Effect of varying hydrolysis time on extraction of spherical bacterial cellulose nanocrystals as a reinforcing agent for poly(vinyl alcohol) composites

Abstract

Bacterial cellulose nanocrystal (BCNC) was prepared from bacterial cellulose (BC) using acid hydrolysis for 12, 24 and 72 h. The effect of the BCNC was estimated as a means of reinforcing the poly(vinyl alcohol) (PVA) matrix in terms of mechanical and thermal properties. The effect of the hydrolysis time on BCNC extraction was evaluated by considering morphology, changes in chemical functional groups, crystallinity and thermal stability. Atomic force microscopy (AFM) images revealed the diameters of spherical cellulosic particles were in the range 16–35 nm with the smaller ones resulting from a longer hydrolysis treatment time. Fourier transform infrared (FTIR) spectroscopy showed no changes in the functional groups between BC and BCNC samples for all hydrolysis extraction times. However, X-ray diffraction (XRD) proved that the crystallinity of the BCNC increased up to 87% in comparison with the BC. The thermal stability of nanocellulose decreased over a longer hydrolysis period. Furthermore, the BCNC showed an improved effect on the PVA matrix in both tensile and thermal analysis. Therefore, BCNC obtained by acid hydrolysis for 24 h could be used as a reinforcing agent for material industries.