Study on Insulation Properties of Spherical Boron Nitride Epoxy Composite Resin

Hexagonal boron nitride has high thermal conductivity and excellent insulating properties, however, conventional flake boron nitride has a large specific surface area, which dramatically increases the viscosity of slurry and makes it difficult to be molded when composited with epoxy resin. In this paper, spherical boron nitride was prepared to address this problem, and it was used as a filler to prepare spherical boron nitride epoxy resin composites. A comparative study was made to investigate the effect of the morphology and filling amount of the flake/spherical boron nitride filler on the electrical insulation properties of the epoxy resin composites. It is found that the relative dielectric constant of the composites increases with the increase of filler content, and the dielectric loss factors are lower than 2.0%; compared with the flake boron nitride, the spherical boron nitride composites have lower relative dielectric constant and dielectric loss because of the reduction of “filler-resin” interface; the addition of the appropriate amount of boron nitride significantly enhances the volume resistivity and breakdown strength of the composites; the relative dielectric constant of the epoxy resin composites is lower than that of the filler resin. The addition of appropriate amount of boron nitride can significantly enhance the volume resistivity and breakdown strength of the composites.