Rheological Properties of Partially Hydrolyzed Polyacrylamide Solutions

Abstract

An experimental study was conducted to investigate the effect of salt on viscoelastic properties of partially hydrolyzed polyacrylamide Pusher 700 (Dow Chemical) in aqueous solutions. Viscosity η and primary normal stress differences N1, were measured on a Weissenberg rheogoniometer and a Contraves low‐shear viscometer. The experimental results show the well known stabilizing effect of salt on the solutions' viscosity (i.e., the solutions become less viscous and less shear thinning) up to a critical value of shear rate, γc, which depends on salt and polymer concentrations. For values of shear rate greater than γc, both η and N1 exhibit appreciable increases with increasing shear rate. The amplitude of the so‐called shear‐thickening phenomenon increases with increasing salt concentration. For γ>γc the presence of salt has no apparent effect on either η or N1 of the concentrated polymer solutions. For lower polymer concentrations, the addition of salt increases markedly the values of η and N1. The inves...