Effect of inorganic fillers type and size on dry band arcing erosion of silicone rubber composites

Abstract This paper analyzes the impact of particle type, surface treatment and particle size of different inorganic fillers on the suppression of AC and DC dry band arcing erosion in silicone rubber. The silicone rubber composites analyzed in this study were loaded with 50 weight% with alumina trihydrate, magnesium hydroxide and ground silica fillers, respectively. Results of inclined plane tests show deeper erosion under + DC than -DC and AC. However, a great reduction in erosion depth was achieved for alumina trihydrate-filled composites compared to those filled with silica and magnesium hydroxide. For alumina trihydrate-filled silicone rubber, erosion performance increases with decreasing particle size; whereas, for silica-filled silicone rubber, higher erosion resistance was obtained with a larger filler size. The correlation between simultaneous thermogravimetric and differential thermal analyses and the outcomes of inclined plane tests revealed that a smaller filler could form a larger surface area with strong bonds at the interface between the filler particles and polymer matrix. This could increase heat dissipation due to dry band arcing, thus limiting erosion of silicone rubber. However, larger particles promote an increase in the level of residues formed during the decomposition of silicone rubber. These stable residual layers could act as strong thermal shields against dry band arcing, thus limiting future erosion of the composite. This study demonstrates the significant impact of filler type and size on the suppression of AC and DC dry band arcing erosion in silicone rubber.