ASTM_D_696_-_08e1.pdf

Designation:D696081Standard Test Method forCoefficient of Linear Thermal Expansion of PlasticsBetween 30C and 30C with a Vitreous Silica Dilatometer1This standard is issued under the fixed designation D696;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.1NOTEEditorially corrected parenthetical temperature values in 5.2 in March 2013.1.Scope*1.1 This test method covers determination of the coefficientof linear thermal expansion for plastic materials having coef-ficients of expansion greater than 1 106/C by use of avitreous silica dilatometer.At the test temperatures and underthe stresses imposed,the plastic materials shall have a negli-gible creep or elastic strain rate or both,insofar as theseproperties would significantly affect the accuracy of the mea-surements.NOTE1There is no known ISO equivalent to this standard.1.1.1 Test Method E228 shall be used for temperatures otherthan 30C to 30C.1.1.2 This test method shall not be used for measurementson materials having a very low coefficient of expansion(lessthan 1 106/C).For materials having very low coefficient ofexpansion,interferometer or capacitance techniques are rec-ommended.1.2 The thermal expansion of a plastic is composed of areversible component on which are superimposed changes inlength due to changes in moisture content,curing,loss ofplasticizer or solvents,release of stresses,phase changes andother factors.This test method is intended for determining thecoefficient of linear thermal expansion under the exclusion ofthese factors as far as possible.In general,it will not bepossible to exclude the effect of these factors completely.Forthis reason,the test method can be expected to give only anapproximation to the true thermal expansion.1.3 The values stated in SI units are to be regarded asstandard.The values in parentheses are for information only.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:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD4065 Practice for Plastics:Dynamic Mechanical Proper-ties:Determination and Report of ProceduresE228 Test Method for Linear Thermal Expansion of SolidMaterials With a Push-Rod DilatometerE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE831 Test Method for Linear Thermal Expansion of SolidMaterials by Thermomechanical Analysis3.Terminology3.1 DefinitionsDefinitions are in accordance with Termi-nology D883 unless otherwise specified.4.Summary of Test Method4.1 This test method is intended to provide a means ofdetermining the coefficient of linear thermal expansion ofplastics which are not distorted or indented by the thrust of thedilatometer on the specimen.For materials that indent,see 8.4.The specimen is placed at the bottom of the outer dilatometertube with the inner one resting on it.The measuring devicewhich is firmly attached to the outer tube is in contact with thetop of the inner tube and indicates variations in the length ofthe specimen with changes in temperature.Temperaturechanges are brought about by immersing the outer tube in aliquid bath or other controlled temperature environment main-tained at the desired temperature.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.30 on Thermal Properties(Section D20.30.07).Current edition approved Nov.1,2008.Published November 2008.Originallyapproved in 1942.Last previous edition approved in 2003 as D696 03.DOI:10.1520/D0696-08E01.2For 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 5.Significance and Use5.1 The coefficient of linear thermal expansion,betweentemperatures T1and T2for a specimen whose length is L0at thereference temperature,is given by the following equation:5L22 L1!/L0T22 T1!#5 L/L0Twhere L1and L2are the specimen lengths at temperatures T1and T2,respectively.is,therefore,obtained by dividing thelinear expansion per unit length by the change in temperature.5.2 The nature of most plastics and the construction of thedilatometer make 30 to