DISPERSION OF TITANIUM-DIOXIDE AGGLOMERATES IN VISCOUS MEDIA

The dispersion behavior of titanium dioxide agglomerates in viscous media was studied. Under application of shear within a cone-and-plate device, the titanium dioxide agglomerates primarily dispersed by an erosion process in which small fragments separate from the surface. The cohesiveness of unwetted powder was quantified using a compression test method. In some cases, the shear stress necessary to produce erosion was found to be an order of magnitude smaller than the measured cohesivity. Medium infiltration within agglomerates was assessed through observation.of penetration of the medium into powder compacts. The kinetics of the erosion process was highly sensitive to the overall porosity of the agglomerates. In the case of high porosity, the erosion rate depends on the speed of medium infiltration within the agglomerate, and the strength of the applied shear stress. A relatively wide size distribution of fragments was observed. For low-porosity agglomerates, the erosion process depends on the magnitude of shear stress, the cohesive strength of the agglomerates, and agglomerate-medium interactions. A narrower distribution of fragments, having smaller mean size, was observed.