Highly absorbable lyocell fiber spun from celluloses/hydrolyzed starch-g-PAN solution in NMMO monohydrate

To improve the absorption properties of lyocell fiber, a hydrolyzed starch-grafted-polyacrylonitrile (HSPAN) superabsorbent whose powder size was less than 100 μm was added to the cellulose solution in N-methyl morpholine N-oxide (NMMO) monohydrate. The lyocell fiber was prepared by dry jet-wet spinning of the solution. To begin with HSPAN whose water-absorbency was 325 g/g (water/fiber) was prepared by hydrolysis of the copolymer in which acrylonitrile (AN) monomer was grafted onto the starch. The introduction of HSPAN led to a notable improvement of absorbency and absorption rate of lyocell fiber for water. The maximum water-absorbency of the fibers containing HSPAN 2 and 5 wt% was as high as 4.55 and 8.21 g/g, respectively. These values are comparable with 1.94 g/g for unmodified lyocell fiber. SEM and polarizing optical microscope results confirmed that HSPAN remained within the lyocell fiber at both wet and dry states. With increasing HSPAN content, however, the mechanical properties of lyocell fibers were decreased. Thus, the optimum HSPAN content may give a good combination of absorption and mechanical properties.