Rheological Aspects of Aqueous Smectite Suspensions
Abstract
Viscosity and flow behavior of smectite suspensions are of paramount importance for the use of this clay mineral in drilling fluids, paper coaters, detergents, paint, cosmetics, pharmaceuticals, and other industrial products. Rheology of colloidal suspensions has been a subject of numerous studies during the last two decades. Comprehensive reviews of these studies are presented by Sherman (1970), Mewis (1980), Goodwin (1982), Ottewill (1982), Krieger (1985), Tadros (1987), and Barnes et al. (1989). Rheological properties of water-based drilling fluids containing smectites (bentonites) as the main viscosifier are described by Gray et al. (1980) and Chilingarian and Vorabutr (1981).
Aqueous smectite suspensions contain colloidal smectite particles as the solid phase and water as the continuous phase. The viscosity and flow behavior of smectite suspensions are sensitive to many factors. A review of these factors is presented in th is chapter inclUding the effects of particle characteristics and interparticle forces on suspension rheology.
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Contents
Clay-Water Interface and its Rheological Implications

Rheology is the science of the flow of fluids and deformation of solids. Of special interest to the clay scientist are the flow behavior and stability of clay suspensions, and the time-dependent deformation of clays in a solid or semi-solid state. The physical state of a clay may change with increasing water content; from a solid, to a semi-rigid plastic, then to a gel, and finally to a suspension. In each state, the main factors determining the rheological behavior of the system are related to: (a) the molecular configuration and dynamics of the clay-water interface, and (b) the nature of the particle interactions at this interface. The hydration of the ions and the clay surfaces plays a special role in clay rheology because flow and deformation directly involve molecular movements along the clay-water interface.