TiO2 Pigment Suspension Behaviour upon Adsorption of Polymeric Dispersants

The influence of polymeric dispersants containing different functional groups on TiO2 pigment particle suspension was investigated at pH 6.0 and 9.5, using rheology and particle size data. The dispersants chosen were polyacrylic acid and modified polyacrylamides including homo and copolymers modified with carboxylate and/or hydroxyl groups. The pigment suspension was strongly affected by both pH and dispersant functional groups. The pigment suspension exhibited a maximum yield stress and particle size at the pigment isoelectric point. The presence of carboxylate groups in both polyacrylic acid and anionic polyacrylamide copolymer altered the pigment dispersion behaviour, reducing the suspension yield stress and mean particle size. The polyacrylamide homo-polymer had negligible effect on the pigment dispersion properties at pH 9.5, while it caused pigment particle aggregation at pH 6.0. The hydroxyl-modified polyacrylamide had negligible effect on the pigment dispersion at pH 6.0, but decreased the yield stress and the mean particle size at pH 9.5.