The importance of explicitly considering interparticle interactions in Ihe rheology of dense suspensions and particle slurries is well established, although the exact relationships between particle-level quantities and macroscopic rheology and stability are at best qualitative. Most of the understanding has been developed follow shear rheological (linear viscoelastic) properties and/or for dilute dispersions. This project has the goal of providing experimental evidence for the influence of interparticle surface forces and hydrodynamic forces (due to the presence of the solvent) on the moderate to high shear rheological properties and shear stability of dispersions that span the colloidal to particulate range (colloidal dispersions to slurries). Of particular interest is the shear thickening transition and dilatancy, and how that, explicitly depends on the strategy used to stabilize the dispersion or slurry (i.e. steric, electrostatic, polymeric stabilization), as well as the hydrodynamic forces irnport,ant at higher shear rates. The research to date has the following components:
- Systematically explore the influence of the basic methods of parrticle stabilization on the shear thickening and dilatancy of well-characterized colloidal dispersions and slurries of non-colloidal particles. In this report, in particular, the effect of added adsorbed polymer on the rheology is studied for explicit comparison to sirriulation results.
- Use the experimental data to develop simple force-balance based models for predicting the onset of shear thickening, as well as for use by formulators to prevent shear thickening.