Study on the Corona Resistant Property of Polymide/TiO2@SiO2 Films

The corona resistant property of polyimide (PI) composite films is a very important parameter in the application of electrical insulation materials. The reports show that the ultraviolet (UV) ray in the corona process always destroy the PI. In this background, a novel method using SiO₂-coated TiO₂ (TiO₂@SiO₂) particle as dopant in PI has been proposed and the composite films with different content of PI/SiO₂@TiO₂ are prepared. Surface morphology, corona resistant property and UV-vis absorption property of the composite films are tested and characterized by scanning electron microscope (SEM), corona resistant system (CRS) and UV-vis spectroscopy (UV-VIS) respectively. The results show that PI/TiO₂@SiO₂ and PI/TiO₂ films are successfully prepared with different doping content and inorganic nano-particles are well dispersed into the PI. After the corona, the surface of the both kinds of films become rougher and the surface flatness of PI/TiO₂@SiO₂ is better than that of PI/TiO₂. The mass fraction of the C element on the surface of the films decreases. On the contrary, the mass fractions of the O element and Ti element increase in the process of corona. The lost mass fraction of the C element in the PI/TiO₂@SiO₂ is less than that in the PI/TiO₂. This shows that the stability of PI/TiO₂@SiO₂ is better than that of PI/TiO₂. With the increase of the content of the nano-particles in the films, the corona resistant properties of the composite films increase gradually. When the content of the nano-particles is about 25%, the corona resistant time is the longest. Beyond that doping content, the time will be shorter. The corona resistant property of the composite films doped with TiO₂@SiO₂ are better than those doped with TiO₂ under the condition of - oping the same content. The UV-visible absorption ability of the PI/TiO₂ is more significant than that of PI/TiO₂@SiO₂. The stability of PI/TiO₂@SiO₂ is better than that of PI/TiO₂, so the corona resistant property of PI/TiO₂@SiO₂ is more excellent than that of PI/TiO₂.