A Critical Evaluation of Dispersants: Part II. Effects on Rheology, pH, and Specific Adsorption

Six dispersants commonly used in the whiteware industry were evaluated in a typical whiteware body composition suspension and a clay suspension. The dispersants evaluated included the sodium salts of polyacrylic acid, polymethacrylic acid, silicate, carbonate, phosphate, and 1:1 (carbonate:silicate). The 1:1 dispersant was also evaluated as a function of the addition sequence of carbonate and silicate. Apparent viscosity and pH were measured for all dispersants, and zeta potential measurements were taken on sodium polyacrylic acid, carbonate, and silicate, in the clay suspension. The apparent viscosity values were used as a measure of dispersant effectiveness. The six dispersants were either highly effective (polyacrylic acid, polymethacrylic acid, silicate, phosphate, and 1:1) or ineffective (carbonate). The rheological behavior of the 1:1 dispersant was indifferent to the addition sequence of its components, but could be affected by the suspension preparation method. The specific adsorption tendency of ionic species was determined and indicated that the anions were responsible for dispersion.