Dielectric performance improvement of polypropylene film modified by γ-ray irradiation for HVDC capacitors

Polypropylene (PP) films exhibit low dielectric strength and high losses under elevated temperatures and strong electric field environments. This paper proposes a method to improve the dielectric properties based on γ-ray irradiation crosslinking, investigates the effect of the type of sensitizer on the crosslinking reaction, and explores the effect of crosslinking structure on the dielectric properties of PP films such as breakdown strength. The results showed that the type of group in the sensitizer influenced its activity in the crosslinking reaction, and the modified films added with pentaerythritol triacrylate (PETA) exhibited the highest crosslinking degree of 25.68%. In addition, it was found that the crosslinked structure improved the stability of the molecular chains at high temperatures and reduced the probability of thermal breakdown. At 115 °C, the modified films with PETA showed a 72.5% reduction in conductivity and a 33.6% increase in breakdown strength. This method demonstrates the importance of irradiation crosslinking modification for improving the reliability of PP films in high-temperature and strong electric field applications.