Preparation and characterization of all para‐position polysulfonamide fiber

Poly(4,4′‐diphenylsulfone terephthalamide) referred to as all para‐position polysulfonamide (all para‐position PSA) is a special kind of PSAs, copolymer s of 3,3′‐diaminodiphenylsulfone, 4,4′‐diaminodiphenylsulfone, and terephthaloyl chloride. However, with the increasing para‐structure content in the PSAs, the PSA shows very poor solubility in common amide‐type polar aprotic solvents and cannot be used for wet spinning. In this article, it was found that all para‐position PSA can be easily dissolved in N,N‐Dimethylacetamide (DMAc)/LiCl system, and then the all para‐position PSA fiber was prepared for the first time by wet spinning. The properties of all para‐position PSA pulps and fibers were investigated via Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy, thermal gravimetric analysis, dynamical mechanical analysis, X‐ray diffraction (XRD), and tensile strength testing. The tensile strength, elongation at break, and crystallinity of the resulting fiber were 4.4 cN/dtex, 15.9%, and 33.53%, respectively. The results indicated that all para‐position PSA fiber was a high‐temperature resistance fiber with better mechanical properties than common PSA fiber. The improved tensile strength of the fiber will expand its applications and may take place of Nomex in certain fields and become a new generation of flame retardant and high‐temperature resistant material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013