Preparation of polyamideimide films containing glass by sol-gel process and their dielectric breakdown

Polyamideimide (PAI) composite film containing 57 phr glass was prepared by the sol-gel process starting from metal alkoxides. The film is flexible, pale yellow, and transparent. The fracture surface indicates that the glass particles are uniformly dispersed and have a diameter of less than 0.1 μm. The dielectric breakdown strength Eb of the glass-PAI film is almost equal to that of the PAI film. Eb decreases with sample thickness from 0.4 to 1.3 μm and decreases with temperature from room temperature to 300°C. These results indicate that PAI can be filled with the solgel glass without the introduction of defects which affect the dielectric breakdown. Eb is lowered by aging at 300°C. The Eb of glass-PAI film decreases more than the Eb of PAI film. The decrease in Eb seems to be caused by oxidation of silane coupling agent as well as diphenylmethane groups in the PAI chain