Thermal and Electrical Properties of Nitrile-Containing Polyimide/BaTiO3 Composite Films

Polyimide composite films were prepared by mixing the BaTiO3 particles into poly(amic acid) solution followed by film casting and thermal imidization under controlled temperature conditions. The poly(amic acid) was synthesized by solution polycondensation reaction of 4,4`-oxydiphthalic anhydride with 2,6-bis(4-aminophenoxy) benzonitrile, using N-methyl-2-pyrrolidone as solvent. The surface of BaTiO3 particles was modified by treating with an aminosilane coupling agent, 3-aminopropyltriethoxysilane. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterize the structure and properties of the composites. The influence of BaTiO3 content on the composite film properties was evidenced. The films exhibited good thermal stability having the initial decomposition temperature above 520 degrees C. They had stable dielectric properties over large intervals of temperature and frequency. The dielectric constant and the dielectric loss increased with the increase of BaTiO3 content. The dynamic mechanical analysis and dielectric spectroscopy revealed subglass transitions gamma and beta. At higher temperature an alpha-relaxation that corresponds to the glass transition and a conductivity process were evidenced. POLYM. COMPOS., 32:846-855, 2011. (c) 2011 Society of Plastics Engineers