| As a high-performance engineering material, polyimide (PI) having excellent physical, chemical and electrical properties in a broad temperature range, have been applied on the electric insulatation, microelectronics, and aerospace industry. With the developing power electronics technology, variable frequency speed control technology is widely applied in the electrical machine, power saving 20 to 30%. The effect on the power saving is quite remarkable. Traditional polyimide partial discharge resistant properties have been unable to meet the requirements of frequency modulation, thus limiting the polyimide applications. So study on corona-resistant PI hybrid films is of importance. Now the research on preparation conditions, the dispersion of nano-materials, thermal stability, insulating properties of corona resistant PI hybrid films are mainly foucsed on. The corona resistant of PI have been greatly improved, but its breakdown mechanism of aging, prediction of thermal aging, and inorganic hybrid membrane components such as component analysis problem for inorganic hybrid film has not yet been resolved.Qualitative analysis and quantitative analysis on the Al content of PI/Al2O3 hybrid films were investigated using Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), X-ray Fluorescence Spectrometry (XRF), Fourier Transform Infrared Spectrometry (FT-IR), X-ray Energy Dispersive Spectrometry (EDS), Gravimetric Method, Thermo-gravimetric Analysis (TG, in air atmosphere). The result showed that FT-IR and EDS were good qualitative analysis methods. FT-IR was used to confirm the structure and component via analyzing the group of hybrid films. EDS was mainly used to monitor elements contained in the surface of hybrid films. The relative standard deviations (RSD) of EDS and TG were too great to use quantitative analysis, then they only could be used as semi-quantitative analysis methods. On the contrary, ICP-AES and Gravimetric Method were excellent quantitative analysis methods. The RSD of Gravimetric Method is below 0.8%.The RSD of ICP-AES is below 0.6%. And the recovery of standard sample for ICP-AES is 103.24%. At last, the fast and accurate analysis method for the A1 content in the hybrid films was set up eventually by ICP-AES.The aggregation structure of series hybrid films were measured via Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM).The result show that, compared with the PI/Al2O3 hybrid film, particle size and distribution of Al2O3 in PI/Al2O3 nano hybrid films were smaller. And increased with the content of Al2O3, the inorganic phase had evolved into network structure from the isolated spherical phase in the hybrid film.The DuPont corona-resistant PI film (Kapton 100-CR) was treated with the device of corona aging test made by ourselves for 10 hours, and characterized via SEM, AFM, and EDS. The mechanism of corona aging and breakdown of Kapton 100-CR was studied depend on the variation trend of the microstructure and the element content. The results indicated that Kapton 100-CR film was made up of three layers. The outer layers contained a lot of Al element and the middle layer was pure PI. All of the films belonged to inorganic-organic-inorganic composite structure. The process of aging and breakdown had been composed of incubation course, expansion of branch and collapse breakdown. The corona aging of Kapton 100-CR derived from the electricity, heat and chemical reaction.The thermal stabilization of PI/Al2O3 hybrid films made by ourselves was studied by TGA. First the thermal decomposition kinetics parameters (activation energy of thermal decomposition, collision coefficient and action progression) of PI hybride films containing 4wt% and 8wt% nano-alumina particles were calculated with the Coats-Redfern method at different heating rate in N2 and air, respectively.Then based on the relationship between thermal aging and the thermal decomposition kinetics, the thermal aging curve of PI hybrid films in air atmosphere and nitrogen atmosphere were draw out, getting the temperature for long term service. The results show that the Coats-Redfern method is reliable methods for prediction thermal aging life of PI/Al2O3 hybrid materials.
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