Dielectric Performance of Polypropylene Films Modified by UV Irradiation for HVDC Capacitors

The breakdown strength of polypropylene (PP) used in metalized film capacitors decreases sharply in the high-temperature environment, seriously affecting the stable operation of capacitors. This paper proposes a method to improve the dielectric properties by crosslinking modified with UV irradiation. After crosslinking, the thermal stability of the molecular chain was enhanced due to the three-dimensional network structure, and the density of traps increased. Elevated crosslinking improved the breakdown strength and electrical conductivity of polypropylene films at high temperatures. Results showed that the modified sample with 1.5 wt% of crosslinker addition had a maximum crosslinking degree of 17.8 %, with a decrease in conductivity. The breakdown strength was 569.4 kV/mm at 115 °C, which was 16.2 % higher compared to original PP. This paper provides a new idea for improving the high-temperature dielectric properties of PP films.