The effects of residual polymerization solvent on the physical properties of poly(2-cyano-p-phenylene terephthalamide)

Abstract

Poly(2-cyano-p-phenylene terephthalamide) (CY-PPTA) was obtained by the polycondensation of terephthaloyl dichloride and 2-cyano-p-phenylene diamine in the mixture of N-methyl-2-pyrrolidone (NMP) and calcium chloride (CaCl2). Washing the polymerized product with water and drying at the elevated temperature inevitably left a small amount of polymerization residues which could be eliminated only by additional washing with acetone. The thermogravimetric and H-1-/C-13-NMR analyses revealed that the residues were largely composed of NMP which existed as a complex with the polymer. The complex was broken up between 200 and 300 degrees C and evolved 5 wt % of gaseous products, which had an adverse effect on the physical properties of as-spun CY-PPTA fibers obtained by dry jet-wet spinning. The heat treatment of the as-spun fibers including residual NMP exhibited some porous morphology on the fiber surface due to the evolved gases. However, the existence of the residual NMP had little effect on the intrinsic viscosity and liquid crystalline phase behavior of the polymer. Both rheological and optical properties exhibited the critical concentration at 3 wt % with the clear schlieren texture of nematic liquid crystalline phase. The inclusion of residual NMP decreased dynamic viscosity and yield stress. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43672.