Reinforcement of Wet-Spun Cellulose Nanowhisker Fibers by Post-Oxidative Crosslinking of Surface Mercapto Groups

Cellulose nanowhiskers (CNWs) having surface mercapto groups were prepared by surface carboxylation of CNWs and subsequent grafting of 2-aminoethanethiol. The obtained thiolated CNWs (SH-CNWs) were spun into fibers by wet spinning, followed by a post-oxidation treatment with hydrogen peroxide to generate disulfide linkages working as crosslinks between SH-CNWs. Optimizations of several spinning conditions, including types of coagulation and oxidation baths, oxidation times, amounts of hydrogen peroxide used as an oxidant, were examined for higher mechanical properties of the fibers. The optimum conditions, namely a coagulation bath of tetrahydrofuran, 10 minutes of oxidation, and oxidation bath of dimethylsulfoxide, gave highest mechanical properties such as Young’s modulus of 10.1 GPa and stress at break of 61.6 MPa, higher than those of the uncrosslinked SH-CNW fibers.