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Adhesive Application Guide.pdf

Adhesive Application Guide

lqi007 2012-07-19 评分 0 浏览量 0 0 0 0 暂无简介 简介 举报

简介:本文档为《Adhesive Application Guidepdf》,可适用于工程科技领域,主题内容包含InnovativeEpoxyAdhesiveSolutionsforOverYearswwwepotekcomepoxyAdhesiveAppli符等。

InnovativeEpoxyAdhesiveSolutionsforOverYearswwwepotekcomepoxyAdhesiveApplicationGuideThisguideisaneducationaltooldesignedtoassistadhesiveusersingainingamorethoroughunderstandingofadhesivepropertiesandtestingItwascompiledthroughthecombinedeffortsofmultipledepartmentsinEpoxyTechnology,Incincluding:QualityControl,ResearchandDevelopment,TechnicalServices,SpecialFormulatingServices,ProcessControlandTechnicalSalesandMarketingAlthoughwehavebasedourinformationonthemostuptodatedataandtestingavailable,advancesintestmethodsandmaterialsareconstantlyevolvingPleaseusethisreferencepieceasaguideonlyandbesuretofollowtherecommendationslistedondatasheetsaswellasanyadditionaltechnicalinformationincludedwithyouradhesiveproductshipmentWehopethattheinformationcontainedwithinthisguideisusefulandvaluabletoyouinchoosingthebestadhesiveforyourspecificapplicationForanyadditionalassistanceneeded,pleasecontactourApplicationsExpertsatEpoxyTechnologyattechservepotekcomor()InnovativeEpoxyAdhesiveSolutionsforOverYearsTableOfContentswwwepotekcompageTableOfContentsViscosityRheologyPotLifeandWorkingLifeAdhesiveCuringKineticsofCureGlassTransitionTemperature(Tg)ThermogravimetricAnalysis(TGA)DegradationTemperatureOutgassingLapShearandDieShearLapShearDieShearDynamicMechanicalAnalysis(DMA)ThermomechanicalAnalysis(TMA)ElectricalConductivity(VolumeResistivity)ThermalConductivityViscosityRheologypageVVAAFdvdxViscosityisatermandvalueusedtodescribetheinternalfrictionofafluidThedegreeoffrictionisobservedwhenaforceisappliedtothematerialThemorefrictiondetected,themoreforcerequiredtomovethematerialorto"shear"itShearingoccurswhenthefluidisactuallymovedAlowviscosityproductlikewaterrequireslessforcetoflowthanahighviscositymaterial,likepeanutbutterTheforcerequiredtoshearamaterialcanbemeasuredandreportedusingaBrookfieldViscometerOnetypeisaconeandplateviscometershowninfigureTheconeandplateviscometerpreciselymeasuresthetorqueestablishedbytheresistanceinafluid,sandwichedbetweenarotatingconeandstationaryplateAstorqueisdirectlyproportionaltotheshearstressinthematerial,itcaneasilybeconvertedtoabsolutecentipoise(mPas)unitsthroughknowngeometricconstantsofthecone,therateofrotation,andthestressrelatedtorque(orfromprecalculatedrangecharts)Theplateportionoftheassemblyisthesamplecup(showninfigure)whichholdsthefluidandremainsstationaryItisjacketedsothataconstanttemperatureismaintainedthroughoutthetestThecupislockedontotheviscometersothatthematerialcomesintocontactwiththeconeNewtondefinedviscositybythemodelinfigurebelowTwoparallelplanesoffluidofequalarea"A"areseparatedbyadistance"dx",movinginthesamedirection,butatdifferentvelocities(VandV)HeassumedthattheforcetomaintainthisdifferenceinspeedwasproportionaltothedifferenceinspeedthroughouttheliquidAlsocalledthevelocitygradientToexpressthis,Newtonsaidthat"η"isaconstantforagivenmaterialandiscalledits"viscosity"Thevelocitygradient,dvdx,isameasureofthechangeinspeedatwhichthelayersmovewithrespecttooneanotherThisdescribestheshearingaliquidgoesthroughandisreferredtoasthe"shearrate(S)"whichisreportedin"reciprocalsecond"(sec)ThetermFAindicatestheforceperunitarearequiredtoproducetheshearingactionItisreferredtoas"shearstress"andwillbesymbolizedby"F"Itsunitofmeasurementis"dynespersquarecentimeter"(dynescm)figurefigureViscosityRheologyViscosityRheologywwwepotekcompageUsingthesesimplifiedterms,viscositymaybedefinedmathematicallybythisformula:ASTMTestMethodD,"StandardTestMethodforHighShearViscosityUsingaConeandPlateViscometer",isbasedontheabovedefinitionandisfollowedforviscositymeasurementsThefundamentalunitofviscosityisthe"poise"Ifamaterialrequiresashearstressofonedynepersquarecentimetertoproduceashearrateofonereciprocalsecond,itwouldproduceaviscosityofonepoise,orcentipoiseViscositycanalsobeexpressedin"milliPascalseconds"(mPas)OnemilliPascalsecondisequaltoonecentipoiseNewtonassumedthatallmaterialshave,atagiventemperature,aviscositythatisindependentoftheshearrateInotherwords,twicetheforcewouldmovethefluidtwiceasfastThisholdstrueforNewtonianfluidsonlyThefollowingisaschematic(figure)ofaconeandplateviscometerinaction:ThetypeofflowdescribedaboveistrueforNewtonianfluidsonlyThefollowinggraphsshowhowthistypeofproductbehavesFigureshowsthestraightlinerelationshipbetweenshearrate(F)andshearstress(S)Figureshowshowtheviscosityremainsconstant(assumingtemperatureisheldconstant)withvaryingshearratesfigurefigurefigureη=Viscosity=FS=shearstressshearrateButnotallfluidsareNewtonianintheirflowcharacteristicsInfact,thereareseveraltypesofflowbehaviorTheseproductsareclassifiedasNonNewtonianTherearethreesubgroupswithintheNonNewtonianclassification:Pseudoplastic,DilatentandPlasticViscosityRheologypagePseudoplasticmaterialswilldecreaseinviscositywithanincreaseinshearrateThisissometimesreferredtoasshearthinningFiguresdepictthis:ADilatenttypeofbehaviorasseeninfiguresandbelow,causesproductstoincreaseinviscositywithanincreasingshearrateThisisalsocalledshearthickeningandiscommonlyseenwithdeflocculatedsolidssuchasclayThethirdandfinaltypeofflowisPlasticWhenamaterialexhibitsPlasticbehaviorsimilartofiguresandbelow,itwillremainina"solid"stateuntilacertainamountofforce(yieldvalue)isappliedtoitbeforeitwillflowAgreatexampleofthisisketchupfigurefigurefigurefigurefigurefigureViscosityRheologywwwepotekcompageEpoxiescanexhibitanyoralloftheseflowbehaviorswhichisimportanttoconsiderwhenchoosinganadhesiveforaspecificapplicationThixotropyisanotherparameterthatisrelatedtoviscosityandcanbemeasuredusingaviscometerAthixotropicfluiddecreasesinviscositywithtime,whileitissubjectedtoconstantshearingasseeninfigureThistypeofbehaviorcanoccurincombinationwithanyoftheaboveflowtypesfigurefigureWhentalkingthixotropy,oftenwerefertoThixotropicIndex(TI)ThisisavaluereportedbytakingtheratiooftwoseparatereadingsatdifferentspeedsonaviscometerForexample,ifamaterialproducesareadingof,cPsatRPMand,cPsatRPM,thethixotropicindexisequalto,,orUsually,TIiscalculatedfromviscositiesmeasuredatRPMsthatareadecadeapart(iebetweenandRPMsorbetweenandRPMs)ThisnumberisalsokeyinchoosingthepropertypeofmaterialforaparticulardispensingtechniqueAlloftheprecedingterminologyanddefinitionsarealso"rheologicalparameters"RheologyisdefinedasthescienceofthedeformationandflowbehaviorofmaterialsFlowbehaviorisimportantinmanyindustrialprocessesandthesuccessorfailureofanapplicationiswidelybasedonthesepropertiesforaspecificadhesiveCoatings,moldedplastics,adhesives,personalcareitems,cosmetics,inks,cement,solderpastesandmedicinesareexamplesoftherangeofcommerciallyavailableproductswhoseviabilitydependsonhavingtheproperrheologyForalloftheabovematerials,thenecessaryrheologicalpropertiesmustbeexaminedbeforeprocessingandapplicationThefollowinggraph(figure)showshowausermaywanttobalanceviscosityandthixotropyinordertodeterminethebestapplicationmethodforagivenadhesive:PotLifeandWorkingLifepagePotlifeisametricusedtodefinethelengthoftimethatamaterialcanbehandledbeforeitsviscositychangessubstantiallyGenerally,potlifeisdefinedastheamountoftimeittakesfortheinitialviscositytodoubleFigurebelowshowstheincreaseinviscosityovertimeforatypicallowtemperaturecureepoxysystemYouwillnoticethattheviscositybuildsslowlyatfirstasthechemicalreactionbeginsHowever,thereactionitselfgivesoffheatwhich,inturn,increasestherateofreactionThisprocesscausestheviscositytoincreaseinanexponentialmannerOften,knowingthepotlifealone,isnotsufficienttodeterminehowlongagivenmaterialcanbeusedforagivenmanufacturingprocessForexample,figureshowsthenormalized(change)viscosityversustimefortwodifferentproductsBoththeblueandgreenproductsexhibitthesamepercentchangeinviscosityversustimeSincebothformulationsdoubletheirviscosityafterhours(shownasachange),theybothwouldhavehoursofpotlifeAsshowninfigure,thismaterialhasabouthoursofpotlife,ieittakesthreehoursbeforetheviscositydoubles(change)figurefigurePotLifeandWorkingLifePotLifeandWorkingLifepagewwwepotekcomHowever,asfigureshows,thetwomaterialshaveverydifferentstartingviscosityvaluesThestartingviscosityofthegreenmaterialistentimesgreaterthanthatofthebluematerialAsaresult,themagnitudeofviscositychangeoveragivenperiodoftimeforthegreenproductismuchhigherthantheblueproductInthesecases,theprocesslimitsforaspecificapplicationshouldbeusedtodefinetheworkingtimeforagivenmaterialinagivenprocessIntheexampleabove,customerAmaybeabletoworkwiththebluematerialaslongastheviscosityislowerthan,cPsThiswouldgivecustomerA,hoursofworkinglife(hourslongerthanthepotlife)Ontheotherhand,customerBmayonlybeabletoworkwiththegreenmaterialiftheviscosityislessthan,cPsInthiscase,thematerialwouldhaveaworkinglifeofonlyhoursincustomerB’sprocessThus,potlifeisadatasheetvaluedesignedtogiveafirstorderdescriptionofthespeedofviscosityincreaseovertimeHowever,theactualworkingtimeoftheproductwillbeapplicationspecificandshouldbedeterminedanddefinedbasedontheindividualprocessfigurefigureAdhesiveCuringpageThewordpolymercomesfromtheGreekwordspoly(meaningmany)andmeros(meaningparts)Assuch,polymersarelongmoleculechainscomposedofmanythousandsofsmallunits(monomers)joinedendtoendAnexampleoflinearpolyethylene,thesimplesthydrocarbonpolymer,isshowninfigure:PolymersfallintotwomaincategoriesthermoplasticsandthermosetsThermoplasticmaterialsaregenerallycomposedoflinearpolymerchainswithlittleornobranchingorsidegroupssimilartothethermoplasticpolyethylenepolymerinthediagramaboveAsaresult,thesechainsareabletoeasilyslidepasteachotherwhenheatedInthisway,thermoplasticscanbeheatedandformed,thenreheatedandreformedrepeatedlywithoutdamageOntheotherhand,thermosetsundergoachemicalreactionwheninitiallyheatedandcuredtoformathreedimensionalcrosslinkednetworkOncethesematerialsarecured,thisstructureislockedinplaceandthematerialcannotbereformedorreprocessedAnexampleofthechemicalcrosslinkstructureforacommontypeofthermosettingpolymer,anepoxy,isshowninfigurefigureAdhesiveCuringAdhesiveCuringpagewwwepotekcomfigureEpoxiesgettheirnamefromthethreemembered"epoxide"ringslocatedonthestartingepoxidemonomerInthecaseabove,thestartingmonomerisactuallyadiepoxide,whichcontainstwoepoxidegroupsoneateachendofthemonomerThehardenerintheabovesystemisadiamine,whichcontainsareactiveaminegroupateitherendofthemoleculeEachoftheepoxideringscanbeopenedbyanactivehydrogenontheendofthediaminetoproducechemicalbondsbetweentheepoxidemonomerandthehardenerThisparticulardiaminehardenerprovidesfouractivehydrogensthatarecapableofreactingwithfourdifferentepoxidemonomerstochemicallycrosslinkthemtogetherTypically,thehigherthefunctionality(numberofreactivesites)ofthehardener,themoretightlycrosslinkedtheresultingcuredthermosetwillbeIngeneral,highlycrosslinkedsystemswillhavehigherhardnessandmorethermal,chemicalandmoistureresistanceAdhesiveCuringpageKineticsofCureThecurekineticsrateforthermosettingadhesivescanbemonitoredusingDifferentialScanningCalorimetry(DSC)DSCmeasurestheenergyabsorptionofasampleasitissubjectedtoaspecifiedthermalprofileTheamountofheatcontainedinamaterialatanygiventimeisknownasitsenthalpyAsadditionalthermalenergyissuppliedtothematerial,itsenthalpywillincreaseTheleveloftheresultingtemperaturechangeinthismaterialwillbedictatedbyitsspecificheatAtagiventemperature,specificheatistheamountofthermalenergyneededtochangethetemperatureofthatmaterialbyoneunitFigurebelowshowsthecrosssectionofatypicalDSCsampleholderAsmallamountofuncuredsample(~mgofresincontent)isplacedinasmallaluminumsamplepanwithlidThesamplepanisplacedontopofanindividualchromelheatingdiscAnidenticalemptyaluminumpanisplacedonasecondchromelheatingdisctoserveasareferencefortheexperimentEnergyissuppliedseparatelytothesamplepanandthereferencepaninorderforeachofthemtoexactlymatchtheheatingrateofapredeterminedtemperatureprofileTherateofenergysuppliedtothesampletoheatitatacontrolledrateisproportionaltothespecificheatofthesampleThespecificheatofamaterialwillchangeonlyslightlywithtemperatureaslongasthatmaterialremainsinthesamephysicalstateHowever,whenthethermalprofileimposedonamaterialcausesatransitiontoanewstate,(iemelting,decomposition,curing,etc)thiswillcauseasignificantchangeinthespecificheatTherapidchangeinspecificheatatatransition,thencausesachangeintheamountofenergyneededtobedeliveredtothesampleinordertomaintainthedesiredheatingorcoolingprofileDynamicSamplerChamberReferencePanSamplerPanLidGasPurgeInletChromelDiscChromelDiscThermocoupleJunctionAlumelWireHeatingBlockChromelWireThermoelectricDisc(Constantan)StandardDSCCell*figure*CourtesyofTAInstrumentsAdhesiveCuringpagewwwepotekcomChangesinstatethatabsorbenergyareknownasendothermicchangesMeltingisanexampleofanendothermicstatechangeHeatisputintothesystemtoallowmoleculesthemobilitytobegintomoveEventually,enoughheatisputintothesystemtocauseoverallflowofthemeltedmaterialAtthispoint,theheatenergybecomesconvertedtothekineticenergyoftheliquidOntheotherhand,changesinstatethatactuallyevolveenergyareexothermictransitionsHeatofreaction(curing)andcrystallizationareexamplesofexothermictransitionsFigureshowssometypicalendothermicandexothermictransitionsastheywouldappearinaDSCscanAsmentionedearlierinthissection,DSCcanbeusedtomonitorthecureofathermosettingmaterialThisisaccomplishedbysubjectingtheuncuredthermosettoacontrolledtemperaturerampandanalyzingthelocation,sizeandshapeoftheresultingexothermiccurepeakFigureshowsaDSCkineticcuringprofileforatypicalepoxysystemThepeakinthesample’sheatflowresponseislocatedabovethebaseline,representinganexothermiceventThepeakofthiscuringexothermislocatedatapproximatelyC,indicatingthatthefastestcureforthisproductwilloccuratthistemperatureTheonsetofthecurepeakforthisproductisCfigureAdhesiveCuringpageHowever,thisdoesnotmeanthattheproductcannotcurebelowCAstheenlargedportionofthekineticcurvereveals,thereisactuallyasmallamountofexothermstartingaslowasCThisparticularproductwillcureatC,butitwilltakearoundfourhoursOntheotherhand,whenthisproductiscuredatC,thepeakcuretemperature,itwillonlytakeaboutminutesThetotalchangeinenthalpythatthesampleundergoesduringcurecanbecalculatedbyintegratingtheareaundertheexothermpeakForthematerialinthediagramabove,thetotalheatofreactionisJgAsspecifiedinASTMD,"StandardTestMethodforTransitionTemperaturesandEnthalpiesofFusionandCrystallizationofPolymersbyDifferentialScanningCalorimetry",thistotalheatofreactioncanthenbeusedtodeterminetheextentofreactionofthematerialafteritiscuredaccordingtoadesiredcureconditionThecuredmaterialisanalyzedintheDSCusingthesamethermalprofileusedtomeasuretheuncuredmaterialFigureshowstheoriginalexothermoftheuncuredmaterialabove,alongwiththatofthesamematerialcuredatCforminutesfigureAdhesiveCuringpagewwwepotekcomThematerialcuredatCforminutesexhibitsonlyaverysmallresidualexothermpeakThisindicatesthatmostofthetheoreticalcrosslinkingreactionswerecompletedduringthecureTheenlargedviewofthecuredsampleexothermshowsthatonlyJgofreactivityremainsoftheoriginalJgheatofreactionforthismaterialThus,onlyofthematerialisleftunreactedbytheimposedcureEpoxiesdonotneedtoachieveafullreactioninordertoperformwellasadhesivesGenerally,systemsthathavebeencuredtoatleastconversionwillexhibitmechanicalandphysicalpropertiesthatdo

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