Ageing of Rubber - Accelerated Heat Ageing Test Results

Ageing of Rubber

Accelerated Heat Ageing Test Results

R.P. Brown, T. Butler and S.W. Hawley

Europe’s leading independent plastics and rubber specialists

Ageing of Rubber Accelerated Heat Ageing Test Results

R.P. Brown, T. Butler and S.W. Hawley Rapra Technology Limited

Acknowledgements This report is an output from the Weathering of Elastomers and Sealants project which forms part of the UK government’s Department of Trade and Industry’s Degradation of Materials in Aggressive Environments Programme. The authors are indebted to all those who contributed financially, with provision of materials, and by giving advice and support. We are particularly grateful to the members of the Industry Advisory Committee for all their help and guidance throughout the project: Alfa Laval Saunders Ltd., AWE, British Energy Generation Ltd., British Nuclear Fuels plc, Enichem UK Ltd., Hiflex Hose, Schlumberger Gas Metflex, Silvertown UK Ltd., Tun Abdul Razak Research Centre, and Wavin Building Products Ltd.

Rapra Technology Limited Shawbury, Shrewsbury, Shropshire SY4 NNR, United Kingdom Telephone: +44 (0)1939 250383 Fax: +44 (0)1939 251118 http://www.rapra.net

First Published 2001 by

Rapra Technology Limited Shawbury, Shropshire SY4 4NR, United Kingdom

© Copyright 2001 Rapra Technology Limited

ISBN: 1-85957-274-X

All rights reserved. Except as permitted under current legislation no part of this publication may be photocopied, reproduced or distributed in any form or by any means or stored in a retrieval system, without prior permission in writing from the copyright holder. The report is published in good faith, but on the basis that no responsibility or liability of any nature shall attach to Rapra Technology Limited arising out of or in connection with any utilisation in any form of any material contained herein.

Contents 1. Introduction ...................................................................................................................... 1 2. Materials .......................................................................................................................... 1 2.1 Original Materials ..................................................................................................... 1 2.2 New Materials ........................................................................................................... 2 3. Preparation of Test Pieces ................................................................................................. 3 4. Physical Tests .................................................................................................................... 3 5. Exposure of Test Pieces ..................................................................................................... 4 6. Results .............................................................................................................................. 4 6.1 Presentation ............................................................................................................... 4 6.2 Uncertainty ................................................................................................................ 5 6.3 Prediction of Natural Ageing ..................................................................................... 5 7. Discussion ......................................................................................................................... 8 7.1 Change with Time ...................................................................................................... 8 7.1.1 General ............................................................................................................. 8 7.1.2 Hardness .......................................................................................................... 9 7.1.3 Modulus ........................................................................................................... 9 7.1.4 Tensile Strength .............................................................................................. 10 7.1.5 Elongation at Break ........................................................................................ 10 7.1.6 DMTA ............................................................................................................ 10 7.1.7 Compression Set ............................................................................................. 11 7.2 Predictions ............................................................................................................... 12 7.2.1 General ........................................................................................................... 12 7.2.2 Hardness ........................................................................................................ 15 7.2.3 Modulus ......................................................................................................... 16 7.2.4 Tensile Strength .............................................................................................. 16 7.2.5 Elongation at Break ........................................................................................ 17 7.2.6 DMTA ............................................................................................................ 18 7.2.7 Compression Set ............................................................................................. 18 7.2.8 Choice of Analysis Method ............................................................................ 19 7.2.9 Effectiveness of the Predictions ....................................................................... 20 8. Conclusions .................................................................................................................... 21 References ........................................................................................................................... 22

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Appendix 1 - Compound Details ......................................................................................... 23 Appendix 2 - Accelerated Heat Ageing Results .................................................................... 35 Compound A - Natural Rubber - Standard .................................................................... 37 Compound B - Natural Rubber - Good Ageing .............................................................. 41 Compound C - Natural Rubber - Mineral Filler Loaded ................................................ 45 Compound D - Natural Rubber - Mineral Filler (Heavy Loaded) .................................. 49 Compound E - Styrene Butadiene Rubber - General Purpose ......................................... 53 Compound F - Styrene Butadiene Rubber - Good Ageing ............................................... 57 Compound G - Styrene Butadiene Rubber - General Purpose ......................................... 61 Compound H - Styrene Butadiene Rubber - Good Ageing .............................................. 65 Compound J - Butyl Rubber - General Purpose .............................................................. 69 Compound K - Butyl Rubber - Good Ageing .................................................................. 73 Compound L - Polychloroprene - General Purpose ........................................................ 77 Compound M - Polychloroprene - Natural Ageing ......................................................... 81 Compound N - Polychloroprene - Heat Ageing .............................................................. 85 Compound P - Nitrile Rubber - General Purpose ........................................................... 89 Compound R - Polychloroprene - Good Ageing ............................................................. 93 Compound S - Miscellaneous - Acrylate Rubber ............................................................ 97 Compound T - Miscellaneous - Chlorosulphonated Polyethylene ................................ 101 Compound W - Miscellaneous - Polysulphide Rubber .................................................. 105 Compound X - Miscellaneous - Silicone Rubber .......................................................... 109 New Compounds Compound N1 - FVMQ ............................................................................................... 113 Compound N2 - HNBR ............................................................................................... 117 Compound N3 - Epoxidised Natural ............................................................................ 121 Compound N4 - Chlorinated Polyethylene ................................................................... 125 Compound N5 - Fluorocarbon ..................................................................................... 129 Compound N6 - Exxpro ............................................................................................... 133 Compound N7 - Epichlorohydrin ................................................................................. 137 Compound N8 - EPDM ................................................................................................ 141 Compound N9 - EVA ................................................................................................... 145 Compound N10 - PU .................................................................................................... 149 Participants’ Compounds Compound P1 ............................................................................................................... 153 Compound P2 ............................................................................................................... 157 Compound P3 ............................................................................................................... 161

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Ageing of Rubber - Accelerated Heat Ageing Test Results

Compound P4 ............................................................................................................... 165 Compound P5 ............................................................................................................... 169 Compound P6 ............................................................................................................... 173 Compound P7 ............................................................................................................... 177 Compound P8 ............................................................................................................... 181 Compound P9 ............................................................................................................... 185 Compound P10 ............................................................................................................. 189 Appendix 3 - Compression Set Results .............................................................................. 193 Appendix 4 - Example Graphs .......................................................................................... 201

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Ageing of Rubber - Accelerated Heat Ageing Test Results

1 INTRODUCTION A long-term natural ageing programme was started in 1958 when 19 rubber compounds were exposed at 3 locations. The final sets of test pieces were withdrawn in 1998 giving a total of 40 years of natural ageing. The results of the physical tests carried out at intervals over the 40 years have been published [1]. The 19 compounds were re-mixed in 1999–2000 in order that accelerated ageing tests could be carried out for direct comparison with the results from natural ageing. A total of 20 new compounds were also mixed to represent polymers not available in 1958 and to reflect changes in compounding practice. Ten of these materials were formulations directly nominated by industry covering materials of current interest to particular companies. The 39 materials were subjected to accelerated heat ageing for a series of times and temperatures, artificial weathering and exposure to ozone. This report details the results of the accelerated heat ageing tests and their analysis for the prediction of changes after long-term natural ageing. The accelerated weathering and ozone test results have been published separately [2].

2 MATERIALS The test pieces used in the programme were produced from compounds with the formulations given in Appendix 1. For reasons of confidentiality the materials nominated by industry are only described by polymer type. As regards the original 19 materials it is perhaps surprising that compounding has changed relatively little and most of the formulations are relevant today. The new compounds formulated by Rapra, with advice from the project Industry Steering Group, were selected as being the more commercially important of the many polymers and compounding ingredients introduced since the start of the project in 1958.

2.1 Original Materials Natural rubber compound A was selected as it had been used at Rapra for many years as a standard material which loosely represented a tyre tread or high grade conveyor belt cover. Compound B has what became known as an efficient vulcanising system with no elemental sulphur, although the term had not then been coined. The third natural rubber compound (C) represents a fairly high rubber content non-black filled material. The last natural rubber compound (D) was requested by the electrical side of the industry as a highly loaded, low grade insulation material and was said to exhibit good ageing properties in the dark. Compounds E and F are styrene butadiene rubbers (SBR) corresponding to A and B whilst G and H are oil extended versions. Compounds J and K were referred to as general purpose and good ageing butyl compounds, respectively. They represent the extremes of polymer available, with high and low unsaturation, respectively. The three polychoroprene compounds came from the polymer supplier and were labelled general purpose (L), natural ageing (M) and heat ageing (N).

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The two nitrile compounds were suggested by the main UK supplier at the time to represent a general purpose material (P) and a good ageing formulation (R). The remaining compounds were also suggested by the relevant suppliers as general purpose materials. It is important to remember when considering the results obtained for these materials that the re-mixes will not be identical with the original compounds produced in 1958 and this can be expected to have significant effect on the correlation between natural and accelerated results. As well as unavoidable differences in the polymers and compounding ingredients there was no way of ensuring that the states of cure achieved were identical.

2.2 New Materials Compound N1 is a fluorosilicone based on LS 2380U. The hydrogenated nitrile material, compound N2, is a formulation to give heat resistance. Compound N3 is an epoxidised natural rubber with low black loading used in an acoustic application. The chlorinated polyethylene, compound N4, represents a formulation for hose tube and cover material. Compound N5 is a 70 IRHD fluorocarbon based material for seal applications. Compound N6 is an Exxpro material (isobutylene p-methylstyrene copolymer) described as general purpose. The epichlorohydrin material, compound N7 is also formulated for general purpose use. The sulphur cured ethylene propylene diene terpolymer (EPDM), compound N8, is a formulation typically used for radiator hose applications. Compound N9 is an ethylene vinyl acetate (EVA) cable sheathing material. Compound N10 is a general purpose millable polyurethane.

Compounds P1 – P10 are materials submitted by industry participants: Compound P1

ethylene propylene copolymer

Compound P2

siloxane cellular material

Compound P3

medium nitrile, carbon black filled with EV sulphur cure

Compound P4

nitrile, NF standard 0115/2

Compound P5

EPDM, NF standard 0115/1

Compound P6

Vamac G material, carbon black filled with a Diak/DOTG cure system

Compound P7

W type polychloroprene with small amount of SBR, carbon black filled, sulphur/metal oxide cure

Compound P8

natural rubber

Compound P9

thermoplastic rubber – Santoprene 101 55 V185 from AES

Compound P10

nitrile

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Ageing of Rubber - Accelerated Heat Ageing Test Results

3 PREPARATION OF TEST PIECES Batches of all 39 compounds were mixed. In most cases 2 batches were needed, which were blended. Standard 2 mm thick sheets and type A compression set buttons were produced by compression moulding. The cure times used in 1958 for the original materials could not be derived from measurements in a curemeter as these instruments were only in the experimental stage. Hence, they were derived from a programme of curing for various times and measuring physical properties. The cure times for the new materials were derived from measurements on a Monsanto rheometer. The cure conditions arrived at are given in Appendix 1.

4 PHYSICAL TESTS Ideally, the same physical tests as used in the natural ageing programme would have been used to monitor changes but the volume of work that would have entailed was prohibitive. Hence, the following properties were selected: • tensile strength, • elongation at break, • stress at 100% elongation, • stress at 300% elongation, • microhardness, • compression set, and • dynamic mechanical thermal analysis (DMTA). The first 6 properties listed correspond to properties monitored in the natural ageing programme. DMTA allows a large amount of dynamic property data to be generated very efficiently using small test pieces including tan δ (to relate to resilience), glass transition temperature Tg, and T2 and T10 to compare with the Gehman low temperature test results. Tests were carried out in general accordance with the current ISO methods [3-6]. For tensile properties, type 2 dumbbells were used, with 3 dumbbells being tested for each measurement point. For compression set, type A buttons were used with 2 buttons tested at each measurement point. Hardness measurements were made by taking 5 readings on one test piece. The dynamic measurements were made on a Polymer Laboratories DMTA apparatus using clamped single cantilever geometry (strip test pieces 10 mm wide, 25 mm long and 2 mm thick) under the following conditions: displacement amplitude 64 x 10-6 m peak to peak, frequency 1 Hz, temperature –80 °C to 80 °C, temperature ramp rate 3 °C/min. One test piece was used at each measurement point and 2 additional test pieces were available to check on repeatability.

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5 EXPOSURE OF TEST PIECES Test pieces were exposed in air exchange ovens complying with ISO 188 [7] for a series of times and temperatures. The temperatures used for a given material were selected bearing in mind the known heat resistance of the material and the limitation that the longest exposure (lowest temperature) would be 6 months. The temperatures are shown on the individual graphs of property change with time. For all properties except compression set, 5 batches of test pieces were prepared for each compound which allowed a maximum of five temperatures to be used. The plan was to aim for a minimum of 4 temperatures per material. Each batch consisted of 8 sets of 3 dumbbells, a piece of sheet for hardness measurements and 8 strips (10 mm wide and 150 mm long) for DMTA tests. Initially, 5 of the 8 sets were exposed at each selected temperature and the first set tested after 3 days. Further exposure times were then selected, adding sets of test pieces if necessary, with the aim of obtaining useful results at a minimum of 5 exposure times with the longest time yielding approximately a 50% change in properties. Test pieces were conditioned for a minimum of 16 hours at 23 °C prior to test. For compression set, 6 sets of 3 buttons were prepared for each compound, which would allow tests at 3 temperatures with two times at each temperature. (The original plan was for only 2 temperatures.) The times were somewhat arbitrarily chosen as 1 and 5 weeks. All compounds were tested at 23 °C and at 100 °C or 150 °C depending on the known heat resistance. The third temperature was selected after consideration of the results at the first two temperatures.

6 RESULTS 6.1 Presentation For properties other than compression set, the results for each property after artificial ageing were plotted as a function of exposure time. The tensile properties are the mean of results on 3 test pieces and the hardness result is the median of 5 readings. Initially, a line was constructed for each graph that passed through the points. For analysis of the data, the form of the curve drawn is not important as the Williams Landel Ferry (WLF) transform uses the data points and the parameters for the Arrhenius plot are extracted from the graphs manually, when the best fit can be estimated by eye. There are too many graphs to be reproduced in total but those for hardness, tensile strength, elongation at break and 100% modulus are given in Appendix 2 by material (there is no 100% modulus graph for material P2) with all temperatures for a given material/property on one graph. These are presented as the experimental points without any lines fitted. Predictions derived from Arrhenius and WLF analysis other than compression set have also been tabulated. The compression set results are tabulated in Appendix 3, Table 1 and two examples of the results displayed graphically are given for compounds N1 and N2 in Figures 1 and 2. Predictions were made from the compression set results by fitting a dose rate equation and these are tabulated in Appendix 3, Table 2 for 1 and 40 years at 23 °C.

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The results for natural ageing after 40 years for the original 19 compounds are included in the prediction tables for comparison. The results derived from the DMTA measurements were in many cases erratic and/or the changes were quite small and it was not considered useful to tabulate or show graphically the full results. However, Tg for compound A and tan δ for compounds M and A are shown in Appendix 4, Figures 1, 2 and 3.

6.2 Uncertainty In order to make a realistic assessment of the significance of the results it is necessary to make an estimation of the variability of the test results. An indication of variability is illustrated on the graphs by means of error bars. These were derived from standard deviations for repeatability taken mostly from precision statements in ASTM and ISO test method standards. The repeatability standard deviations were multiplied by 2 to give the 95% confidence intervals. It will be appreciated that these error bars simply give an idea of the degree of scatter which might generally be expected. The uncertainties in estimates made by extrapolation of the results are inevitably very large. Comment is made below on the validity and significance of predictions but no attempt at quantification of the uncertainties has been made.

6.3 Prediction of Natural Ageing Extrapolation of the accelerated results to longer times at lower temperatures was attempted by two approaches—the Arrhenius relation and the WLF equation—and compression set results analysed using a dose rate equation. These techniques are outlined below and are discussed in more detail in a guide to the assessment of the useful life of rubbers [8]. In this report, the predictions are made for change at 23 °C and 40 °C to equate to long-term natural ageing under temperate and hot dry conditions. For some applications, particularly with the more heat resistant polymers, it may be of greater interest to extrapolate to more elevated temperatures that are representative of service conditions. The reaction rate/temperature relationship can often be represented by the Arrhenius equation: −E

K(T) = Ae RT or

⎛ E ⎞ Log(K(T)) = B − ⎜ ⎟ ⎝ RT ⎠ where K(T) is the reaction rate, A and B are constants, E is the activation energy, R is the gas constant, and T is the absolute temperature. To enable Arrhenius plots to be constructed, a single measure to represent change with time at each temperature is derived from the graphs. Ideally, the single measure would describe the

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shape of the graph, most simply the slope of a straight line, but this is often not possible. The most common practice is to take the time for the property to change by a given amount, for example 50%, but in this work it would be more convenient if the change in a given time could be used to make comparison with the natural results easier. Unfortunately, this is not always feasible because of the differing timescales for property change at different temperatures. For the first 19 compounds, the measure used was the time to reach the change found in natural ageing after 40 years under hot dry conditions. The hot dry condition was selected as the higher temperature is nearer to accelerated ageing than temperate conditions and generally gives a larger change than temperate conditions. Hot wet conditions are least relevant to oven ageing. For the remaining compounds, the times to reach a convenient, but arbitrary, percentage change were used, which varied from compound to compound and from property to property. The log of the measure of change of property with time (reaction rate) was plotted against reciprocal of absolute temperature. Where this sensibly yielded a straight line, the best fit line was constructed by computer. The straight lines were extrapolated to give measures of the reaction rates at 23 °C and 40 °C. For the first 19 compounds these are expressed as the time to reach the level of change found after 40 years natural ageing under temperate and hot dry conditions. For the remaining compounds, they are expressed as the time to reach the end point chosen. These predictions are tabulated, with the activation energies, for each material in Appendix 2. The natural ageing results (where relevant) are included for comparison. Examples of the Arrhenius plots are given in Figures 4-7 in Appendix 4. It is important to appreciate that for the original materials only one end point was taken— the change after 40 years in hot dry conditions. This means that the Arrhenius predictions in both the 23 °C and 40 °C columns are for the time to reach that end point. When comparing the 23 °C predictions with natural ageing in temperate conditions, to a first approximation the predictions should be adjusted by the ratio of the change under temperate conditions to that under hot dry conditions. Similarly, when comparing the 40 °C predictions with natural ageing in hot dry conditions consideration should be given to the fact that the hot dry conditions averaged rather less than 40 °C and hence all the predictions should be on the low side in terms of number of years. An alternative to constructing the Arrhenius plot of log (K) against 1/T is to shift the plots of property against time along the time axis to construct a master curve. It is based on the principle of time and temperature superposition—a change in temperature being equivalent to a change in rate. Essentially, the method consists of gradually shifting plots of property against time determined at different temperatures to the plot at a selected reference temperature until the curves partially overlap. Hence, by successive shifts, a master curve at the reference temperature is obtained, for which the origin of the timescale is fixed by the origin of the isotherm actually determined at the reference temperature. Based on the same series of isotherms, the master curve naturally shifts towards the shortest times when the reference temperature is higher.

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This procedure has the important advantage that no particular measure of the reaction rate has to be chosen nor any form assumed for the change of property with time. However, the model can only be used if the curves have essentially the same form at different temperatures. Use was made of the WLF equation to perform time temperature superpositions: ⎛ a(T − T0 ) ⎞ log(aT ) = ⎜ ⎟ ⎝ b + (T − T0 ) ⎠

In this expression, aT is the shift factor of an isotherm determined at temperature T, in relation to the isotherm at the reference temperature T0, and a and b are two adjustable coefficients dependent upon the material. By definition, when T=T0 there is no shift to apply. The shifts were made using software developed for the purpose and the values of log(aT) plotted against the corresponding temperature values. Standard curve fitting techniques were used to determine the best fit for the WLF equation to give values of the constants a and b. There is a problem because of the inherent discontinuity in the WLF equation. The form of the equation is such that if, in the denominator, the best fit estimate for b is equal to T – T0 at a particular value of T, the expression for the shift factor reaches a discontinuity. The effect of this is that for certain compounds the extrapolated temperature, e.g., 23 °C, is in the critical region. This leads either to abnormally long times (millions of years or more) if the temperature was just above critical or abnormally short times (fractions of a second) if the temperature was just below the critical point. This was encountered in a few cases and in these circumstances a modified approach to the shift factor was used and the formal WLF equation abandoned. The shift factor concept was still used but for these situations an Arrhenius equation was fitted to the shift factor (not to log(aT)): aT = P exp(Q/RT) where P and Q are coefficients found by best fit calculation, R is the gas constant and T the absolute temperature in the normal Arrhenius fashion. This has the advantage that it has no discontinuities and so a smooth temperature transition is assured. Using the WLF equation, the master curve was shifted to 23 °C and 40 °C and predictions for the changes after 40 years made. In some cases, this required extrapolation of the master curve in time. These predictions are tabulated for each material with the natural ageing results (where relevant) in Appendix 2. Note that these results are expressed as change in property after 40 years rather than the time to reach a given change used for the Arrhenius predictions. Examples of the master curves are given in Figures 8-11 in Appendix 4. As for the Arrhenius predictions, when comparing the 40 °C predictions with natural ageing in hot dry conditions consideration should be given to the fact that the hot dry conditions averaged rather less than 40 °C and hence all the predictions should be on the high side in terms of percentage change. The predictions at 23 °C can be directly compared to the temperate natural results.

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The predicted changes in tan δ have been converted to change in resilience to allow better comparison with the natural ageing results. The relation used was: Resilience = exp(–π tan δ) x 100 The compression set (CS) results were analysed by fitting a dose rate relation: CS =

100 ⎛t⎞ 1+ ⎜ ⎟ ⎝ a⎠

b

where t is time and a and b are coefficients for a particular material. This relation is self limiting between 0 and 100 over the whole time range of 0 to infinity. With two values of compression set and two times, the best fit values for the coefficients can be found. Predictions were derived for the set after 1 and 40 years at 23 °C using the results obtained at 23 °C. These are given in Appendix 3, Table 2 with the natural ageing results under temperate conditions (where relevant).

7 DISCUSSION 7.1 Change with Time 7.1.1 General It is clear from the graphs in Appendix 2 that the directions and rates of change with time vary considerably depending on material and property. The shape of the change of property with time graph is not always consistent at all temperatures for a given material and property. It can also be seen that in a number of cases the form of change with time is relatively complex. Whilst apparent complex behaviour can sometimes be attributed to scatter of experimental points, in many of these cases there appears to be real changes of rate of change and even change of direction. Considering the original 19 compounds, this is in contrast to the naturally aged results where, although in many cases scatter was considerable, the form of change with time was generally thought to be relatively simple. It is highly probable that many instances of change of rate and direction in accelerated tests are due to different reactions occurring at different temperatures and to the severity of degradation produced at higher temperatures and longer times. This immediately confirms the generally held view that changes seen under high levels of acceleration are not necessarily representative of changes at normal ambient conditions. Further, such differences in behaviour are likely to be seen at the degree of acceleration needed to produce results in what would be generally considered to be a reasonable timescale. The implication for making predictions by extrapolation from accelerated tests is that the validity of the results may be very dependent on the measure of change taken to fit the predictive model, particularly its position along the time axis. It also indicates that longer exposures at lower temperatures than was possible in the timescale of this work are desirable.

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The actual rates of change of property with time in the accelerated tests are not sensibly contrasted to those from natural ageing from simple observation of the curves. This is simply because it is the rate at which the rates of change with time change with temperature (activation energy) that will largely determine predictions made to lower temperatures. When studying the graphs, note should be taken of the scale used so that the degree of scatter is put in perspective. Despite the care taken in the preparation of test pieces and the testing, it is apparent that the scatter is significant and it would have been advantageous if more data points and more test pieces could have been afforded.

7.1.2 Hardness Most of the hardness results showed a relatively simple form of change with hardness increasing with time, but there were notable exceptions. After natural ageing all materials had either increased or changed very little so overall there is a general correlation between natural and accelerated results. The natural rubber compounds A–D are examples of where the curves are more complicated. For compound B it is clear that hardness rises gently until at the two higher temperatures there is a drop followed by a sharp rise. This report will not generally attempt to relate the changes seen to reactions taking place but here it could reasonably be argued that reversion followed by embrittlement occurred at the higher temperatures. With the other 3 materials, a drop in hardness occurred very quickly except at the lowest temperature. Interestingly, the other natural rubber compound P8 showed simply a gentle rise in hardness. The butyl compounds J and K were the only ones consistently to show a decline in hardness (they changed very little on natural ageing). Acrylate S, ethylene propylene P1 and the thermoplastic elastomer P9 showed the tendency for a maximum and/or minimum followed by a steep rise, similar to the behaviour of compounds A–D. More complicated behaviour was also seen in the polysulphide W, the fluorocarbon N5, polyurethane N10 and the cellular material P2. Compound W is unusual in showing a sharp fall in hardness after an initial rise, although the rise becomes very small at the lowest temperature. It is likely that the behaviour of fluorocarbon N5 is due to experimental scatter. Materials N10 and P2 seem to have a change of the direction of change depending on temperature. Both compounds S and W changed little on natural ageing and the sharp fall found in accelerated tests for W must be due to a different mechanism.

7.1.3 Modulus Superficially at least, the 100% modulus curves are not dissimilar to those for hardness. Again there is some cyclic behaviour with the natural rubbers A–D, acrylate S, ethylene propylene P1 and the thermoplastic elastomer P9, and compounds W and N10 show complications. In some cases, the experimental scatter seems more evident than with hardness. Where the modulus results are missing for longer times it is simply because elongation had fallen below 100% (it did not reach 100% in the case of P2). There were no notable new phenomena in the 300% modulus results and there are rather fewer results because of materials breaking at lower elongations.

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7.1.4 Tensile Strength The scatter of results appears greater for tensile strength than for hardness making it more difficult in a number of cases to be certain of the trend. However, for the great majority of materials strength tended to fall. Only for Hypalon T, epichlorohydrin N7, and nitrile rubber P3 was the trend fairly clearly for a rise in strength. In the natural ageing results compounds S, T, W and X tended to rise but all the others either fell or changed little. In accelerated tests compound S did show an initial rise, compound X actually changed very little but compound W definitely fell. Hence, apart from compound W there was a general correlation between accelerated and natural results. Both polychloroprenes, M and N, and hydrogenated nitrile rubber N2 showed an upturn in strength at the highest temperature only, indicating the onset of a different mechanism. The nitrile P showed this at 90 °C and 100 °C but it was followed by a downturn in strength at 100 °C. The nitrile R had a somewhat curious scatter of results at 70 °C. There was indication of cyclic behaviour for the hydrogenated nitrile rubber N2, chlorinated polyethylene N4, nitrile rubber P4 and Vamac material P6. Compounds N2 and P6 appeared to have maxima, followed by a minimum in the case of compound P6. Compounds N4 and P4 possibly had minima. The tensile strength of compound N5 apparently changes direction falling slightly in strength at 150 °C then rising at 210 °C.

7.1.5 Elongation at Break The change in elongation curves, with very few exceptions, showed a downward trend with time. This was also the case for natural ageing. Hence, the pattern of change was quite consistent. However, there were many instances where the curves at different temperatures crossed so that there was inconsistency in terms of the trend with temperature. The butyl rubber J exhibited some odd behaviour but this was probably only at the higher temperatures. Elongation of polychloroprene L deteriorated very rapidly at longer times at the highest temperature. Acrylate S was a rare case where elongation tended to rise, although it appeared to go through a minimum first. There was possibly another change of direction at long times. Hypalon T fell in elongation initially but at longer times there was considerable scatter and the trend was a little uncertain. Rather curiously, the amount of initial fall seemed to be inversely related to temperature. The polysulphide W exhibits particularly complex behaviour and it is probable that the higher temperatures used were too severe. Significant change only appears at the highest temperature for the fluorocarbon N5.

7.1.6 DMTA The results from DMTA appeared to be subject to considerable scatter of experimental points giving rise to particularly large uncertainty. The general trend was for glass transition temperature to change little or rise with time of ageing. Silicone X was an exception in that the glass transition temperature tended to fall. Where the rise was considerable it occurred at longer times and at the higher temperatures.

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The results for compound A (Appendix 4, Figure 1) illustrate this and reference to the tensile strength and hardness graphs suggests that large rises in Tg occur after the material is quite severely degraded. The same general trend, as expected, was seen for T2 and T10 temperatures with most materials showing little change or a rise with time for these properties. T2 decreased at longer times for compound P6 and there were unexplained drops in T2 for materials N4 and P9 at the longest time at particular temperatures. These three materials showed similar behaviour for T10 temperature. No sensible results were obtained for P2. The natural ageing results for T2 and T10 values were also subject to large scatter and it was concluded that in many cases the changes were not significant. Cases of falling T2 or T10 values in natural ageing were not reflected in the accelerated results. Interestingly, the correlation between T2 and T10 was probably better for the accelerated results than for the natural ageing. Considering the scatter of results, for most materials tan δ could be said to show little change. An example is shown for compound M (Appendix 4, Figure 2). Where there was significant change there were some cases of a rise and some, but less, cases of a fall. Changes in resilience for the natural ageing were also found to be generally fairly modest. Where appreciable rise or fall was recorded on natural ageing there was an inverse general correlation with the direction of change found in the accelerated tests. This should be expected as tan δ decreases as resilience increases, and at the tan δ = 0.2 level a change of 0.01 is equivalent to about 6% resilience. The absolute values of tan δ and resilience are unlikely to correlate well as they are obtained at two different frequencies. The results for compound A (Appendix 4, Figure 3) show that a large increase in tan δ probably occurs only after quite severe degradation and at the lowest temperature there is some evidence that there is first a decrease in tan δ.

7.1.7 Compression Set Not surprisingly, in all cases compression set increased with time of exposure and with increasing temperature. Hence, the direction of change shows complete correlation between natural and accelerated exposure. Some of the rates of increase with time at 23 °C are small and there was no change with the polysulphide W at the highest temperature as it reached 100% set in the shorter time. The test pieces of fluorocarbon N5 crumbled on removal from the jigs at 140 °C and 200 °C (the highest temperatures used). The most plausible explanation is that local breaking strains at the elevated temperature were exceeded, possibly in combination with incomplete knitting of a rolled blank. The two examples of the compression set results presented graphically in Figures 1 and 2, Appendix 3 (for compounds N1 and N2, respectively) illustrate how the rate of change with time will vary for different materials and for different temperatures. As set approaches 100% the rate of change with time will become smaller because of the asymptotic nature of set curves.

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7.2 Predictions 7.2.1 General The predictions obtained by WLF and Arrhenius analysis are presented by material in Appendix 2, blank cells indicating where it was not possible to obtain a prediction or, in the case of 300% modulus, where there were no (or insufficient) results. The quality of the WLF master curves and the Arrhenius plots varied considerably. A good WLF master curve is where the transforms fit smoothly and for Arrhenius plots, the best appear as a perfect straight line. By way of illustration, the Arrhenius plot for elongation at break of compound G is given in Appendix 4, Figure 4, which is a good example and, in Appendix 4, Figure 5, the Arrhenius plot for elongation at break of compound N9 which is rather less good. The very respectable WLF master curve for elongation at break of compound M at 40 °C is given in Appendix 4, Figure 8, and the unsatisfactory WLF master curve for elongation at break of compound K at 23 °C in Appendix 4, Figure 9. Where the WLF master curve was particularly bad and essentially a scatter diagram or the Arrhenius plot was far from a straight line no prediction could be made. However, there was apparently not good correlation between relatively poor WLF or Arrhenius plots and wrong or unreasonable predictions, nor between particularly good plots and good predictions. This is probably because poor predictions are more related to the shapes and direction of the property-time curves at elevated temperatures. Considering first the original 19 materials and the results for hardness and tensile properties, predictions were obtained using the WLF equation for about 95% of the cases (property and material) but using the Arrhenius relation a prediction was only obtained in about 75% of the cases. Where no prediction was obtained by WLF theory it was because the data did not yield a sensible fit to the transform. No prediction was obtained using the Arrhenius relation when either there was no sensible change in the property with time at the various temperatures or the heat ageing results showed a change in the opposite direction to natural ageing. It is largely because of the latter point that there are fewer predictions using the Arrhenius relation than when using WLF theory. In over 85% of the predictions made using WLF theory, the change predicted was in the same direction as that seen in natural ageing. Because of the end point chosen, all the predictions obtained using the Arrhenius relation were in the same direction as seen in natural ageing. Hence, ignoring magnitude, predictions from the accelerated tests are apparently showing the same trend as natural ageing in over 80% of cases using WLF theory and over 75% using the Arrhenius relation. In about 60% of the cases where the WLF prediction was in the wrong direction a prediction was not obtained using the Arrhenius relation. Hence, there is a relatively small but significant number of cases where there is disagreement between the two approaches. This can doubtless be related to the choice of end point with the Arrhenius approach (where a different end point could result in the prediction changing direction) and the use of all the data with WLF theory. This in turn is related to cases where the change of property with time changes direction. A prediction being in the right direction is perhaps more significant than how near it is in magnitude to the change seen in natural ageing. If the correct trend is predicted it gives some

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Ageing of Rubber - Accelerated Heat Ageing Test Results

confidence that accelerated tests were a valid approach. The degree of extrapolation being applied to these results is so large that the uncertainty in magnitude of the predictions is such that a result within 50% of that realised in natural ageing would be considered good. The magnitude, and in some cases the direction, of change predicted by the Arrhenius relation can be changed by choosing a different end point. The magnitude can also be changed by ignoring results at one or more of the test temperatures. The magnitude of change predicted by WLF theory is subject to the interpretation of the master curve and can also be changed by ignoring a temperature. It will be appreciated that to make numerous analyses of all the data in this study would constitute a prohibitive volume of work for one report. However, in many cases there is scope for more detailed study of particular material/property combinations using different criteria from the ageing curves as input. As a simple illustration of possible alternatives, further analysis of the hardness changes of two compounds by the Arrhenius and WLF relations has been made. As can be seen from the plots of the hardness results for compounds B and R (given in Appendix 2), compound B showed relatively complicated behaviour with the shape of the hardness–time plot changing with temperature, whilst compound R showed relatively consistent increase of hardness with time. This is reflected in the WLF master curves (Appendix 4, Figures 10 and 11) where compound R gives a much smoother fit than compound B. The best predictions from these for change in hardness after 40 years at 40 °C are 49% for compound B and 82% for compound R. After long-term exposure in a hot dry climate (not averaging as high as 40 °C) these materials actually changed by 24% and 55%, respectively. Arrhenius plots were constructed with the end point taken as 24% and 55% (which required judicious extrapolation for some curves) and are shown in Appendix 4, Figures 7 and 8, respectively. These yielded predictions of 7 years and 6 years at 40 °C for compounds B and R, respectively, and 24 years and 16 years at 23 °C. Considering the shapes of the hardness–time curves for compound B, this end point would be difficult to justify and it is perhaps remarkable that sensible predictions were obtained. The Arrhenius plot for compound B in particular is clearly not a perfect straight line. If the 70 °C point is ignored the prediction becomes 21 years at 40 °C and 124 years at 23 °C, whilst if the 100 °C point is ignored these figures are 3.5 years and 9 years, respectively. This is not the direction one would expect and is probably an artifact of the end point used. The effect of ignoring points for compound R is less drastic, reflecting the better straight line seen in the Arrhenius plot. The corresponding figures are 6 years and 17 years ignoring the 70 °C point and 4.5 years and 11 years ignoring the 100 °C point. Had it not been for an interest in making direct comparisons with long-term exposures, it would be sensible to have chosen rather lower end points. If an end point of 10% is taken for compound B the scatter on the Arrhenius plot is increased and the predictions are 1.5 years at 40 °C and 4 years at 23 °C for a 10% change. However, if the 100 °C point is ignored these become 5 years at 40 °C and 35 years at 23 °C. With linear extrapolation this is equivalent to 12 years and 84 years to reach 24% change at 40 °C and 23 °C, respectively.

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Taking an end point of 20% for compound R also increases the scatter on the Arrhenius plot and yields predictions of 2 years at 40 °C and 9 years at 23 °C. Ignoring the 100 °C point yields 3.5 years at 40 °C and 20 years at 23 °C. With linear extrapolation this is equivalent to 10 years and 55 years to reach 55% change at 40 °C and 23 °C, respectively. Where the Arrhenius plot is not linear there is justification in ignoring the highest temperature as not being representative of reactions at lower temperatures. With this selective use of the data very reasonable predictions in comparison to natural exposure could be obtained. All the predictions in these examples showed the same trend as in natural exposure but tended to overestimate the rate of change. Considering the uncertainty in actual temperature on natural exposure, the WLF predictions could be said to be good for both compounds, in spite of the shapes of the property-time curves for compound B. With selective use of the data, good predictions were obtained for both compounds by the Arrhenius approach. In considering any of the predictions obtained for the original 19 materials it should be remembered that the accelerated tests were carried out on re-mixes which will not be identical with the original compounds mixed 40 years previously. Considering hardness and tensile properties for the new compounds, predictions could not be obtained in about 6% of cases. This is rather less than for the original materials but, remembering that there were no restrictions on the choice of end point for Arrhenius, is probably not significant. There are of course no natural ageing results for these materials so taking these predictions to be valid is an act of faith. Judging from the results for the original 19 materials it might be postulated that the odds would be on less than 15% being totally wrong, but that is pure conjecture. Of course, the same situation applies to these results as to those for the original materials and by making alternative analyses, for example with different end points, different predictions could be obtained. The choice of end points for the predictions given were somewhat arbitrary and not restricted by needing comparison with natural ageing. Taking a broad view of the comparison between the Arrhenius and WLF approaches there is complete conflict in the direction of the predictions in about 5% of cases. As noted in sections 6.1 and 7.1.6, the results derived from the DMTA measurements were rather less satisfactory than for hardness and tensile properties. In consequence, the predictions made are subject to even more uncertainty. Predictions were obtained in only 32% of cases and a number of these would appear highly suspect. The problem is a combination of the degree of change being relatively small in the majority of cases and the degree of scatter in the results. The magnitude of the predicted changes in comparison to natural ageing is considered property by property below. For the original 19 compounds the WLF predictions are directly comparable with natural ageing as they are given in percentage change after 40 years. A direct comparison of the magnitude of change predicted by Arrhenius with natural ageing is not possible because of the restrictions of the analysis. Hence it is necessary to compare the changes that occurred in 40 years with predictions of the number of years to produce the same change. As pointed out in section 6.3, it is important to note that the Arrhenius predictions in years are the times to reach the degree of change that were found after 40 years natural ageing in

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the hot dry climate. Hence, taking the hardness of compound A in Appendix 2, as an example, the Arrhenius predictions are for a change of 7.6% (i.e., the change found for natural ageing after 40 years under hot dry conditions). It is also important to remember when comparing the 40 °C predictions from both the Arrhenius and WLF approaches with natural exposure under hot dry conditions that the average temperature in the natural exposures was rather less than 40 °C. The Arrhenius analysis yields figures for the activation energy which is a measure of the rate of change of the reaction rate (or end point) with temperature. The activation energies obtained vary over a very large range and it is highly probable that they reflect the uncertainty of the data. In a few cases (in addition to those where no Arrhenius predictions were obtained) no activation energy is tabulated because it was clear that the calculated value was largely a product of noise in the data. Figures found in the literature generally range between 70 kJ and 120 kJ so the lower energies predicted in some cases could be considered unrealistic. However, it is interesting that low predicted activation energies did not correlate with particularly poor estimates of change of properties.

7.2.2 Hardness Considering the original 19 materials, predictions were obtained in all cases using WLF theory. There were 3 instances where no prediction was obtained using the Arrhenius relation: compounds J, K and T. For compound J there could not be a prediction as there was no change on natural ageing, for compound K change was too little at two of the temperatures, and for compound T there was very little change on natural ageing. For compounds C, D, K and W there were WLF predictions in the wrong direction. It is obvious that for compounds C and D the drop followed by a rise in hardness accounts for the difference between the 23 °C and 40 °C predictions. For compound K there was little change at 3 temperatures and an excessive drop in hardness at the highest temperature and a prediction is not really sensible. For compound W the rates of change at the highest 3 temperatures were clearly excessive. In the great majority of cases WLF theory overpredicts the degree of change by a factor of 2 or more. For materials J, N and S the predictions can be considered remarkably accurate. In just two cases, compounds L and X, does the prediction underestimate the change although the difference is certainly within the uncertainty band. The Arrhenius approach also overestimates the degree of change, or rather underestimates the time for the change, in most cases. For materials C, D and P the predictions overestimate the time for change at 23 °C. For compound E the predicted time at 23 °C is remarkably accurate. For compounds S and X the times for change are overestimated for both 23 °C and 40 °C. It is interesting that the Arrhenius approach has in a few cases underpredicted the time at 40 °C but overpredicted the time at 23 °C. In this context, it should be noted that for both the WLF and Arrhenius approach the hot dry climate of the natural exposures has been approximated as 40 °C whereas in fact it was probably less than this. The temperate climate was very close to 23 °C. For the new compounds predictions were obtained using both the WLF and Arrhenius approaches in all cases except one; no prediction was obtained for compound P2 using the

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Arrhenius approach. For two compounds, N10 and P1, there is conflict as to the direction of change predicted by the 2 approaches. This can be attributed to the change in hardness changing direction with time and in the case of N10 to the WLF fit being very poor. There are several cases where the WLF and Arrhenius predictions are in the same direction but differ in magnitude by a very large margin, the more obvious being N2, N4, P5, P6, and P9 where the times predicted by the Arrhenius relation are very long.

7.2.3 Modulus For the original 19 materials predictions were obtained using WLF theory in all possible cases except for compounds A and X at 100% and compound T at 300%. Arrhenius predictions were not obtained for compounds J, K, S, T, W and X at 100%. At 300%, predictions were only obtained for materials B, C, F and H. For compounds A and X the changes in 100% modulus were very small. For compound T there were few results for 300%. The lack of Arrhenius predictions is largely because of the conflicting direction of change in natural and accelerated tests and changes in direction for accelerated ageing, but scatter of results is also a factor. It is interesting that modulus appears to be a far less reliable property for obtaining predictions than hardness. The WLF predictions were in the wrong direction for 100% modulus of compounds K and W at 40 °C, probably because of the accelerated results changing direction with time. The same applies to compound D at 300%. The 300% modulus predictions were also in the wrong direction for compounds A, C, G and N. For compounds A and C changing direction in accelerated tests was again apparent but for compounds G and N the natural and accelerated results are simply different. As for hardness, WLF theory overestimates the degree of change in the great majority of cases but there are several underestimates for one of the two temperatures and several cases where the predictions match the natural results quite well. With the exceptions of compounds C and X, the Arrhenius predictions underestimate the time for change and the predictions for compounds M and N at 23 °C are very near to the natural results. For the new compounds, predictions were obtained in all possible cases except from WLF theory for 100% modulus of compounds N5 and P5 and 300% modulus of P1, and from the Arrhenius relation for 100% modulus of compounds N5, N6 and P9 and for 300% modulus of compounds P1 and P9. There are no conflicts between the two approaches, and although WLF theory predicts no change for compound P6, the Arrhenius prediction is for a very long time to see appreciable change. However, there are again cases of WLF and Arrhenius predictions differing in magnitude by a large margin.

7.2.4 Tensile Strength For the 19 original materials, tensile strength predictions were not obtained by WLF theory for compounds K, M and R and by the Arrhenius relation for compounds J, K, L, P, S, T, W and X. These cases are associated with either a small change on natural ageing, small changes from accelerated ageing, anomalous behaviour or too great an extrapolation needed from the WLF master curve.

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WLF predictions were in the wrong direction for compounds J, N, S and W although for compound J the differences were fairly small. The changes on natural ageing for compound X were also quite small and the prediction was for no change. Again, WLF theory overestimated the change in almost all cases although the predictions for compounds L and P were very near to the natural results and the prediction for compound C was an underestimate. Underestimates of the time for change were again obtained from the Arrhenius predictions in most cases but overestimates were given for compounds C and E whilst the estimates for compounds A, B and G at 23 °C were very near to the natural ageing results. For the new compounds, predictions were obtained by WLF theory in all cases except materials N5, P2 and P6 and by the Arrhenius relation in all cases except compounds N5, N8, N9, P2 and P6. The trend with time for compound N5 changed with temperature and there was also evidence of this with compounds P2 and N9. Compounds P6 and N8 showed a large degree of scatter. There is conflict as to the direction of change with compounds P1, P4 and P10 at 40 °C, which is probably associated with change in strength changing direction with time. With compounds N1, N7 and P5, WLF theory predicts no change whilst the Arrhenius approach predicts a fairly modest increase in strength. In these cases there are also changes in direction of change in strength. Once again there are cases of WLF and Arrhenius predictions differing in magnitude by a very large margin.

7.2.5 Elongation at Break Considering the original 19 compounds, predictions were obtained in all cases using WLF theory except for material R, whilst no predictions were obtained using the Arrhenius relation for compounds K, L, S, T and W. The change of elongation for compound R was very rapid at all except the lowest temperature. The changes on natural ageing were small for compounds K, L and S. The accelerated results for compound K were somewhat scattered, compound L changed very little, there were changes of direction with temperature for compound S, changes of direction with time for compound T and changes with both temperature and time for compound W. The two approaches did not agree on the direction of change for compounds W, J and K at 40 °C. For compound X, WLF theory predicted no change at 23 °C but on natural ageing compound X showed a small rise in elongation. The Arrhenius relation predicted that compound X would have a large drop in elongation. The disagreement for compound W can probably be attributed to the change of direction with time and temperature and for compounds J and K to scatter and change of direction with time. The disagreement for compound X illustrates the effect of a relatively modest swing from a positive to a negative change of direction. Yet again, WLF theory overestimated the change in the great majority of cases with only compounds C and N resulting in underestimates. The predictions for compounds S, E and M at 23 °C were close to the natural results. The Arrhenius predictions are almost all underestimates of the time for the change but the prediction for compound G is an overestimate at 23 °C. The predictions that best match the natural results at 23 °C are for compounds R, N, E and C.

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The only cases where no predictions were obtained for the new compounds were for P9 using WLF theory and for compounds N5 and P2 using the Arrhenius relation. The WLF master curve for compound P9 resembles a scatter diagram. There was some change of direction with time and temperature for compound N5 and little change in elongation for compound P2. There were no disagreements of direction of change between the 2 approaches. For material P6, WLF theory predicted no change but the Arrhenius relation predicted thousands of years for a 25% change. The same situation applied to elongation as to the other properties in that there were some large differences in magnitude between WLF and Arrhenius predictions.

7.2.6 DMTA Predictions for the DMTA parameters were generally only obtained in 25–50% of the cases although almost 75% were obtained for T2 using the Arrhenius relation. Although only of the order of 15% of the cases where WLF predictions were obtained were in the wrong direction compared to natural ageing, there were very few where the prediction was reasonable. This could said to be the case for T2 of compounds C and W at 23 °C, T10 of compounds E at 23 °C, T10 of K, and resilience of G and F. There were a similar number of reasonable predictions using the Arrhenius approach. It is concluded that the reproducibility of these DMTA parameters is too poor for them to be effective for this type of long-term prediction and the situation is not helped by the changes in natural ageing being small for most of the parameters. Some of the Arrhenius plots obtained were clearly unsatisfactory but many of them appeared to be quite reasonable and did not immediately indicate that predictions would be poor. It was clear that almost all of the WLF master curves showed far from perfect fit of the transforms which would indicate that predictions were likely to be unreliable. However, the best fits did not correlate with the cases where reasonable predictions were obtained.

7.2.7 Compression Set The predictions for compression set are always in the right direction. As can be seen from Appendix 3, Table 2 the magnitude of predictions for set after 40 years is always smaller than was found in natural ageing under temperate conditions. The predictions for set after 1 year are also lower than natural ageing for most compounds but in 3 cases, compounds F, H and N, the predictions are larger. The two values are similar for compound K. There is little correlation in terms of ranking of materials between the predictions and natural ageing after 40 years but, with the exception of compounds F, H, N and K, there is quite reasonable correlation after 1 year. As only two times of exposure were used, perhaps it would be surprising if the results had been any better. If measurements were made at several times and for up to 6 months as for the other properties it is likely that much better extrapolations could be obtained for set behaviour. However, it is curious that all the predictions at 40 years and the great majority at 1 year are low, which cannot reasonably be attributed to differences between the original materials and the re-mixes. Three possibilities are suggested. Chemical ageing could play a significant part after 40 years, although this does not explain the bias to low results after 1 year. It would, however, affect the correlation between predictions and natural ageing. The rate of recovery may be proportional to exposure time and hence higher set would be recorded at longer times using the standard 30 minute recovery period. It is also possible that the difference in test piece

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dimensions between the natural and accelerated ageing samples is significant (a special annulus test piece was used in the natural exposures). The predictions in this table were obtained using the results at 23 °C only. Including the data at elevated temperatures gave a worse fit to the dose rate relation. If there had been more time points it might be that using all temperatures would be advantageous. It can also be noted that the results do not support the idea that single point compression set data obtained at elevated temperature will correlate with longer term performance at ambient temperature. For example, the data obtained for 1 week at 70 °C is roughly split 50% either side of the natural results after one year.

7.2.8 Choice of Analysis Method Since there are the two techniques available for estimating the change in property that will result at a time or temperature other than those experimentally chosen, the question arises as to which is the better. Both techniques have certain advantages and drawbacks. The WLF approach relies on the validity of the time-temperature superposition principle whilst the Arrhenius approach is dependent on the validity of the assumption that increasing temperature merely increases the rates of change and does not introduce new types of change. Neither of these is likely to be completely true in all cases, primarily because there will be different reactions taking place at different temperatures. The WLF approach provides a master curve that encapsulates the whole of the accumulated data and therefore potentially provides the greatest information. The Arrhenius approach on the other hand usually disregards the bulk of the data gathered being limited to a specific end point, which may have been arbitrarily chosen. If it is possible to use all the data at each temperature to obtain a reaction rate then this disadvantage of the Arrhenius approach would disappear. Although the Arrhenius approach is mathematically simpler, with computer help the WLF approach is practically easier to use because of there being no need to specify a measure of reaction rate nor to make any assumptions when interpolating between points. The WLF approach is also more versatile in that it is relatively easy to produce predictions in terms of time to reach an end point and as change in a given time. With the Arrhenius approach this necessitates re-doing the calculation completely with a different measure of reaction rate. It does not appear that one of the methods consistently gives better correlation with natural ageing results. Where the change of property with time is uncomplicated and consistent, very similar results can be expected from the two approaches. The problems arrive when the change of property with time is complex, for example if it first falls and then rises. It was seen several times in this work that the WLF approach in taking all the data may produce a prediction which is dominated by one part of the ageing curves. Sometimes intuition suggests that this is giving an invalid prediction. With the Arrhenius approach it is necessary to make a choice of which part of the curve will be used and the validity of the prediction will then be dependent on whether that choice was correct.

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When a WLF master curve is generated the timescale it spans depends on the timescale of the ageing tests and on the activation energy. In some cases it is necessary to extrapolate the master curve to the time of interest which increases uncertainty. If the extrapolation needed is unreasonably large no prediction can be obtained from what appears to be perfectly good raw data. Both methods will indicate if results at one temperature are out of line with the others (for example because of a different reaction taking place). With Arrhenius the plot will be curved for the Arrhenius approach and using the WLF approach the poor fit to the master curve will be obvious. One conclusion is that more time should be spent than was possible for this report on studying the data in each case and that several analyses should be made, using all and parts of the data. Alternatively, if you are certain that all the data is relevant and valid then the WLF approach is usually the better choice, whereas if it is believed that part of the data is more valid than the rest then the Arrhenius approach is more appropriate.

7.2.9 Effectiveness of the Predictions Without restrictions on the end point used, predictions for hardness and tensile stress-strain properties were obtainable in over 90% of exposure trials. There was some variation between the different parameters with hardness being most successful and 300% modulus least successful. For DMTA parameters there was a much lower success rate for obtaining predictions. The differences between the properties being considered is largely attributable to differences in their repeatability and reproducibility but is also affected by the magnitude of the changes seen and the shapes of the plots of change of property with time. There are obviously least problems with relatively large changes in property and low degrees of scatter. The ease of obtaining a prediction also varies with material where, apart from differences in variability, the main factor is the shapes of the plots of change of property with time. It is one thing to obtain a prediction but quite another to obtain a valid or reliable prediction. In this work, the success rate in terms of predicting the same direction of change as seen in natural ageing was good for the hardness and tensile properties. In most of the cases where the direction was wrongly predicted it was possible to see how this could arise because of some complexity in the property-time curves. The predictions for the DMTA parameters were far less good but it was possible in most cases to see the probable causes of difficulty associated with scatter of results, magnitude of the changes and the shapes of the property-time curves. Compression set was shown to be a special case in that the direction of change and the general form of the compression set-time curve are always correctly predicted. Relatively few compression set results were obtained in this work and the predictions made from them always underestimated the long-term set found in natural ageing. However, the results raised optimism that if a quantity of results comparable with that obtained for the other properties were to be obtained good predictions could result. For the hardness and tensile properties, where the direction of change was correctly predicted, the majority of predictions overestimated the degree of change. The reasons for this are not entirely clear but are doubtless connected with changes in reaction rate and shape of the propertytime curve with temperature.

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In all cases where the property-time curve changes in shape or direction, either with time or with temperature, the choice of ageing temperature and the measure of change used will be critical. The analysis in this report only scratched at the surface of what could be done with the mass of data collected by taking different measures of change and rejecting parts of the data. With different analysis it is likely that some predictions could be improved. It was also very evident that, despite the size of the programme and the care taken, it really needed more temperatures, more time points and more test pieces to be used to reduce uncertainty. In particular, there were many cases when testing at lower temperatures and for longer times was highly desirable, confirming the view that successful accelerated testing will inevitably be very costly in time and effort. The main conclusion from the work is that accelerated ageing to predict performance at longer times is certainly not all good but is by no means all bad. The results obtained here may be disappointing in some respects but are also encouraging in that with sufficient time and effort it seems likely that very useful predictions could be obtained in most cases. Conversely, the results show that if the times and temperatures used are inadequate and/or the experimental uncertainty is too high then there is a high chance of obtaining poor predictions.

8 CONCLUSIONS An accelerated heat ageing programme involving a total of 39 rubber compounds has been successfully completed. The results showed that in many cases the curve of property change with time was complex indicating that reactions occurred which were not present in natural ageing. For hardness and tensile stress-strain properties, predictions (sensible or otherwise) of change at ambient temperatures could be made in 90% of the cases using WLF and Arrhenius relations, but the use of DMTA parameters was far less successful. A significant number of predictions were in conflict with the results of natural ageing. Where the direction of change was correctly predicted the predictions overestimated the degree of change in most cases. For compression set, the direction and general form of the change with time could always be correctly predicted but with the limited results obtained in this programme the set after long times was underestimated. There is considerable scope for more extensive analysis of the data generated by taking different measures of change and rejecting parts of the data. To reliably obtain useful predictions from accelerated test requires the use of more temperatures and data points than were possible in this work, in particular testing for longer times at lower temperatures.

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REFERENCES 1. R.P. Brown and T. Butler, Natural Ageing of Rubber—Changes in Physical Properties over 40 Years, Rapra Technology Limited, 2000. 2. R.P. Brown, T. Butler and S.W. Hawley, Ageing of Rubber—Accelerated Weathering and Ozone Test Results, Rapra Technology Limited, 2001. 3. ISO 37 1994 Rubber, vulcanised or thermoplastic—Determination of tensile stress-strain properties. 4. ISO 48 1994 Rubber, vulcanised or thermoplastic—Determination of hardness. 5. ISO 815 1991 Rubber, vulcanised or thermoplastic—Determination of compression set at ambient, elevated or low temperatures 6. ISO 4664 1998 Rubber—Determination of dynamic properties of vulcanisates for classification purposes (by forced sinusoidal shear strain). 7. ISO 188 1998 Rubber, vulcanised—Accelerated ageing or heat resistance tests. 8. R.P. Brown, Practical Guide to the Assessment of the Useful Life of Rubbers, Rapra Technology Limited, 2001.

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APPENDIX 1 COMPOUND DETAILS

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Appendix 1

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Ageing of Rubber - Accelerated Heat Ageing Test Results

Natural Rubber

Natural Rubber Ingredient

Amount (pphr)

Compound A – Standard

Smoked sheet

100

Curing conditions: 35' @ 141 °C

HAF black

50

Stearic acid

2.5

Pine tar

4.5

Zinc oxide

5

CBS

0.5

PBN

1.0

Sulphur

2.5

Compound B - Good Ageing

Smoked sheet

100

Curing conditions: 30' @ 148 °C

HAF black

50

Stearic acid

0.5

Pine tar

4.5

Zinc oxide

5

TMTD

2.5

PBN

1.0

MBT

1.0

Compound C - Mineral Filler Loaded

Smoked sheet

100

Curing conditions: 20' @ 141 °C

Stearic acid

1.5

Petroleum-based softener

5

Zinc oxide

5

CBS

0.5

PBN

1.0

Sulphur

2.5

Precipitated calcium carbonate

80

Compound D - Mineral Filler

Smoked sheet

100

(Heavy Loaded)

Stearic acid

1.5

Curing conditions: 20' @ 141 °C

Petroleum-based softener

25

Zinc oxide

5

CBS

0.6

PBN

1.0

Sulphur

3.2

Precipitated calcium carbonate

200

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Appendix 1

Styrene Butadiene Rubber Ingredient

Amount (pphr)

Compound E - General Purpose

SBR 1500

100

Curing conditions: 40' @ 153 °C

HAF black

50

Stearic acid

2

Petroleum-based softener

4.5

Zinc oxide

3

CBS

1.0

PBN

1.0

Sulphur

1.75

Compound F - Good Ageing

SBR 1500

100

Curing conditions: 40' @ 153 °C

HAF black

50

Stearic acid

2

Petroleum-based softener

4.5

Zinc oxide

3

TMTD

3

PBN

1.0

MBTS

1.0

Compound G - General Purpose

SBR 1710

100

Curing conditions: 40' @ 153 °C

HAF black

50

Stearic acid

2

Petroleum-based softener

4.5

Zinc oxide

3

CBS

1.0

PBN

1.0

Sulphur

1.75

Compound H - Good Ageing

SBR 1710

100

Curing conditions: 50' @ 153 °C

HAF black

50

Stearic acid

2

Petroleum-based softener

4.5

Zinc oxide

3

TMTD

3

PBN

1.0

MBTS

1.0

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Butyl Rubber

Butyl Rubber Ingredient

Amount (pphr)

Compound J - General Purpose

Polysar 301 (high unsaturation)

100

Curing conditions: 40' @ 153 °C

FEF black

50

Zinc oxide

5

Stearic acid

2

MBT

0.5

TMT

1.0

Sulphur

2

Compound K - Good Ageing

Polysar 100 butyl (low unsaturation) 100

Curing conditions: 90' @ 153 °C

HAF black

50

Zinc oxide

25

Sulphur

2

MBTS

4

GMF

2

© Copyright 2001 Rapra Technology Limited

27

Appendix 1

Polychloroprene Ingredient

Amount (pphr)

Compound L - General Purpose

Neoprene type WRT

100

Curing conditions: 60' @ 153 °C

Light calcined magnesia

4

PBN

2

Stearic acid

0.5

SRF black

40

Petroleum-based softener

5

Robac 22

0.75

Zinc oxide

5

Compound M - Natural Ageing

Neoprene type WRT

100

Curing conditions: 60' @ 153 °C

Light calcined magnesia

4

Akroflex CD

2

Stearic acid

0.5

SRF black

50

Petroleum-based softener

5

DOTG

0.75

TMT-MS

0.75

Sulphur

0.75

Zinc oxide

5

Compound N - Heat Ageing

Neoprene type WRT

100

Curing conditions: 60' @ 153 °C

Light calcined magnesia

4

Aranox

0.5

Akroflex CD

2

Octamine

3.5

Stearic acid

0.5

SRF black

30

Precipitated calcium carbonate

90

Low volatile process oil

8

Robac 22

1

Zinc oxide

25

28

Ageing of Rubber - Accelerated Heat Ageing Test Results

Nitrile Rubber

Nitrile Rubber

Compound P - General Purpose

Ingredient

Amount (pphr)

Nitrile rubber

100

Curing conditions: 40' @ 153 °C

Compound R - Good Ageing

(ca. 32-34% acrylonitrile) SRF black

50

DOP

20

Zinc oxide

5

Stearic acid

1

PBN

1

MBTS

1.5

Sulphur

1.5

Nitrile rubber

100

Curing conditions: 30' @ 153 °C

(ca. 35% acrylonitrile) SRF black

50

DOP

10

Polypropylene adipate

10

Zinc oxide

5

Stearic acid

1

Flectol H

2

TMTD

3

CBS

3

© Copyright 2001 Rapra Technology Limited

29

Appendix 1

Miscellaneous Ingredient

Amount (pphr)

Compound S - Acrylate Rubber

Hycar 4021

100

Curing conditions: 90' @ 153 °C

SRF black

50

Stearic acid

1

Triethylene tetramine

2

TMTM

1

Sulphur

3

Compound T -

Hypalon 20

100

Chlorosulphonated polyethylene

Precipitated calcium carbonate

45

Curing conditions: 30' @ 153 °C

Hydrogenated wood rosin

5

Litharge

20

MBTS

0.5

Flectol H

2

Process oil

10

Robac P25

0.75

Light calcined magnesia

10

Compound W - Polysulphide Rubber

Thiokol St

100

Curing conditions: 30' @ 141 °C

SRF black

60

Stearic acid

3

GMF

1.5

Zinc oxide

0.5

Dimethyl silicone gum (slightly unsaturated)

100

Diatomaceous silica

45

Fine silica

36

Ferric oxide

1

2,4-dichlorobenzoyl peroxide in silicone fluid

2

Compound X - Silicone Rubber Curing conditions: 10' @ 135 °C Post cure 1 h @ 150 °C, 24 h @ 250 °C in air

30

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compounds

New Compounds Ingredient

Amount (pphr)

Compound N1 - FVMQ

Silastic LS 238 OU

100

Curing conditions: 10' @ 171 °C,

Silastic HT-1

1

Post cure 4 h @ 200 °C in air

DHBP (50% silicone oil)

0.9

Compound N2 - HNBR

Zetpol 2000L

100

Curing conditions: 30' @ 180 °C

Spheron 4000

60

Naugard 445

1.5

Rhenogran ZMMBI 50

3

Zinc Oxide Active

3

Peroximon F40

8

Compound N3 - Epoxidised natural

Based on Epoxyprene 50, low

Curing conditions: 23.5' @ 141 °C

black loading, sulphur, TMTD, CBS and stabilised. Details confidential.

Compound N4 - Chlorinated polyethylene

Tyrin CM 3630

100

Curing conditions: 30' @ 180 °C

Flectol pastilles

0.2

Maglite DE

10

SRF N772 black

60

FEF N550 black

50

Britomya BSH

20

Bisoflex TOT

35

Drapex 39

4

Perkadox 14/40

6.25

Rhenogran TAC 50

5.6

Compound N5 - Fluorocarbon

Viton A-202C

100

Curing conditions: 20' @ 170 °C,

MT N990 Black

20

Post cure 24 h @ 225 °C in air

Sturge VE

6

Maglite DE

3

Compound N6 - Exxpro

Exxpro MDX90-10

100

Curing conditions: 45' @ 150 °C

HAF N330 Black

50

Stearic Acid

2

Zinc oxide

0.5

Tetrone A

1

© Copyright 2001 Rapra Technology Limited

31

Appendix 1

New Compounds (continued) Ingredient

Amount (pphr)

Compound N7 - Epichlorohydrin

Hydrin C65

100

Curing conditions: 37' @ 165 °C

SRF N772 black

70

Winnofil S

5

Paraplex G50

5

DOP

5

Vulkanox MB

1

Stearic acid

1

Span 60

1

Zisnet F

1

DPG

0.3

Maglite DE

5

Compound N8 - EPDM

Vistalon 7000

100

Curing conditions: 17.5' @ 165 °C

Zinc Oxide

10

Stearic Acid

2

SRF N772 Black

45

FEF N550 Black

60

Strukpar 2280

59

Sulphur

1

TMTD

2.5

ZDMC

2.67

NDBC

2

Sulfasan R

1.7

Compound N9 - EVA

Levapren 400

100

Curing conditions: 30' @ 165 °C

Staboxal PCD

3

Post cure 2 h @ 165 °C in steam

Zinc stearate

2

Vulkanox DDA

1

FEF N550 Black

30

Mistron Vapour

50

Perkadox 14/40

6

TAC

4

Compound N10 - PU

Adiprene FM

100

Curing conditions: 7.5' @ 165 °C

FEF N550 Black

40

DBP

5

Stearic Acid

1

Dicup 40C

3

Rhenogran TAC50

2

32

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participants’ Compounds

Participants' Compounds Details of most of the formulations are not disclosed. Compound P1

Blend of two EPDM copolymers, one with high ethylene content and medium Mooney viscosity, the other with medium ethylene content and low Mooney viscosity. Contains carbon black, zinc oxide, TMQ, paraffinic process oil, dicumyl peroxide and a sulphur donor.

Compound P2

Silicone gum blended to give a methylvinylsiloxane content of 0.31% Silicone processing aid Precipitated silica Fumed silica Vinyl specific peroxide Urea

Compound P8

Natural rubber Activators Fillers Process aids 6PPD TMQ Antiozonant wax Sulphenamide TMTM Sulphur

100 7 105 50 3 2 4 0.75 0.1 1.5

(pphr)

Compound P10

NBR (28% ACN) Mineral fillers Silica Zinc oxide Stearic acid Antioxidants Sulphur cure system

100 100 25 10 1

(pphr)

© Copyright 2001 Rapra Technology Limited

33

34

Ageing of Rubber - Accelerated Heat Ageing Test Results

APPENDIX 2 ACCELERATED HEAT AGEING RESULTS

© Copyright 2001 Rapra Technology Limited

35

36

Ageing of Rubber - Accelerated Heat Ageing Test Results

Natural Rubber - Standard

Hardness Compound A 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

50

60

Heat Ageing Period (Days)

Tensile Strength Compound A 100°C

70°C

80°C

90°C

40.0

Tensile Strength (Mpa)

30.0

20.0

10.0

0.0 0

10

20

30

40

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

37

Compound A

Elongation at Break Compound A 100°C

70°C

80°C

90°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

10

20

30

40

50

60

40

50

60

Heat Ageing Period (Days)

Modulus at 100% Compound A 100°C

70°C

80°C

90°C

10.0

Modulus at 100% (Mpa)

8.0

6.0

4.0

2.0

0.0 0

10

20

30 Heat Ageing Period (Days)

38

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

4.3

-0.2

T2

T10

-21

1.9

6.7

45

44

-10

-0.2

3

24

36

-71

-83.5

-155.3

0.0

-100

-64.0

-91.7

36

300% Modulus

-5.3

44

100% Modulus

-81

-71

33.3

40 years at 23 °C

Rebound Resilience

-48

Elongation at Break

-77

6.7

Hot Wet

-48.7

-35

Tensile Strength

7.6

Hot Dry

-100

-87

-18

-100

-82.7

33.3

40 years at 40 °C

WLF Predictions (%)

Tg

12

Temperate

40 Year Natural Ageing Change (%)

Hardness

Property

Compound A (natural rubber - standard)

62.3 years

16.7 years

43.1 years

61.9 years

633.4 days

17.5 years

80.8 years

11.5 years

23 °C (time)

5.6 years

2.5 years

4.3 years

4.1 years

156.9 days

2.7 years

7.1 years

2.1 years

40 °C (time)

Arrhenius Predictions

109.2

87.0

104.8

122.8

63.3

85.2

110.6

77.0

Activation Energy (kJ)

Natural Rubber - Standard

39

Compound A

40

Ageing of Rubber - Accelerated Heat Ageing Test Results

Natural Rubber - Good Ageing

Hardness Compound B 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound B 100°C

70°C

80°C

90°C

Tensile Strength (Mpa)

30.0

20.0

10.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

41

Compound B

Elongation at Break Compound B 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound B 100°C

70°C

80°C

90°C

8.0

Modulus at 100% (Mpa)

6.0

4.0

2.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

42

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-13

75

27

3.1

-0.9

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

12

-11

Tensile Strength

Tg

10

Temperate

18

-1.6

1.5

14

121

-38

-24

24

Hot Dry

15

-2.4

-2.4

30

95

-40

-34

21

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound B (natural rubber - good ageing)

-7.3

-50.6

-48.4

67.0

172.9

-86.1

-15.2

49.3

40 years at 23 °C

-28.5

-74.1

-194.3

24.3

154.8

-100.0

-70.8

49.3

40 years at 40 °C

WLF Predictions (%)

394.9 days

21.8 years

153.6 days

9.6 years

30.2 years

101.8 years

24.4 years

23 °C (time)

226 days

5.3 years

49 days

2.4 years

5.1 years

13 years

6.6 years

40 °C (time)

Arrhenius Predictions

25.3

64.4

51.9

62.1

81.0

93.4

59.5

Activation Energy (kJ)

Natural Rubber - Good Ageing

43

Compound B

44

Ageing of Rubber - Accelerated Heat Ageing Test Results

Natural Rubber - Mineral Filler Loaded

Hardness Compound C 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

80

60

40

20 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound C 100°C

70°C

80°C

90°C

Tensile Strength (Mpa)

30.0

20.0

10.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

45

Compound C

Elongation at Break Compound C 100°C

70°C

80°C

90°C

800

700

Elongation at Break (%)

600

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound C 100°C

70°C

80°C

90°C

5.0

Modulus at 100% (Mpa)

4.0

3.0

2.0

1.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

46

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-2

-1.7

T2

T10

-6.7

-0.9

0.5

5.6

54

-3.3

-2.7

-3.7

-1.4

31

-24

-34.4

-3.3

-1.3

10.6

-5.0

-7.0

-39.6

46

300% Modulus

1.7

73

100% Modulus

-18

-49

0.0

40 years at 23 °C

Rebound Resilience

-11

Elongation at Break

-43

7.9

Hot Wet

-20.3

-24

Tensile Strength

4

Hot Dry

-41.8

-39.8

-73.6

-54.6

-28.3

85.4

-92.2

-82.8

-29.6

40 years at 40 °C

WLF Predictions (%)

Tg

10

Temperate

40 Year Natural Ageing Change (%)

Hardness

Property

Compound C (natural rubber - mineral filler loaded)

3.8 years

265.2 years

291.6 years

648.2 years

100.5 days

607.8 years

41.2 years

127.8 years

89 years

23 °C (time)

250.5 days

21.5 years

20.1 years

29.3 years

34.8 days

45.4 years

4.8 years

9 years

12 years

40 °C (time)

Arrhenius Predictions

78.1

113.9

121.4

140.5

48.1

117.7

97.6

120.5

91.0

Activation Energy (kJ)

Natural Rubber - Mineral Filler Loaded

47

Compound C

48

Ageing of Rubber - Accelerated Heat Ageing Test Results

Natural Rubber - Mineral Filler (Heavy Loaded)

Hardness Compound D 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50

40 0

30

60

90

120

150

180

100

120

Heat Ageing Period (Days)

Tensile Strength Compound D 100°C

70°C

80°C

90°C

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

20

40

60

80

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

49

Compound D

Elongation at Break Compound D 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

20

40

60

80

100

120

80

100

120

Heat Ageing Period (Days)

Modulus at 100% Compound D 100°C

70°C

80°C

90°C

3.5

Modulus at 100% (Mpa)

3.0

2.5

2.0

1.5

1.0 0

20

40

60 Heat Ageing Period (Days)

50

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-73

83

92

0

-0.9

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

5.3

-19

Tensile Strength

Tg

8.9

Temperate

-8.2

1.3

2.4

49

72

-86

-31

7.6

Hot Dry

-3.5

-0.9

-0.6

30

11 5

-85

-14

16

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

5.3

-38.0

-104.9

21.8

96.8

0.0

-41.7

-12.3

40 years at 23 °C

-5.8

-64.9

-198.0

-62.8

177.7

-91.5

-82.3

63.9

40 years at 40 °C

WLF Predictions (%)

Compound D (natural rubber - mineral filler (heavy loaded))

175.8 years

26.2 years

11.5 years

22.7 years

13.3 years

68.1 years

23 °C (time)

15.2 years

3.0 years

2.5 years

4.3 years

520.7 days

9.6 years

40 °C (time)

Arrhenius Predictions

111.1

98.3

68.8

75.1

101.2

88.8

Activation Energy (kJ)

Natural Rubber - Mineral Filler (Heavy Loaded)

51

Compound D

52

Ageing of Rubber - Accelerated Heat Ageing Test Results

Styrene Butadiene Rubber - General Purpose

Hardness Compound E 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound E 100°C

70°C

80°C

90°C

35.0

Tensile Strength (Mpa)

30.0

25.0

20.0

15.0

10.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

53

Compound E

Elongation at Break Compound E 100°C

70°C

80°C

90°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound E 100°C

70°C

80°C

90°C

20.0

Modulus at 100% (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

54

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-1.6

-1.1

T2

T10

11

0.7

-3.5

79

172

8.2

1.5

-3

73

133

-63

-10.7

-87.9

>53.4

554.1

-83.0

-26.8

17.9

28

300% Modulus

12

108

100% Modulus

-66

-31

19.7

40 years at 23 °C

Rebound Resilience

-47

Elongation at Break

-30

15

Hot Wet

-28.6

- 20

Tensile Strength

18

Hot Dry

16.1

-58.8

-52.3

-161.3

>53.4

839.8

-100.0

-57.6

37.4

40 years at 40 °C

WLF Predictions (%)

Tg

12

Temperate

40 Year Natural Ageing Change (%)

Hardness

Property

Compound E (styrene butadiene rubber - general purpose)

5.9 years

322.3 years

4.3 years

11.2 years

20.8 years

40.4 years

176 years

50.1 years

23 °C (time)

461.3 days

23.1 years

434.1 days

3.4 years

4.2 years

7.9 years

18 years

8 years

40 °C (time)

Arrhenius Predictions

69.9

119.5

58.1

54.5

72.6

74.1

104.4

83.5

Activation Energy (kJ)

Styrene Butadiene Rubber - General Purpose

55

Compound E

56

Ageing of Rubber - Accelerated Heat Ageing Test Results

Styrene Butadiene Rubber - Good Ageing

Hardness Compound F 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound F 100°C

70°C

80°C

90°C

35.0

Tensile Strength (Mpa)

30.0

25.0

20.0

15.0

10.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

57

Compound F

Elongation at Break Compound F 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound F 100°C

70°C

80°C

90°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

58

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© Copyright 2001 Rapra Technology Limited

-23

57

34

1.3

-0.7

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

7.4

-3.5

Tensile Strength

Tg

11

Temperate

11

-0.3

-2

53

13 3

-46

-17

17

Hot Dry

10

0.3

-1.2

75

126

-53

-26

15

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

17.6

80.4

322.4

-34.3

-24.4

27.5

40 years at 23 °C

17.6

174.8

553.1

-56.4

-31.9

56.3

40 years at 40 °C

WLF Predictions (%)

Compound F (styrene butadiene rubber - good ageing)

241 days

659.7 days

16.7 years

13.4 years

19.2 years

13.3 years

18 years

11 years

23 °C (time)

72.3 days

429.5 days

2.5 years

2.2 years

4.4 years

3.1 years

3.8 years

3.3 years

40 °C (time)

Arrhenius Predictions

54.6

19.5

81.6

66.6

66.8

70.0

54.2

Activation Energy (kJ)

Styrene Butadiene Rubber - Good Ageing

59

Compound F

60

Ageing of Rubber - Accelerated Heat Ageing Test Results

Styrene Butadiene Rubber - General Purpose

Hardness Compound G 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound G 100°C

70°C

80°C

90°C

25.0

Tensile Strength (Mpa)

20.0

15.0

10.0

5.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

61

Compound G

Elongation at Break Compound G 100°C

70°C

80°C

90°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound G 100°C

70°C

80°C

90°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

150

180

Heat Ageing Period (Days)

62

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-48

107

-31

-0.1

0.4

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

4.3

-17

Tensile Strength

Tg

18

Temperate

1.9

0.3

-0.4

-90

200

-66

-27

25

Hot Dry

0.53

2.1

0.3

-93

51

-72

-46

24

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

-0.4

-6.0

-406.4

95.2

550.3

-69.8

-38.8

45.0

40 years at 23 °C

-30.3

-37.9

80.7

1091.3

-100.0

-54.3

61.3

40 years at 40 °C

WLF Predictions (%)

Compound G (styrene butadiene rubber - general purpose)

12.9 years

23.1 years

76.1 years

27.1 years

89.5 years

41 years

34.3 years

23 °C (time)

3.1 years

5.4 years

13.2 years

4.9 years

12.2 years

5.8 years

6.5 years

40 °C (time)

Arrhenius Predictions

64.7

65.8

79.3

77.8

90.3

88.6

75.3

Activation Energy (kJ)

Styrene Butadiene Rubber - General Purpose

63

Compound G

64

Ageing of Rubber - Accelerated Heat Ageing Test Results

Styrene Butadiene Rubber - Good Ageing

Hardness Compound H 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50 0

30

60

90

120

150

180

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound H 100°C

70°C

80°C

90°C

25.0

Tensile Strength (Mpa)

20.0

15.0

10.0

5.0 0

30

60

90 Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

65

Compound H

Elongation at Break Compound H 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound H 100°C

70°C

80°C

90°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

66

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-24

94

26

-0.6

-1.1

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

14

-11

Tensile Strength

Tg

14

Temperate

16

-1

0.3

64

205

-48

-25

21

Hot Dry

16

0

1.2

65

96

-53

-26

18

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

-92.8

-34.6

-373.2

>100.8

373.8

-100.0

-45.9

45.1

40 years at 23 °C

-64.1

-442.9

>100.8

1162.1

-100.0

-65.2

68.6

40 years at 40 °C

WLF Predictions (%)

Compound H (styrene butadiene rubber - good ageing)

34.2 years

14.2 years

84.7 years

672.8 days

15.3 years

4.3 years

13.4 years

10.2 years

23 °C (time)

8.5 years

5 years

19 years

231.1 days

4.4 years

512 days

3.4 years

3.2 years

40 °C (time)

Arrhenius Predictions

63.0

47.1

67.8

48.5

56.4

50.4

62.5

51.9

Activation Energy (kJ)

Styrene Butadiene Rubber - Good Ageing

67

Compound H

68

Ageing of Rubber - Accelerated Heat Ageing Test Results

Butyl Rubber - General Purpose

Hardness Compound J 70°C

100°C

80°C

90°C

120°C

80

Hardness (Micro-IRHD)

70

60

50

40

30 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound J 80°C

90°C

100°C

70°C

120°C

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

69

Compound J

Elongation at Break Compound J 80°C

90°C

100°C

70°C

120°C

800

700

Elongation at Break (%)

600

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound J 80°C

90°C

100°C

70°C

120°C

5.0

Modulus at 100% (Mpa)

4.0

3.0

2.0

1.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

70

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

8.3

-4.4

-3

300% Modulus

T2

T10

Rebound Resilience

18

14

100% Modulus

Tg

-9.4

0

Tensile Strength

Elongation at Break

0

Temperate

27

-1.8

-3.1

25

30

-19

0.8

0

Hot Dry

19

-2

-1

13

14

-8.8

7. 3

0

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound J (butyl rubber - general purpose)

-1.9

-35.7

11.0

22.2

-22.9

-3.2

0.0

40 years at 23 °C

-16.7

-75.0

5.8

2.6

54.7

-20.6

-3.3

40 years at 40 °C

WLF Predictions (%)

27.9 years

1026.1 years

609 days

23 °C (time)

5.1 years

109.9 years

244 days

40 °C (time)

Arrhenius Predictions

76.7

101.4

41.5

Activation Energy (kJ)

Butyl Rubber - General Purpose

71

Compound J

72

Ageing of Rubber - Accelerated Heat Ageing Test Results

Butyl Rubber - Good Ageing

Hardness Compound K 100°C

70°C

80°C

90°C

120°C

90

Hardness (Micro-IRHD)

80

70

60

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound K 80°C

90°C

100°C

70°C

120°C

20.0

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

73

Compound K

Elongation at Break Compound K 80°C

90°C

100°C

70°C

120°C

700

Elongation at Break (%)

600

500

400

300

200 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound K 80°C

90°C

100°C

70°C

120°C

4.0

Modulus at 100% (Mpa)

3.0

2.0

1.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

74

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-14

45

66

-3

-2.2

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

21

-5.1

Tensile Strength

Tg

4.4

Temperate

23

-1.4

-2.2

0

-20

2.4

0.72

4.3

Hot Dry

6.1

-1.5

-1

8.4

27

-15

0

6.9

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound K (butyl rubber - good ageing)

0

28.9

32.3

-52.8

-10.7

40 years at 23 °C

-0.8

48.1

14.6

-56.7

-10.7

40 years at 40 °C

WLF Predictions (%)

33.5 years

3.5 years

23 °C (time)

7.7 years

2.0 years

40 °C (time)

Arrhenius Predictions

66.7

25.0

Activation Energy (kJ)

Butyl Rubber - Good Ageing

75

Compound K

76

Ageing of Rubber - Accelerated Heat Ageing Test Results

Polychloroprene - General Purpose

Hardness Compound L 100°C

70°C

90°C

80°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound L 100°C

70°C

90°C

80°C

Tensile Strength (Mpa)

25.0

20.0

15.0

10.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

77

Compound L

Elongation at Break Compound L 100°C

70°C

90°C

80°C

400

Elongation at Break (%)

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound L 100°C

70°C

90°C

80°C

20.0

Modulus at 100% (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

78

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-

300% Modulus

Rebound Resilience

Tg

7.8

-0.9

40

100% Modulus

T10

-12

Elongation at Break

-1.7

-1.2

Tensile Strength

T2

5.6

Temperate

4.4

-0.08

-1.4

-

53

-11

-5.3

10

Hot Dry

2

0.5

-1.5

-

89

-13

-18

13

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

0.5

28.1

-39.3

0.0

1.4

40 years at 23 °C

0.5

79.0

-62.9

0.0

4.1

40 years at 40 °C

WLF Predictions (%)

Compound L (polychloroprene - general purpose)

26 years

8.3 years

23 °C (time)

6.3 years

2.9 years

40 °C (time)

Arrhenius Predictions

64.1

47.1

Activation Energy (kJ)

Polychloroprene - General Purpose

79

Compound L

80

Ageing of Rubber - Accelerated Heat Ageing Test Results

Polychloroprene - Natural Ageing

Hardness Compound M 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound M 100°C

70°C

80°C

90°C

Tensile Strength (Mpa)

30.0

25.0

20.0

15.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

81

Compound M

Elongation at Break Compound M 100°C

70°C

80°C

90°C

400

Elongation at Break (%)

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound M 100°C

70°C

80°C

90°C

25.0

Modulus at 100% (Mpa)

20.0

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

82

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-31

74

12

-3.3

-0.5

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

13

-12

Tensile Strength

Tg

16

Temperate

2.1

0.3

-1.6

66

100

-42

-15

21

Hot Dry

2.2

0.8

0.2

24

72

-42

-17

23

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

18.7

104.1

-36.1

32.4

40 years at 23 °C

39.0

412.3

-100.0

42.9

40 years at 40 °C

WLF Predictions (%)

Compound M (polychloroprene - natural ageing)

43.3 years

59.6 years

24 years

16.1 years

15.1 years

23 °C (time)

12.4 years

9.1 years

5.6 years

4.7 years

4.5 years

40 °C (time)

Arrhenius Predictions

56.6

85.2

66.1

55.4

54.7

Activation Energy (kJ)

Polychloroprene - Natural Ageing

83

Compound M

84

Ageing of Rubber - Accelerated Heat Ageing Test Results

Polychloroprene - Heat Ageing

Hardness Compound N 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

95

90

85

80

75 0

30

60

90

120

150

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N 100°C

70°C

80°C

90°C

18.0

Tensile Strength (Mpa)

16.0

14.0

12.0

10.0

8.0 0

30

60

90

180

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

85

Compound N

Elongation at Break Compound N 100°C

70°C

80°C

90°C

500

Elongation at Break (%)

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N 100°C

70°C

80°C

90°C

Modulus at 100% (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

86

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-29

96

-10

-6.2

-1.1

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

25

-16

Tensile Strength

Tg

11

Temperate

25

-0.7

-6.3

-48

135

-57

-13

11

Hot Dry

18

0.3

-3.4

-34

11 7

-65

-20

14

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound N (polychloroprene - heat ageing)

18.4

185.1

-8.4

103.9

14.1

40 years at 23 °C

42.5

332.5

-62.2

147.6

25.0

40 years at 40 °C

WLF Predictions (%)

629.3 days

66.6 years

72.3 years

13.8 years

11.4 years

23 °C (time)

454.7 days

11.2 years

14.5 years

4.1 years

3.7 years

40 °C (time)

Arrhenius Predictions

14.7

81.0

72.9

55.3

51.3

Activation Energy (kJ)

Polychloroprene - Heat Ageing

87

Compound N

88

Ageing of Rubber - Accelerated Heat Ageing Test Results

Nitrile Rubber - General Purpose

Hardness Compound P 100°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P 100°C

80°C

90°C

70°C

Tensile Strength (Mpa)

25.0

20.0

15.0

10.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

89

Compound P

Elongation at Break Compound P 100°C

80°C

90°C

70°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P 100°C

80°C

90°C

70°C

25.0

Modulus at 100% (Mpa)

20.0

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

90

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-34

75

62

-3.6

0

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

14

-4.8

Tensile Strength

Tg

21

Temperate

15

-0.2

-2.4

175

16 4

-52

0

28

Hot Dry

10

1.1

-2.5

17 5

12 7

-48

5.8

23

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound P (nitrile rubber - general purpose)

-28.6

-57.3

158.4

130.4

-100.0

0.0

39.5

40 years at 23 °C

-170.9

-90.1

205.4

1148.6

-100.0

0.0

81.8

40 years at 40 °C

WLF Predictions (%)

30 years

30.3 years

9.6 years

43.2 years

24.3 years

138.9 years

23 °C (time)

4.4 years

6.6 years

2.8 years

8 years

5.5 years

19.8 years

40 °C (time)

Arrhenius Predictions

87.0

69.0

55.9

76.5

67.7

88.3

Activation Energy (kJ)

Nitrile Rubber - General Purpose

91

Compound P

92

Ageing of Rubber - Accelerated Heat Ageing Test Results

Nitrile Rubber - Good Ageing

Hardness Compound R 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound R 100°C

70°C

80°C

90°C

25.0

Tensile Strength (Mpa)

20.0

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

93

Compound R

Elongation at Break Compound R 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound R 100°C

70°C

80°C

90°C

20.00

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

94

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-28

126

62

-1.3

-0.1

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

16

-8.3

Tensile Strength

Tg

34

Temperate

4.4

0

-1.3

10

176

-42

-11

55

Hot Dry

-11

0.4

-0.5

92

129

-37

-13

54

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound R (nitrile rubber - good ageing)

41.1

123.4

72.5

40 years at 23 °C

179.5

259.3

81.8

40 years at 40 °C

WLF Predictions (%)

31.7 years

69.5 years

32 days

15.8 years

23 °C (time)

6.7 years

5.8 years

13 days

5.8 years

40 °C (time)

Arrhenius Predictions

70.8

113.0

39.8

45.2

Activation Energy (kJ)

Nitrile Rubber - Good Ageing

95

Compound R

96

Ageing of Rubber - Accelerated Heat Ageing Test Results

Miscellaneous - Acrylate Rubber

Hardness Compound S 150°C

170°C

160°C

140°C

100

90

Hardness (Micro-IRHD)

80

70

60

50

40

30 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound S 150°C

170°C

160°C

140°C

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

97

Compound S

Elongation at Break Compound S 150°C

170°C

160°C

140°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

90

120

Heat Ageing Period (Days)

Modulus at 100% Compound S 150°C

170°C

160°C

140°C

8.0

Modulus at 100% (Mpa)

6.0

4.0

2.0

0.0 0

30

60 Heat Ageing Period (Days)

98

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

Rebound Resilience

Tg

-14

0.7

T10

-

300% Modulus

0.4

-1.3

100% Modulus

T2

-5.5

0

-4.8

Temperate

-10

0. 6

0. 7

-

9.4

-3.2

8.4

-4.1

Hot Dry

-48

1.2

1.1

-

5.9

-2.9

10

-5.5

Hot Wet

40 Year Natural Ageing Change (%)

Elongation at Break

Tensile Strength

Hardness

Property

Compound S (acrylate rubber)

-74.3

0

0

>-76.1

0

40 years at 23 °C

-83.4

0

0

>-76.1

0

40 years at 40 °C

WLF Predictions (%)

3863 years

23 °C (time)

646 years

40 °C (time)

Arrhenius Predictions

81.2

Activation Energy (kJ)

Miscellaneous - Acrylate Rubber

99

Compound S

100

Ageing of Rubber - Accelerated Heat Ageing Test Results

Miscellaneous - Chlorosulphonated Polyethylene

Hardness Compound T 100°C

80°C

90°C

70°C

70

Hardness (Micro-IRHD)

65

60

55

50

45 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound T 100°C

80°C

90°C

70°C

14.0

Tensile Strength (Mpa)

12.0

10.0

8.0

6.0 0

30

60

90

120

150

180

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

101

Compound T

Elongation at Break Compound T 100°C

80°C

90°C

70°C

500

Elongation at Break (%)

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound T 100°C

80°C

90°C

70°C

12.00

Modulus at 100% (Mpa)

10.00

8.00

6.00

4.00

2.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

102

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-34

55

41

-0.4

-0.9

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Rebound Resilience

14

14

Tensile Strength

Tg

3.3

Temperate

34

-0.3

-0.2

38

62

-32

18

0

Hot Dry

45

-0.9

-0.6

49

63

-38

6

7.3

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

67.0

-43.5

30.5

96.1

68.8

-57.8

36.7

96.1

40 years at 40 °C

WLF Predictions (%) 40 years at 23 °C

Compound T (chlorosulphonated polyethylene) 23 °C (time)

40 °C (time)

Arrhenius Predictions

Activation Energy (kJ)

Miscellaneous - Chlorosulphonated Polyethylene

103

Compound T

104

Ageing of Rubber - Accelerated Heat Ageing Test Results

Miscellaneous - Polysulphide Rubber

Hardness Compound W 100°C

70°C

80°C

90°C

80

Hardness (Micro-IRHD)

70

60

50

40

30 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound W 100°C

70°C

80°C

90°C

8.0

Tensile Strength (Mpa)

6.0

4.0

2.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

105

Compound W

Elongation at Break Compound W 100°C

70°C

80°C

90°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound W 100°C

70°C

80°C

90°C

4.0

Modulus at 100% (Mpa)

3.0

2.0

1.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

106

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-

300% Modulus

Rebound Resilience

Tg

1.9

-1.9

12

100% Modulus

T10

1.7

Elongation at Break

5.4

11

Tensile Strength

T2

5.7

Temperate

0

-1.5

5.2

-

4.3

6.7

9.3

5.9

Hot Dry

-2.1

-1.6

2.2

-

4.3

-4.1

2.1

3.1

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound W (polysulphide rubber)

-55.8

-67.7

3.0

-63.2

4. 0

-17.1

-13.5

-100.0

40 years at 23 °C

-100.0

-100.9

-192.5

-100.0

-100.0

-67.7

-100.0

-100.0

40 years at 40 °C

WLF Predictions (%)

413.4 years

9 years

23 °C (time)

29.6 years

679 days

40 °C (time)

Arrhenius Predictions

103.3

119.6

71.7

Activation Energy (kJ)

Miscellaneous - Polysulphide Rubber

107

Compound W

108

Ageing of Rubber - Accelerated Heat Ageing Test Results

Miscellaneous - Silicone Rubber

Hardness Compound X 150°C

170°C

210°C

70

Hardness (Micro-IRHD)

65

60

55

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound X 150°C

170°C

210°C

9.0

Tensile Strength (Mpa)

8.0

7.0

6.0

5.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

109

Compound X

Elongation at Break Compound X 150°C

170°C

210°C

300

Elongation at Break (%)

250

200

150

100

50

0 0

30

60

90

120

150

180

120

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound X 150°C

170°C

210°C

6.0

Modulus at 100% (Mpa)

5.0

4.0

3.0

2.0

1.0

0.0 0

30

60

90 Heat Ageing Period (Days)

110

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

16

7.4

-8.3

Tensile Strength

Elongation at Break

100% Modulus

Rebound Resilience

12

1.9

T10

Tg

0.9

T2

300% Modulus

13

Temperate

14

1.6

0.8

-4.1

-20

7.9

12

Hot Dry

9.4

0.5

0.4

-5.5

4.6

22

11

Hot Wet

40 Year Natural Ageing Change (%)

Hardness

Property

Compound X (silicone rubber)

0. 0

0. 0

0. 0

40 years at 23 °C

-11.0

0.0

0.0

40 years at 40 °C

WLF Predictions (%)

171.6 years

263.9 years

23 °C (time)

44.1 years

73.3 years

40 °C (time)

Arrhenius Predictions

103.3

61.6

58.1

Activation Energy (kJ)

Miscellaneous - Silicone Rubber

111

Compound X

112

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - FVMQ

Hardness Compound N1 150°C

170°C

210°C

85

Hardness (Micro-IRHD)

80

75

70

65 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N1 150°C

170°C

210°C

10.00

Tensile Strength (Mpa)

9.00

8.00

7.00

6.00

5.00

4.00 0

30

60

90

120

150

180

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

113

Compound N1

Elongation at Break Compound N1 150°C

170°C

210°C

250

Elongation at Break (%)

200

150

100

50

0 0

30

60

90

120

150

180

120

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N1 150°C

170°C

210°C

8.00

7.00

Modulus at 100% (Mpa)

6.00

5.00

4.00

3.00

2.00

1.00

0.00 0

30

60

90 Heat Ageing Period (Days)

114

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

0.0

-31.8

29.4

Tensile Strength

Elongation at Break

100% Modulus

Rebound Resilience

Tg

T10

T2

300% Modulus

0.0

40 years at 23 °C

41.6

-41.2

0.0

0.0

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N1 (FVMQ)

25%

-25%

-10%

10%

Measured Change

456.6 days

2.2 years

3.4 years

41.1 years

23 °C (time)

Arrhenius Predictions

298.9 days

498.3 days

2.0 years

16.6 years

40 °C (time)

19.2

21.1

23.5

41.3

Activation Energy (kJ)

New Compound - FVMQ

115

Compound N1

116

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - HNBR

Hardness Compound N2 150°C

170°C

160°C

140°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N2 150°C

170°C

160°C

140°C

30.0

28.0

Tensile Strength (Mpa)

26.0

24.0

22.0

20.0

18.0

16.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

117

Compound N2

Elongation at Break Compound N2 150°C

170°C

160°C

140°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

90

120

Heat Ageing Period (Days)

Modulus at 100% Compound N2 150°C

170°C

160°C

140°C

25.0

Modulus at 100% (Mpa)

20.0

15.0

10.0

5.0

0.0 0

30

60 Heat Ageing Period (Days)

118

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

>28.2

-49.4

>595.2

68.6

Tensile Strength

Elongation at Break

100% Modulus

300% Modulus

Rebound Resilience

Tg

T10

T2

49.3

40 years at 23 °C

68.6

>595.2

-57.5

>28.2

49.3

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N2 (HNBR)

50%

300%

-25%

10%

25%

Measured Change

41.9 days

157.1 years

13.6 years

2.11E+7 years

8408.7 years

23 °C (time)

Arrhenius Predictions

25.3 days

32.1 years

3.6 years

568837 years

947.2 years

40 °C (time)

23.0

72.0

59.7

163.9

99.1

Activation Energy (kJ)

New Compound - HNBR

119

Compound N2

120

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - Epoxidised Natural

Hardness Compound N3 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N3 100°C

70°C

80°C

90°C

30.0

Tensile Strength (Mpa)

25.0

20.0

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

121

Compound N3

Elongation at Break Compound N3 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N3 100°C

70°C

80°C

90°C

8.00

Modulus at 100% (Mpa)

6.00

4.00

2.00

0.00 0

30

60

90

120

150

Heat Ageing Period (Days)

122

Ageing of Rubber - Accelerated Heat Ageing Test Results

88.7

>-79.6

-100.0

>251.1

>124.1

728.6

-458.0

-948.6

-100.0

Tensile Strength

Elongation at Break

100% Modulus

300% Modulus

T2

T10

Tg

Rebound Resilience

40 years at 23 °C

© Copyright 2001 Rapra Technology Limited

-100.0

1012.2

>124.1

>251.1

-100.0

>-79.6

88.7

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N3 (epoxidised natural)

-10%

5°C

5°C

5°C

50%

50%

-25%

-25%

25%

Measured Change

50.1 years

27.4 years

24.9 years

38.0 years

13.6 years

26.4 years

11.9 years

9.0 years

52.8 years

23 °C (time)

Arrhenius Predictions

5.3 years

4.1 years

3.9 years

4.8 years

624.2 days

3.8 years

581.1 days

557 days

7.4 years

40 °C (time)

102.2

85.8

84.7

94.2

94.2

88.1

91.3

80.7

89.1

Activation Energy (kJ)

New Compound - Epoxidised Natural

123

Compound N3

124

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - Chlorinated Polyethylene

Hardness Compound N4 100°C

150°C

160°C

130°C

140°C

100

Hardness (Micro-IRHD)

95

90

85

80 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N4 100°C

150°C

160°C

130°C

140°C

22.0

20.0

Tensile Strength (Mpa)

18.0

16.0

14.0

12.0

10.0

8.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

125

Compound N4

Elongation at Break Compound N4 100°C

150°C

160°C

130°C

140°C

250

Elongation at Break (%)

200

150

100

50

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N4 100°C

150°C

160°C

130°C

140°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

126

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-6.8

>57.7

Elongation at Break

100% Modulus

Rebound Resilience

Tg

T10

T2

0. 0

-4.0

Tensile Strength

300% Modulus

2.4

40 years at 23 °C

78.9

>57.7

-24.3

-21.5

4.8

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N4 (chlorinated polyethylene)

25%

-25%

-15%

10%

Measured Change

135.1 years

396.7 years

1692.4 years

1808.4 years

23 °C (time)

Arrhenius Predictions

23.4 years

59.8 years

205.6 years

223.2 years

40 °C (time)

79.6

85.8

95.6

94.9

Activation Energy (kJ)

New Compound - Chlorinated Polyethylene

127

Compound N4

128

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - Fluorocarbon

Hardness Compound N5 170°C

150°C

210°C

75

Hardness (Micro-IRHD)

73

71

69

67

65 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N5 150°C

210°C

170°C

18.0

Tensile Strength (Mpa)

16.0

14.0

12.0

10.0 0

20

40

60

80

100

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

129

Compound N5

Elongation at Break Compound N5 150°C

170°C

210°C

300.0

Elongation at Break (%)

250.0

200.0

150.0

100.0 0

20

40

60

80

100

80

100

Heat Ageing Period (Days)

Modulus at 100% Compound N5 150°C

170°C

210°C

10.00

Modulus at 100% (Mpa)

8.00

6.00

4.00

2.00

0.00 0

20

40

60

Heat Ageing Period (Days)

130

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

Rebound Resilience

Tg

T10

T2

300% Modulus

100% Modulus

Elongation at Break

Tensile Strength

Hardness

Property

0.0

0.0

40 years at 23 °C

0.0

0.0

40 years at 40 °C

WLF Predictions (%)

Compound N5 (fluorocarbon)

-15%

Measured Change 2.5 years

23 °C (time)

Arrhenius Predictions

299.8 days

40 °C (time)

50.6

Activation Energy (kJ)

New Compound - Fluorocarbon

131

Compound N5

132

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - Exxpro

Hardness Compound N6 80°C

90°C

70°C

100°C

Hardness (Micro-IRHD)

80

75

70

65 0

30

60

90

120

150

180

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N6 80°C

90°C

70°C

100°C

20.0

Tensile Strength (Mpa)

18.0

16.0

14.0

12.0

10.0 0

30

60

90 Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

133

Compound N6

Elongation at Break Compound N6 80°C

90°C

70°C

100°C

Elongation at Break (%)

250

200

150

100 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N6 80°C

90°C

70°C

100°C

12.00

Modulus at 100% (Mpa)

10.00

8.00

6.00

4.00

2.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

134

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-27.1

-36.7

0.0

Tensile Strength

Elongation at Break

100% Modulus

Rebound Resilience

Tg

T10

T2

300% Modulus

20.9

40 years at 23 °C

0.0

-39.5

-42.0

22.4

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N6 (Exxpro)

-15%

-15%

10%

Measured Change

86.5 days

2.5 years

3.1 years

23 °C (time)

Arrhenius Predictions

48.7 days

299.8 days

493.1 days

40 °C (time)

26.1

50.6

38.1

Activation Energy (kJ)

New Compound - Exxpro

135

Compound N6

136

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - Epichlorohydrin

Hardness Compound N7 80°C

90°C

100°C

70°C

95

Hardness (Micro-IRHD)

90

85

80

75 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N7 80°C

90°C

100°C

70°C

14.00

Tensile Strength (Mpa)

13.00

12.00

11.00

10.00

9.00

8.00 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

137

Compound N7

Elongation at Break Compound N7 80°C

90°C

100°C

70°C

400

Elongation at Break (%)

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N7 80°C

90°C

100°C

70°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

138

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

0.0

-77.7

232.6

Tensile Strength

Elongation at Break

100% Modulus

Rebound Resilience

Tg

T10

T2

300% Modulus

16.7

40 years at 23 °C

243.4

-82.3

0.0

20.5

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N7 (epichlorohydrin)

50%

-25%

10%

10%

Measured Change

19.4 years

4.7 years

24.3 years

11.1 years

23 °C (time)

Arrhenius Predictions

4.3 years

388.2 days

3.2 years

2.8 years

40 °C (time)

68.7

67.1

91.9

61.9

Activation Energy (kJ)

New Compound - Epichlorohydrin

139

Compound N7

140

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - EPDM

Hardness Compound N8 100°C

80°C

90°C

110°C

90

Hardness (Micro-IRHD)

85

80

75

70 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N8 100°C

80°C

90°C

110°C

20.0

Tensile Strength (Mpa)

19.0

18.0

17.0

16.0

15.0

14.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

141

Compound N8

Elongation at Break Compound N8 100°C

80°C

90°C

110°C

500

Elongation at Break (%)

400

300

200

100 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N8 100°C

80°C

90°C

110°C

10.00

Modulus at 100% (Mpa)

8.00

6.00

4.00

2.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

142

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

0.6

-47.9

82.6

>83.8

Tensile Strength

Elongation at Break

100% Modulus

300% Modulus

Rebound Resilience

Tg

T10

T2

0.0

40 years at 23 °C

>83.8

82.6

>-44.0

0.6

1.3

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N8 (EPDM)

10%

50%

-25%

5%

Measured Change

36.5 days

188.9 days

214.3 days

20.4 years

23 °C (time)

Arrhenius Predictions

18.3 days

125 days

104.3 days

6.2 years

40 °C (time)

31.3

18.7

32.6

53.8

Activation Energy (kJ)

New Compound - EPDM

143

Compound N8

144

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - EVA

Hardness Compound N9 100°C

150°C

170°C

160°C

140°C

100

Hardness (Micro-IRHD)

95

90

85

80

75 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N9 100°C

150°C

170°C

160°C

140°C

20.0

Tensile Strength (Mpa)

18.0

16.0

14.0

12.0

10.0

8.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

145

Compound N9

Elongation at Break CompoundN9 100°C

150°C

170°C

160°C

140°C

250

Elongation at Break (%)

200

150

100

50

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound N9 100°C

150°C

170°C

160°C

140°C

20.00

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

146

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

Rebound Resilience

Tg

T10

T2

0. 0

19.8

100% Modulus

300% Modulus

>-95.9

-1.7

Tensile Strength

Elongation at Break

8.9

40 years at 23 °C

0.0

29.9

>-95.9

-2.6

12.7

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound N9 (EVA)

5°C

50 %

-25%

10%

Measured Change

24.6 years

228.7 years

506 years

17 years

23 °C (time)

Arrhenius Predictions

9.3 years

47.2 years

82.5 years

7.1 years

40 °C (time)

44.3

71.6

82.3

39.7

Activation Energy (kJ)

New Compound - EVA

147

Compound N9

148

Ageing of Rubber - Accelerated Heat Ageing Test Results

New Compound - PU

Hardness Compound N10 80°C

90°C

70°C

100°C

100

90

Hardness (Micro-IRHD)

80

70

60

50

40

30 0

30

60

90

120

150

180

Heat Ageing Period (Days)

Tensile Strength Compound N10 80°C

90°C

70°C

100°C

20.0 18.0 16.0

Tensile Strength (Mpa)

14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0

2

4

6

8

10

12

14

16

18

20

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

149

Compound N10

Elongation at Break Compound N10 80°C

90°C

70°C

100°C

250.0

Elongation at Break (%)

200.0

150.0

100.0

50.0

0.0 0

2

4

6

8

10

12

14

16

18

20

Heat Ageing Period (Days)

Modulus at 100% Compound N10 80°C

90°C

70°C

100°C

10.0

Modulus at 100% (Mpa)

8.0

6.0

4.0

2.0

0.0 0

2

4

6

8

10

12

14

16

18

20

Heat Ageing Period (Days)

150

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

>-69.0

-84.0

Elongation at Break

100% Modulus

Rebound Resilience

Tg -10%

5°C

T10

-25%

-25%

-25%

-25%

18.5 days

545.2 days

83.1 days

280.4 days

12 days

9.6 days

59.7 days

23 °C (time)

Arrhenius Predictions Measured Change

5°C

-100.0

-84.0

>-69.0

>-86.4

14.9

40 years at 40 °C

T2

-100.0

-42.9

Tensile Strength

300% Modulus

6.8

40 years at 23 °C

WLF Predictions (%)

Hardness

Property

Compound N10 (PU)

8.7 days

103.7 days

30.3 days

75.8 days

6.4 days

5.7 days

25.5 days

40 °C (time)

34.6

75.3

45.8

59.4

28.3

23.8

38.6

Activation Energy (kJ)

New Compound - PU

151

Compound N10

152

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - EPR

Hardness Compound P1 150°C

170°C

160°C

140°C

100

95

Hardness (Micro-IRHD)

90

85

80

75

70

65 0

10

20

30

40

50

60

70

80

90

100

80

90

Heat Ageing Period (Days)

Tensile Strength Compound P1 150°C

170°C

160°C

140°C

20.0

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

10

20

30

40

50

60

70

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

153

Compound P1

Elongation at Break Compound P1 150°C

170°C

160°C

140°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

10

20

30

40

50

60

70

80

90

90

100

Heat Ageing Period (Days)

Modulus at 100% Compound P1 150°C

170°C

160°C

140°C

10.00

Modulus at 100% (Mpa)

8.00

6.00

4.00

2.00

0.00 0

10

20

30

40

50

60

70

80

Heat Ageing Period (Days)

154

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-47.6

>300.5

Elongation at Break

100% Modulus

Rebound Resilience

Tg

T10

T2

0.0

18.2

Tensile Strength

300% Modulus

-1.4

40 years at 23 °C

0.0

>300.5

-54.0

10.6

-1.4

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound P1 (EPR)

100%

-25%

-25%

15%

Measured Change

6.0 years

66.2 days

6266360.7 yrs

1760.5 years

23 °C (time)

Arrhenius Predictions

685.2 days

36 days

234097 years

291.6 years

40 °C (time)

52.8

27.7

149.1

81.6

Activation Energy (kJ)

Participant Compound - EPR

155

Compound P1

156

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Siloxane Cellular Material

Hardness Compound P2 150°C

170°C

210°C

40

Hardness (Shore 00)

35

30

25

20 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P2 150°C

170°C

210°C

0.500

Tensile Strength (Mpa)

0.400

0.300

0.200

0.100

0.000 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

157

Compound P2

Elongation at Break Compound P2 150°C

170°C

210°C

140.0

120.0

Elongation at Break (%)

100.0

80.0

60.0

40.0

20.0

0.0 0

30

60

90

120

150

180

Heat Ageing Period (Days)

158

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

Rebound Resilience

Tg

T10

T2

300% Modulus

100% Modulus

Elongation at Break

Tensile Strength

Hardness

Property

0.0

18.5

40 years at 23 °C

0.0

22.2

40 years at 40 °C

WLF Predictions (%)

Compound P2 (siloxane cellular material) Measured Change

23 °C (time)

Arrhenius Predictions 40 °C (time)

Activation Energy (kJ)

Participant Compound - Siloxane Cellular Material

159

Compound P2

160

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Medium Nitrile Rubber

Hardness Compound P3 100°C

80°C

90°C

100

Hardness (Micro-IRHD)

95

90

85

80

75 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P3 100°C

80°C

90°C

70°C

22.0

Tensile Strength (Mpa)

20.0

18.0

16.0

14.0

12.0

10.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

161

Compound P3

Elongation at Break Compound P3 100°C

80°C

90°C

70°C

400

Elongation at Break (%)

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P3 100°C

80°C

90°C

70°C

25.00

Modulus at 100% (Mpa)

20.00

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

162

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

26.1

-88.5

>83.0

Tensile Strength

Elongation at Break

100% Modulus

-62.3

-120.5

T10

Tg

Rebound Resilience

3.0

T2

300% Modulus

22.0

40 years at 23 °C

-198.9

-111.6

87.9

>83.0

>-41.4

35.0

22.0

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound P3 (medium nitrile rubber)

5°C

50%

-25%

10%

15%

Measured Change

11.2 years

8.6 years

53.3 years

4.0 years

117.6 years

23 °C (time)

Arrhenius Predictions

4.1 years

2.5 years

5.6 years

525.1 days

20.3 years

40 °C (time)

45.2

55.8

102.2

47.0

79.6

Activation Energy (kJ)

Participant Compound - Medium Nitrile Rubber

163

Compound P3

164

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Nitrile Rubber

Hardness Compound P4 100°C

80°C

90°C

70°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P4 100°C

80°C

90°C

70°C

30.0

Tensile Strength (Mpa)

25.0

20.0

15.0

10.0

5.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

165

Compound P4

Elongation at Break Compound P4 100°C

80°C

90°C

70°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P4 100°C

80°C

90°C

70°C

25.00

Modulus at 100% (Mpa)

20.00

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

166

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

>-72.2

177.9

87.6

Elongation at Break

100% Modulus

300% Modulus

-10%

Rebound Resilience

10%

100%

-25%

-25%

10%

8.8 days

597.4 days

153.1 days

3.0 years

327 days

9.6 years

5.3 years

23 °C (time)

Arrhenius Predictions Measured Change

5°C -58.6

78.3

559.9

>-72.2

>7.3

49.3

40 years at 40 °C

Tg

T10

-51.4

>7.3

Tensile Strength

T2

49.3

40 years at 23 °C

WLF Predictions (%)

Hardness

Property

Compound P4 (nitrile rubber)

7.1 days

421.9 days

47.5 days

495 days

84.4 days

405.6 days

1.9 years

40 °C (time)

9.3

15.8

53.1

36.8

61.5

97.9

45.7

Activation Energy (kJ)

Participant Compound - Nitrile Rubber

167

Compound P4

168

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - EPDM

Hardness Compound P5 150°C

170°C

160°C

140°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

50

60

Heat Ageing Period (Days)

Tensile Strength Compound P5 150°C

170°C

160°C

140°C

20.0

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

10

20

30

40

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

169

Compound P5

Elongation at Break Compound P5 150°C

170°C

160°C

140°C

Elongation at Break (%)

150

100

50

0 0

10

20

30

40

50

60

Heat Ageing Period (Days)

Modulus at 100% Compound P5 150°C

170°C

160°C

140°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

10

20

30

40

Heat Ageing Period (Days)

170

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

Rebound Resilience

Tg

T10

T2

300% Modulus

100% Modulus

>-87.5

0.0

Tensile Strength

Elongation at Break

5.5

40 years at 23 °C

>-87.5

0.0

19.3

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound P5 (EPDM)

25%

-25%

-25%

15%

Measured Change

5.9 years

338.5 years

2.9E+06 years

2230.8 years

23 °C (time)

Arrhenius Predictions

622.7 days

50.5 years

1.0E+05 years

339.3 years

40 °C (time)

56.3

86.3

152.7

85.4

Activation Energy (kJ)

Participant Compound - EPDM

171

Compound P5

172

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Vamac G

Hardness Compound P6 150°C

170°C

160°C

140°C

100

Hardness (Micro-IRHD)

95

90

85

80

75 0

30

60

90

120

Heat Ageing Period (Days)

Tensile Strength Compound P6 150°C

170°C

160°C

140°C

14.0

Tensile Strength (Mpa)

13.0

12.0

11.0

10.0 0

30

60

90

120

150

180

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

173

Compound P6

Elongation at Break Compound P6 150°C

170°C

160°C

140°C

300

Elongation at Break (%)

250

200

150

100

50

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P6 150°C

170°C

160°C

140°C

15.00

Modulus at 100% (Mpa)

13.00

11.00

9.00

7.00

5.00 0

30

60

90

120

Heat Ageing Period (Days)

174

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

0.0

100% Modulus

Rebound Resilience

Tg

T10

T2

300% Modulus

0.0

6.4

40 years at 23 °C

0.0

0.0

9.0

40 years at 40 °C

WLF Predictions (%)

Elongation at Break

Tensile Strength

Hardness

Property

Compound P6 (Vamac G)

50%

-25%

15%

Measured Change

1126406.5 years

2668132.7 years

341864.8 years

23 °C (time)

Arrhenius Predictions

67897.0 years

111474.2 years

21078.2 years

40 °C (time)

127.4

144.1

126.4

Activation Energy (kJ)

Participant Compound - Vamac G

175

Compound P6

176

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - W Type Polychloroprene

Hardness Compound P7 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P7 100°C

70°C

80°C

90°C

25.0

Tensile Strength (Mpa)

20.0

15.0

10.0

5.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

177

Compound P7

Elongation at Break Compound P7 100°C

70°C

80°C

90°C

400

Elongation at Break (%)

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P7 100°C

70°C

80°C

90°C

20.00

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

178

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-58.6

140.9

Elongation at Break

100% Modulus

Rebound Resilience

-485.2

5°C

-54.8

Tg

5°C

100%

-25%

-15%

25%

88.5 years

95.3 years

68.6 years

52.8 years

23.3 years

4094.8 years

64.7 years

23 °C (time)

Arrhenius Predictions Measured Change

5°C

-226.3

>315.2

>-97.4

-9.2

56.3

40 years at 40 °C

T10

T2

-63.2

-17.6

Tensile Strength

300% Modulus

45.3

40 years at 23 °C

WLF Predictions (%)

Hardness

Property

Compound P7 (W type polychloroprene)

10.6 years

12.3 years

9.1 years

7.1 years

3.4 years

112.5 years

9.3 years

40 °C (time)

96.4

93.0

91.5

90.8

86.7

163.1

87.9

Activation Energy (kJ)

Participant Compound - W Type Polychloroprene

179

Compound P7

180

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Natural Rubber

Hardness Compound P8 100°C

70°C

80°C

90°C

100

Hardness (Micro-IRHD)

90

80

70

60

50

40 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P8 100°C

70°C

80°C

90°C

Tensile Strength (Mpa)

15.0

10.0

5.0

0.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

181

Compound P8

Elongation at Break Compound P8 100°C

70°C

80°C

90°C

700

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P8 100°C

70°C

80°C

90°C

5.00

Modulus at 100% (Mpa)

4.00

3.00

2.00

1.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

182

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

-31.2

-84.3

>286.7

20.2

Tensile Strength

Elongation at Break

100% Modulus

300% Modulus

Rebound Resilience

Tg

T10

T2

46.3

40 years at 23 °C

59.3

>286.7

>-72.4

-73.8

85.2

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound P8 (natural rubber)

5°C

25%

100%

-25%

-25%

25%

Measured Change

1558.9 years

33.9 years

3.4 years

18 years

218.8 years

9.4 years

23 °C (time)

Arrhenius Predictions

63.7 years

2.3 years

321.6 years

2.7 years

17.3 years

2.3 years

40 °C (time)

145.1

122.8

61.8

85.6

115.2

64.2

Activation Energy (kJ)

Participant Compound - Natural Rubber

183

Compound P8

184

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Santoprene 101 55 V185

Hardness Compound P9 100°C

140°C

170°C

150°C

160°C

100

Hardness (Micro-IRHD)

90

80

70

60

50 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P9 100°C

140°C

170°C

150°C

160°C

8.00

Tensile Strength (Mpa)

6.00

4.00

2.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

185

Compound P9

Elongation at Break Compound P9 100°C

140°C

170°C

150°C

160°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P9 100°C

140°C

170°C

150°C

160°C

5.00

Modulus at 100% (Mpa)

4.00

3.00

2.00

1.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

186

Ageing of Rubber - Accelerated Heat Ageing Test Results

-25.3

Tensile Strength

© Copyright 2001 Rapra Technology Limited

0.0

300% Modulus

-4.5

0.0

Tg

Rebound Resilience

T10

T2

0.0

100% Modulus

Elongation at Break

47.1

40 years at 23 °C

0.0

-7.0

-0.2

0.0

-41.9

47.1

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound P9 (Santoprene 101 55 V185)

-25%

-25%

10%

Measured Change

201192.6 yrs

688079.1 yrs

119209.9 yrs

23 °C (time)

Arrhenius Predictions

12722.4 yrs

32237.6 yrs

10874.1 yrs

40 °C (time)

125.3

138.9

108.6

Activation Energy (kJ)

Participant Compound - Santoprene 101 55 V185

187

Compound P9

188

Ageing of Rubber - Accelerated Heat Ageing Test Results

Participant Compound - Nitrile Rubber

Hardness Compound P10 100°C

80°C

90°C

70°C

100

Hardness (Micro-IRHD)

95

90

85

80

75 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Tensile Strength Compound P10 100°C

80°C

90°C

70°C

16.0

Tensile Strength (Mpa)

14.0

12.0

10.0

8.0

6.0 0

30

60

90

120

Heat Ageing Period (Days)

© Copyright 2001 Rapra Technology Limited

189

Compound P10

Elongation at Break Compound P10 100°C

80°C

90°C

70°C

600

Elongation at Break (%)

500

400

300

200

100

0 0

30

60

90

120

150

180

150

180

Heat Ageing Period (Days)

Modulus at 100% Compound P10 100°C

80°C

90°C

70°C

Modulus at 100% (Mpa)

15.00

10.00

5.00

0.00 0

30

60

90

120

Heat Ageing Period (Days)

190

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

>-97.7

80.7

130.0

Elongation at Break

100% Modulus

300% Modulus

Rebound Resilience

Tg

T10

-32.1

-10.7

Tensile Strength

T2

19.5

40 years at 23 °C

-42.9

189.6

180.4

>-97.7

24.6

22.0

40 years at 40 °C

WLF Predictions (%)

Hardness

Property

Compound P10 (nitrile rubber)

5°C

5°C

50%

50%

-25%

-10%

10%

Measured Change

7.3 years

7.5 years

7.9 years

22.1 years

29.6 years

37.2 days

11.0 years

23 °C (time)

Arrhenius Predictions

2.7 years

3.4 years

662.6 days

3.4 years

4.6 years

23.4 days

2.7 years

40 °C (time)

45.6

35.5

66.8

85.2

84.1

21.0

63.7

Activation Energy (kJ)

Participant Compound - Nitrile Rubber

191

Compound P10

192

Ageing of Rubber - Accelerated Heat Ageing Test Results

APPENDIX 3 COMPRESSION SET RESULTS

© Copyright 2001 Rapra Technology Limited

193

Appendix 3

194

Ageing of Rubber - Accelerated Heat Ageing Test Results

© Copyright 2001 Rapra Technology Limited

3.3

10.3

11.2

13.0

12.4

13.4

6.5

20.0

5.0

6.3

8.5

7.8

9.9

6.0

55.1

30.5

C

D

E

F

G

H

J

K

L

M

N

P

R

S

T

W

9.4

12.5

B

X

7.7

1 week

11.2

33.8

62.0

7.4

10.4

9.3

15.9

9.1

6.7

25.0

7.3

17.8

16.8

19.2

17.1

21.5

6.8

20.5

13.3

5 weeks

23 °C

A

Compound Reference

80.6

73.7

23.4

23.8

56.7

39.5

39.3

37.6

85.1

48.9

37.4

56.7

1 week

97.4

86.3

40.6

42.0

67.0

64.1

59.3

57.7

95.3

68.3

57.1

70.9

5 weeks

70 °C

16.7

102.2

88.4

67.6

51.7

60.6

48.1

42.6

20.9

84.6

76.8

23.5

57.5

25.1

58.8

96.3

71.6

52.7

71.9

1 week

29.3

102.2

95.3

81.5

62.5

77.9

68.7

60.0

40.9

92.9

86.3

38.7

72.1

41.7

72.3

98.0

78.7

68.5

81.9

5 weeks

100 °C

65.1

68.8

49.8

56.7

1 week

91.6

100.0

93.8

92.1

5 weeks

140 °C

56.6

94.6

1 week

88.9

104.1

5 weeks

150 °C

Table 1. Compression Set Results (%)

60.0

1 week

106.3

5 weeks

160 °C 1 week

5 weeks

200 °C

Compression Set Results

195

196

21.3

31.7

14.4

22.3

0.1

5.6

13.0

2.1

8.0

10.8

20.7

12.7

18.2

N8

N9

N10

P1

P2

P3

P4

P5

P6

P7

P8

P9

P10

9.4

N5

9.9

19.0

N4

N7

10.4

N3

17.8

24.4

N2

N6

5.9

1 week

27.1

16.2

29.0

18.3

15.6

4.1

19.2

12.8

2.5

34.1

26.8

45.5

32.5

13.0

23.6

10.8

29.9

15.6

33.6

9.1

5 weeks

23 °C

N1

Compound Reference

35.9

72.5

42.4

20.4

48.7

38.7

1 week

49.3

86.3

64.3

38.0

65.6

55.6

5 weeks

70 °C

50.5

90.7

72.4

60.4

32.0

30.2

44.3

53.7

34.0

39.8

68.3

63.2

39.3

12.7

1 week

69.2

96.0

85.0

69.3

44.4

44.7

63.2

90.7

58.2

63.3

81.1

97.1

63.7

23.9

5 weeks

100 °C

45.6

62.6

63.2

35.1

75.6

9.8

47.7

1 week

63.3

93.5

96.4

47.6

90.2

22.1

84.9

5 weeks

140 °C

72.1

9.5

50.9

95.9

33.2

1 week

80.0

16. 7

65.1

102.8

71.8

5 weeks

150 °C

Table 1. Compression Set Results (%) Continued

70.4

59.7

64.2

88.4

1 week

77.5

84. 3

75.3

109.4

5 weeks

160 °C

16.1

104.3

81.4

42. 3

1 week

27.5

111.6

120.1

72.4

5 weeks

200 °C

Appendix 3

Ageing of Rubber - Accelerated Heat Ageing Test Results

Compression Set Results

Table 2. Predicted Compression Set Results (%) Compound Reference

Natural Results

Prediction Results

1 year

40 years

1 year

40 years

A

46.8

100.0

27.0

45.9

B

58.2

92.0

37.8

57.9

C

35.3

71.1

18.1

38.6

D

72.8

98.2

49.2

76.3

E

42.2

81.9

29.7

45.4

F

21.1

60.6

31.8

47.0

G

42.9

92.9

25.3

35.6

H

24.0

74.3

26.1

36.0

J

24.0

75.0

10.1

13.2

K

38.2

79.5

33.6

43.0

L

19.4

59.0

10.1

14.8

M

32.8

78.8

15.2

23.6

N

32.8

81.1

34.6

58.5

P

39.2

77.9

12.2

15.6

R

26.2

81.9

13.3

16.1

S

15.7

40.8

10.0

13.3

T

83.9

97.0

71.2

78.5

W

69.9

85.0

39.1

44.3

X

45.9

72.4

14.4

18.0

© Copyright 2001 Rapra Technology Limited

197

Appendix 3

Table 2. Predicted Compression Set Results (%) Continued Compound Reference

Prediction Results 1 year

40 years

N1

16.6

27.5

N2

49.4

64.5

N3

26.6

40.8

N4

50.5

69.9

N5

12.9

15.4

N6

34.2

45.9

N7

19.0

26.5

N8

52.7

71.1

N9

66.1

81.4

N10

53.2

76.9

P1

54.9

73.3

P2

74.4

99.6

P3

35.3

65.5

P4

31.6

46.5

P5

10.4

23.3

P6

35.5

60.9

P7

35.2

55.8

P8

43.8

59.0

P9

22.5

29.9

P10

43.9

61.3

198

Ageing of Rubber - Accelerated Heat Ageing Test Results

Compression Set Results

Compression Set Compound N1 23 °C

100 °C

150 °C

100.0 90.0 80.0

Compression Set (%)

70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 0.0

1.0

2.0

3.0

4.0

5.0

6.0

5.0

6.0

Weeks

Figure 1

Compression Set Compound N2 23 °C

100 °C

150 °C

120.0 110.0 100.0

Compression Set (%)

90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 0.0

1.0

2.0

3.0

4.0

Weeks

Figure 2

© Copyright 2001 Rapra Technology Limited

199

Appendix 3

200

Ageing of Rubber - Accelerated Heat Ageing Test Results

APPENDIX 4 EXAMPLE GRAPHS

© Copyright 2001 Rapra Technology Limited

201

Appendix 4

202

Ageing of Rubber - Accelerated Heat Ageing Test Results

Example Graphs

Glass Transition Temperature Compound A 100°C

70°C

80°C

90°C

-25.00

Glass Transition Temperature (°C)

0

10

20

30

40

50

60

150

180

-30.00

-35.00

-40.00

-45.00 Heat Ageing Period (Days)

Figure 1 Tan Delta Compound M 100°C

70°C

80°C

90°C

0.300

Tand Delta at 23°C

0.200

0.100

0.000 0

30

60

90

120

Heat Ageing Period (Days)

Figure 2

© Copyright 2001 Rapra Technology Limited

203

Appendix 4

Tan Delta Compound A 100°C

70°C

80°C

90°C

0.300

Tan Delta at 23°C

0.250

0.200

0.150

0.100 0

10

20

30

40

50

60

Heat Ageing Period (Days)

Figure 3

Arrhenius Plot for Change in Elongation at Break with Time Compound G

Time (days) to end point

1000.000

100.000

10.000

1.000 0.00265

0.00270

0.00275

0.00280

0.00285

0.00290

0.00295

Reciprocal Temperature (kelvin)

Figure 4

204

Ageing of Rubber - Accelerated Heat Ageing Test Results

Example Graphs

Arrhenius Plot for Change in Elongation at Break with Time Compound N9

Time (days) to end point

1000.000

100.000

10.000

1.000 0.00220

0.00225

0.00230

0.00235

0.00240

0.00245

0.00250

0.00255

0.00260

0.00265

0.00270

0.00275

Reciprocal Temperature (kelvin)

Figure 5

Arrhenius Plot for Change in Hardness with Time Compound B for 10% Change

Time (days) to end point

1000.000

100.000

10.000

1.000 0.002650

0.002700

0.002750

0.002800

0.002850

0.002900

0.002950

Reciprocal Temperature (kelvin)

Figure 6

© Copyright 2001 Rapra Technology Limited

205

Appendix 4

Arrhenius Plot for Change in Hardness with Time Compound R

Time (days) to end point

1000

100

10

1 0.00265

0.00270

0.00275

0.00280

0.00285

0.00290

0.00295

Reciprocal Temperature (Kelvin)

Figure 7

WLF Temperature Shifted Elongation at Break - Compound M Reference Temperature = 40°C 100°C

70°C

80°C

90°C

500

Elongation at break (%)

400

300

200

100

0 1

10

100

1,000

Time (Months)

Figure 8

206

Ageing of Rubber - Accelerated Heat Ageing Test Results

Example Graphs

WLF Temperature Shifted Elongation at Break - Compound K Reference Temperature = 23°C 80°C

90°C

100°C

70°C

120°C

700 600 Elongation at break (%)

500 400 300 200 100 0 0

1

10

100

1,000

Time (Months)

Figure 9

WLF Temperature Shifted Hardness - Compound B Reference Temperature = 23°C 100°C

70°C

80°C

90°C

100 95

Hardness (Micro-IRHD)

90 85 80 75 70 65 60 0

1

10

100

1,000

Time (Months)

Figure 10

© Copyright 2001 Rapra Technology Limited

207

Appendix 4

WLF Temperature Shifted Hardness - Compound R Reference Temperature = 23°C 100°C

70°C

80°C

90°C

100 95

Hardness (Micro-IRHD)

90 85 80 75 70 65 60 55 50 1

10

100

1,000

Time (Months)

Figure 11

208

Ageing of Rubber - Accelerated Heat Ageing Test Results

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