Rheopectic fluids, properties

Rheopectic fluids. These fluids are quite rare in occurrence and exhibit a reversible increase in shear stress with time at a constant rate of shear. Examples are bentonite clay suspensions, certain sols, and gypsum suspensions. In design procedures for thixotropic and rheopectic fluids for steady flow in pipes, the limiting flow-property values at a constant rate of shear are sometimes used (S2, W3). 

Time-Dependent Fluid Properties. This category includes thixotropic and rheopectic fluids. When a shear stress is applied to a thixotropic fluid, the viscosity decreases gradually, and when the stress is removed, a gradual recovery is observed. The opposite behavior is observed with rheopectic fluids a gradual increase of viscosity during shear followed by recovery on the removal of shear-inducing stress. 

Although there are materials which possess rheological properties that depend on the duration of shear (e.g., in thixotropic fluids the dynamic viscosity decreases, and in rheopectic fluids the dynamic viscosity increases with the time for which shearing forces are appli ), we will consider only those materials which do not change their properties with time. 

Rheopectic (antithixotropic) fluids are shear-thickening fluids whose r a increases with time under constant or low y. Rheopexy is a property of linear... 

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