aging and durability of high temperature electrical insulation

8/2/2019 Aging and Durability of High Temperature Electrical Insulation

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AGINGANDDURABILITY OFHIGHTEMPERATURE ELECTRICAL INSULATION GRANTNO.F496209510396

1SEPT1995-31AUGUST1999FINALREPORT

PROJECTMANAGER RINCIPALINVESTIGATOR DR.CHARLESY-CLEE LARENCE JWOLFAfOSR ASHINGTONUNIVERSITY

DTICQUALITYINSPECTED3 2 0 0 0 0 4 2 80 4 5


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REPORTDOCUMENTATIONPAGEPublicreportingburdenforthiscollectionofinformationsestimatedtoaverage ou rpe rresponse,n < gatheringandmaintainingthedataneeded,andcompletingandeviewingthecollectionofinformation,collectionofinformation,ncludingsuggestionsorreducingthisburden,oWashingtonHeadquartersSe DavisHighway,Suite1204,Arlington,VA2202-4302,and totheOfficeofManagementand Budget,

AFRL-SR-BL-TR-00- sourcesitofthiSefferso

1.GENCYUSEONLY(Leaveblank) 2. REPORTDATE 3. REPORTTYPEANDDATESCOVERED FINAL01 SE P95-31 AUG99 4.ITLEANDSUBTITLE AGING AND DURABILITY OFHIGHTEMPERATURE ELECTRICALINSULATION 6.UTHOR(S)ClarenceJWolf7. PERFORMINGORGANIZATIONNAME(S)ANDADDRESS(ES)Washington UniversityStLouisMO

9. SPONSORING/MONITORINGAGENCYNAME(S)AND ADDRESS(ES)AFOSR/NL 801 NRandolph St.,Rm 73 2ArlingtonVA2203 -1977

5. FUNDINGNUMBERS F49620-95-1-0396

8.PERFORMINGORGANIZAT IONREPORTNUMBER F49620-95-1-0396

10.SPONSORING/MONITORING AGENCYREPORTNUMBER

11.SUPPLEMENTARYNOTES

12a.DISTRIBUTIONAVAILABILITYSTATEMENT Approvedfo rpublicrelease;Distributionunlimited 12b.DISTRIBUT IONCODE

13.ABSTRACT (Maximum200words)Th eobjectivesofthisprogramaretoinvestigatethelong-termaging processeswhichoccurin typicalhightemperature polymericsystems. The primarysystemofinterestisirradiatedethylene tetrafluorethylene(ETFE)coatedoversilverplatedcopper.he tw ospecificgoalsof thisresearchare:1)To determinethermaloxidativedegradationofahightemperaure polymersuchasETFEin th epresenceofmetalsurfaces,and(2)To determinetheeffectof thepolymeron theoverallstabilityandmorphology ofthemetalsurface.heineticsofth eETFEdegradationprocessasafunction ofradiationdose(usedto cross-linkthepolymer,therebyenhancingits mechanicalroperties),temperatureandcatalyticmetasurfacewerestudiesby severaldifferentthermaloxidativemethods.ineticparameters,temperaturecoefficients(i.e.,activationenergies),anddegradationratesasafunctionoftemperature,radiationdose,andcatalyticsurfaceswereinvestigated.nalyticalprocedureswereusedto determinethemostaccurateandreproduciblemethodfo rkineticanalysis.Th ediffusionandsubsequentsurfacereactionsofcopperthroughathinsilverplate(silverplatedcopperconductor)werestudiedby scanningAugerelectronandopticalspectroscopies.he kineticsofth ecopperdiffusionareevaluatedin ordertocorrelatehangesin thepolymerdegradationreactionswiththechangein surfacechemistryandmorphologyofthemetal.Theinitialsilversurfaceslowlychangestoan oxidized coppersurfaceofth egeneralstochiometryCu27 oasth ecopperdiffusesthrough th esilverlayer.The diffusionismorerapidandth ecoppersurfacelayeristhickerwhentheconductoriscoveredwithpolymer.nthiscaseth eratioofcoppertooxygenatth esurfaceisapproximatley3 :1 .hesolubilityof14.SUBJECTTERMS

17.SECURITYCLASSIFICATION OF REPORTUNCLASS

18.SECURITYCLASSIFICATION OFTHISPAGE UNCLASS

19.SECURITYCLASSIFICATION OFABSTRACT UNCLASS

15.NUMBEROFPAGES 5416.PRICECODE

20 .LIMITATION OF ABSTRACT StandardForm298(Rev.2-89)EGPrescribedbyANSIStd.239.18DesignedusingPerformPro,WHS/DIOR,O ct9


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AgingandDurabilityofHighTemperatureElectricalInsulation GrantN o " .F496209510396(lSept1995-31Aug1999)ProjectManagerDr.CharlesY-C Lee

AFOSR ClarenceJ.WolfWashingtonUniversitySt.Louis,Mo

ExecutiveSummaryTheobjectivesof thisprogramarctoinvestigatethelong-term agingprocesses

whichoccurintypicalhightemperaturepolymericsystems.Theprimarysystemofinterestisirradiatedethylenetetrafluorethylene(ETFE)coatedoversilverplatedcopper. Thetwospecificgoalsofthisresearcharc:odeterminethermaloxidativedegradationofahightemperaturepolymersuchas

LTFEinthepresenceofmetalsurfaces,andodeterminetheeffectofthepolymerontheoverallstabilityandmorphologyofthemetalsurface.ThekineticsoftheETFEdegradationprocessasafunctionofradiationdose(usedtocroN-hnkthepolymer,therebyenhancingitsmechanicalproperties),temperatureandeat.ilvtiemetalsurfacewerestudiedbyseveraldifferentthermaloxidativemethods.Kineticparameters,temperaturecoefficients(i.e.activationenergies),anddegradationratesasafunctionoftemperature,radiationdose,andcatalyticsurfaceswereinvestigated.nalyticalprocedureswereusedtodeterminethemostaccurateandreproduciblemethodforkineticanalysis.


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Thediffusionandsubsequentsurfacereactionsofcopperthroughathinsilverplate(silverplatedcopperconductor)werestudiedbyscanningAugerelectronandopticalspectroscopies.hekineticsofthecopperdiffusionare evaluatedinorderto correlatechangesinthepolymerdegradationreactionswiththechangeinsurfacechemistryandmorphologyofthemetal.heinitialsilversurfaceslowlychangestoanoxidizedcoppersurfaceof thegeneralstochiometryCu270asthecopperdiffusesthroughthesilverlayer.he diffusionismorerapidandthecoppersurfacelayeristhickerwhentheconductoriscoveredwithpolymer.nthiscasetheratioofcoppertooxygenatthesurfaceisapproximately3:1.

Thesolubilityoforganicfluids,carbondisulfideandtolueneintoanothermodelsyMcm.polyphenylenesulfide,wasinvestigated.he effectoftemperature,morphology ar.Jpre-sorptionannealingonthetransportprocesswasstudied.


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AppendixI:upportPersonnelGraduateStudents JonathanEldersDeptofChemicalEngineeringWashingtonUniversity St.Louis,MO3 1 3 0

ChrisLong DeptofChemicalEngineeringWashingtonUniversity St.Louis,MO3 1 3 0OtherResearchers

1 .DanWaddillProfessorDeptofPhysicsandMaterialsScienceUniversityofMissouri-RollaRolla,MO 2.eanMcKinney DepartmentofMaterialSciences University ofMissouri-RollaRolla,MO 3 .ernieSunierDepartmentof MaterialSciences WashingtonUniversity'o'4.ngelaAiduck(Graduated)DepartmentofMaterialSciencesWashingtonUniversitySt.Louis,MO31 30 5.nriqueFarfun(Graduated)DepartmentofChemicalEngineeringWashingtonUniversity St.Loufs.MO3 1 3 0 5.ynthiaChew DepartmentofChemicalEngineeringWashingtonUniversitySt.Louis,MO3 1 3 0


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6.cottHager(Graduated)DepartmentofChemicalEngineeringWashingtonUniversity St.Louis,MO3 1 3 0


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AppendixII:ublications1 .C.J.Wolf,HJ.Brandon,V.L.Young,K.U.JerinaandA.P.Srivastave,"Chemical,PhysicalandMechanicalAnalysisofExplantedBreastImplants,"ImmunologyofSilicones,M.PotterandN.R.RoseEds.,SpringerVerlag,New York,1996,p25 .2.Wolf CJ ,BrandonJH ,JerinaKL,YoungVL .Long-Term AgingofImplantedSilicone/SilicaCompositeBreastImplants."roceeding,EleventhInternationalConferenceonCompositeMaterials,GoldCoast,Queensland,Australia:d.M.L.Murray,p467(1998).3 .Thermo-OxidativeDegradationofEthylene-Tetrofluorethylene,"J.P.Elders andCJ.Wolf,3 rdNationalGraduateResearchPolymerconference,21-24June199S,UniversityofAkronPolymerchemistryDivision(ACS),pp9-15 .4. .J .Brandon,CJ.Wolf,V.L.YoungandK.L.Jerina.EffectofSurgicalImplantationontheLocalShellPropertiesofSILASTICIISiliconeGelBreastImplants,"J.Biomatl.Sei.(Polym.Ed.)inpress.5.randon,HJ,Peters,W.,Young,V.L,Jerina,K.L.,Wolf,C.J.,andM.W.Schorr,"AnalysisofTwoD ow CorningBreastImplantsRemovedAfter28 YearsofImplantation,"AestheticSurgery,Jan/Feb,1999.6.randon,HJ,Young,V.L,Jerina,K.L.andWolf,CJ,"EffectofImplantationSurgeryon theAverageStrengthPropertiesofSiliconeGelBreastImplants,"AestheticSurgery,May/June,1999.7.Brandon.HJ.Jerina,K.L.,Wolf,CJ,andYoung,V.L,"UltimateStrength PropertiesofControlandExplantedSILASTICeO andSILASTIC*!SiliconeGel-FilledBreastImplantShells,"AestheticSurgeryJournal,Sept/Oct.,1999.

tN Brandon.HJ,Jerina,K.L.,Wolf,CJ,andYoung.V.L,"UltimateStrength Propertiesof ControlandExplantedSILASTIC^IISiliconeGelBreastImplantShells"AestheticSurgery Journal,Mar./Apr.2000 .9.randon,HJ,Young,V.L,Jerina,K.L.andWolf,CJ,"SEMCharacterizationofSurgicalInstrumentDamagetoBreastImplants,"SubmittedtoPlasticand

ReconstructiveSurgery.

BookReviewsforACS(AppearinJACS)1 .Resinsfo rCoatings:hemistry,PropertiesandApplications. .StyeandW.Frectay(Hanser-Gardner:incinnati,1996).


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2.HydrocarbonResins,R.Mildenberg,G.CollinandM.Zander(Wiley-VXH;New York1997).Publicationsupportedby AFOSF

1 .nvironmentaltressDeformationfolyethertheretone), .P .Srivastour,N.Depke,andC.J.Wolf,.ofAppl.Polym.Sei.66725-731(1997).2.Thermo-OxidativeDegradationofIrradiatedEthyleneTetrafluorethylenes,inOxidativeBehaviorofMaterialsinThermalAnalyticalTechniques,Eds.A.T.RigaandG.H.PattersonSTP1326ASTM,1997pp .116-127.3 .orptionTolueneintoLow TemperatureAnnotatedPolyphenyleneSulfide,Mo.J.UndergradChem.Res.745-55(1998/1999).4..J.WolfandC.Chew.SorptionofTolueneinPolyphenyleneSulfide

(PPS),"J.Polym.Sei.(Phys.Ed.)(submitted). 5..J .Wolf.SorptionofCarbonDisulfideinPolyphenyleneSulfide(PPS),"J.Polym.Sei.(Phys.Ed.)submitted.)


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AsingandDurabilityof HighTemperatureElectricalInsulationGrantN o " .F496209510396(lSept1995-31Aug1999)FinalReport

ClarenceJ.WolfWashingtonUniversity St.Louis,Mo

1 .0 SummaryTheprimaryobjectivesofthisprogramaretodeterminethelong-term aging

processeswhichoccurintypicalhightemperaturepolymericsystems.Ofparticularinterestisadeterminationofthefactorswhichcontrolthelong-termdurabilityofelectricalinsulationsystems.naseparate,bu trelatedseriesofexperiments,wehaveshownthattheprimarymodeoffailureoffluorinatedthermoplasticco-polymersusedaselect! icalinsulationisstresscracking.urthermore,wehaveobservedthatthecracksc;i:ibedirectlycorrelatedwiththethermaldegradationoftheinsulation. therpolymers exhibita differentcriticalmodeoffailure,forexamplethepolyimide,pp'diphenyleneo\uiepvromellitimide(commerciallysoldbyDuPontasKapton")crackswhenstressed inthepresenceofwater,i.e.stresshydrolysis.1)Theparticularsystemofinterestinthiss:ud>sirradiatedethylenctetrafluoroethylene(ETFE)oversilverplatedcopper.Thetwospecificgoalsofthisresearchare:odeterminethermaloxidativedegradationmechanismofhightemperaturepolymer

suchasETFEinthepresenceofmetalsurfaces,andodeterminetheeffectofthepolymerontheoverallstabilityandmorphologyofthe

metalsurface.


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ThekineticsoftheETFEdegradationprocessasafunctionofradiationdose(cross-linkedpolymer),temperatureandcatalyticmetalsurfacewerestudiedbyseveraldifferentmethods. ineticparameters,temperaturecoefficients(i.e.activationenergies),anddegradationratesasafunctionoftemperature,radiationdose,andcatalyticsurfaceswereinvestigated. combinationof physicalanalyticalmethods,including'ATR-FTIR,TGA,DSC,andGC/MSwereusedtostudythepolymer.

The effectofthepolymeronthemetalsurfacesandthesubsequentsurfacereactionsofcopperthroughathinsilverplate(silverplatedcopper)werestudiedby scanningAugerandscanningelectronmicroscopy(SEM).heinitialsilversurfaceslowlychangestoanoxidizedcoppersurfaceofthegeneralstochiometryCu,70asthecopperdiffusesthroughthesilverlayer.henewsurfacelayerhasacatalyticeffectuponthedecompositionof theoverlayingpolymer.

Thediffusionandsolubilityof twopenetrants,carbondisulfideandtoluene,intopoi\phenvlenesulfide(PPS)wereinvestigated.PScompositeisatoughmaterialprj-ciulvusedinthenoseofcommercialaircraft.heeffectsoftemperature,nv.'rrhologv.andannealingonthetransportprocesswereinvestigated.hedatasuggestth.;:thevoids/channels(freevolume)formedduringsolventinducedcrystallizedare .sm.tiieiiian92.-Vbu tlargerthan49.Vandmaybetheratedeterminingfactorinthetrailspe:;process.


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2.0Introduction The useofpolymersandpolymericmaterialsincriticalcomponentsofboth

militaryandcommercialaerospacesystemsisexpandingrapidly.hesematerialshaveoutstandingphysicalandchemicalpropertiesandtheirfullpotentialhasno tbeenutilized.Oneofthemajorlimitationsofthesematerialsisalackofknowledgeabouttheirlong-termproperties(durability)inahostileenvironment.hus,thedeterminationsoftheirlifetime,or agingcharacteristics,isanareaofimmediateconcern.hepredictionoftheaeineprocessisparticularlydifficultfornewmaterialsdesignedfo rtheharshcomplexaerospaceenvironment.he highlevelofsophistication ofmodernaircraftrequiresadeepunderstandingoftheeffectsoftheenvironmentontheoperating system.neofthemajorareasofconcernistheelectricalsystem oftheaerospacevehicle.ecenttragedies su e costthatelectricalinsulationparticularlywithregardtocrackingandflaking,maybe theAchillesheeloffly-by-wireaircraft.

Theighlevelofsophisticationinmodernaircraftelectronicsystemsrequires ! . > : r _ 'termprotectionfromaharshoperatingenvironment.Modernaircraftrequiremilesoielectricalwiringtoconnectthevariousaircraftcomponents.orexample,smallerAirForceaircraft,suchastheF-15Eagleor F-16Falcon,requiremorethan100,000 feet130.00'.in)ofelectricalwiring.uetothetightdemandsonspace,weight,energyandmaintenancecostinaircraftofthishighdegreeofsophistication,theinsulationmustbe lightweight,haveexcellentdielectricproperties,andmustmaintainthermalstabilityathightemperaturesfo ralongperiodoftime.

Inadditiontothehightemperaturerequirements,thewiresystemmustremain flexibleatalloperating conditions.sageneralclassofcompounds,thermoplastic


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resinsexhibitmanydesirableproperties,andonesuchresinsystem,irradiatedethylenetetrafluoroethyleneispresentlybeingextensively usedinaerospacewiring systems.hisisanextremelycomplexsystem,consistingofasemi-crystallinethermoplasticresinwhichisirradiatedwithhigh-energyelectionstoenhanceits mechanicalproperties;inadditionitcontainsseveraladditivestominimizeoxidationandmaximizeflameresistance.hiscomplexsystemisplacedindirectcontactwithan activemetal,theconductor(silvercoatedcopper),andmaintainedatelevated temperatureforlongperiodsof time.erospacewiringsystemshaveadesigngoalof10.000hoursat200C!heagingofawiresystemisacomplexphenomenoninwhichanorganicpolymerisindirectcontactwithametalsurface,theconductor.Manyelectronicsystemswhichutilizecircuitboardsencounterasimilarproblem,i.e.organicpolymerincontactwithanactivemetalsurfacefo ranextendedtimeperiodatelevated temperature.

TheETFEsystemisofparticularinterestfortworeasons:1 )itcomprisesthebasicpartofthenew,so-called"hybrid,"insulationofuseon

mainmodernAirForceandNavyaircraft,and2)itisasemi-crystallinethermoplasticresinsystem whichiscross-linkedby

electronirradiation.Therefore,wehavematerialwhichhasgreatpracticaluse,a"hightemperature,"semi-cry.stalline,cross-linkedthermoplasticindirectcontactwithasilver/coppermetalsurface.

SinceETFEisasemi-crystallinethermoplasticsresin,weextendedou rstudiestoanotherthermoplasticpolymer,i.e.polyphenylenesulfide,PPS.PSisalsoconsideredahighperformancethermoplasticresinwhichhasphysicalpropertiessimilarto


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polyetheretherketone(PEEK).nfactPPScomposite(E-glassfibers)isacandidatefo rus eonthenoseoftheAirbusIndustriesA-340commercialjet.hemelting pointof PPSisapproximately285CanditsTisapproximately85C.PS ,likePEEK,canbe obtainedineithertheamorphousor semi-crystalline stateandexhibitssolventinduced crystallization inthepresenceofawidevarietyof solvents.Wewereparticularlyinterestedinthetransportpropertiesoftheorganicfluids,tolueneandcarbondisulfide,intoPPS.reasofparticularconcernwere )solubility,2)ratesofsorption,3 )desorption,4)diffusioncoefficient,5)solventinducedcrystallinity,and6)thermaltreatment(annealing)priortosorption. ProgramObjectives:heoverallobjectiveofthisprogramwastodevelopabasicunderstandingofthefactorswhichdeterminethelong-termstability,i.e.durability,ofhighperformancethermoplasticresinsystems.he programcanbeconvenientlydividedi.r.otwospecificprojects:

1 )Todeterminethelong-termeffects,i.e.durability,ontheoverallpropertiesofacomplexthermoplasticresinsystemincontactwithanactivemetalsurface,andto^onsiJcrtheeffectof eachofthemanyprocessingvariablesonthestabilityofthismaterial:and

2)Characterizethetransportpropertiesoforganicliquidswhosecharacteristics representthoseencounteredinaharshairspaceenvironmentintoatypicalsemi-crystallinethermoplasticresin.

Oneofthemoreimportantaspectsofthisprogramisconcernedwiththepracticalquestion:hatistheeffectof eachcomponentofasystemonthedurabilityoftheothercomponents.hisaspectofthegeneralquestionofmaterialdurabilityisusually


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neglected.Mostelectronicsystemsusedinhighperformancesystemsconsistofintegratedcircuitsinwhichthevariouscomponentsarefabricateddirectlyontoacircuitboard.ormallythecircuitboardisanorganicfilm,suchasanepoxyorpolyimide.he long-termstabilityandoverallsynergisticeffectofthevariouscomponentsoneachotherisofdirect-relevancetothisstudy.


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3 .0 ExperimentalTheterminologyusedinthisreportconcerningthedurabilityoftheelectrical

insulationisasfollows:olymerandinsulationareusedinterchangeablyasthecoatingoverametalor conductor

onductorissilverplatedcopperetalreferstothebasemetalirereferstoaconductorcoatedwithinsulation.

Materials:heETFEwascommercialgradepolymercontainingapproximately2. 5 ;c;riallvlisocyanurate(TIAC)cross-linkingagent.he conductorwasextrusion coatedwithpolymertoformthewireandi twasirradiatedwith .5MeV electronstoMvjicddoses.henominalconductorwas19-strandsilver-platedcopper.achstrandi s(1.15mmindiameter,platedwithasilverlayer5x105cmthick.hedatais^.:mmari"/edinTable .

Samplesof0.25mmthickfilmsof amorphousPPS(


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timesandaweightlossversustimecurvewasestablishedfo rallwiresandinsulation. Theambientatmosphereislimitedtoair.Thermogravimetricanalysis(TGA):ThermalAnalysis TA-2950 TGAequippedwithanautomaticsampleinletwasusedforallTGAanalysis.heanalyseswereconductedineitherair,nitrogenoroxygenataflowrateof 60 cmVmin.sothermal,dynamic,and"thermaljump"methodswereusedtoevaluatedegradationrates.achmethoddeterminesdifferentcomponentsof thekinetics"puzzle",includingactivationenergy(whichproperlyshouldbecalledtemperaturecoefficient),rate,order,andmechanism.ynamicTGAcanbeusedasamulti-experimentalmethodtodetermineactivationenergies,asshownbyFlynnandWall(2).amplesaredegradedataseriesofhcatin rates,andineachexperiment,thetemperaturetoreachadesignatedconversionisrecorded.heheatingrateisplottedagainsttheinverseofthattemperaturetofindtheactivationenergy.nthe"thermaljump"method,thetemperatureis"jumped"from TltuT2ataspecifiedconversion;thusratescanbemeasuredattwotemperaturesatthesam.jdecreeofconversionandtheactivationenergycanbedirectlyestimatedwiththeaidoftheArrheniusequation(3).acho{thesemethodshasitsownsetofadvantagesanddi.Nadvaiitages.nprinciple,the"jump"methodisidealtodetermineactivationciu-r_ic>.however,itisdifficulttouseatlowtemperatureswherethereactionratesarelov.andthesignal-to-noiscratioislow.ScanningAngerSpectroscopv:ugerelectronspectroscopyisananalyticaltechniquetodeterminetheelementalcompositionofthetopfewatomiclayersofasample'ssurface. PhysicalElectronicsModel545scanningAugermicroprobehousedatthePhysicsdepartmentattheUniversityofMissouri-Rollahasbeenusedfo rallexperiments.


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EveryelementproducesauniqueAugerspectrum.he entireanalysisisconductedinahighvacuumchamber.

AnadditionalfeatureoftheAugeranalysischamberistheabilitytocarefullyabradethesurfacebyargonionbombardment.hissputteringmethodremovessurfacematerial. sputterprofileinvolvesmonitoringtheAugerelectronsignalfromaf e w - selectedelementsasthesampleissputteredawaybytheargonionbeam,producinganelementalcompositionprofileasafunctionof depth.hesputteringrateusedinou rexperimentsvariedfrom19to50nm (190 to500)per minute.Thesputteringcanbe stoppedatanytimeduringtheprofilingandasurveyscanor elementmap acquired,theprofilingthenisresumed.Mappinginthisfashiongivesthree-dimensionalinformationaboutthesamplecomposition.C.nsChromntnaraphv-MassSpectrometrvfOC-MSI:aschromatographyisananalvticalmethodusedtoseparated componentsofacomplexmixture. Varian3600 CScasChromatographwithaSaturnGC/MS/MSdetectorhasbeenusedtoidentifyvolatileETFEdegradationproducts.hepolymerisdegradeddirectlyinaVarian ChronutoprobepyrolyzerattachedtotheGC/MS.reliminaryseparationisaccomplishedbyashort(3m)sectionofblankcolumnusedasaflowrestrictor.FluidSorption:ilmsapproximately60 x 6mmwereimmersedinthefluidofinterestcontainedin2. 5x5cm culturetubeswhichwereplacedinathermostatted aluminum block.tappropriateintervals,thesampleswereremovedfromtheculturetubes,blotteddrv,placedinataredweighing jar,weighedonadigitalelectricbalanceandreturnedtotheoveninlessthan5seconds.luiddesorptionwasaccomplishedby placingthesampleonawatchglassinanovenatthetemperatureofinterest.


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10

InfraredSpectroscopy.Rspectroscopywasusedtoexaminethesolidpolymerstoascertainwhatproductswereformedandwhatcompoundswerelostasafunctionofbothradiationandthermaldegradation.ouriertransformattenuatedtotalreflectanceinfrared(FT-ATR-IR)wasusedtoconducttheexperiments.heinstrumentwaslocatedattheMonsantoCo.ResearchlaboratoryinCreveCoeurMissouri.he polymerwasplacedon apolished silverstageunderamicroscopewithbothopticalandATRcapabilities.Normally,128scanswereusedtoformaspectra.TFEsamplesdegradedinboththepresenceandabsenceofconductorinairfortimeintervalsrangingfrom20to60 hoursattemperaturesbetween240and290Cwereanalyzedby FT-ATR.Crvstnllinitv/morphologv:hecrystallinitywasevaluated bydifferentialscanningcolorimetrv(DSC)inanitrogenatmosphereatascanrateof10C/mininaThermalAnalvsisDSC(TA2910ModulatedDSC).


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1 1

4.0ResultsandDiscussionAnin-depthinvestigationofthethermaldegradationofatypicalcommercial

polymer,suchasETFE,hasallofthecomplexitiesassociatedwithindustrialpolymers.Itisasemi-crystallinecopolymerprepared fromastoichromatric ratioofethyleneandtetrafluoroethylene,itcontainsananti-oxidant,andaflameretardantanditisirradiated withhigh-energyelectronsinthepresenceofa"promoter"to enhanceitshightemperaturemechanicalproperties.urthermore,inactualusethismaterialisindirectcontactwithanactivemetalsurfacewhosechemistrychangeswithtime.hisstudyusedacombinationofphysicalanalyticalmethodstodeterminethedegradationmechanismofthiscomplexmaterialinanenvironmentwhichsimulated itsactualuse.fthedegradationprocesscanbeaccuratelymeasuredandmodeled,thedurabilityor lifetimeotthepolymerincontactwiththeactivemetalcanbeestimated.

TheprimarymodeoffailureofthermoplasticelectricalinsulationarisesfromaK V N Snmechanicalproperties,leadingtocracking.heprimarycauseofcrackingiscmbrittiementoftheinsulationduetothermo-oxidativedegradation.heresearchwas concernedwiththreeaspectsof theoveralldegradationprocess:

egradationkineticsof ETFEpolymeregradationof ETFEinthepresenceof metalcatalyst,andhysicalandchemicalchangesinthecompositionoftheconductor.

Degradationof ETFE:hedegradationofETFEwasstudiedbyfourdifferentmethods:1 .isoihermally:nanaircirculatingovenattemperaturesbetween150Cand300C


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12

2.isothermallyistheTGAsystem(air,oxygen,or nitrogenatmosphere)attemperaturesbetween220Cand320C3 .dynamicallyintheTGAsystem(air,oxygen,ornitrogenatmosphere)atheatingratesbetween0.5 and20C/min,and4.intheTGAusingthekinetic-jumpmethodtooscillatebetweentemperatures,usuallybetween300Cand310C.Thesemethodscomplimenteachotherandprovided answerstodifferentportionsoftheETFEdegradationpuzzle.ypicalresultsfromeachof thesemethodsarediscussedbelow.IsothermalThermo-OxidativeDegradation: typicalfractionalweightlosscurvefo rihedegradationofETFEinsulationat2S0CinanaircirculatingovenisshowninFigure1 .heradiationdosevariedfrom 0to4SMrads.sothermalETFEweightlosscurvesindicateacomplex,multistepdegradationprocess.Withinthefirsthour,ETFEloses.:r\ni: . '


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1 3

wherea=degreeofconversionA=lineardegradationcoefficientB=additivescoefficientC=exponentialratecoefficientD =Coefficientfo rvolatilizationoflowmolecularweightcompoundsH=stepfunctionoccurringatt=0TheAparameterreflectsweightlossof theETFEpolymer,Bindicatestheamountofadditivesintheinsulation,Creflectstherateatwhichadditivesarelost,andDreflectsthecompoundswhichevolveduringheating.he effectof bothtemperatureandradiationonthesevariableswas determined.hebestfittotheexperimentaldatayieldedthefollowingexpressions:

A= \Alx\0,0e\p(-\51{U/wl)/RT)+ 2.69x\0i-X-exp(-\U{kJ/mol)/RT) (2)

/ > '=2.49x10'+ 4.14xlO-A '3a)/;=54()xl0" -+2.3 5x10"4A '3b)

where

X=radiationdose(MRad),R=gasconstant,andT=temperature(K),respectively. isessentiallyindependentofdose.


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14

ETFEwire(insulationandunmodifiedconductor)sampleswithradiationdosesfrom0to48MRadsweredegradedinanaircirculatingovenattemperaturesrangingfrom240Cto300C.ypicaldegradationcurves,inwhichtheamountofpolymerremaining.,[(1-ct)whereaisthedegreeofconversion]asafunctionof timeat260Care showninFigure2.tisreadilyapparentthatthehighertheradiationdose,themorerapidlythepolymerdegrades.or examplethetimeforthesampletoincura10% weishtlossinthepresenceofmetalisonlyone-thirdthatrequired intheabsenceofmetal;thiscomparisonissummarizedinTable2.Weightlossinthepresenceofthemetalisotalinearfunctionof time,bu tshowsadependenceon thedegreeofconversion,a.Weightlosscurvesexhibitastrongdependenceon dosefo rirradiationlessthan0MRadsbutfortheheavilyirradiatedsamples,i.e.29 ,3 8and4SMRads,thera;e>of weightlossareessentiallythesame.IsothermalThermogravimetricAnalysis: IsothermalTGAwasusedto(1 )investigateshort-termdegradation,and(2)determinetheeffectofdifferentenvironmentalgases.Ti;> dataservesasanexcellentcheckonisothermalovenexperiments.

TheeffectoftemperatureontheisothermaldegradationprocessisillustratedinFiirure3v . heretheweightlossisshownasafunctionof timeattemperaturesrangingfron,24'TCto300Cforinsulationirradiatedat4SMRads.hedataisconsistentwiththatobservedintheisothermalovenstudiesNon-IsothermalTGA:wonon-isothermalTGAmethodswereusedtoestimatethekineticparametersfo rtheETFEdegradationprocess,asacomplimenttoisothermalmethodsdescribedabove.herespectivemeritsof theFlynnandWall(2)methodandthekinetic jumpmethod(3 )willbediscussed,alongwithacomparisonofresults.


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15

KineticJump:he kineticjumpmethodisatechniquetoobtaintheactivationenergy foradegradationprocessinaselectedtemperatureintervalatagivendegreeofconversion(3).uringagivenruntheisothermaltemperatureiscycledbetweentwoormoretemperaturesandtheactivationenergyA)calculated bymeasuringtheratesattwotemperaturesandusingthesimpleformoftheArrheniusequation:

AE=RTrT/{AT-\n[R(T)/R(Tl)}}4)whoreR[T,)andRft)retheratesof thetemperaturesT2andTrespectively.hejumpscanbeconductedataseriesoftemperatures,degreesofconversion,andradiationdoses,andallotherkineticparameters,suchasreactionorder,areeliminated.hepracticallimitsofthismethodarerestricted bythelowsignal-to-noiseratioatlowtemperaturewhendegradation ratesare small.DynamicTGA:ndynamicTGA samplesareheatedatdifferentheatingratesicneratingaseriesofcurvesofweightlossversustemperature.heratesof degradationa:thedifferentheatingratescanbeanalyzed.hedatacanbeanalyzedaccordingtotheFlvnnandWallmethodwhichisderivedfromthenon-isothermalkineticequation

da/dt= f[a)*k{T)*g{a,T)5)wherea=degreeofconversionT=temperature


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Thismethodassumesthatthedegreeofconversionandtemperaturevariablesareseparable,thereforeg(a,T) =1 .sinthethermaljumpmethod,kisassumedtohaveanArrheniusdependence,leadingtotheequation

da/dt= f(a)*A*exp(- /RT).6)Themathematicsandapproximationsinvolvedinthismethodhavebeendescribed by severalauthors,fo rexampleseeRef1 .Multipleexperimentsatdifferentheatingratesarecomparedatthesamedegreeofconversion,eliminatingtheeffectoftheconversionterm,andtheactivationenergycanbeobtained directlyfrom theTGA data.

Experimentswereconductedinair,oxygen,andnitrogenon ETFEsamplesheatedat1,2.5,0, 5,and20C/min.ctivationenergieswerefoundat0.57oconversionintervalsbetween5%and9 . 5%,theresultsaresummarizedinTable3 .Activationenergiesfromirradiatedsamplesdegradedinairaveraged15 5kJ/mol.Unirradiatedsamplesbehavedifferentlythanirradiatedsamplesandexhibitamuchhiehcractivationenergy,intherangeof23 5kJ/mol.argedeviations(about10%)werer.mcdinthesamplesirradiatedto29 MRadand38MRad.tthehighdegreesofconversion,theactivationenergiesdecreased,withanaveragedecreaseof 6% throughtheconversionrange.amplesdegradedinnitrogenweremorestable,withtemperaturefactorsabove200 kJ/molatallirradiationdoses.amplesdegradedinoxygenare different! seriesofexperimentssimilartothosedescribedaboveontheinsulation,fo rwiresamplesaresummarizedinTable4.heerrorassociatedwiththeseexperimentsiscrcatcrthanthatassociatedwithinsulationalonebecausetheratesareastrongerfunction ofthedegreeofdegradation.


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1 7

Thetemperaturefactorfo runirradiated ETFEisapproximately100kJ/mollowerthanforthesampleirradiatedat6MRads.orradiationdosesgreaterthan6MRadstheactivationenergiesinoxygenarebetween150and170 kJ/mol.hedegradationofwireinoxygenismorecomplex. tleasttwodifferentdegradationprocesseswereobserved;theirrelativemagnitudesdependupontheTGA heatingrate. deconvoluteddegradationratecurveisshowninFigure4.urprisingly,thetemperaturecoefficientsdeterminedbyasimpleArrheniusplotsuggestthatthehighertemperaturereactionhasalowertemperaturecoefficient.xperimentsinairandoxygenreach5-10% conversionatlowertemperaturesthaninnitrogen,whichfurthercomplicatesadirectcomparisonbetweenkineticparameters.IsothermalTGA

IsothermalTGAexperimentsareusedtoexplorethedegradation processatlowtemperatures.heseresultscanbedirectlycomparedwithisothermalTGAexperimentsa:highertemperaturesbyappropriatekineticexpressions,however,itshouldbenotedmatintheovenexperimentsthereactionatmosphereisrestrictedtoair.

Theinsulationexhibitsaconstantweightlossratethroughouttheconversionrangeofinterest(39r-309c).heweightlossrateislinearlydependentonirradiationdose,andanArrheniustemperaturecoefficientof150kJ/molwasobservedintherangeof240"to2S0"C.Experimentsinnitrogenshowsthesamegeneraltrends,withalowerdegradationrate.thightemperatures(320"Candaboveinair,or 300Candaboveinoxygen),therateofweightlossisnotlinearwithtime,seeFigure5.tlowconversions,thedegradationratepassesthroughaminimumwhichrapidlyincreasesforconversionof


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IS

theorderof15-20%.Athighconversions,thedegradationratedecreasesslowly.Thisphenomenonismuchmorepronouncedinwire,i.e.inthepresenceof theconductor.IsothermalJumpMethodTGA.heisothermaljumpmethodoffersanalternativemethodtodynamicTGAfo rdeterminingtemperaturedependenceofthedegradationprocess.-singlesampleisdegradedattwoalternatingtemperatures(typically300Cand310C),whiletheresultingweightlossrateismeasuredbytheTGA. tspecifiedconversions,thetemperature"jumps"fromonetemperaturetotheother.verthissmallof atemperaturerange,itisassumedthattheexperimentyieldsweightlossratesattwodifferenttemperaturesforthesameconversion. singtheratioofthesetwodegradationrates,anArrheniustemperaturedependenceyieldsatemperaturefactor.hismethodismoretime-consumingthandynamicmethods,andmorevulnerabletoerrorsfromnoise,butlacksthesystematicerrorfromsamplevariation.orETFEmeasurementsinair,theactivationenergieswerecomparabletodynamicdata,withmorescattering,duetoexperimentalerror. notabledifferenceoccurredinunirradiatedETFEinsulationwhere;:.-ae;;vationenergieswere130kJ/mol(comparedto20 0kJ/molindynamice\rerimeii!s):nnitrogen,thetemperaturefactorswerelowerthanobservedinthei!\r..:m:cmethod,between150 and170 kJ/mol.noxygen,thedatawereconsistenti.e.metemperaturefactorswereessentiallythesameforbothmethods.

ThedegradationofETFEinthepresenceofconductorisdifferentthaninitsalienee.nairthetemperaturefactor*arebetween120 and 35kJ/molandexhibitlessscatterthanobservedinpolymer,thisprobablyarisesfromthehigherdegradationratestherebvincreasingthesignal-to-noiscratio.egradationofirradiatedwiresamplesinnitrogenalsoshowedlowertemperaturefactors(130-150kJ/mol),howeverwithgreater


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19

experimentalscatter.Someofthedifferencesintheresultsobtainedby dynamicandisothermaljumpexperimentsmayresultfromthedifferenttemperatureregionsusedinthetwoexperiments. InfraredAnalysis:Whenagedaspolymer,thesampleswereflatteneddirectlyforIR analysis,whiletheinsulationfromwiresampleswasseparatedfromtheconductorbycuttingthepolymerlengthwisedownthewires,andthetwopieceswereflattenedandanalyzed.othsidesofthesamplecouldbeanalyzedbythismethod;thesurfaceindirectcontactwithmetalsurfaceandthesurfaceexposedtotheambientenvironment.tvpicalFT-ATR differencespectra,inwhichthespectrafromasampleagedfor53hoursat270C(irradiated to6MRadpriortoaging)minusthespectrafromanunagedsample)i> showninFigure6.he IR spectrumshowstwodistinctregions: 1 )therange1750-1500cm"1sattributed topolymeroxidation,i.e.carbonyl,and2)therange1000-1350 c : : > . . N primarilyduetoC-F bonding.hebroadpeak(1750-1500 cm"1)increaseswitha-jiri;;andismorepronouncedinsamplesinwhichETFEisincontactwiththeAe/Cuconductor.heIRspectraldataissummarizedinTable5.Ajiin:oftheSilver/CopperInterface:hemajorobjectiveofthisprojectistodeterminetheoveralldurabilityof thepolymer/metalsystem,i.e.theinsulationandtheconductor Althoughusuallyneglected,theconductorisacomplexsystemwhichciuUL'eswithtime.nmanyelectricalsystems,theconductorisacopperwirecoatedwithathinlayerofmetal,suchassilver,primarilytoenhancesolderability.owever,during prolongeduseathightemperature,coppercandiffusethroughthesilverlayer,markedlychangingthecharacteristicsofthemetal.ctivemetals,suchascopper,silverortheiroxidesarewellknownfortheircatalyticactivity.Wehaveobservedinsomeinstances


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20 thatthemetallicdiffusionprocessisafunctionofthepolymercoating.Therefore,thedegradationofthepolymericsystemchangeswithtime.Wehaveexamined thisphenomenonbytheuseofscanning Augerspectroscopy.

Ofparticularinterestisthediffusionofcopperthroughthesilverlayerandthesubsequentoxidationofthecopperlayer.Alayerofsilver,5x10- 'cm thick,isapplied overmetalliccopper.]he concentrationof Ag,Cu,C,O,Sb,andClweremonitored following controlledthermalagingasafunctionofdepthbyscanningAugerspectroscopy;atypicaldepthprofileisshowninFigure7.heinterfacebetweenthesilverandcopperlayersoftheunagedsamplesisrelativelysharp,approximatelySxlO'cmthick,andcontainsonlysilverandcopper. ttypicalscanningAugertraceof ana^cdsampleisillustratedinFigure8.nthisparticulartrace,thesamplehadbeenirradiatedtoatotaldoseof48 MRadsandagedinanairenvironmentfo r181hoursat25'JC.tisimportanttonotethatthesurfaceisessentiallyalayerofcopperoxide(theapproximatestoichiometryisCu :70basedonatomicratios)6xl0'5cm thick. smalla:::o.:r.;of Sbwasalsoobservedonthesurface:hesourceofSb maybefromSbF ?v .iv.jhi softenaddedtoinsulationasaflameretardant.hediffusionofcopperandits subsequentoxidationwasinvestigatedasafunctionof1 )radiationdose,2)agingtemperature,and3 )presenceor absenceof polymercoatingonthediffusionprocess.Theefieetofradiationdose,temperature,time'of aging,andpresenceorabsenceofpolymeronthediffusionprocessisillustratedinFigure9.hediffusionofcopperthroughthesilverlayerisreadilyapparent.

Theeffectof thepolymeronthemetalsurfaceduringaginghasalargeinfluenceonthediffusion/oxidationprocess.Mostsamplesagedasconductor(inabsenceof


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2 1

insulation)displayedacopperandoxygenlayerontheirsurface,withlittleor no silverpresent.he compositionofthislayer(atomicratioofcoppertooxygen)shiftedfrom 1.5:1onthesamplesurfaceto2:1atdepthgreaterthan500 nm .heseratiossuggestthatthesurfacelayerconsistsofCuOwhiletheinteriorregionisamixtureof CuOandCu:0.Thethicknessof thecopperoxidelayerincreasesasagingtemperatureandtimeincrease,andistypicallybetween3 00and60 0nm thick. silverlayerfollowsthecopperoxidelayer,andthebulkinterioriscopperonly.sexpected,theoxygenconcentration decreaseswithdepth;forexampleseeFigure8.WhentheconductoriscoveredwithETFE,thediffusionismorerapidandthecoppersurfacelayeristhicker;theratioofcoppertooxygenatthesurfaceisapproximately3:1anddecreasesasonemovesintothebulksample,seeFigure9.he silverprofileisbroadsuggesting thatthesilverisnotstationarybu talsodiffuses.owever,therateofdiffusionofsilverincopperissignificantlyslowerthanthediffusionofcopperthroughsilver.Analysisof DegradationProducts.heprimaryproductsidentified byGC/MSanalysisoftheeffluentproductswereHFandfluorinatedhydrocarbonsoftheparentcompound.Theprimarymassspectralpeakwasatm/- ^-147andcorrespondsto[CIIX'ILCRCF,]'.onscorrespondingtohigheroligimersof theparentmoleculewerealsoobserved.Microscopy: Opticalmicroscopywasusedtoobservechangesinboththesurfacesoftheinsulationandconductorbothbeforeandafterdegradation/aging. The sampleswerenormallyviewedatamagnificationof900X.hesamesampleswerealsostudiedbyATR-FTIR.nmanyinstancesthesilverlayerwasobservedto"peel"offthecopperconductor.or example,theinsulationremovedfromagedwire(i.e.sampleagedfo r20


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-n

oursat270C)displayed longthinmetallicstripesata45 angletotheaxialdirectionofthesample(thelengthofthewire).he silvercolorandwidthofthesestripes,combined withthematchtothehelicalpackingofthewirestrands,suggestthatthesilverlayeron theconductoradherestothepolymersurface.stheirradiationdose,temperature,ordegradationtimeincreases,theadhesiontothepolymerbecomesmorepronounced.he conductordisplayedcorrespondingcolorchanges,withasilvercolorappearingatthesidesofastrand,andshadesofredor orange(indicativeofcoppercompounds)inthecenterofindividualstrands.hislatterphenomenonindicatesthatthediffusion/oxidationprocessisstronglyinfluenced bythepresenceofthepolymercoating.

TheSEManalysisshowed,thatinmanycases,thesilverlayerwasstronglyattachedtothepolymerlayeranduponremovaloftheinsulationfromthewire,thesilveradheredtothepolymer.hisphenomenonisillustratedinFigure 0wherethecenterregionofthephotoshowsalayerofsilverandbarecopperonboththeleftandrightsides.hisparticularsamplewasirradiatedtoadoseof9MRadandagedaswirefor20 l iat270C.heinteriorsurfaceoftheinsulationhadasmoothsurface,whilethesurfacelavcrcontainedmanybumpsandcrevasses.nanotherlocationonthesamesampletheouterlayerpeeledawayandanelementalanalysis(EDS)oftheinteriorpeeledregionindicatedthattheadheringsurfacewas83% silverand17% copper.hecompositionofthelaveranditslocationsuggestthatthisisthesilvercoating,andthatitdebondsfromthecopperandattachestothepolymerduringaging.Thisobservationagreeswiththeopticalmicroscopyexperiments.


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ZJ

SORPTIONOFFLUIDS ThesorptionofCS2intoamorphousPPSasafunctionoftemperatureisillustrated

inFigure11.hesorptionprocessactuallyconsistsoffourseparateregions: 1 )aninitialregioninwhich -3wt% israpidlysorbed,2)aregionwhichiseventuallylinearwithroottime(pseudo-Fickianregion).3 )amaximumvalue,and4)a"pseudo-equilibrium"regioninwhichthesolubilityisessentiallyconstant.hesorptionoftolueneinamorphousandcrystallinePPSat24isshowninFigure2.hesorptionprocessissimilartothatobservedwithCS:exceptthatthesorptionincrystallinePPSissignificantlyless.

Theinitialrapidsorptionprobablyarisesfromstressenhancesorptiondue tosurfacestresses.heactivedepthof thestressedregioncanbe estimated:fthe .surface"issaturated,itcomprises10% of thesamplethickness(2wt% dividedbytheequilibriumsolubility,20wt%).hefilmsare0.262mmthickandcontaintwoactivesurfaces,thus,thestressedsurfaceisapproximately0.013 mm(or3p:m)thick.

Thesecondregioncorrespondstothenormalsorptionofanorganicfluidinapolvmcr.heshapeof thecurveisgovernedbytherateof penetrationofthefluid

,comparedtotherateofrelaxationoftheswollenpolymerbehindtheadvancingfront.Thepseudo-Fiebianregion,correspondingtoweightgainwhichisalinearfunctionofthesquare-routtime,indicatesthattherateofdiffusionisgreaterthantherateof relaxation.Themaximumisthesorptioncurveandtheassociated gentledecreaseinamountsorbedarisesbecausethepolymerundergoessolventinducedcrystallization.mallamountsof solventaretrappedinoradjacenttothecrystals,thesolventisslowly"squeezed"outofthecrystalsasthesampleslowlyapproachesequilibrium.hisisinsharpcontrastto the


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24 sorptionof fluids,suchaswater,inepoxieswherethesamplecontinuestosorbwater,evenafterthousandsofhours,astheresinslowlyrelaxes.

The sorptionofCS2andtolueneintocrystallinePPSexhibitquitedifferentphenomena.S2isreadilysorbedincrystallinePPSalthoughitsrateofsorptionisapproximatelyone-hundredththatofthesorptionrateobservedinamorphousPPS.However,itsequilibriumsolubilityincrystallinePPSisonly15% lessthanthatobservedinamorphousPPS;atypicalsorptioncurveisshowninFigure 3.othsolubilityandrateofdiffusionoftolueneintocrystallinePPSaresmall:eeFigure2.

Ofparticularinteresttotheoverallmechanismistheresorptionofafluidintoaresinfromwhichtheinitialsaturatingpenetranthasbeenremoved.hi sparticular studyactuallyconsistedof 4separateexperiments:esorptionofeitherCS2ortolueneintoaresinoriginallysaturatedwithCS2or onethathad beensaturatedwithtoluene:hiscanheabbreviatedasCSVCS2,CS:toluene,toluene/CS2or toluene/toluene.heseresultsaresummarizedinFigures4and 5.respectively.hesorptionandsubsequent^surpiionofCS:frominitiallyamorphousPPSat26,33,and40CareshowninFigure! < Followingthefirstsorptionthesampleswerecompletelyabsorbedat65Cina\.:;iunnoven.hesolubilityisessentiallyindependentof temperature,approximately 7 v.i\i.comparedtotheinitialsolubilityof approximately20wt9c.

I tisimportanttonotethevastdifferenceinthesorptionofCS2andtoluene,particularlywithrespecttoresorption.lthoughCS2andtoluenehavesignificantlydifferentvaporpressuresatanygiventemperature,i.e.theboilingpointsofCS2andtolueneare 40 and110C,respectively,theprimarydifferencewithregardtosorptionistheirmolecularsize.troomtemperature,themolarvolumesofCS2andtolueneare


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58.7and106cm 3,respectively.heaveragemolecularvolumeofCS,andtoluenewerecalculatedandreportedtobe 49 and92A\respectively(5).

AmorphousPPScanbe thermallycrystallizedbyheatingitabovetheglasstransitiontemperature.ypicalDSC thermogramsforPPSheatedaboveandbelowits T(85-90C)areshowninFigure7.hreenoticeablefeaturesare exhibitedinthethermogram ofatypicalamorphousPPSsample(showninfigure17A):aistheTgatabout85-90C,isthe"coldcrystallization:exothermatabout130Candy isthemeltingendothermatabout290C.hemagnitudeof the"coldcrystallization"peakdecreaseswhenPPSisheatedattemperaturesabove70CCandisabsentwhenPPSisheatedattemperaturesat110Candabove.ccordingtoBrady(6),theheatofcrystallizationof100% crystallinePPSisS0kJ/kg.heratioof theexotherm(at130C)orendotherm(at290C)totheheatof thecrystallinitygivesthedegreeofcrystallinityproducedduringthe"coldcrystallization"or .thedegreeofcrystallinityinthesampleatthetimeofmelting,i.e.,fc=H N I/H C).respectively.he"coldcrystallization" exotherms:;rcshownincolumn2ofTable6andthecrystallinitiesproducedduring"coldcrystallization"areshownincolumn3 ofTable6.he% "coldcrystallinity"inatypicalamorphou-.PPSsamplegivesthemaximumc


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26 producedduringdryingisequaltothemaximum%"coldcrystallinity"(28%)minusthe%"coldcrystallinity"observedinthethermogram.heabsenceofthe"coldcrystallization"peaksinFigure 7 D andE(driedat110Cand130Crespectively)suggestthatthedegreeofcrystallinitythermallyinducedisgreaterthanor equalto28% .ThePPSthermogramsresemblethethermogramsofPEEK (7)wherethecrystallizationexothermismuchsmallerthanthemeltingendotherm.hisobservationhasbeenexplainedbynotingthatthecrystallizationprocessinPEEK continues(aftertheinitialcoldcrystallization)duringtheDSC scantoform "moreperfectcrystals"whichmeltatabout345C(7).

Typicalweightgaincurvesinwhich%weightgainisplottedasafunctionofsquare-roottime(Fickianform)fordifferentdryingconditionsaresummarizedinFigureIS.nexpandedviewof thisgraphshowingthefirst25hoursisshowninFigure9.i\pu\i!weightgaincurvefo ranamorphoussample(asreceived)isshowninFigure20 .

Ingeneral,sorptioncurvesforsamplesdriedator below100CshowthreemajorrcL-h'n,iseeFigure20):A)arapidinitialperiodwhichexhibitsanaccelerated absorption,(B )asteadyweightgainwhichisapproximatelylinearwithsquareroottime,andtC itheweightgaincurverisingtoitsmaximumvalueofabout11 .5%.hislatterphenomenamaybeduetoanexpulsionofasmallamountoffluidfromthecrystallineregion.whilethesystemattainsequilibrium,ormayarisefromtheextractionofasmallamountoflowmolecularcompoundsintotheimmersionfluid.

Theinitialsorptionforsamplesdriedatorbelow100C(seeFigure19)occursapproximatelywithinthefirst10s.Thissorptionhowever,isno tseenfo rsamplesdriedatorabove110Csuggestingthatinitialsorptionisassociatedwithsurfacemorphology.


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27Thecrystallinityofsamplesdriedatorabove110Cisatleast2Z%whereasthecrystallinityofsamplesdriedator below100Cisbelow28%.llthecurvesshowalinearrelationshipwithsquareroottimeaftertheinitialrapidsorptionsuggestingthatFick'slawsareapplicable andpseudo-Fickian-likediffusion coefficientscanbe estimated. markeddecreaseintherateofdiffusion(whichisproportionaltothesquareoftheslope)fo rsamplesdriedat110Ccomparedtothatfo rsamplesdriedatorbelow100C,suggestthatdiffusionisafunctionofdryingconditions.heratiooftheslopeforsamplesdriedat110Ctothatfo rsamplesdriedator below100Cisapproximatelyone-sixteenthimplyingthatthediffusioncoefficientsfo rsamplesdriedat110Cisapproximately250 timessmallerthanthatforsamplesdriedatorbelow100Csincediffusionisproportionaltothesquareoftherateofdiffusion.


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2S

Sample

BD

TablePropertiesofElectricalWireSystem RadiationDose(MRad)

0

1 9 29 3S4S

MeltingPointC)265.3 261.5 259.1 255.2251.6249.246.7

"Measuredby DSC:he minimumisthemeltingendotherm


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29 Table2.Comparisonoftime(hours)to10% ETFEweightlossfrompolymeraloneandincontestwithAg/Cuat260C

Dose(MRads)9Insulation(min) 17700 13900000 Wire(min)900 2800800 2 9 3 8 4 86900 4500 40501700 1475 1400


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30 Table3Activationenergies(kJ/mol)fromthedynamicmethodforthedegradationofirradiatedETFE

Environ- Radiation Degree o f conversion(%)ment (Mrads) 5 6 7 8 9 1 0 a v e 0*A i r 0 2 4 1 2 3 8 2 3 6 2 3 5 2 3 3 2 3 2 236 3 . 3A i r 6 1 5 2 1 5 6 1 5 7 1 5 8 1 5 7 1 5 7 1 5 6 2 . 1 A i r 9 1 6 4 1 6 2 1 6 0 1 5 8 1 5 8 1 5 7 1 6 0

2 . 7A i r 1 9 1 6 2 1 6 0 1 5 8 1 5 7 1 5 6 1 5 5 1 5 S 2 . 6A i r 2 9 1 8 5 1 S 2 1 7 8 1 7 3 1 7 0 1 6 6 1 7 6 7 . 3A i r 3 8 1 4 5 1 4 3 1 4 3 1 4 2 1 4 1 1 4 1 1 4 3 1 . 5A i r 4 8 1 6 9 1 6 1 1 5 6 1 5 4 1 5 2 1 5 0 1 5 7 7 . 0Nitrogen 0 2 2 1 2 2 3 2 2 5 228 2 3 1 2 3 4 227 4 . 9Nitrogen 6 200 2 0 2 2 0 2 205 206 2 0 9 204 3 . 3Nitrogen 9 204 2 0 6 2 1 2 219 225 2 2 9 216 1 0 . 2Nitrogen 1 9 219 2 2 2 2 3 0 240 247 2 5 0 2 3 5 1 3 . 0 Nitrogen 29 1 7 6 1 7 9 1 8 4 1 9 0 1 9 7 2 0 3 1 S S 1 0 . 5Nitrogen 3 8 210 2 1 2 2 2 6 249 259 269 2 3 S 2 5 . 0Nitrogen 4 8 237 2 4 0 246 254 260 2 6 1 250 1 0 . 20\>ge n 0 1 4 6 1 4 7 1 4 8 1 4 9 1 5 0 1 5 0 1 4 8 1 . 6Oxygen 6 1 0 1 1 0 1 1 0 3 1 0 6 1 0 5 1 1 0 1 0 4 3 . 4Oxygen 9 1 6 9 1 7 0 1 7 0 1 6 9 1 6 8 1 6 7 1 6 9 1 . 2C)\\gen 1 9 1 8 1 1 S 4 1 8 6 1 8 7 1 8 6 1 8 4 1 8 5 2 . 2(Kygen 2 9 1 9 8 1 9 5 1 9 4 1 9 3 1 9 3 1 9 2 1 9 4 2 . 1(\ygen 3 8 200 2 0 2 2 0 3 2 0 3 2 0 3 2 0 4 2 0 3 1 . 4t\\^en 4 S 2 2 5 2 1 S 2 1 4 212 209 206 2 1 4 6 . Sn " Standard d e v i a t i o n ,l o


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31Table4Activationenergies(kJ/mol)fromthedynamicmethodforthedegradationofirradiatedETFE

Environ- R a d ia tion(Mrads)

04

19 75

197De g r e e o fconversion (%)

m e n t 6 7 8 9 1 0 a v s a* A i r 1 9 7 1 9 8 1 9 7 1 9 6 1 9 6 1 9 7 0 . 7A i r 6 1 6 2 1 5 S 1 5 5 1 5 4 1 5 3 1 5 3 1 5 2 1 5 5 3 . 5A i r 9 1 7 4 1 6 9 1 6 5 1 6 1 1 5 8 1 5 5 1 5 3 1 6 2 7 . 6A i r 1 9 1 6 3 1 5 S 1 5 7 1 5 4 1 5 3 1 5 2 1 5 1 1 5 5 4 . 2A i r 2 9 1 6 5 1 5 S 1 5 7 1 5 5 1 5 3 1 5 2 1 5 1 1 5 6 4 . SA i r 3 8 1 5 7 1 5 6 1 5 4 1 5 1 1 5 0 1 4 S 1 4 7 1 5 2 3 . 9A i r 4 8 1 6 8 1 6 1 1 5 7 1 5 4 1 5 2 1 5 0 1 4 8 1 5 6 6 . 9Nitrogen 0 2 4 1 2 4 2 2 4 1 240 239 2 3 9 240 1 . 2Nitrogen 6 2 0 2 2 0 2 2 0 1 202 20S 2 1 2 2 0 5 4 . 5Nitrogen 9 2 0 8 2 1 3 226 239 i~>~> 1 3 . 9Nitrogen 1 9 2 0 9 2 1 4 230 2 4 3 224 1 5 . 5Nitrogen 2 9 2 0 2 2 0 7 217 2 2 1 7 ] " > S . SNitrogen 3 8 2 1 1 2 1 8 2 2 5 2 2 5 220 6 . 7Nitrogen 4 S 2 1 2 2 1 4 224 2 2 6 219 7 . 0Oxyge n 0 1 2 9 1 3 0 1 3 1 1 3 3 1 3 3 1 3 4 1 3 2 2 . 0Ox>ge n 6 1 2 1 1 2 1 1 2 3 1 2 4 1 2 5 1 2 5 1 2 3 1 . 8Ox\ge n 9 1 4 9 1 4 7 1 4 8 1 4 8 1 4 S 1 4 6 1 4 8 1 . 0\\ge n 1 9 1 6 3 1 6 5 1 6 4 1 6 3 1 6 0 1 5 9 1 6 2 2 . 3Ox>ge n 2 9 1 6 6 1 6 5 1 6 4 1 6 3 1 6 0 1 5 9 1 6 3 2 . 8Uxsge n 3 S 1 6 6 1 6 6 1 6 4 1 6 4 1 6 1 1 5 9 1 6 3 2 . SOw J en 4 8 1 7 3 1 7 0 1 6 9 1 6 6 1 6 4 1 6 2 1 6 7 4 . 1

Standarddeviation,a


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J)-i

Table5SummaryofFT-IRSpectraUnasedETFESpectrumpeaks Source2980(m),2960(vv),2890 (w) C-H stretching 1475(w),145 l(s) CH-,scissoring 1320-1330(s) CH,twisting1252(vs) CF,asymmetric1170(vs) C-C skeletal1115(vs) CF, symmetric1050(vs) CF, 972fm)665(s).510(s) CF2 Additivesandcrosslinks1700 Carbonylstretchfrom TAIC1170 TertiaryC-H (from crosslinks)1120-1010 TertiaryC-F ObservedbothinliteraturespectraandindescriptionofPirozhnaya andTarutina.J.Appl.Spectroscopy3 4539-54119S1).ExperimentalunagedETFEspectrahadweakerC-H stretchingbands

'Timesubstractedspectrapeaks Explanation=4000 - 3600(m ,broad) OH29S0.2960.2890(m) CH stretch,seenin290C,21hrsamples;700-1500(m,broad) Carbonyls(anoverlayof severalin270C,53hoursamples1742im'i Dialkylketone(seenin290C,21hr samples)or -C=DF,( > 1 7im> C=C

i45!(n^ CH,i322 CH, 1165 TertiarvCH

; 1 0 3 * . i < \> ) PossibleshiftofCF:peakdu etochanges insubstituents ;322. 165peaksmaybedependentonjubtractionparameters


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Table6:SC AnalysisofPPS JJ

ReferenceVaue:0kJ/kgTemperature(C ) "Cold"Crystallization Exotherm (J/g)%"Cold"Crystallization Meltingendotherm(J/g) %Finalcrystallinity

%Initialcrystallinity*Asreceived 22.3 27.8S 32 .90 41.13 0 .0 70 22.4 2S.00 32.57 40.71 0 .0 100 8.2 10.27 31 .87 39 .84 17.7110 ~0 -0 32.04 40.05 >2S 130 -0 ~0 31.11 38 .89 >2S

InitialCyrstcllinity=MAX(% "ColdCrystallinity")-%"ColdCrystallinity"measured


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34

References1 .larenceJ.Wolf andR.S.Soloman,"EnvironmentalDegradationof AromaticPolyimide-insulated ElectricalWire,"IEEETrans.Elec.Insulation9,265 (1984).2..H .FlynnandL.A.Wall,"ThermalAnalysisofPolymerby Thermogravemetric

Analysis,"J.Res.Nad.Bur.Stand.,Ser.A70(6)487-523(1966).3 ..H .Flynne"AspectsofDegradationandStabilizationofPolymers,"Chap. 2 pp.573-603 ,H.H.G.Jellinck,ed.Elsevier,Amsterdam,1978.4..J .Wolf,S.C.Hager,andN.P.Depke,"Thermo-OxidativeDegradationofIrradiated EthyleneTetrafluorethylenes,"inOxidativeBehaviorof MaterialsinThermalAnalyticalTechniques,"Eds.A.T.RigaandG.H.PattersonSTP1326ASTM,1997pp.116-127.1 ClarenceJ.Wolf,J.A.Bornmann,andM.L.Gurpon,"TheAbsorption ofOrganic

LiquidsinPoly(Aryl-Ether-Ether-Ketone)[PEEK]"J.Polm.Sei.3:Polym Phys.29 1533-1539(1991).6..J .Brady,J.Applied Polym.Sei.,Phys.Ed.,20 ,25411976).7..J .WolfandJ.A.Bornmann,"DifferentialScanningColoremetry(DSC)toDetermineCrystallinityinPEEK,"Soc.Adv.Mater.Proc.Eng.,34,1167(1990).


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35

0.950.90.85

C35 0 .8 0.75 0 .7

0.65

0 .6 0

o XA0D

O O

2000

xA0

D

xA0

D

4000

1

o 1

oo O I

0MRads X X X 6MRads A A x X < > 0

AA A 9MRads ** oo 0 19MRads

0 $ ** * 29MRads D D % $ 38MRads i

DD D 48MRads

6000 time(min)

8000 10000 1

FIGURE. Fractionalweightoss1-a)remaining as aunction oftime for the thermal degradation ofrradiated ETFE.


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3

0 .9 H .&**j,+ 1 1 i i 1 0MRads ! wire

% 0 + ** + 6MRadswire0 .8 - i ? * A 9MRadswire0 .7

00 AA+ 0* 19MRads 29MRads wirewire0it** o A+

*' $ 38MRads wire0 .6 rei

X 48MRads wiret0.5f

- + -0 .4 _ 0 .3 0

A+-

0.2 0 -0.1 % >i +n i 1 1' #i 01 i

0 1000 2000000000 5000000000000 900000time ( m i n )

FIGURE 2. Percentweight loss for the thermal-oxidative degradation(260C)fwires unctionfim endadiationose.


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1 0 0 VOW

1000 2000 3000Time( m i n )

en


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co

SPUTTERTIMEfmiiO

S .Augersputterprofileofasilverplatedcoppersampleirradiatedtoatotaldoseof4SMUadsandagedat250*Cfor1S1hours.


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SilverShor tTermProfiles

oCD0 *5*b

agedatoagedat+ agedat0agedatXagedatDagedat

dashedline- agedat

solidlineagedat

48MRadwire240Cfor 60hrs48MRadinsulatio

240Cfor60hrs6MRadwire240Cfo r60hrs6MRadinsulation240Cfor60hrs48MRadwire

240Cfor30hrs48MRadinsulatio

240Cfor30hrs48MRadinsulatio240Cfor30hrs48MRadwire240Cfor30hrs

1000 1500 2000 2500depth(nm)

3000 35009.Comparisonof augersputterprofilesfrominsulationandwireagedatdifferentoxidizingconditions.


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FIGURE 10. SEM photomicrograph ofonductorhowingilver platedcbonding from copper substrate. Sample was aged with an ETFEoverlay for0ours at70'C.


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5

A.-asreceived

C-Driedat00C

D-DriedntHOC

E-Driedat130C

30C00C 2OCTemperature 500C 325CFIGURE 17. DSChermogramsromPS annealedtifferenttemperatures.


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52

u

14.00

12.00

10.C0

S.00

6.CO

X+.x4h*Zm

C00

" n x#~. >**ocr

10 15 KoolTimeh ')

X

.-c\Yi.GaXSW.GaXfcWi.Gi 5Wi.c>+ 5 , w i.G J-*\V.Ga OSWi.Ga SWi.Ga

nAsReceived)n60C)nJ0C)n(40C)n70C)nSOC)n90C)nI00C)n110C)n140C)

20 25

FIGURE IS . Percentweightthermal anneal.

cainfoluenentoPSollowing


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M.00

12.00

10 0

1.00

600

jno2noCO

K +

x *+ %Wi.CiinAlRcc:iv

ftWl.GlinS0C)45-Wl.G>in50C)X*W.Giin(4()C)X%W|.Giin7UC) W.Giin8IIC)+%Wl.Gain9I1C)-W.GiinItKIC)OW.Gain1 mo *W. GainHOC)

el)xxX + O x -*x-Vc- Ti*+ 5.r -

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0.5 1. 5 2.5RootTimeh1")

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1 * * " 1 &*

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1 6CO! c1 ^ " ' * B ~ 4 .COc -

1 2CO1 l-1 A %\Vi.Gain(A sRece ived)i >rv,

00 1.0 2.0 30 4.0 5.0 6 .0 7.0in.RootTime(h )

FIGURE0 . Percentweightain curveorhe sorption ofolueneintomorphousPS at0C.

aging and durability of high temperature electrical insulation

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