Aa. Zaman et Bm. Moudgil, RHEOLOGY OF BIDISPERSE AQUEOUS SILICA SUSPENSIONS - A NEW SCALING METHOD FOR THE BIDISPERSE VISCOSITY, Journal of rheology, 42(1), 1998, pp. 21-39
The shear viscosity of electrostatically stabilized bidisperse aqueous
silica suspensions has been studied as a function of shear rate, part
icle size, total volume fraction of the particles, and volume ratio of
small to large particles. The higher limiting relative viscosity (at
1000 s(-1)) of monodisperse suspensions of 0.6, 0.85, and 1.5 mu m sil
ica particles was found to be particle size dependent indicating devia
tion from hard sphere behavior. It is shown that the flow properties o
f bidisperse suspensions of colloidal size particles is not only affec
ted by the volume (weight) ratio of the two sizes, but the absolute si
ze of the particles and the particle size ratio also play an important
role in determining the viscosity of the suspension. Binary mixtures
of particles of smaller size ratios show higher viscosities than the s
uspensions containing larger size ratio particles. This indicates that
the viscosity response of suspensions of colloidal size particles is
controlled by both hydrodynamic interactions and colloidal forces. The
Farris [Trans. Sec. Rheol. 12, 281 (1968)] model was found to be inad
equate when applied to bidisperse suspension of colloidal size particl
es. An empirical method is suggested to estimate the viscosity of a bi
modal suspension at a given volume fraction of the particles, from the
viscosity of monodisperse systems and the viscosity of a bimodal susp
ension (at a fixed total volume fraction) as a function of the volume
ratio of the two particles. (C) 1998 The Society of Rheology.