Influence of Silicone Rubber Content on the Aging of <scp>RTV</scp> ‐ <scp>SiR</scp> Coating

ABSTRACT The service life of glass and porcelain insulators widely used in overhead transmission lines is constrained by the durability of room temperature vulcanized silicone rubber (RTV‐SiR) anti‐pollution flashover coatings. To enhance aging resistance and evaluation, this study conducted accelerated thermal‐oxidative aging experiments on coatings with different silicone rubber (SiR) contents to evaluate the variations in their structural, electrical, and compositional evolution. The results show a progressive aging in surface morphology, characterized by crack propagation, pore formation, and declining hydrophobicity, accompanied by an overall increase in bulk conductivity. The SiR content follows a three‐stage aging pattern, namely the stabilization stage, the acceleration stage, and the degradation plateau, corresponding respectively to crosslinking enhancement, chain scission, and network failure. The coating with higher initial SiR content exhibits better aging resistance due to a higher proportion of thermally stable chemical crosslinks and fewer thermally sensitive physical crosslinks. The stage‐dependent variation in SiR content demonstrates a strong correlation with aging progression, offering a reference for service life prediction and maintenance planning.