Preparation, morphology and properties of nano-sized Al₂O ₃/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 A1₂O₃ via in situ polymerization. The TEM and SEM micrographs indicated that the A1₂O₃ 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 A1₂O₃. The PI hybrid film was strengthened and toughened simultaneously by the introduction of the well-dispersed A1₂O₃ particles. The PI hybrid films showed improved electrical aging performance as compared with pure PI film. Especially, the PI hybrid films with 10wt.% of A1₂O₃ 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 A1₂O₃ 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.