CELLULOSE BEHAVIOUR IN NaOH/THIOUREA/UREA AQUEOUS SOLUTIONS

Cellulose rapidly dissolves in an 8 wt% NaOH/6.5 wt% thiourea/8 wt% urea aqueous solution pre-cooled at -8 degrees C. Compared to NaOH/thiourea and NaOH/urea aqueous solutions. the solvent system shows low toxicity and higher solubility towards cellulose. To elucidate the rheological behaviour of the solution system, the prepared cellulose solution was investigated by steady and dynamic viscoclastic measurements, as well as by the falling ball method. The viscoelastic behaviour of the cellulose solutions evidenced the expected viscosity dependence oil concentration. Irreversible sot-gel transition occurred under both heating and cooling, the solution prepared with the new solvent appearing stable at 0 degrees C. It was also confirmed that the cellulose dissolved ill NaOH/thiourea/urea/H2O was more stable than that dissolved ill NaOH/thiourea/H2O and NaOH/urea/H2O. The activation every and structural viscosity index of the cellulose solution were figured out, to determine the spinnability of the cellulose solution, which suggested that it was not a molecular solution, the cellulose molecules ill solution forming micelles instead of being separated as single molecules.