Masakazu Mesaki, Yoshinori Tatematsu and Hideki Goda
Aromatic polyamide-imide resins (PAI) based on Trimellitic anhydride and Diphenylmethane-4,4'-diisocyanete were modified by an oligo-alkoxysilane compound to obtain novel silane-modified PAI. Then, PAI-silica hybrid films were prepared by drying and curing the silane-modified PAI. Increasing the silica unit content gives the hybrid films a higher Young's modulus and a higher tensile strength than the original PAI film, however, maximum elongation is maintained. Furthermore, they have much lower moisture absorption than PAI film under wet conditions. Moreover, this hybrid film has been found to have a different dielectric constant than the conventional film. This report describes properties of silane-modified PAI varnish, which is used as an insulation layer for enameled wire.