Ranking of rubber vulcanizates used as seals based on effect of accelerated aging

Technical properties such as hardness, tensile strength, ultimate elongation, and rebound resilience are popular in quality control, but the trend in these properties shows a generalized picture of the structure-property relations. Test specimens were aged in hot air by systematically varying the time and temperature from 24 to 96 h at 70 to 100 degreesC. For an effective comparison the observed values were plotted as a function of time, temperature, and formulations. The data thus obtained were correlated with shelf-aging in particular cases, and it was observed that aging at 100 degreesC for 24 h could be used for such formulations. A "sulfur donor" system cured nitrile-butadiene rubber (NBR) vulcanizate and an ethylene-propylene-diene (EPDM) vulcanizate showed the best retention of properties. Although the SEM micrograph of the NBK. was in agreement with this observation, the EPDM was not. (C) 2000 John Wiley & Sons, Inc.