Analyzing the Role of Filler Interface on the Erosion Performance of Filled RTV Silicone Rubber under DC Dry-band Arcing

Abstract

This study investigates the role of filler interface on suppressing the erosion of room temperature vulcanized silicone rubber composites filled with fumed silica, nano alumina trihydrate and sub-micron hexagonal boron nitride fillers during DC dry-band arcing. Simultaneous thermogravimetric-differential thermal analyses indicate a superior effect for fumed silica in suppressing the depolymerization of silicone rubber and promoting radical based crosslinking. This can be attributed to favorable interactions at the fumed silica-silicone interface tethering the siloxane chains. At low filler loading of alumina trlhydrate, water of hydration has insignificant effects on suppressing depolymerization compared to that influenced by fumed silica's interface at equal filler loading. Similarly, incorporating thermally conductive boron nitride filler in silicone rubber does not show improvement in the depolymerization rate compared to that influenced by fumed silica. These findings correlate with the +DC inclined plane tracking and erosion test outcomes indicating superior erosion performance for the fumed silica filled composite. This accordingly supports the influential role of the filler interface over the water of hydration and thermal conductivity enhancement in suppressing the DC erosion of silicone rubber composites under the test conditions of this study. A statistical boxplot analysis technique is introduced to elucidate the inception of the stable dry-band arc in terms of the change in leakage current randomness during the +DC inclined plane tracking and erosion test. The boxplots reveal a slow inception of the stable dry-band arc with the fumed silica filled composite delaying the erosion of silicone rubber during the test. This finding confirms the influence of the filler interface over composite thermal conductivity in suppressing erosion of silicone rubber under DC dry-band arcing.