Dielectric and thermal properties of boron nitride and Silica epoxy composites

Samples containing only submicrometric filler (BN), only nanometric filler (Silica) and both fillers were prepared by gravity moulding. A pure epoxy sample was also prepared to quantify the enhanced properties. Glass transition temperatures were measured by Differential Scanning Calorimetry. Dielectric Breakdown data were analysed using the Weibull statistical method and Dielectric Spectroscopy was used at low and high voltage to measure the samples permittivity. The glass transition temperature is decreased by BN presence but not by nanosilica. At ambient temperature, the β relaxation peak is not affected by nanoparticles nor by applied voltage. Strangely, the sample containing the two nanoparticles type is not affected compared to pure epoxy. On dielectric spectra, a supplementary relaxation peak for samples containing nanosilica is present. This peak is associated with the interphase between nanosilica and polymer.