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

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, effects of parameters, such as polymer concentration, temperature, and ionic strength, were studied via different methods such as Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and zeta potential. In FTIR spectra of SPA-laponite dispersion, in addition to typical peaks of laponite, there was a weak peak at 1040 cm-1 characterizing SPA polymer. The z-average particle sizes of laponite particles increased after 168 h of aging in the 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 observed 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. However, dispersion stability decreased with increasing temperature and ionic strength. The rheological studies showed that the viscosity curves of SPA-laponite dispersions were located below those of the corresponding pure SPA polymer solutions. In addition, the samples had their shear viscosities increased by increasing the SPA polymer concentration. Consequently, particle settling was hindered by increasing the polymeric matrix viscosity. Furthermore, it was shown that laponite nanoparticles’ stability in electrolyte media could be improved by decreasing the power-law coefficient using a power-law equation fitted to the polymer solution of viscosity-shear rate data.