Dielectric properties of polyimide/Al2O3 hybrids synthesized by in-situ polymerization

Polyimide/nano-Al2O3 hybrids were prepared via simple in-situ polymerization and the thermal imidation routes. The hybrids film was characterized by transmission electron microscope (TEM) and infrared spectrum (IR). The dielectric behaviors of the composites were investigated as a function of the concentration of the Al2O3 nanoparticles. The results show that, at ± 980 V (bipolar), the corona-resistant life to the breakdown of polyimide with nano-Al2O3 loading of 30% is 93 min which is over 10 times longer than that of the unfilled film. Such large enhancement may originate from the shielding, thermal conduction and thermal stability effects of the nano-Al2O3 layer. As the nano-Al2O3 loading increases, the volume resistivity and the electrical breakdown strength show a little decline, while the dielectric constant of the hybrid films increases, which could be attributed to the significant interfacial zone between the polyimide and the filler.