Electrical Characteristics of Polyimide Film modified by Nanoparticle in LN

Polyimide (PI) film is an organic polymer, which has excellent mechanical and electrical properties. At present, several types of researches have been conducted on the electrical properties of PI films at ambient and high temperature, nevertheless few researchers focused on the modification effect and electrical of PI films modified by nano properties at extra low-temperature conditions. In order to improve the insulation performance of PI film in liquid nitrogen (LN) to promote its application in superconducting amorphous alloy transformers, nanoparticles (NP) SiO
2
and Al
2
O
3
with 1%, 3%, 5%, and 7% mass fractions are used to modify PI film. AC breakdown electrical field strength and the permittivity of modified and unmodified PI films with different mass fractions are obtained in LN. By comparing the test results of PI films with different NP mass fractions, the optimal doping mass fractions for SiO
2
NPs are 5wt%, and for Al
2
O
3
is 3wt%.