Experimental research on conduction current characteristics of 100HN and 100CR polyimide film before and after corona aging

To investigate the effect of inorganic nanoparticles on the carrier transportation properties of polyimide (PI), the measurement on conduction current was carried out with both the original 100HN PI film and nano-Al₂O₃ filled corona-resisting 100CR PI film produced by DuPont Company. Experimental results showed that: before corona aging, the current in ohm region of 100CR PI film was significantly larger than that of 100HN PI film, while the space charge limited current of 100CR PI film was less than that of 100HN PI film; after corona aging, the trapped carrier density and electrical aging threshold of 100HN PI film decreased, while both increased in case of 100CR PI film. It can be deduced from above results that the introduction of nanoparticles into polyimide may increase both the thermal-released free charge carriers and trap level density and depth. The two consequences act oppositely on the conduction current and determine the conduction current in low electric field and that in high electric field respectively. In addition, corona aging affects the conduction current of 100CR PI film and 100HN PI film differently with mechanism to be investigated.