Electrical and Thermal Properties of PMMA/h-BN Composite Insulating Materials Produced by Electrostatic Adsorption Method

Thermal conductive plates in devices such as power modules for automobiles require materials which has performances such as high thermal conductivities and acceptable electric breakdown strengths. To this end, herein polymethylmethacrylate (PMMA)/hexagonal boron nitride (h-BN) composite materials with the flaky surface of h-BN oriented parallel to the thickness direction are fabricated by an electrostatic adsorption method. To investigate the influence of the molding temperature and measurement temperature on the composites, DC breakdown tests and thermal conductivity measurements are performed. In addition, conduction current measurements are used to estimate the volume resistivity. As the molding temperature increases, the DC breakdown strength decreases and the thermal conductivity increases. Additionally, the DC breakdown strength decreases as the measurement temperature increases. These results suggest that thermal processes might lead to breakdown and the thermal conductivity slightly decreases as the measurement temperature increases. The effect of the negative temperature dependence of the thermal conductivity in h-BN is greater than that of the positive temperature dependence in PMMA. Further, the volume resistivity decreases as the h-BN content increases, and the estimated volume resistivity with a 60% h-BN content is about 60 GΩ·cm.