Rheometer

November 1, 2021

When it is required to study the relationship between stress and deformation of fluid materials, it is necessary to use a rheometer. This tool is useful to know the viscosity and the normal stress coefficient of substances, therefore it is considered a very useful instrument in physics laboratories and industries in various areas.

Rheology is the science that studies the relationship between the force of a material and the deformation that occurs when it flows. To establish the precision in the measurement, in addition to using a rheometer, it is necessary to perform constitutive equations to model the behavior of these materials.

If you need to determine the speed of a substance and obtain accurate results, I invite you to know what a rheometer is for and what are its main uses.

What is a Rheometer?

The rheometer is a laboratory material used to measure the effort and viscosity with which a liquid flows, or some type of mixture, exposing it to a certain force.

Its mechanical structure makes it possible to determine the fluid of those liquid substances that do not have a single viscosity value defined. These mixtures generally require adjustment and measurement with much tighter parameters than using a viscometer.

The viscometer for its part is a measurement tool that offers data on the ductility and viscosity of substances that have a defined density. It is also useful in process controls and laboratory applications.

What is a Rheometer for?

Rheometers are instruments that serve to measure viscosity, as well as determine the elasticity of all non-Newtonian substances under extensive conditions.

The main properties that a rheometer can measure are:

  • Yield flow
  • Thixotropy
  • Extensional viscosity
  • Yield stress.
  • Behavior during stress relaxation
  • Extrusion swelling
  • Melt fractures

Each of these properties make it possible to determine the stress and deformation of the fluids, in this way it is much easier to know in detail the conditions and viscosity of the substances.

Rheometer Types

Within the market of measuring instruments there are two types of rheometer, whose differences are established by their operation, they are:

The rotational rheometer

It is a versatile device that can be configured in different rheological methods, in order to know the structure and performance of suspensions in some substances . The types of tests are established from the generation of simple viscosity curves, up to decades of torque, by means of stress measurement and precise sequences.

This type of rheometer offers more and more accurate and immediate results, because it is a modern instrument that accounts for the test method of specific processes , to generate and interpret relevant data.

In terms of optimization, rotational rheometers are designed to operate in many decades of torque and in the viscosity of liquids with a weak structure.

Some of the substances that are measured in rotational rheometers are: samples of creams and liquid gels of weak structure.

How do rotational rheometers work?

Rotational rheometers work much like the viscometer. However, rheometers have superior functionality .

To use this equipment, the first thing to do is load the samples between two geometric plates, for example in a cone and plate system alternately and a cup and bob system.

The rheometer by means of the upper plate applies rotational shear stress on the substance, then the missing stress is calculated, this is called “shear rate”.

This tool is accurate and will allow you to identify the condition where shear stress can be applied.

Capillary rheometer

The capillary rheometer has its origins in the polymer industry, its objective is to measure the viscosity profiles of suspensions in substances that have large particles at high loads . For example: ceramic slurries, polymer melts, inks, food and coatings.

The advantage of this type of equipment is that it has a very high force, which allows knowing the behavior of substances at limits much higher than the rotational rheometer.

It is used in industrial processes such as extrusion and spraying of coarse-sized materials.

How does the capillary rheometer work?

For the operation of this mechanical tool, pressure must be exerted at the outlet of a sample , which must be determined by a barrel or depending on a high pressure. Now then, the pressure drop of the barrel will provide the information about the flow pressure velocity of the liquid substance at which you want to calculate the viscosity.

Uses of a Rheometer

The rheometer is the indicated measuring instrument to measure the viscosity of fluids that cannot be read by the viscometer . This tool is responsible for establishing precise parameters to know the properties of liquids.

This mechanical equipment subjects the fluid to different types of deformations, measuring stress, viscosity, normal stress coefficient, storage modulus, loss modulus and nonlinear viscoelasticity.

Rheometers allow knowing the yield point of substances, this element is of great importance because it is essential to guarantee the quality of some products such as: gels, varnishes, lubricants, pastes, ointments, paints, etc.

The food industry also uses this tool to know the flow of some products such as cream creams, desserts, puddings. On the other hand, medicine uses this system to know the flow properties of the blood for the nutrition and oxygen processes of the organs.

Rheometer Features

As you have seen before, there are two types of rheometer according to the type of substance that you want to measure. However, despite their differences, they coincide in some essential characteristics that I will share with you:

  • Analyze the behavior of materials in a state of deformation and fluidity
  • They measure magnitudes such as angle of twist, torque, and period
  • Designed with a wide range of pressure and temperatures
  • Some show digitized results

Its characteristics include elements such as large and small pulleys, fixed and mobile columns, plates, motor, transmission belt, screws, devices to control temperature, force transducers. This set of pieces make up a system that allows the sample to be exposed to deformations and flow velocities to represent industrial processing conditions.

Importance of Rheometers

Rheometers are measuring instruments of great importance in various areas , not only the industrial and physical sectors benefit from this device, but also its operation is necessary for scientific research on health and food.

Achieving a good quality product depends on many factors, including its viscosity. Depending on the type of substance you want to study, you should choose the rheometer that best suits what you need, so you will get accurate results.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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