The effect of environmental factors on degradation and recovery characteristics of RTV silicone rubber

Room temperature vulcanized (RTV) silicone rubber has been widely used to coat porcelain insulators to render water repellency to prevent formation of water filming on the surface and thus to suppress the leakage current and consequently flashover. However, the electrical property and its hydrophobicity of RTV silicone rubber coating under outdoor conditions may be influenced by many environmental factors. In this study various treatments, such as salt-fog, salt water immersion and UV irradiation were applied to the samples to investigate the change of the electrical property and hydrophobicity. As a result the leakage current increased and contact angle decreased as the degradation time is longer. But the degraded RTV silicone rubber has recovered its hydrophobicity during drying time in ambient condition because LMW (low molecular weight) silicone fluid diffused from the bulk to the surface.