Preparation and characterization of ternary copolyimide fibers via partly imidized method

Abstract

A series of copolyamic acid (PAA) were synthesized from various ratios of two diamines p-phenylene diamine and 4,4′-oxydianiline (ODA) via copolymerization with pyromellitic dianhydride (PMDA) in polar solvent dimethylacetamide. A mixture of acetic anhydride and triethylamine was used as the cyclizing agent and added to the PAA in order to chemically convert it into partly imidized PAA, which then was spun into fibers by dry-jet wet-spinning. Finally, polyimide (PI) fibers were prepared after the as-spun fibers had been heat-treated. The results indicated that the intrinsic viscosity of partly imidized PAA was higher than that of pure PAA. Moreover, when the partly imidized PAA was spun into a suitable composition coagulation bath, the as-spun fibers gained a circular and dense internal morphology. The tensile strength and initial modulus of the heat-treated PI fibers were better than those of the homo-PI PMDA-ODA fibers, respectively, and the thermal stability of the PI fibers was also enhanced.