Effect of Gamma Radiation Modification on Crystallization and Breakdown Properties of Polypropylene

Abstract

Polypropylene (PP) is widely used as a dielectric material in metallized film capacitors, but the movement of the molecular chains and aggregate structure at high temperatures can greatly reduce the breakdown strength. In this paper, the effects of gamma radiation dose and sensitizer content on the crystallization properties and the breakdown strength of PP at high temperatures were investigated. The breakdown strength and crystallization properties are closely related to the crosslinking degree, which is affected by both the radiation dose and the content of sensitizer. In this study, it was obtained that the sample with adding 1 wt% sensitizer and 5 kGy radiation dose had dense spherical crystals, and 22.6% improvement of breakdown strength at $115^{\circ}\mathrm{C}$ compared to PP.