Effect of BN Nanosheet Orientation on Thermal Conductivity and Insulation Properties of BN/Epoxy Resin Composite

Boron nitride (BN) is widely used for the preparation of epoxy resin composites with high thermal conductivity. Substantial increase of thermal conductivity needs high degree of BN concentration, it can lead to difficulty in material preparation and decrease insulation properties. Applying electric field during the curing process can increase orientation degree of BN and improve the thermal conductivity of composites at a lower degree of BN concentration. It is necessary to study the change of BN alignment, thermal conductivity and dielectric properties with different level of electric field strength. In this paper, DC electric field strength applied during the curing process of 25wt% BN/epoxy composite preparation is from 0 to 16.67kV/m. The orientation of BN is determined based on scanning electron microscope (SEM). The effect of the BN orientation on thermal conductivity and insulation properties is studied through thermal conductivity and dielectric spectral testing. With increase of the strength of applied electric field, the direction of BN in the composite is more parallel to the direction of electric field, the thermal conductivity is improved up to 4.1 times than that of pure epoxy, the dielectric constant and electrical conductivity increase. The results of the study show the impact of the electric field through the measurement of the BN alignment, thermal conductivity and insulation properties. The alignment of nano sheet is obvious. the thermal conductivity is higher and insulation properties are better compared with pure epoxy.