Viscosity & Rheology

Our Capabilities

Equipped with a TA Instruments Rheometer and a Brookfield Viscometer Dynalene is ready to analyze viscosity, yield stress, shear rates and other properties of various Newtonian and Non-Newtonian fluids and soft solids. We also have Cannon Fenske Viscometers to measure the kinematic viscosity of Newtonian liquids according to ASTM D445 and ISO 3104.

Discussion

Viscosity is defined as the internal friction of a fluid which makes it resistant to flow. This resistance to flow is caused by molecular attraction. Viscosity is an important characteristic to understand because it provides valuable information on how your material will perform. Determining the viscosity of your material can be important for something as simple as the thickness of your shampoo. This knowledge will allow you to have the assurance that your product is consistent from lot to lot and conforms to customers expectations. For complex engineering systems, understanding the viscosity of a product is vital for much more involved reasons, as in determining what type of pumps are needed, the piping system required and how the material may change at different temperatures and shear rates.

Newtonian Fluids

A Newtonian fluid is defined as a fluid whose viscosity remains constant regardless of the shear rate. Common examples of these are water, alcohols, and glycerol.

Non-Newtonian Fluids

A Non-Newtonian fluid is defined as a fluid whose viscosity changes when then shear rate (force) upon it changes. Most often the viscosity of a material will decrease as the shear increases. This is called shear thinning. Examples of these fluids are whipped cream, ketchup and syrups. Conversely shear thickening (Dilatant) materials increase viscosity with the increase of shear. This usually occurs in suspensions and not pure materials. Corn starch in water is a common example.

There are also Non-Newtonian Fluids that are time dependent. A Thixotropic fluid will have its viscosity decrease over time. Common examples would be yogurt and peanut butter. Conversely Rheopectic fluids viscosity increase over time. Printer ink for example.