Concentrated kaolin pulps are utilized as coatings in the chemical industry. During pulp application, high shear rates are obtained. Elevated shear rates associated to high viscosities incite difficulties on the lamina movement generating risks, bubbles or even tearing the paper. To minimize this effect pH adjustment and addition of dispersant agents to the pulp are made. The aim of this work was to study the colloidal behavior of the Coat 90 Prado region (Bahia State) kaolin pulps, through zeta potential and rheological evaluations combined with the classical DLVO theory. The data analysis showed that the pulps presented thixotropic behaviour and that the apparent pulp viscosity, at the same shear rates and time intervals, first reduced with pH increasing and then stablized at a particular constant pH value. On the other hand, there is a total interaction energy value which provides a maximum degree of stability/dispersion to the pulp.
Kaolin; surface chemistry; DLVO theory
