Hard sphere colloidal dispersions: Viscosity as a function of shear rate and volume fraction

Abstract

The viscosities of suspensions of sterically stabilized (hard) silica spheres in cyclohexane are reported as a function of shear rate (γ̇) and volume fraction (6×10− 4<φ<0.6). The shear thinning scales according to (η r −η∞)/(η0−η∞) =1/(1+1.31ηγ̇a 3/k T) with limiting low and high shear viscosities described up to φ∼0.35 by η0=1+5/2φ+(4±2)φ2+(42±10)φ3 , η∞=1+5/2φ+(4±2)φ2+(25±7)φ3 . At higher volume fractions the viscosity becomes more sensitive to φ and diverges at φ m =0.63±0.02 (γ̇→0) , φ m =0.70±0.02 (γ̇→∞) . The experimental results compare well with existing hard sphere theories and the data of Krieger (1972) for aqueous lattices. Even at the highest volume fraction neither yield stresses nor shear thickening are observed.