COPOLYIMIDES - THERMAL AND MECHANICAL-PROPERTIES

Polyamic acids with different proportions of benzidine (Bz) and 4,4'-d iamino-diphenylmethane (DADPM) were prepared by polycondensating diffe rent molar ratios of Bz and DADPM with pyromellitic dianhydride (PMDA) in dimethyl formamide. Chemical cyclodehydration of copolyamic acids by acetic anhydride/pyridine resulted in corresponding copolyimides. P olymers were characterized by determination of intrinsic viscosity and nitrogen content. Thermal stability was investigated by thermogravime tric analysis. Some of the copolyamic acids were wet spun into fibres and subsequently converted to polyimides. Copolyimide fibres containin g benzidine moiety had better mechanical properties than those contain ing DADPM.