ASTM_D_1673_-_94_1998.pdf

Designation:D 1673 94(Reapproved 1998)An American National StandardStandard Test Methods forRelative Permittivity and Dissipation Factor of ExpandedCellular Polymers Used For Electrical Insulation1This standard is issued under the fixed designation D 1673;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(e)indicates an editorial change since the last revision or reapproval.INTRODUCTIONAlthough fundamentally similar to test methods used for solid electrical insulating materials in sheetor plate form,certain modifications in the procedures and measurement techniques are necessary forthe proper determination of the relative permittivities and dissipation factors of foamed or expandedcellular polymers.This is occasioned by the fact that in many,if not most,instances expanded cellularmaterials have surfaces that preclude the use of conventional electrodes such as metal foil attached bypetrolatum and similar adhesives,or conducting silver paint applied by brushing or spraying.Furthermore,it is generally true that slabs or plates of expanded cellular materials are available onlyin substantially greater thicknesses than those commonly used for test specimens of solid insulation.1.Scope1.1 These test methods cover procedures for determiningthe relative permittivities and dissipation factor of flat sheets orslabs of expanded cellular polymers of both the rigid andflexible types,at frequencies from 60 Hz to 100 MHz.Provision is made for measurements on specimens up to 50mm(2 in.)in thickness,but it is recommended that specimensgreater than 25 mm(1 in.)in thickness shall be tested atfrequencies up to a maximum of only about 1 MHz.1.2 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:D 150 Test Methods for AC Loss Characteristics and Per-mittivity(Dielectric Constant)of Solid Electrical Insulat-ing Materials2D 374 Test Methods for Thickness of Solid Electrical Insu-lation2D 1056 Specification for Flexible Cellular MaterialsSponge or Expanded Rubber3D 1711 Terminology Relating to Electrical Insulating Ma-terials23.Terminology3.1 For definitions of relative permittivity,dissipation fac-tor,and loss index,refer to Test Methods D 150 or Terminol-ogy D 1711.4.Significance and Use4.1 Relative Permittivity:4.1.1 Because a relatively large proportion of their volumesare composed of more or less uniformly distributed,isolated orinterconnected gas-filled cells,foamed or expanded cellularpolymers always have lower relative permittivities,at a givenfrequency and temperature,than the solid base resins fromwhich they are prepared.4.1.2 The relative permittivities of expanded cellular poly-mers are important because they determine the increase incapacitance between conductors,or between conductors andground,that will result when a circuit or component isencapsulated in such a material,over their correspondingvalues before encapsulation(when air is the surroundingmedium).Likewise,the relative permittivities of an expandedcellular polymer may serve as a measure of the decrease ofsuch capacitances caused by substitution of the expandedmaterial for a solid encapsulating compound or resin of knownrelative permittivity.1These test methods are under the jurisdiction of ASTM Committee D-9 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D 09.12 on Electrical Tests.Current edition approved Jan.15,1994.Published March 1994.Originallypublished as D 1673 59 T.Last previous edition D 1673 79(1989)e1.2Annual Book of ASTM Standards,Vol 10.01.3Annual Book of ASTM Standards,Vol 09.02.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.4.1.3 In transmission lines,such as coaxial cable,televisionlead-in cables,etc.,the reduction of relative permittivity of anexpanded material from its value in the original solid state hassignificant usefulness in design,since the capacitance per footof cable,and such cable characteristics as velocity of propa-gation and characteristic impedance are all dependent upon therelative permittivity of the insulating material.4.1.4 In wave guides,radomes,dielectric lenses,etc.,foruse at radio frequencies,if the cellular polymer is nonmagnetic,the relative permittivity(usually in combination with thedissipation factor)determines such transmission characteristicsas velocity of propagation,attenuation distance,decibel lossper meter,phase factor,complex index of refraction,index ofabsorption,and dielectric conductivity.44.1.5 The relative permittivity determination may serve as aproduction co