Experimental Study of Rheological Properties of Water-Carbopol Microgel

In this article, microgel rheological properties has been studied at different Carbopol 940 concentrations in water using the rotational and capillary rheometer. The results obtained at shear rates less than 1000 1/s showed that the gels follow the Herschel-Bulkley rheological model. Investigation of the rheological properties’ temperature variation indicated the stability of the gels up to 50 °C. The effect of time on the rheological properties of the gels showed their appropriate stability in a period of 40 days at 25 °C. With respect to the effectiveness of pH of the medium on the gels’ behavior, the effect of pH was studied by addition of caustic soda and it was indicated that in a neutral medium, the gels have the maximum viscosity. The capillary tube rheometer was used to investigate the fluid behavior at high shear rates (shear rate range of 190000-600000 1/s). The results of the application of oscillatory rheometer showed a nonlinear and weak viscoelastic behavior of this kind of gels up to a Carbopol concentration of 0.5% compared to other viscoelastic fluids such as water-methyl cellulose solutions.