Nanocellulose fibrils isolated from BHKP using ultrasonication and their reinforcing properties in transparent poly (vinyl alcohol) films

Nanocellulose fibrils (NCFs) were isolated from bleached hard kraft pulp (BHKP) using high-intensity ultrasonication, and their reinforcement capabilities for poly (vinyl alcohol) films were investigated. Scanning electron microscopy (SEM), thermogravimetric analysis (TG), and X-ray diffraction (XRD) were used to characterize the fibrils and films. The results revealed that the prepared NCFs were long filaments with a cellulose I crystal structure. The filaments were 50-150 nm in diameter, and had lengths longer than 500 mu m. The crystallinity and thermal stability of the NCFs were increased compared with BHKP because of the removal of hemicellulose. A NCFs content of 4 wt% was found to give the best light transmittance and mechanical properties in the PVA composites. The PVA composites exhibited a visible light transmittance of 75 %, and the tensile strength and Young's modulus were significantly improved, with values 1.86 and 1.63 times larger than that of neat PVA.