1、Designation: D5478 09D5478 13Standard Test Methods forViscosity of Materials by a Falling Needle Viscometer1This standard is issued under the fixed designation D5478; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods cover the measurement of the viscosity of Newtonian and non-Newtonian liquids. These test methodsare a
3、pplicable to liquids having viscosities in the range from 5 104 to 103 Pas (0.5 to 106 cP). The shear rate range is dependentupon the needle used and viscosity of the liquid and may vary from 104 to 103 s1. With an extension bar and applied weight,a shear rate of 104 s1 may be achieved.1.2 The yield
4、 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) bymeasuring the steady-state (constant) or terminal velocities of cylindrical needles as they fall through the test
5、liquid under theinfluence 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 standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of th
6、e safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E1 Specification for ASTM Liq
7、uid-in-Glass ThermometersE2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids3. Terminology3.1 Definitions:3.1.1 dilatant or shear thickening fluid, nfluid in which the apparent viscosity increases with increasing shear rate.3.1.2 Newtonian fluid, nfluid in whi
8、ch the dynamic viscosity does not vary with shear rate but only with the temperature andpressure.3.1.3 Non-Newtonian fluid, nfluid in which the dynamic viscosity varies with shear rate over at least some shear rate range.3.1.3.1 DiscussionThis viscosity is sometimes referred to as the “apparent visc
9、osity” since it is not a true property of the fluid but a variable dependingon the shear rate. The viscosity of most non-Newtonian fluids fits a power law expression. A power law fluid is defined by thefollowing equation:a 5Kd/dt!n21 (1)where:a = apparent viscosity, Pas (or dynes/cm2 = P), mPas = cP
10、,K = fluid consistency, Pasn (or dynes n/cm2),1 These test methods are under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and are the direct responsibility ofSubcommittee D01.24 on Physical Properties of Liquid Paints and Paint Materials.Current e
11、dition approved Feb. 1, 2009Feb. 1, 2013. Published March 2009February 2013. Originally approved in 1993. Last previous edition approved in 20032009 aspublished as D5478 98 (2003).D5478 09. DOI: 10.1520/D5478-09.10.1520/D5478-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or
12、 contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes hav
13、e been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official doc
14、ument.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1d/dt = shear rate or velocity gradient, 1/s, andn = flow behavior index, dimensionless.3.1.4 pseudoplastic or shear
15、 thinning fluid, nfluid in which the apparent viscosity decreases with increasing shear rate.3.1.5 viscosity, nthe ratio between an applied shear stress to the resulting shear rate (velocity gradient) is defined as thedynamic viscosity. It is a measure of the resistance to flow of a fluid.3.1.5.1 Di
16、scussionIn the SI unit system, the units of viscosity are Pas. One mPas is equal to one centipoise (cP).3.1.6 yield stress, nsome fluids when subjected to a shear stress behave as deformable solids until a certain critical shear stress(yield stress or yield value) is reached after which they behave
17、as fluids.3.1.6.1 DiscussionExamples of such fluids include many paints and pigment pastes and certain food materials such as ketchup.4. Summary of Test Methods4.1 Test Method A consists of determining the viscosity of Newtonian liquids.FIG. 1 Schematic of Falling Needle ViscometerD5478 1324.2 Test
18、Method B consists of determining the apparent viscosity and shear rate of pseudoplastic and dilatant fluids in the powerlaw region.4.3 Test Method C consists of determining the apparent viscosity and shear rate of pseudoplastic and dilatant fluids outside ofthe power law region.4.4 Test Method D con
19、sists of determining the yield stress of liquids that have such a property.5. Significance and Use5.1 These test methods are applicable for measuring the rheological properties of varnishes and paints. In particular, the low tomoderate shear rate measurements provide information related to sag resis
20、tance, leveling, etc.6. Apparatus6.1 Viscometer, falling-needle-type and associated equipment listed as follows:6.1.1 Falling Needle Viscometer 3,4,5Aschematic of the falling needle viscometer is shown in Fig. 1. The viscometer consistsof a vertical cylindrical test section of diameter D. The liquid
21、 specimen is placed in the test section and the specimens temperatureis maintained constant by means of a constant temperature bath that circulates a liquid through another cylindrical container (waterjacket) that is coaxial to the test section. A thin hollow cylinder of length L with hemispherical
22、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 itsforward end that may be varied to change its density.After the needle has attained its constant terminal velocity, thisAnother typeof n
23、eedle is connected at the top with an extension bar and a weight holder so that external weights may be added to increase theeffective density of the needle and the maximum achievable shear rate. With any needle, terminal velocity is measured bydetermining the needle transit time between two circumf
24、erential marks a known distance apart on the test section (for opaqueliquids 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 constants of the system (L, D, d), the viscosity of
25、a Newtonian fluid can be calculatedfrom the instrument theory. For a non-Newtonian fluid whose viscosity depends upon the shear rate, a series of needles aredropped. The falling needle is an absolute method of viscosity measurement that does not need any instrument calibration.However, it may be che
26、cked through use of known certified viscous fluids such as standard oils.6.1.2 ThermometerAthermometric device calibrated to 0.1C whose accuracy, precision, and sensitivity are equal to or betterthan theASTM thermometerthermometers described in Specifications E1 or E2251. The use of non-mercury ther
27、mometers or otherdevices is highly recommended.6.1.3 Circulating Liquid Bath, capable of maintaining the test specimen temperature to 60.1C.6.1.4 Stopwatch or Electronic Device, capable of measuring to 60.01 s or an automatic sensing device with the same accuracy.7. Preparation of Specimen7.1 After
28、opening the specimen container, mix the fluid gently with a glass rod for 5 min.7.2 Pour the specimen carefully into the test section so as to minimize the formation of air bubbles. If available, a syringe isuseful for this purpose.7.3 Remix the specimen in the test container using the needle retrie
29、ver rod by pushing it up and down four times at a velocityof approximately 4 cm/s.7.4 Allow the specimen to remain at rest in the test section for a minimum of 5 min or until any air bubbles have risen to thesurface. Longer rest times may be used in the case of yield stress measurements.TEST METHOD
30、ANEWTONIAN FLUIDS VISCOSITY MEASUREMENTS8. Procedure8.1 Level the viscometer so that the central vertical axis of the test section is parallel to the gravity vector by using either abubble level or a plumb bob.8.2 Circulate the liquid from the constant temperature bath until the test specimen temper
31、ature is constant at the specified valuewith a variation of 60.1C.3 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. 20512058.4 Park, N. A., and Irvine, T. F., Jr., “The Falling
32、Needle Viscometer, A New Technique for Viscosity Measurements,” American Laboratory, Vol 20, November 1988, pp.5763.5 The sole source of supply of the falling needle viscometer known to the committee at this time is Stony Brook Scientific, Ltd., P.O. Box 147, 914 Filmore914 FillmoreRd., Norristown,
33、PA19403. If you are aware of alternative suppliers, please provide this information toASTM International Headquarters.Your comments will receive carefulconsideration at a meeting of the responsible technical committee,1 which you may attend. This instrument may be interfaced with a computer for data
34、 collection and analysis.A computer program is available for data analysis for instruments that are not interfaced.D5478 1338.3 To determine the viscosity, drop a needle along the central axis of the test section and measure its velocity by the amountof time taken to move between two of the measurem
35、ent lines. This may be done by using a stopwatch or an automatic sensingdevice. The measurement lines should be at least a test section diameter from the top and bottom of the liquid.8.4 Record the values of the needle velocity, the liquid and needle densities, the test specimen temperature, the loc
36、al accelerationof gravity and the test section, and needle dimensions D, L, and d.8.5 Drop additional needles of different densities to establish whether the fluid is Newtonian. If the measured viscosity isessentially constant using the different density needles, then the fluid is Newtonian.9. Calcu
37、lation9.1 Calculate the Newtonian fluid viscosity for any needle drop as follows:5gs 2l!UtG(2)where: = dynamic viscosity, mPas (= cP),g = local acceleration of gravity, cm/s2,s = needle density, g/cm3,l = test specimen density, g/cm3,Ut = measured needle terminal velocity, cm/s, andG = geometric con
38、stant depending upon the test section and needle dimensions D,L, and d that is furnished by the instrumentmanufacturer. Table 1 lists several typical geometric constants.where: = dynamic viscosity, mPas (= cP),g = local acceleration of gravity, cm/s2,s = needle density, g/cm3,l = test specimen densi
39、ty, g/cm3,Ut = measured needle terminal velocity, cm/s, andG = geometric constant depending upon the test section and needle dimensions D,L, and d that is furnished by the instrumentmanufacturer. Table 1 lists several typical geometric constants.10. Report10.1 Report the following information:10.1.1
40、 Name of the test specimen,10.1.2 Temperature of the test specimen, C, and10.1.3 Viscosity of the test specimen, mPas (= cP) (Note 1).NOTE 1If the same needle is dropped more than once, report the minimum, maximum, and average viscosity values. If needles of different densitiesare dropped, report th
41、e individual viscosity measurements.11. Precision and Bias11.1 PrecisionIn an interlaboratory study, six operators in six laboratories measured (four replicates) viscosities of threeNewtonian oils and one essentially Newtonian spar varnish. These materials covered a viscosity range of 100 to 1440 mP
42、a.smPas(cP). The within-laboratory coefficient of variation was found to be 2.70 or 0.5 % of the average viscosity. The correspondingbetween-laboratories coefficient was 4.58 or 0.9 % of the average viscosity. Based on these coefficients, the following criteriashould be used for judging the acceptab
43、ility of results at the 95 % confidence level:11.1.1 RepeatabilityTwo results of individual viscosity measurements obtained by the same operator at different times shouldbe considered suspect if they differ by more than 1.4 % relative.11.1.2 ReproducibilityTwo results of individual viscosity measure
44、ments obtained by operators in different laboratories shouldbe considered suspect if they differ by more than 2.4 % relative.TABLE 1 Geometric Constants (G) for Several SystemDiametersA (D) and Needle Lengths (L)System Diameter, Needle Length, G, Viscosity Range,cm cm 1/cm2 mPas (= cP)1.905 10.2 80.
45、89 501060.8044 4.2 529.8 101040.4996 4.2 12,816 0.520A Needle diameter = 0.3980 cm.D5478 13411.2 BiasBias has not been determined for this test method.TEST METHOD BAPPARENT VISCOSITY AND SHEAR RATE OF PSEUDOPLASTIC AND DILATANT FLUIDSIN POWER LAW REGIONS12. Procedure12.1 Follow the procedures in acc
46、ordance with 8.1 and 8.2.12.2 Drop a series of needles of the same geometry but different densities along the central axis of the test section and measuretheir velocities by the amount of time taken to travel between two of the measurement lines.This may be done by using a stopwatchor an automatic s
47、ensing device. The measurement lines should be at least a test section diameter from the top and bottom of theliquid.12.3 Record the values of the needle velocities, needle densities, the test specimen temperature, the local acceleration of gravityand the test section, and needle dimensions D, L, an
48、d d.13. Calculation13.1 Plot a graph of Loge(s l) versus LogeUt. If the points form a straight line then the shear rate is in the power law region(see 13.3) and the slope of the straight line is the flow index, n.13.2 Calculate the shear rate from the following equation:Loge/Ut!5A11B1 Logen1C1 Logen
49、!2 (3)1D 1 Logen!31E 1 Logen!41F 1Logen!5Loge/Ut!5A11B1 Logen1C1 Logen!2 (3)1D 1 Logen!31E 1 Logen!41F 1Logen!5where the values of A1, B1, C1, D1, E1, and F1 are given in Table 2 for the same representative systems and needles as in Table1.13.3 Calculate the apparent viscosity from the following equation:LogeF aUtgs 2l!G 5A21B2 Logen1C2 Logen!2 (4)1D2 Logen!31E2 Logen!41F2 Logen!5where the values of A2, B2, C2, D2, E2, and F2 are given in Table 2 for the same representative systems and
