Latex thickening: Interactions between aqueous polymeric dispersions and solutions

Abstract

Abstract Latex thickening—the process of increasing the viscosity of a polymer emulsion by addition of a water‐soluble polymer —has been studied by rheological measurements and by the examination of other colloidal properties. For the systems studied, which represent a range of polymers in both the dispersion and solution phases, the flow curves were represented over a wide range of shear rate by the equation, S = K (τ − τ 0 ) 2 , where S is shear stress, τ is shear rate, and K and τ 0 are constants, of which the latter is considered to be a yield stress. Aside from the generality of the mathematical function, the behavior of various latex‐thickener pairs is extremely specific to the pair involved. Additional data on latex creaming and on the influence of the thickener and latex concentrations confirms the specificity. The available data indicate that latex thickening is not simply an enhancement of the viscosity of the aqueous phase by the thickener, but that in addition to this the ability of the thickener to flocculate or deflocculate the latex is an important part of the mechanism of thickening. These colloidal interactions change, often precipitously, with minor changes in the polymers, the latex emulsifier, and the concentrations of the components.