Balance of mechanical and electrical performance in polyimide/nano titanium dioxide prepared by an in-sol method

Hybrid polyimide (PI)/titanium dioxide (TiO2) films were prepared by in situ polymerization and sol-gel and in-sol methods (where in-sol method indicates that in situ polymerization and the sol-gel method were used in the same samples). The mechanical and electrical properties were found to be sensitive to the processing methods and the dispersion of nano titanium dioxide (nano-TiO2) in the PI matrix. For the PI/TiO2 films prepared by the in situ polymerization method, their tensile strength increased with increasing TiO2-in situ (TiO2-in situ is the TiO2 nano-particles prepared by in situ polymerization method) concentration. However, the optimal corona lifetime of the PI/TiO2 films was 15 min at 20 kHz and 2 kV because of poor dispersion. For the PI/TiO2 films prepared by the sol-gel method, the corona lifetime reached 113 min because of superior dispersion and a tensile strength of about 19.63 MPa. A balance of mechanical and electrical performances was achieved with the in-sol method. The corona-resistant life of the PI/TiO2 films was 43 min, which was about six times longer than that of the neat PI. Their tensile strength was 83.5 MPa; these films showed no decrease in this value compared with the pure PI films. (C) 2016 Wiley Periodicals, Inc.