Effect of cellulose pulp type on the mercerizing behavior and physical properties of lyocell fibers

Various crimped lyocell fibers are spun from isotropic dopes of cellulose solutions in N-methyl morpholine N-oxide (NMMO) monohydrate with different compositions of hardwood and softwood pulp (IPS lyocell fibers). The physical properties of IPS, lyocell fibers treated with NaOH aqueous solutions are compared with those of commercially available Tencel lyocell fibers, which are obtained by anisotropic phase spinning. WAXD reveals that pulp composition has little effect on crystalline structure, and IPS lyocell fibers yield a crystalline structure almost the same as that of Tencel fibers (cellulose 11 structure). Alkali treatments affect physico-mechanical properties such as compaction and tensile properties. Mercerization with 10 wt% NaOH solution causes the largest weight loss and the highest degree of swelling. Lyocell fibers show a notable decrease in tensile strength when treated with strong alkali solutions higher than 7.5 wt%. In addition, IPS lyocell fibers with more softwood content display less reduction in tensile properties after strong alkali treatments.