Rheological behavior of highly concentrated aqueous calcium carbonate suspensions in the presence of polyelectrolytes

We investigated the rheological properties of concentrated aqueous suspensions of calcium carbonate in the presence of polyelectrolytes; namely, a linear homopolymer and a comb-grafted copolymer. We mainly discuss the effects of volume fraction of particles, polymer concentration and polymer structure on the apparent viscosity at high shear rate and yield stress. The flow behavior of the concentrated suspensions that contained a polymer can be explained by the difference of the repulsive force among particles, induced by the adsorbed polymer. Moreover, we observed that the effect of polymer on dispersibility is more pronounced in the steric hindrance behavior rather than the electrostatic behavior. The size of agglomerates in the suspension can be estimated by the critical pigment volume concentration (CPVC). The agglomerates in the suspension without polymer consisted of some hundreds of primary particles and the agglomerates became smaller when the polymer concentration was increased. Furthermore, the agglomerates in the suspension stabilized by steric repulsion were smaller than those stabilized by electrostatic repulsion.