Which of the following represents the rheological behaviour of dilatant liquids?
Newtonian viscosity: An “ideal” fluid produces shear stress proportional to the strain rate. That is, the greater the force applied, the faster the fluid flows and the plot is a straight line.
Pseudoplastic viscosity: The viscosity of many dental materials decreases with increasing strain rate until it reaches a nearly constant value. 
That is, the faster they are stirred, forced through a syringe, or squeezed, the less viscous and more fluid they become.
Liquids that show the opposite behavior are dilatant and become more rigid as the rate of deformation (shear strain rate) increases. That is, the faster they are stirred, the more viscous and resistant to flow they become.
Finally, some classes of materials behave like a rigid body until some minimum value of shear stress is reached. This is represented by the offset along the shear-stress axis. These fluids, which exhibit rigid behaviour initially and then attain constant viscosity, are referred to as plastic.
The viscosity of most fluids decreases rapidly with increasing temperature. Viscosity may also depend on the previous deformation of the liquid. Such fluids become less viscous and more flowable upon repeated applications of pressure and are termed thixotropic.
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