Polymorphic transformation of cellulose I to cellulose II by alkali pretreatment and urea as an additive

The effect on crystalline structure transformation from cellulose I to cellulose II polymorph was studied of the cotton linter treated with NaOH with and without urea as an additive, analyzed by wide-angle X-ray diffraction analysis. Cotton linter treated with increasing NaOH concentration showed at 15 wt% sudden transformation from cellulose I to cellulose II polymorph. But when urea 5 wt% was used as additive along with 15 wt% NaOH concentration the magnitude of the transformation reduced largely. The crystallinity index showed a gradual decrease with increasing concentration of NaOH. The crystallinity index showed a gradual decrease with increasing concentration of NaOH with or without addition of urea, nevertheless with addition of urea a further slight more transformation was also observed. (C) 2013 Elsevier Ltd. All rights reserved.