Dielectric Properties of Thermally Aged Polypropylene Blended with Propylene-Based Copolymer

Nowadays, polypropylene (PP) has become favorable in high voltage alternating current (HVAC) and high voltage direct current (HVDC) due its excellent electrical properties. Nonetheless, PP has a major issue in mechanical properties, stiffness and brittleness. Therefore, propylene-based copolymer (PBC) has been used to improve the mechanical properties of PP, yet this could negatively affect the degradation performance of polypropylene/copolymer blends in comparison with pure polypropylene. Thus far, the impact of thermal aging on PP/copolymer blends has not been thoroughly examined, particularly for dielectric properties. In this paper, direct current (DC) breakdown strength, DC conductivity, and scanning electron microscopy (SEM) has been reported for PP blended with 20 wt% of PBC, unaged and aged at 120 °C. The results reveal that DC breakdown strength of aged PP reduced by 14% compared to unaged PP, while DC breakdown strength of aged PP/PBC blend is comparable with unaged PP/PBC blend. The DC conductivity for both PP and PP/PBC blend reduced after thermal aging, but the reduction for PP/PBC blend is more pronounced compared to pure PP. Meanwhile, there are no changes in morphology for both unaged and aged PP and PP/PBC blends. Therefore, PP/PBC blend has demonstrated a good impact and can be an alternative for power cable insulation.