High-Insulation Performance Polyimide Dielectric Based on Built-in Electric Field Structure Design

Polymer materials play an important role in power electronics and electrical insulation systems. Despite significant efforts in research to enhance their insulation performance, improving the dielectric and insulation properties of polymer dielectrics remains a challenging task. In this work, a method was introduced to enhance the breakdown strength and corona endurance life of polyimide films by adding hydroxylated boron nitride/polyethyleneimine nanosheets. The breakdown strength of polyimide based composite film is significantly enhanced (661 kV/mm), and the corona endurance life reaches 40 h. The improvement in breakdown strength is mainly attributed to the wide bandgap characteristics of BNNS. And the hydroxylated boron nitride nanosheets have excellent dispersibility in the composite film. The improvement of corona endurance life is due to the formation of a reverse built-in electric field inside the filler of BOP under low voltage conditions, which is opposite to the direction of the external electric field. The built-in electric field can partially counteract the external electric field, reducing the number of ionized electrons generated during the secondary collision process, thereby extending the corona endurance life. In addition, the two-dimensional nanosheets form a barrier layer, hindering the electrical breakdown path and further improving the insulation performance. The research results provide a new design approach for improving the insulation performance of polymer composite films.