Improved Dielectric Properties of Polypropylene Films by Electron-Beam Irradiation Modification for Power Capacitor

The dielectric properties of polypropylene (PP) for metalized film capacitors (MFCs) decrease significantly at high temperatures, affecting the reliable operation of capacitors. In this article, a method of improving the high-temperature dielectric properties of PP films based on electron-beam (EB) irradiation modification is proposed. PP films doped with pentaerythritol triacrylate (PETA) are prepared and irradiated with doses of 0–20 kGy under EB rays. The intrinsic correlation among the irradiation dose, crosslinking structure, and the dielectric properties of PP films is investigated. The improvement in dielectric strength is most significant for the PP film samples with a crosslinking degree of up to 17.4%. The dc breakdown strength and conductivity of PP15 are 561 kV/mm and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.12\times 10^{-{13}}$ </tex-math></inline-formula> at 125° C, respectively. The discharged energy density is 2.96 J/cm3 with the charge-discharge efficiency of 75.0%. The results show that the rigid structure impedes the bending and slipping of molecular chains at high temperatures, improving the heat resistance of PP. This study illustrates that the application of irradiation crosslinking modification improves the dielectric properties of PP films.