Combustion Performance of Silicone Rubber Polymer Insulation Material Under Damp‐Heat Ageing Conditions: Molecular Insights Into the Effects of Structural Changes on Macroscopic Properties

ABSTRACT Silicone rubber (SR), an organic silicon polymer material, is known for its excellent heat resistance and mechanical properties. It is widely used in composite insulators and cable accessory materials. However, the ageing caused by humidity and heat significantly impacts its performance, an issue that cannot be ignored. This paper investigates the changes in the combustion performance of SR insulation materials during wet‐heat ageing, focussing on both experimental and simulation‐based approaches. Through macroscopic experiments, SR samples underwent wet‐heat ageing tests, and the changes in combustion phenomena, oxygen index, afterflame time, and microstructure with varying ageing degrees were studied. Molecular simulation techniques were employed to uncover the mechanism by which structural changes during wet‐heat ageing affect SR's combustion performance. The results reveal that as the ageing degree increases, the colour of the SR sample remains largely unchanged, but the surface shows an increasing number of wrinkles, holes, and traces of filler precipitation. The combustion characteristics of SR exhibit a noticeable upward trend as the ageing degree deepens. Using the ReaxFF force field, five distinct structural changes during wet‐heat ageing were identified and categorised from ageing degree 0 to ageing degree 5. As the ageing degree increases, the spatial ductility and thermal stability of SR change significantly, which in turn alters the intermolecular forces within the material. These structural changes lead to improved combustion performance of SR. This paper provides theoretical guidance for understanding the evolution of SR's performance during ageing and its implications for future research and material development.