Effects of nonionic surfactant and associative thickener on the rheology of polyacrylamide in aqueous glycerol solutions

The effect of a low molecular weight nonionic surfactant and an acrylic associative thickener on the rheology of polyacrylamide in aqueous glycerol solutions under steady shear was experimentally investigated. The nonionic surfactant (Tween20), associative thickener (Acrysol TT935) and polyacrylamide (Separan AP30) underwent complex molecular interactions in solution as reflected by rheological measurements. The surfactant also interacted with the glycerol solvent. The addition of surfactant in aqueous glycerol solutions reduced the surface tension, as well as the solution viscosity, at low surfactant concentration. The solution viscosity went through a minimum at certain surfactant concentration, depending on the composition of glycerol/water mixture, before increasing again. Similar behavior was found when the surfactant was added to the polyacrylamide solution, except there was an initial increase in the viscosity before the reduction. The associative thickener, Acrysol TT935 (an anionic acrylic emulsion copolymer) exhibited a strong affinity with polyacrylamide in solution, as indicated by a sharp increase in the solution viscosity. The dilute polyacrylamide solution became highly elastic in the presence of either the nonionic surfactant on the associative thickener. A threestage model was proposed to describe the surfactant/thickener/polymer interactions.