VISCOSITY EQUATION FOR CONCENTRATED SUSPENSIONS OF CHARGED COLLOIDAL PARTICLES

Concentrated suspensions of charged stabilized colloidal particles exh ibit very large viscosity at low shear rate, a strong shear-thinning b ehavior at intermediate shear rate, and a constant second Newtonian vi scosity at high shear rate. This type of non-Newtonian behavior is aff ected by many factors such as the particle volume fraction phi, the pa rticle diameter, the surface electric potential psi(0), salt concentra tion, etc. The generalized equation for the viscosity eta of this syst em is proposed by applying Eyring's transition state theory. The surfa ce electric potential psi(0) and the thickness of the electric double layer k(-1) are determined by applying the theory to experimental data . Systematic experiments of eta of the model colloidal dispersion syst ems are carried out as the function of phi and shear rate and the resu lts are satisfactorily reproduced by the present theory. The effects o f hydrodynamic diameter d(h) and psi(0) of the colloidal particle on e ta are also quantitatively explained. (C) 1997 The Society of Rheology .