Effect of Graft Distribution on Conductivity and Breakdown Strength of Polypropylene Film for Power Capacitor

In this paper, the maleic anhydride (MA) is grafted onto the polypropylene (PP) molecular chain by UV irradiation. The distribution of maleic anhydride-grafted polypropylene (MA-g-PP) is controlled to investigate the influence of graft distribution on the dielectric performance. The results indicate that the film with MA-g-PP distributed on both sides exhibits the best electrical properties. The leakage conductivity declines by 72.4% at 30 °C and decreases by 89.9% at 115 °C. The breakdown strength is enhanced by 8.1% at 30 °C and improved by 13.9% at 115 °C. Through the analysis of electrostatic potential and molecular orbital, the MA-g-PP could capture carriers and has stronger attraction on free electrons. The carriers trapped on both sides of the film could form a reverse electric field to suppress charge injection, thereby inhibiting the molecular chain structure degradation. This paper provides theoretical guidance for grafting modification from the perspective of charge transport behavior regulation, which facilitates the promotion of film capacitors.