Wet spinning of cellulose nanofibers via gelation by alkaline treatment

Wet-spun fibers were prepared from plant-based cellulose nanofibers (CNFs) via a novel approach proposed in a previous report. This method is based on the use of a simple NaOH treatment and the minimization of the use of harmful reagents. The CNF gels prepared using an 8% NaOH solution exhibited good preservation of the cellulose I crystal structure, contributing to the high tensile properties of the spun fibers. This study further explored this approach, and a CNF suspension with 8% NaOH was spun into a 2% sulfuric acid coagulation bath at different spinning rates (1–100 m/min). Straight long fibers with a circular cross-section were obtained at all spinning rates. The orientation index of the CNFs and the tensile properties of the CNF spun fibers increased slightly with increasing spinning rate. However, these values were lower than the values expected based on the previous reports. The aggregation of CNFs in the NaOH solution likely affected these properties. Nevertheless, the advantages of this method, namely the lack of use of toxic solvents and the minimal use of organic solvents, were demonstrated. Furthermore, a high wet strength can be expected due to the formation of interdigitated linkages between the CNFs. These CNF filaments are promising for applications in smart textiles, biosensors, and structural reinforcement.