Synergistic Effects of Amine-Containing Antioxidants on the Aging Performances of Ethylene Propylene Diene Rubber

In this study, two types of amine-containing antioxidants composed of 2-mercaptobenzimidazole zinc (MBZ) and 4,4 '-bis(alpha, alpha-dimethylbenzyl) diphenylamine (445) were used to improve the thermo-oxidative aging resistance of ethylene propylene diene rubber (EPDM). The synergistic effects on the performances of EPDM and the corresponding aging mechanism were investigated by FTIR, tensile test, differential scanning calorimetry (DSC), rotary rheometer and other equipment. The results showed that the hardness increased gradually with the increasing aging time regardless of the type of antioxidants. Compared with the EPDM without antioxidants, the elongation retention of those samples with MBZ or 445 improved obviously. Additionally, the sample with the MBZ/445 complex showed the highest retention values at the same aging time. The antioxidative mechanisms were further analyzed by carbonyl index, activation energy and oxidation induction time, respectively. Results indicated that the degree of oxidation of EPDM using the MBZ/445 complex was much lower than other control systems during the aging process. As a result, the MBZ/445 complex was a favorable antioxidative additive for EPDM.