Influence of shear intensity during slip preparation on rheological characteristics of calcium carbonate suspensions

The shear forces developed during the preparation of ground calcium carbonate (GCC) suspensions by ball milling were varied by using different solids loading in the starting slurries. An ammonium polycarbonate was used as dispersant and two different molecular weight carboxyl methyl celluloses (CMC) were added as binder/thickening agents. The influence of shear intensity on the steady shear viscosity was studied by comparing the measurements made on the starting suspensions, at given solids loading, (non-diluted systems) with those performed on suspensions containing the same solids volume fractions but derived from more concentrated ones (60 vol.%) by adding the required amounts of water (diluted systems). Slip casting experiments were also performed in order to correlate the flow characteristics of the suspensions with their ability towards packing. The results demonstrated that, at a given solids loading, diluted systems are less viscous and pack better than non-diluted ones indicating that high intensity shearing during slip preparation enhances dispersion and deagglomeration of suspended powders, and that the rheological characteristics and packing behaviour can be further controlled by the processing aids.