Crystallization Regulation of Cross-Linking Polypropylene on Dielectric Performance for Capacitors in SMES

In this paper, a method based on irradiation cross-linking modification and crystallization regulation is proposed to improve the dielectric properties of polypropylene (PP) films. Sorbitol nucleating agent DMDBS with different contents is added during the preparation of cross-linked PP film to investigate the influence of nucleating agents on cross-linking modification. The results show that the cross-linked structure restricts the carrier migration behavior under the electric field, leading to a decrease in the conductivity. The doping of nucleating agents increased the nucleation density and the cross-linking degree of the PP films, thus further improving their insulating properties. The cross-linking degree of PP film doped with 0.05 wt% DMDBS is increased to 20.16%. The conductivity was decreased by 36.8%, and the breakdown strength was improved by 18.3% in contrast to pure PP film. The paper provides practical experience for the enhancement of insulating properties of PP films for capacitors.