The synergistic effects of the micro-BN and nano-Al^sub 2^O^sub 3^ in micro-nano composites on enhancing the thermal conductivity for insulating epoxy resin

Epoxy resin has been widely used in electrical and electronics industries due to its excellent adhesion and insulating properties. However, the low thermal conductivity limits its application in the devices, especially under the working conditions of high frequency. In this work, the epoxy resin composites filled with binary fillers of dopamine modified micro-BN and KH550 modified nano-Al2O3 were fabricated and the thermal conductivities, dielectric losses and breakdown strengths in high frequency and electrical field of the composites were studied. A high thermal conductivity of 1.182 W m−1K−1 was realized in the composite with 22.5 wt% BN and 7.5 wt% Al2O3, which was about 700% higher than neat epoxy resin. The results of breakdown experiments in high frequency and high voltage field showed that the positive effect of the thermal conductivity increase was greater than the negative effect of the dielectric loss increase, and the notably improved breakdown time of the composite was 406% higher than that of neat epoxy. The epoxy resin composites with high thermal conductivity and excellent dielectric strength could be a potential insulating material in the electrical and electronics industries.