Charge Transport Characteristics of ZnO/Polyimide Nanocomposite Under Vacuum DC flashover

Polyimide is a commonly used polymer dielectric material on spacecraft. The vacuum and radiation environment can easily lead to the accumulation of static charge on the spacecraft and trigger the surface discharge. Therefore, improving the surface DC flashover voltage of the dielectric in the space environment is crucial to improve the reliability of the spacecraft. In this paper, ZnO/PI nanocomposite was prepared to improve the flashover voltage. The electrical performance test including the relative permittivity, surface and bulk resistivity of the specimen was tested. The thermally stimulated depolarizing current method was used to analyze the trap parameters. The results show that the flashover voltage of PI is enhanced by nano ZnO, among which the flashover voltage increases the most at 3wt% ZnO content. Further analysis shows that the surface flashover intensity depends on the trap density, conductivity and methods of charge transportation and accumulation. The higher the trap density and higher electrical conductivity in the ohmic region, the lower the charge accumulated and the higher the flashover.