Viscosity units

Viscosity measurements are expressed in either systematic or empirical units both are used, but the current trend is very much toward using systematic units. 

Source D. Godfrey and R. L. Peeler, Explanation of SI Viscosity Units, Lubrication Engineering 38 613-614 (1982). With permission. 

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A number of arbitrary viscosity units have also been used. The most common has been the Saybolt Universal second (SUs) which is simply the time in seconds required for 60 mL of oil to empty out of the cup in a Saybolt viscometer through a carefully specified opening. Detailed conversion tables appear in ASTM D2161, approximation of kinematic viscosity V in mm /s(= cSt) can be made from the relation shown in equation 8 ... 

No thermostat viscosity unit = s, unless otherwise noted. 

For higher molecular weight polydimethyl siloxanes (Af > 2500), the number-average molecular weight is related to the bulk viscosity by the foUowiag formula, where the viscosity units are mm /s(=cSt). 

Another viscosity unit is the kinematic viscosity u. This is the ratio of viscosity to density. Common units used for this are the stoke (1 cm- s" ) and the centistoke (1 mm s ). 

The unit of absolute viscosity is the Poise (P, g cm s or mPa s), while the unit for Idnematic viscosity is the Stoke (St, cm s Because of the large size of these viscosity units, absolute viscosities for ionic liquids are usually reported in centipoises (cP) and Idnematic viscosities reported in centistokes (cSt). 

In addition, the U.S. Pharmacopoeia includes the explanation of kinematic viscosity [units in stoke (s) and centistoke (cs)], defined as the absolute viscosity divided by the density of the liquid at a definite temperature, p ... 

In the SI system, the theoretical unit of v is m2/s or the commonly used Stoke (St) where 1 St = 0.0001 m2/s = 100 cSt = 100 centiStoke. Similarly, 1 centiStoke = 1 cSt = 0.000001 m2/s = 0.01 Stoke = 0.01 st. The specific gravity of water at 20.2°C (68.4°F) is almost 1. The kinematic viscosity of water at 20.2°C (68.4°F) is for all practical purposes equal to 1 cSt. For a liquid, the kinematic viscosity will decrease with higher temperature. For a gas, the kinematic viscosity will increase with higher temperature. Another commonly used kinematic viscosity unit is Saybolt universal seconds (SUS), which is the efflux time required for 60 mL of petroleum product to flow through the calibrated orifice of a Saybolt universal viscometer, as described by ASTM-D88. Therefore, the relationship between dynamic viscosity and kinematic viscosity can be expressed as... 

SISO cup constants are from ISO International Standard 2431. k Thermostatted, viscosity units = s/60 mL. 

Water viscosity is a measure of the resistance to flow exerted by water. Units of centipoise are used most often by petroleum engineers. The definitions of other viscosity units are given in Chapter 6 in connection with gas viscosity. 

Since the apparent viscosity of a non-Newtonian fluid holds only for the shear rate (as weii as temperature) at which it is determined, the Brookfield viscometer provides a known rate of shear by means of a spindle of specified configuration that rotates at a known constant speed in the fluid. The torque imposed by fluid friction can be converted to absolute viscosity units (centipoises) by a multiplication factor. See viscosity, shear stress. The viscosities of certain petroleum waxes and wax-polymer blends in the molten state can also be determined by the Brookfield test method ASTM D 2669. 

In the older literature you will find the viscosity unit of poise, defined to be ... 

The first of these properties is viscosity. All principal companies use mainly one of two viscosity units, centipoise (cP) or centistokes (cSt). Centipoise is the more popular. If your database presents only one, say cP, then you may quickly convert it to the other, cSt, by a simple equation ... 

COMOSS collated monolithic support stmcture cP centipoise (a viscosity unit)... 

The measurements of the resistance of a fluid to flow. The higher the viscosity, the more resistance to flow. A "heavy" oil has more resistance to flow than a "light oil. Normally measured at 40°C and 100°C for Saybolt Universal and for other classifications dynamic viscosity (units poise or centipoise) kinematic viscosity (stoke or centistoke). 

There are also a number of specialty viscosity tests that employ their own relative units. These tests have been developed for specific industries such as paints and coatings. Generally, these viscosity units can be directly converted to poise. 

Liquid sulfur-dicyclopentadiene (DCP) solutions at 140°C undergo bulk copolymerization where the melt viscosity and surface tension of the solutions increase with time. A general melt viscosity equation rj == tj0 exp(aXH), at constant temperature, has been developed, where tj is the viscosity at time t for an S -DCP feed composition of DCP mole fraction X and rj0 (in viscosity units), a (in time 1), and b (a dimensionless number, -f- ve for X < 0.5 and —ve for X > 0.5) are empirical constants. The structure of the sul-furated products has been analyzed by NMR. Sulfur non-crystallizable copolymeric compositions have been obtained as shown by thermal analysis (DSC). Dodecyl polysulfide is a viscosity suppressor and a plasticizer for the S8-DCP system. 

Viscosity Units of poise (=0.1 Pascal sec). Viscosity affects how easily the slurry flows. The more viscous a material, the more it resists flow. High slurry viscosity results in poor transport of reactants and products to and from the wafer surface. Viscosity also affects slurry transport across the wafer and lubrication of the wafer-pad interface. 

The units for K will depend on the units prescribed for the other terms. Thus, in the English system of units, if the pressure change is in psf (pounds per square foot), the distance is in feet, and the viscosity value is in Bvu s (British viscosity units of pounds/ft-sec), with the velocity in ft/sec, then the dimensions of K will be ft /sec. (It may be noted that the viscosity in poises has the dimensions of grams/cm-sec, and the viscosity in centipoises has the dimensions of centigrams/cm-sec. Accordingly, to convert a viscosity value in centipoises, multiply the value by 6.72 x 10 to yield the viscosity value in Bvu s.)... 

The flow of liquids or semisolids is described by viscosity, or, more precisely, by shear viscosity (unit Pa sec). The viscosity defines the resistance of the material against flow. Viscosity is not a coefficient, because it is a function of the shear strain rate y [ti = /(y)]. In the classical fluid mechanics, the dynamic viscosity is obtained using a viscometer. (A viscometer is a rheometer, i.e., an instrument for the measurement of rheological properties, limited to... 

The activity of byaluronidase is determined by measuring the reduction in tuihidiiy of a sub.slraie of native byaluroni-date and certain proteins or by measuring tbe reduction in viscosity of a buffered solution of sodium or potassium by-aluronirlate. Each manufacturer defines its product in turbidity or viscosity units, but values ate not tbe same because they measure different properties of tbe enzyme. 

In the preceding equation, the subscript j represents the phase j j = w, o, t for water phase, oil phase, and total relative mobility, respectively. The unit of relative mobihty is the inverse of the viscosity unit, for example, (mPa s) or (cP). An example of water and oil relative permeability curves is shown in Figure 4.1. The corresponding water, oil, and total relative mobihties are shown in Figure 4.2, with the water and oil viscosities being 1 and 10 mPa s, respectively. Figure 4.2 also shows the minimum total relative mobility, the water mobility, oil mobility, and total mobility at a given saturation. The total mobility is the sum of water and oil mobihties. 

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