Testing shear thinning/thixotropy and shear thickening/antithixotropy relationships in a fumed silica suspension

Motivated by the existence of conflicting results that can be found in the specialized literature, an experimental program was designed strictly following the definitions of thixotropy and antithixotropy provided by the International Union of Pure and Applied Chemistry. To test the validity of the implicitly assumed correspondence between steady state shear thinning and thixotropy, and steady state shear thickening and antithixotropy, a colloidal suspension that shows steady shear thinning and shear thickening behaviors at different shear stress regimes was used. In this way, possible misinterpretations of the results from the different chemical nature or physical properties of the materials were avoided. An apparent viscosity function for shear thinning/shear thickening fluids was used. In addition, kinetic equations for the time dependency of the viscosity were also used to obtain the temperature dependence of the rate constants for the formation and rupture of particle aggregates in both shear regions.