Effect of ultraviolet-induced chemical structure degradation on surface insulation strength of polyimide films

作者：Wen-Rui Li, Shiyin Zeng, Yucheng Zhang, Guangyu Sun, H.‐J. LIU, Changchun Qi, Fei Pang, Xiao-Gang Qin, Bai‐Peng Song, Guan-Jun Zhang · 发表于：Journal of Physics D Applied Physics · 年份：2026 · DOI：10.1088/1361-6463/ae7d3b · 研究领域：High voltage insulation and dielectric phenomena、Synthesis and properties of polymers、Polymer Science and PVC

Abstract Ultraviolet (UV) irradiation can induce pronounced surface degradation in polyimide (PI), which can consequently impair their surface insulation strength (the surface flashover threshold). In this work, the influence of UV-induced degradation on the surface flashover behavior of PI films is systematically investigated. Two commercially available PI films with distinct molecular structures are selected and subjected to accelerated UV irradiation to introduce controlled degradation states. The results indicate that UV exposure triggers molecular chain scission and surface structural reconstruction, leading not only to a deterioration in mechanical properties and thermal conductivity, but more critically to substantial modifications of near-surface electrical processes closely associated with surface flashover. Comprehensive characterizations of dielectric response, charge transport behavior, trap state distribution, and secondary electron emission properties indicate that UV-induced degradation promotes field electron emission at the cathode triple junction, deepens trap energy levels and suppresses charge dissipation, enhances secondary electron multiplication, and may intensify outgassing-related processes. These degradation-induced effects facilitate earlier flashover initiation and accelerates the subsequent development. In addition, the two PI films exhibit different sensitivities to UV-induced degradation, and the disparity in the deterioration of their surface f...