GB/T 7142-2002 in English

《GB/T 7142-2002塑料长期热暴露后时间-温度极限的测定》由TC15（全国塑料标准化技术委员会）归口，TC15SC5（全国塑料标准化技术委员会老化方法分会）执行，主管部门为中国石油和化学工业联合会。
本标准规定了评价塑料经长期热暴露后耐热性能的原理和方法。本标准使用的耐热性术语适用于在空气中进行的试验。本标准不适用于试样在非空气环境下和/或施加应力下的耐热性能的评价。本标准中的塑料热老化研究的唯一根据是：热老化一定时间后会导致性能变化。所要研究的性能通常在老化温度回复到室温后进行测试。在热老化过程中，塑料的各种性能是以不同的速率变化的。能够比较各种塑料的热老化性能，判断的标准取决于所要研究的性能的类型和容许限定值。在本标准应用中，假定在引起预定性能变化所需时间的对数与相应的绝对温度倒数之间存在近似直线关系（阿累尼乌斯定律）。在研究温度范围内，被试塑料不应发生转变，特别是一级转变。

Scope

1.1 This standard specifies the principles and methods for evaluating the heat resistance of plastics after long-term heat exposure. 1.2 The heat resistance term used in this standard applies to the test conducted in air. This standard does not apply to the evaluation of the heat resistance of samples in a non-air environment and/or under applied stress. 1.3 The only basis for the thermal aging research of plastics in this standard is that thermal aging will lead to performance changes after a certain period of time. The properties to be investigated are usually tested after the aging temperature has returned to room temperature. During heat aging, various properties of plastics change at different rates. The thermal aging performance of various plastics can be compared, and the judgment standard depends on the type of performance to be studied and the allowable limit value. 1.4 In the application of this standard, it is assumed that there is an approximately linear relationship (Arrhenius law) between the logarithm of the time required to cause a change in a predetermined property and the corresponding reciprocal of the absolute temperature. A shift should occur, especially a first-order shift.