1、Designation: D3769 15Standard 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
2、 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 stat
3、ed 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 regula
4、tory limitations prior to use.NOTE 1There 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-
5、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. S
6、ince 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 materia
7、l 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.
8、NOTE 2This 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 coeffi
9、cient 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
10、, 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
11、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.NOTE 3If test specimens are cut from parts, the specimens must
12、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 of1hat236 2C and 50 6 10 % relativehumidity before testing.1This test method is under the
13、jurisdiction ofASTM 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:
14、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 historica
15、l 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 States17. Procedure7.1 Measure the thickness in the clamping area of the testspecimen to
16、 the nearest 0.03 mm.7.2 Clamp the specimen in the fixture with a 100 6 1mmunsupported 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 clampe
17、d 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.NOTE 4Other combinations of test temperatures, test times,
18、andoverhang lengths are permitted subject to prior agreement between the testrequestor and the testing facility.These conditions are to be included in thetest report.8. Calculation8.1 Sag = Ao Af.9. Report9.1 The report shall include the following:9.1.1 Direction of cutting,9.1.2 Conditioning proced
19、ures before testing,9.1.3 Time and temperature of the test,9.1.4 Initial value at 23C, average of three,9.1.5 Final sag value at test temperature, average of three,and9.1.6 Specimen thickness.10. Precision and Bias10.1 Table 1 is based on a round robin conducted in 1980 inaccordance with Practice D3
20、040, involving three materialstested by four laboratories. For each material, all the sampleswere prepared at one source and the individual specimens werealso prepared at one source. Each test result consisted of oneindividual determination. Each laboratory obtained four testresults for each materia
21、l. (WarningThe explanation of r(10.2 10.2.2) is only intended to present a meaningful way ofconsidering the approximate precision of these test methods.The data in Table 1 shall not be applied to acceptance orrejection of materials, as these data apply only to the materialstested in the round robin
22、and are unlikely to be rigorouslyrepresentative of other lots, formulations, conditions, materials,or laboratories. Users of this test method shall apply theprinciples outlined in Practice E691 to generate data specific totheir materials and laboratory (or between specific laborato-ries). The princi
23、ples of 10.2 10.2.2 would then be valid forsuch data.)10.2 Concept of r in Table 1If Srhas been calculated froma large enough body of data, and for test results that wereaverages from testing three specimens for each test result, then:10.2.1 RepeatabilityTwo test results obtained within onelaborator
24、y shall be judged not equivalent if they differ by morethan the r value of that material. r is the interval representingthe critical difference between two test results for the samematerial, obtained by the same operator using the sameequipment on the same day in the same laboratory.10.2.2 Any judgm
25、ent in accordance with 10.2.1 would havean approximate 95 % (0.95) probability of being correct.10.3 There are no recognized standards by which to esti-mate bias of this test method.11. Keywords11.1 deformation; heat sag; high-temperature; microcellu-lar; sag; urethaneNOTE 1Not to scale.FIG. 1 Fixtu
26、re for High-Temperature SagD3769 152SUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue (D3769 - 10)that may impact the use of this standard. (September 1, 2015)(1) Five-year review. (2) Removed permissive language wherever needed.AST
27、M International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are en
28、tirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsa
29、nd should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee
30、on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or
31、at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 1 Precision for
32、Heat Sag TestMaterialFlexural ModulusMPa (psi)Values expressed in unit of mm (in.)Average SrArBUrethane A 700 (100 000) 7.06 (0.278) 1.55 (0.061) 4.34 (0.171)Urethane B 350 (50 000) 0.43 (0.017) 0.66 (0.026) 1.85 (0.073)Urethane C 175 (25 000) 3.40 (0.134) 3.53 (0.139) 9.88 (0.389)ASr= within-laboratory standard deviation for the indicated material. It is obtained by pooling the within-laboratory standard deviations of the test results from all of theparticipating laboratories:Sr5 ffss1d21ss2d21ssnd2g/ng.Br = within-laboratory critical interval between two test results = 2.8 Sr.D3769 153
