The combined effect of heat-draw ratios and residence time on the morphology and property of aromatic copolysulfonamide fibers
The wet-spun aromatic copolysulfonamide (co-PSA) fibers were heat-drawn at different ratios and then characterized by tensile testing, wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). The results showed that the tenacity of co-PSA fibers did not increase monotonously with the draw ratios and a maximal value of tenacity and initial modulus was observed as the heat-draw ratio increased. Accordingly, the large crystalline size, content of mesophase and crystal phase, as well as long period and fibril length, were corresponding to the maximum tenacity of the heat-drawn fibers. This suggested that the residence time of the co-PSA fibers, during which it stayed in the heat tube, could not be neglected when the draw ratios changed. A more perfect structure could be formed with a favourable draw ratio and residence time.