Green and Economical Strategy for Spinning Robust Cellulose Filaments

A green, low-cost, and efficient processing technology to spin regenerated cellulose multifilaments has attracted much attention in the textile field. Herein, robust cellulose filaments were produced from a cellulose solution in a NaOH/urea/ ZnO aqueous system with a relatively high concentration (7.5 wt %) via the wet-spinning technique by coagulating in cheap and renewable 15 wt % citric acid/5 wt % trisodium citrate/40 wt % glycol at low temperature, followed by drawing in a 5% sulfuric acid bath. In our findings, the solubility and the solution stability were significantly improved by introducing 0.8 wt % ZnO, and the cellulose chains self-aggregated in parallel to form nanofibers through hydrogen bonding, as a result of the relatively slow exchange ratio between the coagulator and solvent. Moreover, the nanofibers with an average diameter of 30-50 nm were aligned to the fiber direction by stretching orientation in the second sulfuric acid coagulator, leading to the further enhancement of the filament strength. The nanofibril-structured cellulose fibers exhibited a high orientation degree of 0.85 and an excellent tensile strength of 2.92 cN dtex(-1). The wet-spinning process only took 8 h, and our production costs were as cheap as viscose, which was an efficient, low-cost, and green process without the discharge of toxic substances. Furthermore, the 80-160 nm ZnO nanoparticles could be generated into cellulose filaments for achieving ultraviolet and static resistance. This work provided a green and economical strategy for spinning robust cellulose filaments. Such a technology is being industrially trialed by cooperating with Yibin Grace Co. Ltd in China, showing potential impact on the sustainability in the industry, economy, and environment.