The effects of Al 2 O 3 contents on the morphology and electrical properties of polyimide/nano-Al 2 O 3 composite films

Polymer-inorganic composite materials, which offer enormous scientific and technological promise in areas ranging from microelectronics to nanobiotechnology, is an exciting area of research. In this paper, a boehmite sol, which used as the precursor of nano-alunima particles, was firstly synthesized by the hydrothermal process using aluminum isopropoxide as the precursor of aluminu and toluene as solvent. Then this obtained hoehmite sol was in situ added into the polyimide (PI) matrix to fabricate the polyimide/Al 2 O 3 (PI/Al 2 O 3 ) nano-composite films. The effects of different hoehmite contents on the morphology, mechanical, thermal stability and electrical properties of PI composite films were investigated. Scanning Electrical Microscopy (SEM) results indicated that after the curing process, all the boehmite sol totally changed to the Al 2 O 3 nanoparticles and they were homogenously dispersed in the PI matrix without any agglomeration. Thermal Gravimetric Analysis (TGA) showed that the initial decomposition temperature of PI/Al 2 O 3 nanocomposite films was slightly increased with the increased of hoehmite sol contents, which meaned that the thermal stability of PI/Al 2 O 3 composite films was improved. Moreover, the results of corona resistance tests indicated that the addition of Al 2 O 3 nanoparticles greatly improved the corona resistance of PI composite films. When the Al 2 O 3 content was 12wt.%, the corona resistance time reached 136 hours, while the pure PI film was only 0.5 hour. This improvement in corona resistance of PI/Al 2 O 3 composite films should be attributed to the preventing charge accumulation effect of Al 2 O 3 nanoparticles.