Enhanced thermal conductivity and rheological performance of epoxy and liquid crystal epoxy composites with filled Al2O3 compound

The heat dissipation capability of electrical insulation materials has been the bottleneck affecting the development of high power density electrical equipment and electronic devices. In this study, we investigated the effect of filler compounding, filler surface treatment and liquid crystal structure on the microscopic morphology, rheological performance, thermal conductivity and dielectric performance of the epoxy resin (EP) and liquid crystal epoxy resin (LCEP) composites. The results show that the composite with 45 μm and 3 μm Al2O3 compound fillers at a ratio of 3:2 showed a reduction in viscosity for about 1/3-1/30 and an enhancement in thermal conductivity for about 10%–40% compared to the other filler compounds with different filler size and ratio. The filler surface treatment by silane coupling agent diminished the viscosity by up to 90% and simultaneously enhanced the thermal conductivity of the composite by about 10%. The composite with LCEP matrix showed a thermal conductivity up to 2.47 W/(m·K) at 80 wt% filler loading, which is about 0.54 W/(m·K) higher than that of EP based composite. Moreover, the filler surface treatment can improve the electrical breakdown strength and volume resistivity of the composites. The results indicate that filler compound optimization, filler surface treatment and LCEP matrix can significantly improve the thermal conductivity, rheological and dielectric properties of the composites.