Electrical Insulation and Mechanical Properties of Epoxy/Micro-silica (MS)/Micro-alumina (MA) Composites

Effect of mixture ratio of micro-silica (MS) and micro-alumina (MA) on the electrical insulation and mechanical properties of epoxy composites was investigated in order to develop a new insulation material for high voltage gas insulated switchgears. The mixing ratio of inorganic filler to epoxy resin was fixed to 70 wt%, and the mixture ratio of MS and MA in inorganic filler was 10:0, 9:1, 7:3, 5:5, 3:7, 1:9, and 0:10, respectively. Insulation breakdown strength increased with increasing MS content, however it did not follow the mixture rule of composite showing synergy effect. Those values for neat epoxy, epoxy/MS (70 wt%), and epoxy/MA (70 wt%) were 44.5, 53.4 and 47.1 kV/2 mm, respectively. Tensile strength and flexural strength were measured using a universal testing machine at a crosshead speed of 10 mm/min, and they also increased with increasing MS content, while they did not follow the mixture rule of composite.