Effects of filler distribution on morphology and thermal conductivity of polymer composites

The dielectric properties of the composite samples were characterized using dielectric spectroscopy in a wide range of frequencies (10^-2 Hz - 1 MHz) at temperatures ranging from 20 to 200 °C. The real part of the dielectric permittivity of a microcomposite containing 50 wt% of BN was found to be close to that of the PE matrix value (about 2.5) at 0.1 Hz after water removal. Thermal conductivity of PE was greatly improved: after a high-milling time, it increased by about 50% in comparison with the pure matrix. The study of the AC breakdown voltage has indicated a decrease when high-milling time was used. On the opposite, when short-milling time was used, a slight increase in breakdown was observed. This could be attributed to the defects and the possible contamination of composite by the crucible-balls. Scanning Electron Microscopy has been used to investigate the morphology of PE-BN films to evaluate the dispersion of BN.