Preparation of All-Cellulose Composite Fiber Reinforced by Cellulose Nanofibrils Based on CO<sub>2</sub> Switchable Solvent

In this paper, cellulose solution was obtained by dissolving cellulose in CO 2 switchable solvent, and the CNF spinning solution was prepared by mixing cellulose solution with cellulose nanofibrils (CNF) by physical blending. CNF reinforced all-cellulose composite fibers were prepared by wet-spinning. The spinning solution with good dispersion of CNF can be obtained. The rheological property test showed that the solution has spinnability. The composite fibers were subsequently prepared by wet-spinning. The structure and properties of the composite fibers were analyzed by FT-IR, XRD, SEM, TGA, and mechanical properties testing. The results showed that the chemical structure of the composite fiber was the same as that of cellulose, but the aggregate structure became amorphous, which resulted in deceased thermal stability. The composite fibers had dense and solid structure without any cavity. The mechanical strength of the composite fiber was upto 1.12cN/dtex.