The key difference between thixotropic and pseudoplastic is that the viscosity of thixotropic fluids decreases upon applying a force whereas the viscosity of pseudoplastic fluids increases upon applying a force.
Fluids are liquid or gaseous substances that have a viscosity. We can divide fluids into two types based on the viscosity as thixotropic and rheopectic fluids. Both these are non-Newtonian fluids. In addition to that, there are two other forms of fluids as Bingham and pseudoplastic fluids, based on the properties. However, this article mainly focuses on the difference between thixotropic and pseudoplastic fluids.
CONTENTS
1. Overview and Key Difference
2. What is Thixotropic
3. What is Pseudoplastic
4. Side by Side Comparison – Thixotropic vs Pseudoplastic in Tabular Form
5. Summary
What is Thixotropic?
Thixotropic fluids are liquids or gases whose viscosity decreases upon applying stress over a known time period. Therefore, it can be defined as a time-dependent pseudoplastic behaviour. In contrast, the behaviour of rheopectic fluids can be described as a time-dependent dilatant behaviour. Furthermore, thixotropic fluids show a non-linear stress-strain behaviour as well. Therefore, longer the fluid goes under shear stress, lower the viscosity of the fluid becomes. In other words, these fluids take time to get its viscosity equilibrium when a change in shear rate is introduced.
Some common examples of thixotropic fluids include cytoplasm of cells, synovial fluid, some varieties of honey, some types of clay, solder pastes in electronics, thread-locking fluids, gelatin, xanthan gum, etc.
What is Pseudoplastic?
Pseduoplastic fluids are liquids or gases whose viscosity increase upon application of a force. The opposite type of fluid for pseudoplastic is Bingham fluid. It is a time-dependent fluid because the shear stress applied to the fluid during a particular amount of time is taken to determine the change in viscosity.
Figure 01: Ketchup is an Example of a Pseudoplastic Fluid
A common example of a pseudoplastic substance is a suspension of cornstarch in water. Here, the concentration of cornstarch has to be equal to the concentration of water. When no force is applied, this suspension behaves similar to water. But, when shear stress is applied on the fluid, it solidifies. Other common examples include paint and ketchup.
What is the Difference Between Thixotropic and Pseudoplastic?
Thixotropic and pseudoplastic are two types of fluids that can be categorized according to the behaviour of the fluid upon application of a force. The key difference between thixotropic and pseudoplastic is that the viscosity of thixotropic fluids decreases upon applying a force, whereas the viscosity of pseudoplastic fluids increases upon applying a force.
Some common examples of thixotropic fluids include cytoplasm of cells, synovial fluid, some varieties of honey, some types of clay, solder pastes in electronics, thread-locking fluids, gelatin, xanthan gum, etc. Some common examples of pseudoplastic fluids include ketchup, paint, cornstarch in water suspension, etc. The behaviour of thixotropic fluids is described as time-dependent pseudoplastic behaviour.
The following table summarizes the difference between thixotropic and pseudoplastic fluids.
Summary – Thixotropic vs Pseudoplastic
In brief, thixotropic and pseudoplastic are two types of fluids that can be categorized according to the behaviour of the fluid upon application of a force. The key difference between thixotropic and pseudoplastic is that the viscosity of thixotropic fluids decreases upon applying a force, whereas the viscosity of pseudoplastic fluids increases upon applying a force.
Reference:
1. Kelly, David. “Non-Newtonian Fluids.” FluidFlow, 19 Feb. 2019, Available here.
2. “Pseudoplastic Fluid.” Pseudoplastic fluid – an Overview | ScienceDirect Topics, Available here.
3. “Thixotropy.” Wikipedia, Wikimedia Foundation, 27 Mar. 2020, Available here.
Image Courtesy:
1. “Heinz USDA Organic Tomato Ketchup” By Tt341 – Own work (CC BY-SA 4.0) via Commons Wikimedia