TBAH/Urea/H₂O solvent for room temperature wet-spinning of cellulose and optimization of drawing process

TBAH(tetra-butylammonium hydroxide)/Urea/H₂O solvent has been applied for the solvent wet-spinning of cellulose, due to its room temperature operation, good stability and spinnability of the cellulose solution, as well as the unconditional string of low DP (degree of polymerization) for dissolving cellulose. Most importantly, it is found that the stability of the cellulose solution can be dramatically improved by the addition of urea, as indicated by the rheological property of the cellulose solution. With the help of urea, it has been preliminarily studied about the effect of the drawing process, including t_nf (time for the formation of nascent fiber in coagulation bath), δ₁ (primary drawing ratio) and δ₂ (secondary drawing ratio), on the orientation structure and the mechanical performances of the spun fibers. The correlations between the drawing process and the mechanical performance have been established by mathematical models. The tensile strength of the spun fibers improved up to ca. 96% (1.3 cN/dtex) through our optimization of the drawing process. Morphological observations indicated that the spun fibers exhibited regular shape with a circular cross-section. X-ray diffraction and scattering analysis demonstrated that the orientation structure of fibers spun by TBAH/Urea/H₂O is similar to that of the commercial viscose and Tencel fibers.