PEEK with Boron and Aluminum Nitride: Using a Model To Describe Thermal Conductivity Interactions in Ternary Composites

We here report the properties of polyether ether ketone (PEEK) loaded with hexagonal boron nitride (BN) with and without aluminum nitride (AlN), produced through extrusion compounding and compression molding. The primary purpose of this work was to improve the thermal conductivity of PEEK for electric insulation applications in electric motors. The thermal conductivity, thermal diffusivity, and effusivity increased with filler content reaching maximum values at 30 wt % filler that were a factor of approximately 2, 2, and 1.5 of those of the pure polymer. On a volume content, the ternary system PEEK/BN/AlN was more effective than the binary system (PEEK/BN) in raising the thermal conductivity. By the use of a developed model, it was possible to conclude that a small synergy in terms of thermal conductivity did exist. Density revealed compact systems with a porosity of 0–3%. Scanning electron microscopy revealed a uniform dispersion of BN and a combination of dispersed AlN nanoparticles and agglomerates in the ternary system. Dielectric and breakdown voltage results indicated that the composite properties were acceptable for electric motors, even though the DC breakdown strength decreased in the presence of the fillers.