Investigation of Thermal Conductivity and Breakdown Strength in Polypropylene/Ultra-High Molecular Weight Polyethylene Blends

This work presents a dielectric composite material with enhanced thermal conductivity: polypropylene (PP) is blended with ultra-high molecular weight polyethylene (UHMWPE) with up to 30% by weight, prepared by a solution blending method. Differential scanning calorimetry shows two distinct melting peaks of UHMWPE and PP phases respectively. The bimodal trend in crystallization temperature confirms poor mixing and separate crystal formation. The maximum thermal conductivity of the composites is ~0.30W/m·K, which is an increase of 35.5% compared to neat PP. The high viscosity of the mixing solvent, on the other hand, causes reduced chain alignment, resulting in reduced thermal conductivity enhancement. When compared to neat PP, the blends exhibit an AC breakdown strength that is reduced by just 3.6%, which is not significant considering measurement uncertainties. We conclude that the breakdown strength of these systems is relatively unaffected by their composition, due to an unchanged morphology.