1、Designation: C1735 11Standard Test Method forMeasuring the Time Dependent Modulus of Sealants UsingStress Relaxation1This standard is issued under the fixed designation C1735; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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. Scope1.1 This test method covers a procedure for measuring thetime dependence of modulus in elastomeric joint sealants in
3、atest specimen configuration described in Test Method C719.These sealant materials are typified by highly filled rubbermaterials. Any Mullins effect is first assessed and mitigated intwo loading-unloading cycles. Time dependence of modulus inmaterials is then determined using a stress relaxation pro
4、ce-dure.1.2 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.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
5、appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C717 Terminology of Building Seals and SealantsC719 Test Method for Adhesion and Cohesion of Elasto-meric Joint Sealants Under Cyclic Movement (
6、HockmanCycle)E4 Practices for Force Verification of Testing MachinesE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE631 Terminology of Building ConstructionsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Def
7、initions:3.1.1 For definitions of terms used in this test method, referto Terminologies E631 and C717.4. Summary of Test Method4.1 This test method consists of two loading cycles wherestrain is increased froma0%toauser-defined maximumstrain and one stress relaxation procedure at a strain no greatert
8、han23 of the user-defined maximum strain. A schematicdiagram of this test strain history is shown in Fig. 1.4.2 The motivation for the two loading-unloading cycles isto assess if any Mullins effect is present and to mitigate any ofthis effect in the subsequent stress relaxation test. As long asthe m
9、aximum strain achieved during the first deformation isnot exceeded, however, all subsequent loadings follow thesame stress-strain curve.4.3 Stress relaxation procedure is based on a sudden impo-sition of either a tensile or compressive strain on the testspecimen at a value of no more than23 of the m
10、aximum strainand the measurement of the load required to maintain thistensile or compressive strain as a function of time.4.4 The conversion of load relaxation values to apparentmodulus and fractional change in apparent modulus is accom-plished by inputting information about the specimen geometryand
11、 the amount of deformation into an equation that is based onthe statistical theory of rubber-like elasticity.5. Significance and Use5.1 The intent of this test method is to determine the timedependence of modulus in building joint sealants using twoloading-unloading cycles to identify and mitigate a
12、ny Mullinseffect, and followed by a stress relaxation procedure todetermine the time dependent modulus.5.2 This test method has found applications in screening theperformance of building joint sealants since the modulus is oneindicator of the ability of elastomeric building sealant towithstand envir
13、onmental induced movements.6. Apparatus6.1 Testing MachineAny testing machine in compliancewith Practices E4, capable of producing a constant crossheaddisplacement rate in displacement control and equipped withmeans for recording complete load versus displacement curvesduring the test.1This test met
14、hod is under the jurisdiction ofASTM Committee C24 on BuildingSeals and Sealants and is the direct responsibility of Subcommittee C24.20 onGeneral Test Methods.Current edition approved Aug. 15, 2011. Published October 2011. DOI:10.1520/C1735-11.2For referenced ASTM standards, visit the ASTM website,
15、 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6
16、.2 Load CellThe load cell of the testing machine shall becapable of recording the load with an accuracy of 61%ofthemaximum indicated value.6.3 Loading FixturesUsed to mount specimens to thetesting machine so that the surface of the substrate is perpen-dicular to the direction of the applied load and
17、 to minimize anyeccentric loading in the test specimen.6.4 Air-circulating OvenTo condition specimens at thespecific temperature and relative humidity.6.5 Mechanical Fastener or Rubber BandsTo hold aspecimen assembly together before and after filling it withsealant compound.6.6 Geometry Measuring To
18、olTo measure the dimensionsof aluminum substrate and sealant to an accuracy of at least 65mm (0.2 in.). Because stress is the load per area exerted on thetest specimen, an accurate measurement of the geometry iscritical.7. Preparation of Test Specimen7.1 Test conditions of temperature and relative h
19、umidityused throughout this test method are defined in TerminologyC717.7.2 The standard substrate used in the test shall be alumi-num alloy (76.2 by 12.7 by 12.7 mm) (3 by 0.5 in. by 0.5 in.),6063-T5, or 6061-T6 with anodizing process AA-M10C22A31. Prior to use, the aluminum alloy shall be cleanedac
20、cording to a procedure described in the Test Method C719,which involves cleaning the substrate by wiping the surfacewith methyl ethyl ketone or similar solvent. Then dip thesurface in a detergent solution.An alternative would be a 0.1 %solution of a clear hand dishwashing detergent. These solutionss
21、hould be made up in distilled or deionized water. Rinse thesurface (without touching it) in distilled or deionized water andallow it to air dry.7.3 Where use of primer is recommended by the sealantmanufacturer, substrate materials shall be primed with therecommended primer or primers.7.4 Mix thoroug
22、hly for 5 min at least 250 g of basecompound with the appropriate amount of curing agent beingcareful not to generate excess heat. For single-componentsealants, no mixing of components is required. Dispense thecompound from a cartridge into a specimen cavity (50.8 by12.7 by 12.7 mm) (2 by 0.5 by 0.5
23、 in.) formed by two parallelsubstrate faces (50.8 by 12.7 mm) (2 by 0.5 in.) with apolytetrafluoroethylene (PTFE) film on the back and PTFEspacers (12.7 by 12.7 by 12.7 mm) (0.5 by 0.5 by 0.5 in.) oneach end, as shown in Fig. 2.7.5 Use appropriate mechanical fasteners or rubber bands tohold the spec
24、imen cavity together before and after filling itwith the compound.7.6 Condition the specimen in the fixture at the standardconditions of temperature and relative humidity for a minimumof 5 h. Then remove the mechanical fasteners or rubber bandsand the PTFE backing film. Keep the PTFE spacers and the
25、aluminum substrate intact.7.7 Allow specimen to cure according to the Test MethodC719 specifications.7.8 Test specimens surfaces should be smooth and free fromnicks and scratches.7.9 The finished test specimen is shown in Fig. 3.8. Number of Test Specimens8.1 Test at least three specimens of each se
26、alant.The value of t0is 20 s and t1is typically 2000 s.FIG. 1 Strain History Used for Two Loading-Unloading Cycles and a Stress Relaxation MeasurementFIG. 2 Illustration of Specimen Preparation Before Filling it withthe Sealant CompoundC1735 1129. Procedure9.1 Perform the test at the standard condit
27、ions of tempera-ture and relative humidity stated in 7.1. Tests at other ambienttemperature and relative humidity may be run if desired.9.2 Mount the specimen (as prepared in Section 7)inthefixture of the testing machine. Exercise precautions to mini-mize axial misalignment.9.3 Set the testing machi
28、ne at a crosshead displacement rateof 20 mm/min (0.787 in./min). Set the direction of appliedstrain, either tensile or compressive.9.4 Apply load to the specimen until the strain reaches themaximum strain, after which the specimen is completelyunloaded at the same crosshead displacement rate.9.5 The
29、 specimen is allowed to rest for 200 s. This is doneto ensure the viscoelastic recovery from one loading is com-plete before the next loading is initiated.9.6 Repeat 9.4 and 9.5 for the second loading-unloadingcycle.9.7 Set the testing machine at a crosshead displacement rateof 1000 mm/min (39.37 in
30、./min).9.8 Apply load to the specimen until the strain reaches thedesired test strain, no greater than23 of the maximum strainand hold that value while load is monitored as a function oftime. The time required to load the specimen is less than1ssothe first data point is not taken until after 10 s to
31、 avoid transienteffects associated with loading.9.9 Inspect the sample to note the locus of joint failure, ifany failure occurs.10. Calculation and Analysis10.1 Calculate an apparent modulus, Ea, using a relationshipbased on the statistical theory of rubber-like elasticity:Ea t,l! 53Lt!WB l2l22!(1)w
32、here:L = load, N (lb),W = length of the specimen, m (in.),B = depth of the specimen, m (in.),t = time, s,l = extension ratio, which is given by:l51 1DH(2)where:D = crosshead displacement of testing machine, andH = width of the specimen, m (in.).10.2 For convenience in comparing the relative change i
33、napparent modulus of materials during environmental expo-sures, the fractional change in apparent modulus, F, may becalculated as a function of time:F 5Eat1!Eat0!(3)where:Ea(t0) = apparent modulus at time, t0, andEa(t1) = apparent modulus at time, t1.10.3 A plot of the fractional change in apparent
34、modulus isuseful for comparison between different exposure times. Forsuch a graph, no change would be represented as a horizontalstraight line at F = 0. A horizontal line above or below F =0indicates that exposure causes a vertical shift in the stressrelaxation curve but no change in shape (that is,
35、 the timedependence does not change. Something other than a horizon-tal straight line indicates a change in time dependence.11. Report11.1 Report the following information:11.1.1 Identification of the sealant tested, including type,source, manufacturer code number, curing conditions em-ployed,11.1.2
36、 Identification of the substrate used,11.1.3 Name and description of primers used, if any,11.1.4 Temperature and relative humidity,11.1.5 Number of specimens tested,11.1.6 Type of strain (compressive or tensile),11.1.7 Maximum strain, test strain.11.1.8 Descriptive of the type of failure, if any:11.
37、1.8.1 Cohesive failure, if separation occurred within thematerial,11.1.8.2 Adhesive failure, if separation occurred at theinterface of the substrate and the sealant,11.1.8.3 Mixed failure, if both adhesive and cohesive failureregions are present.11.1.9 Records in terms of apparent modulus or normali
38、zedmodulus as a function of time.12. Precision and Bias12.1 The precision of this test method is based on aninter-laboratory study of C1735, conducted in 2009. A singlelaboratory participated in this study, testing samples of SealantE at discrete time periods. Every “test result” represents anindivi
39、dual determination, and the laboratory reported fourreplicate test results at each time segment. For reportingpurposes, these results were grouped into three broad timecategories (550 s, 50200 s, and 5002000 s). Except for theuse of a single laboratory and material, Practice E691 wasH, B and W are t
40、he width, depth and length of the specimen, respectively.FIG. 3 Geometry for the Sealant SpecimenC1735 113followed for the design and analysis of the data; the details aregiven in ASTM Research Report No. C24-1060.312.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be
41、 judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.12.1.1.1 Repeatability l
42、imits are listed in Table 1.12.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more than the “R” valuefor that material; “R” is the interval representing the criticaldifference between two test results for the same material,obtained by different operator
43、s using different equipment indifferent laboratories.12.1.2.1 Reproducibility limits cannot be determined in asingle-laboratory study.12.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177.12.1.4 Any judgment in accordance with statement 12.1.1
44、would normally have an approximate 95 % probability of beingcorrect, however the precision statistics obtained in this ILSmust not be treated as exact mathematical quantities which areapplicable to all circumstances and uses. Consider the repeat-ability limit as a general guide, and the associated p
45、robabilityof 95% as only a rough indicator of what can be expected.12.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.12.3 The precision statement was determined through sta-ti
46、stical examination of 232 test results, submitted by a singlelaboratory, on a single sealant.12.3.1 The sealant used in this test was described as: SealantE, a sample that is representative of a commerically viableformulation.13. Keywords13.1 elastomeric joint sealant; environmental attack; Hock-man
47、 cycle; modulus; Mullins effect; stress relaxationASTM 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 right
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