Improved thermal conductivity and AC dielectric breakdown strength of silicone rubber/BN composites

The present study demonstrates a synergistic effect with the addition of low loading levels of boron nitride filler in silicone rubber that resulted in significant improvement in both ac breakdown strength and thermal conductivity of silicone rubber composites. Our results show that addition of 2.5 vol% and 7 vol% of h-BN platelets improved thermal conductivity of silicone rubber composites by 25% and 65% respectively. The ac breakdown strength of silicone rubber composites was investigated by varying surface area and particle size of hexagonal boron nitride (h-BN) platelets. The breakdown strength of composites with only 2.5 vol% of low surface area boron nitride (0075) was enhanced by 20% and with high surface area boron nitride (7HS) was improved by 30%. The improvement in ac breakdown strength was primarily attributed to effective heat dissipation in the composite as well as low dielectric loss performance of the composite and was dependent upon the textural properties of boron nitride fillers.