A pseudoplastic material is one in which viscosity decreases with increasing rate of shear (also termed shear thinning). This property is found in certain complex solutions, such as ketchup, whipped cream, blood, paint, and nail polish. Pseudoplasticity can be demonstrated by the manner in which shaking a bottle of ketchup causes the contents to undergo an unpredictable change in viscosity. The force causes it to go from being thick like honey to flowing like water.
It is important to note the distinction between a shear thinning fluid and a thixotropic fluid. The former displays decreasing viscosity with increasing shear rate, while the latter displays a decrease in viscosity over time at a constant shear rate.
A shear thinning fluid is an example of a smart material, a class of materials that can respond to changes in the environment.
