Effect of nano Al₂O₃ crystallographic structure on properties of polyimide hybrid films

To prepare PI/nano Al₂O₃ hybrid films with different Al₂O₃ contents and crystallographic structures, the nano Al₂O₃ treated by coupling agent was dispersed uniformly in polyamic acid by ultrasonic wave. The micro morphology, aggregation structure and performances such as optical throughput, thermal stability and electric breakdown strength were studied. The effects of crystal structure and contents of nano- Al₂O₃ on the microstructure and properties of PI/nano Al₂O₃ hybrid films were also investigated. Results show that the thermal stability and electric breakdown strength of PI/nano Al₂O₃ hybrid films are higher than those of pure PI film; the thermal stability is enhanced with the increasing of Al₂O₃, and the electric breakdown strength is intensified firstly and weakened then. The crystallographic structure of Al₂O₃ powder has major influence on PI molecular chain's bulk density, which results in the property variance of hybrid films.