What is the difference between shear thinning and thixotropic?

What is the difference between shear thinning and thixotropic?

When describing the viscosity of liquids, however, it is therefore useful to distinguish shear-thinning (pseudoplastic) behaviour from thixotropic behaviour, where the viscosity at all shear rates is decreased for some duration after agitation: both of these effects can often be seen separately in the same liquid.

Is thixotropic shear thinning?

Thixotropy is a time-dependent shear thinning property. A thixotropic fluid is a fluid which takes a finite time to attain equilibrium viscosity when introduced to a steep change in shear rate. Some thixotropic fluids return to a gel state almost instantly, such as ketchup, and are called pseudoplastic fluids.

What is the difference between shear thinning and shear thickening fluids?

A fluid is shear thickening if the viscosity of the fluid increases as the shear rate increases (see Figure 2). Fluids are shear thinning if the viscosity decreases as the shear rate increases. Shear thinning fluids, also known as pseudo-plastics, are ubiquitous in industrial and biological processes.

What is the thixotropic agent?

Thixotropic Agents Thixotropic agents are added to oil-well cement slurries to produce thixotropic properties downhole, which are needed to overcome problems of lost circulation by sealing off lost circulation zones or achieving good annular fill across incompetent zones.

How do you know if shear is thinning?

Shear thinning index can be calculated by dividing apparent viscosity at the lowest speed by the value of apparent viscosity at the highest speed (typically at 2 and 20 or 5 and 50 rpm). The resultant ratio is an index of shear thinning.

Why does shear thinning happen?

Why Does Shear Thinning Occur? Shear thinning occurs because of rearrangements in the fluid microstructure in the plane of the applied shear. It is frequently seen in dispersions such as suspensions and emulsions, including melts and solutions of polymers.

Is shear thinning permanent?

Temporary viscosity loss is where polymers in the fluid are stretched which cause thinning. However, this thinning is reversible once the shear stress is removed. Permanent viscosity loss is not reversible as shearing the fluid causes breakdown of the polymer by rupturing the macromolecular chains.

What is shear-thickening example?

Corn starch and water (oobleck) Cornstarch is a common thickening agent used in cooking. It is also a very good example of a shear-thickening system. When a force is applied to a 1:1.25 mixture of water and cornstarch, the mixture acts as a solid and resists the force.

Is milk a thixotropic fluid?

Human milk showed non-Newtonian, shear-thinning, thixotropic behavior with both yield and flow stresses. Storage and aging increased milk density and decreased viscosity.

Is ketchup thixotropic?

When a ketchup container is turned upside down, the ketchup does not readily come out unless shaken or squeezed. Ketchup is a thixotropic fluid which is classified as a non-Newtonian fluid which has property of becoming a liquid like state when force is applied and returns to gel like state without force.

How does shear thinning occur?

Shear thinning occurs because of rearrangements in the fluid microstructure in the plane of the applied shear. It is frequently seen in dispersions such as suspensions and emulsions, including melts and solutions of polymers.

Is shear thinning reversible?

In the majority of the liquids shear-thinning behavior is completely reversible, with the liquid returning to its ‘normal’ viscosity once the force is removed. Shear thinning materials can be thixotropic whereas thixotropic materials are always shear thinning.