Rheology of non-Newtonian fluids: A new flow equation for pseudoplastic systems

On the assumption that pseudoplastic flow is associated with the formation and rupture of structural linkages a new flow equation is derived. The equation takes the form ƞ = ƞ∞ + ƞ0 − ƞ∞1 + αD23, where D = rate of shear, η0 = limiting viscosity at zero rate of shear, η∞ = limiting viscosity at infinite rate of shear, and α is a constant associated with the rupture of linkages. Graphical methods for evaluating the three constants η0 , η∞ , and α are presented. Experimental data are presented on a wide range of pseudoplastic systems, ranging from suspensions to optically clear solutions, in both aqueous and nonaqueous media. In all cases the results conform to the equation with a high degree of accuracy over a wide range of shear rates.