Wet spinning of cellulose nanofibers via gelation by alkaline treatment
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ORIGINAL RESEARCH
Wet spinning of cellulose nanofibers via gelation by alkaline treatment Kentaro Abe
. Momoyo Utsumi
Received: 6 June 2020 / Accepted: 12 September 2020 Ó Springer Nature B.V. 2020
Abstract Wet-spun fibers were prepared from plantbased 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. K. Abe (&) M. Utsumi Research Institute for Sustainable Humanosphre, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan e-mail: [email protected]
Keywords Cellulose nanofiber Wet spinning Alkaline treatment Gelation Interdigitation
Introduction Cellulose is widely used in the fiber and textile industries due to its high mechanical strength, low toxicity, and good biocompatibility. In addition to being produced from cotton fibers, cellulosic fibers now can also be derived from regenerated cellulose and cellulose derivatives. Currently, wood pulp and cotton are the main sources of cellulose fibers and contain natural cellulose as crystalline microfibrils with a diameter of * 3 nm and length of several micrometers. Microfibrils from wood and other plant sources have desirable physical and morphological properties and are isolated as cellulose nanofibers (CNFs). Such CNFs have become popular as an emerging bio-based nanomaterial with potential for use in a wide range of applications in the biomedical, pharmaceutical, and tissue engineering fields. Recent studies have explored the spinning of CNFs. Regenerated cellulosic fibers generally exhibit deteriorated mechanical properties due to the crystal conversion from cellulose I to cellulose II during processing. Indeed, Nishino et al. (1995) estimated the longitudinal elastic moduli of the crystalline regions of natural cellulose I and cellulose II to be 138 and 88
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