Dielectric Energy Storage Performances of Photoinitiator-Modified Polypropylene Films

Polypropylene (PP) film is extensively utilized in capacitors due to its low dielectric loss and high breakdown strength. However, its susceptibility to dielectric property degradation and reduced energy density under elevated temperatures limits its further application in high-power-density devices. To enhance the energy storage stability of PP at elevated temperatures, this study employed an ultraviolet-light-initiated grafting method to graft acrylic acid (AA) molecules onto the PP backbone. Using benzophenone (BP) as the photoinitiator, the influence of initiator content on the structure and energy storage performance of PP-g-AA films was systematically investigated. Results indicate that an appropriate BP content effectively promotes AA grafting onto the PP surface, enhancing intermolecular compatibility and crystalline integrity of the film. At a BP content of 0.3 wt%, the film exhibits a breakdown electric field strength of 495.9 MV/m at 125 ℃, with discharge energy density increased to 2.41 J/cm3 and charge-discharge efficiency reaching 95.87%. Compared to pure PP films, the high-temperature energy storage performance was significantly enhanced.