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.