Regenerated cellulose films from NaOH/urea aqueous solution by coagulating with sulfuric acid

A series of novel regenerated cellulose (RC) films was prepared from cotton linters in 6wt% NaOH/4wt% urea aqueous solution by coagulating with 1-20 wt% sulfuric acid (H2O4) aqueous for 1-20 min. Dependences of structure, morphology, light transmittance, mechanical properties, and water permeability of the films on the H2SO4 concentration and the coagulation time were investigated by using IR, UV-Vis, x-ray diffraction, scanning electron micrograph, tensile testing, membrane osmometry, etc. All of the films exhibited homogeneous porous structure on the surface, but different inner architectures for the various coagulation conditions. The tensile strength and breaking elongation of the films decreased with increasing H2SO4 concentration and the coagulation time, and the highest tensile strength (97 MPa) of the films was obtained by coagulating with 5 wt% H2SO4 for 2 min. The H2SO4 concentrations have significantly more influence on the structure and properties of the films than the coagulation time. The novel RC films displayed larger pore size and higher water permeability than those of RC films prepared from cellulose cuoxam, and the pore sizes could be adjusted by changing the H2SO4 concentration. This work provided an optimal coagulation condition for preparing RC films in the solvent system and scientific information for controlling the properties and pore sizes of the films.