StandardTestMethodfor
EffectsofHeatAgingonWeightLoss,Cracking,andChalkingofElastomericSealants1ThisstandardisissuedunderthefixeddesignationC792;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.
1.Scope
1.1Thistestmethodcoversalaboratoryprocedurefordeterminingtheeffectsofheatagingonweightloss,cracking,andchalkingofcured-in-placeelastomericjointsealants(single-andmulticomponent)foruseinbuildingconstruction.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyproblems,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.
1.3ThereisnoknownISOequivalenttothistestmethod.2.ReferencedDocuments2.1ASTMStandards:2C717TerminologyofBuildingSealsandSealants3.Terminology
3.1Definitions—SeeTerminologyC717fordefinitionsofthefollowingtermsusedinthistestmethod:compound,elastomeric,non-sagsealant,sealant,andself-levelingsealant.4.SummaryofTestMethod
4.1Threesealantspecimensarespreadonthinaluminumplatesand,afterdeterminingnetweightsofsealant,arecuredfor7daysat2362°C(7463.6°F)and5065%relativehumidity.Immediatelyfollowingthisinitialcuretimetwospecimensareexposedinaforced-draftovenmaintainedat7062°C(15863.6°F)for21days.Attheendofthisexposurethepercentageweightlossofthesealantisdeterminedandexaminationismadeforpresenceofcracksandchalking.
ThistestmethodisunderthejurisdictionofASTMCommitteeC24onBuildingSealsandSealantsandisthedirectresponsibilityofSubcommitteeC24.20onGeneralTestMethods.
CurrenteditionapprovedMay1,2008.PublishedJune2008.Originallyapprovedin1975.Lastpreviouseditionapprovedin2004asC792–04.2ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.
15.SignificanceandUse
5.1Weightlossthroughvolatilizationofcomponentsofasealantinabuildingjointmayaffectsealantappearancebecauseofshrinkageandsealantperformancebecauseofthelossoffunctionalsealantcomponents.Exposuretohigh-temperatureenvironmentswillacceleratethelossofvolatiles.5.2Thistestmethodmeasuresweightloss.Itcanbeusedincombinationwithaknowledgeofsealantdensitytoestimateshrinkage.Inaddition,whencomparedtosealanttheoreticalweightsolids,itprovidesanestimateoftheextenttowhichfunctionalsealantcomponentscanbevolatilizedwhenexposedtohighservicetemperatures.Substantiallossesofthistypemayhelppredictearlyfailuresindurability.Also,developmentofcracksorchalking,orboth,lessenssealantservicelife.However,asealantthatdevelopsnocracksorchalking,orlowweightlossinthistestmethod,doesnotnecessarilyassuregooddurability.
6.Apparatus
6.1Forced-DraftOven,controlledat7062°C(15863.6°F).
6.2Balance,sensitiveto0.01g.
6.3RectangularBrassFrame,withinsidedimensions130by40by6.4mm(5by11⁄2by1⁄4in.).
6.4AluminumPlates,three,each152by80by0.6to1.6mm(24to16gage).
6.5Straightedge,metalorplastic,about152mm(6in.)long.
6.6ThinKnifeBlade.
6.7Spatula,steel,about152mm(6in.)long.
7.Procedure
7.1Unlessotherwisespecifiedbythoseauthorizingthetest,standardconditionsoftemperatureandrelativehumidityforthetestshallbe2362°C,(7363.6°F)and5065%,respectively.
7.2TestofMulticomponentSealants:
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C792–04(2008)
7.2.1Conditionatleast400gofbasecompoundandappropriateamountofcuringagentinaclosedcontainerforatleast24hatstandardconditions;thenmixthoroughlyfor5min.
7.2.2Weighthethreealuminumplatestothenearest0.01g.7.2.3Filltherectangularframe,aftercenteringitonanaluminumplate,withaportionoftheconditionedcompound,andstrikeitoffflatwithastraightedge.Immediatelylifttheframefromthesealantafterseparatingitbyrunningathin-bladedknifealongtheinsideoftheframe(Note1).Preparethreesuchspecimens,weigheachtothenearest0.01g,andcurethemfor7daysatstandardconditions.
7.2.4Followingthe7-daycuringperiod,placetwoofthethreespecimensinthedraftovenfor21days,leavingthethird(control)specimenatstandardconditonsforthesameperiod.7.2.5Attheendofthe21-dayperiod,removethespecimensfromtheovenandallowtocoolfor1hatstandardconditions.Weighthemtothenearest0.01gandcalculatethepercentweightlossofthesealantsasfollows:
Weightloss,%5[~W22W3!/~W22W1!#3100
(1)
7.3.1Conditionatleast400gofcompoundinaclosedcontainerforatleast24hatstandardconditions.
7.3.2Followthesameprocedureasspecifiedin7.2.1-7.2.6,eliminatingthemixingnecessaryformulticomponentsealants.8.Report
8.1Reportthefollowinginformationforeachsampletested:
8.1.1Identificationofthesealanttested.
8.1.2Descriptionofthetypeofsealant,suchassingle-ormulticomponent,nonsagorself-leveling,color,etc.
8.1.3Percentweightlossesoftheheat-treatedspecimens.8.1.4Presenceofcrackingandchalkingascomparedwiththecontrolspecimen.Fig.1includesexamplesofcrackingobtainableinthistest.Number0representsnocracking.8.1.5Variation,ifany,fromthespecifiedtestprocedure.9.Precision
9.1Astatisticalanalysismadefromtheresultsobtainedfromaround-robintestinwhicheachofthreelaboratoriestestedsevensealantsamplesinaccordancewiththeprescribedtestforeffectofheatagingonweightlossresultedinthefollowing:
9.1.1Repeatability(thatis,thedifferencebetweentwodeterminationsofweightlossonthesamesamplewithinthesamelaboratory)was0.51%weightloss.
9.1.2Reproducibility(thatis,thedifferencebetweentheresultsoftwolaboratories,eachmakingtwoweightlossdeterminationsonthesamesample)was0.90%.
9.2Theresultsobtainedbythethreelaboratoriesinwhicheachlaboratorytestedsevensealantsamplesinaccordance
where:
W1=weightofaluminumplate,
W2=weightofaluminumplatewithfreshsealant,andW3=weightofplatewithsealantafterheataging21days.7.2.6Examinethesealantsforcrackingandchalkingandcomparewiththethird(control)specimen.
NOTE1—Inthecaseofapourablegradecompound,donotlifttherectangularframeuntilthesealantissufficientlysetthatitwillretainitsrectangularshape.
7.3TestofSingle-ComponentSealants:
NOTE1—Number0representsnocracking.
FIG.1ExamplesofCrackingObtainableinThisTest
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withtheprescribedtestfortheeffectofcrackingandchalkingwereclosetounanimous.Theexceptionwasthereportofonelaboratoryindicatingnocrackingorchalkingofonesample,whereastheremainingtwolaboratoriesreportedslightcrack-ingandchalking.
10.Keywords
10.1chalking;compound;cracking;elastomericsealants;heataging;non-sagsealants;self-levelingsealant;weightloss
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