Novel surface potential decay of TiO2-based polyimide nanocomposite films

Polymer nanocomposites have attracted wide interest as a method of enhancing polymer properties and extending their applications. Surface potential decay has been used widely as a tool to monitor charge transport and trapping characteristics of insulating materials. Polyimide (PI) as an engineering material has been paid more attention due to high thermal and chemical stability, good mechanical property and excellent insulating property in a wide range of temperature. There has been a lot of work over last few years on optical, thermal and mechanical properties of polyimide nanocomposites. However, less attention has been given to the effect of nano-fillers on charge transport and trapping in polyimide nanocomposites. In the present paper the surface potential decay after dc corona charging of PI nanocomposites has been studied. Polyimide nanocomposite films containing surface modified nano-particles by employing silane coupling agent were prepared by using in-situ dispersion polymerization process. The surface potential decay measurements on both pure PI film and PI nanocomposite films were investigated over the different corona-charged times and charging voltages in a controlled environment where temperature and relative humidity were kept at 21°C and 45%, respectively. It has been found that there is a significant change in the surface potential decay characteristics after nanofillers were introduced into polyimide. The surface potential decay pattern depends also on the amount of nano-fillers. The possible surface potential decay mechanisms responsible for the observed phenomena were discussed.