Revealing the nature of frequency-dependent breakdown characteristics for typical polymer insulating films

Polymer dielectrics are critical for the reliable operation of electrical equipment under high field strength and high frequency. The degradation of breakdown performance at high-frequency AC fields has been noticed in polymer dielectrics, while the underlying mechanism remains unrevealed. Here, systematic experiments as well as first-principles calculations are combined to illustrate the correlation between the intrinsic material properties and the electrical insulating performance, including the energy bandgap Eg, glass transition temperature Tg, and dielectric dissipation factor tanδ. The results demonstrate that Eg predominantly governs the intrinsic DC breakdown strength, tanδ is the key driver of the heat generation under high-frequency conditions, and Tg underpins the heat endurance. They together determine the frequency-dependent breakdown performance. This research provides insights into the core intrinsic factors of high-frequency insulation reliability and offers guidance for selecting quantifiable and intrinsic proxy properties for the design and development of polymer-based insulating polymers.