grades is available for processing via the full range of composite techniques into inherently fire resistant products without the addition of flame retardants or fillers. They achieve Class 0 under BS476 Part 6 and Class 1 for flame spread under BS476 Part 7. The oxygen index is >55% and laminates pass the 3 m Cube Smoke Test as category 1. Under the French NFF 16-101 tests laminates are rated as M1F1 for flame spread and smoke/toxicity respectively. These factors, combined with the minimal levels of smoke and toxic emissions that are produced in a fire, make phenolics the product of choice in many areas where public safety is important. In the few cases where phenolic resins require a flame retardant addition, such as in paper and textile containing compounds, reactive flame-retardants like TBBA or additives such as organophosphorus compounds are used. Ammonium polyphosphate is also effective.

5.7.4 PU Casting Systems High amounts of ATH can be added to the polyol stream where PU casting systems need flame retardancy. To pass the UL94 V-0 test about 300 phr are required. The addition of red phosphorus and ATH is much more effective and does not affect the insulating properties of the resins. A typical formulation would have 100 phr of ATH and 20 phr of red phosphorus. Encapsulation resins from Dow Chemical are solvent-free systems sold under the Voratron name. Flame-retarded halogen-free versions are available that meet UL94 V-0 requirements. These polyurethane crosslinked resins are both insulating materials and act as a ‘construction’ material and housing for fixing electrical components in power distribution, transformers and cable joints.

5.7.5 Acrylic Resins MODAR Modified acrylic liquid resins have been available since the mid 80s and are used in closed mould and pultrusion technologies. When combined with ATH they offer low smoke; low toxicity fire performance in composites. These resins are more accurately described as ‘oligourethane-methacrylates dissolved in methyl methacrylate solvent monomer’. Crosslinking, through the methacrylate functionality on the backbone and the solvent is initiated in the same way as for unsaturated polyester resin by decomposing an organic peroxide, either thermally or chemically with an accelerator. Flame retardant laminates are produced by introducing ATH into the resin, the higher the loading, the better the performance. However, increased loadings lead to higher dispersion viscosity that can lead to processing problems. Since MODAR resins have a low inherent viscosity quite high loadings can be formulated, in conjunction with BYK W996 dispersing agent, and still achieve excellent fire performance and processing ability. The level of glass present will of course, influence these properties. Glass mat at 17 vol% is a typical composite. Table 5.2 shows the minimum ATH loading to meet some of the European fire specifications.

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Table 5.2 Fire performance of MODAR 835S laminates with 17 vol% random glass mat National Bureau Minimum ATH Dispersion of Standards Fire requirement (NBS) Smoke required * viscosity (Dmax) BS 476 parts 6 & 7 — 200 cps 70 phr Class 2 115 1500 cps ** 208 phr Class 1 116 2500 cps ** 250 phr Class 0 French NF-P92-501 M2 50 phr 200 cps 117 M1 150 phr 700 cps 102 German DIN 4102 B2 50 phr 200 cps 117 B1 150 phr 700 cps 102 German DIN 5510 S4/SR2/ST2 100 phr 300 cps 114 Italian CSE RF3/77 Classe 1 150 phr 700 cps 102 * Alcan LV63 or Martinal ON904 + 2 wt% BYK W996 ** Maximum dispersion viscosity for resin transfer moulding is accepted as around 1000 cps. So, under ambient conditions, these 2 dispersions are only suitable for wet press and vacuum moulding. Source of data: Ashland Specialty Chemicals

5.7.6 Dicyclopentadiene Dicyclopentadiene (DCPD) with or without a saturated polyester as a low smoke low profile additive can pass various building fire tests such as the German Chimney test or the British and French spread of flame tests at the highest or next but one classifications. Likewise an unsaturated polyester blended with methyl methacrylate can achieve such levels with either 120 phr of APP, 225 phr ATH and 25 phr APP, or with 300 phr of ATH. Similar formulations also pass German and US railway tests with 100 phr of ATH and 10 phr APP. Not only are these formulations highly flame retardant but they also fulfil smoke density and toxicity requirements as severe as those demanded by the aircraft industry. 5.8 Thermoplastic Polyesters PBT is one of the fastest growing engineering thermoplastics, driven mainly by the automotive and electronics markets, accounting for the majority of its use. This has occurred as PBT continues to replace thermosets in many electrical applications. The material has good dimensional stability, strength, low moisture absorption and excellent electrical properties. It is however, easy to ignite and so has to be flame retarded. This is usually achieved by relatively low loadings of brominated flame retardants in combination with antimony oxide. Electrical connectors are one of the largest volume applications of PBT and can be formulated to meet the V-0 class of the UL94 ignition test. Around 8% bromine content in the final PBT compound is sufficient to achieve the V-0 test rating for all types of brominated flame retardants, but some affect the physical and mechanical properties of the resultant materials more than others. Polymeric brominated styrene additives would be preferred in glass-filled compounds. Brominated polystyrene, such as Saytex HP-7010 from Albemarle Corp. and poly(dibromostyrene) are such materials. They retain excellent properties after heat ageing. High impact strength and excellent electrical properties are especially noted for HP-7010 due to the additive’s high purity and low aliphatic halogen content.

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Several recent patents concern thermoplastic polyesters for electrical goods. DuPont has disclosed a moulding composition for PBT, to which is added a reinforcement and a mixture of melamine pyrophosphate with an aromatic phosphate oligomer. The physical properties are reported to be good (EP 903370). BASF has a US patent (US 5712336) in which a thermoplastic polyester is flame-retarded with decabromodiphenylethane and two more additives. These are: • •

a metal oxide or metal sulfide or metal borate or a mixture of these, and an ester made from a carefully specified acid and alcohol.

Along with the makers of other polymers that are utilised in the electronics industry, PBT manufacturers have been concentrating on flame-retardant product grades that contain neither halogens nor antimony, since there is a reduction of electrical properties such as tracking resistance, plus the growing debate about potential toxicity hazards. Phosphorus-based systems (such as Ultradur B 4000 from BASF) are now available that have an incandescent wire resistance of up to 960 °C plus outstanding CTI values and meet the V-2 classification for UL94 down to a wall thickness of 0.4 mm. PBT from BASF in the form of Ultradur B4520 can be made flame retardant with a combination of cyclic diphosphonate ester (TPMP) and melamine. TPMP is available as Antiblaze 1045 from Albright & Wilson and comes as a colourless highly viscous liquid. TPMP modestly improves the flame retardancy of PBT. LOI rises from 21.9 to 23.5 or 26.7 at 10 or 20% loading and achieves V-2 in UL94. Co-addition of melamine to the TPMP leads to a strong increase of the LOI to 31.8 and helps to obtain V-0 rating. The optimum ratio between TPMP and melamine is 2:3 at a 20% total loading. There appear to be interactions between the additives as well as between the additives and PBT. It is likely that the combination of TPMP and melamine provides a dual mechanism associated with the condensed and gas phases. In the condensed phase, interaction between TPMP and melamine results in the formation of phosphorus-nitrogen containing solid residue. This residue, even at a relatively small yield can be very efficient because of its glassy-like performance providing superior barrier properties. On the other hand, TPMP + melamine significantly modifies the mechanism of thermal decomposition of PBT towards formation of amides rather than acids. The amides undergo dehydration, the water from which then cools the flame. White smoke is seen as the material self-extinguishes and is found to be benzonitriles that crystallise very rapidly and probably trap the free radicals in the flame. For flame-retardant polyester fibres the copolymerisation of phosphorus retardants is the most common method. However, a serious difficulty is that the phosphorus-containing polymer is easily hydrolysed. Work by the Toyobo Company Limited in Japan has shown that two identical PET fibres can offer differing properties depending on where the phosphorus compound is situated within the polymer chains. One has the addition as a side chain and the other an identical phosphorus compound in the polymer backbone. Both fibres had almost the same physical and flame retardant properties, yet the main-chain type hydrolysed around twice as fast as the sidechain type, and led to an immediate drop in toughness. This difference in hydrolysis properties is found to depend on whether a phosphonate ester bond is placed in the polymer backbone or a pendant site. In the case of the main-chain type, the scission of the polymer backbone occurs by hydrolysis of phosphonate ester bonds, whereas in the case of the side-chain type, this does not occur. The results of this investigation show that the polyester fibre with the side-chain modifier gives sufficient flame retardancy and excellent hydrolysis resistance.

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Work at North Carolina State University has shown that an inclusion compound melt processed into PET film provides substantial flame retardancy. The compound was formed between betacyclodextrin and the phosphorus-based flame retardant Antiblaze RD-1. The properties were much better than films containing the separate constituents on their own. GE Plastics’ non-halogenated, FR PET grade V9760NH contains 30% glass fibre reinforcement and is free of halogens and red phosphorus. A dedicated technology was developed for this material that combines its excellent plasticity with a wide processing window. 5.9 Polycarbonates Polycarbonate blends are a major constituent of computer housings. Traditional brominated FRs used in some markets are being replaced by fillers such as inorganic phosphates, as a nonhalogenated alternative. High inorganic loadings, however, can degrade mechanical properties. An environmentally benign approach through using lower inorganic loadings can be achieved using nanocomposites. One combination that has been studied is PC with montmorillonite clay (MMT). Blends made by extrusion have created difficulties and show a degradation of the molecular weight with development of colour. Processing leads to more exfoliation of platelets in the clay that causes two competing effects. A reduction of the peak heat release rate (HRR) because of the exfoliated platelets, versus degradation processes that increase the peak HRR. The dominant effect in low ash and/or low shear situations is reduction of peak HRR. The opposite is true with high ash or high shear since the peak increases. PC/ABS blends can be made FR with high efficiency brominated products that maintain high heat distortion temperatures and can obtain V-0 and 5VA ratings with no blooming or plateout on moulds. The loadings required will depend on the PC to ABS ratio of the formulation used. Plate-out has been a long-term problem with certain PC/ABS formulations, especially when based on triphenyl phosphate (TPP). Resorcinol diphenyl phosphate (RDP) brings some improvements versus TPP, but a better option is bisphenol A diphenylphosphate (BPADP). This shows excellent stability plus good flow with low volatility. It has a better melt stability and hydrolytic stability than RDP. Bayer has been developing grades of Bayblend, polycarbonate/ABS, based on a proprietary FR package free of bromine, chlorine and antimony synergist. A second generation is targeted mainly at business machine housings, kitchen appliances, personal care products, and home items such as vacuum cleaners. Although available as a developmental product for evaluation, it has been fully commercialised as Bayblend FR90. Eliminating halogens has improved thermal and light stability, and also helps avoid bloom and plateout. Avoiding antimony trioxide is important since, in the presence of heat and moisture, it can catalyse or accelerate the degradation of polymers like polycarbonate. The material has a UL94 V-0 rating at 1.4 mm thickness. Bayer offer a flame-retarded version of their Bayblend PC/ABS series that is halogen-free and suitable for extruded and thermoformed components destined for the E&E market plus the construction and automotive sectors, also extrusion grades. These can be readily made flame retardant with organophosphorus compounds. The good flow properties of these alloys have made them ideal for a wide range of injection moulding applications, such as thin-wall articles, within the E&E and IT sectors. Until the last few years, these very properties, including the plasticising effect of the FRs used, prevented adequate melt stability from being achieved and so precluded their use in extrusion. Bayer and GEP, with their Cycoloy range, have now introduced FR alloys of PC/ABS in extrusion grades. Bayblend FR3030 is offered with a required melt stability as created by use of non-

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Newtonian high molecular weight polycarbonates and specific, low-plasticising FR additives based on phosphorus. The new grades have excellent light stability, high heat resistance, good stresscracking and chemical resistance plus giving parts with excellent surface quality. These extrusion grades produce low levels of smoke, around half of a comparable PPO alloy, and on a par with rigid PVC, often the main material chosen for many extruded electrical components such as ducts, conduits, etc. Bayblend FR 3030 even satisfies the Airbus Industrie demands on toxic fumes potentially released in aircraft cabins. It also achieves V-0 at 1.6 mm in UL94 and 1 mm components pass the glow wire test at 960 °C. The materials pass the Epiradiateur test for building panels and the German ‘Bundesbahn test’ for parts in railway vehicles. There is potential as a replacement for rigid PVC over which it has a 30 °C advantage for use in electrical installations, and also has a 20% lower density (1.18) over the same material, thereby offering weight reductions for similar components. Samyang Corporation of South Korea has a phosphate based PC/ABS compound for use in domestic appliances and automotive interiors (US Patent 5864004). Borates are central to the formulations disclosed in Patent EP 892010 from Daicel Chemical Industries Inc. of Osaka, relating to polycarbonates. General Electric’s Patent EP862185 concerns flame retardant based on an aryl-containing silicone, which may contain triphenyl or diphenyl groups, together with a diorganic polysiloxane compound. It is claimed to improve the flame retardancy of polycarbonate without losing the transparency. Dow Corning Toray Silicone in Japan has proposed the use of a silicone-based FR for polycarbonate compounds. A heat treatment at 380 °C for polycarbonate containing the silicone material has been shown to generate a phenyl silyl ether linkage that appears to lead to flame retardancy for the formulation. 5.10 Other Thermoplastics Phosphorus may be incorporated into PMMA to reduce flammability. Work carried out at Salford University has shown that MMA may be reacted with diethyl(methacryloxymethyl) phosphonate (DEMMP) to form a copolymer that provides a better flame retardant performance than a compound to which diethyl ethyl phosphonate (DEEP) has been added. DEEP has a similar structure to DEMMP and it might be expected that the two compounds confer a similar degree of flame reatardancy to PMMA at similar loadings. The rise in oxygen index is similar, 17.5 up to 22 at 3.5% of phosphorus in each case. However, the MMA/DEMMP copolymer is more thermally stable and gives better FR properties. It turns out that the DEEP plasticises PMMA whereas the copolymer has similar physical and mechanical properties to unprotected PMMA. Fortron polyphenylene sulfide is utilised in lamp holders and adaptors. The Ticona family of materials have high heat resistance, inherent flame retardancy and good electrical insulating properties. Fortron 1140L4 is used in strip-lighting systems for low-voltage halogen lamps, while grade 61665A4 is injection moulded into insulating rings for lampholders. The US Federal Aviation Administration (FAA) has studied the fire behaviour of the engineering plastics that are now used as cabin materials. These would have a significant effect on postcrash fires that can pose the most serious threat to passenger safety. The results form part of a flammability and smoke properties database and create a benchmark for new fire safety systems. The materials examined included polycarbonate, polyetherimide (Ultem), polyamide-imide (Torlon), polysulfone (Udel), polyphenylene sulfide (Techtron), polyetheretherketone (PEEK)

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Flame Retardants for Plastics Market Report

(Ketron), polyimide (Vespel SP-1), polyphenylsulfone (Radel R) and sintered polybenzimidazole (PBI) (Celazole). These materials were unfilled or neat without any flame-retardant additives. Except for Ultem, none of the materials is widely used for aircraft interior applications. They were tested in a cone calorimeter under differing heat flux levels. Several materials did not exhibit sustained ignition at 35 kW/m2; neither Vespel nor PBI ignited even at 50 kW/m2. Blistering occurred with all samples plus a swelling of the top layer with the formation of a gas bubble. This bubble eventually released volatile gases that then ignited. Soon after flaming ignition, all materials showed char formation accompanied by surface swelling. The total heat release (THR) values of Ultem, PEEK and Torlon were significantly lower, by a factor of 10 when compared to PC, Udel, Radel R and Techtron. The charring character of the polymers greatly affects the heat release rate. Although a single peak HRR value cannot be used to assess overall fire performance, worthwhile comparisons can still be made if all materials exhibit similar burning behaviour. Torlon, PEEK, Vespel and PBI produced low HRR at high external heat fluxes between 50 and 75 kW/m2 and showed high char integrity. Polymers having low flammability either due to lower heats of combustion or heat release rates, also show lower smoke production rates. Total heat released and effective heats of combustion appear to be better parameters for assessing the relative fire performance of polymers.

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6 Suppliers and the Consumption of FR Additives and Compounds Chapter 6 reviews the supply chain and discusses the source of materials used by the resin suppliers and compounders. The market for flame retardant additives is discussed and some statistical data presented. 6.1 General Comments Various factors are affecting the growth of the additives industry, many of them business rather than technically related. Among them are foremost, the growth of plastics consumption and intermaterial competition, followed by a demand for shareholder value; pressure on margins; globalisation; health and safety issues; and plastics recycling or disposal. Major activity has been seen over recent times in acquisitions and divestments. This is driven by the need to increase shareholder value. While certain companies are focusing more closely on their core technologies, others are extending their current portfolios into related areas. Witco and Ciba had product swaps plus allied distribution agreements to enable each to concentrate on their individual technological expertise yet, at the same time, offer customers the benefit of ‘one-stop shopping’. Extending one’s product line has expanded Great Lakes and OxyChem into antimony oxide flame retardants through the purchases of Anzon and Laurel respectively in the late 1990s, so allowing them to offer these synergies along with their core halogenated flame retardants. Clariant had taken Albright & Wilson’s red phosphorus business on board back in 1997. Then Rhodia eventually topped Albemarle’s share offer for A&W, after a bidding war in 1999. Some health and safety issues are perceived to exist with certain plastic additives, such as halogenated flame retardants, along with some heat-stabilisers for PVC and various phthalate plasticisers. At present there have been no restrictions on any halogenated flame retardants, but there are some voluntary agreements limiting usage; more in Europe than in North America. Some suppliers are looking at non-halogenated replacements, such as inorganic hydroxides, melamines and various inorganic and organic phosphorus compounds. Growths of fire retardants is seen on a global scale to be 3-4% per year. The spread of chemistries that a combined group would offer become important for a specialised chemical company as customers are increasingly demanding the ‘one-stop shop’ for their requirements. Customer overlap is one driver for acquisitions plus the complementary product areas of flame retardants, surfactants, fine chemicals, water treatment and tertiary amines. It was estimated that only 40% of A&W sales, at most, are in markets served by Albemarle. Bromine suppliers are still looking for acquisitions in the non-halogenated sector to help spread the risk if the worst happens in the regulatory arena. Market consolidation of the chemical industry has resulted in 5 players accounting for more than half of US sales, these are: • • • • •

Great Lakes, Albemarle, Occidental (OxyChem), Dead Sea Bromine and Akzo Nobel.

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In addition we are seeing increasingly a move away from a specific chemistry by the main suppliers. For instance Great Lakes, the No. 1 brominated company, has added phosphorus and antimony products through their acquisition of FMC Process Additives and Anzon respectively. Trends seen in customer markets for engineering thermoplastics are the need for higher thermal stability because of miniaturisation, interest in non-halogens and the wider use of polymer blends to achieve FR performance. Thermoset requirements will include non-halogen FR-4 printed circuit boards, higher heat distortion temperatures in polymers and the impact on FRs of the changes in PU blowing agents, plus the use in PU foams of non-diphenyl ether types of FR. Trends in PVC are perceived as increased concern over smoke generation and the need for greater low temperature flexibility in wire and cable. 6.2 Suppliers This section provides comment on the major manufacturers and suppliers of flame retardant additives and materials. Table 6.1 lists suppliers of different types of flame retardants. Since the mid-1990s, when even the biggest flame retardant suppliers were specialist companies, at least within the plastics industry, there have been many consolidations and the biggest companies now have a wider range of FR types within their portfolios. Another change is that during this period, some of the larger FR suppliers now either belong to larger additive manufacturers, like Ciba and Clariant, or themselves have become multi-additive companies in the manner of Great Lakes Chemical Corporation.

Flame retardant type Brominated materials

Chlorinated materials Antimony trioxides Alumina trihydrate

Magnesium hydroxide

Zinc borate Phosphorus materials

Intumescent materials Melamine Silicones Other inorganic materials

Table 6.1 Suppliers of flame retardants Suppliers Albemarle Corporation, Dead Sea Bromine Group including their subsidiary Eurobrom, Great Lakes Chemical, Atofina, Ferro, Clariant, Toso Atofina, Clariant, Occidental, Akzo, Ineos Chlorine Campine SA, Mines de la Lucette, Ferro, Great Lakes (took over Anzon) Alcan Chemicals, Martinswerk (part of Albemarle), Great Lakes, Solem Europe, Alcoa, Climax, Huber Engineered Materials, Ciba, Nabaltec, Omya Alcan Chemicals, Eurobrom (Dead Sea Bromine), Martinswerk, Premier Periclase, Solem Europe, Britmag, Flamemag International, Martin Marietta Magnesia Specialties, Kyowa Chemical, Huber Borax Consolidated, Climax Molybdenum, Joseph Storey, Alcan Chemicals Albright & Wilson (now part of Rhodia), Akzo, Clariant, FMC Corporation (now a subsidiary of Great Lakes), Olin, Bayer, Italmatch Chemicals, Solutia, Unitex Chemical, Nordmann, Rassmann Clariant, Himont Ciba, Akzo, Chemie Linz, Cyanamid, Atofina Dow Corning, GE Bayer Alcan Chemicals, Amspec, Anzon (subsidiary of Great Lakes), Climax, Morton International, Sherwin-Williams

Companies traditionally operating with brominated compounds continue to expand their product lines with non-halogenated retardants, such as boron and phosphorus compounds. In early 2001

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Great Lakes Chemical Corporation inherited the Reoflam line of phosphate ester FRs after acquiring the process additives division of FMC Corporation. Albemarle Corporation introduced its new phosphorus-based range with NcendX P-30 from an 11,000 tpa plant in Orangeburg, South Carolina. The company has also teamed with the Borax Corporation to develop halogen and halogen-free flame retardants, as well as supply zinc borate flame and smoke-suppressing agents to Asian markets. The rest of this section provides further background about the supply chain.

6.2.1 Brominated Flame Retardants Since the decline of dibromoethane as a petrol additive, the major use for bromine has been in fire retardants, mainly in plastics. In 1997, production of Br was 470,000 t. The largest volume brominated flame retardant, accounting for about half the market is tetrabromobisphenol-A (TBBA), used in printed circuit boards. The second largest, taking about 10% of the market, is decabromodiphenyl ether, widely used in casings for TVs and computers. Mixtures of polybrominated diphenyl ethers are also found in treated furniture. A third major FR is hexabromocyclodecane, used primarily in polystyrene foam and also in textiles. Production of the raw material, elemental bromine, is dominated by the three major companies; Albemarle, Dead Sea Bromine and Octel, part of Great Lakes. This production is concentrated in the US and Israel, The former has over 50% and the latter around 30%. China, the UK, France and some Central Asian republics are other sources. The US and Israel produce bromine from brines that are far more concentrated than the ocean’s, especially the Dead Sea with 14,000 ppm compared to only 65 ppm in the former. The leading makers of BFRs are Albemarle and Great Lakes in the US, Atofina in France, Dead Sea Bromine in Israel and Tosoh Corporation in Japan. US company Albemarle has been very much to the fore in the development of processes to reduce or eliminate risks associated with the production of BFRs. The middle of 1997 saw the completion of 3 years of research into a new process that eliminates methyl bromide, a highly regulated compound, as a by-product in the production of certain brominated compounds. Albemarle built a worldscale plant of 50,000 tonnes in 1999 for the production of TBBPA at Magnolia, Arkansas that uses the new process. At the end of 1998 Albemarle, Jordan Dead Sea Industries (Jodico) and Arab Potash Company (APC) signed a JV agreement to make and market bromine and bromine derivatives from a world scale complex to be built in Jordan near the Dead Sea. The new company, Jordan Bromine Company, has units to manufacture bromine, TBBPA and calcium bromide near to the APC site. Bromine containing brines are provided from APC’s existing solar evaporation pans. Chlorine, which is used in the manufacture of bromine, will be sourced from an adjacent plant. Albemarle will provide the venture with process and engineering technology in addition to marketing, customer service and manufacturing expertise. Ferro Corporation sold its Pyro-Chek named products business, made in both the US near Chicago, and France, to Albemarle Corporation at the beginning of 2000, along with the French plant. Investment in the French unit, at Port-du-Bouc, by Ferro ensured that new developments in the brominated polystyrene FR family were completed and the new owners also benefit from the additional environmental improvements to achieve reduced atmospheric emissions during manufacture.

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Great Lakes Chemical Corporation has generated new offerings from all parts of its FR portfolio. Two relatively new materials are Firemaster PBS64 and PBS64HW, based on its unique dibromostyrene monomer. These are aimed at engineering plastics such as polyamide and polyesters for small parts including connectors. The new materials offer improved flow characteristics and higher thermal stability. The Dead Sea Bromine Group has formed joint ventures in both China and Japan to enhance its presence in world markets. In China it has teamed up with Ochean Chemicals, the largest Chinese producer of bromine. The second JV is with DKS of Japan to produce and market worldwide products based on DKS’s technology. Dead Sea Bromine has also started up a large facility for the manufacture of poly(pentabromobenzyl) acrylate, a flame retardant used in polyamides and thermoplastic polyesters. Albemarle is adding 37,500 tonnes of TBBA capacity at Safi, Jordan through its JV with Arab Potash, due to start up at end 2002. Globally bromine capacity in 2000 was 570,000 tonnes, with the top three having 35% at Dead Sea Bromine, Great Lakes 30% and Albemarle 20%. Over all FR products Great Lakes is the world’s largest manufacturer, with Albemarle in second place.

6.2.2 Melamine Melamine production capacity in Europe is around 360,000 tonnes. DSM had the largest capacity with around 25% in 1999. Agrolinz Melamin, producing in Italy and Austria has expanded from 100,000 tonnes to 130 kt by the end of 2000. This means they have claimed the first spot from DSM. BASF has 65 kt capacity and Atofina around 26,000 tonnes. Most is used for thermoset resins and adhesives, but a significant proportion goes into flame retardants. Further capacity exists in Romania and Poland. Melamine FRs are a small but growing market. In 1996, DSM merged the melamine FR activities of DSM Melamine and the fine chemicals operation of DSM Chemie Linz to form DSM’s Melapur BV, which became the largest producer of such additives in Europe. Ciba Specialty Chemicals increased its flame retardants portfolio in May 2002 by purchasing DSM Melapur Flame Retardants, a leader in melamine-based technology, mainly utilised in engineering plastics for the automotive and electrical & electronic sectors. This complements their Flamstab technology, used for polyolefins. Ciba will retain the Melapur trademark and the two companies are expected to work together to find new flame-retardant methods based on melamine chemistry.

6.2.3 Phosphorus Flame Retardants The 1999 purchase of FMC Corporation’s Polymer Additives Division has resulted in about half of Great Lakes Corporation’s $800 million turnover being in flame retardants. These cover bromine, antimony and now FMC’s phosphorus expertise. FMC had two sites, one at Trafford Park, Manchester, England and the other in Nitro, West Virginia, US. By extending their product platform, Great Lakes now offers halogen and nonhalogen based flame retardants. In conjunction with their other additives for polymers, such as antioxidants and stabilisers, the company provides customers with a comprehensive portfolio of integrated additives second to none in the market. A major benefit from the combined flame retardant range to Great Lakes is FMC’s ability to meet the FR needs of polymer applications such as PC/ABS blends for office equipment.

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Consolidation has continued among producers of flame retardants. Apart from the Great Lakes activity recorded above, Akzo acquired the phosphorus FR activities of Courtaulds. Albright & Wilson (A&W) sold their red phosphorus business to Clariant. The next year A&W accepted an offer from Rhodia via an Austrian company, ISPG to acquire the phosphorus chemistry activities, including FRs. This was the outcome of a bidding contest between Rhodia and Albemarle. The A&W purchase makes Rhodia the world’s largest operator in speciality phosphate chemicals. Akzo has been increasing capacity for Fyrol PCF, its trichloropropyl phosphate, both in Germany and the US. Great Lakes has produced Firemaster BZ54 for the flexible PU foam market and offers advantages over conventional chlorinated phosphate esters, such as lower loadings. It is well suited to the requirement of non-CFC blowing agents, exhibiting lower scorch than when alternatives are utilised. Reofos BAPP, a bisphenol A diphosphate and Reofos 507, butylated triaryl phosphate, are other new grades aimed at overcoming problems in engineering thermoplastics such as stress cracking and plate-out sometimes found with FR packages used in PC/ABS and PPO/PS blends.

6.2.4 Mineral Filler Flame Retardants The market for antimony oxides is dependant on PVC and brominated FRs, since the trioxide works as a synergist with halogens, whether in the polymer itself or as an additive. Raw materials are a key cost at around 80% of the product. Bolivia and Guatemala have closed their antimony ore mines due to low prices and China is now the leading source of antimony ore. Alcan Chemicals Europe, a major source of flame retardants, mainly mineral based aluminium and tin compounds, has been put up for sale by parent Alcan Canada. Magnesium hydroxide has to compete with ATH as a mineral filler FR. ATH is widely used in thermoset polyester and some elastomers, but is finding increasing use in EVA and other ethylene copolymers. Prices range from as low as 20p/kg up to 80p/kg for specialised grades. By contrast, magnesium hydroxide, used in PP and PA that are processed at too high a temperature for ATH, costs from 60p/kg up to £1.50/kg. Magnesium hydroxide is used in wire and cable, roof membranes and a widening list of specific polyolefin applications. A proper comparison has to be with the fine precipitated grades of ATH for which the worldwide market is around 100,000 tonnes, compared to about 20,000 tonnes for magnesium hydroxide. Currently, producers in Japan are seen as Kyowa Chemicals Industry and Tateho of Japan. Kyowa have a combined capacity of around 18,000 tonnes since opening a second plant in the Netherlands during 1999. Tateho have a recently opened plant of 12,000 tonnes capacity. In addition, Magnifin, a JV between Alusuisse-Lonza and Veitscher Magnesitwerke, has a 10,000 tpa plant in Austria; and Dead Sea Periclase has a 6000 tpa in Israel. Flamemag International has a pilot plant in Australia to prove a new hydrothermal process, with plans for a 10,000 tpa commercial unit to be built around 2002. Flamemag is another JV, between Queensland Metals Corp. and Mines de la Lucette the French company. Great Lakes has brought out uprated antimony oxide-based grades. Fyrebloc 100 and Fyrebloc 101 are 100% active formulations using a halogenated carrier giving excellent flow and thermal stability that improve processing and handling. Albemarle purchased Alusuisse Martinswerk GmbH, based at Bergheim, Germany, from Alcan Inc of Canada in mid-2001, this sale being one of the conditions to comply with the European

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competition requirements for Alcan’s purchase of the Alusuisse-Lonza Group during 2000. Martinswerk also has a 50% stake in Magnifin Magnesia Produkte GmbH based at St Jakobs/Breitenau in Austria. This stake has also passed to Albemarle. This has made Albemarle the leader for ATH and MDH mineral FRs.

6.2.5 Borate Flame Retardants At around the beginning of 2000 Albemarle began a joint development programme with Borax Corporation to create new, more versatile flame retardant technologies. These were to be new options in both halogenated and halogen-free systems for polymers. A challenging target was set to explore borate FR chemistry and the broader use of borates in polymers beyond the traditional outlets in PVC, polyamide and epoxy potting compound applications. Future growth opportunities in styrenics, engineering plastics and other resins would take advantage of the low toxicity and FR performance of zinc borates. Borax had been planning to grow this aspect of their business and felt that Albemarle was an excellent partner who has an extensive background in FR chemistry and long-standing ties with the polymer industry. Equally, a link with Borax provides another strand for Albemarle as they broaden their FR capabilities. Albermarle has expanded its inorganic bromide capabilities at its production operation in Thann, France.

6.2.6 General Saytex and NcendX are the cornerstone of Albemarle’s portfolio from the late 1990s with a 50,000 tpa expansion for Saytex RB-100 material, demand for which had been increasing at 7-10% a year. A more recent addition has been Saytex CP-2000, a continuous process, and high quality tetrabrominated product and NcendX P30, a bisphenol A based phosphate product being targeted at the PC/ABS materials, with a 12,000 tpa unit opened in early 2000. Albemarle Corp. is involved in a JV in China for the manufacture of various polymer additives including flame retardants. The US company and Jinhai Chemical & Industry Co. will jointly sell and export these products from the new enterprise. Non-halogen FRs for styrenics and new brominated platforms are part of the Great Lakes strategy for future developments. For polyolefins, the priorities are non-blooming, no plate-out materials as well as non-halogen materials. 6.3 Consumption and Market Data As reported before, the publication of dedicated statistics for the consumption of flame retardant additives is intermittent and mostly retrospective, with few ‘current’ estimates. However, various consultancies do regularly issue reports covering plastics additives as a whole, in which are included figures for FR materials. Estimates for the world market for BFRs at the end of the 90s was around 1m tonne/year, with the US and Europe taking more than 70% of global consumption, Japan around 14% and the rest elsewhere in Asia. Global growth rates are said to be 7-8% with Asia the fastest sector of all. Comprehensive figures have been issued by Townsend Tarnell (Table 6.2). Townsend Tarnell in 1996 said that FR growth worldwide would average 5% to 2001.

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Table 6.2 World market for flame retardants in plastics in 1996 (tonnes) Material type

Europe

North America

Asia

Antimony-based 18,000 20,000 35,000 Brominated 53,000 67,000 97,000 Chlorinated 16,000 16,000 11,000 ATH 90,000 150,000 75,000 Phosphorus65,000 48,000 30,000 based Others 15,000 13,000 7,000 Total 257,000 314,000 255,000 Source: BRG Townsend Inc., reproduced with permission.

Rest of the World

Total

2,000 7,000 2,000 10,000

75,000 24,000 45,000 325,000

Growth pa 19962001 % 3 6 1 5

5,000

148,000

4

little 26,000

35,000 852,000

7 5

In the US, Business Communications Corporation (BCC) predicted 5% growth in FR consumption until 2003. The highest growth was expected for phosphorus-based FRs, at 7%, and brominated FRs with 8.5% (Table 6.3). BCC data show that ATH was the largest volume market. Table 6.3 Estimated consumption of Flame retardants in the USA (tonnes) Annual growth Product type 1998 2000 2003 (%) Antimony-based 27,670 29,030 30,845 2.2 ATH 135,173 143,790 157,400 3.1 Brominated 94,350 111,130 142,000 8.5 Chlorinated 36,740 38,100 40,825 2.1 Phosphorus-based 40,370 46,267 56,700 7.0 Magnesium-based 3,175 3,630 4,080 5.0 Others 6,350 6,800 7,710 4.0 Total 343,828 378,747 439,560 5.0 Source: Business Communications Co. Inc.

A more recent study by Freedonia for the US market gives growth there to be a little less, at 3.7% pa; from 450,000 tonnes in 2000 up to 540,000 tonnes by end 2005. Details are shown in Table 6.4. Table 6.4 USA demand for flame retardants – 2000-2005 (000 tonnes) Annual growth Type of additive 2000 2005 (%) ATH 156 177 2.5 Bromine compounds 120 147 4.2 Phosphorus-compounds 70 86 4.3 Antimony oxides 33 43 5.4 Chlorine compounds 27 29 1.6 Boron compounds 23 27 3.7 Others 26 34 5.3 Total 455 543 3.7 Source: Freedonia Group, reproduced with permission.

European consumption in 1998 for flame retardants has been given as 27% of the market with North America at 31% and the Asia-Pacific region taking 38%. BCC estimated that in 2001

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404,000 tonnes of FR were consumed in Europe, to rise by 4% pa to 491,000 tonnes in 2006. Growth may increase if stringent fire safety requirements are established for the E&E sector. Frost & Sullivan in a European study gave FR additives at a volume of 261,000 tonnes in 1995, up to 291,000 tonnes in 1998, with an estimated growth of 3.8% a year to become 377,000 tonnes in 2005. Estimated volume shares and changes to 2005 were listed as follows: • • •

ATH 45% in 1995 unchanged by 2005 Brominated types 25% drop to 20%+ Antimony oxide from 7.5% down to 5.7%

The drops will be made up by several other families, mainly melamine, magnesium hydroxide, zinc borate and zinc stannate. There are about 30 players, according to Frost & Sullivan, in the European market (Table 6.5, Figure 6.1). Table 6.5 Revenue breakdown of the European flame retardants market (2000 and 2003) 2000 2003 Brominated flame retardant 32.4% 31.8% Phosphorous based 29.7% 28.8% Aluminium trihydroxide 14.7% 16.1% Antimony trioxide 10.9% 10.4% Chlorinated flame retardant 4.4% 4.2% Melamine based 3.6% 3.6% Magnesium hydroxide 2.5% 2.9% Zinc borate 1.4% 1.6% Zinc stannates 0.32% 0.43% Others 0.10% 0.14% Source: Frost & Sullivan 2001, reproduced with permission.

Melamine based 3.6% Chlorinated flame retardant 4.2%

Magnesium hydroxide 2.9%

Zinc borate Zinc stannates 1.6% 0.4% Others Brominated flame 0.1% retardant 31.8%

Antimony trioxide 10.4% Aluminium trihydroxide 16.1%

Phosphorous based 28.8%

Source: Frost & Sullivan

Figure 6.1 Total flame retardant chemical market: percent of revenues by product type (Europe), 2003

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Freedonia, a US research company, estimated that FRs for plastics accounted for 440,000 tonnes of material in the US in 1998, worth some $725 million. Growth in value terms is given as 7% a year as regulatory and environmental factors spread. About 25 million tonnes of PP are consumed worldwide with an average growth of 7% annually. Only about 1% of this PP consumption volume is flame retarded. Until 1998 the market requirement for the standard of flame retardancy was estimated as: • • • •

UL94 V-0 @ UL94 V-2 @ DIN 4102 B 1 @ others

63% 23% 12% 2%

Since then, a range of applications now calls for V-0 rather than V-2, which has increased the call for further high flame retardancy. The average growth for FR PP is around 8% per year. Brominated FRs are the most widely employed for PP. The use of non-halogenated FRs is limited because of insufficient thermal stability during processing or the high loading needed to obtain good flame retardancy that may compromise the resultant physical properties of the compound. Estimates of consumption of the different FR families gives: • • • •

Non-halogenated TBBA derivatives Decabromo and similar Other Br/Cl types

24% 19% 29% 28%

Flame retardant applications for PP are proportionately much less important than for other resins such as styrenics and engineering thermoplastics; less than 5% of the total FRs consumption is used in PP. This is mainly due to the difficulty and cost in reaching the high standards of flame retardancy required in electronics and building industries with PP compounds. The cause of this difficulty is the high crystallinity and flammability of PP. Brominated FRs had sales in 2000 of $900 million (global). Market shares are: • • • •

Great Lakes Albemarle Dead Sea Bromine Others

31%, @ $271.7 million 23% 22% 24%

In 1998, FRs accounted for roughly 13% of the global additives market, at almost $2 billion. In 1999, the total plastics additive market was $15.5 billion Global growth for FRs is estimated to be 5% a year: • • •

North America @ Asia-Pacific @ Latin America @

6% as average of 4-7% (to be 1.5 billion lb by 2003) 7-9% 6-8%

US demand for flame-retardants was expected to grow by over 4% pa to 1500 million pounds weight by 2003. Plastics account for almost 80% of this demand, according to Freedonia.

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The three most important markets for FR plastics are construction, electrical and electronic devices, and motor vehicles. The best opportunities lie in the electronics sector where strong growth in consumer electronics and wire and cable applications is driving the demand for higher-value, speciality grades of flame retardant plastics. Environmental concerns over brominated, and other halogenated products will negatively impact on their future growth as end users pursue less controversial substitutes including non-halogenated phosphorus, magnesium hydroxide and silicone compounds. SRI Consulting issued a new study on flame retardants in November 2002, in which they give the total market for flame retardants in the United States, Western Europe and Asia in 2001 as more than 1.2 million metric tons and valued at almost $2 billion. This market is expected to grow at an average annual rate of about 3.0-3.5% per year on both a value and a quantity basis over the 20012006 period, exceeding 1.4 million metric tons valued at just under $2.4 billion. The United States has been the largest consuming region with 32% of the total, followed by Western Europe (29%), Other Asia (21%) and Japan (19%). Flame retardant consumption reached a peak during 1999/2000 but has suffered severely with the economic downturn of 2001. Although the economic conditions affected all products, durable goods requiring flame retardants were hit especially hard. These include electronic and communications equipment, construction and transportation markets. Asia Pacific, excluding Japan, represents the most rapidly growing market for flame retardants since manufacture of consumer goods requiring flame retardants has been migrating to this area. Currently, most use is in printed circuit boards and housings for consumer electronics and business machines for export, so these products must meet the flame retardant regulations of the destination countries. However, as the standards of living in the Asia Pacific countries continue to rise as the area recovers from recent economic downturns, both rapidly increasing regional demand for the products themselves and domestic regulations requiring flame retardancy are expected to follow. The major flame-retarded resins in this region are epoxy and phenolic resin (for printed circuit boards) plus acrylonitrile-butadiene-styrene (ABS) and polystyrene (for consumer electronics and business machine housings). The growth in Japanese flame retardant consumption is expected to be less than Other Asia because of a shift in production to those areas. The Bromine Science and Environmental Forum in Brussels gave the global FR market as worth $2.2 billion in 1998. Brominated compounds made up 39%, inorganics took 27% and phosphorusbased compounds at 24%. Chlorinated compounds took 6% with the remaining 4% taken by melamines. Other, US firms, including Merrill Lynch arrived at a similar value total, but gave a slightly differing breakdown of types. The market for flame retardants in 2000 globally was estimated as $2.16 billion. This was broken into bromine 34%, phosphorus 22%, antimony oxide at 17%, ATH 14%, chlorine-based at 7% and others on 5%. When fillers and colourants are excluded then flame retardants take about 12 wt% of the global tonnage for performance additives on 2001 figures of roughly 8.5 million tonnes. This is second only to plasticisers that take a massive 59%, mainly in PVC. In tonnage terms more than 900,000 tonnes where sold in 2000 (Table 6.6). The market for flame retardants depends as much on the overall growth of plastics consumption as it does on any increase in FR requirements within a plastics application per se. There is anticipated growth of 5.5% a year for the rest of the decade in plastics consumption (in Europe). The European market for FRs came to around 380,000 tonnes in 2000, with a value of around 275 million euros.

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Table 6.6 Worldwide demand for flame retardants - 2000 Type of additive % ATH 42 Bromine-containing 21 Phosphorus-containing 17 Antimony oxides 8 Chlorine-based 6 Melamine 3 Magnesium hydroxide 2 Others 1 Source: Filler Consulting, Austria

6.4 Compounding for Flame Retardancy It is important to realise/remember when formulating a compound with a particular type of flame retardant that other additives included may have adverse effects on the efficacy of the FR capability. The presence of carbon black, mineral fillers, UV or antistatic additives may well alter the behaviour of the resulting compound. Oils or organic pigments may likewise have detrimental effects and so need to be excluded or replaced in the final formulation. One important reason why these additives may have a negative impact on flame retardant properties is that their chemical structure inhibits the formation of halogen radicals, when a bromine or chlorine containing FR is employed. If these radicals are trapped before they are able to curtail the material degradation process, there is a dramatic reduction in the efficacy of the flame retardancy. It is always advisable to carry out tests when generating new formulations. Table 6.7 gives some examples of other additives giving problems with specific FR agents: Table 6.7 Impact of other additives on flame-retardant materials Flame retardant Detrimental additives Chlorinated paraffins Carbon black Antimony trioxide Calcium carbonate (at low levels) Brominated compounds Ethoxylated amines (antistatic) at high levels Phosphorus-based compounds Comonomers such as EVA ATH at levels >60% Specific organic pigments Intumescent systems Mineral oils at high loadings Borates Stearates at high loadings

In preparing compounds with FR content, it is necessary to achieve a certain metering accuracy, if the main polymer resin has not already been purchased as an FR grade. Uniform dispersion of the FR additives is also most important for coat efficiency. The percentages added may fluctuate from quite low levels to very high ones for inorganic, dependant upon the required level of FR performance and the type of polymer used. If the amount of additive is so high that a masterbatch or concentrate cannot be used, then traditional mixing is employed. The advantage of working with a mix is that it is possible to produce a finished compound with all the required properties, such as UV resistance, suitable colour and high elastic modulus, for example. The drawback is that the concentration of the additives in question is pre-determined and any corrections have to be introduced at the development stage of the formulation. Masterbatches are used in applications where a high degree of dispersion of a low, final concentration of an FR and/or

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other additives is required. Here, the advantage is that it is possible to make corrections to the concentration. Flame retardant additives are no different from any other plastic additive. There are a number of characteristics that must be known and understood to properly use any plastics additive. Structure and the molecular weight for a specific FR additive affects the toxic nature of the product, the inherent physical properties and the ultimate use of the FR additive. Important attributes include melting point, particle size, decomposition temperature, and solubility among others. Most halogenated FRs suitable for use are monomeric molecules. Although oligomeric and polymeric FRs do exist commercially, they are generally used in higher heat engineering resin systems. When selecting a FR for a thermoplastic is to best match the melt point of the FR with the processing conditions of the polymer. Also it is sensible to select the FR that has a decomposition temperature similar to the combustion characteristics of the polymer. A promising approach toward reducing flammability of polymer systems is to alter the condensedphase chemistry at elevated temperatures. Structure modification can alter the decomposition chemistry to favour transformation of the polymer to a char residue. Such an increase occurs when thermally induced stable crosslinking structures and/or aromatic rings are produced. Work by the Brooklyn Polytechnic in New York has examined systems such as polystyrene, aramids, PF resins and nitrile polymers such as SAN. Styrene-acrylonitrile copolymers are strong, rigid and transparent. They have excellent dimensional stability, high craze resistance, but their flammability requires retardation for designed end-uses. The effect of zinc chloride decreases the initial thermal stability of SAN but char yield was significantly increased. High temperature FTIR showed that zinc chloride complexes with the nitrile group. This, in turn, induced a modified degradation mechanism leading to thermally stable triazine ring formation which crosslinked the main chains. One shortcoming of the so-called ‘fire-smart polymers’ approach to flame retardancy is that polymer manufacturers usually prefer to optimise their product for properties other than flame retardancy, so that introducing structures to favour flame retardancy may mean a compromise of other properties. Moreover, putting in specialised functional groups often means increased cost. Therefore a good strategy would be to try to utilise, as crosslinking sites, those latent functional groups that are already present in commercial polymers.

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7 End-User Market Sectors 7.1 Automotive Automotive foams may be made more flame retardant by the incorporation of phosphorus polyols that are bound to the foam matrix by hydroxyl groups. Clariant offers grades of its Exolit range that are non-halogenated additives for flexible polyether slabstock and moulded foams. Benefits of the Exolit range are low emissions, high ageing resistance, good odour characteristics and high efficiency. Exolit OP 550 is a low-fogging additive that is recommended for moulded and high-density slabstock foams where flame retardant efficiency is uppermost. OP 551 (TP) is a low-fogging liquid flame retardant for slabstock where a lack of discoloration is critical. Exolit OP 560 (TP) has appropriate emission characteristics to satisfy the latest VOC values to comply with the standard Daimler-Chrysler PB VWT 709 test procedure. This product gives a good balance between high efficiency and good ageing performance and exerts only a slight influence on mechanical properties. The Exolit OP range can be used in conventional production facilities by direct injection into the mixing head. The products should not be pre-mixed with polyols or polyol formulations because they are only partially soluble in polyether polyols with low hydroxyl numbers and they hydrolyse slowly in the presence of water. Materials in car interiors need to meet a horizontal flame spread rate of no more than 4 in/min (102 mm/min), when tested according to US Federal Motor Vehicle Safety Standard 302 (FMVSS 302), however, the results of this test have been shown not to predict fire hazard. Fire fatalities in highway vehicles, although occurring in much smaller numbers than in buildings, do represent significant numbers. In 1997, there were 88 such cases in the UK and 450 in the USA. Careful studies by respected fire performance specialists have examined typical plastics materials taken from a random selection of current vehicles, such as dashboard components, door and headliners, seats and other trim, plus a further selection of commercial plastics available on the open market for any and all applications. Results indicate that while there are significant differences among vehicles, the large majority of car interior materials tested (a random yet indicative cross-section) represent a fire performance that is, at best, mediocre. Moreover, the comparison between the two sets of materials shows that car interior plastics are likely to ignite much faster than commercially available plastics and release heat almost twice as fast. The fire hazard consequence of the analysis is that flashover in the vehicle interior does not require large ignition sources. Thus, even very small ignition sources can generate a large enough fire so that ease of exiting the vehicle is going to be severely hampered. In 2001, influential groups such as the US Fire Retardant Chemicals Association and the US National Association of State Fire Marshals had at last started to consider ways to develop alternatives to test requirements based on FMVSS 302, or its equivalent ISO 3795. Fire test requirements for the acceptability of automotive interior materials should be changed so that materials with improved fire performance are used in future. Since the fire performance of typical car interior materials seems to be poorer than that of conventional plastic materials that can be found commercially in the market place, then improvements in automotive materials fire performance should be easily achievable. This can result from either using intrinsically safer plastic materials or from adding flame retardants to existing materials.

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7.2 Other Transport Composites are increasingly becoming the material of choice in the manufacture of rail vehicles. The reasons for this are varied and include high strength to weight ratio, low maintenance costs, ease of installation and the facile reproduction of complicated designs. Common in-service examples include toilet modules and interior panelling. Phenolics have an advantage over other resin matrices due to their unique chemical structure that makes them inherently fire resistant. They do not readily burn and if involved in a fire, produce minimal levels of smoke or toxic fumes. Phenolic resins are traditionally orange/brown in colour and will progressively darken on exposure to UV light. To overcome this, phenolic surface pastes or in-mould primers are used to maintain the fire performance of the final composite whilst providing a smooth, pinhole free surface onto which fire retarded paints can be applied. It is this system that is used for the most stringent of applications – the interior of underground trains which are designated as Category 1a under BS 6853, the 3m cube smoke test. Rolling stock within this classification is defined as having ‘Substantial operating periods in a single track tunnel with no side exit to walkway and escape shaft, or, sleeper cars which operate underground for significant periods, or, trains that operate without staff’. Railway companies all over Europe and in the USA now use trains containing phenolic components; both internal for panels, luggage racks and toilet modules; and for external parts such as massive front ends, window frames and, more recently, for panels made in a sandwich of PVC foam cores and phenolic skins. Window frames for the Madrid Metro meet the M1F1 French standard and parts made by Mitras Composites UK conform to Category 1b of BS 6853 for ADtranz, a major rail vehicle manufacturer. Fire safety is now taken extremely seriously for underground and enclosed-space applications. The London Underground rail system has taken to using silicone glass and phenolic glass laminate materials. They both are approved to specification SE 970 and have excellent properties under fire propagation and spread of flame test conditions, plus low toxicity. Silicone glass is used for many insulation jobs underground and both materials are finding widespread use in critical locations on the London network. Lower loadings of halogen-free flame retardants are to be welcomed in the transport sector where low smoke density is required and lighter weight composite components are increasingly specified. The European railway sector has been anticipated to double its use of reinforced plastics between 2000 and 2005, up to at least 100,000 tonnes. The biggest growth is expected in glass-reinforced polyester composites, in above-ground rolling stock; but they must have a low heat emission rate and low smoke and toxic fumes in the event of a fire. To avoid halogenated resins, which generate smoke and toxic fumes during combustion, ATH has been utilised, yet high loadings are required leading to mechanical and processing difficulties. Phosphorus-based retardants are effective in thermoset resins, by dehydrating the pyrolysing polymer, forming unsaturated compounds with subsequent charring. The non-volatile polymeric phosphates thus formed provide a glassy coating for the carbonaceous layer that is forming at the same time. This coating inhibits the pyrolysis reaction and shields the underlying polymer from oxygen and radiant heat. In the company of special synergists, a protective coating in the form of an intumescent layer can be formed in the case of a flaming situation; and flame-retardants based on phosphorus are also good suppressors of after-glow and smoke. Such properties are of particular interest to formulators of gelcoats. Exolit AP 740 from Clariant meets the demand for halogen-free materials for various composite-processing routes; such as resin transfer moulding and pultrusion, at fairly low addition

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rates. 50 pphr of this additive can allow the Epiradiateur test, NF 92-501 to be passed by a composite with a rating of M1, compared with the need for 250 pphr when aluminium hydroxide is used. Only 20-50 pphr of AP 740 are required in epoxy resins to reach the same low level of smoke density as is produced with polyester laminates. The aviation standard FAR 25.853 can be passed with a loading of 25-35 pphr. A liquid version of the additive is available for circumstances where a powder additive cannot be utilised. Red phosphorus flame-retardants are effective in thermoset resin systems and also elastomers, often combined with ATH, or magnesium hydroxide in elastomers. A wide range of treated red phosphorus in dispersion or concentrate form, offered by Clariant, is easier to handle and safer to transport, compared with powder grades. Such phosphorus additives do not affect the electrical properties of the composite, and they have little impact on the physical properties of the laminates manufactured. Work has been progressing to devise a test method for a European standard for rolling stock, prEN 45545. This task has been much more difficult for railway vehicles than for other areas due to the large discrepancies between the various national standards. The operators of public transport in the UK enforce the strictest requirements across Europe. German specifications are lax in comparison. French requirements cover both fire and smoke development. Harmonised fire regulations are needed as the railway system accommodates more and more transnational high speed trains such as the ‘Thalys’ that runs between Cologne, Brussels and Paris. The focus of fire prevention is passenger safety and so special attention is attached to smoke development and its toxicity. Modern GRP systems offer solutions based on both coated ATH and polyphosphate additions to meet the varying requirements of the different standards. Intricately shaped interior trim on the SBahn suburban railway in Berlin features flame retarded SMC materials. 7.3 Electrical Components All materials employed in electronic equipment operating under electrical load have to be flame retardant. Traditional printed circuit boards utilise epoxy resins retarded by reacting TBBA into the liquid resins before laminate construction (FR4). To comply with UL94 V-0 specification, the resins contain about 20% of bromine. In case of fire or smouldering, brominated epoxies evolve corrosive decomposition products that can damage the surrounding electronic equipment. This can be avoided by use of phosphorus flame retardants. It has been found that the addition of finely divided red phosphorus can result in the required flame retardancy with no effect on the thermal and electrical properties of the laminates. As with other sectors, an increasing number of OEMs in the electrical world will insist on halogenfree systems for their products. This extends to the printed circuit boards (PCBs) used to make them. Even the phosphorus systems mentioned above are likely to come under scrutiny as well. The thermal stability of FR4 brominated resins is poorer than non-brominated (G10), although it has been improved over the years. Limitations of FR4 can be overcome by using a G10 resin with ATH and the effect of heat ageing this combination provides a V-0 performance. Once subjected to a fire, all the various options that contain phosphorus or nitrogen can generate toxic species such as cyanides, phosphorous acids etc., but carbon monoxide and dioxide are the most lethal gases, and tend to be present in far larger quantities once a fire has taken hold.

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The TBBA in an epoxy system can be replaced by phosphorus compounds that are built into the backbone of the resin. Unfortunately it is very difficult to obtain the same laminate characteristics by this approach, hence the addition approach of red phosphorus. It is known that with halogenated systems the higher the laminate glass transition temperature (Tg) the lower the halogen content required to achieve V-0 performance. So to achieve FR properties the resin Tg is increased, making the laminate more difficult to drill and rout. The cost also rises. The advantage of the phosphorus-based system is that its tracking/arcing performance is significantly improved, but other key parameters tend to suffer. The water absorption is high and likely to cause problems with plated-through holes that may trap moisture and so cause blistering when later heated, either during soldering or in service. Epoxy systems incorporating ATH show an endothermic reaction and this is important in absorbing heat produced in a fire and matches well with the decomposition of the TBBA based epoxy. CEM3 laminates made with non-woven as well as woven glass in epoxy plus ATH (but no other FR additives) give V-0 characteristics. Because of the lack of thermal stability of standard ATH, the laminate can blister under certain processing conditions, such as reflow soldering. This problem has been addressed by the development of modified forms of ATH with much improved stability whilst retaining the FR effectiveness. These have been successfully used in CEM3 laminates to produce a material that on combustion gives off mainly CO2 and some NO2, so toxicity is very low. One such thermally stable (TS) material is Martinal TS610 from Martinswerk. This is added at at least 200 pphr to achieve V-0 at 1.6 mm thickness, prior to incorporation into the non-woven glass layer. In woven glass cloth layers it is not possible to incorporate TS610 at these loadings. In CEM3 laminates TS ATH can be combined with phosphorus since in certain instances this can simplify the manufacturing process. Unfortunately this raises the materials cost and can generate the problems described above for P-containing systems. In processing Martinal-containing systems, sedimentation of the filler must not take place and the company recommend a combination of TS610 and TS601 with a suitable resin circulation method to minimise the potential problem. Woven glass FR4 laminates have been available for a long time using standard ATH and lower levels of bromine within the resin system. Above 60 phr of ATH, copper adhesion can be reduced and above 80 phr mechanical properties can be adversely affected. By incorporating TS ATH into the epoxy resin system, the level of phosphorus in the backbone of the resin can be reduced. The use of an ATH filler will also reduce the laminate cost. The addition of Martinal TS 601 to the phosphorus-based resin improves the flammability and allows a lower Tg resin system to be used. Other laminate properties are not affected. CEM3 laminates, incorporating Martinal TS, can be produced with very low potential toxicity. This low toxicity should accelerate the use of this type of material worldwide. FR4 laminates cannot at present incorporate the high levels of Martinal TS to achieve UL94 V-0 rating without other FR materials present. The combination of Martinal (TS601) with phosphorus in the backbone of the resin would appear to be the best compromise currently available. However, resins containing TBBA are very cost-competitive and continue to provide great efficacy of flame retardant protection. Those who call for a halogen-free PCB system often tend to be referring just to the flame retardant package employed, and perhaps forget to check on the halogen status of the complete installed PCB package.

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7.4 Electronics Products Significant changes are taking place in resins selected for moulding of housings and enclosures for electronics products. A survey of the US market has indicators (Table 7.1). A major influence on the choice of material is now being played by downsizing and, more importantly, thin-wall moulding technology, bringing more demanding requirements for properties. The main materials in the computer and business machine sector are ABS, PC/ABS alloys and high impact PS, with some use of PVC and polycarbonate. In consumer electronics, however, HIPS is almost exclusively used, and little change is expected up to 2003. In the business machine sector, monitors are expected to account for nearly 30% of material consumption and, in the consumer sector, stationary TV sets will make up 33%. Table 7.1 Resin demand for electronics housings in the US, 1998-2003 (000 tonnes) Average growth 1998 2003 (%) Computers/business machines 413.1 465.9 2.4 Consumer electronics 325.0 401.8 4.3 Total 738.1 867.7 3.3 Source: Business Communications Co. Inc.

Technologies that will influence the use of materials in the future are (as well as thin-walling) EMI shielding and the changes in flame retardant additives, under pressure from the need to comply with environmental regulations in various countries. Marketing is driven largely by the short product life cycles of computers and business machines, and also tumbling retail prices. Logistical considerations have led to huge volumes of business machines, including computers, being made in Asia, plus a move of US resin production and conversion operations to Mexico. Brominated flame retardants have been one of the cornerstones contributing to the safe and spectacular development of computers, business machines and other electronic apparatus. This market is consuming vast qualities of styrenic copolymers to produce the housings of this equipment. Good standards of flame retardancy have been developed and applied in the US, and to a lesser extent in Europe, and they can be achieved thanks to brominated flame retardants. Recent developments call for styrenic materials with better moulding properties to produce lighter, thinner and more complex parts with good impact properties. In some cases UV and light stability is also requested. New flame retardants are now on offer to address these needs. They have been developed by their suppliers from chemistry that is not based on that of diphenyl ethers, and so offer an alternative solution to those sectors of the market that are reluctant to use deca- and octobromodiphenyl ether. The surge in new electronic products led by small computer-based devices has resulted in significant changes in resin choices for enclosures. Downsizing and more importantly, the rush to thin-wall constructions have led to a change in resin selection for enclosures. The computer and business machine sector uses very few resins of consequence. ABS, PC/ABS and HIPS followed by those of much less importance such as PVC and polycarbonate. On the other hand the consumer product enclosure market is exclusively made up of HIPS with little change foreseen over the immediate future.

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The computer/business sector enclosures should grow at 2.4% annually, with monitors taking almost 30% of total resin consumption. The total in 1998 was 188,000 tonnes. Growth on the consumer side is expected to be over 4%, from 138,000 tonnes to reach 182,000 tonnes in 2003. Stationary TVs will account for 33% of total resin, with audio/video and CDs taking a further 35%. In resin competition, PC/ABS will erode a significant portion of ABS’s share, while HIPS will hold its own along with PVC. Polycarbonates are expected to increase greatly, yet remain a minor resin in this market. HIPS competes directly with ABS but not with PC/ABS. Moves to restrict the use of halogenated flame retardants are starting to have a dramatic impact on the way in which plastics are used in electronic equipment and the ability of electronic manufacturers to provide the consumer with higher levels of fire safety. Certain plastics may no longer be able to be used and, more importantly, the high levels of fire safety (such as UL94 5V and above) may no longer be readily achieved without additional material cost. The move to recover ever-increasing volumes of end-of-life equipment is certainly a challenge to the electronic equipment industry and all those in its upstream supply chain. Various labelling schemes operating in Europe that ‘confirm’ the absence of brominated FRs from the products so marked include an EC one, Germany’s Blue Angel plus the TCO and White Swan systems in Scandinavia. In addition, a draft of the proposed EC Directive on waste electrical and electronic equipment would ban some brominated compounds from 2004 (written in 1999). These are polybrominated biphenyls and polybrominated diphenyl ethers. The directive would also require all halogenated flame retardants to be removed from components in any waste equipment that is separately collected. As a result some computer manufacturers, such as Hewlett-Packard, have shifted to phosphorusbased FRs in housings for computer monitors. Siemens has developed a phosphorus-based alternative to the TBBA used in the epoxy resin laminates that are the basis of all circuit boards. Electronics giant NEC of Japan has entered the fray with a polycarbonate containing a silicone FR. The company has licensed Sumitomo Dow to be the manufacturers of this special polycarbonate. Sold as NuCycle, the new material is used to make NEC’s liquid crystal display monitors and battery packs for portable computers. It is also applied for other polycarbonate applications, covering projectors and plasma flat screens. NEC has a target to stop using halogenated FRs by 2011 and has been shifting, generally, to phosphorus compounds. For all branches of E&E products, the call now is for flame retardant systems that do not rely on halogens or phosphorus and the leading suppliers are all steadily improving their additives; despite the considerable argument about the merits of different materials; not to mention the scientific reasoning behind some legislation. For E&E products in general, however, the real pressure is foreshadowed in the European WEEE recycling legislation. Annex III of the draft requires that any plastics parts containing halogenated flame retardants must be separated before recycling, so imposing additional costs, and militates against the use of bromine-containing compounds. This flies in the face of preliminary conclusions under the EU’s own risk assessment programme that indicate that there is no need for risk reduction from the two types, decabromo diphenylether

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(decaBDE) and octobromo diphenylether (octoBDE), mainly used in electrical and electronics equipment. It also appears to be at odds with other studies on the effectiveness of these flame retardants and recycling them. Fundamentally, there is also a growing feeling that the fairest way of assessing flame retardants (and other additives) is a complete life-cycle assessment (LCA) on their environmental impact. The proposal has been attacked from several sides, not least the German Environment Ministry, whose Deputy Director-General has been quoted as believing that there is no need for binding recycling targets, and opposes substance bans such as those proposed for lead or the PBDE and PBB flame retardants. In addition both the German Environment and Economic Affairs Ministries were concerned at the excessively prescriptive and restrictive system being proposed for E&E waste by the EC’s Environment Directorate-General. German studies have shown that polystyrene compounds flame retarded with decaBDE, as widely used for housings, meet the stringent requirements of the German Chemicals Banning Ordinance. They also indicated that no detectable amounts of brominated dioxins/furans were formed during recycling. There was no debromination of the additive and exposure of workers to dioxins/furans was below German workplace limits by some two orders of magnitude. Fears have also been expressed that the material bans contained in the draft WEEE Directive would infringe international trade agreements. Practical confirmation of the effectiveness of brominated flame retardants also comes from recent Japanese work, by copiers makers Ricoh and Fuji-Xerox. Setting up a practical recycling loop for moulded copier components, and comparing recycling of an ABS compound flame retarded with a brominated epoxy oligomer with that of eight other compounds retarded with organic phosphate esters, it found that the recycled brominated ABS met the highest levels of fire safety, as represented by the classification UL5V, which is the test with which most manufacturers of office copiers comply. As a result, Japanese manufacturers of copiers are now specifying that new lines must have 25-30% content of recycled material, containing brominated flame retardants. Another source of confirmation of the overall benefits of flame retardants in general and of the brominated species in particular is a LCA study from Sweden. This concludes that from an environmental viewpoint there is little basis for a general prohibition on all halogenated flame retardants. Looking specifically at the bromines, the environmental consultancy that conducted the work, Orango AB, concludes that there are some 70 different types used in industry, with very different properties. Bromine is a natural substance and is not an environmental toxin, it is even used in cough medicine, but in some individual cases bromine may be included in synthetic molecules that are stable and bioaccumulate, so giving at some point negative effects on health or the environment. Because fires themselves are a major source of polycyclic aromatic hydrocarbons (PAHs), a class of carcinogenic substance found in combustion smoke together with dibenzodioxins and furans, the use of flame retardant additives significantly decreases environmental emissions of this type. The Swedish study compared US and European TV sets and showed that those manufactured to the European standard gave off far higher emissions of PAHs. US sets, containing brominated flame retardants, produced fewer emissions to the environment. US makers must produce sets to meet the V-0 standard of the UL94 fire test but, in Europe, the moulded plastic enclosure of a TV set needs only to pass a Horizontal Burn (HB) test. The US manufacturers use the brominated flame retardant decaBDE to meet their specification, but in Europe manufacturers have removed all flame retardants from their enclosures. The final statement from the Swedish study concludes, ‘In the case of key emission species (polycyclic aromatic hydrocarbons, and dibenzodioxins and furans), there is a markedly higher

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total emission over the whole life cycle from the non flame-retarded TV than from the flameretarded TV’. The BSEF concurs that the concept of producer responsibility for collection and recycling of equipment is agreed by the industry sectors affected by WEEE, but it will be difficult to achieve the proposed targets. Moreover, if certain brominated compounds are one of the best solutions for recycling (as found by the Japanese), the EC, with its mandatory separation of all plastics containing halogenated species, is requiring the industry to perform a difficult task and trying to pull in two directions simultaneously.

7.4.1 Telecommunications Fire safety for plastics in telecommunications depends on the type of components under consideration, and their location, as much as the specific polymer material from which they are made. The products vary from small consumer items to high voltage cables. Therefore, the safety requirements for a range of applications must be set quite differently, although the expected lifetime conditions for a component may not always be clearly known or forecast. In the case of small switches or connectors, the key parameter is ignitibility. If a loose connection causes increased thermal exposure to the plastic of a component, then the problems will be minimised if ignition to flame can be prevented. At present the plastics utilised are often characterised by their performance in tests with small impinging flames, but we may ask what may be such a small flame source in a real-life scenario? The next step in achieving safety would be to limit the potential of fire spread from the ignited component to the surroundings. This may be controlled through the burning characteristic such as heat release rate or formation of flaming polymer droplets, but equally the manufacturer may design those surroundings in such a way that small flames would not cause any harm. The fire safety of equipment enclosed in cabinets could be controlled by consideration of the components and cables inside or by designing the cabinet in an appropriate way. In some cases active measures like detectors or water mist systems might be included. Often the fire behaviour of cables is considered the main factor in a telecommunications system. In addition to the cables themselves, the performance resulting from any passage through walls must be considered. Sealing of power cables as they enter a building is usually carried out, but there is often little control of the open holes created when installing cables within a building. One issue when rating cables is what to take as the scaling denominator? Test rigs with equal areas or equal numbers of cables have been used when comparing the behaviour of different products. All data generated should be freely available for fire safety engineers to use when assessing the potential consequences of fire in a cable bundle. It is unfortunate that old cable runs, with possibly poorer fire behaviour, may be left in conduits and so perhaps nullify the benefit achieved by employing new improved modern cables. It is common now to set higher requirements for products intended to perform under higher temperatures under normal use than in the past. Current trends are for ever more control over fire safety of products due, in part, to the globalisation of trade and the increased desire to adopt more rational performance-related standards for products rather than piece-meal consideration of the elements in a component or system. In Europe, some telecomm products such as cables will be considered as construction products and so subject to the Construction Products Directive (89/106/EEC of 21/12/98). However,

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implementation after many years is still not settled, due to the wait for harmonised tests and standards to invoke them. A key issue is the development and resolution of the so-called Single Burning Item test. Other European projects are covering the general testing of cables, FIPEC; and one for advanced methods for the determination of fire effluent composition. One aspect of a, reasonable, common market is the acceptance of test results from one laboratory everywhere in the market area. On the other hand it appears that the rules governing the test and certification procedures will become more stringent in order to guarantee the acceptance of the results. It would not, therefore, be a surprise if the cost of a single series of tests and related product certification increased so causing potential problems for manufacturers in small markets, albeit great benefits for companies in international markets.

7.4.2 Consumer, Brown Goods Studies in the US in the past, mainly through the auspices of the National Institute of Standards & Technology (and its predecessor, National Bureau of Standards), have shown that the overall costs, in terms of damage, health and environmental considerations, of non-flame retarded TV cabinets, and other consumer items, that are involved in fires is much higher than those associated with a properly formulated and flame retarded material used for the same purposes. Testing by the Swedish national testing and environmental authorities on the same types of products made use of a general life cycle analysis (LCA) model that has been modified to contain the likelihood of fire occurrence and the consequences. Both chlorinated and brominated dioxins are emitted in greater quantities from non-FR TVs with just a Horizontal Burn (HB) rating compared to the TVs containing brominated flame-retardants to a V0 rating level. Polycyclic aromatic hydrocarbons (PAH) are also given off in far greater quantities by the non-FR TVs than the protected ones. It is worth noting that the emission levels of both the brominated and chlorinated dioxin equivalents from both the FR and non-FR TV life-cycles are low compared to other sources. Figures indicate that such emissions from one million TVs during their 10-year life-cycle is at most around 10 mg, or 1 mg/year. In the Netherlands, the annual emissions of dioxins from all known sources are just short of 1,000 g. If we take a figure of 11 million TV sets in that country this would equate to a total dioxin emission from TVs of roughly 11 mg/year or only 0.001% of the overall national total emissions. It should be noted that the production of PAH is many times higher than the production of all types of dioxins and furans. It would be reasonable to conclude that PAH emissions represent a much greater risk to health and the environment than the dioxin-equivalent emissions. In addition, at least 16 people die each year in Europe, based on UK and European statistics. These are known to be conservative due to the cautious estimate of the frequency of TV fires, based on the HB rated sets in Europe. It is conjectured that there may be up to 10 times this number. In the US, however, there is no record of any deaths from fires related to the V0 rated sets in that country. Thus, the risk to human life must not be ignored in any overall assessment of the risk from flame retardant additives. This has been confirmed by work in Germany by the Fire & Environmental Protection Service. The occurrence of TV fires in the US is more than an order of magnitude lower than in Europe (13 compared to 265 fires per million TVs). This dramatic difference provides compelling evidence

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that the higher fire safety classification of enclosure materials typically used in the manufacture of TV sets sold in the USA does have a significant and beneficial effect on fire safety. After dropping for several years, the number of TV set fires in Europe has stopped decreasing, and in countries such as the UK, Sweden and the Netherlands where detailed statistics are kept there is direct evidence that the figures are rising. The European CE mark requires compliance to the local equivalent of IEC65, which allows HB classified materials for enclosures. HB materials are much more easily ignited than those with the stringent V0 classification, and are therefore much more susceptible to fires resulting from design errors, manufacturing defects, misuse, external causes or the effect of ageing and general deterioration. Enclosures made from HB materials may not provide enough protection to consumers, especially children and the elderly, or to their property. Other countries such as the USA or Japan require higher safety ratings than Europe. The technology to achieve that higher fire safety has been a normal commercial practice for many years. Implicit in the studies on fire statistics and the LCA from Sweden, a return to the use of materials with high levels of fire safety may be necessary to provide adequate protection to European consumers. It is in the interests of society, due to loss of life and property, to take measures to lower the incidence of fire by analysing and acting upon the elements that contribute to fire safety, i.e., materials fire performance, design and consumer education. So, making materials less fire-safe is obviously not a move in the right direction. 7.5 Electrical Cables Cables used in mining, railways, shipbuilding and heavy industrial equipment have to be resistant to fire, oils, abrasion and other hazards, yet remain flexible across a wide temperature range from sub-zero to tropical and desert conditions. 25 years ago, this property spectrum could only be met by materials based on chlorinated rubbers such as chloroprene and Hypalon, which on the whole served their purpose well. However, by the end of the 70s, it was recognised by various cable users, especially the Ministry of Defence (MoD) and the London Underground (LUL) that should cables covered with these materials become involved in a fire, sufficiently strong that they themselves combusted then there was a potential hazard. The combustion products generate much black smoke and acidic gases. The former prevents evacuation by obscuring visibility and the latter is an irritant and corrosive agent. These conditions become particularly hazardous in areas of restricted access and exit such as underground rail systems and military vehicles. Other problem areas are those of high population density and those containing capital-intensive plant and machinery. The smoke evolved by chlorinated compounds is a consequence of the chemical structure of the polymeric material and compounding ingredients. Acidic gases result from dehydrochlorination of the polymer. BICC began R&D for the MoD and LUL to develop halogen-free materials that would, nevertheless, have the properties of inherent flame retardancy, fluid resistance and flexibility at both high and low temperatures, yet have much reduced smoke and gas emissions. The programme gained ever more urgency after the Falklands conflict of 1982 and the King’s Cross fire of 1988. At that time the choice was limited to EP rubbers, EVA, ethylene methyl acrylate (EMA), and nitrile formulations. None of these polymers are inherently flame retardant and only NBR

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possesses an adequate level of fluid resistance. Early work was centred on this group of materials, either alone or in blends with each other or with plastics such as the polyester or polyamide thermoplastic elastomers. The early offerings were EVA or EMA polymer systems plus large amounts of hydrated fillers. These materials had poor processibility and had a poor level of physical and mechanical properties. The materials have evolved since the 1980s as new polymers and additives have come on the market. Now, halogen-free compounds are available that have equivalent flame retardancy and fluid resistance to the old chlorinated traditional materials, plus low smoke and acid gas properties. High performance grades fully meet the Naval Engineering Standard NES 518, now known as DEF Stan 61-12 (Part 31) and represent the ultimate in fluid resistant, flame resistant, halogen-free rubber technology. Today, BICC Compounds offers a wide array of halogen-free elastomers as solutions for applications not only in shipbuilding, but construction, petrochemical, railway and automotive engineering. In addition to their fire performance, halogen-free materials now also offer environmental and life expectancy advantages over traditional materials. They do not contain any heavy metals, nor plasticisers or sulfur-based vulcanising agents; and can now be predicted to last for around five times longer than traditional chlorinated elastomers under the same conditions. Teknor Apex has various halogen-free insulation and jacketing compounds which provide characteristics to allow communications and data cables, for both copper and fibre optic, to meet European, IEC, requirements for minimal smoke toxicity. The Fireguard LSZH series offer good productivity for cable extrusion, due to low die ‘drool’. The 1000 series grades, with Shore D hardness from 43 to 56, give LOI levels from 35 to 53%. There are five 2000 grades with hardnesses from 38 to 53 and LOI from 35 to 52%. In IEC 332-3C tests, cables with jackets and buffers made from LSZH compound exhibit maximum char lengths of no more than 89 cm; the permissible maximum is 250 cm. European regulations governing cable sheathing flammability are slowly moving closer to the tougher regulations now operating in the US. The European standard for plenum wiring, IEC 3323C, is about as demanding as the US standard for risers, UL 1666. The US plenum wiring standard, UL910, is much tougher. A new European requirement, closer to UL 910 is believed ‘imminent’. In simulated fire situations, while wiring meeting UL910 hardly burns at all, wiring meeting the IEC requirements burns extremely quickly, creating extremely high temperatures that lead to flashovers. Zero-halogen cable takes longer to burn than halogenated cable, but once ignited, it spreads more rapidly. Another company making moves in this field is MA Hanna, the US-based compounder now part of PolyOne. Cable compounds became their first market-oriented product group, following an expansion of their German-based unit Melos Carl Bösch in Melle. This increased production of ECCOH brand of low smoke and zero halogen (LSOH) compounds was first made at Enviro Cable Compounds based in Oslo, Norway, another subsidiary. The company is possibly the leader in wire and cable compounds, after the in-house compounding of the cable makers themselves. The LSOH materials, based on polyolefins, are designed to reduce risks of black corrosive smoke from cable fires and are aimed at low- and medium-voltage uses. While the material is at least twice the cost of PVC, it is not a major factor in total cable costs, depending on the type and size of cable. On a big cable, the jacket will only be around 3% of the total cost, rising for a small cable to 20%. Market growth was seen as 10% pa with demand around 60-70 ktpa. The total demand for PVC cable compounds is around 1000 ktpa, of which special flame retardant types take 20%. BICC Compounds, a subsidiary of BICC Cables part of General Cable, have been at the forefront of low smoke and fume technology. One area has been low smoke and zero halogen compounds to meet the new Harmonisation Document for the insulation of single core unsheathed electrical

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cables. These types are designed for low-voltage point-to-point wiring between machinery and light sources in factories, where they directly replace the PVC-based 6491X cable range. Such cables are usually installed in areas where there are large numbers of people present, particularly where there are restricted means of escape. European Harmonisation document HD 22.9, from CENELEC, is specified in British Standard BS7211 and calls for low smoke, zero halogen materials that maintain the levels of flame retardancy, cost and processing speed experienced with PVC, while reducing the potential risk of combustion products. BICC has developed a range of crosslinkable compounds for this demanding application, which are suitable for different manufacturing routes. Large amounts of hydrated mineral fillers are employed in new polymers that permit high loadings, plus additional chemical additives that stabilise the fillers in the polymer matrices and improve the characteristics of ageing and processibility. The ability to crosslink the compounds gives improved physical properties, better chemical resistance and shape retention at temperatures significantly above the melting point of the polymer resin itself. This prolongs the life of the compound and its integrity in the event of a fire. One of three methods can be utilised in the cable industry: peroxide, silane (either Monosil or Sioplas techniques) and electron beam; each requiring a different compound to achieve the right properties. Each has positive points and drawbacks. For peroxide crosslinking, the compound has been selected to maximise the speed of the line by providing maximum scorch safety time during extrusion, while giving maximum residence time in the continuous vulcanisation tube. The version for silane processing has been formulated to minimise silane dosages and avoid side reactions with the curing system, while the compound for electron beam curing contains special promoters to maximise crosslink density. Cable racks fall into three overall categories; ladders, open trays and closed trays. Their influence on fire performance is considerable and can be measured in a version of the 3 m cube room smoke test under IEC 61034. Unexpectedly, a closed tray does not afford complete fire protection since a chimney effect can cause rapid fire propagation along the length of the sample. Belgian cable company Kabelwerk Eupen has introduced a commercial application for polymerclay composites to make flame retardant cables. EVA-based cable jackets are combined with the clay materials in what is called a ‘one-pot synthesis’ extrusion technique. 5% of the nanoclay improves the fire performance of the EVA compound by promoting char formation and delaying degradation. In addition, it prevents dripping of any burning polymer material. The maker of the nanoclay is Süd-Chemie, who believe that the nanocomposites could be used as an alternative to PVC coatings and resins containing brominated FRs. Kabelwerk Eupen have explored combining nanocomposites with other FRs. These include ATH in EVA. The two companies have applied for a patent for this technology and claim that less ATH is needed in a nanocomposite than in a standard compound, thereby leading to increased extrusion speeds and improved elasticity. To achieve typical flame retardancy for cables required by the most important international cable fire test (IEC 60332-3-24, Tests on electrical cables under fire conditions – Part 3-24: Test for vertical flame spread of vertically-mounted bunched wires or cables) demands a high loading of a mineral FR filler such as ATH. 65wt% of ATH with 35% of a suitable polymer like EVA must often be used for cable jackets. A similar compound of EVA (with 28% VA content) with ATH and 5% of a nanocomposite can pass the same test. It was found that the ATH could be reduced to only 45% of the composition. The reduction in the total amount of the fillers results in improved mechanical and rheological properties of typical EVA-based cable compounds. The char formed is

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very rigid with only very few small cracks and is believed to be the cause of a much reduced peak rate of heat release when combusted. A range of halogen-free low smoke compounds for cable insulation and sheathing are available from AEI Compounds Ltd., in Gravesend, England. These come under the Catapyrric trade name. Some, such as SX545:CM540U are silane crosslinkable; whereas others are moisture curable or entirely thermoplastic. 7.6 Building and Construction The introduction of flammable pentane as a blowing agent to replace HFCs and other potentially ozone-depleting fluorocarbons in the manufacture of foam panels has brought with it the additional factor of fire resistance. The fire behaviour of pentane is such that in PU formulations, it is necessary for the pentane and water components to be precisely coordinated with as little pentane as possible. In spite of this, high quantities of flame retardant are required to pass the tests set in DIN 4102-B2. This creates a more costly polyol component. By contrast, PIR formulations display different behaviour in fire tests. Since the isocyanurate groups give the foam excellent flame retardant properties, PIR foams fulfil the fire tests with much reduced levels of non-halogen flame retardants. In addition, higher quantities of pentane may be utilised without impairing the FR properties of the foam to any great extent. Elastogran has developed pentane blown polyisocyanurate formulations with a much-reduced content of halogen-free flame retardants. The company has developed new polyester polyols for the package that contain isocyanurate. The new PIR systems also offer far better dimensional stability for the resultant insulation panels. Panels with paper or aluminium outer layers have been continuously produced in thicknesses from 20 mm to 140 mm. They are primarily used as roof insulation in the form of dimensionally stable panels with flexible outer layers. Another material that has become more widely recognised for its fire safety as an insulation medium in construction is phenolic foam. Most products from the wide choice available today provide good fire resistance and meet various relevant standards, either inherently or with the use of flame retardants and facing materials. However, a significant difference arises with regard to the level of smoke emissions. A surprising point is that Building Regulations do not set limits on smoke emission by construction materials and components under fire conditions; even though it is well accepted that smoke is often a serious hazard and may well be more life-threatening than the fire itself. Such safety considerations have led to an increase in the number of specifiers requiring phenolic foam insulation. Although this is a cellular plastic, it has good fire performance, exhibits low flame spread, extremely low smoke emission and is a very efficient thermal insulant. The densely crosslinked structure of phenolic foam has an inherently low capability of smoke generation, which is a result of the polymer being essentially a char forming material when heated to ignition temperature. The char has a high carbon content that acts as good thermal insulation; it burns slowly, without flaming or melting, and so avoids substantial coalescence of low molecular weight organic species, which are known to be smoke producing. Phenolic foam is unusual in that it combines the good thermal performance, moisture resistance and structural strength of cellular materials with the fire performance of inorganic and fibrous materials. The versatility of phenolic foam makes it ideal for a whole range of applications, from

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traditional heating and ventilation uses, structural applications such as roofing, cavity board, floors and the like to composites panels for use in the food processing industry. Awareness of phenolic foam is increasing all the time through such activities as the testing protocols under the Euro-classification system and the European Phenolic Foam Association, that highlight the excellent fire performance and low smoke and gas emissions of phenolic based products. New preparation techniques in the 1980s have given rise to extensive usage of phenolic foams for pipe and ducting insulation and to wider application in the flexible-face laminate market for building insulation. Such foams meet the requirements of most major fire tests relevant to the construction industry, entirely unaided, while other organic insulants require the addition of flame retardants or facings such as steel, aluminium or plasterboard. An example is Kooltherm pipe and duct insulation from Kingspan Industrial Insulation that achieves Class 0 rating as defined in the UK Building Regulations. This is a combination of BS476: Part 6 for Fire propagation and Class1 Spread of Flame according to BS476: Part 7. These tests demonstrate the excellent generic fire performance of phenolic materials without the aid of additives or protective facings. The Nord Test NT 036 is a full-scale test used by insurance authorities, where the ceiling of a room is lined with 24 x 3.6 m lengths of insulated pipework. A 150kW burner is used and flame spread, smoke and toxic gas emission are assessed. Phenolic foam gives negligible flame spread or smoke and the quantities of CO and CO2 generated during the 15-minute test are small and toxicologically insignificant. Also, under BS5111 the Kooltherm products register a smoke obscuration figure of less than 5%, the same as mineral wool. Phenolic foam pipe insulation has also been tested and approved by Factory Mutual for use as pipe insulation, based on its low spread of flame. A single European standard has been proposed for the construction industry based on a new test currently called the Single Burning Item test, designated prEN SBI. In this, the reaction of materials to fire is divided into ‘Euro-classes’ (prEN 13501-1), see Chapter 8. Flame retarded SMC parts have excellent resistance to fire in the SBI test. It is so good that it achieved the highest classification for organic materials and the best smoke status. The SBI test will succeed the following national standards, among others, in the construction industry: • • •

DIN 4102; Epiradiateur NF-P-52-501/ NF-F-16101/2; BS 476 Parts 6 & 7.

Unlike DIN 4102, in which some melting test specimens are rated as superior to non-melting materials but exhibit totally different behaviour in a real fire, the SBI test offers the possibility of testing the materials under more realistic fire conditions. Because of this anomaly in DIN 4102, flame resistant thermoset materials are often rated as being poorer performers than they actually are, especially in Germany. The SBI test is much more realistic in this regard and does not disadvantage or advantage any material on account of its ‘ peculiarities’. Highly filled formulations, with ATH, subjected to the SBI test gave rise to the results shown in Table 7.2. The tests conducted by Michael Sommer (BYK-Chemie GmbH) on SMC panels reveal

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that the material passes all test specifications of the pertinent methods and can be modified to meet all needs where necessary. Depending on section thickness, ATH content can be adjusted to allow a component to achieve the appropriate specifications. Table 7.2 Comparison of ATH-filled SMC compounds, and other materials, in the SBI test FIGRA THR SMOGRA Material tested (W/s) (MJ) (m2/s) Fire class B, smoke class S1 <120 <7.5 <30 UP, SMC, halogen-free FR B B S1 Fire class B, smoke class S2 <120 <7.5 <180 PVC, FR B B S2 Fire class C, Smoke class S1 <250 <7.5 <30 PF, phenolic foam C B S1 <180 >7.5 <750 Fire class D, smoke class S2 S2 D D PP, pipes of 40 mm and 110 mm diameter S2 D D PVC, cables with PVC jackets >180 >7.5 >750 Fire class E or F, smoke class S3 S3 E/F E/F PC, FR, 3-coats S3 E/F E/F PS, FR S3 E/F E/F PU, FR foam FIGRA = Fire Growth Rate; THR = Total Heat Release; SMOGRA = Smoke Growth Rate Source: Michael Sommer, BYK-Chemie GmbH, reproduced with permission.

Products for outdoor use such as wall cladding, can be press moulded in many variants from SMC or BMC. Pultruded profiles can also achieve B1 fire status if a resin such as DCPD or unsaturated polyester/MMA is used with up to 250 phr of ATH as part of the additive package. The classification of flame resistant GRP systems in the SBI test will be a great boost for the materials enabling them to satisfy the fire protection rules of the future. 7.7 Upholstered Furniture and Textiles The application of natural fibre based fabrics has increased in the furniture industry during recent times after many years of decline, as synthetic materials were the favoured textiles and fillings. A reappraisal of the fire properties of various materials in their proper context for coverings, barrier layers and fillings has hastened this trend. There is now the possibility of natural fibres having an increased resistance to ignition even in the absence of flame retardants. Cover fabrics, such as wool, cotton, flax, viscose and their blends, are often impregnated with proprietary flame retardant systems such as Pyrowatex and Proban, which demonstrate fastness on washing or cleaning. Wool has the advantage of a natural capacity to form intumescent carbonaceous char with excellent thermoinsulating properties. Wool/cotton or wool/flax at 50/50 blends are most efficacious. Flax has the added property of protecting against moth infestation and also prevents static build-up. Such blends pass the small ignition source test, e.g., the equivalent of a lighted match, no ignition during a 20 second application, with the exposed fabric converted into a char with no exposure of the underlying PU foam substrate. Another way to protect the inner, support component of upholstery is the use of barrier materials in the form of non-flammable interlayers placed between a covering fabric and the filling material. Woven and non-woven fabrics as well as felt made from natural fibres (e.g., cotton, flax and hemp) and their blends with flame retarded synthetic fibres, can be used.

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The Institute of Natural Fibres in Poznan, Poland has developed new barrier fabrics, both woven and non-woven. The first was a cotton weave containing a small addition of polyester. The latter was made of flame retardant flax and hemp fibres. The flame retardant and its application method were developed by the institute. The flame retardant, called FOBOS M2T, was based on urea polyborates and the sodium salt of alkyl-aryl sulfonic acid. The method of impregnation is cheap and simple. It can be carried out on typical finishing equipment and increase manufacturing costs by only 10-15%. The use of a non-flammable barrier fabric has been shown not only to increase time to ignition but also to reduce the maximum heat release rate. Various non-woven systems were found to offer good fire prevention properties with differing fillings and the same linen/polyester covering, but the best combination in a range of cone calorimetry tests was an impregnated flax/hemp non-woven. This gave good times to ignition with all fillings, but the lowest figures for heat release, both in total and for maximum and average rates of release was given with a PU foam filling. The various projects at the institute reveal that natural barrier material treated with flame retardants are an effective method for reducing flammability of upholstery systems. Barriers made from FR treated nonwovens are much more effective than barriers made of difficult-to-ignite fabrics. The move in the US to introduce regulations for the flammability of furniture fabrics has spurred activity in the segment. The US Consumer Product Safety Commission (CPSC) has found that the outer cover fabric is the primary determinant of the initial growth of small open flame-ignited furniture fires. Injuries caused by these fires are principally those of children playing with lighters and matches. A study for the CPSC examined 16 flame retardant compounds and found eight immediately of ‘minimal risk’. The main three compounds already used in the UK for fabric protection appear to be on the ‘accepted’ list for the US standard. For cotton-based fabrics the major candidate is phosphonic acid (3-[hydroxymethyl]amino)-3-oxypropyl dimethyl ester, sold as Pyrovatex. It is already used for apparel and does not meet the definition of ‘toxic’ under the Federal Hazardous Substances Act (FHSA). For synthetic fabrics, decaBDE and hexabromocyclododecane are the main candidates. Since these compounds have large molecules they cannot be easily absorbed, although they require, typically a synergist, usually antimony trioxide. The latter, however, has increasingly fallen under suspicion as a possible carcinogen or at the very least an undesirable product to inhale as dust. Zinc borate has continued to attract attention as a proven substitute, and is another not ‘toxic’ substance under the FHSA. Meanwhile there is a fourth candidate, used for many decades in certain flame-resistant cotton apparel fabrics. This is tetrakis hydroxymethyl phosphonium salts (THPS), with trade names such as Proban.

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8 Fire Testing 8.1 Introduction Depending on the particular polymer under consideration, the product type into which the polymer is incorporated and the specific end-use application, many different fire retardant methods can be used. The aim of all these modifications of a polymer product is to improve its fire performance to pass the specified fire test(s) for the application concerned. There are several ways to change the fire behaviour of a polymeric material especially at the different phases of combustion. However, there is no single best way to improve the fire behaviour of a certain polymer/polymer product because the needed performance depends on the requirements in the intended end-use. Hence, the same product may need to be optimised in two or more ways if it is to be used in different applications. End-use applications of products can be grouped in many different ways depending on the purpose. For fire safety, the essential points to bear in mind are regulatory requirements, and within those the detailed end-use applications including exposure conditions, etc. Clearly identified application areas are electrical and electronic equipment, textiles, furniture, cars, trains, ships, aeroplanes and construction products. Within these groups the end-uses may vary considerably. The conditions of the application, such as temperature, humidity, light exposure, etc., not only define the needs for material properties but also reflect on the required fire performance. One example is fire-retarded wood boards that can be used both indoors in reasonably stable conditions and outside under varying exposures. In addition, specific applications in railways and a marine environment demand different types and levels of performance. The assessment of hazard in real fire situations requires the coupling of material and fire properties with fire dynamics, and thus cannot be based only on small-scale laboratory tests measuring one or a few parameters. Essential factors affecting the fire performance under real fire conditions cover the following: •

Material properties, such as thickness, density, heat absorption, heat capacity and strength as a function of temperature;

•

Fire properties, such as heat release as a function of time, smoke and gas emission and charring rate; and

•

Fire dynamics with properties such as vertical and horizontal flows.

The main features of real fire performance are the target for simulation or description in classification tests that usually are small or intermediate scale in size. Even smaller scale and very simple methods can be used in product development for cases where classifications tests have been performed that are representative of the product family and type of concern. These tests may be very helpful if the parameter(s) measured are relevant to the larger scale classification test and if a proper correlation can or has been established between the two scales. Key parameters to estimate fire behaviour of fire-retardant products, or indeed any product, are the classic stages of ignitability, flame spread, heat release, smoke production, toxic or corrosive gas emission; plus charring rate and mechanical properties (retention thereof) at elevated temperatures. 8.2 Specific Tests Fire testing is a very complicated subject. To start with, fire performance is dictated by requirements imposed by various, differing, bodies, such as:

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• • •

Governments in order to protect lives and property; Insurance companies with a financial interest in minimising losses; and Fire brigades wishing to minimise fire-fighting hazards.

In Europe, each country has its own fire test systems and requirements. North America also has several different large- and small-scale tests. However, one fact remains certain: no single test, whether large or small, can be used to predict the performance of materials under actual fire conditions. Very simply, there are too many variables in a real fire that are too complex to be incorporated into a single test. Consequently, the interpretation of any fire test result and individual product material performance is a complex matter. Any test is only an indication of performance under the conditions of that test. No test can simulate real fire conditions. No test can predict the source of ignition, configuration of construction, nor the involvement and potential contribution to the fire of other combustible products. It is generally recognised, however, that large-scale tests are more informative than small-scale tests. They have also been shown to give repeatable results. Results from different large-scale tests correlate closely and therefore give valuable information that may not be learned from small-scale examination of materials or products. In the UK, the late 90s saw strong influences from insurance companies who are demanding their own standards be met before insurance is granted on a building. This work has been largely directed by the Loss Prevention Council (LPC, an insurance industry grouping) and often utilises US-style large-scale tests. The large-scale tests, which are believed to be amongst the best of those available, are the Factory Mutual Class 1 Calorimeter Test, the FM 25-foot Corner Test, and the so-called Mini-corner test. Each offers drawbacks and benefits that need to be carefully evaluated. The FM Calorimeter Test is primarily used for rating various metal deck roof constructions. It is becoming internationally accepted as the most representative acceptance criterion for the roofing and insurance industries. Class 1 can result in lower insurance rates for the whole building. In this test the insulation board is topped with a conventional 3-ply built-up roof and the whole assembly is heated by direct flame impingement from the underside for 30 minutes. Fuelcontribution rates are determined by direct fuel substitution and the time-temperature details are recorded for the assembly. The results are cross-checked with the limits for Class 1 approval. FM claims that in 100 ft x 20 ft (~30 m x 6 m) building tests, composite steel roof deck assemblies with acceptable Class 1 ratings, would not lead to a rapid spread of fire if subjected to an interior fire. The FM Corner Test is for measuring the propensity of materials to flashover or develop selfpropagating flame fronts in a structure designed to simulate a large-unoccupied factory or warehouse. The test enclosure is 25 ft high (8 m) with one wall 50 ft long (over 15 m) and another 38 ft long (10.7 m). The test material is installed on the walls and/or ceiling, with or without sprinkler protection, and is exposed to a fire generated by a 340 kg crib of wood. This crib produces a temperature of up to 1000 °C within 5 minutes. The material passes the test if flames do not exceed the limits of the structure and if other criteria, such as degree of damage to the structure are met. This corner test has gained international acceptance when related to the use of cellular plastic materials in buildings that are 25-30 ft high (7.6–9.1 m), as is typical of commercial and industrial buildings.

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The third widely used test mentioned is the Mini-corner Test. This was especially designed to replicate the behaviour of products in the FM 25-ft test on a smaller scale. It has been successfully used for predicting results of the FM Corner Test (to find the propensity of flashover), except for materials that melt at low temperatures. The main points in favour of the corner test are listed as: •

The ignition crib produces a realistic fire source with temperatures up to 1000 °C. (Compare this with, say, the B2 test in which the ignition source is a Bunsen flame on foam at ambient temperatures in the laboratory.)

•

The test configuration is similar to a room and any interaction of the product under test with other components can be observed.

•

The products under examination are usually full-size panels and so the application and fixing details can be the same as normally used in a construction.

These conditions create an environment in which three practical characteristics can be observed: •

How easily does the product ignite?

•

Does the flame spread lead to fire propagation and, if so, at what speed?

•

Will this propagation lead to flashover and total combustion of the product being tested?

For economic reasons, or for screening purposes, small-scale tests are still often used. For a totally new product type, it is always important to ensure that the small-scale test(s) used are representative (i.e., correlation known and differentiation possible) in relation to large/classification-scale test(s) when choosing test methods for product development purposes. Examples of test methods to measure the key parameters of ignitability, heat release, flame spread plus smoke and gas production are: •

The cone calorimeter (ISO 5660) [Rate of heat release from building products, 1993]

•

Single burning item (SBI) (prEN SBI) [Building products excluding floorings – exposed to thermal attack by a single burning item, 1999]

•

Room/corner test (ISO 9705) [Full scale room test for surface products, 1993]

•

Spread of flame/LIFT (IMO FTP Code, Part 5 and ISO 5658-2) [International Maritime Organisation, Fire Test Procedures, test for surface flammability, 1998 and Lateral surface spread of flame on building products with specimen in vertical configuration, 1995]

•

Fourier transform infrared (FTIR) gas analysis spectroscopy

In most cases the classification criteria for reaction to fire behaviour are based on the assumption that early phase fire development causes the main hazard. This means that the key elements for effective fire retardants are to delay ignition and to reduce heat release and smoke production, at least during the early part of exposure. 8.3 Comparing Test Results The major and enduring problems in fire science and technology are trying to compare results from different test methods and scales of test. The following are some of the points to be borne in mind: 1. The parameters used do not correlate. Examples can be found of attempted correlation in which parameters of a different nature are compared, such as limiting oxygen index value and

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heat release under high irradiance or smoke production in well-ventilated and under-ventilated conditions. 2. Different fire exposure levels. In small-scale tests, the fire exposure may be too unrealistically low to be able to discriminate between different fire behaviours occurring on the larger (real) scale. As an example, the new European SBI test uses a propane burner of 30 kW in a corner. As a second guarding test a 20 mm small flame (prEN ISO 11925-2) is used. This small test can be used only as a screening test to see whether there is not any chance of passing the SBI test. This is seen for a range of wood products in Table 8.1, which shows that the small flame test is not able to differentiate between the different classes of product performance. It is even more difficult to compare small flame test results with those from experiments that generate flash-over from the exposure of a surface panel to severe enough fire conditions. Table 8.1 Comparison between results of SBI and small flame test Product SBI class Small flame class FR particle board _ _ Intumescent coat on particle board _ _ Melamine faced particle board D _ Particle board D _ Birch plywood D _ Medium density fibre board D _ Low density fibre board E _ 3. Different types of exposure. Whether the exposure is radiative or convective/conductive (or various combinations thereof) may cause major errors in the interpretation of comparative results; small flame ignition time data may rank materials differently compared with ignition times under purely radiative conditions. 4. Limitations of applicability. In some tests, the overall behaviour is dependent on the possible spread of fire within the specimen area. An example is the SBI test in which heat release data are quite comparable with cone calorimetry if those from the product tested are such that it will not spread fire much beyond the area of highest exposure behind the flame in the SBI corner. However, this simple correlation is most probably not valid anymore for a product that will spread fire under the SBI method. 5. Behaviour of joints and fixings. In small-scale tests, effects arising from the joints and fixing techniques are not possible to measure and thus intermediate or even full-scale tests are needed to demonstrate those effects. Even though there have been many improvements in the harmonisation of fire testing, there are still many different testing and classification requirements to be defined for a number of products depending on the area of application, such as marine applications where IMO fire testing is one of the few global systems, construction products where Construction Product Directive-related harmonisation is at last to take place in Europe, aircraft, railways, cables, etc. It is the actual geometry of a final product in combination with the energy input of the flame retardant test or fire that determines what the degree of flame retardancy will be. The laws of mass and heat transport dictate that when the geometry changes, mass and heat transfer will change in a strong non-linear way. As a consequence, actual fire behaviour can be vastly different on end products compared to FR tests on small-scale test specimens of the materials out of which these products are made. This poses a dilemma for designing FR materials, as on the one hand one tries to develop new FR compositions using small-scale screening techniques while in reality many products will be

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subjected to flame or fire retardant tests which do not display any appreciable correlation with small-scale tests. Cable manufacturers have used the LOI test as a screening tool in the development of FR materials. Many are moving away from this approach and the general contemporary consensus is that UL94 VB tests offer a better indication of actual large-scale cable test performance, although the correlation is still weak. Recent changes in FR standards concern the large-scale cable flame retardant IEC332-2 test and intermediate tests such as the SBI. These new tests could require reformulation of existing products to obtain a lower rate of heat release, to reduce smoke evolution or to eliminate burning drips. It is likely that such reformulation efforts of FR materials will be screened initially by determining the rate of heat release in a cone calorimeter or in the final product test rather than by FR tests such as LOI or UL94 VB. This discussion does not imply that small-scale tests should be ignored. The importance of having ignition resistant and effective FR materials at low enthalpy input is a significant contribution to fire safety. The ultimate goal of the FR product manufacturer is, of course, to develop flame retardant products that are as safe as possible. This requires a balanced approach to develop materials with the appropriate levels of flame retardancy over a range of practically relevant smallscale and larger scale FR tests. 8.4 Tests for Building Materials The process of harmonisation for the testing of the reaction of building materials to fire has been going for over a decade. The culmination of all the effort over the years has emerged as a panEuropean testing and classification system that divides such materials into classes A1, A2, B, C, D, E and F. The test methods to be followed are: Table 8.2 Harmonisation tests and standards Test Method Standard Non-combustibility Pr EN ISO 1182 Calorific value (PCS) Pr EN ISO 1716 Single burning item (SBI) Pr EN 13823 Small burner test Pr EN ISO 11925-2 Flooring radiant panel Pr EN ISO 9239-1 Classification Pr EN ISO 13501-1

Although some of the test methods are new, most are established techniques with slight modifications. Floor coverings are tested by the radiant panel method, which is already in use in most European countries. The test methods for determining the calorific value and to confirm the nature of noncombustible materials (currently Class A building materials in Germany) are also well established and have been modified only slightly for the European classification system. A class E ranking, that means minimal demands on reaction to fire (e.g., currently class B2 in Germany, denoting ‘normal flammability’), is awarded on the basis of results from the small burner test, which is used in similar form in many European countries, such as Austria, Italy and Germany). For classifying combustible building materials in classes B to D, the single burning item test (SBI) has been produced. It was developed using flat building elements for wall and ceiling linings, then subjected to a round-robin test and finally verified in a ‘room corner test’ (ISO 9705). The specimens, of 1 m x 1.5 m and 1.5 m x 0.5 m, are arranged orthogonally, flat against the walls of

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the room corner with the largest dimension vertical, and exposed to a diffusion flame of 30 kW. The heat release is determined by the oxygen consumption method, where the consumption of oxygen is proportional to the heat released when an organic material burns. An important characteristic is the fire growth rate (FIGRA), which is calculated by dividing the heat released when the product burns by the time at which a specific rate of heat release is reached. It should correlate to the time to flashover in the room corner test. An additional criterion for ranking products in the SBI test is the total heat release (THR) in the first 10 minutes of the test. Also determined are the smoke emission and the presence, or otherwise, of burning drops or particles. Unlike the previous tests that it supersedes, the SBI test involves exposing a relatively large area of the specimen to a flame. The fire scenario in the SBI test also ignores the early stages of the fire and any smouldering that may occur after the burner is removed. This may lead to different, often worse, classifications as regards reaction to fire than was previously the case for any individual material. In particular, melting thermoplastic materials are often classified less favourably in the SBI test because, first, a large amount of melted material may accumulate near the burner and be ignited by the persistent heating, and, second, the poorly reproducible melting gives rise to relatively extensive scatter of the test results. The SBI test also classifies smoke. One criterion employed is the smoke growth rate (SMOGRA). This is the maximum quotient of smoke emission divided by the respective point in time. There is controversy about the relevance of such a value as regards risk posed by smoke emission in the event of a real fire. Owing to the relatively large amount of material that is decomposed in the vicinity of the burner, many plastics end up with an unfavourable classification. By contrast, wooden materials, which only evolve large quantities of smoke when they smoulder, receive a relatively good classification. It is feared that the very existence of a smoke classification in the new Euro system, no matter how inappropriate, may lead legislators to impose demands that were absent from previous building regulations. The SBI test was designed for two-dimensional products and it has still not been established how to adapt or apply such a test for non-planar parts such as pipes, cables and linear seals. Indeed, the cable industry is moving towards total unacceptance of the new system, and is proposing its own system that would feature completely different test methods. It remains to be seen how building products that cannot be tested by the SBI method will eventually be tested, whether in a large-scale room-type test or another scenario; and also how these various tests, under the new European classification system, are incorporated, as they eventually must be, into national building regulations. In the Single Burning Item test, the reaction of materials to fire is divided into ‘Euro-classes’ (prEN 13501-1), see Table 8.3. The SBI test will succeed the following national standards, among others, in the construction industry: • • •

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Table 8.3 Proposed European standards for the construction sector Specification

Applied standard

No contribution to fire

ISO 1182 + ISO 1716 prEN SBI prEN SBI prEN SBI prEN SBI DIN 4102-1 DIN 4102-1

Hardly any contribution to fire Little contribution to fire Acceptable contribution to fire Acceptable reaction to fire No classification for fire

Euroclass A1 A2 B C D E F

DIN 4102 Category A1 A2 B1 B1 B2 B2 B3

Unlike DIN 4102, in which some melting test specimens are rated as superior to non-melting materials but exhibit totally different behaviour in a real fire, the SBI test offers the possibility of testing the materials under more realistic fire conditions. The so-called Euro classification system for fire performance of building products will be in the form of a ‘tool kit’ of criteria, based on a common test procedure, from which individual Member States will be able to select the requirements for their own specific standards. This approach should separate detailed test standards from product classification and result in a reduction of the amount of testing required. Only the SBI test will be needed and is expected to give all the basic data required for the classification system. As a consequence, product standards throughout the EU will refer only to classification standards; and appeals against standards set by any individual country will only be allowed in reference to the classification. An appeals procedure and the use of a large-scale room-corner reference test could be invoked in cases where it can be argued that the SBI test might not give a true reflection of the reaction to fire performance in a given end use. Such appeals can be requested by Member States or industry federations and CEN, the European standards authority. A transition period of some 8 to 10 years will probably pass before the relevant legislation and standards have been adopted in each country. Even then, the individual Member States will be able to set the level of fire performance they require in any particular circumstance, and products will have to meet that level in order to sell for that purpose in that country. 8.5 Cable Testing An EC funded project has been examining the various test methods that are used to evaluate electric cables and their fire performance. This was funded by DG XII of the Commission and is designated as Fire Performance of Electric Cables (FIPEC). Various levels of testing have emerged from the project ranging from a small-scale, cone calorimeter test procedure especially developed for cables and their constituent materials, a full scale procedure based on IEC 60332-3, but utilising heat rate release and smoke production rate (SPR) measurements, and a real scale test for mock cable installations. Companies involved came from the cable manufacturing sector, cable users, material suppliers and research bodies. 8.6 Mattress Tests In the US, the federal government considered rejecting proposals to label PU mattresses with fire hazard information. The Consumer Product Safety Commission was responding to a petition from the Children’s Coalition for Fire Safe Mattresses, but the CPSC wishes to adopt fire standards that

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would consider how an entire mattress behaves in a fire, not just the filling material. It is recommending the development of complete standards for mattress flammability from open-flame ignitions. 8.7 Clothing Tests The protection of clothing, specifically nightwear, is only regulated in the UK and Ireland. Various committees under the Consumer Policy and Health Protection Directorate (DG XXIV) of the European Commission and the European Standards Body (CEN) have in recent years been considering the introduction of a requirement for nationally enforceable specifications under the umbrella of the General Products Safety Directive (92/59/EEC). A feasibility study mandated by the European Commission on CEN was handled by Technical Committee CEN TC248 for Textiles, Subcommittee 1 on burning behaviour. This Study Mandate M/263 of December 1997 found that EN 1103:1995, a standard for the burning behaviour of apparel fabrics should be the basis of a nightwear standard and that further protocols were needed to consider any toxicological and dermatological risks from any treatments used on such fabrics to meet any subsequent standards. The feasibility study identified a set of parameters, which determined the fire resistance of nightwear and these must be taken into account by the proposed standard. The two main parameters were rate of flame spread and flame surface flash. Test methods capable of measuring these parameters must be determined. Factors such as care maintenance, the ageing of nightwear by washing and drying must also be addressed. Any flame retardants employed on the textiles should not be prohibited or be assessed as unacceptable risks by the EC under any regulations or Directives. These conclusions from the Study Mandate have resulted in a Standardisation Mandate for the preparation of a draft standard. Mandate M/304 for such work was accepted and approved by CEN in December 2001 and passed to the same committee, TC248. The development of the requisite technical standard(s) is now underway. Once the necessary mandated technical standards have been agreed, sleepwear sold throughout the EU will have to comply with the agreed performance requirements. Thus the future should offer an enhanced level of fire safety for nightwear, and protection for the most vulnerable, such as the very young and the elderly.

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9 Environmental and Regulatory Matters The saga of the effects, benign or malignant, of brominated diphenyl ethers continues, with hope that a more scientific approach has at last been seen as the route forward. Waste directives relevant to flame retardants have now been promulgated by the EU and the general attitude to halogenated species also continues to attract attention in the chemical community. This chapter covers some comments and information relating to fire safety, recycling and environmental issues. 9.1 Fire Safety Fire safety is an integral part of fire precautions, which aim to minimise the number of fires and the damage from them. These measures hinder the initiation of fires, limit their propagation and, if possible, exclude flashover. Preventing fires or delaying them makes escape possible over a longer period of time. As a result, life, health and property are efficiently protected. A fire always follows the same basic pattern of initiation, development to a full fire and then its decrease. Fire precautions for combustible materials only apply to the early stage of a fire, i.e., the initiating fire phase by preventing ignition and by influencing the parameters of fire propagation and heat release. The influence of new legislation is essential for increasing the fire safety level in many fields. One striking example is the introduction of the UK regulations for flame retarded upholstered furniture in 1988. It shows a drop of fires and a dramatic fall in deaths caused by such furniture. Compare the figures for 1988 of 4818 recorded fires and 247 deaths to 1993 when there were 3746 fires and 146 deaths. The fire safety of electrical and electronic equipment is promulgated by rules and regulations for product safety laid down mainly by bodies such as Underwriters’ Laboratories (UL) in the USA, and used all over the world. Standards organisations like the International Electrical Commission (IEC) have fire safety requirements that may sometimes be based on those in UL standards. Plastics used in E&E equipment have to meet both materials and finished components fire safety requirements. They are part of product safety standards like UL 1950, CSA 22.2, IEC 950 and EN 60950 for business machines and UL 1410, UL 746, IEC 65 and EN 60065 for the safety of consumer electronic items (see Table 9.1). The flammability of the plastics materials covered by various UL safety standards are covered by the ubiquitous UL94; ‘Tests for flammability of plastics materials for parts in devices and appliances’ and its counterpart IEC 707, to evaluate their performance with respect to resistance to ignition and flame propagation. Depending on the requirements, materials have to meet horizontal burning tests, UL94 HB or the more stringent vertical burning tests, Class UL94 V-2, V-1, V-0 OR 5V. These tests simulate ignition sources of lower energy that may occur in E&E equipment and impinge on plastics parts in electrical components. Materials meeting the highest levels of these Bunsen burner tests, V-0 or 5V, have proved most effective in conferring a high level of safety to E&E equipment against both internal and external sources of low energy ignition. Contrary to the USA, where UL94 V-0 classification is nearly always required for plastics materials used in office and consumer electronics; in Europe, according to IEC 65, besides plastics used as fire enclosures, major plastics parts like TV-set back plates and housings only have to fulfil the horizontal classification, HB.

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Table 9.1 Product safety standards Business Equipment UL 1950 Underwriters’ Laboratories. Information technology equipment including electrical business equipment. CSA 22.2 Canadian Standards Association. Safety of information technology equipment, including electrical business equipment. IEC 950 International Electrotechnical Commission. Safety of information technology equipment, including electrical business equipment. EN 60950 / European Standard. Safety of information technology equipment, including A2 electrical business equipment. Consumer Equipment UL 1410 Underwriters’ Laboratories. Television receivers and high-voltage video products. Underwriters’ Laboratories. Polymeric materials UL 746 Short term property evaluations A Long term property evaluations B Use in electrical equipment evaluations C Fabricated parts D Industrial laminates, filament wound tubing, vulcanised fibre, and materials used E in printed wiring boards IEC 65 International Electrotechnical Commission. Safety requirements for mains operated electronic and related apparatus for household and similar general use. EN 60065 European Standard. Safety requirements for mains operated electronic and related apparatus for household and similar general use.

In a Draft for the revision of IEC 65 issued in the late 90s, basically no more flammability requirements at all are foreseen if the plastics materials exceed a certain distance from potential ignition sources with open circuit voltage. The same is true if potential ignition sources are protected by a fire enclosure; the other materials in a TV will require no safety classification. The new IEC 65 draft would thus allow the use of TV backplates and housings without any fire safety classification, because it relies on the technical design of the TV rather than on the safety level of the materials used. In the past, in Europe, plastics used for backplates and housings in office and consumer electronics virtually all complied with the high specifications of V-0 and V-1 classifications. This guaranteed a high level of fire safety of materials against internal fire sources plus external ones like candles. For TV sets, this was done on a voluntary basis, as, in principle, only the low levels of fire safety requirements for materials in IEC 65 had to be met.

9.1.1 European Standards for Television Sets Starting in Germany in 1993, requirements that excluded the use of halogenated flame-retardants and plastics for copiers, PCs and printers were introduced. These were given eco-labels (‘Blue Angel’ Eco-label). TVs that did contain them were deprecated in consumer magazines. As a consequence, the majority of TVs available in Europe now no longer contain flame retardants at all in backplates and housings. Backplates and housings make up the majority of plastics used in TVs. The use of materials with lower safety levels in such appreciable amounts could affect the overall fire safety level of E&E equipment with, as a consequence, a lower degree of protection for life or property. In addition, as more fires would result, the environment would also become affected. Therefore, fire safety should be included as an environmentally relevant criterion in the requirements for eco-labels and consumer magazines.

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Introducing fire safety, as an environmental criterion, would further fit into the attempts worldwide to hold and extend the existing high level of fire precautions. The international harmonisation of fire regulations in building, transportation and electrical engineering and electronics will eventually create global requirements for combustible materials and finished parts where high levels of fire safety will have to be achieved. Work in the US at the end of the 1980s by the then National Bureau of Standards (now the National Institute of Standards and Technology) had conclusively shown that housings containing flame retardants and so meeting higher fire safety requirements better resisted ignition and delayed flame propagation and subsequent involvement of the whole apparatus in the fire than non-flame retarded products (NBS Special Publication 749, 1988). It was shown that the total quantity of toxic combustion products released by the flame-retarded plastics (expressed as carbon monoxide equivalents) was one-third that of non-flame retarded plastics. An extensive, more recent, study by an independent fire consultancy in Germany has confirmed such findings for TVs and PC monitors and has warned against ignoring fire safety in any push for ‘chemical correctness’ and protection of the environment. Findings from this work include: •

The materials flammability tests carried out showed that sufficiently flame retarded plastics meet the high requirements of vertical tests, UL95 V. The low flame retardancy of non-flame retarded plastics only met the lower horizontal tests, UL94 HB.

•

The tests with external ignition sources of increasing intensity showed that flame retarded UL94 V plastics generally do not burn, whereas HB-rated plastics readily ignite when exposed to the lowest energy ignition source, typical of a short-circuit or to accidental contact with an open flame.

•

Older model European TVs and backplates generally have higher safety levels than new sets currently available in Germany.

•

New TV sets and backplates purchased in Germany can in most cases be ignited by the lowest energy ignition source.

•

TVs bought in Japan and the USA have high to very high fire safety levels.

•

New PC monitors have high fire safety levels. They do not burn when exposed to the different ignition sources.

•

In two simulated ‘real life’ fire tests in a fully furnished room, a new TV purchased in Germany when ignited by the lowest level of heat source, led to flashover in the room after just about 7 minutes. A TV form the USA did not ignite and did not burn at all, even when exposed to the highest intensity ignition sources.

There is therefore a need to use plastics parts with a higher level of fire safety meeting the requirements of UL94 Vertical tests so as to ensure adequate consumer protection. External fire sources, inadequate design, manufacturing faults or defects due to simple wear and tear, plus consumer misuse may lead to flashover and fully developed fires in a very short time if housings and backplates are not flame retarded to meet the vertical test criteria. To optimise fire safety for TVs in Europe, housings and backplates should be made resistant to external ignition sources at the lower end such as candles. This could be achieved by harmonising fire safety standards for consumer electronics with the North American requirements by upgrading the IEC 65 Standard used in Europe. Fire safety plays a key role in society, because it helps to reduce fire hazard and so prevent fires. It contributes to the saving of human lives, to protect property and, indirectly the environment. Therefore, the objective of all should be to hold and improve fire safety levels in all fire and environmental regulations and technical standards.

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A leading European fire expert, Jurgen Troitzsch, has spoken out about the weakness of the European standard of flame retardancy for TV sets. As fire safety standards have been relaxed in Sweden, fires attributed to E&E increased by >30% during 5 years to 2000.

9.1.2 Brominated Flame Retardants The Brominated Flame Retardant Industry Panel, the US industry trade association within the Chemical Manufacturers’ Association commissioned work to quantify the benefit derived from BFRs in the USA. The basis of this analysis is US fire data from the National Fire Protection Association (NFPA). This study concluded that within US experience, the total number of lives saved as a result of the use of brominated flame retardants in the analysed products ranges from 630 to nearly 1000 a year (Table 9.2). Table 9.2 Estimated lives saved by brominated flame retardants annually in the USA Product flame Total lives saved Maximum Total lives Total lives retarded by from secondary potential lives saved from saved brominated ignition saved direct ignition additives Television and 90 100 190 510 appliances Electrical wiring > 80 > 80 > 80 Fabric back-coating 144 160 Cushioning 216 216 Total > 630 > 960 Source: ‘The Contribution of Brominated Flame Retardants to Life Safety in the United States’, Benjamin/Clark Associates, Inc., reproduced with permission from Speciality Chemicals Magazine.

There have been ongoing discussions about emissions from the incineration of plastics that have been flame-retarded. On this issue the WHO’s International Program for Chemical Safety has stated of PBDEs that properly controlled incineration, i.e., according to current European regulations, does not lead to the emission of significant quantities of dioxins or furans. There has also been some discussion about what happens when products made with BFRs burn in accidental fires, such as the catastrophic fire at Düsseldorf Airport in 1996. However, the official report on the fire stated that dioxins and furans were either not detected or were found at levels well under the limit values considered today. The Fire and Environmental Protection Service, a highly respected organisation in German and European fire safety circles, has shown by the scrupulous analysis of the outcome of fires involving plastics materials, and two well documented German fire disasters that the cancer risk from PAH is up to 500 times higher than that of polyhalogenated dioxins and furans. The Düsseldorf airport and Lengerich fires gave rise to wild speculation about the chemical species that caused and represented the most danger. As with all fires it was shown that carbon monoxide contributes overwhelmingly to the toxic hazards generated and causes over 90% of fatalities in fires. Decomposition products from flame retardants, like HBr, HCl and HCN, do not play a role in the acute toxicity of fire gases, which is driven by carbon monoxide. This is also true for the formation of dioxins and furans. PAHs are found in high amounts in all fires involving any natural and synthetic carbon-based materials (i.e., almost any non-metallic material) and include carcinogens. Polyhalogenated dibenzodioxins (PHDD) and furans are generated from organic or inorganic

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compounds in fires at usually 3 orders of magnitude lower amounts, and then only when halogencontaining materials are present. The impact of PAHs and PHDD and furans in the two major fires mentioned showed that the cancer risk from PHDD/Fs is substantially lower than that of PAHs. Both pollutants are strongly bound to soot and they are of low bioavailability. This explains why no chronic toxicity effects from these pollutants were reported, not only by persons accidentally exposed to fire gases during one exposure, but also from frequently exposed professionals such as fire fighters and sanitation personnel. The findings of these two fires indicate that the chronic toxicity potential from dioxins and furans is highly overestimated and that the contribution of polybrominated dioxins and furans released by the flame-retarded plastics is negligible. Regarding the end use and also recycling and incineration aspects, more and more studies have been conducted on smoke and the products of decomposition. In 1996, the well-respected German testing centre ‘Forschungszentrum Karlsruhe’ ran combustion trials at its TAMARA pilot incinerator. Results indicate that, even under extreme conditions, electrical and electronic (E&E) plastic waste can safely undergo co-combustion with municipal solids. The work carried out at Karlsruhe has given further proof that “municipal solid waste combustion is an ecologically acceptable and economically sound disposal route for typical amounts of electrical and electronic waste containing brominated flame retardants”. Some of the main conclusions of this work are: •

The high amounts of E&E plastic waste material added has a positive influence on the combustion process (i.e., cleaner and more complete combustion) and the burnout of the bottom ashes has improved.

•

The dioxin and furan levels remained within the range typically found in such incineration plants – the addition of the extra E&E waste did not increase these levels.

•

Reflecting on the emissions throughout the production, use and disposal of TV sets, the latest LCA studies conclude that there is significantly higher emission of polycyclic aromatic hydrocarbons (PAH) and halogenated dibenzodioxins/furans for non-flame retardant TVs.

The positive contribution of brominated flame retardants as a life saver is a proven fact and European manufacturers of electronic goods should not jeopardise fire safety in an attempt to gain market acceptability. As fire safety standards have been relaxed in Sweden, fires attributed to EEE increased by >30% during 5 years to 2000. E&E enclosures made from flame-retarded resins are effective in preventing the ignition and spread of fire, in turn saving lives and the destruction of property. Numerous studies and a broad base of fire experience have demonstrated the value of flame retardants. Some of the conclusions that these studies point out are that, compared to plastics with no flame retardants, FR plastics: • • •

Provide up to 15 times more escape time. Release only one-third the amount of toxic gases (CO equivalents). Generate essentially the same amount of smoke.

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In the US, the estimated annual saving of life by the use of BFRs in E&E is 190, with a maximum figure of 510 souls. European statistics have been analysed and show that at least 16 lives are lost each year as a direct result of TV fires, with the true figure perhaps up to ten times higher. Such data reaffirm the need for FR plastics of the highest safety standards to ensure appropriate consumer protection. 9.2 Brominated Flame Retardants Brominated flame retardants (BFRs) are often the most effective when both performance and cost are considered. While these FRs are of positive benefit, used to protect the polymers that make up television sets, personal computers, soft furnishings, etc., they are now an issue related to environmental pollution and, in some quarters, deemed toxic. Some studies indicating the presence of polybrominated diphenylethers (PBDEs) in marine life and breast milk have added fuel to the environmental lobby’s calls to have these products banned or their use severely restricted. Manufacture of BFRs requires specific handling and expertise and, for this reason, they are produced in a few specialised facilities around the world. In response to concerns about their products and to focus their efforts in research, the major producers have established an organisation to steer the work. The Bromine Science and Environmental Forum (BSEF), which comprises Albemarle, Dead Sea Bromine, Great Lakes Chemical, Elf Atochem (as was) and Tosoh, was established in 1997 to conduct scientific research and to provide scientific data to support the safe use of bromine-containing products. The BSEF admitted that brominated compounds and halogenated materials in general have had a bad press. But the industry has for some time sought to look at the issues surrounding BFRs and their use by addressing environmental exposure and looking at product composition. Industry’s commitment does not propose a ban or phaseout of BFRs. Brominated flame retardants can be divided into three main groups: polybrominated diphenyl ethers (PBDE), hexabromocyclododecane (HBCD) and tetrabromobisphenol-A (TBBPA), which is by far the most widely produced and used of all the brominated flame retardants. Of the PBDE group, decabromodiphenyl ether (decaBDE) is the most widely used and, according to studies, no trace of decaBDE has been found in the environment. What is more, current research has shown that this compound cannot be broken down into the shorter chain compounds. TBBPA and HBCD, used in a wide range of products, have not been found in the environment either, according to this current research. Meanwhile the shorter chain PBDEs have been found widely, particularly in the marine environment. However, the chairman of the BSEF has commented that the flame retardant industry has not and does not produce or use these shorter chain compounds in any large quantity. In fact recent studies show that pentabromodiphenyl ether (pentaBDE) was widely used by the mining and drilling industry in the 1980s and early 1990s as a hydraulic fluid, yet no one looks into these industries to explain the presence of these compounds in marine life. These latter industries seemed unwilling, at the time, to contribute to the debate or the research. It must be remembered that the flame retardant industry is a relatively young one, established in the early 1970s, and the BSEF highlights a report published in 1992, which provides evidence of PBDEs in sediment dating back to the 1940s. So what are the other possible sources of these compounds? Apart from the historic uses already mentioned, it is known that many organobromine compounds, including chemical precursors of brominated flame retardants are naturally present in marine life.

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There has always been a school of thought that anything naturally occurring, part of the environment, would be dealt with by nature, being easily broken down. This theory may need reappraisal after a study at Carlton University. This claims (in Environmental Science and Technology, an ACS publication) to have found a naturally occurring substance that is similar in chemical structure to PCBs, an industrial chemical banned because of damage it caused to the reproductive systems of wildlife, particularly birds, that had eaten fish from polluted waters. These pollutants contain chlorine and bromine and the work appears to have identified a naturally occurring substance that is as persistent as any man-made pollutant. If the findings are proven, it could mean a radical rethink not only by the many environmental groups lobbying to ban halogencontaining compounds, but also a radical look at the policy making business. Of course, the flame retardants industry cannot rule out misuse by itself or its customers, and to this end producers set up a programme of product stewardship in order to educate all those using brominated flame retardants as to best practice. BFR loading in polymers is illustrated in Table 9.3. Table 9.3 Examples of brominated flame retardant loadings in polymers (V-0 classified) Loading of BFR Loading of Sb2O3 Base Polymer Brominated flame retardant (%) (%) 23 8 Polypropylene Decabromophenyl ether 27 8 Ethylene bis(tetrabromophthalimide) Polystyrene Decabromodiphenyl ether 12 4 Tetrabromobisphenol-A 15 4 ABS Octobromodiphenyl ether 20 6 Tetrabromobisphenol-A 20 4 4 12 PET Decabromodiphenyl ether 4 17 Pentabromobenzyl acrylate 4 18 TBBPA carbonate oligomer Source: R Borms, European Chemical News.

To facilitate a better understanding of the issues surrounding BFRs, the BSEF set up a research programme, which was carried out by independent researchers at the Netherlands Fisheries Institute. The research has been broken down into several main areas: Food chain residues will look at how the shorter chain PBDEs have entered the marine life, the aim being to trace the route and follow it right back to its source. Sediment core studies will also be carried out, whereby sediment from the ocean will be taken, dated and analysed. This will put a timescale to the presence of these brominated compounds. The results will be looked at in relation to the existence of the flame retardant industry and any possible use prior to the development of BFRs. The programme is expected to last two years, with summaries of progress published on a regular basis. Other issues that the BSEF will address are recycling and life cycle analysis (LCA). Consumer safety is an ever-growing issue. With consumer purchasing power rising and the number of personal computers and other electronic equipment in the home increasing, politicians and those in a position to make policy, will have to weigh up some very serious issues. Manufacturers of electrical products, particularly those aimed at the European market, may have to look at the possibility of consumers laying the blame squarely at their door, when it is realised that a serious incident could, perhaps, have been prevented if adequate levels of BFRs had been used. A report commissioned by the UK Department of Trade and Industry has indicated the benefits from BFRs outweigh the possible hazard risks to the environment and human health. The report

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entitled ‘Risks and Benefits in the Use of Flame Retardants in Consumer Products’ describes the work carried out at the Polymer Research Centre of Surrey University, England. It concludes that there are many benefits from using flame retardants. An example is the reduction of the risk of death or injury from a fire involving consumer products, such as upholstered furniture, by between 30-90% when flame retardants are used. The UK government accepted the report as an important contribution to the debate on the use of FRs in consumer products and is also supportive of the risk assessment work commissioned by the EU, underway in the mid 1990s. There have been, however, concerns about the safety of brominated flame retardants. Although in 1995 the World Health Organisation (WHO) found that the risk to the general population from TBBA was ‘insignificant’, more recent research has cast doubt on this conclusion. Concern arose in Sweden following revelations that brominated FRs caused irreversible brain damage and disrupted thyroid systems of newborn mice. Also, levels of polybrominated diphenyl ether have been found in the breast milk of Swedish women over the last 25 years. With claims that TBBA has hormonedisrupting effects, the Swedish Chemicals Inspectorate recommended that two groups of brominated flame retardants be phased out within five years. A further safety concern was that combustion of brominated flame retardants might lead to the formation of bromodioxins. The possibility of combustion is perhaps less of a worry because the dioxins are produced at around 600 °C – higher than processing temperatures but lower than fire temperatures. And old computers and televisions are usually dumped in landfill sites rather than burned. Furthermore, manufacturers are now developing brominated FRs that do not produce dioxins on combustion, and others that char rather than burn so that the bromine is retained in the residue. Nonetheless, the WHO recommended that brominated flame retardants ‘should not be used where suitable replacements are available’. Plastics containing no flame retardants are now being used in computer monitor housings. These have an internal fireproof metal layer, which also provides electromagnetic shielding. Whether this is a satisfactory substitute for flame retardants is still very uncertain. Moves to legislate for the recycling of electrical products and the partial phase-out of some brominated flame retardants has resulted in the WEEE and RoHS Directives (see Sections 9.3 and 9.4). Results of the studies commissioned by the BSEF have given a strong signal of support for the ‘probity’ of BFRs. Findings from the highly regarded GfA laboratory at the University of Erlangen, Germany say that BFRs do not hinder plastics from being recycled and can withstand at least five recycles. This has important implications for the use of plastics in electronics since it was shown that HIPS retarded with decaBDPE will meet the requirements of the German Chemicals Banning Ordinance, which is regarded as one of the strictest regulations in existence. The findings provide strong support for the BFRs known to be among the most efficacious of flame retardants for plastics, especially engineering ones. Three separate elements within the test programme provided the following results: •

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Formation of dioxins/furans: A compound containing standard loadings of decaBDPE was injection moulded and reground to simulate recycling. After five cycles the material was analysed for brominated dioxins and furans. The compound showed no detectable amounts and the recycled forms showed levels below the limit of the German Dioxin Decree by a factor of about 40.

Flame Retardants for Plastics Market Report

•

Debromination: The same compound was analysed for possible degradation of the FR additive. Comparison of concentrations before and after recycling showed no change, indicating that no decomposition (i.e., debromination) had occurred.

•

Workplace exposure: A flame retarded PS was subjected to two successive simulated recycling cycles and workplace exposure to PBDD/F was monitored during processing. At all stages, exposure to dioxins/furans was below the German workplace limits by about two orders of magnitude.

The BSEF said that recycling was the key to future environmental sustainability of many industrial processes and it was necessary for additives manufacturers also to help users of plastics (e.g., makers of electronic equipment) to ‘close the loop’. Another study, at a recycling plant in Sweden, showed that the workers were being exposed to diphenyl ethers. BSEF is collaborating with the company to develop the best practice for its processes. In September 2001, the European Parliament took the unprecedented step of voting to ban two chemicals for which risk assessments were still ongoing. Octabromodiphenyl ether (octaBDE) and decabromodiphenyl ether (decaBDE) were lumped in with pentaBDE during a debate on the EC’s proposed ban on the latter chemical, which was based on an already completed risk assessment. All three flame retardants would be banned by 2006 according to the parliament. OctaBDE should be banned by mid-2003 and the deca- version three years later. However the decaBDE ban would be repealed if the completed risk assessment shows it to be harmless. Penta residues in other substances must not exceed 0.1%, according to the parliament vote, rather than the 5% limit proposed by the EC. These measures, heavily altered, reached final adoption in December 2002, as a formal Amendment to the ‘Use Ban’ Directive of 1976 that relates to restrictions imposed on the marketing and use of certain substances deemed dangerous after suitable scientific investigation. Parliament and Council have decided to exclude from this Directive decaBDE in view of its importance for fire safety and due to an ongoing scientific risk assessment being due to be finalised by the EU in 2003. The Directive will consequently prohibit only octaBDE and pentaBDE from the EU market by mid-2004. The risk assessment of decaBDE has so far found no significant risk and its completion in the Summer of 2003 will be the basis for any future policy decision on decaBDE. DecaBDE is widely used to protect furniture textiles from fire sources in accordance with UK and Irish furniture fire safety legislation, which provides the consumer with the highest levels of fire safety in the world. An estimated 3,160 lives have been saved by the UK legislation alone in the period 1988-2000. A new study carried out by Toronto University finds that, of the 3 PBDE flame retardants, neither decaBDE nor octaBDE is likely to be transported in the environment over long distances. The study clarifies recent reports from the Arctic Monitoring and Assessment Programme (AMAP) which incorrectly stated that PBDEs had been found in the Arctic when this should only have referred to the constituents of pentaBDE. The potential for substances to be transported over long distances or as it is technically known, the potential for long-range transport (LRT), is one of the four recognised criteria in assessing whether

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or not a substance might qualify as a persistent organic pollutant (POP). (The other three criteria for defining a POP are persistence, bioaccumulation and toxicity.) Researchers in the field of environmental modelling at Toronto University have studied the potential for LRT of the constituents of the three PBDE flame retardants known as pentaBDE, octaBDE and decaBDE. These products have different physico-chemical and also different toxicological properties. The recently completed study used the most advanced mathematical models to estimate whether or not the investigated substances have a potential for LRT. The various models used all came to the same conclusions: •

PBDEs with a low degree of bromination such as those contained in commercial pentaBDE are likely to undergo LRT

•

PBDEs with seven or more bromine substitutions, such as those which make up most of commercial octaBDE and which make up the total content of decaBDE, are likely not to be subject to LRT.

•

These conclusions are supported by recently published monitoring studies, which find the constituents of pentaBDE at remote locations (Arctic, Siberia, etc.), but which do not find any substances related to octaBDE or decaBDE at the same locations.

The Dutch Ministry of the Environment announced in February 2003 that ‘the temporary ban of the production, trade and use of the flame retardant FR-720 shall not be prolonged’ This means that imports into the Netherlands of BDBPT and products containing BDBPT will not be restricted. FR720 is the bis(2,3 dibromo)propyl ether of TBBA. The temporary ban proved unjustified as it lacked scientific evidence that BDBPT should be of any concern with respect to acute toxicity. The product is not found in the environment and an initial risk assessment in January 2002 commissioned by the industry for the Dutch Government showed the substance was of no concern. The EU Commission had opened an infringement procedure against the Dutch Government on the basis of an unjustified barrier to trade. The ban would have also set a precedent whereby any EU Member State could have banned any substance merely on the grounds of incomplete data and ignoring the need for further science to be conducted. Following the decision to lift the ban, further research is to be conducted on behalf of the Ministry of Environment by RIVM, the Dutch National Institute for Public Health and the Environment with publication by end of 2003. 9.3 EU Directives The German Environment Ministry attacked European proposals to ban individual substances, such as specific flame retardants in the draft regulations for the recycling of electrical and electronics equipment. They were backed by the country’s Ministry of Economic Affairs. The Environment Ministry saw no need for binding recycling targets and opposed substance bans such as those proposed for lead and the PBDE and PBB flame retardants. Both Ministries were concerned at the excessively prescriptive and restrictive system being proposed at that time (2000) for electrical and electronic waste by the EU Commission’s Environment Directorate-General. They had planned to include a phase-out of PBDEs in the disposal of Waste Electrical and Electronic Equipment (WEEE) Directive, in spite of the fact that preliminary conclusions under EU risk assessments indicated that there was no need for risk reduction from the two types, decaBDE and octaBDE, mainly used in such equipment.

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The German criticism is part of a growing call that substance restrictions should have no place in waste legislation, but should be separately considered and be based on life-cycle risk assessments. For example, German legislation on end-of-life IT equipment does not contain any substance restrictions. Studies in Germany have effectively demonstrated that polystyrene compounds flame retarded with decaBDE, which is widely used for housings of such equipment, meet the stringent demands of the German Chemicals Banning Ordinance. The studies also indicated that no detectable quantities of brominated dioxins or furans were formed during recycling, that there was no debromination of the additive and that the exposure of workers to dioxins/furans was at least two orders of magnitude below German workplace limits. Another factor is the consideration that the material bans contained in the draft WEEE Directive would infringe international trade agreements. The surprise move by the EC in mid-2000 to make three separate pieces of legislation out of a single original draft directive on waste electrical and electronic equipment (WEEE) served to concentrate attention on brominated flame retardants (BFRs) in such applications. Under the early draft, EU countries ‘shall ensure that the use of lead, mercury, cadmium, hexavalent chromium, PBB, and PBDEs (polybrominated biphenyls and polybrominated diphenyl ethers) in electrical and electronic equipment is substituted on 1 January 2008.’ These have now become the subject of the Restriction of Hazardous Substances directive (RoHS). Additionally the Commission was proposing that all plastics containing BFRs be separated out from electrical and electronic equipment before recycling or disposal. This could have left the plastics industry trying to face two ways at the same time. Restrictions on BFRs would rob companies of some of the most effective flame retardants available, at a time when politicians and fire-fighters are pressing for increased levels of flame retardancy for plastics in certain E&E applications. The proposals on PBBs would not affect the plastics market, since their production had already been discontinued and very few E&E makers use the substances. However, PBDEs are widely used by the industry. The legislation, although directed at equipment used in Europe, has international implications, given the high levels of imports, especially from Asia, of products like personal computers and small appliances. Indeed, the feeling at the influential US Association of State Fire Marshals is such that it has complained to Brussels that moves to ban BFRs would compromise fire safety. There are even indications that it could try to block importation of any E&E equipment whose fire safety is reduced as a result of the WEEE proposals. The draft directive showed that the commission was concerned about risks involved in landfilling, incinerating, and recycling plastics that contain BFRs. For example, in one section on recycling the draft states: ‘Halogenated substances contained in WEEE, in particular BFRs, are also of concern during the extrusion of plastics, which is part of the plastic recycling. This is due to the fact that during recycling of plastics containing BFRs, brominated dibenzofurans and brominated dibenzop-dioxins may be formed. Various studies suggest that the risk of generation of dioxins is a reason for the complete lack of recycling of plastics containing BFRs.’ However, the industry-funded Bromine Science and Environmental Foundation (BSEF) in Brussels says that the proposals would very likely be changed significantly, since they now have to be considered by both the European Parliament and EU member states. According to the BSEF, indepth studies completed in Germany and discussed earlier in this chapter show that recycling of PBDEs meets the strictest dioxin legislation in the world.

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Given the tough recycling targets set by the WEEE proposal (EU countries will be required to collect at least 4 kg of waste E&E equipment per person per year), it seems difficult to imagine enforced separation of all BFR plastics if this is going to impose additional costs for the very plastics most suited to recycling. For decaBDE, the risk assessment has so far found no significant risk and, following the assessment's completion in the Summer of 2003, it will be possible for the EU to exempt decaBDE from phase-out under the RoHS Directive. The importance of the 11 October WEEE agreement is that the EU will base its decision for decaBDE on scientific risk assessment and individual EU Member States will not be able to undermine this. Under the Council/Parliament agreement, each EU Member State will have to wait until July 2006 to introduce the restrictions under the RoHS Directive, thus maintaining the cohesion of the EU Single Market for electrical and electronic products. The European Brominated Flame Retardant Industry Panel (EBFRIP) observed that “The Conciliation agreement means that the future EU regulatory status of decaBDE will be based on scientific risk assessment. This is surely a welcome conclusion for decaBDE, a chemical substance for which a significant risk has not been identified either for the environment or for human health and which continues to save 1000s of lives through fire prevention”. In February 2003, the EU Directives on the management of electrical and electronic waste (WEEE) and hazardous substances in E&E equipment (RoHS) were published in the EU official journal. By 13 August 2004, EU Member States will have to transpose both laws onto their own national legislation. Under the WEEE Directive, manufacturers will then have another 2 years - until 31 December 2006 - to reach the recycling and recovery targets set up for the different categories of E&E appliance. By this time, plastics containing brominated flame retardants (BFRs) will have to be separated prior to recycling, energy recovery or disposal. The Directive's requirement to increase mechanical recycling is an advantage for plastics containing BFRs as they offer high level of stability during the recycling process. The separation requirement will in turn facilitate the recycling and recovery of plastics containing BFRs for which there is a wide range of tested recycling and recovery technologies. Under the RoHS law, manufacturers will have to cease using PBB, pentaBDE, and octaBDE in new E&E equipment from 1st July 2006. 9.4 Recycling Matters The bromine industry became concerned in early 2000 about the formal proposal from the EC to mandate increased levels of recycling for Waste Electrical and Electronic Equipment (WEEE). The BSEF stated that the requirement to separate all WEEE containing halogenated flame retardants would increase costs for collection and disposal. This is in complete contrast to Japanese copier makers who were specifying the very same halogenated flame retardants on grounds of the relative ease of recycling them. Ricoh and Fuji-Xerox were specifying 30% and 25% recycled ABS for mass production during 2000. The Japanese copier industry established that recycled ABS can match the performance requirements set down for virgin material. The brominated flame retardants used in the compounds are said to be stable and have the advantage of not hydrolysing during the recycling process. In addition, only brominated FRs can enable ABS to meet the fire safety test 5V, claimed to be the highest level of safety. A closed loop recycling technology for components that contain brominated flame retardants has been specifically developed by Fuji Xerox, in conjunction with the resin manufacturer Ube Cycon, by purchasing crushed and granulated waste components, decontaminating, re-compounding and

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shipping back a quality-assured compound. This encourages the equipment manufacturer to make the effort of controlling the quality of the waste parts. It also allows the recycled resin to be pigmented at the same time as it is reprocessed with the addition of virgin material and additives. This is seen as an advantage over conventional processes, in which the colouring is usually added after the recyclate has been pelletised. This, in turn, required secondary melt processing, with possible further heat deterioration and additional costs. The company sees the ABS system as a model for recycling other resins. The top cover of the DocuCentre 550 copier is moulded in ABS, flame retarded with a brominebased additive to meet 5V UL94, having been compounded from virgin material plus reclaim from the same part. Fuji Xerox has been recycling unretarded HB ABS since 1998 and has established an upgrade recycling technique that raises the HB rating to 5V. A similar system has been introduced by Ricoh, recycling 5V material for the exterior cover of its copiers. Reclaim accounts for 3-5% of all resin and the technology was introduced on 8 new models. The trend is expected to increase, both in the number of models and the quantity of material recycled in each. The mouldings for recycling are chopped into pieces between 4 and 15 mm in size. After cleaning the chips are sent to the resin manufacturer for re-compounding. Addition rates of reclaimed material in subsequent mouldings range from 25 to 75% at Fuji and 30-70% at Ricoh. As the recycled resin shows some drop in properties, and is recycled on average two or three times, the amount of virgin resin must be increased. The cost of reclaimed material is higher than the equivalent virgin compound but Fuji Xerox expects that, long-term, closed-loop recycling will reduce procurement cost of raw materials and fully cover the cost of reclaiming. A Japanese study in 2000 by Techno Polymer, a leading plastics manufacturer in Japan suggests that key plastics that are retarded with brominated additives are, in fact, easier to recycle. The company compared various ABS compounds, some containing a brominated epoxy oligomer and others various organic phosphate esters. It was concluded that “among the commercially available plastics suitable for business machines, only FR-ABS retarded by the brominated compound shows flawless recyclability in terms of keeping the original performance after the thermal history and accelerated hydrolysis testing”. The company also found that the recycled brominated ABS met the highest levels of fire safety, as represented by the UL94 5V classification, which is the test with which most copier makers comply. With regard to incineration, the European Brominated Flame Retardant Industry Panel (EBFRIP) has supported a programme at the TAMARA pilot incinerator of the Forschungszentrum Karlsruhe (the Karlsruhe Research Centre). The conclusion of this project (to be found at www.firesafety.org) is that, even under extreme conditions, E&E plastic waste rich in plastics containing BFRs can safely undergo co-combustion with municipal solid waste and it is an ecologically acceptable and economically sound disposal route for normal amounts of E&E waste containing brominated flame retardants. In addition, amounts of E&E plastic waste material added to municipal solid waste have a positive influence on the combustion process, giving a cleaner and more complete combustion, and the burnout of the bottom ashes is improved. The levels of dioxin and furan remained within the range typically found in such incineration plants and the addition of extra E&E waste does not increase these levels.

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Most municipal waste incinerators today add active carbon to the combustion procedures, as this effectively helps decrease the already-low concentrations of dioxins to near-zero levels. This stateof-the-art dioxin abatement technology guarantees compliance with air emission regulations, even if dioxin and furan levels were significantly higher than those found during the co-combustion test performed at Forschungszentrum Karlsruhe. Plastics that are flame retardant to the more stringent UL94 V-0 standard have been shown to reduce emissions to the environment compared to plastics flame retarded to the less stringent IEC65 horizontal burning (HB) standard, which has been more prevalent in Europe in recent times. The Swedish National Testing and Research Institute has developed a total life-cycle assessment (LCA) model directed at determining the cost of measures taken to attain a high level of fire safety. The first full application of that method was for TV sets that were V-0 or HB rated. The LCA concluded that the loading on the environment was less for the TV containing the brominated FR than for the TV set without FR. The main reason for this is the greater number of fires and the resultant environmental emissions associated with the TVs made from HB material. As the volumes of E&E items have increased it is now seen that there must be adequate treatment options to replace landfill. Plastics, on average, represent 20% by weight of current E&E products, with the share estimated to rise in the future. With end-of-life recovery being an integral part of the life cycle of plastics, appropriate measures must be taken to ensure the maximum value is obtained from the plastics after their first life in E&E equipment. The proposed WEEE directive imposes a collection target of 4kg per person in the EU by 2006. It also establishes recovery targets of 60-80% and reuse/recycle targets of 50 to 75% depending on the type of item involved. Plastics containing BFRs enjoy a wide range of options at end of life and fit into the accepted ‘mantra’ of reduce, reuse, recycle. On the reduce level, flame retardants contribute due to fires prevented and the resulting reduction in the need to replace fire-damaged goods that would contain fresh material. Plastics containing BFRs can be reused in the same application as shown by the recycling (refill and reuse) of copier toner cartridges. Some of the considerations when choosing recycling options include: • • • • •

The cost and complexity of disassembling the different types of E&E, Identifying the different components and compositions of the disassembled parts, Separating and sorting the various materials, such as metal coatings, paints, The ease of recycling the various materials obtained, and The value of the materials resulting from the recycle operation.

Contrary to the proposed WEEE directive many believe that a form of recycling is energy generation from plastic waste with bromine recovery as a form of recycle. Recycle should cover mechanical recycle in the originally intended application or in a downgraded application, or feedstock recovery with or without bromine recovery, or energy generation with at least the bromine recovered. Some think that energy recovery without any bromine should be classified as disposal, alongside landfill or incineration with no energy output at all. To take the mechanical recycling route, several steps such as sorting and dismantling are almost certainly involved, plus comminuting of larger pieces now present. Mechanical recycling can result in compounds for use in an original or lesser application, depending on the thoroughness of all the

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intermediate stages that may be necessary. It certainly offers the highest value for end of life E&E FR plastics. This method may be feasible for large plastic parts such as TV back covers and some copier, and other, enclosures where the cost of disassembly and sorting may be offset by the extra value obtained from such recycling compared to other options. A technique that could have application in a broader range of end-of-life E&E FR plastics is feedstock recycling. The EBFRIP in cooperation with the BSEF has carried out a feasibility study on bromine recovery from waste E&E. Plastics from the waste E&E are co-fed with municipal solid waste (MSW) either to a pyrolysis unit or to an incineration unit for syngas generation or energy recovery, respectively. The flue gas is scrubbed and bromine salts are recovered which can then be converted back to bromine, so closing the loop on the use of bromine in BFRs. Depending on the nature of the resultant waste ash it may be recovered for secondary materials, such as basalt, metal or cement. The conclusions of the feasibility study are that it is economically and ecologically feasible to perform feedstock recycling, or bromine recovery. The project could reduce the emission of so-called greenhouse gases and also provide bromine producers with the opportunity of recycling a minimum of 10,000 tonnes a year of bromine in Europe. The waste to energy recovery route covers energy via incineration or as a fuel source in smelters, cement kilns or chalk ovens as is often the case with plastic waste today. Past problems with standards of operation at incinerators, such as operating temperature, residence times and emissions, led to concerns over the incineration of plastics waste in the past. However, since that time more stringent requirements for operation have been introduced, such as a minimum of 850 °C in the combustion chamber, minimum of 2 sec residence time for the resulting flue gases at 850 °C, in the presence of at least 6% oxygen. The Association of Plastics manufacturers in Europe (APME) has issued a definitive report on the ‘Karlsruhe Trials’ at the TAMARA facility already mentioned above. This is entitled ‘Recycling of bromine from plastics containing brominated flame retardants in state-of-the-art combustion facilities’. This has demonstrated that in modern plants with suitable wet scrubbing equipment, recycling of bromine in plastics waste containing BFRs is technically feasible. The expectation is that mechanical recycling of plastics from WEEE will often not be efficient, so implementation of the EU directive on the management of such wastes will mean that such materials will be increasingly available for bromine recycling in such facilities. APME estimates that WEEE plastics comprise just over 3% of the 19 million tonnes of collectible post-consumer plastics in Europe. This quantity, of around 733,000 tonnes is projected to rise significantly in the future. EEE is defined by the directive as ‘all appliances dependant on electric currents or EM fields in order to work, and which use AC up to 1000V or DC up to 1500V’. This, of course, covers, business machines, telecommunications equipment, brown and white goods, small hand-held domestic appliances plus medical and other equipment such as sewing machines and household leisure and garden goods. The waste plastics become available for dedicated recovery after either a manual dismantling and separation process, or after mechanical shredding and refining. On average, around 30% of the plastics in E&E contain flame retardants of one type or another. In 2000, of the plastics with FRs used in E&E goods, 59% used non-halogenated types and the rest were halogenated. The major location of the BFRs is in business, data processing and telecomms equipment at 53% of EEE using BFRs. Brown goods have 22%, industrial items a further 7%, household ones just 2%

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with the remaining 16% spread over ‘others’. Interestingly, just one BFR represents over 50% of the total BFR market. This is tetrabromobisphenol-A. The incineration programme was designed for bromine levels in a mix of WEEE and ordinary MSW to be between 0.5 and 1.0 wt%. This is more than 100 times the typical concentration in MSW. Depending on the mix and type of WEEE the bromine could be found in the bottom ash, fly ash and/or the gas phase in varying proportions. Bromine was expected to promote volatility of metals, since metal bromides tend to have low boiling points. This was indeed observed as metal transfer to the fly ash increased for copper, lead, zinc and others present in the generality of the MSW. There was no significant correlation between increased bromine levels and the overall level of halogenated dioxins and furans; and the brominated dioxins and furans that were present were almost totally destroyed or removed. Bromine can be recovered from various species that reach the gas phase. APME estimate that up to 8000 tonnes of bromine a year is available for recovery from such facilities. Up to 2-3% of WEEE FR plastics can be safely added to the fuel mix in combustion facilities, well exceeding the amount that is ever likely to be produced. They also suggest a dedicated or multipurpose pyrolysis/gasification facility as a route for bromine recycling from WEEE plastics. More information is available on the APME website at www.apme.org. A further study, recently completed by TNO (the Dutch engineering, testing and scientific organisation) has concluded that the presence of bromine in plastics (as a flame retardant) does not adversely affect energy recovery equipment for household waste treatment. Levels of bromine in the plastic waste going to energy recovery can be easily increased by a factor of 9-10 times before any additional adverse effect could occur in the equipment. Like several materials found in the household waste stream, bromine has the potential of corrosive properties, which could by definition adversely affect the energy recovery equipment. However, given the presence in household waste of other potential corrosive materials like hydrochloric acid and the comparatively low levels of bromine (up to 100 times lower than chlorine), it was important to find out up to what level of plastics containing BFRs could be added to a feedstock recycling or an energy recovery facility without causing additional equipment corrosion. Currently, plastics containing BFRs form on average only 0.35% of the total waste going to household waste treatment. Levels of BFR containing plastics in the household waste are unlikely to exceed even 3% under the new EU Directive on Waste Electrical and Electronic Equipment (WEEE). Hence, BFR plastics are compatible with WEEE solutions such as feedstock and energy recovery. The study was funded by the European Brominated Flame Retardant Industry Panel (EBFRIP) and can be found at http://www.ebfrip.org. 9.5 Postscript Recent and current regulatory programmes and pronouncements, in Europe and nationally, about brominated flame retardants are but part of a political concept called Sustainability. Since the EU and its Market is a huge size, arguably second only to the USA, any legislation coming out of Europe that potentially affects trade in some way or another, is noted across the world. The generally accepted definition of sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. This implies that mankind’s collective effort to improve the quality of life on Earth will be sustainable

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if, and only if, the resulting perturbation is not allowed to exceed the capacity of our planet’s ecological support systems. This presupposes that the earth’s natural product cycles are by definition sustainable. In 1998, the United Nations Commission on Sustainable Development (UNCSD) recognised that business and industry would play a crucial role in the global quest for sustainable development and, on that occasion, UNCSD made reference to the OECD Risk Assessment Programme on brominated flame retardants as a model example of a global, voluntary chemical industry initiative. By contrast, the 2nd Integrated Product Policy (IPP) Conference in early 2001 explicitly acknowledged the hurdles barring the way to sustainable development and justified the exclusively ‘green’ focus of the proposed policy initiative on the grounds of political pragmatism. It set 3 key pre-conditions of success for IPP: • • •

The prices of green products must be competitive; Green product design must be encouraged; The market demand for green products must be stimulated.

In June 2001, the EU Committee of the Regions emphasised the need for IPP to be framed on the basis of the fundamental principles underpinning EU environmental policy. They are: a) the Precautionary Principle, and b) the Substitution Principle. The precautionary principle states that where there are threats of serious or irreversible damage, lack of scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation. In its Communication of 2/2/00 the European Commission emphasised that regulatory measures that invoke the Precautionary Principle should start from a scientific evaluation. This should be as complete as possible and should identify at each stage the degree of scientific uncertainty. The European Council endorsed the Precautionary Principle at the Nice Summit in December 2000, and recalled measures should be periodically reviewed and amended as necessary. In September 2001, the Danish EPA recommended that Danish enterprises, importers and retailers of electronic equipment should voluntarily reject products containing brominated FRs. This initiative came one month after the publication of the updated Danish EPA Action Plan on Brominated Flame Retardants. Its objective was the international phase-out of the use of the most problematic BFRs, the short-term focus being on the PBBs and PBDEs. A further objective of this Action Plan was to assess flame retardants that are potentially less harmful to the environment and health so as to facilitate substitution, thereby helping to promote the development of greener products. There has been much debate in the last four to five years around the sources of organohalogens found in apparently ‘threatened’ species (including man). There has been a school of thought that believes such chemicals can have only anthropogenic origins, but this has been increasingly challenged by the results of various studies. Back in 1999, the general scientific view tended to be that all organohalogens accumulating in wildlife came from industrial sources or other human activities. This included a report by a joint US/Canadian body, the International Joint Commission (IJC) responsible for environmental monitoring of the Great Lakes, which stated that there is ‘something non-biological’ about fluorinated, chlorinated and brominated organics.

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Other statements claimed that some types of synthetic compounds ‘are not found in nature’, including halogenated hydrocarbons such as PCBs, although the IJC shifted slightly later to say that the presence of BDPEs, chlorinated paraffins and naphthalenes in the tissue of a range of species ‘was a mystery’. Next, the first recorded instance of a naturally produced organohalogen accumulating in the eggs of wild birds and marine species was identified as 1,1-dimethyltetrabromodichloro-2,2-bipyrrole. As a result the investigators expressed the opinion that a better understanding of the natural sources of organohalogens was essential when regulations concerning anthropogenic organohalogens were being prepared. Subsequently, there were reports of a previously unknown natural organochlorine contaminant in the blubber of marine mammals and in birds, and the bioaccumulation of halogenated dimethylbipyrroles in the Arctic marine food chain. Since the first naturally occurring compound mentioned above, much work continues to be reported on organohalogens such as hexahalogenated dimethylbipyrroles (HDBPs) that are produced naturally by many types of algae and marine organisms and can accumulate in animals higher up the food chain. Natural brominated compounds have been detected in blubber extracts from marine animals. Other naturally occurring compounds such as methoxy tetrabromo diphenyl ether isomers have been reported and may be misinterpreted as methoxylated metabolites of tetrabromodiphenyl ether. Other interesting facts cover the generation of chlorine and bromine themselves. The natural production of chlorine occurs by the injection of sea-salt aerosol generated by wind stress into the air over ocean surfaces and is the major global source of atmospheric chlorine. The production rate for this natural phenomenon is estimated to be 50 times greater than the estimated anthropogenic production capacity of around 40 megatonnes. Turning the same model to calculating the bromine in sea salt aerosol, then the corresponding oceanic production rate is about 7 megatonnes, with the man-made figure being not much over one-half a megatonne. All this information suggests a reappraisal of the basis for much of the regulatory effort at both EU and national levels on BFRs. Although there is legitimate concern over some halogenated manmade chemicals, there has been an apparent distortion of perspective on the relative toxicity impact potentials (TIP) of anthropogenic versus naturally occurring organohalogens. The lack of adequate TIP data on alternatives to BFRs should give pause for thought, not to speak of the relative flame-retardant efficiency and design adequacy of the candidate substitutes. The politics of plastics additives and complex chemical species in general seem to be at variance with scientific findings and their interpretation. One global trend that has been gathering pace is utilising science to confirm the key reason for using FR technology in the first place – namely, that these products save lives and property. Sweden has been generally credited with being most strongly against FR additives, with its Chemical Inspectorate providing the leading critical voice. Yet, in April 2001, the Inspectorate criticised as ‘inconclusive’ some research by environmental activists in their case against brominated FRs. ‘Just because a fire retardant contains bromine does not make it dangerous’. Nevertheless, the Nordic countries are still looking closely at FR products. Important questions have been raised in Scandinavia about antimony, phosphate, and bromine-based FRs. But, again, the prevailing view highlights the role of these products in saving lives and property as the prime considerations. Much time in 2001 was spent in the EU Commission and the Parliament looking at brominated FRs in the context of the WEEE and hazardous substance ban (RoHS) directives. At one point the

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Commission considered banning all brominated FRs. Instead the Parliament passed a law that will ban rarely-used PBBs and PBDEs for E&E equipment. Risk assessments on two important additives, the decabromo and octabromo types, show that these chemicals are environmentally acceptable. In Tokyo, the Japan Environment Association changed its ecolabel criteria for copiers, printers and PCs. The change withdraws the exclusion of all BFRS to just PBBs and PBDEs, products that have little impact on the marketplace. Pressure for this change had filtered up from Japanese OEMs, who recognise the superior recyclability of BFR plastics and also the consumer demand for greater fire safety. In recent years, the National Academy of Sciences in the US has examined the effects on human health of 16 FR chemicals used to meet new furniture fire safety standards. The studies produced enough data for the Academy to definitely evaluate eight of these products. It concluded that there were no significant environmental or health concerns related to their use.

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European Suppliers of Flame Retardants – Company Names and Addresses A Schulman Pedro Colomalaan 25 B-2880 Bornem Belgium Tel: +32 38 944211 Fax: +32 38 897110 A Schulman GmbH Huettenstrasse 211 50170 Kerpen-Sindorf Germany Tel: +49 2273 5610 Fax: +49 2273 561350 E-mail: [email protected] http://www.aschulman.com Akzo Nobel Functional Chemicals BV PO Box 247 3800 AE Amersfoort Netherlands Tel: +31 3346 76767 Fax: +31 3346 76100 E-mail: [email protected] http://www.functionalchemicals.com Alcan Chemicals Europe 135 Aberdour Road Burntisland Fife Scotland KY3 0EP United Kingdom Tel: +44 (0) 1592 411000 Fax: +44 (0) 1592 411111 E-mail: [email protected] http://www.alcanchemicals.com Americhem Europe Limited Cawdor Street Eccles Manchester M30 0QF United Kingdom Tel: +44 (0) 1617 897832 Fax: +44 (0) 1617 877832 E-mail: [email protected] http://www.americhem.com

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Aquaspersions Limited Beacon Hill Road Halifax West Yorkshire HX3 6AQ United Kingdom Tel: +44 (0) 1422 386200 Fax: +44 (0) 1422 386239 E-mail: [email protected] http://www.aquaspersions.co.uk Areton International Plastics Limited Unit 47/48 Clywedog Road North Wrexham Industrial Estate Wrexham LL13 9XN United Kingdom Tel: +44 (0) 1978 664646 Fax: +44 (0) 1978 664647 E-mail: [email protected] http://www.areton.com Arto Chemicals Limited Arto House London Road Binfield Bracknell, Berkshire RG42 4BU United Kingdom Tel: +44 (0) 1344 860737 Fax: +44 (0) 1344 860820 E-mail: [email protected] Biesterfeld Plastic Benelux BV Oude Bosscheweg 15 5301 LAZaltbommel Netherlands Tel: +31 418 572315 Fax: +31 418 572370 E-mail: [email protected] http://www.biesterfeld-plastic.com Blagden Specialty Chemicals Limited Osprey House Black Eagle Square Westerham Kent TN16 1PA United Kingdom Tel: +44 (0) 1959 560805 Fax: +44 (0) 1959 565656 E-mail: [email protected]

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Borax Europe Limited 1A Guildford Business Park Guildford Surrey GU2 8XG United Kingdom Tel: +44 (0) 1483 242000 Fax: +44 (0) 1483 242001 E-mail: [email protected] http://www.borax.com Bromine & Chemicals Limited 201 Haverstock Hill London NW3 4QG United Kingdom Tel: +44 (0) 2074 317707 Fax: +44 (0) 2074 317797 Broste AB Kryptongatan 9B 431 53 Molndal Sweden Tel: +46 3174 64440 Fax: +46 3177 69676 E-mail: [email protected] http://www.broste.com Cairn International Limited Cairn House Elgiva Lane Chesham HP5 2JD United Kingdom Tel: +44 (0) 1494 786066 Fax: +44 (0) 1494 791816 E-mail: [email protected] http://www.cairninternational.co.uk Caldic Belgium Terlochtweg 1 Hemiksem 2620 Belgium Tel: +32 3 8704811 Fax: +32 3 8704859 http://www.caldic.com

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Campine SA Nijverheidsstraat 2 Beerse Antwerp 2340 Belgium Tel: +32 1460 1511 Fax: +32 1460 1577 http://www.campine.be Capital Rubber & Plastics Limited Units 9/11 Deans Factory Estate Lambs Lane Rainham Essex RM13 8XL United Kingdom Tel: +44 (0) 17085 52214 Fax: +44 (0) 17085 24004 http://www.capitalrubber.uk.com Ceepree Products Limited Springfield House Lower Eccleshill Road Darwen, Blackburn Lancashire BB3 0RP United Kingdom Tel: +44 1254 702800 Fax: +44 1254 873009 E-mail: [email protected] http://www.ceepree.com CH Erbsloeh KG Duesseldorfer Strasse 103 47809 Krefeld Germany Tel: +49 2151 52500 Fax: +49 2151 525100 E-mail: [email protected] http://www.cherbsloeh.de Charlotte Chemical Inc 2500 Wilcrest Suite 334 Houston Texas 77042 USA Tel: +1 52 5 203 6226 Fax: +1 52 5 203 6434 E-mail: [email protected] http://www.charlotte.com

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Clariant (Italia) SpA - Masterbatches Division Via Lainate 26 20010 Pogliano Milanese (MI) Italy Tel: +390 2 99187558 Fax: +390 2 99187552 http://www.clariant.masterbatches.com Collinda Limited Collinda House 25 Ottways Lane Ashtead Surrey KT21 2PL United Kingdom Tel: +44 (0) 1372 278416 Fax: +44 (0) 1372 278559 E-mail: [email protected] http://www.collinda.co.uk Colortek Farbsysteme GmbH Ringstrasse Gerwerbegebeit 1 19357 Karstadt Germany Tel: +49 38797 760 Fax: +49 38797 76200 E-mail: [email protected] http://www.colortek.de DSBG Eurobrom BV PO Box 158 2280 AD Rijswijk Netherlands Tel: +31 7034 08438 Fax: +31 7039 99035 E-mail: [email protected] http://www.dsbgfr.com Duslo AS PO Box 33 927 03 Šal'a Slovakia (Slovak Republic) Tel: +421 31 7753388 Fax: +421 31 7753018 E-mail: [email protected] http://www.duslo.sk

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Dyna-Grout Inc 24B Skidmore Road Deer Park NY 11729-7217 USA Tel: +1 631 242 3366 E-mail: [email protected] http://www.dynagrout.com E & E Limited Bramley Road Milton Keynes MK1 1PT United Kingdom Tel: +44 (0) 1908 271511 Fax: +44 (0) 1908 375611 E-mail: [email protected] E. Wood Limited Standard Way Northallerton North Yorkshire DL6 2XA United Kingdom Tel: +44 (0) 1609 780170 Fax: +44 (0) 1609 780438 E-mail: [email protected] Ferro Chemicals SA Etang de la Gafette BP 28 13521 Port-de-Bouc France Tel: +33 04 42 40 73 00 Fax: +33 04 42 40 73 33 http://www.ferro.com Gabriel-Chemie GmbH Industriestrasse 1 2352 Gumpoldskirchen Austria Tel: +43 2252 636300 Fax: +43 2252 63660 E-mail: [email protected] http://www.gabriel-chemie.com Gedriplastics NV Industriezone Peerderbaan 1419 B-3960 Bree Belgium Tel: +32 89 469760 Fax: +32 89 469766 E-mail: [email protected] http://www.gedriplastics.com

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Great Lakes Chemical Corporation Tenax Road Trafford Park Manchester M17 1WT United Kingdom Tel: +44 (0) 1618 722323 Fax: +44 (0) 1618 753177 E-mail: [email protected] http://www.pa.greatlakes.com Hardie Polymers Limited 53 Stockiemuir Avenue Bearsden Glasgow Scotland G61 3JJ United Kingdom Tel: +44 (0) 1419 423330 Fax: +44 (0) 1419 424001 E-mail: [email protected] http://www.hardie-polymers.co.uk Intermag Company Limited Bath Road Felling Industrial Estate Gateshead NE10 0LG United Kingdom Tel: +44 (0) 1914 382030 Fax: +44 (0) 1914 384717 E-mail: [email protected] Internatio BV Wilhelminaplein 32 3008 Rotterdam (AV) Netherlands Tel: +31 10 2908600 Fax: +31 10 2908611 E-mail: [email protected] http://www.internatio.nl Internatio NV Blarenberglaan 21 Industrieterrein Noord A 2800 Mechelen Belgium Tel: +32 1529 4950 Fax: +32 1529 4952 E-mail: [email protected] http://www.internatio.com

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Italmatch Chemicals SpA Via Pietro Chiesa 7/13 Torri Piane - San Benigno 16149 Genova Italy Tel: +390 10 642081 Fax: +390 10 4695296 E-mail: [email protected] http://www.italmatch.it Joseph Storey & Company Limited Heron Chemical Works Moor Lane Lancaster Lancashire LA1 1QQ United Kingdom Tel: +44 (0) 1524 63252 Fax: +44 (0) 1524 381805 E-mail: [email protected] http://www.josephstorey.co.uk KMZ Chemicals Limited 48 Station Road Stoke D'Abernon Cobham Surrey KT11 3BN United Kingdom Tel: +44 (0) 1932 866426 Fax: +44 (0) 1932 867099 E-mail: [email protected] Krahn Chemie GmbH Grimm 10 20457 Hamburg Germany Tel: +49 4032 092-0 Fax: +49 4032 092-297 E-mail: [email protected] http://www.krahn.de Laminopol Sp zoo Ul. Szczecinska 58 B 76200 Sł upsk Poland Tel: +48 59 8453463 Fax: +48 59 8452959 E-mail: [email protected] http://www.laminopol.com

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Martinswerk GmbH Kolner Strasse 110 50127 Bergheim Germany Tel: +49 2271 9020 Fax: +49 2271 902557 E-mail: [email protected] http://www.martinswerk.de Microfine Minerals Limited Raynesway Derby DE21 7BE United Kingdom Tel: +44 (0) 1332 673131 Fax: +44 (0) 1332 677590 E-mail: [email protected] http://www.microfine.co.uk National Chemical Company NCC House 42 Lower Leeson Street Dublin 2 Ireland Tel: +353 1 6131400 Fax: +353 1 6616676 E-mail: [email protected] http://www.ncc.ie Nexans CSPL UK Limited Tandy House Felixstowe Road Abbey Wood London SE2 9AA United Kingdom Tel: +44 (0) 2085 573481 Fax: +44 (0) 2085 573535 Nordmann, Rassmann GmbH Kajen 2 20459 Hamburg Germany Tel: +49 4036 870 Fax: +49 4036 87249 E-mail: [email protected] http://www.nrc.de Omnia Chemie GmbH Gorsenkothen 45 D-40882 Ratingen Germany Tel: +49 2102 81431 Fax: +49 2102 841253

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Omya Sas 35 Quai Andre Citroen 75015 Paris France Tel: +33 1 4058 4482 Fax: +33 1 4058 4469 http://www.omya.com Polyadd Limited 53A Denby Lane Codnor Ripley Derbyshire DE5 9SP United Kingdom Tel: +44 (0) 1773 570994 Fax: +44 (0) 1773 570994 E-mail: [email protected] http://www.polyadd.co.uk Produits Chimiques de Lucette ZI de la Vallee Verte 53940 Le Genest Saint Isle France Tel: +33 2 4301 2310 Fax: +33 2 4302 4906 http://www.pcdlucette.com PVC Technical Services P.O. Box 1377 Silver City New Mexico 88062 USA Tel: +1 505 534 9098 E-mail: [email protected] http://www.plasticsnet.com Rakem Limited Wellington Street Bury Manchester BL8 2BD United Kingdom Tel: +44 (0) 1617 620044 Fax: +44 (0) 1617 620033 E-mail: [email protected] http://www.rakem.co.uk

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Rhodia Consumer Specialties Limited PO Box 3 210-222 Hagley Road West Oldbury West Midlands B68 0NN United Kingdom Tel: +44 (0) 121 429 4942 Fax: +44 (0) 121 420 5151 http://www.albright-wilson.com Salmon & Cia Lda Rua Da Cova Da Moura 2-6º 1399-033 Lisboa Portugal Tel: +351 21 3920130 Fax: +351 21 3920189 E-mail: [email protected] Schill & Seilacher "Struktol" Aktiengesellschaft Moorfleeter Strasse 28 D-22113 Hamburg Germany Tel: +49 40 733620 Fax: +49 40 73362194 E-mail: [email protected] http://www.struktol.de Solvay Fluor und Derivate GmbH PO Box 220 30002 Hannover Germany Tel: +49 511 8572162 Fax: +49 511 817338 E-mail: [email protected] http://www.solvay-fluor.com Synergistic Polymer Systems PO Box 2116 Bellaire Texas 77402 -2116 USA Tel: +1 713 780 8888 Fax: +1 713 780 8887 E-mail: [email protected] Tolson Polymers BV Westblaak 194 3012 KN Rotterdam Netherlands Tel: +31 10 2141 918 Fax: +31 10 2420 800 E-mail: [email protected]

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Tropag GmbH Bundesstrasse 4 20146 Hamburg Germany Tel: +49 4041 4013-0 Fax: +49 4041 4013-20 E-mail: [email protected] http://www.tropag.com VAMP Srl Viale S. Boezio, 4-6 20145 Milano Italy Tel: +39 02 3492281 / 3490518 Fax: +39 02 33103681 E-mail: [email protected] http://www.paginegialle.it/vampsrl Vamp Tech SpA Viale delle Industrie 10/12 20040 Busnago (MI) Italy Tel: +390 39 6957821 Fax: +390 39 6820563 E-mail: [email protected] http://www.vamptech.com West & Senior Limited Milltown Street Radcliffe Manchester M26 1WE United Kingdom Tel: +44 (0) 1617 247131 Fax: +44 (0) 1617 249519 E-mail: [email protected] http://www.westsenior.co.uk Wilfrid Smith Limited Elm House Medlicott Close Corby Northamptonshire NN18 9NF United Kingdom Tel: +44 (0) 1536 460020 Fax: +44 (0) 1536 462400 E-mail: [email protected] http://www.wilfrid-smith.co.uk

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Abbreviations and Acronyms ABS AMAP AOM APC APME APP ATH ATO BAPP BCC BDBPT BDP BDPE BEO BET BFR BHPP BMI BPADP BSEF CFR CMHR CPSC CPVC CR CTI DAHP DCPD decaBDE DEEP DEMMP DKS DPE DSBG DTI E&E EBFRIP EBT EBTBP EEA EG EM EMA EPB EPDM EPS ETP EVA FHSA FIGRA FIPEC FMVSS

acrylonitrile-butadiene-styrene terpolymer Arctic Monitoring and Assessment Programme ammonium octamolybdate Arab Potash Company Association of Polymer Manufacturers in Europe ammonium polyphosphate alumina trihydrate antimony trioxide bis(4-aminophenyl) phenyl phosphate Business Communications Corporation bis(2,3-dibromo)propyl ether of TBBA bisphenol A bis(diphenyl phosphate) bromodiphenyl ether brominated epoxy oligomer specific surface area, Brunauer-Emmett-Teller method brominated flame retardant bis(3-dihydroxyphenyl) phenyl phosphate bismaleimide bisphenol A diphenylphosphate Bromine Science & Educational Forum chlorinated fire retardant combustion modified heat resistance Consumer Product Safety Commission chlorinated PVC chloroprene Comparative Tracking Index diammonium hydrogen phosphate dicyclopentadienol decabromo diphenylether diethyl ethyl phosphonate diethyl(methacryloxymethyl) phosphonate Dai-Ichi Kogyo Seiyaku diphenyl ether Dead Sea Bromine Group Department of Trade and Industry electrical and electronics European Brominated Flame Retardant Industry Panel ethylene bis(tetrabromophthalimide) ethylene bis(tetrabromophthalimide) ethylene-ethyl acrylate copolymer expandable graphite electromagnetic ethylene methyl acrylate ethane 1,2 bis (pentabromophenyl) ethylene-propylene-diene terpolymer expanded polystyrene engineering thermoplastic ethylene-vinyl acetate copolymer Federal Hazardous Substances Act fire growth rate Fire Performance of Electric Cables Federal Motor Vehicle Safety Standard

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FR FST FTIR GMA GRP GWFT HALS HB HBCD HDBP HDT HET HIPS HRR IEC IPP Jodico JV LCA LDPE LIFT LOI LPC LRT LSOH LUL MBEO MC MDH MFI MHC MMT MoD m-PPO MSW NBS NFPA NOR OBSi octaBDE ODOPB OI PA PAH PBB PBDE PBI PBO PBT pbw PC PCB PCB PE PEEK

146

flame retardant fire-smoke toxicity Fourier transform infrared glycidyl methacrylate glass reinforced plastic Glow Wire Flammability Test hindered amine light stabiliser horizontal burning hexabromocyclododecane hexahalogenated dimethylbipyrroles heat deflection temperature hexachloroendomethylenetetrahydrophthalic high impact polystyrene heat release rate International Electrical Commission Integrated Product Policy Jordan Dead Sea Industries joint venture life-cycle assessment low density polyethylene lateral ignition flame spread test limiting oxygen index Loss Prevention Council long-range transport low smoke zero halogen London Underground modified brominated epoxy oligomer melamine cyanurate magnesium hydroxide melt flow index magnesium hydroxycarbonate montmorillonite clay Ministry of Defence modified polyphenylene oxide municipal solid waste National Bureau of Standards National Fire Protection Association N-alkoxy hindered amines organoboroxo-siloxane octabromo diphenylether 2-(6-oxido-6H-dibenzo(c,e)(1,2)oxaphosphorin-6-yl)-1,4-benzenediol oxygen index polyamide polycyclic aromatic hydrocarbon polybrominated biphenyl polybrominated diphenyl ether polybenzimidazole polybenzoazole poly(butylene terephthalate) parts by weight polycarbonate polychlorinated biphenol printed circuit boards polyethylene polyetheretherketone

Flame Retardants for Plastics Market Report

pentaDBE PET PHA PHDD PMMA PON POP PP PPO PS PU PVA PVC R&D RDP RHR RoHS RTM SAN SBI SBS SEA SG SMC SMOGRA SPR TBBA TBBPA TCPP TDCP TGPSO THPS THR TIP TMCPP TPMP TPP TPU TS UL UNCSD UP UV WEEE XPS ZB ZHS

pentabromo diphenylether polyethylene terephthalate polyhydroxyamide polyhalogenated dibenzodioxins polymethyl methacrylate phosphorus oxynitride persistent organic pollutant polypropylene polyphenylene oxide polystyrene polyurethane polyvinyl alcohol polyvinyl chloride research & development resorcinol diphenyl phosphate rate of heat release Restriction of Hazardous Substances resin transfer moulding styrene-acrylonitrile polymer Single Burning Item styrene-butadiene-styrene specific effective area specific gravity sheet moulding compound smoke growth rate smoke production rate tetrabromobisphenol A tetrabromobisphenol A trichloropropylphosphate tris dichloropropyl phosphate triglycidyl phenyl silane oxide tetrakis hydroxymethyl phosphonium salts total heat release toxicity impact potential tris monochloropropyl phosphate cyclic diphosphonate ester triphenyl phosphate thermoplastic polyurethane thermally stable Underwriters’ Laboratories United Nations Commission on Sustainable Development unsaturated polyester ultraviolet Waste Electrical and Electronic Equipment Directive extruded polystyrene zinc borate zinc hydroxystannate

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ISBN: 1-85957-385-1

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