Surface roughness effect on the shear thinning of non-colloidal suspensions

Abstract

The shear thinning behavior of non-colloidal suspensions is investigated experimentally with emphasis on the effect of surface roughness of suspending particles. The first shear thinning at a low shear-rate is observed, which originates from particle–particle interaction, and the second shear thinning at a high shear rate is also reported as the polymeric solvent shear thins. Due to the decrease of the size of particle clusters, the viscosity of suspensions decreases in the first shear thinning regime. The surface asperities on rough particles hinders the lubricative interaction between close-contact particles suppressing the growth of clusters, and therefore, the first shear thinning behavior weakens. The shielding of the lubricative interaction also prevents the local shear rate enhancement, corresponding to the suppressions second shear thinning and the rising of a second-order first normal stress difference from the polymeric solvent. A theoretical model describing the first shear thinning behavior of non-colloidal suspension is developed, and the predications agree well with experimental data. The roughness effect on dynamic rheological behavior is also investigated.