Stability and Rheological Behavior of Sulfonated Polyacrylamide/ Laponite Nanoparticles Dispersions in Electrolyte Media

Abstract

Due to the importance of nanoparticles stability in industrial applications, in this research, stability of laponite nanoparticles dispersions containing different concentrations of sodium sulfonated polyacrylamide (SPA) was investigated in electrolyte media for oil reservoirs applications. In this regard, effect of parameters such as polymer concentration, temperature, and ionic strength were studied via different methods such as Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) and zeta potential. In FT-IR spectra of SPA-laponite dispersion, in addition to typical peaks of laponite, there was a weak peak at 1040cm-1 characterizing SPA polymer. The z-average particle sizes of laponite particles increased after 168 h of aging in presence of SPA polymer. Zeta potential measurements showed that, adsorption of anionic groups of polymer on particle surface during the aging process has led to a decrease in zeta potential value (toward more negative values). It was seen that dispersion stability depended on polymer concentration, ionic strength of aqueous media, and temperature. Visual observations showed that the stability of laponite nanoparticles in electrolyte media was improved by increasing the SPA polymer concentration. The rheological studies showed that the viscosity curves of SPA-laponite dispersions were located below those of the corresponding pure SPA polymer solutions. Consequently, particle settling was hindered by increasing the polymeric matrix viscosity. Furthermore, using a power-law equation fitted to the polymer solution viscosity-shear rate data, it was shown that laponite nanoparticles stability in electrolyte media could be improved by decreasing the power-law coefficient.