The rheological properties of Polyacrylamide (PAA) solution are extremely important to know if one is designing a system that will extrude the polymer into various shapes. The present study is to determine the rheological behaviour of PAA aqueous solutions at different concentrations ( ) by using Brookfield DV-II rheometer. Various rheological models are reviewed for a better understanding of their applicability to the PAA solution in determining the viscosity. The models that have been investigated are Jeffrey's model, Oldroyd 8-constant model and Giesekus model. The aforementioned models are the most powerful for predicting the rheological behaviour of viscoelastic fluids. For each model, the parameters which yield the best fit with experimental data are determined. Results showed that, Giesekus model provide the best prediction of viscosity as a function of shear rate and the effects of concentration can be adequately described by an exponential function. For adequate prediction of non-Newtonian viscosity as a function of both shear rate and concentration, simple correlations were proposed. Comparing the results with experimental data revealed that the proposed correlations are in good agreement with apparent viscosities. |
