ASTM_D_3769_-_20.pdf

Designation:D376920Standard Test Method forMicrocellular UrethanesHigh-Temperature Sag1This standard is issued under the fixed designation D3769;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 This test method covers the procedure and apparatus formeasuring high-temperature sag of microcellular urethanematerials.1.2 The values stated in SI units are to be regarded asstandard.1.3 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE1There is no known ISO equivalent to this standard.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD3040 Practice for Preparing Precision Statements for Stan-dards Related to Rubber and Rubber Testing(Withdrawn1987)3E145 Specification for Gravity-Convection and Forced-Ventilation OvensE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE2935 Practice for Conducting Equivalence Testing inLaboratory Applications3.Terminology3.1 Terms used in this standard are defined in accordancewith Terminology D883,unless otherwise specified.For termsrelating to precision and bias and associated issues,the termsused in this standard are defined in accordance with Terminol-ogy E456.4.Significance and Use4.1 This test method is used to indicate the potentialtendency of microcellular materials to deform during paintapplication in an assembly plant operation.Since a standardspecimen is used,do not assume heat sag measurements to beexactly those which will occur on a part during or after thepaint application and baking operation of an assembly process.4.2 Before proceeding with this test method,reference shallbe made to the specification of the material being tested.Anytest specimen preparation,conditioning,or dimensions,orcombination thereof,and testing parameters covered in thematerials specification shall take precedence over those men-tioned in these test methods.If there are no materialspecifications,then the default conditions apply.NOTE2This test method is applicable to solid urethanes.5.Apparatus5.1 Test Fixture,capable of holding the specimens in a fixedcantilever position for the duration of the entire test procedure.The test fixture shall be constructed from a material such asaluminum or steel that exhibits a low coefficient of linearthermal expansion and therefore allows the test fixtures heightto be considered constant through the test.See Fig.1.5.2 Oven,conforming to the specifications for a Type IAlaboratory oven in accordance with Specification E145.5.3 Scaled Rule,accurate to 1 mm.5.4 Thickness Indicator,accurate to 0.03 mm.5.5 Base,a flat,smooth surface free of any surface irregu-larities that would affect the height measurements.The basemust be heat-resistant to the maximum temperature that the testfixtures will be exposed.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials-Plastics and Elastomers.Current edition approved July 1,2020.Published July 2020.Originally approvedin 1979.Last previous edition approved in 2015 as D3769-15.DOI:10.1520/D3769-20.2For 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.16.Test Specimens6.1 The test specimen shall have a minimum length of 125mm,and be 25 6 1 mm in width by the nominal thickness ofthe plaque or part.The recommended standard test specimen is4 mm in thickness.The minimum