Structure and Properties of Regenerated Cellulose Fibers Based on Dissolution of Cellulose in a CO2 Switchable Solvent

Development of an effective, nontoxic, and easy-to-process novel cellulose dissolution system for the preparation of regenerated cellulose fibers is of great importance and necessity for a greener and more sustainable future, with which the traditional viscose process with serious pollution can be gradually substituted. Herein, we demonstrated the successful utilization of a CO2 switchable solvent, a novel cellulose derivative dissolution system resembling viscose but without releasing toxic gases such as CS2 and H2S, for the preparation of regenerated cellulose fibers. The corncob cellulose raw material can be readily dissolved completely after the capture of CO2 in dimethyl sulfoxide (DMSO) with 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), resulting in cellulose spinning dope with high stability. Results showed that regenerated cellulose fibers with smoother surface morphology, a higher degree of crystallinity, and satisfactory mechanical properties were obtained under mild conditions with relatively slower double diffusion. Moreover, drawing treatment further increased the degree of crystallinity and orientation and the mechanical properties. All fibers had a dense structure, circular cross sections, no fibrillation, and high thermal stability. The regenerated cellulose fibers had degrees of crystallinity and orientation and tensile strength of 75.3%, 0.82, and 1.05 cN/dtex and 68.4%, 0.82, and 1.00 cN/dtex, respectively, in water and 30 vol % DMSO coagulation baths with a drawing ratio of 2.0 and 1.5, respectively. This work illustrated that the CO2 switchable solvent, which could be considered as "green viscose", is a good candidate with great potential for the preparation of regenerated cellulose fibers with high performance and various functionalities in the future.