DISSOLVED STATE AND VISCOSITY PROPERTIES OF CELLULOSE IN A NaOH COMPLEX SOLVENT

Cellulose may be quickly dissolved in a NaOH complex solvent (NaOH/urea/thiourea/H2O). A detailed investigation on the effects of solvent composition and temperature on cellulose solubility has been presented. Optical microscopy and wide-angle X-ray diffraction (WAXD) were used to study the process of dissolution. The highest solubility of cellulose was recorded in NaOH/urea/thiourea/H2O with an 8/8/6.5/77.5 composition, at –10 °C, although the components of this solvent cannot dissolve cellulose on their own, even at a low temperature. CP MAS C NMR spectra proved that, during regeneration, cellulose I (cotton linters) first changed to amorphous cellulose chains in solution and then to cellulose II. The intrinsic viscosity [η] of the cellulose solutions revealed that the cellulose complex occurs as flexible coil chains in the NaOH/urea/thiourea aqueous system, the chain stiffness of cellulose being higher than that of normal synthetic polymers, in a good solvent. According to relative viscosity measurements, the cellulose solution was stable during the storage stage.