A Quantitative study of polymeric dispersant adsorption onto oxide-coated titania pigments

Polyacrylic acid salts and similar copolymers are used extensively in the coatings industry to disperse oxide-coated titania pigments. The effect of polymer adsorption onto the pigment can vary widely depending on polymer composition, pigment surface treatment, and solution properties such as pH and ionic strength. This investigation examines the effect of molecular weight on the adsorbed layer thickness and stabilizing action of polyacrylic acid dispersants. In order to understand the stabilization mechanism, a DLVO model was used in which the surface treatment layer of the pigment and the adsorbed layer thickness of the dispersant were taken into account. It was found that only this level of detail could account for the degree of stability found in pigment suspensions. Layer thickness and adsorption isotherms indicate that the dispersant molecules do not adsorb completely flat to the pigment surface but with enough loops and tails to provide some electrosteric stabilization. (C) 1999 Elsevier Science S.A. All rights reserved.