Dispersion of Cellulose Nanocrystals in a Water-Methanol Co-solvent System

Abstract

This study reports how a co-solvent system of water and methanol can be used to better disperse cellulose nanocrystals (CNC) into a polyvinylpyrrolidone (PVP) matrix through careful selection of mixing parameters and process steps. With appropriate order of mixing, a purely mechanical means of magnetic stirring and sonication provides good homogeneity without the need for chemical surface treatments of the CNC. The effect of preparation method on dispersion and solution rheology were characterized for CNC-PVP mixtures of up to 20% CNC by weight. A pre-dispersion of CNC into pure water before the addition of methanol was found to have a dramatic impact on the rate of agglomeration of CNC particles as well as the viscosity of the solutions of CNC-PVP-water-methanol. Birefringence measurements of the dried CNC-PVP mixtures demonstrate how the agglomeration is dramatically reduced through an appropriate predispersion step.