Enhancement of Regenerated Curdlan Fibers with High Wet-Ductility via Post-Drawing in Water

Biomass-derived biodegradable fibers have attracted considerable attention as sustainable alternatives to petroleum-derived non-biodegradable synthetic fibers. Curdlan, a linear β-1,3-glucan, is a promising renewable resource that exhibits unique physicochemical properties owing to its triple-helical crystalline structure. The regenerated fibers of curdlan can be fabricated by wet spinning; these fibers exhibit excellent ductility but poor mechanical strength compared to other polysaccharides such as cellulose. In this study, a new post-treatment was developed to enhance the mechanical properties of regenerated curdlan fibers by exploiting their high ductility when swollen with water. Curdlan was dry-jet wet spun using an ionic liquid as the solvent and water as the coagulant. The regenerated fibers were subsequently post-drawn in water to a maximum of four times the original fiber length, followed by air-drying. The resultant fiber showed a 1.4-fold increase in the briefringence (Δn) value, which represents the orientation degree; moreover, the tensile strength was two times higher (20 cN tex‒1; 300 MPa) than that of the untreated fiber. It was also observed that an increase in the degree of post-drawing was more effective in enhancing the regenerated curdlan fiber than an increase in the initial draw ratio from 10 to 20 during wet spinning.