Healing filler–matrix interfaces in drawn BN/UHMWPE composites by a simple thermal annealing treatment†

Thermally conductive polymer dielectrics have great potential in modern electronic systems by efficiently dissipating the generated heat and thus decreasing the working temperature. Here, unfunctionalised boron nitride microplatelets (BN) and macromolecular alignment, induced by solid-state drawing, were adopted to increase the thermal conductivity of ultra-high-molecular-weight-polyethylene (UHMWPE). A thermal annealing treatment was then utilised to heal filler–matrix interface defects, created during drawing, to enhance the dielectric properties. In particular, an annealed UHMWPE/1 wt% BN composite film with a draw ratio of 20 showed a 20% increase in breakdown strength and a slight increase in charge–discharge efficiency to 94%. This finding demonstrates a simple and fast method to optimize the dielectric and thermal conduction properties of polymer composites films, without the need of any filler surface functionalisation, which promises widening applicability of polymer film capacitors.