The Effect of Nanocellulose Surface Properties on the Corresponding Wet-Spinning Process for Man-Made Fibers: Extrusion, Coagulation, and Drying

Utilizing the elementary building blocks of plant cell walls, cellulose nanofibrils (CNFs), can give final materials excellent mechanical properties. For instance, CNF-based wet-spun fibers exhibit superior mechanical properties, surpassing their source materials, plant fibers. Such high mechanical performance is closely related to CNFs' orientation; thus, most previous research has focused on optimizing spinning rates or introducing post-stretching to enhance this parameter. In this study, the effects of the CNF surface properties on CNF orientation were investigated, which are often neglected in the literature: 1) during extrusion, the CNF surface properties affect the rheological behaviors of the spinning suspension, which in turn influences CNFs' orientation potential; 2) during coagulation, they govern the affinity between CNFs and antisolvents, thereby determining the shrinkage of CNF gels; 3) during drying, they directly impact capillary forces induced by the evaporation of antisolvents, which significantly determine the CNF orientation in the end products. Overall, this fundamental study provides deeper insights into the assembling behavior of colloidal nanoparticles such as CNFs, which can advance the development of high-performance man-made fibers.