Dielectric Breakdown Performance of Deashed Polypropylene for HVDC Film Capacitors

The metal ash in polypropylene (PP) significantly weakens the breakdown performance, and the deashing process can reduce the ash content. In this article, a novel deashing solution of metal deactivator (MD)/ethanol (ET) is prepared in an attempt to reduce the ash content and improve the breakdown performance. The film sample is prepared for the breakdown and conductivity performance tests, and the results reveal that the breakdown strength of the deashed sample is increased by 34%, the conductivity is greatly suppressed by 77%, and the discharge energy density is significantly enhanced by 80%. In addition, the total metal ash content of the deashed sample is decreased by 65%, and the defect coefficient after crystallization is reduced by 70%. A stable ring structure is formed between MD and metal ashes, which plays a great role in deashing. Therefore, the metal ash ionization and the catalytic effect on the thermal-oxidative degradation of PP are significantly inhibited, resulting in a great improvement in the breakdown strength. This deashing method provides a feasible reference for the study of high-reliability capacitor films with excellent insulation performance.