Dispersion of Al2O3 suspension with acrylic copolymers bearing carboxylic groups

The interaction between acrylic copolymers carrying carboxylic groups and the surface of an alumina powder in water has been studied. The trends of the adsorption isotherms suggest the formation of a monolayer according to the Langmuir model. The quantity absorbed on the plateau increases when the fraction of carboxylic groups on the polymer decreases. The electrokinetic properties of the alumina suspensions were also analysed. Results indicate that the copolymer adsorption leads to a shift in the IEP towards acidic pH. Moreover, the density of charge of the surface of alumina particle at pH 8–9 was found to depend on the quantity of adsorbed carboxylic groups and on the configuration of the adsorbed polymer. The stability of dispersions was investigated through particle size distribution and rheological properties after addition of various amounts of copolymers. The ability of the acrylic copolymer to stabilise alumina suspensions was found to be greatly affected by the content of carboxylic groups contained in the macromolecular chain.