ASTM_D_5470_-_12.pdf

Designation:D547012Standard Test Method forThermal Transmission Properties of Thermally ConductiveElectrical Insulation Materials1This standard is issued under the fixed designation D5470;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*1.1 This standard covers a test method for measurement ofthermal impedance and calculation of an apparent thermalconductivity for thermally conductive electrical insulationmaterials ranging from liquid compounds to hard solid mate-rials.1.2 The term“thermal conductivity”applies only to homo-geneous materials.Thermally conductive electrical insulatingmaterials are usually heterogeneous and to avoid confusion thistest method uses“apparent thermal conductivity”for determin-ing thermal transmission properties of both homogeneous andheterogeneous materials.1.3 The values stated in SI units are to be regarded asstandard.1.4 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prior to use.2.Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insu-lation(Withdrawn 2013)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1225 Test Method for Thermal Conductivity of SolidsUsing the Guarded-Comparative-Longitudinal Heat FlowTechnique3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 apparent thermal conductivity(),nthe time rate ofheat flow,under steady conditions,through unit area of aheterogeneous material,per unit temperature gradient in thedirection perpendicular to the area.3.1.2 average temperature(of a surface),nthe area-weighted mean temperature.3.1.3 composite,na material made up of distinct partswhich contribute,either proportionally or synergistically,to theproperties of the combination.3.1.4 homogeneous material,na material in which rel-evant properties are not a function of the position within thematerial.3.1.5 thermal impedance(),nthe total opposition that anassembly(material,material interfaces)presents to the flow ofheat.3.1.6 thermal interfacial resistance(contact resistance),nthe temperature difference required to produce a unit of heatflux at the contact planes between the specimen surfaces andthe hot and cold surfaces in contact with the specimen undertest.The symbol for contact resistance is RI.3.1.7 thermal resistivity,nthe reciprocal of thermal con-ductivity.Under steady-state conditions,the temperaturegradient,in the direction perpendicular to the isothermalsurface per unit of heat flux.3.2 Symbols Used in This Standard:3.2.1 =apparent thermal conductivity,W/mK.3.2.2 A=area of a specimen,m2.3.2.3 d=thickness of specimen,m.3.2.4 Q=time rate of heat flow,W or J/s.3.2.5 q=heat flux,or time rate of heat flow per unit area,W/m2.3.2.6 =thermal impedance,temperature difference perunit of heat flux,(Km2)/W.4.Summary of Test Method4.1 This standard is based on idealized heat conductionbetween two parallel,isothermal surfaces separated by a test1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.19 on Dielectric Sheet and Roll Products.Current edition approved Jan.1,2012.Published February 2012.Originallyapproved in 1993.Last previous edition approved in 2011 as D5470 11.DOI:10.1520/D5470-12.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.*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 specimen of uniform thickness.The thermal gradient imposedon the specimen by the temperature difference between the twocontacting surfaces causes the heat flow through the specimen.This heat flow is perpendicular to the test surfaces and isuniform across the surfaces with no lateral heat spreading.4.2 The measurements required by this standard when usingtwo meter bars are:T1=hotter temperature of the hot meter bar,K,T2=colder temperature of the hot meter bar,K,T3=hotter temperature of the cold meter bar,K,T4=colder temperature of the cold meter bar,K,A=area of the test surfaces,m2,andd=specimen thickness,m.4.3 Based on the idealized test configur