Study On Electrical And Thermal Aging Property Of Polyimide Mixed With Nano-particles

As a kind of functional materials, polyimide (PI) had excellent dielectricity and good mechanical property under high temperature, and it had been applied in the fields of frequency conversion system and insulation of electric machine. Because of the inherent aging distinction, however, the topic about how to prolong the used life by adopting active protection measure became more and more important. PI mixed with nano-particles was the hotspot of recent research, and its corona-resistance property had been improved largely. However, the problems about the aging breakdown mechanism and the forecast of thermal-aging life etc had not been resolved presently.The Dupont corona-resistant PI films (100-CR) were treated with the apparatus of corona aging made by ourselves for 10 hours, and characterized with SEM, AFM, and EDS. Their mechanism of aging and breakdown from the aspect about film structure, micro-configuration and the change of element content was studied. The results indicated that 100-CR film was made up of three layers. The outer layers contained a lot of in-organic element Al and the middle layer was pure PI. All of the films belonged to organic–inorganic continuous structure. The process of aging and breakdown had been composed by three steps: incubation course, expansion of branch and collapse breakdown. The initial style of breakdown was electrical breakdown, at last became thermal breakdown, probably due to the action of nano-inorganic ingredient.The thermal stabilization of PI mixed with nano-alumina particles made by ourselves was studied by TGA. The test results showed that the thermal stabilization of PI containing 8wt% inorganic component is better than that of PI containing 4wt% inorganic component. The thermal decompose kinetics parameters (thermal decompose activation energy, collision coefficient and action progression) of PI containing 4wt% and 8wt% nano-alumina particles in N2 and air were calculated with the way of Coats-Redfern, and checked with the method of Kissinger. At last it gained that the thermal decompose activation energy (E) were 91.18, 86.83, 105.53, 100.88 kJ/mol, respectively. The corresponding collision coefficient (A) and action progression (n) were obtained at the same time. According to the relation between thermal decompose kinetics and thermal aging, the thermal aging life curves of PI containing 4wt% and 8wt% nano-alumina particles in N2 and air were drawn. The results explained that the way of Coats-Redfern was one of the credible means to forecast the thermal aging life of mixed PI.