ASTM_D_3769_-_15.pdf

Designation:D376915Standard 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 and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE1There is no known ISO equivalent to this standard.2.Referenced Documents2.1 ASTM Standards:2D3040 Practice for Preparing Precision Statements for Stan-dards Related to Rubber and Rubber Testing(Withdrawn1987)3E145 Specification for Gravity-Convection and Forced-Ventilation OvensE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Significance and Use3.1 This test method is used to indicate the deformationtendency of microcellular materials that may occur duringpaint application in an assembly plant operation.Since astandard specimen is used,do not assume heat sag measure-ments to be exactly those which will occur on a part during orafter the paint application and baking operation of an assemblyprocess.3.2 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.4.Apparatus4.1 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.1.4.2 Oven,conforming to the specifications for a Type IAlaboratory oven in accordance with Specification E145.4.3 Scaled Rule,accurate to 1 mm.4.4 Thickness Indicator,accurate to 0.03 mm.4.5 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.5.Test Specimens5.1 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 specimen thickness shall be3 mm.5.2 Three specimens to each material shall be tested.NOTE3If test specimens are cut from parts,the specimens must be cutfrom areas that are of constant thickness;that is,no ribs,bosses,holes,orother section changes are allowed.6.Conditioning6.1 Unless otherwise specified,condition the specimens andfixture a minimum of 1 h at 23 6 2C and 50 6 10%relativehumidity before testing.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 Sept.1,2015.Published September 2015.Originallyapproved in 1979.Last previous edition approved in 2010 as D3769-10.DOI:10.1520/D3769-15.2For 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 7.Procedure7.1 Measure the thickness in the clamping area of the testspecimen to the nearest 0.03 mm.7.2 Clamp the specimen in the fixture with a 100 6 1 mmunsupported overhang.Primed or painted surfaces are to bemounted facing up.7.3 After 5 min,measure the distance between the base andthe unsupported end of the specimen as shown in Fig.1 andcall this Ao.7.4 Place the clamped specimen in an air-circulating oven atthe test temperature of 120 6 1C for 60 6 1 min.7.5 After oven aging,remove the fixture with the specimenfrom the oven.7.6 After 5 min,repeat the measurement as in 7.3 for Aoandcall this distance Af.NOTE4Other combinations of te