Study On The Preparation And Properties Of Inorganic-Hybrid Polyimide Films

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, the inorganic-hybrid polyimide (PI) materials have been applied in the fields of electronic equipment, electrical engineering, etc.In this paper, alumina hybrid polyimide film and composite polyimide film 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 lifespan of PI film with 23wt% amount of alumina (counting as Al2O3) is 95.1 hours, 24.1 times longer than that of pure PI film, and it is similar to that of DuPont 100CR film, but composite film's corona resistance property is inferior to DuPont 100CR film's. The results of partial discharge experiment demonstrate that the discharge inception voltage of DuPont 100CR film is two times more than films'prepared by us. It is revealed that the breakdown strength of hybrid film is the same as that of pure film, while composite film's breakdown strength is lower than that of hybrid film, though DuPont film's breakdown voltage is the same as pure film's, but higher than that of composite film by 13%.The relative dielectric constantεrof composite film is higher than pure film and hybrid film's in low frequency region and intermediate region, which declines quickly in high frequency region. The curves ofεr- f of hybrid film and DuPont film are alike, and descend gradually in high frequency region. While the dielectric loss tanδof composite film and DuPont film are identical and decline with frequency in low frequency region, hybrid film's tanδis the same in this region, but all the three films'tanδare larger than pure film's. And in intermediate and high frequency region, the curves of tanδ- f of pure film and DuPont film are similar, while hybrid film and composite film's tanδincreases quickly. It is illustrated by SEM that the inorganic particles are distributed homogeneously on the surface of hybrid film, and the content of Al2O3 is 21wt%.The FTIR spectrum reveals that pure film, hybrid film and DuPont 100CR film's imidization is not complete, and there are charac-teristic peaks of alumina and silica appearing in the FTIR spectrograms of hybrid film and DuPont film.