Engineered Interfaces in Extruded Polyphenylsulfone- Boron Nitride Composite Insulation

Improving matrix-filler interactions is critical for optimizing dielectric performance in composite insulation; however, the technique used to an introduce inorganic filler into organic matrices varies in its ability to satisfactorily reduce the size of cavities and interfaces. This study reports how sample rheology influenced the dielectric performance and thermal conductivity of extruded polyphenylsulfone (PPSU) – hexagonal boron nitride (BN) composite insulation through changing the BN incorporation strategy. Depending on the technique used to introduce BN into the host matrix, the low melt viscosity, torque, and melt viscosity temperature of the polymer were reduced, enabling better mixing, heat transfer, and smaller voids. This corresponded to an increase in dielectric strength compared to other formulations; however, the thermal conductivity shifted further away from the thermal conductivity target of 1 W/m·K target, which was an indication of a larger separation distance between the particles in samples with smaller interfaces. A trade-off between dielectric strength and thermal conductivity may exist when maximizing thermal conduction without sacrificing dielectric strength.