Novel BN-epoxy/anhydride composites with enhanced thermal conductivity

A new series of high thermal boron nitride (BN) composites are prepared and characterized by several techniques. They are formed by an epoxy-anhydride matrix and different BN contents, ranging from 30 to 80 wt%, of 120 mu m agglomerates. For high BN ratio (>= 60 wt%), epoxy mixtures were compressed (75 MPa) during 1 minute before curing, eliminating voids due to the high increase of viscosity, improving the compactness of the material and enhancing the thermal conductivity (TC). The curing process evolution was studied by calorimetric measurements to see if there was an influence of the filler on the curing rate. Rheological tests were performed to obtain the percolation threshold. It was observed that BN filler did not affect negatively the thermomechanical properties of the materials and allowed to enhance the TC from 0.17 W/m K in the case of the neat epoxy, to 3.06 W/m K when 80 wt% of BN agglomerates were added, which represents an improvement of 1700%.