Effect of different alkaline solutions on crystalline structure of cellulose at different temperatures

Abstract

Effect of alkaline solutions such as 10% NaOH, NaOH/urea and NaOH/ethylene glycol solutions on crystalline structure of different cellulosic fibers (cotton linter and filter paper) was investigated at room temperature and −4°C. The highest dissolution of cotton linter and filter paper was observed in NaOH/ethylene glycol at both temperatures. X-ray patterns of treated cotton linter with different alkaline solutions at low temperature showed only two diffractions at 2θ=12.5° and 21.0°, which belonged to the crystalline structure of cellulose II. CP/MAS 13C NMR spectra showed the doublet peaks at 89.2ppm and 88.3ppm representing C4 resonance for cellulose I at room temperature, Whereas, at low temperature the doublet peaks were observed at 89.2ppm and 87.8ppm representing C4 resonance for cellulose II. Degree of polymerization of cellulose plays an important role in cellulose dissolution in different alkaline solutions and temperatures, where, a low temperature gives high dissolutions percentage with change in crystalline structure from cellulose I to cellulose II forms.