1、Designation: D 5478 98 (Reapproved 2003)Standard Test Methods forViscosity of Materials by a Falling Needle Viscometer1This standard is issued under the fixed designation D 5478; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the measurement of theviscosity of Newtonian and non-Newtonian liquids. These testme
3、thods are applicable to liquids having viscosities in therange from 5 3 104to 103Pas (0.5 to 106cP). The shear raterange is dependent upon the needle used and viscosity of theliquid and may vary from 104to 103s1.1.2 The yield stress of liquids having this property may alsobe determined.1.3 These tes
4、t methods consist of determining liquid vis-cosities of Newtonian and non-Newtonian fluids (clear oropaque) by measuring the steady-state (constant) or terminalvelocities of cylindrical needles as they fall through the testliquid under the influence of gravity. Yield stresses of non-Newtonian liquid
5、s may be measured using the same procedure.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of
6、 the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E1 Specification for ASTM Thermometers3. Terminology3.1 Definitions:3.1.1 dilatant fluid (or shear thick
7、ening fluid)one inwhich the apparent viscosity increases with increasing shearrate.3.1.2 Newtonian and non-Newtonian fluidsA Newtonianfluid is one in which the dynamic viscosity does not vary withshear rate but only with the temperature and pressure. Anon-Newtonian fluid is one in which the dynamic
8、viscosityvaries with shear rate over at least some shear rate range.3.1.2.1 DiscussionThis viscosity is sometimes referred toas the “apparent viscosity” since it is not a true property of thefluid but a variable depending on the shear rate. The viscosityof most non-Newtonian fluids fits a power law
9、expression. Apower law fluid is defined by the following equation:ha5 Kg!n21(1)where:ha= apparent viscosity, dyne s/cm2= P = 100 cP,K = fluid consistency, dynesn/cm2,g = shear rate, 1/s, andn = flow index, dimensionless.3.1.3 pseudoplastic fluid (or shear thinning fluid)one inwhich the apparent visc
10、osity decreases with increasing shearrate.3.1.4 viscosityThe ratio between an applied shear stress tothe resulting shear rate (velocity gradient) is defined as thedynamic viscosity. It is a measure of the resistance to flow ofa fluid.3.1.4.1 DiscussionIn the SI unit system the units ofviscosity are
11、Pas. One mPas is equal to one centipoise (cP).3.1.5 yield stressSome fluids when subjected to a shearstress behave as deformable solids until a certain critical shearstress is reached after which they behave as fluids. This criticalshear stress is called the yield stress or yield value.3.1.5.1 Discu
12、ssionExamples of such fluids include manypaints and pigment pastes and certain food materials, forexample, ketchup.4. Summary of Test Methods4.1 Test Method A consists of determining the viscosity ofNewtonian liquids.4.2 Test Method B consists of determining the apparentviscosity and shear rate of p
13、seudoplastic and dilatant fluids inthe power law region.4.3 Test Method C consists of determining the apparentviscosity and shear rate of pseudoplastic and dilatant fluidsoutside of the power law region.1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings
14、, Materials, and Applications and are the directresponsibility of Subcommittee D01.24 on Physical Properties of Liquid Paints andPaint Materials.Current edition approved Dec. 1, 2003. Published December 2003. Originallyapproved in 1993. Last previous edition approved in 1998 as published asD 5478 98
15、.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
16、 C700, West Conshohocken, PA 19428-2959, United States.4.4 Test Method D consists of determining the yield stressof liquids that have such a property.5. Significance and Use5.1 These test methods are applicable for measuring therheological properties of varnishes and paints. In particular, thelow to
17、 moderate shear rate measurements provide informationrelated to sag resistance, leveling, etc.6. Apparatus6.1 Viscometer, falling-needle-type and associated equip-ment listed as follows:6.1.1 Falling Needle Viscometer3,4,5A schematic of thefalling needle viscometer is shown in Fig. 1. The viscometer
18、consists of a vertical cylindrical test section of diameter D. Theliquid specimen is placed in the test section and the specimenstemperature is maintained constant by means of a constanttemperature bath that circulates a liquid through anothercylindrical container (water jacket) that is coaxial to t
19、he testsection. A thin hollow cylinder of length L with hemisphericalends and diameter d (the needle) is aligned with the axis of thetest section and allowed to fall under the influence of gravity.The needle has a small weight in its forward end that may bevaried to change its density. After the nee
20、dle has attained itsconstant terminal velocity, this velocity is measured by deter-mining the needle transit time between two circumferentialmarks a known distance apart on the test section (for opaqueliquids this can be done by an automatic sensing device, suchas a magnetic sensor, etc.). With a kn
21、owledge of the terminalvelocity, the liquid and needle densities, the geometric con-stants of the system (L, D, d), the viscosity of a Newtonianfluid can be calculated from the instrument theory. For anon-Newtonian fluid whose viscosity depends upon the shearrate, a series of needles are dropped. Th
22、e falling needle is anabsolute method of viscosity measurement that does not needany instrument calibration. However, it may be checkedthrough use of known certified viscous fluids such as standardoils.6.1.2 ThermometerA thermometric device calibrated to0.1C whose accuracy, precision, and sensitivit
23、y are equal to orbetter than the ASTM thermometer described in SpecificationE1.6.1.3 Circulating Liquid Bath, capable of maintaining thetest specimen temperature to 60.1C.6.1.4 Stopwatch or Electronic Device, capable of measuringto 60.01 s or an automatic sensing device with the sameaccuracy.7. Prep
24、aration of Specimen7.1 After opening the specimen container, mix the fluidgently with a glass rod for 5 min.7.2 Pour the specimen carefully into the test section so as tominimize the formation of air bubbles. If available, a syringe isuseful for this purpose.7.3 Remix the specimen in the test contai
25、ner using theneedle retriever rod by pushing it up and down four times at avelocity of approximately 4 cm/s.7.4 Allow the specimen to remain at rest in the test sectionfor a minimum of 5 min or until any air bubbles have risen tothe surface. Longer rest times may be used in the case of yieldstress m
26、easurements.3Park, N. A., and Irvine, T. F., Jr., “Measurements of Rheological FluidProperties with the Falling Needle Viscometer,” Review of Scientific Instruments,Vol 59, 1988, pp. 20512058.4Park, N. A., and Irvine, T. F., Jr., “The Falling Needle Viscometer, A NewTechnique for Viscosity Measureme
27、nts,” American Laboratory, Vol 20, November1988, pp. 5763.5“The sole source of supply of the falling needle viscometer known to thecommittee at this time is Stony Brook Scientific, Ltd., P.O. Box 147, 914 FilmoreRd., Norristown, PA19403. If you are aware of alternative suppliers, please providethis
28、information to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee,1whichyou may attend.” This instrument may be interfaced with a computer for datacollection and analysis. A computer program is available for data analy
29、sis forinstruments that are not interfaced.FIG. 1 Schematic of Falling Needle ViscometerD 5478 98 (2003)2TEST METHOD ANEWTONIAN FLUIDSVISCOSITY MEASUREMENTS8. Procedure8.1 Level the viscometer so that the central vertical axis ofthe test section is parallel to the gravity vector by using eithera bub
30、ble level or a plumb bob.8.2 Circulate the liquid from the constant temperature bathuntil the test specimen temperature is constant at the specifiedvalue with a variation of 60.1C.8.3 To determine the viscosity, drop a needle along thecentral axis of the test section and measure its velocity by thea
31、mount of time taken to move between two of the measurementlines. This may be done by using a stopwatch or an automaticsensing device. The measurement lines should be at least a testsection diameter from the top and bottom of the liquid.8.4 Record the values of the needle velocity, the liquid andneed
32、le densities, the test specimen temperature, the localacceleration of gravity and the test section, and needle dimen-sions D, L, and d.8.5 Drop additional needles of different densities to estab-lish whether the fluid is Newtonian. If the measured viscosityis essentially constant using the different
33、 density needles, thenthe fluid is Newtonian.9. Calculation9.1 Calculate the Newtonian fluid viscosity for any needledrop as follows:h5grs2rl!UtG(2)where:h = dynamic viscosity, P = 100 cP,g = local acceleration of gravity, cm/s2,rs= needle density, g/cm3,rl= test specimen density, g/cm3,Ut= measured
34、 needle terminal velocity, cm/s, andG = geometric constant depending upon the test sectionand needle dimensions D, L, and d that is furnished bythe instrument manufacturer. Table 1 lists severaltypical geometric constants.10. Report10.1 Report the following information:10.1.1 Name of the test specim
35、en,10.1.2 Temperature of the test specimen, C, and10.1.3 Viscosity of the test specimen, cP (Note 1).NOTE 1If the same needle is dropped more than once, report theminimum, maximum, and average viscosity values. If needles of differentdensities are dropped, report the individual viscosity measurement
36、s.11. Precision and Bias11.1 PrecisionIn an interlaboratory study, six operators insix laboratories measured (four replicates) viscosities of threeNewtonian oils and one essentially Newtonian spar varnish.These materials covered a viscosity range of 100 to 1440 mPa.s(cP). The within-laboratory coeff
37、icient of variation was foundto be 2.70 or 0.5 % of the average viscosity. The correspondingbetween-laboratories coefficient was 4.58 or 0.9 % of theaverage viscosity. Based on these coefficients, the followingcriteria should be used for judging the acceptability of resultsat the 95 % confidence lev
38、el:11.1.1 RepeatabilityTwo results of individual viscositymeasurements obtained by the same operator at different timesshould be considered suspect if they differ by more than 1.4 %relative.11.1.2 ReproducibilityTwo results of individual viscositymeasurements obtained by operators in different labor
39、atoriesshould be considered suspect if they differ by more than 2.4 %relative.11.2 BiasBias has not been determined for this testmethod.TEST METHOD BAPPARENT VISCOSITY ANDSHEAR RATE OF PSEUDOPLASTIC AND DILATANTFLUIDS IN POWER LAW REGIONS12. Procedure12.1 Follow the procedures in accordance with 8.1
40、 and 8.2.12.2 Drop a series of needles of the same geometry butdifferent densities along the central axis of the test section andmeasure their velocities by the amount of time taken to travelbetween two of the measurement lines. This may be done byusing a stopwatch or an automatic sensing device. Th
41、e mea-surement lines should be at least a test section diameter fromthe top and bottom of the liquid.12.3 Record the values of the needle velocities, needledensities, the test specimen temperature, the local accelerationof gravity and the test section, and needle dimensions D, L, andd.13. Calculatio
42、n13.1 Plot a graph of Loge(rs rl) versus LogeUt.Ifthepoints form a straight line then the shear rate is in the powerlaw region (see section 13.3) and the slope of the straight lineis the flow index, n.13.2 Calculate the shear rate g from the following equation:Logeg/Ut! 5 A11 B1Logen 1 C1Logen!21 D1
43、Logen!31 E1Logen!41 F1Logen!5(3)where the values of A1, B1, C1, D1, E1, and F1are given inTable 2 for the same representative systems and needles as inTable 1.13.3 Calculate the apparent viscosity from the followingequation:LogeFhaUtgrs2rl!G5 A21 B2Logen 1 C2Logen!2(4)TABLE 1 Geometric Constants (G)
44、 for Several SystemDiametersA(D) and Needle Lengths (L)System Diameter,cmNeedle Length,cmG, 1/cm2Viscosity Range,cP1.905 10.2 80.89 501060.8044 4.2 529.8 101040.4996 4.2 12,816 0.520ANeedle diameter = 0.3980 cm.D 5478 98 (2003)31 D2 Logen!31 E2Logen!41 F2Logen!5(5)where the values of A2, B2, C2, D2,
45、 E2, and F2are given inTable 2 for the same representative systems and needles as inTable 1.14. Report14.1 Report the following information:14.1.1 Name of the test specimen,14.1.2 Temperature of the test specimen during the needledrops, C,14.1.3 Graph of Loge(rs rl) versus LogeUtand the valueof nas
46、determined by the slope,14.1.4 Calculated values of haand g, cP, and 1/s respec-tively in accordance with 13.2 and 13.3, and14.1.5 Flow curve (graph) of apparent viscosity haversus gin Log-Log coordinates including the temperature and testspecimen information.15. Precision and Bias15.1 PrecisionIn a
47、n interlaboratory study, six operators insix laboratories measured (four replicates) viscosities of fourmaterials comprising a spar varnish, a rust inhibitive primer, alatex semigloss, and an alkyd gloss enamel, that covered areasonable range of viscosities. The varnish was very slightlydilatant (sh
48、ear thickening) and the paints all were shearthinning. Measurements were taken with at least three needlesin each case and as many as six (equivalent to six operatorstesting 18 paints). Because Test Method B does not requiresingle point viscosities, but rather viscosity-shear rate curves,and slight
49、differences in specified needles give different shearrates and, therefore, viscosities, it was decided not to try todetermine precision on the basis of individual viscosities. Wewere not comfortable with trying to determine the precision ofcurves either, so we decided to normalize the values obtainedby multiplying the viscosities by the shear rates to produceshear stresses and use these to determine the precision. Thewithin-laboratory coefficient of variation was found to be 0.31or 0.2 % of the average shear stress. The betwe
