Designation: D 6546 00An American National StandardStandard Test Methods forand Suggested Limits for Determining Compatibility ofElastomer Seals for Industrial Hydraulic Fluid Applications1This standard is issued under the xed designation D 6546; 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1These test methods cover the procedure for measuringphysical properties of elastomer seals in the form of O-ringsafter exposure to industrial hydraulic uids and thermal aging.Themeasuredpropertiesarethencomparedtothephysicalproperties of elastomer seals that have not been exposed to theindustrial hydraulic uids and thermal aging. The changes inthese properties form a basis for assessing compatibility whenthesechangesarecomparedagainst thesuggestedlimitsinTable 1.1.2Whilethesetest methodsinvolvetheuseof O-rings,theycanalsobeusedtoevaluatethecompatibilityof theelastomericcompoundsofspecialtysealswithindustrialhy-draulic uids and their resistance to thermal aging. ThecompoundscanbemoldedintoO-ringsfor evaluationpur-poses.1.3These test methods provide procedures for exposingO-ring test specimens to industrial hydraulic uids underdenite conditions of temperature and time. The resultingdeterioration of the O-ring material is determined by compar-ingthechangesinworkfunction,hardness,physicalproper-ties, compression set, and seal volume after immersion in thetest uid to the pre-immersion values.1.4Thisstandarddoesnot purport toaddressall 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.1.5The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.2. Referenced Documents2.1ASTM Standards:D 395Test Methods for Rubber PropertyCompressionSet2D 412Test MethodsforVulcanizedRubberandThermo-plastic Rubbers and Thermoplastic ElastomersTension2D 471Test MethodforRubberPropertyEffectsofLiq-uids2D 1414Test Methods for Rubber O-Rings3D 2000Classication System for Rubber Products in Auto-motive Applications3D 2240Test Method for Rubber PropertyDurometerHardness2D 3677Test Methods for RubberIdentication by Infra-red Spectrophotometry2D 3767Practice for RubberMeasurement of Dimensions2D 5028Test Methodfor CuringProperties of PultrusionResins by Thermal Analysis4E 1131Test MethodforCompositional AnalysisbyTher-mogravimetry52.2 SAE Standard:6AS568AO-ring Sizes3. Terminology3.1Denitions:3.1.1batchalltheO-ringsmoldedfromthesamelotofmaterial and presented for inspection at one time.3.1.2compounda fully formulated elastomer materialcontaining all llers and cross- linking agents.3.1.3uid saturation effectthe absorption of uid by theelastomer until anequilibriumswell value is reachedat aparticular temperature.3.1.4O-ringarubberseal ofhomogeneouscompositionmolded in one piece to the conguration of a torus with circularcross section.3.1.4.1DiscussionO-rings are used as both dynamic andstatic seals. The size of the O-ring is normally designated by adash number corresponding to the size tables listed in AS568A.The dimensions for the O-rings used in these test methods arelisted in Annex A2.3.1.5ultimateelongationtheamount of stretchthat theO-ring is exposed to before breaking.1Thesetest methodsareunderthejurisdictionof ASTMCommitteeD02onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.NO.09 on Compatibility.Current edition approved April 10, 2000. Published June 2000.2Annual Book of ASTM Standards, Vol 09.01.3Annual Book of ASTM Standards, Vol 09.02.4Annual Book of ASTM Standards, Vol 08.03.5Annual Book of ASTM Standards, Vol 14.02.6Available from Society of Automotive Engineers, 400 Commonwealth Drive,Warrendale, PA 15096.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.6work functionwork done on a test specimen to cause20 % deformation.4. Signicance and Use4.1When more than one elastomer seal material is tested,the test methods yieldcomparative data onwhichtobasejudgements as to expected service quality. Suggested in-serviceproperty change limits are provided. Property changes beyondthese limits will indicate limited service life of the elastomerseal.4.2Thesetestmethodsattempttosimulateservicecondi-tions through controlled aging and evaluation of propertychanges but may not give any direct correlations with actualpart performance since actual service conditions vary widely.These test methods yield comparative data and indications ofproperty changes of the elastomeric seal material under idealservice conditions. These test methods can be used for qualitycontrol purposes, for engineering assessments, for serviceevaluation, andfor manufacturingcontrol. Theinformationfromthesetest methodscanbeusedtoanticipateexpectedservice quality.5. General Test Methods5.1Except as otherwise specied, the test methods forrubber O-rings referred to in 5.1.1-5.1.6, which are applicableingeneral tovulcanizedrubber, shall becompliedwithasrequired and are hereby made a part of these test methods.5.1.1Tension TestTest Methods D 412 and D 1414.5.1.2Compression SetTest Methods D 395 and D 1414.5.1.3FluidAgingTestMethodD 471andTestMethodsD 1414.5.1.4HardnessTest Method D 2240.5.1.5Compositional AnalysisTest Methods D 3677andTest Method E 1131.5.1.6Degree of CureTest Method D 5028.5.2In case of conict between the provisions of the ASTMtest methods referenced in 5.1.1-5.1.6 and the detailed provi-sionsofthetestmethodsin TestMethodsD 6546, thelattershall take precedence.6. Test Conditions6.1TemperatureThetesttemperatureshallbethemaxi-mum sustained temperature anticipated in service.6.2Immersion PeriodsThe following immersion periodsare recommended: 24 h, 72 h, 100 h, 250 h, 500 h, and 1000 h.The nal immersion period will depend upon the results of theprevious immersionperiod. If the changes inthe physicalproperties have deteriorated beyond the suggested limits, thenfurther testing is not required. The tolerance for any immersionperiod shall be6 1 % of the immersion period.7. Test Fluids7.1For reliable compatibility assessments, it is desirable touse the uid with which the elastomer will come in contact inactual service. For comparative tests, samples of uid from thesame drum or shipment shall be used.8. Test Specimen8.1Thetest specimensshall beO-ringsmoldedfromthesamecompoundbatchfromwhichtheactual seals will bemolded. The test samples should approximate the cross sectionof the actual seal to be used so that the uid saturation effect isproperlyconsidered. Thetestsamplesshouldbeeither-021,-120, -214, or -320 O-rings, in accordance withAS568A.These have an approximate inside diameter of 25.4 mm (1 in.)and represent the most popular cross sections of seals used inindustrial systems. The actual dimensions of each O-ring sizeare listed in Annex A2.8.2Test specimensshall bewipedcleanofexternal con-taminants prior to testing by using a clean dry wipe.9. Suggested Compatibility Test Limits9.1For a critical seal application, property change limits, asdescribed in Table 1, should be observed.9.2Allvaluesareinreferencetosoaktimeintheopera-tional uidat theoperatingtemperatureof theapplication.Values reect changes fromthe determined pre-immersionoriginal physical property values of the test specimens.9.3If thechanges arewithintheselimits, theelastomershould be considered compatible. Once a seal material is foundto be compatible, all seals for that system should be ordered byspecic compound or specication and not by Classication D200 call out number or generic polymer designation.10. Procedure for Change in Volume10.1Apparatus:10.1.1Test Container, a Mason jar (quart size) tted with alid to prevent liquid and vapor from escaping. The lid shall notcontaminate the test liquid. Cover the lid with aluminum foil.10.1.2Heating Device, a forced air oven, aluminum blockheater, or oil bath heater. Maintain the temperature within61C (1.8F).TABLE 1Property Change LimitsTime, h Maxi-mumVolumeSwell,%Maxi-mumVolumeShrinkage,%HardnessChange,Shore APointsMaxi-mumTensileStrengthChange,%Maxi-mumElongationChange,%Maxi-mumWorkFunctionChange,%Maxi-mumCompres-sion Set,%24 15 3 67 20 20 612 . . .70 15 3 67 20 20 612 20100 15 3 68 20 20 612 20250 15 4 68 20 20 612 25500 20 4 610 25 25 617 301000 20 5 610 30 30 620 35D 6546 00210.1.3Test SpecimenThe test specimen shall consist of anentire O-ring. The same specimen may be used for all tests withhardness and volume determinations made prior to stress-straintests. Place the test specimen in the test liquid so that it is notdistortedorincontactwiththesidesofthetestcontainerorwiththeothertest specimens. Test aminimumofthreetestspecimens at one time. It is also important that only O-rings ofonesizeandonematerial compoundbeplacedinthetestcontainer.10.1.4Analytical Balance, an analytical balance capable ofallowing a test specimen to be weighed whether in air or whilesubmerged in water.10.2Volume ChangeTest three specimens.10.2.1Weigh each test specimen in air, M1, to the nearest 1mg, and then weigh each specimen immersed in water, M2, atroom temperature. It is important that all air bubbles clingingto the test specimen be removed before reading the weight inwater. Blot the specimen dry.10.2.2Suspend the specimens in the glass jar by the use ofcorrosion-resistant wire. Separatethespecimensbybendingsmall loops in the wire or by locating themin differentlocations so that they do not contact each other.10.2.3Suspend the specimen vertically so that 25.4 mm (1in.) of test uid is between the lower extremity of the specimenand the bottom of the apparatus. Add enough test uid to coverthespecimentoadepthof25.4mm(1in.)overtheupperextremity of the specimen.10.2.4Place the test apparatus in the heating device adjustedto maintain the sample at the test temperature for the requiredlength of time. At the end of the required immersion period,remove the specimen from the apparatus. Cool the specimen toroom temperature by immersing it in a cool, fresh amount ofthe test uid for 45 min.10.2.5At the end of the cooling period, remove the speci-men from the uid, wipe with a cloth dipped in acetone, andblot dry. Weigh each test specimen in air, M3, and then weigheach specimen immersed in water, M4.10.2.6Some oils can be very viscous and may be difficult toremove with an acetone wipe. Since these oils do not readilyvolatize, specimensexposedtotheseoilscanbecooledbysuspending them for 45 min in air at room temperature shieldedfrom draft. This will allow the majority of the oil to drip off thesurface of the specimen. Then proceed with the acetone wipeandweighingprocessdescribedin10.2.5. Report whenthisalternate method of specimen cooling is used.10.2.7The change in volume is calculated as follows:DV, % 5~M32 M4! 2~M12 M2!~M12 M2!3 100 (1)where:M1= initial mass of specimen in air, g,M2= initial mass of specimen in water, g,M3= mass of specimen in air after immersion, g, andM4= mass of specimen in water after immersion, g.10.3VolumeShrinkage-SimulatedDryOut (Optional TestMethod)Test three specimens.10.3.1Insome situations whenlongdowntimes are ex-pected, the O-ring should not shrink beyond 5 % of its previousvolume change value since this can affect its ability to be aneffectivesealwhenthesystemisrestarted. Inthosecasesinwhich a positive volume change was obtained in 10.2 and longsystemdowntimes areanticipated, it is recommendedthatvolume shrinkage be determined. To perform this optional testmethod, additional O-rings will have to be tested in accordancewith10.2andthentestedinaccordancewith10.3sincethenormal test for volume change is immediately followed by thedestructive tensile test.10.3.2The test specimen shall consist on an entire O-ring.The specimen must rst be submitted for the volume swell test.This specimen is only to be used for this test sequence and notfor any other testing.10.3.3Place the test specimen from the volume swell test inaforced-air oventhat allowsair circulationaroundthetestspecimen, and maintain the oven at a test temperature of 23 61C (73.4 6 1.8F) for 22 6 0.25 h. At the end of the requiredperiod, remove the specimen from the oven and allow it to aircool.10.3.4Weigh each test specimen in air, M5, and then weigheach specimen immersed in water, M6.10.3.5The change in volume or shrinkage is calculated asfollows:DV, % 5~M52 M6! 2~M32 M4!~M32 M4!3 100 (2)where:M3= initial massof volumeswell specimeninair afterimmersion, g,M4= initial mass of volume swell specimen in water afterimmersion, g,M5= mass of volume swell specimen in air after dry out, g,andM6= massofvolumeswell specimeninwaterafterdryout, g.11. Changes in Tensile Strength, Work Function,Elongation, and Hardness11.1Original PropertiesThe original tensile strength,work function, ultimate elongation, and hardness shall bedetermined using a duplicate set of specimens of O-rings of thesame cross section as those that are to be immersed in the testuid. The O-rings shall be from the same batch as those that areto be immersed in the test uid.11.2Properties After Exposure to the Test Fluid, for deter-mining the tensile strength, work function, ultimate elongation,and hardness of specimens after immersion in the test uid atthe test temperature. At the end of the required immersion time,removethespecimens, andifnecessary, cool themtoroomtemperature in a fresh sample of the same uid for 45 min. Atthe end of the cooling period, remove the specimen from theuid, wipeit withaclothdippedinacetone, andblot dry.Immediatelydetermine the hardness, tensile strength, workfunction, and ultimate elongation in accordance with thefollowing test methods, using the original cross-sectional areaof the untreated specimens.11.2.1Threespecimensshallbetested. Thetestspecimenshall consist of the entire O-ring. These specimens must rst besubmitted to the volume swell test and cannot be used for anyother testing since physical property tests are destructive.D 6546 00311.3Hardness ChangeMeasure the hardness in accor-dancewithTestMethodsD 1414, Section16, usingamicro-hardness tester. Select the mean value fromthe multiplereadings taken on each O-ring, and then select the mean valuefor all theO-rings. (Themeanvaluefor hardnessmeasure-mentsisthenumericalmeanvalue;thusifvereadingsareobtained, for example, 70A, 69A, 69A, 72A, and71A, thenumerical mean would be 70.2 or 70A since shore hardness isalwaysreportedinwholenumbers.)ThemeanvalueforallO-rings shall be recorded. Measurements are to be taken beforeand after exposure to uid.11.3.1The hardness change is calculated as follows:DH 5 H22 H1(3)where:DH = hardness change,H1= hardness before uid exposure, andH2= hardness after uid exposure.The units are given as Shore A points and a plus or minussignshouldbeincluded. A negativesignwouldindicatethattheO-ringissofteningafterexposureanditshardnessvaluewouldbe less thanthe hardness value before exposure. Apositive sign would indicate that the O-ring is hardening afterexposureandits hardness valuewouldbegreater thanthehardness value before exposure.11.4Tensile Strength Change:11.4.1TestingMachineThe testingmachine shall con-form to the requirements specied in Section 3 of Test MethodsD 412withtheexceptionofgrips. GripsfortestingO-ringsshall consist of ball-bearing spools at least 8.89 mm (0.35 in.)in diameter and be capable of being brought within 19.05 mm(0.75 in.) center-to-center distance at closest approach. Stresseswithin the specimen shall be minimized by rotating one spoolor by lubricating the contact surface of the spools with castoroil.11.4.2Test SpecimenThe test specimen shall consist of anentire O-ring.11.4.3ProcedureBring the grips close enough together sothat the specimen can be installed without stretching. Separatethe grips to remove any slack in the specimen. Exercise carethat no load is placed on the specimen. Pull the specimen at arateof50.8cm/min(20in./min). Recordthebreakingforcevalue, F, at the time of rupture.11.4.4Calculations:11.4.4.1Tensile strength is calculated as follows:T 5 F/A (4)where:T = tensile strength, MPa (psi),F = breaking force, N (lb), andA = twice the cross-sectional area calculatedfromaxialthickness, W, as follows:A 5 p W2/2 5 1.57 W2mm2~in.2! (5)11.4.4.2Tensile strength change is calculated as follows:DT 5T22 T1T13 100 (6)where:DT = tensile strength change (%),T2= tensile strength after immersion, andT1= tensile strength prior to immersion.11.5Elongation Change:11.5.1Testing MachineSame as for tensile strengthchange.11.5.2Test SpecimenSame as for tensile strength change.11.5.3ProcedureSame as for tensile strength change,except recordthecenter-to-center distance(D) betweenthespools at rupture to the nearest 2.54 mm (0.1 in.).11.5.4Calculations:11.5.4.1Ultimate elongation is calculated as follows:E, % 5~2D 1 G 2C!C3 100 (7)where:D = distance between centers of the spool grips at the timeof rupture of the specimen,G = circumferenceofonespool(spooldiameter33.14),andC = inside circumference of the specimen (inside diameter3 3.14)11.5.4.2Change in elongation is calculated as followsDE, % 5E22 E1E13 100 (8)where:E2= elongation after immersion,E1= elongation prior to immersion.11.6Work Function (WF) Modulus Change:11.6.1Testing MachineSame as for tensile strengthchange.11.6.2ProcedureSame as for tensile strength change.11.6.3CalculationsCalculate the work function (WF) asthe energy per unit volume at 20 % elongation. This value isdetermined as the area under the stress-strain curve from 0 to20 %strain, andthetensiletestershouldbeprogrammedtodetermine this value.11.6.3.1Change in work function is calculated as follows:DWF 5WF22 WF1WF13 100 (9)where:DWF = change in work function,%,WF2= work function after immersion, MPa (psi), andWF1= work function prior to immersion, MPa (psi).12. Compression Set12.1Micrometer, for measuring the specimen thickness, inaccordance with Practice D 3767, Method A1.12.2Spacer Bars, to maintain the constant deection.Spacer bars for O-ring samples shall have a thickness of 9.5 60.02 mm (0.3756 0.001 in.).12.3CompressionDevice, consistingof twoor moreatsteel plates betweentheparallel faces of whichtheO-ringspecimens may be compressed, as shown in Fig. 1. Steelspacers for the required 25 % of compression shall be placedon each side of the O-ring specimens to control their thicknessD 6546 004whilecompressed. Thesteel surfaces contactingtherubberspecimens shall be ground to a maximum roughness of 250 m(10 in.) and then chromium plated and polished.12.4Oven, a forced air oven capable of maintaining the testtemperature within6 1C (1.8F).12.5PlatesThe plates between which the O-ring testspecimeniscompressedshall bemadeofsteel ofsufficientthickness (at least 9.560.02mm(0.37560.001in.) orthicker) to withstand the compressive stresses without bending.The surfaces against which the O-ring specimen is held shallhaveahighlypolishedchromium-platednishandshall becleaned thoroughly and wiped dry before each test.12.6Original Thickness MeasurementMeasure the origi-nal thickness of the specimen to the nearest 0.02 mm (0.001in.). Place the specimen on the anvil of the micrometer so thatthe presser foot will indicate the thickness at the central portionof the top and bottom faces.12.7Applicationof CompressiveForcePlacetheO-ringtest specimenbetweentheplatesofthecompressiondevicewith the spacers on each side, allowing sufficient clearance forthe bulging of the O-ring when compressed. Where a lubricantis applied, it shall consist of a thin coating of the O-ring, withalubricanthavingsubstantiallynoactionontherubber. Formost purposes, asiliconeor uorosiliconeuidissuitable.Tightentheboltssothat theplatesaredrawntogether uni-formly until they are in contact with the spacers. The amountof compression employed shall be approximately 25 %. Asuitable mechanical or hydraulic device may be used tofacilitate assembling and disassembling the test xture.12.8Test Temperature and TimeThe test temperature shallbe the maximumanticipated service temperature. The testtimes shall be72h, 100h, 250h, 500h, and1000h. Incomparative tests, use identical temperature and test periods.12.9Test SpecimenThe test specimens should be O-ringsmolded from the same compound from which the actual sealswill be molded. The test samples should approximate the crosssection of the actual seal to be used so that the uid saturationeffect is properly considered. The test samples should be either-021, -120, -214, or -320O-rings. Aminimumof twotestspecimens should be tested at one time. It is important that onlyO-rings of one size and one material be placed in thecompression xture.12.10Test FluidFor accurate compatibility assessment, itis desirable to use the uid with which the elastomer will comeinto contact when in service. For comparative tests, samples ofuid from the same drum or shipment shall be used.12.11Test Container, a Mason jar (quart size), tted with alid to prevent liquid and vapor from escaping. The lid shall notcontaminate the test liquid. Cover the lid with aluminum foil.12.12Test ProcedureThe test specimen shall be at roomtemperature when inserted in the compression device. Place theassembled compression device, immersed in the test uid, inthe oven within 2 h after completion of the assembly, and allowit to remain there for the required test period at the testtemperature. Attheendofthetestperiod, releasetheplatesimmediately and allow the specimens to cool to room tempera-ture for 45 min in a fresh portion of the test liquid.12.13Final Thickness MeasurementAfter the rest period,measure the nal thickness at the center of the test specimen inaccordance with Practice D 3767, Method A1.12.14Calculate the compression set expressed as a percent-age of the original deection as follows:C 5@~to2 tf!/~to2 tn!# 3 100 (10)where:C = compression set expressed as percentage of the origi-nal deection,to= original thickness of specimen,tf= nal thickness of specimen, andtn= thickness of spacer bar used.Record the value for C.13. Material Traceability and Compound Conrmation13.1Toprovide full traceabilityof the compoundbeingqualied and to ensure that the compound and the state of curedo not change during production, an FTIRspectrumof arandomly chosen qualication part shall be obtained in accor-dance with Test Methods D 3677. This spectrum appropriatelydated and recorded shall remain part of the permanent recordFIG. 1 Compression Device for O-ring SpecimensD 6546 005forthequaliedcompound. Copiesofthisrecordshouldbeavailable for reference.13.2In addition, a TGA curve will be obtained for the samesampleinaccordancewithTest MethodE 1131. Thiscurve,showing compositional analysis, will also be appropriatelydatedandrecordedandshall remainpart of thepermanentrecord for the qualied compound.13.3ADifferential Scanning Calorimetry (DSC) curve,conrming the degree of cure of the sample, will be obtainedin accordance with the procedure listed in Annex A1. This DSCcurve will be properly dated and recorded and will also becomepart of the permanent record for the qualied compound. Thispermanent record, documenting the qualied compound, shallbeusedtoconrmthat productionpartsaremadefromthesame compound as qualied and that they are fully cured aswere the qualied elastomer parts.13.4To compare the FTIR spectra of production parts withthequaliedmaterial, aviewfoil of eachspectrumcanbemadeandoverlaidoneatoptheother. Themajorfeaturesofbothspectrashouldbeidentical. ForTGA comparisons, theweight loss over specic temperature ranges for both thequalied elastomer sample and the production sample shouldbe the same and their curves identical in appearance. Identitycan again be evaluated using the view foil technique.14. Report14.1StatethatthetestwasconductedinaccordancewithTest Methods D 6546, and report the following:14.1.1Date,14.1.2Cure date and batch number of the test specimens,14.1.3Dates of the various periods of exposures,14.1.4Immersion liquid used,14.1.5Temperature of exposure,14.1.6Exposure period,14.1.7All observed and recorded data, including the type ofproperties being reported,14.1.8Results calculated in accordance with the precedingprocedures, and14.1.9Conclusions of the tests based upon the compatibilitylimits listed in Section 9.14.2TheFTIR, TGA, andDSCresults shouldbemain-tained on le for comparison to the results for production parts.15. Precision and Bias15.1The precision and bias of these test methods formeasuring physical properties of new O-rings and O-rings afterexposuretoindustrialhydraulicuidsandthermalagingareessentially as specied in Test Methods D 1414, PracticeD 3677, and Test Method E 1131.16. Keywords16.1compatibility; density; elastomer seal; elongation; uidaging; hardness; industrial hydraulic uid; O-ring; tensilestrength; volume shrinkage; volume swell; work functionANNEXES(Mandatory Information)A1. TEST PROCEDURE FOR DETERMINING DEGREE OF CURE OF ELASTOMERS BY DIFFERENTIAL SCANNINGCALORIMETRY (DSC)A1.1ScopeA1.1.1This test methodcovers thedeterminationof thecure state of elastomers by DSC. It is based on Test MethodD 5028. This test methodis applicable toelastomers withadequate vulcanizers. The normal operating temperature rangeis from room temperature to 250C (482F), but not limited tosuch. All elastomers should be fully cured.A1.2ApparatusA1.2.1Differential Scanning Calorimeter, capable of heat-ing a test specimen and a reference material at a controlled rateuptoat least 20C(68F) per minuteandof automaticallyrecording the differential heat ow.A1.2.2Specimen Holders, composed of clean aluminum orother highthermal conductivitymaterial. Specimenholdersmay be of the open, covered, or sealed type.A1.2.3Nitrogen, or other inert purge gas supply.A1.2.4Flowmeter, for purge gas.A1.2.5RecordingCharts, fortemperaturerecordingappa-ratus withsuitable graduationfor measurements of energydifferential or time.A1.3CalibrationA1.3.1Calibrate the apparatus in accordance with themanufacturers instructions withappropriate standardrefer-ence materials at the same heating rate to be used for samples.For thetemperaturerangeof thisprocedure, indiumwithamelting point of 156C (312.8F) may be used.A1.4ProcedureA1.4.1Cured Elastomer Part:A1.4.1.1Randomlyselectacuredelastomerpartandran-domly choose a small section of the part from its center, andweigh out 76.54 to 153.08 mg of the section.A1.4.1.2Crimp a at metal cover against the pan with thesample sandwiched between them to ensure good heat transfer.Place the sample in the DSC cell.D 6546 006A1.4.1.3Intimate thermal contact between the sample andthe thermocouple is essential for reproducible results.A1.4.1.4Purgethecellwithnitrogenat50to100cc/min(3.06 to 6.10 in.3/min) gas ow rate.A1.4.1.5Heat thesampleat arateof 10C(50F)/ minunder nitrogen atmosphere from ambient to a temperature highenough to achieve the entire exothermic curing curve. Recordthe thermogram.FIG. A1.1 Thermogram Representative of an Uncured ElastomerFIG. A1.2 Thermogram Representative of a Fully Cured ElastomerD 6546 007A1.4.1.6Measuretheheat of reaction(DHR), theshadedarea of Fig. A1.1 (see Figs. A1.1 and A1.2).A1.5CalculationA1.5.1Use the resulting thermogramto determine theexothermicheat of thecuringreaction(DHR) of thecross-linking reaction. This is used to indicate the extent of cure. Afully cured material shall exhibit a DHR of 0 cal./gm (0 Btu/lb).Fig. A1.2 depicts a fully cured material.A1.5.2If the sample exhibits a DHR of 0 cal./gm (0 Btu/lb),thesampleisfullycured. If thesampleexhibitsaDHRofgreater than 0 cal./gm (0 Btu/lb) (see Fig. A1.1), run a duplicatesample. If the duplicate sample yields aDHR of 0 cal./gm (0Btu/lb), run a third sample such that two independent runs arein agreement. If the duplicate sample yields a DHR greater than0 cal./gm (0 Btu/lb), the elastomer part is not fully cured andprocessing is not consistent.A1.6ReportA1.6.1Report the following information:A1.6.1.1Sample identication including compound andbatch inside diameter and mass,A1.6.1.2Heating rate and purge gas owrate,A1.6.1.3Value ofDHR,A1.6.1.4Date of testing, andA1.6.1.5Copies of the actual DSC curves.A1.7Precision and BiasA1.7.1Since this test method is designed to determinewhetherasampleisfullycuredornot, theheat ofreaction(DHR) is the value of interest. If the value of DHR is positive,thenthesampleisnot fullycured. Calorimetricprecisionisnormally61 %andcalorimetricaccuracyisalso61 %, butfully cured materials have no exotherm. What is important indetermining if a material is fully cured is the stability of thebaselinebecauseanypositivevalueabovebaselinecanbeinterpreted as an exotherm. Baseline noise for these types ofinstruments is 0.00431cal (0.0000171Btu). Baselinenoiseduringaruncanineffectcreateapositiveindication. Ifthemaximumbaselinenoisevalueis dividedbytheminimumsample weight, 76.54 mg, than a baseline maximum deviationof0.0563cal/gmcanbeexpected.Therefore, anytestvaluethat ranged from 0 to +0.0563 cal/gm would be equivalent tofully cured material.A2. SIZES OF O-RINGS USED IN TEST PROCEDURESA2.1 Table A2.1 lists the actual sizes of the O-rings used inthe test methods. The sizes are in accordance with AS568A.TABLE A2.1O-ring SizesAS568ADesignationInsideDiameter(in.)Cross Section, in. Inside Diameter(mm)CrossSection, mm-021 0.9266 0.009 0.0706 0.003 23.526 0.23 1.786 0.08-120 0.9876 0.010 0.1036 0.003 25.076 0.25 2.626 0.08-214 0.9846 0.010 0.1396 0.004 24.996 0.25 3.536 0.10-320 1.1006 0.012 0.2106 0.005 27.946 0.30 5.336 0.13D 6546 008ASTM 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 entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ve years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand 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 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,UnitedStates. Individual reprints(singleormultiplecopies)of thisstandardmaybeobtainedbycontacting ASTMat theaboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTMwebsite(www.astm.org).D 6546 009