Solubility of cellulose in NaOH/urea aqueous solution

Abstract

NaOH/urea aqueous solution as solvent of cellulose including cotton linter, bagasse, alkali-soluble cellulose and Bemliese was studied by solubility analysis, viscometry and light scattering. The addition of 2-4 wt% urea significantly improved the solubility of cellulose in 6-8 wt% NaOH aqueous solutions, and moderate urea plays a role in improving solubility and avoiding the formation of cellulose gel. Celluloses I with viscosity-average molecular weight (Mη) of 6.7×104 were completely dissolved in 6 wt% NaOH/4 wt% urea aqueous solution. Cellulose dissolved in 6 wt% NaOH/4 wt% urea aqueous solution degraded slowly with storage time, and Mη of cellulose in the solution decreased 20% after storage for 100 days. The stability of cellulose solution was higher than cellulose cuoxam. A regenerated cellulose membrane having the tensile strength of 88.7 MPa and breaking elongation of 11% was successfully prepared by coagulating 4 wt% Bemliese solution in 6 wt% NaOH/4 wt% urea with 5 wt% CaCl2 then 1.3 wt% HCl aqueous solution as coagulate at 20 °C.