Association thickening of polymer latex dispersions

Low levels of addition of hydrophobically modified water-soluble polymers to dispersions of colloidal polymer latices dramatically alter their rheological behaviour as measured over a wide range of simple shear rates. This measured rheological behaviour for a variety of thickener-latex systems demonstrates that the thickening mechanism is not merely that of thickening the continuous phase, water. Clearly an association between the principal components of the dispersion, the polymer latex and the thickening polymer, takes place. Additionally, in coatings formulations, surfactants and cosolvents are present and these contribute to and alter the mechanism of the thickening process. A variety of mechanisms can be proposed which influence the observed thickening. A set of polymer latices and associative thickeners have been used to experimentally investigate the sensitivities of the interactions and their effect on the rheology of the system.