Improvement to the solubility and reactivity of purified bamboo fibers using a combined chemi-mechanical process

Abstract

Bamboo fibers exhibit poor solubility and reactivity because of the aggregational structure of cellulose macro-molecules in fiber cell walls. It has been shown that more free hydroxyl groups on cellulose molecules can be exposed via fibrillation of the fiber walls during a PFI beating process. The changes in fiber characteristics, such as the fibrillation degree, water retention value (WRV), and crystallinity, were analyzed. The results showed that the fiber fibrillation increased from 0.781% to 1.072%, and the WRV increased from 112.8% to 213.6% during the beating process, indicating that a fibrillation effect was present in the bamboo fiber walls that corresponded to an incremental change in the degree of mechanical pretreatment. The saturated solubility value of the treated fibers in an alkali/urea solvent system at low temperature increased from 0.22 wt.% to 2.69 wt.% with an incremental change in the degree of mechanical pretreatment. After high-revolution PFI beating, the cellulose crystallinity index of the samples decreased from 66.4% to 50.0%, but the intrinsic viscosity changed only slightly. The oxidation degree of the cellulose in the treated samples increased from 0.85 mol/AGU to 1.03 mol/AGU, which suggested that the reagent accessibility and chemical reaction performance of the bamboo fibers were both improved.