Rheology - Rheological Properties, Rheometers and The Deborah Number

Background

Rheology is the study of the flow and deformation of matter and materials, under the application of a stress or strain. While it includes the well characterised systems such as water and other liquids that behave as Newtonian liquids, it also encompasses all non-solid materials. Examples of materials that rheological properties are important in include, slurries, paints, powders, molten polymers, suspensions, emulsions, blood etc.

Rheometers

Rheometers are the devices used to measure the rheology of a material. They are similar to, but more complex than viscometers as they need to be able to deal with applied stresses or strains. They are capable of measuring properties such as yield stress, kinetic properties, complex viscosity, modulus, creep, and recovery.

There are three types of rheometers:

1. Rotational rheometers
2. Capillary rheometers
3. Extensional rheometers

The Deborah Number

The Deborah number is applied to materials that exhibit a transition from elastic to viscous. It is a dimensionless property that indicates how fluid a material is. It is the ratio of the relaxation time to the experiment time or observation time. Materials with high Deborah numbers are typical for materials that behave elastically, while lower Deborah numbers are attributed to

Primary author: AZoM.com