and the viscosity from Brownian motion denoted here as the The shear properties of Brownian, rigid spheres consisting of sterielastic-like viscosity, h (e) , cally stabilized, crosslinked polymethylmethacrylate (PMMA) particles were studied in suspension. Three different volume fractions were used to carry out this study. The suspensions' elastic-like and
viscous-like components of the shear stress were measured by a recently developed technique utilizing cessation of steady shear. The elastic-like viscosity component, or the amount of stress retained at h (e) h c รฅ h (e) r ร
0.97f 2 , [1b] the instant of cessation divided by the shear rate, due to Brownian and possible interparticle forces, decreased in magnitude over the entire range of shear rates used (shear thinning). The decay of the where h c is the viscosity of the continuous phase, f, the elastic-like stress with time after cessation of flow was also analysed volume fraction and the subscript ''r'' means ''relative.'' and found to fit a power law relation. The viscous-like component, or the amount of stress lost at the instant of cessation divided by the (NB: See Doi (3) for a good description of elastic-like and shear rate, is related to hydrodynamic interactions between and drag viscous-like components of the viscosity.) The above result on particles and remained essentially constant with shear rate. These for h (e) is valid only in the limit of dominant Brownian data are the first of this kind gathered for a model hard sphere motion. The total viscosity, h, is the sum of the two composystem (i.e., mechanical means) and agrees well with results of Bender nents and simplifies to Einstein's result in the limit of small and Wagner (J. Colloid Interface Sci. 172, 171 (1995) who used an volume fraction. optical technique.