CELLULOSE NANOCRYSTALS FROM COTTON STALK FOR REINFORCEMENT OF POLY(VINYL ALCOHOL) COMPOSITES

This paper presents an efficient method for extracting cellulose and cellulose nanocrystals (CNCs) from waste cotton stalks. The chemical composition, crystallization, spectroscopic, thermal and morphological analyses of the cotton stalks in every step were performed by relevant tests. Results indicated that the cotton stalks, which were treated by 12.5% sodium hydroxide concentration at 160 degrees C for 1 hour, retained the highest contents of cellulose (68.5%), while maintaining the cellulose crystal type I. An acidified NaClO2 bleaching was subsequently introduced to remove the residual lignin component. Finally, cellulose nanocrystals were successfully extracted from cotton stalks by 65 wt% sulfuric acid hydrolysis at 50 degrees C. The reinforcing efficiency of the extracted CNCs in poly(vinyl alcohol) (PVA) composites was also investigated. Results showed that 3 wt% of CNCs could improve both the tensile strength and modulus of PVA by 48.3% and 21.1%, respectively. The work offers a promising approach to utilizing an abundant agricultural waste, such as cotton stalks.