Characterization of a High Solids TiO\u3csub\u3e2\u3c/sub\u3e – Dispersant System at High Rates of Shear

The objective of this research was to study rheograms of high solids titanium dioxide dispersions at different dispersant levels. Viscometric measurements were collected with a Hercules High-Shear Viscometer. Viscosity was calculated using the initial slope of the increasing shear rate flow curve from the rheogram. This technique was incorporated to calculate viscosity in the laminar reagion up to the critical shear rate, where flow instability was expected to develop according to Taylor vortical flow calculations. The dispersant levels (dispex) were varied based on grams of titanium dioxide at varying percent solids levels. The results were evaluated according to a two-phase model for high solids dispersions at high shear rates. Based on this approach, the continuous (dispersing) phase is being sheared inside the effective gap determined by the volume occupied by the pigment solids. At the same solids volume concentration a parameter, defined as Relative Shear Volume (RS\u27V), was expected to indicate the packing array of solids under strong hydrodynamic conditions. It was found that upon increasing dispersant levels that the gap percent reduction decreased and the relative shear volume increased. These results indicated that the pigment particles were packed more efficiently under shear as the dispersant level increased