The nano-SiO2 dispersions were prepared by microemulsification-phasetransformation method and mechanically blended with polyamide-imideresin

and then cast into films with different nano-contents. Nanocomposite films werecharacterized by transmission electron microscopy (TEM) and Fourier transforminfrared spectroscopy (FT-IR). The corona resistance life and other dielectricproperties of the material were tested in accordance with the IEC60343 standardand thermogravimetric analysis was carried out. The results show that nano SiO2particles are uniformly dispersed in PAI matrix and materials reactedcompletely.The thermal stability of the composites are enhanced by adding nanoparticles.With the increase of SiO2 content

theelectrical conductivity

dielectric constant and dielectric loss changesregularly. Compared with pure PAI

the corona resistance life of nanocompositewith 20% SiO2 is 17.35h

which increases more than eight times. However

the breakdown strength of nanocomposites is a little lower with increase ofnano SiO2 loading.