Impacts of Silicone Grease Swelling on Surface and Interface Insulation Performance and Trap Characteristics of Grafted EPDM

The swelling of rubber caused by silicone grease significantly accelerates the deterioration of the electrical properties of cable accessories, particularly at the surface and interface regions. This study investigates the impact of swelling aging on the insulation performance and trap characteristics of ethylene propylene diene monomer (EPDM) modified by the voltage stabilizer 4-allyloxy-2-hydroxybenzophenone (AOHBP). Physicochemical characterization, electrical measurements, and molecular dynamics simulations were employed to analyze the evolution of EPDM insulation performance under silicone grease swelling. Results indicate that the swelling process alters the trap distribution and reduces the density of deep traps, thereby weakening the material's insulation performance. However, compared to unmodified samples, the grafted EPDM exhibits a higher EPDM/XLPE interfacial breakdown strength and improved anti-swelling capability. Mechanism analysis reveals that the grafted AOHBP introduces steric hindrance, which inhibits the diffusion of silicone grease molecules into the EPDM matrix, effectively alleviating the degradation of surface and interface insulation performance induced by swelling.