Dimension change in microfibrillated cellulose from different cellulose sources by wet disk milling and its effect on the properties of PVA nanocomposite

Microfibrillated cellulose (MFC) with different geometrical characteristics was prepared from three different cellulose sources (pure cellulose, holocellulose, and kraft pulp) using a wet disk milling (WDM) process. The dimension, specific surface area, and relative crystallinity of the MFCs varied with WDM time. The effect of WDM time on the dimensions of MFCs was investigated with atomic force microscopy, revealing that the length and diameter of MFCs decreased with increasing WDM time. The specific surface area and relative crystallinity increased and decreased with WDM time, respectively. MFC-reinforced polyvinyl alcohol (PVA) nanocomposites were prepared by film casting. The tensile strength and elastic modulus of the nanocomposites increased with decreasing MFC dimension and increasing MFC content. There was no significant difference in tensile properties among the nanocomposites reinforced by three different MFCs at the same level of WDM time. The thermal stability of the PVA matrix improved with increasing MFC content. Crystallization temperature of PVA was increased by the addition of MFC, whereas crystallization enthalpy, heat of fusion, and melting temperature all decreased.