Effect of inorganic nano filler on the insulation properties of polyimide films

Polyimide is widely used in inverter-fed motor for its high thermal stability, excellent mechanical properties and corona resistant property. In order to study the effect of inorganic nano filler on the insulation properties of polyimide(PI) film, PI thin films and 10wt.% PI/Al₂O₃ thin films were made based on in situ polymerization method. The conductivity, thermal gravimetric analysis(TGA) and breakdown field strength were tested. Besides, the corona resistant time under a pulse voltage of them was gained. The results indicate that the conductivity of PI/Al₂O₃ films is higher than that of PI film, but the breakdown field strength is on the contrary. When the decomposition rate is 5%, the decomposition temperature of PI/Al₂O₃ film is higher than that of pure PI film by 17.5°C. The organic inorganic interface and high thermal stability of inorganic nanoparticles are the main reasons for enhance of the insulation properties of PI films. This study provides a theoretical basis for the improvement of the turn to turn insulation level of the inverter-fed motor.