Preparation, morphology and properties of nano-sized Al2O3/polyimide hybrid films

Nano-sized Al2O3/polyimide (PI) hybrid films based on 4,4′-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) were prepared by incorporation with different content of nano-sized Al2O3 via in situ polymerization. The TEM and SEM micrographs indicated that the Al2O3 particles were homogenously dispersed in the polyimide matrix by means of the ultrasonic treatment and the addition of coupling agent. The mechanical properties and thermal stability of the pure PI film can be improved by adequate addition of Al2O3. The PI hybrid film was strengthened and toughened simultaneously by the introduction of the well-dispersed Al2O3 particles. The PI hybrid films showed improved electrical aging performance as compared with pure PI film. Especially, the PI hybrid films with 10 wt.% of Al2O3 content exhibited obviously enhanced electrical aging performance with the time to failure of 3.4 times longer than that of pure PI film. The improved electrical aging performance of the hybrid film was attributed to the nano-sized Al2O3 particles highly dispersed in the hybrid film, which confirmed by the investigation of the morphology and the surface composition of PI hybrid film before and after electrical aging.