Viscosity is the mechanical friction between moving molecules and the resistance to deformation due to the mutual attraction of the molecules. In other words, it is the resistance to flow.
There are two types of viscosity:
1. Dynamic viscosity , also known as Absolute viscosity , is the tangential force per unit area required to move one horizontal plane relative to another horizontal plane with unit velocity when the fluid maintains a unit distance.
2. Kinematic viscosity is the ratio of dynamic viscosity to density.
Many simple fluids are classified as Newtonian fluids, meaning that their viscosity does not depend on the amount of shear applied. Examples would be water and simple hydrocarbons. When the complexity of the fluid is increased, for example by including bubbles, droplets, particles or polymers, the fluid can have more complex behaviour and exhibit non-Newtonian behaviour, where the viscosity depends on the amount of shear applied. These types of fluids are often referred to as structured fluids or complex fluids.
Such non-Newtonian behavior is common to many industrial and commercial products including toothpaste, mayonnaise, paints, cosmetics, etc., which are generally shear-thinning fluids, in which viscosity decreases with increasing shear rate, although shear-thinning can occur in some very tightly structured fluids.
Measure
Viscosity is measured using a variety of viscometers and rheometers. Close temperature control of the fluid is essential to obtain accurate measurements, especially in materials such as lubricants, whose viscosity can double with a change of only 5°C. Viscometers are used for fluids that cannot be defined by a single viscosity value and therefore require more parameters to be set up and measured than is the case with a viscometer.
For some fluids, the viscosity remains constant over a wide range of shear rates (Newtonian fluids). Fluids that do not have a constant viscosity (non-Newtonian fluids) cannot be described by a single number. Non-Newtonian fluids exhibit a variety of relationships between shear stress and shear rate.
Viscosity standards
Viscosity can be expressed in several different ways:
– Dynamic viscosity (absolute viscosity): unit cp
– Kinematic viscosity: unit cst
– In addition, people also use conventional viscosity. For this type of viscosity, depending on the device used to measure, we have different names and results such as Engler viscosity (oE), Saybolt viscosity (SSU), Redwood viscosity.
Viscosity Applications
Viscosity measurement allows the most sensitive or convenient way to detect changes in color, density, stability, solid content and molecular weight. (in the chemical industry, e.g. in polymerization reactors).
Rion Viscosity Meter – Viscotester VT-06
Coating viscosity is one of the key factors determining the success of the coating process. Because the repeatability and reproducibility of the coating process are often closely related to coating viscosity, this is an important control parameter.
The viscosity of conformal coatings is often temperature sensitive. To accurately measure the viscosity of a conformal coating material, measurements must be made on samples at a stable temperature.
Food viscosity testing is used to find the best ingredient ratios when manufacturing items such as chewing gum, butter, margarine, bread, candy, chocolate and other food items.
For example, chocolate has many flow characteristics related to encapsulation and bulking. In viscosity measurements of chocolate products, flow characteristics are often described using Casson flow curves.
ATAGO VISCO-895 Automatic Viscosity Meter
Viscosity is one of the most important properties of a fluid and plays a prominent role in the oil and gas industry. Crude oil viscosity affects the ability to pump oil out of the ground; fuel viscosity and volatility affect how easily fuel is sprayed in fuel injectors; lubricant viscosity affects how well it protects an engine. It is an important measurement characteristic in the food, paint, polymer coatings and other industries where flow is a critical product or application characteristic.
MALCOM Solder Paste Viscosity Meter PM-2A, PM-2B, PM-2C
Conclude
Measuring viscosity is an effective way to determine the state (property of matter) or fluidity of a liquid or gas.
It plays a vital role in quality control and various stages of research and development in laboratory, process and research environments as well as a wide range of industries and applications including Food, Chemical, Pharmaceutical, Petrochemical, Cosmetic, Paint, Ink, Coating, Oil and Automotive, Electronics..
The choice of viscometer depends on the needs of use. To achieve that goal, please contact us to start making requests and Semiki will advise on suitable solutions. Viscosity meter.
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