Enhanced Compatibility and Thermo-Oxidative Stability of Silicone Rubber/Ethylene–Propylene Terpolymer Composites via In Situ Interface Coupling

The low surface energy of silicone rubber makes it difficult to blend with conventional rubbers. In this study, we employed mercapto silicone resin (SH-MTQ) for the reactive compatibilization of silicone rubber/ethylene–propylene terpolymer (SEP) composites. The different reactivities of SH-MTQ with silicone rubber and ethylene–propylene terpolymer ensure an efficient enhancement of compatibility. After modification, smaller-sized domains and a more homogeneous distribution emerge in composites, leading to improved mechanical properties. Notably, 6%MTQSEP exhibits a remarkable 102% increase in tensile strength and a 66% improvement in elongation at the break. A possible mechanism for the increased compatibility of SEP composites with SH-MTQ resin is proposed. In addition, the thermo-oxidative stability of composites is significantly enhanced. After being aged at 150 °C for 3 days, the color and mechanical properties of the composites almost remain unchanged. In summary, SH-MTQ has the potential to be a functional filler for the preparation of high-performance SEP composites with outstanding mechanical properties and excellent anti-aging ability.