Fabrication and Properties of Polyimide/Aluminum Oxide Composite Films via Different Alkali Etching and Ion Exchange Technique

Abstract

The polyimide (PI)/aluminum oxide (Al2O3) composite films were prepared via alkali surface modification and ion exchange technique on flexible PI films. Firstly, the polyamide acid layers were formed on both surfaces of PI film through chemical surface modification in aqueous KOH and NaOH solution, respectively. Subsequently the ion exchange process was processed in AlCl3 aqueous solution. After final thermal annealing in air, the aluminum ions which exchanged on both surfaces of PI film became continuous Al2O3 composite layers. The surface morphology, microstructures, thermal and electrical properties of the PI/Al2O3 composite films were tested by the scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), electric breakdown voltage and corona-resistant measurement. Results from SEM measuring revealed that the surfaces of composite films became much rougher with the increasing alkali treatment time. FT-IR spectrums showed that the treatments of alkali surface modification and ion exchange had no effect on molecular structure of polyimide. TGA results showed that the excellent thermal properties of the film are maintained. Electric breakdown voltage of composite films showed monotonically decreased with the increasing alkali treatment time. Corona-resistant test results showed that the best corona-resistant times of composite films which using NaOH and KOH modification were up to 22.6 minutes and 15.4 minutes, respectively.