Mechanical and thermal properties of rice straw cellulose nanofibrils-enhanced polyvinyl alcohol films using freezing-and-thawing cycle method

Abstract

This study investigated effects of loadings of rice straw (Oryza sativa L.) cellulose nanofibrils (CNFs) defibrillated using the high-pressure homogenization technique on tensile property, glass transition temperature, and thermal stability of polyvinyl alcohol (PVA) matrix. CNF loadings had five percentage levels by weight of final composite, i.e. 0, 0.03, 0.08, 0.12, and 0.17%, respectively. A freezing-and-thawing cycle method cast PVA/CNF-mixed and PVA-only films. Experimental results showed that PVA films with 0.03% CNFs had average tensile strength of 50.8 MPa and modulus of 707 MPa, which were 32 and 21% higher than neat PVA ones, respectively. In addition, the glass transition temperature values of PVA/CNF-mixed film increased from 51.6% to 82.6% with increasing the amount of CNFs. The thermogravimetric analysis showed that PVA/CNF-mixed films had significantly higher thermal stability than PVA-only films. The shift of the O–H stretching vibration peak in PVA/CNF-mixed films indicated a good compatibility between CNFs and PVA matrix.