ASTM_D_5478_-_13.pdf

Designation:D547813Standard 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 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 theviscosity of Newtonian and non-Newtonian liquids.These testmethods are applicable to liquids having viscosities in therange from 5 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.With an extensionbar and applied weight,a shear rate of 104s1may be achieved.1.2 The yield stress of liquids having this property may alsobe determined.1.3 These test 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 liquids may be measured using the same procedure.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of 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 Liquid-in-Glass ThermometersE2251 Specification for Liquid-in-Glass ASTM Thermom-eters with Low-Hazard Precision Liquids3.Terminology3.1 Definitions:3.1.1 dilatant or shear thickening fluid,nfluid in whichthe apparent viscosity increases with increasing shear rate.3.1.2 Newtonian fluid,nfluid in which the dynamic vis-cosity does not vary with shear rate but only with thetemperature and pressure.3.1.3 Non-Newtonian fluid,nfluid in which the dynamicviscosity varies with shear rate over at least some shear raterange.3.1.3.1 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 expression.Apower law fluid is defined by the following equation:a5 Kd/dt!n21(1)where:a=apparent viscosity,Pas(or dynes/cm2=P),mPas=cP,K=fluid consistency,Pasn(or dynesn/cm2),d/dt=shear rate or velocity gradient,1/s,andn=flow behavior index,dimensionless.3.1.4 pseudoplastic or shear thinning fluid,nfluid inwhich the apparent viscosity decreases with increasing shearrate.3.1.5 viscosity,nthe ratio between an applied shear stressto the resulting shear rate(velocity gradient)is defined as thedynamic viscosity.It is a measure of the resistance to flow ofa fluid.3.1.5.1 DiscussionIn the SI unit system,the units ofviscosity are Pas.One mPas is equal to one centipoise(cP).3.1.6 yield stress,nsome fluids when subjected to a shearstress behave as deformable solids until a certain critical shearstress(yield stress or yield value)is reached after which theybehave as fluids.3.1.6.1 DiscussionExamples of such fluids include manypaints and pigment pastes and certain food materials such asketchup.4.Summary of Test Methods4.1 Test Method A consists of determining the viscosity ofNewtonian liquids.1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings,Materials,and Applications and are the directresponsibility of Subcommittee D01.24 on Physical Properties of Liquid Paints andPaint Materials.Current edition approved Feb.1,2013.Published February 2013.Originallyapproved in 1993.Last previous edition approved in 2009 as published asD5478 09.DOI:10.1520/D5478-13.2For 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.*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 States1 4.2 Test Method B consists of determining the apparentviscosity and shear rate of pseudoplastic 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.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 moderate shear rate measurements provide information