Study on the Influence Mechanism of Thermal‐Oxidative Aging Temperature on the Degradation Behavior and Properties of Phenyl Silicone Rubber

ABSTRACT In this study, vulcanized phenyl silicone rubber was subjected to thermal oxidative aging at 180°C and 210°C. The mechanical properties, structural integrity of the main and side chains, thermal stability, and apparent activation energy of the samples before and after aging were characterized using a tensile testing machine, Fourier‐transform infrared (FTIR) spectrometer, and thermogravimetric analyzer (TGA). Mechanical testing revealed that, at 180°C, the elongation at break of phenyl silicone rubber decreased gradually with aging time, while the tensile strength initially increased and subsequently declined. In contrast, at 210°C, both the elongation at break and tensile strength exhibited a rapid decrease. FTIR analysis indicated that the observed changes in mechanical properties are primarily associated with the degradation of the polymer main chain. TGA analysis demonstrated that the thermal oxidative aging process proceeds through two distinct decomposition stages. Furthermore, the apparent activation energy ( Ea ) initially decreases with increasing conversion and then gradually increases, reflecting a shift in the dominant degradation mechanism from side‐chain oxidation to main‐chain scission.