HIGH TENACITY AND HIGH MODULUS FILM FROM POLY(2,2'-DICHLORO-4,4'-BIPHENYLENEPYROMELLITIMIDE)

In-plane isotropic poly(2,2 prime -dichloro-4,4 prime -biphenylenepyromellitimide) films were made by first adding acetic anhydride as a cyclodehydrating agent to the poly(amic acid) solution which was obtained by the reaction of 2,2 prime -dichlorobenzidine and pyromellitic dianhydride in N-methylpyrrolidone, and then casting the solution, and finally heating the films in bidirectionally restrained state. As polymer concentration of the fixed gel film was lowered, planar orientation and therefore initial modulus (M//i) of the heat treated film increased.