Effect of a comb-like amphiphilic polymer on the stability of alumina dispersions

The effect of a hydrophobically modified anionic polymer (a maleic anhydride α-olefin copolymer. DAPRAL), which has a comb-like structure, on the stability of alumina suspensions was studied. In the absence of the polymer the suspension stability is controlled by the electrostatic repulsion between particles. Addition of DAPRAL was found to have a significant effect only when the electrostatic repulsion was not sufficient to maintain a stable suspension. The zeta potential of alumina particles and the adsorption density of DAPRAL on alumina were also measured in order to develop the underlying mechanisms for the stability changes. The results suggest that interactions between hydrocarbon chains on the dangling loops and tails do reduce the effect of electrostatic repulsion between alumina particles at low polymer concentrations. At higher polymer concentrations, the hydrocarbon chains on such loops and tails form micellar aggregates; the stability of the suspension is drastically enhanced under such conditions by both steric and electrostatic repulsion.