Dissolution of cellulose from different sources in an NaOH/urea aqueous system at low temperature

摘要

The dissolution of different cellulose pulps from different sources such as wood, bamboo and ramie pulp in 7 wt% NaOH/12 wt% urea aqueous solution was investigated in the present article, as well as the structure and properties of the resultant regenerated films. All of the cellulose samples with molecular weight below 1.2 x 10(5) could be quickly and completely dissolved in NaOH/urea aqueous solution precooled to -12.5 degrees C in 2 min, regardless of the cellulose source, indicating the universality of cellulose dissolution in NaOH/urea solvent. The resultant cellulose solutions exhibited similar rheological behaviors, indicating a similar solution procedure of cellulose in NaOH/urea. These regenerated cellulose films exhibited similar structures and morphologies according to the results of the scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscopy analyses, indicating a microporous structure with a pore diameter ranging from 100 to 300 nm, as well as a complete transition from cellulose I to cellulose II after the dissolution and regeneration process. Furthermore, all of the films had good mechanical properties and light transmittance as a result of the homogeneous structure. In view of the results mentioned above, the NaOH/urea solvent system displayed a strong cellulose dissolving capacity, exhibiting great potential for the further development and comprehensive utilization of cellulose from agricultural and forestry wastes. It is capable of increasing the applications of cellulose and has potential for further development.