HIGH STRENGTH AND HIGH MODULUS POLYIMIDE FIBERS FROM CHLORINATED RIGID AROMATIC DIAMINES AND PYROMELLITIC DIANHYDRIDE

Polyimide fibers were prepared from chlorinated rigid aromatic diamines and pyromellitic dianhydride (PMDA) by wet-spinning the N-methylpyrrolidone solutions of their precursor poly (amicacids) and then imidizing the fibers thermally or chemically. Random copolyimides had better drawability and gave stronger fibers than homopolyimides. For example, the chemically imidized copolypyromellitimide fiber of 2, 2'-dichlorobenzidine (Di-Cl-Bz)/benzidine (80/20) showed tenacity (T) 22.0 g/d, elongation (E) 1.7% and initial modulus (Mi) 1490 g/d. In general, the tensile properties of thermally imidized fibers were inferior to those of chemically imidized fibers, but random copolymers containing Di-Cl-Bz•PMDA as a main component yielded thermally imidized fibers having good tensile properties comparable to those of chemically imidized fibers. For example, T (g/d)/E (%)/Mi (g/d) of thermally imidized Di-Cl-Bz/2-chloro-p-phenylenediamine/PMDA (85/15/100) fiber were 19.1/1.4/1510.