Effect of Thermal Aging on Micro-Region Structure and Electrical Properties of BOPP Films

Metallized film capacitors (MFCs) have been widely used in power transmission system, electronics industry, aerospace and other fields because of their high reliability and safety. The dielectric performances of Biaxially-oriented Polypropylene (BOPP) films used for capacitors greatly determines the long-term stable operation of the whole system. In actual operation, BOPP film is subjected to high temperature, and the local hot spot of the capacitor reaches 105°C. Therefore, the effect of thermal aging on the micro structure and dielectric properties of PP films is noteworthy. In this paper, three kinds of BOPP films with different crystallinity were thermal aged in a closed oven. Based on atomic force microscopy (AFM), the microregion morphology and structure of BOPP films before and after aging were characterized. Moreover, combined with electrical experiments, the effects of aging processes at different time on the leakage current, conductivity and breakdown strength of BOPP films were studied.