Rheology of Suspensions of Solid Particles in Liquids Thickened by Starch Nanoparticles

Abstract

This study explores the rheological characteristics of suspensions containing solid particles dispersed in aqueous matrix phase thickened with starch nanoparticles (SNP). The SNP concentration ranged from 5 to 35 wt% relative to the aqueous matrix phase, while the solids concentration of the suspensions varied from 0 to 57 vol%. Two different size solid particles were used in the experiments. Observations revealed that suspensions at constant SNP concentrations exhibited Newtonian behavior at low solids concentrations but transitioned to non-Newtonian shear-thinning behavior at higher solids concentrations. Notably, an increase in SNP concentration led to an earlier onset of non-Newtonian behavior at lower solids concentrations. The rheological properties of non-Newtonian suspensions were effectively characterized using a power-law model, with the consistency index showing a positive correlation with suspension solids concentration at any given SNP level. Furthermore, the flow behavior index, indicative of shear-thinning behavior, decreased with increasing solids concentration, suggesting an amplification of shear-thinning tendencies in the suspensions. The effect of particle size on the rheological behavior of suspensions was found to be insignificant. Experimental viscosity and consistency data for both Newtonian and non-Newtonian suspensions aligned well with predictions from the Pal model.