To study the influence of temperature and humidity on corona resistance of polyimide（PI）doped with nano alumina（Al2O3）particles

PI/Al2O3 composite film is prepared by in situ method

then corona resistance test of pure PI film and PI/Al2O3 composite film under high frequency square voltage is conducted. The results show that PI/Al2O3 composite film performances better than pure PI film on corona resistance under the same voltage

because nano particles would float on the surface of film which can protect film from further erosion. In addition

polyimide would degrade and produce much gas distributing among polymer matrix

which resulting in distortion of electric field and shorten the life time of film as the increase of temperature. Because of PI/Al2O3 film higher thermal conductivity than pure PI film

PI/Al2O3 film shows better performance in high temperature environment.Furthermore

with the increase of relative humidity

the life time of corona resistance of PI/Al2O3 film would increases first and then decreases

it mainly because water molecule would surround nano particles and form "water shell"

resulting in more transmission paths of charge emerges when relative humidity is low. While relative humidity is high

a lot of ions and little molecules produce due to hydrolysis of polyimide

which leads to distortion of electric filed and deterioration of erosion from corona.