| With the rapid development of science and technology, it presents higher requirements on the performance of engineering dielectric materials. Inorganic-hybrid polymer materials have attracted much attention for their special properties. Because of their excellent electric properties especially on the corona resistance, DuPont 100CR film materials have been applied in the fields of electronic equipment, electrical engineering, etc.In this paper, alumina hybrid polyimide films and composite polyimide films were prepared through sol-gel reaction. Their electric properties, surface morphology and structure were measured and analyzed respectively by corona discharge measuring equipment, breakdown strength measuring system, partial discharge detecting equipment, and dielectric spectrometer, SEM and FTIR.It is shown that the corona-resistant aging life of composite PI film with 24wt% amount of alumina (calculated as Al2O3) is 22.0 hours, and it is close to that of DuPont 100CR film. It is revealed that the breakdown strength of hybrid film is lower than that of pure film, while composite film's breakdown strength is greatly higher than that of hybrid film, and composite film's breakdown strength is close to that of DuPont 100CR film, but is lower than that of pure film by about 10%. The curve of the permittivity (εr) and frequency of composite film is similar to that of DuPont 100CR film, and descend gradually in high frequency region. The curves of the tangent angle of dielectric loss ( tanδ) and frequency of composite film and DuPont 100CR film are alike, DuPont 100CR film and composite film's tanδincreases quickly in high frequency region. It is illustrated by SEM that the inorganic particles are distributed homogeneously on the surface of composite film, and the surface topography of composite film is close to that of DuPont 100CR film. The FTIR spectra reveal that there are characteristic peaks of alumina appearing in the FTIR spectrograms of composite film and DuPont film.
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