ASTM D5478-98(2003)
(Test Method)Standard Test Methods for Viscosity of Materials by a Falling Needle Viscometer
Standard Test Methods for Viscosity of Materials by a Falling Needle Viscometer
SIGNIFICANCE AND USE
These test methods are applicable for measuring the rheological properties of varnishes and paints. In particular, the low to moderate shear rate measurements provide information related to sag resistance, leveling, etc.
SCOPE
1.1 These test methods cover the measurement of the viscosity of Newtonian and non-Newtonian liquids. These test methods are applicable to liquids having viscosities in the range from 5 × 10-4 to 103 Pas (0.5 to 106 cP). The shear rate range is dependent upon the needle used and viscosity of the liquid and may vary from 10-4 to 103s-1.
1.2 The yield stress of liquids having this property may also be determined.
1.3 These test methods consist of determining liquid viscosities of Newtonian and non-Newtonian fluids (clear or opaque) by measuring the steady-state (constant) or terminal velocities of cylindrical needles as they fall through the test liquid under the influence of gravity. Yield stresses of non-Newtonian liquids may be measured using the same procedure.
1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: D 5478 – 98 (Reapproved 2003)
Standard Test Methods for
Viscosity of Materials by a Falling Needle Viscometer
This standard is issued under the fixed designation D5478; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1 dilatant fluid (or shear thickening fluid)—one in
which the apparent viscosity increases with increasing shear
1.1 These test methods cover the measurement of the
rate.
viscosity of Newtonian and non-Newtonian liquids. These test
3.1.2 Newtonian and non-Newtonian fluids—A Newtonian
methods are applicable to liquids having viscosities in the
−4 3 6
fluid is one in which the dynamic viscosity does not vary with
rangefrom5 310 to10 Pa·s(0.5to10 cP).Theshearrate
shear rate but only with the temperature and pressure. A
range is dependent upon the needle used and viscosity of the
−4 3 −1
non-Newtonian fluid is one in which the dynamic viscosity
liquid and may vary from 10 to 10 s .
varies with shear rate over at least some shear rate range.
1.2 Theyieldstressofliquidshavingthispropertymayalso
3.1.2.1 Discussion—This viscosity is sometimes referred to
be determined.
as the “apparent viscosity” since it is not a true property of the
1.3 These test methods consist of determining liquid vis-
fluid but a variable depending on the shear rate. The viscosity
cosities of Newtonian and non-Newtonian fluids (clear or
of most non-Newtonian fluids fits a power law expression. A
opaque) by measuring the steady-state (constant) or terminal
power law fluid is defined by the following equation:
velocities of cylindrical needles as they fall through the test
n21
liquid under the influence of gravity. Yield stresses of non-
h 5 K~g˙! (1)
a
Newtonianliquidsmaybemeasuredusingthesameprocedure.
1.4 The values stated in SI units are to be regarded as the
where:
standard. The values given in parentheses are for information
h = apparent viscosity, dyne · s/cm =P=100 cP,
a
only.
n 2
K = fluid consistency, dyne·s /cm ,
1.5 This standard does not purport to address all of the
g˙ = shear rate, 1/s, and
safety concerns, if any, associated with its use. It is the
n = flow index, dimensionless.
responsibility of the user of this standard to establish appro-
3.1.3 pseudoplastic fluid (or shear thinning fluid)—one in
priate safety and health practices and determine the applica-
which the apparent viscosity decreases with increasing shear
bility of regulatory limitations prior to use.
rate.
3.1.4 viscosity—Theratiobetweenanappliedshearstressto
2. Referenced Documents
the resulting shear rate (velocity gradient) is defined as the
2.1 ASTM Standards:
dynamic viscosity. It is a measure of the resistance to flow of
E1 Specification for ASTM Thermometers
a fluid.
3.1.4.1 Discussion—In the SI unit system the units of
3. Terminology
viscosity are Pa·s. One mPa·s is equal to one centipoise (cP).
3.1 Definitions:
3.1.5 yield stress—Some fluids when subjected to a shear
stress behave as deformable solids until a certain critical shear
stressisreachedafterwhichtheybehaveasfluids.Thiscritical
These test methods are under the jurisdiction of ASTM Committee D01 on
Paint and Related Coatings, Materials, and Applications and are the direct
shear stress is called the yield stress or yield value.
responsibility of Subcommittee D01.24 on Physical Properties of Liquid Paints and
3.1.5.1 Discussion—Examples of such fluids include many
Paint Materials.
paints and pigment pastes and certain food materials, for
Current edition approved Dec. 1, 2003. Published December 2003. Originally
approved in 1993. Last previous edition approved in 1998 as published as example, ketchup.
D5478–98.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4. Summary of Test Methods
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1 Test Method A consists of determining the viscosity of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Newtonian liquids.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5478 – 98 (2003)
, ,
6.1.1 Falling Needle Viscometer —A schematic of the
falling needle viscometer is shown in Fig. 1. The viscometer
consistsofaverticalcylindricaltestsectionofdiameter D.The
liquidspecimenisplacedinthetestsectionandthespecimen’s
temperature is maintained constant by means of a constant
temperature bath that circulates a liquid through another
cylindrical container (water jacket) that is coaxial to the test
section.Athin hollow cylinder of length L with hemispherical
ends and diameter d (the needle) is aligned with the axis of the
test section and allowed to fall under the influence of gravity.
The needle has a small weight in its forward end that may be
varied to change its density. After the needle has attained its
constant terminal velocity, this velocity is measured by deter-
mining the needle transit time between two circumferential
marks a known distance apart on the test section (for opaque
liquids this can be done by an automatic sensing device, such
as a magnetic sensor, etc.). With a knowledge of the terminal
velocity, the liquid and needle densities, the geometric con-
stants of the system (L, D, d), the viscosity of a Newtonian
fluid can be calculated from the instrument theory. For a
non-Newtonian fluid whose viscosity depends upon the shear
rate, a series of needles are dropped. The falling needle is an
absolute method of viscosity measurement that does not need
any instrument calibration. However, it may be checked
through use of known certified viscous fluids such as standard
oils.
6.1.2 Thermometer—A thermometric device calibrated to
0.1°Cwhoseaccuracy,precision,andsensitivityareequaltoor
better than the ASTM thermometer described in Specification
E1.
6.1.3 Circulating Liquid Bath, capable of maintaining the
test specimen temperature to 60.1°C.
6.1.4 Stopwatch or Electronic Device,capableofmeasuring
to 60.01 s or an automatic sensing device with the same
accuracy.
7. Preparation of Specimen
7.1 After opening the specimen container, mix the fluid
FIG. 1 Schematic of Falling Needle Viscometer
gently with a glass rod for 5 min.
7.2 Pourthespecimencarefullyintothetestsectionsoasto
minimizetheformationofairbubbles.Ifavailable,asyringeis
4.2 Test Method B consists of determining the apparent
useful for this purpose.
viscosity and shear rate of pseudoplastic and dilatant fluids in
7.3 Remix the specimen in the test container using the
the power law region.
needle retriever rod by pushing it up and down four times at a
4.3 Test Method C consists of determining the apparent
velocity of approximately 4 cm/s.
viscosity and shear rate of pseudoplastic and dilatant fluids
outside of the power law region.
4.4 Test Method D consists of determining the yield stress
of liquids that have such a property.
Park, N. A., and Irvine, T. F., Jr., “Measurements of Rheological Fluid
Properties with the Falling Needle Viscometer,” Review of Scientific Instruments,
Vol 59, 1988, pp. 2051–2058.
5. Significance and Use
Park, N. A., and Irvine, T. F., Jr., “The Falling Needle Viscometer, A New
5.1 These test methods are applicable for measuring the
Technique for Viscosity Measurements,” American Laboratory, Vol 20, November
1988, pp. 57–63.
rheologicalpropertiesofvarnishesandpaints.Inparticular,the
“The sole source of supply of the falling needle viscometer known to the
low to moderate shear rate measurements provide information
committee at this time is Stony Brook Scientific, Ltd., P.O. Box 147, 914 Filmore
related to sag resistance, leveling, etc.
Rd.,Norristown,PA19403.Ifyouareawareofalternativesuppliers,pleaseprovide
this information toASTM International Headquarters. Your comments will receive
careful consideration at a meeting of the responsible technical committee, which
6. Apparatus
you may attend.” This instrument may be interfaced with a computer for data
6.1 Viscometer, falling-needle-type and associated equip-
collection and analysis. A computer program is available for data analysis for
ment listed as follows: instruments that are not interfaced.
D 5478 – 98 (2003)
7.4 Allow the specimen to remain at rest in the test section 10.1.2 Temperature of the test specimen, °C, and
for a minimum of 5 min or until any air bubbles have risen to 10.1.3 Viscosity of the test specimen, cP (Note 1).
the surface. Longer rest times may be used in the case of yield
NOTE 1—If the same needle is dropped more than once, report the
stress measurements.
minimum, maximum, and average viscosity values. If needles of different
densities are dropped, report the individual viscosity measurements.
TEST METHOD A—NEWTONIAN FLUIDS
VISCOSITY MEASUREMENTS
11. Precision and Bias
11.1 Precision—Inaninterlaboratorystudy,sixoperatorsin
8. Procedure
six laboratories measured (four replicates) viscosities of three
8.1 Level the viscometer so that the central vertical axis of
Newtonian oils and one essentially Newtonian spar varnish.
the test section is parallel to the gravity vector by using either
Thesematerialscoveredaviscosityrangeof100to1440mPa.s
a bubble level or a plumb bob.
(cP). The within-laboratory coefficient of variation was found
8.2 Circulate the liquid from the constant temperature bath
tobe2.70or0.5%oftheaverageviscosity.Thecorresponding
until the test specimen temperature is constant at the specified
between-laboratories coefficient was 4.58 or 0.9% of the
value with a variation of 60.1°C.
average viscosity. Based on these coefficients, the following
8.3 To determine the viscosity, drop a needle along the
criteria should be used for judging the acceptability of results
central axis of the test section and measure its velocity by the
at the 95% confidence level:
amountoftimetakentomovebetweentwoofthemeasurement
11.1.1 Repeatability—Two results of individual viscosity
lines. This may be done by using a stopwatch or an automatic
measurements obtained by the same operator at different times
sensing device.The measurement lines should be at least a test
should be considered suspect if they differ by more than 1.4%
section diameter from the top and bottom of the liquid.
relative.
8.4 Record the values of the needle velocity, the liquid
...
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