![]() One of the key predictions of the theory is the following relationship between viscosity μ For this reason, measured viscosities of the noble gases serve as important tests of the kinetic-molecular theory of transport processes in gases (see Chapman–Enskog theory). The simple structure of noble gas molecules makes them amenable to accurate theoretical treatment. By contrast, pressure is omitted since gaseous viscosity depends only weakly on it. The temperatures corresponding to each data point are stated explicitly. Where data points are unavailable for 25 ☌ or 1 atmosphere, values are given at a nearby temperature/pressure. Here "standard conditions" refers to temperatures of 25 ☌ and pressures of 1 atmosphere. Viscosities at or near standard conditions Consequently, its kinematic viscosity is around 2 to 40 centiStokes. The density is usually on the order of 0.5 to 5 kg/m^3. Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes.įor gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to 0.02 centiPoise. The density is usually on the order of 1000 kg/m^3, i.e. In engineering, the unit is usually Stoke or centiStoke, with 1 Stoke = 0.0001 m^2/s, and 1 centiStoke = 0.01 Stoke.įor liquid, the dynamic viscosity is usually in the range of 0.001 to 1 Pascal-second, or 1 to 1000 centiPoise. ![]() In engineering, the unit is usually Poise or centiPoise, with 1 Poise = 0.1 Pascal-second, and 1 centiPoise = 0.01 Poise.įor kinematic viscosity, the SI unit is m^2/s. This page lists only dynamic viscosity.įor dynamic viscosity, the SI unit is Pascal-second. Kinematic viscosity is dynamic viscosity divided by fluid density. The values listed in this article are representative estimates only, as they do not account for measurement uncertainties, variability in material definitions, or non-Newtonian behavior. Of all fluids, gases have the lowest viscosities, and thick liquids have the highest. Viscosity is measured using a viscometer. For instance, honey hasĪ much higher viscosity than water. It corresponds roughly to the intuitive notion of a fluid's 'thickness'. At EAG Laboratories, many of our viscometers offer select or programmed temperature control, which affords viscosity testing at constant specified temperatures.Dynamic viscosity is a material property which describes the resistance of a fluid to shearing flows. The more elevated the temperature, the more readily the material flows, which results in a lower measured viscosity compared to ambient or sub-ambient conditions. With all viscosity techniques, temperature can greatly impact the results of testing. Common test methods for kinematic viscosity include ASTM D4212, ASTM D1200 and ASTM D445. Intrinsic viscosity is normally performed using the Ubbelohde viscometer.ĭepending on the equipment used, kinematic viscosity can be reported in units of meters squared per second, stokes, centistokes or time in seconds. Intrinsic viscosity is an important technique for characterizing polymers in dilute solution, because it provides information related to molecular weight and the conformational shape of a specific polymer in a chosen solvent. Therefore, the typical applications for capillary viscometers include: dilute polymer solutions, certain types of solvents, dilute solutions, syrups and oils. The capillary geometry is too small for highly viscous samples. The Ubbelohde and Cannon-Fenske viscometers utilize a glass capillary through which the fluid flows under gravity. The cup-type viscometers are typically used for paints, inks, varnishes and highly viscous coatings. Common ASTM test methods for dynamic viscosity include ASTM D4287, ASTM D562 and ASTM D2196.ĮAG Laboratories performs kinematic viscosity measurements using the following viscometers: Depending on the equipment used, viscosity data can be reported in units of centipoise, poise, Pascal-seconds or Krebs units. The instruments contain a calibrated spring that measures the fluid’s resistance to the movement. Rotational viscometers of various torque ranges manufactured by Brookfield Engineering Corp.įor all of these instrument types, a cone, spindle or paddle is placed in contact with the test fluid and is rotated at a programmed shear rate.Krebs spindle viscometer (KU meter) for paints, pigmented coatings, pastes and adhesives.High shear rate viscometer for paints and pigmented coatings, also known as an ICI viscometer.
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