Suppression of Dry-Band Arcing Erosion by Silica Filler in Silicone Rubber Composites

This paper investigates the effects of silica filler on the suppression of the dry-band arcing erosion of silicone rubber outdoor insulating materials. Liquid silicone rubber which was filled with silica at various levels and particle sizes were prepared and tested in the AC inclined plane test as per IEC 60587. The application of the 4.5 kV rms critical test voltage is shown essential in order to realize an effect for the filler throughout the study. Higher erosion resistance is obtained for composites containing higher loading level and larger particle size of silica filler, as indicated by the relative degree of surface damage and the measured level of the erosion depth. A simultaneous thermogravimetric and differential thermal analysis is conducted for elucidating the responsible roles of silica filler. Volume effect of silica filler replacing the polymer in the silicone rubber matrix appears to have a significant effect as reaching a loading level of 50 wt%. In addition, significant increase in the char amount is shown as reaching a silica particle size of 5 μm. Char, resulted as a byproduct of silicone rubber decomposition, is speculated to have a significant role in the suppression of further erosion from taking place during inclined plane test.