| Popis: |
Extremely high shear rates are applied to pigment dispersions during various scale-up and manufactring processes in several industries. As reported in this paper, one has to know the rheological properties of dispersions under high shear, which can not be estimated but have to be measured under similar conditions. Carbonate and clay slurries exhibit a maximum in viscosity with increasing shear rate, responsible for failures in coating processes. Several additives under investigation shift the maximum towards higher shear rates and reduce its height. Water-soluble polymers might even level it off, depending on their molecular weight and molecular weight distribution. It is concluded that the polymers stabilize the liquid layer around the particles. Hence, shear forces may disaggregate floes, but will not increase the interparticle repulsion. |
