Research insight into the change of aggregation structure of BOPP films and its influence on electrical properties under accelerated thermal aging

Abstract Biaxially oriented polypropylene (BOPP) film used in pulse film capacitors withstands high temperatures for a long time. This leads to frequent faults in pulse film capacitors, affecting the reliability of the pulse system. In this paper, the thermal aging tests of BOPP films at 100°C for 10–80 days are carried out in this paper, and the physicochemical and electrical properties of the aging materials are characterized. The results show that more deep and shallow traps to BOPP films are introduced during the thermal aging process. With the increase in aging time, the breakdown field strength gradually decreases, and the conductivity decreases first and then increases. Under the action of thermal aging for a long time, the recrystallization of materials and the destruction of molecular chains by thermal aging are the main reasons for the increase of traps and the decrease of breakdown field strength. The former is dominant in the early stage of aging, and the latter is dominant in the late stage of aging. Therefore, the conductivity shows the law of slow decrease first and then rapid increase. The relevant research provides a theoretical foundation for the process improvement and life prediction of BOPP films.