ASTM_D_3768_-_22.pdf

Designation:D376822Standard Test Method forMicrocellular UrethanesFlexural Recovery1This standard is issued under the fixed designation D3768;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 the flexural recovery of microcellular urethanes.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)3D3489 Test Methods for Microcellular Urethane MaterialsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE2935 Practice for Evaluating Equivalence of Two TestingProcesses3.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 E456.3.2 The following definition is from Test Methods D3489:3.2.1 microcellular urethane,nan elastomeric materialmade by the interaction of a polyol and an organic isocyanate,having cell diameters in the range from 0.0001 to 0.001 mm,with a minimum density of 160 kg/m3(10 lb/ft3).4.Significance and Use4.1 This test method is used to indicate the ability of amaterial to recover after a 180 bend around a 12.7-mm(0.5-in.)diameter mandrel at room temperature.4.2 Before proceeding with this test method,reference shallbe made to any specification for 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 Flexural Recovery Test FixtureThe test fixture shallconsist of a 12.7-mm diameter mandrel mounted to a baseequipped with a protractor.A drawing of a typical test fixtureis shown in Fig.1.5.2 Timer,capable of indicating seconds.5.3 Thickness Indicator,accurate to 0.03 mm.6.Test Specimens6.1 The test specimens shall be cut from molded plaques orparts.The recommended standard test specimen is 4 mm inthickness,and the minimum specimen thickness shall not beless than 3 mm.The specimen shall be 25 mm in width by 150mm in length(1 by 6 in.).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 March 15,2022.Published March 2022.Originallyapproved in 1979.Last previous edition approved in 2016 as D3768-16.DOI:10.1520/D3768-22.2For 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.17.Conditioning7.1 ConditioningCondition the test specimens and the testfixture at 23 6 2C(73.4 6 3.6F)and 50 6 10%relativehumidity for not less than 24 h prior to testing,unlessotherwise specified.7.2 Test ConditionsConduct tests in the standard labora-tory atmosphere of 23 6 2C(73.4 6 3.6F)and 50 6 10%relative humidity,unless otherwise specified.8.Procedure8.1 There shall