Effect of structure on electric properties of Polyimide/Al 2 O 3 composites investigated by SAXS

It is generally believed that the electric properties of the composites are closely related to the structure. In this paper, the small angel X-ray scattering (SAXS) is applied to investigate the effect of structure on electric properties of the composites. Polyimide (PI) composite films filled with different content of gas-phase nano aluminium oxide (Al 2 O 3 ) particles were prepared via in-situ dispersion polymerization process. The experiment results show that the composites possess enhanced lifetime, increased dielectric constant and low dielectric loss attribute to the Maxwell-Wagner-Sillars (MWS) effects. On the basis of the measured fractal dimension and interface thickness of composites obtained via SAXS, the aggregation state of Al2O3 nano-particles were quantitative described. Results demonstrate that the electric properties of composites are closely related to the aggregation state of Al 2 O 3 nano-particles and the interface density is principally responsible for the dielectric constant and corona lifetime of PI/Al 2 O 3 composites.