Mathematical regression models for rheological behavior of interaction between polymer-surfactant binary mixtures and electrolytes

Abstract

The characterization of the rheological behaviors of polymer-surfactant binary mixtures is important in several applications and industrial processes. In this paper, rheological behaviors of partially hydrolyzed polyacrylamide (PHPAM) polymer and sodium dodecyl sulfate (SDS) surfactant solutions have been investigated through viscosity measurement and then mathematical regression modeling. The effects of salt (CaCl2) and alkali (NaOH) on the viscosities of these polymer-surfactant solutions have also been experimentally investigated and theoretically modeled. All polymer-surfactant systems are found to exhibit shear-thinning non-Newtonian behavior. The experimental investigations revealed that addition of salt extensively reduced the viscosity of polymer-surfactant solutions by reducing the hydrodynamic size of polymer and this peculiar effect has been explained in terms of electrical double layer (EDL). The non-Newtonian polymer-surfactant solutions became almost Newtonian when the concentration of CaCl2 exceeded some threshold value (≥4.5 × 10−2 mol.L−1 or 0.5 wt%). Presence of NaOH also reduced the viscosity significantly and explained using the theory of molecular dynamics. The Herschel–Bulkley power law model through mathematical regression fitting procedure has been used to estimate the yield stress (τ 0), the consistency index (k) and the flow behavior exponent (n) and analyze the rheology results.