Effect of polymer molecular weight on adsorption and suspension rheology

Abstract

The adsorption of poly(acrylic acid) [PAA] on the surface of commercial ball clay was studied. The adsorption isotherm of PAAs with different molecular weights was determined at pH 6 and 9. The results showed that the amount of PAA adsorbed on clay was independent of molecular weight. Also, the adsorption amount was decreased with increased pH. However, the overall adsorption amount was lower than the range predicted by a model based upon the mineralogy of kaolinite. A kinetic study of PAA adsorption presented plausible displacement of initially adsorbed PAA. PAA adsorption on clay particles decreased the viscosity of suspensions. Clay suspensions showed the minimum viscosity with a sufficient coverage of particles with PAA necessary for stable suspensions. Optimum chain length of PAA was revealed for effective dispersion.