Cellulose/aromatic polysulfonamide blended fibers with improved properties

Cellulose/aromatic polysulfonamide (PSA) blended fibers with good flame-retardant, hydrophilic and mechanical properties were successfully prepared by dry-jet wet spinning technology with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as solvent. The solution behaviors were studied using the polarized light microscopy (PLM) and rheology measurements. PLM images showed that both cellulose and PSA dissolved completely in solvent. The viscosity of the blend solutions decreased with increasing ratio of PSA. While comparing the experimental results with the calculated data according to the log-additivity rule, it is revealed that zero-shear viscosity shows positive deviations, which indicates a strong interaction between cellulose and PSA. The flame retardant properties of the blended fibers were characterized. When the content of PSA is 70 wt% in the blended fibers, the limiting oxygen index (LOI) is up to 26.2% and the self-extinguishing time away from the flame is just 2 s. The blended fibers exhibited good mechanical properties with the tenacity of 2.6 cN/dtex and the E-modulus of 34.2 cN/dtex, which were higher than that of the washed PSA fiber. The contact angle of the blended fibers containing 70 wt% PSA was 64°, as was smaller than the value of PSA fiber. The morphology and structure of the blended fibers were characterized by scanning electron microscope (SEM), laser scanning confocal microscope (LSCM) and X-ray diffraction (XRD). The SEM images showed a rough morphology for the blended fibers. From the LSCM images, a sheath-core morphology was observed in the blended fibers with 70 wt% PSA. Only cellulose II crystalline structure of the blended fibers was observed from the XRD patterns because no crystallization occurred in PSA phase without heat-stretching and heat-setting at high temperature. This work provides a simple and effective way to prepare flame-retardant fibers with improved hydrophilic and mechanical properties.