Nitrile-butadiene rubber (NBR) has been widely used in in- dustry over the years [1e5]. NBR has great potential in seals in- dustry because of its low cost, excellent resistance to oil, fuels and greases, low abrasion rate, and good processability [1,2]. However, the aging resistance of NBR is sensitive to environmental factors because of the presence of unsaturated back-bone of the butadiene part. A degrading environment, such as one characterized by high temperature, high humidity, strong light, low temperature, or a mechanical load, can have a profound effect on durability of NBR [3e9]. For instance, in oxygen containing environments, the hard- ness, morphology and mechanical properties of NBR rubber can be greatly affected by oxidation, especially at relatively high temper- atures [10e14]. In fact, the process of rubber degradation is very slow in an actual working environment, so it takes a long time to obtain rubber with degradation behaviors. Thus, accelerated aging tests are typically used to study the degradation of rubbers in a comparatively short time [15].
Thermal aging of the NBR rubber in air is an extremely complex