Effect of stirring conditions on cellulose dissolution in NaOH/urea aqueous solution at low temperature

Cellulose can be dissolved in precooled (-12 degrees C) 7 wt % NaOH/12 wt % urea aqueous solution within 2 min as a result of a dynamic self-assembly process among solvent molecules (NaOH, urea, and water) and cellulose macromolecules. The dispersion condition of cellulose could play an important role on the formation of cellulose inclusion complex, leading to good dissolution (Cai et al., Macromolecules 2008, 41, 9345). Therefore, the stirring conditions on the cellulose dissolution in NaOH/urea were studied in this work. The results from solubility experiments, optical microscope images, and rheology experiments suggested that lager stirring blade area, longer stirring time, and higher stirring rate could improve the saturated solubility value (Cmax) of cellulose. However, when Cmax value reached a maximum, it changed hardly with further increasing stirring time and rates, which could be regarded as complete dissolution of cellulose in NaOH/urea. Moreover, a schematic diagram of the cellulose solubility had been made, as an instruction of cellulose dissolution in NaOH/urea. The DLS experiments displayed a similar rule. On the other hand, the Cmax values could be significantly enhanced by decreasing the stirring environment temperature, and the favorable environment temperature range was from -10 to -5 degrees C. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012