Structural, dielectric and mechanical changes in BOPP films under different thermal aging conditions

Polymer film capacitors are widely used in power electronics, automotive, petroleum, and other applications due to their high breakdown voltage, low loss, and high reliability. The thermal aging mechanism of dielectric polymer BOPP is crucial for the exploration of application boundaries in terms of safety. In order to investigate the performance change mechanism of thermally aging films in a systematic manner, thermal aging tests were carried out at 50, 85, and 105 °C for the samples aged for 1, 5, 10, and 15 days, respectively, characterized and compared in terms of structural, mechanical, and dielectric aspects. The experimental results demonstrate that short-term thermal aging is effective in improving the breakdown strength and energy storage density of BOPP films. However, under long-term thermal aging, the films undergo a recrystallization process, which results in increased surface roughness and dielectric loss, along with decreased elongation at break and breakdown field strength. This work opens a novel route for the development of new dielectric materials and heat treatment processes.