Processing and rheological properties of polyol/cellulose nanofibre dispersions for polyurethanes

Polyols are widely used as precursors, compatibilisers, and viscosity modifiers in the polymer, food, and paint industries, and their rheological properties are critical for engineering the optimal performance of final products and enabling new and diverse applications. This study investigates the mechanical and viscoelastic properties of a polyether polyol filled with long thin cellulose nanofibres (CNF). It provides insights into the influence of loading levels on mechanisms of dispersion, interaction, and gelation behaviour. The steady-shear rheological measurements revealed four different regimes of flow behaviour associated with increasing viscosity and yield stress with increasing loading of CNF in the polyol. The oscillatory-shear rheology enabled a better understanding of interactions of CNF dispersed in the polyol and the determination of the threshold concentration of CNF for percolation network formation. The correlation of mechanical properties of the polyol nanocomposites with Shih et al. suggests the network formation of intraflocs of fractal dimension two at the higher loadings of CNF.