influence of aromatic amine hardeners in the cure kinetics of an epoxy resin used in advanced composites

-ATERIALS2ESEARCH6OL.O  Ú )NmUENCEOF!ROMATIC!MINE(ARDENERSINTHE#URE+INETICS OFAN%POXY2ESIN5SEDIN!DVANCED#OMPOSITES -ICHELLE,EALI#OSTA,UIZ#LAUDIO0ARDINI-IRABEL#ERQUEIRA2EZENDE $IVISáODE-ATERIAIS)NSTITUTODE!ERONÕUTICAE%SPA½O#ENTRO4£CNICO!EROESPACIAL !-2)!%#4!0RA½A-ARECHALDO!R%DUARDO'OMESNŽ  6ILADAS!CÕCIAS3áO*OS£DOS#AMPOS 30"RAZIL 2ECEIVED3EPTEMBER2ECEIVED*ANUARY #OMPOSITESTRUCTURESFORAEROSPACEAPPLICATIONSAREMAINLYMADEBYTHEWELL KNOWNPREPREGTECHNOLOGY)N ORDERTOACHIEVEADEQUATEPREPREGPROCESSINGSCHEDULESANDCONSEQUENTLYMAXIMUMlBERSTRENGTHUTILIZATIONONE HASTOKNOWINDEEPTHECUREKINETICSOFMATRIXWHICHHELDTHElBERSTOGETHER4HISWORKDESCRIBESAPROCEDURETO STUDYTHECUREKINETICANDHASASEXAMPLEHOWAROMATICAMINEHARDENERSINmUENCETHECUREKINETICSOFANEPOXY RESINUSEDINADVANCEDCOMPOSITES4HEINVESTIGATIONWASCARRIEDOUTBYUSINGTHE$3#TECHNIQUEANDITWASFOUND THATDEPENDINGONTHESYSTEMUSEDTHECUREKINETICSOFTHEFORMULATIONOBEYSORDERNORAUTOCATALYTICORDER +EYWORDSEPOXYRESINCUREKINETIC$3#ADVANCEDCOMPOSITES )NTRODUCTION 3TRUCTURAL COMPOSITES ARE ENGINEERING MATERIALS MADE OF ORI ENTEDREINFORCINGlBERSDISPERSEDINAMETALLICCERAMICORPOLYMER MATRIX4HE USE OF COMPOSITES MOVED FORWARD IN COMPONENTS OF AIRCRAFTSANDSPACESTRUCTURESDUEMAINLYTOPROJECTmEXIBILITYEASY PROCESSINGLOWERDENSITY^GCM  ASWELLASHIGHMECHANICAL STRENGTHANDMODULUS4HATMATCHERTHEREQUIREMENTSOFTHESTRUCTURES DURINGSERVICE4HISTURNSTHECOMPOSITESPARTICULARLYATTRACTIVEAS SUBSTITUTESOFTHEMETALLICALLOYSFORHIGHDEMANDINGAERONAUTICAL ANDSPACEAPPLICATIONS 4HISWORKFOCUSESONPOLYMERCOMPOSITESWHICHAREMATERIALS MADEOFREINFORCINGlBERSINANEMBEDDEDPOLYMERMATRIX(OW EVER THE PROPERTIES OF COMPOSITES DEPEND ON OTHER FACTORS SUCH ASTHEMOULDINGTECHNIQUESANDCURECYCLES!SACONSEQUENCEIT ISVERYIMPORTANTTHATTHEVALUESOFTHEPROPERTIESUSEDDURINGTHE DESIGNPHASEOFACERTAINCOMPONENTCONSIDERTHEPROCESSVARIABLES INORDERTOOBTAINPRODUCTSOFHIGHQUALITYANDREQUIREDMECHANICAL STRENGTH 4HUS IT IS FUNDAMENTAL TO KNOW ALL THE PARAMETERS INVOLVED INTHECURECYCLE&ORTHATONEOFTHEMOSTUSEDTECHNIQUESINTHE STUDYOFTHEKINETICSOFPOLYMERIZATIONISTHEDIFFERENTIALSCANNING CALORIMETRY$3# 4HEUNDERSTANDINGOFTHECUREKINETICSTHATWILL DELINEATETHECURECYCLETOBEUSEDINTHEPROCESSINGOFPREPREGSISOF FUNDAMENTALIMPORTANCEFORGOODQUALITYADVANCEDCOMPOSITES4HE CUREKINETICSCANBEFOLLOWEDBYUSINGTWO$3#METHODSDYNAMIC ANDISOTHERMAL 4HEISOTHERMALMETHODCANIDENTIFYTWOTYPESOFREACTIONNORDER ORAUTOCATALYTICORDER)FTHEMAXIMUMPEAKOFTHEISOTHERMISCLOSE TOTTHESYSTEMOBEYSKINETICSOFNORDERANDITCANBESTUDIED EITHERBYDYNAMICORISOTHERMALMETHODS )NTHECASEWHENTHE MAXIMUMPEAKISFORMEDINBETWEENANDOFTHETOTALTIME OF THE ANALYSIS THE CURE IS AUTOCATALYTIC AND IT SHOULD BE STUDIED EXCLUSIVELYBYISOTHERMALMETHOD  4HENORDERMODELASSUMESTHATTHEREACTIONOBEYSTHE%QUA TION E MAILMIRABEL IAECTABR  WHEREVISTHEVELOCITYOFREACTIONAISTHEREACTIONRATEORCONVERSIONRATE INAGIVENTIMET"YALINEARPLOTTING%QUATIONITISPOSSIBLETOKNOWTHE VALUESOFNANDK #ONVERSELYTHEAUTOCATALYTICMODELCONSIDERSINDEPENDENTREAC TIONORDERSMANDNASSHOWNIN%QUATION  4HEPARAMETERSDADTANDAAREOBTAINEDFROM$3#ISOTHERMS 4HEREACTIONRATEISOBTAINEDBYTHEREACTIONHEATRATIOD(D4 ATA TEMPERATURE4FROMTHETOTALENTHALPY$(EQUATION   WHERE$(ISTHEEXPERIMENTALENTHALPYCORRESPONDINGTOTHETOTALAREAUPTO THEREACTIONPEAKORFROMTHETHEORETICALENTHALPYFOUNDINTHELITERATURE 4HEVALUEOFAISDETERMINEDBYMEASURINGTHEPARTIALREACTION HEATATATIMET$(PDIVIDEDBYTHETOTALREACTIONHEATISTAKENFROM THEISOTHERMALREACTION$(ISO%QUATION  &INALLYWITHAMINIMUMOFTHREEISOTHERMSONECANOBTAINTHE KINETICPARAMETERS%ACTIVATIONENERGY AND!PRE EXPONENTIALFAC TOR FROM!RRHENIUSPLOTS %XCELLENTREVIEWSCONCERNINGMECHANISMSANDKINETICSOFTHER MOSETCUREAREPRESENTEDINLITERATURE $ESPITETHECONSIDERABLE CURRENTRESEARCHEFFORTINTHElELDOFEPOXYRESINCURENUMEROUSISSUES HAVEYETTOBEADDRESSED4HEREISANUMBEROFPARTIALLYCONmICTING EXPLANATIONSPROPOSEDINRECENTYEARSFORTHEREACTIONMECHANISMSOF EPOXYSYSTEMCURE 4HISWORKDESCRIBESAPROCEDURETOSTUDYTHE CUREKINETICOFPOLYMERICSYSTEMSANDHASASEXAMPLEHOWAROMATIC AMINEHARDENERSINmUENCETHECUREKINETICSOFANEPOXYRESINUSED INADVANCEDCOMPOSITES  0DWHULDOV5HVHDUFK &RVWDHWDO %XPERIMENTAL -ATERIALS 0OLYMERRESINBASE !N EPOXY RESIN OF THE TYPE DIGLYCIDYL ETHER OF BISPHENOL ! $'%"! HAVINGCOMMERCIALNAME$%2 $OW#HEMICAL 0RODUCTS ,TDA WAS USED AS RECEIVED4HIS RESIN IS LIQUID AT ROOM TEMPERATUREITISBIFUNCTIONALANDHAVEANAVERAGEMOLECULARMASS OFGMOL ANEPOXYEQUIVALENTWEIGHTOFANDOFEPOXY GROUPS%POXYRESINCURESMAINLYBYOPENNINGTHEPENDANTEPOXY GROUPEITHERATROOMTEMPERATUREORHIGHTEMPERATUREDEPENDINGON THECURINGAGENTUSED #URINGAGENT 4HE CURING AGENTS USED WERE THE DIPHENYL DIAMINOSULFONE $$3 COMMERCIAL NAME (4  SUPPLIED BY (USTMAN AND THE DIAMINE DIPHENYLMETANE $$- CODE $%( SUPPLIED BY $OW#HEMICAL0RODUCTS $$3 IS A POWDERED CURING AGENT PINK COLOR AND HAVE TO BE MELTEDFORUSE$$-ISPROVIDEDASBROWNmAKESANDALSOHAVETO BEMELTEDFORUSE"OTHCURINGAGENTSAREAROMATICAMINES4ABLE LISTSPHYSICALPROPERTIESOF$$3AND$$-CURINGAGENTS 0REPARATIONOFTHEFORMULATIONS 4HEFORMULATIONSAREPREPAREDBYMIXINGTHE$'%"!RESININ APROPRIATE STOICHOMETRIC PROPORTIONS OF  PPH $$3 AND  PPH $$-4HENTHEYAREHEATEDUPTOTHEHARDENERMELTINGTEMPERATURE FOR APPROXIMATELY  MIN BEING SOON COOLED DOWN IN THE SAME INTERVALOFTIME #HARACTERIZATION $3#SCANNINGSWERECARRIEDOUTINA0ERKIN %LMER 4HERMAL !NALYSIS3YSTEMPREVIOUSLYCALIBRATEDWITHINDIUMUNDERCONSTANT mOWOFNITROGENM,MIN  ANDHEATINGRATEOF—#MIN 4HE WEIGHTOFTHESAMPLESVARIESFROMTOMG3EALEDALUMINUM PANSWEREUSED &OREACHFORMULATIONASCANNINGWASACCOMPLISHED4ABLE INWHICHTOTALHEATOFREACTION$( ANDISOTHERMALTEMPERATURES FOR KINETIC STUDIES WERE OBTAINED 4HE ISOTHERMAL SCANNING GIVES THE VALUE OF THE PARTIAL HEAT OF REACTION $(P 4ABLE  SHOWS THE EXPERIMENTAL CONDITIONS FOR OBTAINING THE ISOTHERMS FOR THE TWO FORMULATIONSUNDERSTUDY 4HECOMPUTERPROGRAM)SOTHERMAL+INETICSINTHECENTRALMODULE OFTHE0ERKIN%LMEREQUIPMENTALLOWSTHEDETERMINATIONOFVARIABLES RELATED WITH THE CURE KINETICS OF EACH FORMULATION4HIS COMPUTER SOFTWAREALSOPROVIDESTHEREACTIONORDERTHATBETTERlTSTOTHERESIN SYSTEMUNDERSTUDY 2ESULTSAND$ISCUSSION 4ABLEPRESENTSTHERESULTSOFTHEDYNAMICRUNSOBTAINEDBY$3# OFTHEEPOXYSYSTEMS$'%"!$$3AND$'%"!$$-4HEONSET PEAKANDlNALTEMPERATURETAKENFROMTHEDYNAMICRUNHAVELOWER VALUESFORTHE$'%"!$$-SYSTEMTHANTHE$'%"!$$3SYSTEM /NTHEOTHERHANDTHETOTALHEATOF$'%"!$$-SYSTEMISHIGHER THAN$'%"!$$3SYSTEM &ORTHE$'%"!$$-SYSTEMTHEREACTIONTEMPERATURESARELOWER THANFORTHE$'%"!$$3SYSTEM4HISHAPPENSPROBABLYDUETOTHE FACTTHAT$$-HASALOWERMELTINGPOINTINRELATIONTO$$34ABLE WHICHINTURNNEEDSALOWERENERGYTOMELTANDTHENPROCEEDSTHE CUREREACTION"ESIDESTHATTHEREISADIFFERENTBETWEENTHERELATIVE 4ABLE0ROPERTIESOFTHEDIPHENYLDIAMINESULFONEANDOFTHEDIAMINE DIPHENYLMETANE #URINGAGENT 0HOWLQJSRLQWSHDNo& 7EIGHTOFACTIVEHYDROGEN GMOL  -OLECULARWEIGHTGMOL  $$3   $$    4ABLE0ARAMETERSUSEDFOROBTAINOFTHECURVESOF$3# $3##URVES $YNAMICRUN )SOTHERMALRUN )SOTHERMALRUN )SOTHERMALRUN )SOTHERMALRUN $'%"!$$7LQLWLDO o& 7HQG o& o& o& o& o& $'%"!$$3 7LQLWLDO o& 7HQG o& o& o& o& o& 4ABLE  #OMPARISON AMONG THE DYNAMIC SCANNING OF THE FORMULATIONS $'%"!$$3AND$'%"!$$- $YNAMICRUN 2QVHWWHPSHUDWXUHo& 3HDNWHPSHUDWXUHo& )LQDO7HPSHUDWXUHo& $+-PRO $'%"!$$    $'%"!$$3     REACTIVITYOFTHE$$3AND$$-DUETOTHEELECTRONDENSITYOFTWO MOLECULES $$3 SHOULD BE LESS REACTIVE SINCE THE SULFONE MOIETY WILLPULLELECTRONDENSITYAWAYFROMTHEAMINEGROUPSWHEREASTHE METHANEMOIETYIN$$-WILLNOT )T IS NOTICED THAT THE REACTION BETWEEN EPOXY RESIN AND $$- HASAHIGHERAMOUNTOFHEATRELEASEDTHANTHEONEWITH$$34HIS SUGGESTSTHATINTHECASEOFPREPREGPROCESSINGTHE$'%"!$$- FORMULATIONWOULDBEMORESENSITIVETOTHEEFFECTSOFACCELERATEDCURE THANTHE$'%"!$$3FORMULATION4HEREFOREINTHEDETERMINATION OFCURECYCLESFORCOMPOSITEPROCESSINGTHECONTROLOFTHEPROCESS INGCONDITIONSMUSTBEMUCHMORECONTROLLEDWHENUSINGTHE$$- HARDENER "EINGKNOWNTHEDYNAMICRUNOFTHE$'%"!$$3AND$'%"! $$-FORMULATIONSTHREESPECIlCTEMPERATURESWERECHOSENFORTHE ISOTHERMALRUNS4HEISOTHERMALTEMPERATURESWERECHOSENBETWEEN THEBEGINNINGOFTHEREACTION8 ANDPEAKTEMPERATUREBECAUSEMAIN KINETICEVENTSOFTHEREACTIONOCCURINTHATAREA!NOTHERISOTHERMAL RUNWASOBTAINEDATATEMPERATUREOFONEFOURTHDISTANCEFROMTHE INITIALTEMPERATUREANDTHEPEAKTEMPERATUREWHICHGIVESINFORMATION ONTHEKINETICORDEROFTHESTUDIEDFORMULATIONSYSTEM &IGURESHOWSA$3#CURVEWHEREMAXIMUMEVOLUTIONOFHEAT ORTHEMAXIMUMREACTIONRATEDADT OCCURSATTHEBEGINNINGOFTHE REACTIONIEATACONVERSIONA^4HEREFORETHE$'%"!$$3 SYSTEMOBEYSNORDERCUREKINETICS4HENORDERKINETICSIMPLIESTHAT THEFORMULATIONOBEYS%QUATION4HEORDERNREACTIONALSODESCRIBES THESHAPEOFTHEISOTHERMALRUNEXPONENTIALFUNCTION ASOBSERVEDIN THE&IGUREANDGIVESTHENECESSARYDATATOTHESTUDYOFTHEREACTION MECHANISM4HUSTHEVALUEOFNINmUENCESTHERATEOFREACTIONOFTHE FORMULATIONWHICHINTURNALLOWSTHEDETERMINATIONOFAPPROPRIATE CURECYCLESFORCOMPOSITEPROCESSING &IGUREEXHIBITSTHEISOTHERMALRUNTHATCHARACTERIZESTHEREAC 9RO1R  )NmUENCEOF!ROMATIC!MINE(ARDENERSINTHE#URE+INETICSOFAN%POXY2ESIN5SEDIN!DVANCED#OMPOSITES TIONORDERFROMTHE$'%"!$$-FORMULATION)TISOBSERVEDTHAT THE MAXIMUM HEAT EVOLUTION THE MAXIMUM REACTION RATE DADT OCCURSINBETWEENANDOFTHETOTALREACTIONTIMEIEATA CONVERSIONAx4HEREFORETHE$'%"!$$-SYSTEMOBEYSTHE AUTOCATALYTICCUREKINETICS !UTOCATALYTICCUREKINETICSIMPLIESTHATTHEFORMULATIONOBEYS %QUATION4HECONSTANTMISRELATEDTOTHEAUTOCATALYTICCONCENTRA TIONOFTHEREACTIONIETHECONCENTRATIONOFHYDROXYLSGROUPSTHATARE BEINGGENERATEDASCUREPROCEEDSANDTHECONSTANTNISRELATEDTOTHE CONSUMPTIONOFEPOXYGROUPS"ESIDESMINmUENCESTHEINITIALRATE OFREACTIONANDCONTROLSTHESYMMETRYOFTHECURVEANDTHECONSTANT NDElNESTHEREACTIONTYPEIEBYTHESHAPEOFTHECURVE4HUSTHE TOTALREACTIONORDERMN ISOBVIOUSLYHIGHERTHANORDERNREACTION KINETICS4HISMEANSTHATFORMULATIONSHAVINGREACTIONKINETICSOF ORDERNANDORDERMN MUSTBETREATEDDIFFERENTLYWHENCURECYCLES FOROPTIMUMCOMPOSITEPROCESSINGSCHEDULESAREREQUIRED /RDERNCUREKINETICS $ATAFROM4ABLEANDRESULTSTAKENFROMTHEISOTHERMSOFTHE FORMULATION$'%"!$$3SYSTEMALLOWSCALCULATIONOFTHEKINETIC PARAMETERSTHATAREPRESENTEDIN4ABLE4HESEKINETICPARAMETERS WEREOBTAINEDBYUSINGTHEh)SOTHERMALKINETICSvSOFTWARE )TISOBSERVEDFROMTHERESULTSOF4ABLETHATTHEVALUEOFISO THERMAL $( INCREASES IN MODULE AS ISOTHERMAL CURE TEMPERATURE GOES HIGHER 4HE INCREASE ON ISOTHERMAL REACTION TEMPERATURE FOR EXOTHERMICREACTIONSGENERATESHEATINAHIGHERPROPORTIONTHANTHE HEATGENERATEDONTHEREACTIONITSELF )T IS ALSO VERIlED THAT THE!RRHENIUS CONSTANT RATE K AND THE REACTIONORDERNINCREASESASREACTIONTEMPERATUREGOESHIGHER4HE INCREASE IN REACTION TEMPERATURE CAUSES A DISTINCT DISTRIBUTION OF MOLECULESPEEDSANDENERGIES FOLLOWEDBYANINCREASEINTHEAVER AGEVALUEOFENERGYFROMREACTANTMOLECULES!SACONSEQUENCEA LARGERNUMBEROFMOLECULESHAVEENOUGHENERGYTHROUGHCOLLISION TOSURPASSTHEACTIVATIONBARRIERANDCONSEQUENTLYTHEREACTIONRATE MAYINCREASE 4HERESULTSFROMISOTHERMALRUNSALLOWOBTAININGTHEVALUESOF THEREACTIONRATESANDTHECONVERSION&IGURESHOWSTHEREACTION RATEFROMEACHISOTHERMREACTIONTEMPERATURETHATWASOBTAINEDAS FUNCTIONOFTHEREACTIONTIMEFOR$'%"!$$3SYSTEM4HEREISA MAXIMUMOFREACTIONRATEFOREACHISOTHERMREACTIONTEMPERATURE &IGUREPRESENTSTHEREACTIONRATEDADT ASAFUNCTIONOFCONVER SION A WHERE IT IS CLEAR A MAXIMUM AT ^ CONVERSION FOR ALL ISOTHERMALREACTIONTEMPERATURES4HISMAXIMUMCONVERTIONFORTHE ISOTHERMSISRELATEDTOTHEMECHANISMSFORBOTHREACTIONORDERNAND FORTHEAUTOCATALYTICREACTIONORDER4HEREFOREFOR$'%"!$$3 SYSTEMTHEPLOTSFROM&IGURESANDCONlRMTHEREACTIONORDERN PREVIOUSLYFOUND 0LOTSFROM&IGURESANDSHOWALSOTHATINGENERALTHEDADT VALUEREACHESAMAXIMUMATADElNITETIMEANDORDElNITECONVERSION )NTHEPLOTOF&IGUREITISVERIlEDTHATTEMPERATUREHASAPRONOUNCED INmUENCEONTHEREACTIONRATE!TLOWERTEMPERATURES^—# THE CURVEHASASMALLERSLOPETHANATHIGHERTEMPERATURESANDTHEREAC &IGURE4YPICALCUREISOTHERMSAT—#SHOWINGNORDERREACTIONMECHA NISMFORTHESYSTEM$'%"!$$3 &IGURE)SOTHERMALREACTIONRATEASAFUNCTIONOFREACTIONTIMEAT—# —#—#AND—#FORTHESYSTEM$'%"!$$3 7DEOH5HVXOWVIRULVRWKHUPDOHQWKDOSLHV$+LVRDQGNLQHWLFSDUDPHWHUVN DQGQIURPWKHIRUPXODWLRQV\VWHP'*(%$''6 7& &IGURE4YPICALISOTHERMCURVESHOWINGAUTOCATALYTICMECHANISMOFREAC TIONFORTHEFORMULATION$'%"!$$-     $+LVR-J     K4         N      0DWHULDOV5HVHDUFK &RVWDHWDO TIONTAKESMORETIMETOREACHTHEMAXIMUMCONVERSIONRATEDADT  !THIGHERTEMPERATURES^ —# THECURVEBECOMESSTEEPER INTHEBEGINNINGOFTHEREACTIONANDREACHESTHEMAXIMUMREACTION RATE 4HEREFORE AT THE BEGINING OF COMPOSITE PROCESSING SMALLER TEMPERATURESAREDESIRABLEONCETHEYHELPANADEQUATEPREPREGHAN DLINGMOULDINGANDCURECONTROL4HISAVOIDSUNDESIRABLEFAST UN CONTROLLEDREACTIONSWHICHCANCOMPROMISEQUALITYANDPROPERTIES OFTHEPRODUCT &IGURE  CONlRMS THE OBSERVATIONS TAKEN FROM &IGURE  4HE $'%"!$$3SYSTEMHASMAXIMUMCONVERSIONAROUND!C CORDINGTO%QUATION WHENCONVERSIONA ISEQUALTOZEROTHEK REACTIONRATECONSTANT VALUECANBEFOUNDFROMPLOTSOFDADTASA FUNCTIONOFTIMEORASFUNCTIONOFCONVERSIONIE >LIA WKXVGAGW N@ (OWEVERFROMCHEMISTRYPOINTOFVIEWSUCHCONSIDERATIONISNOT VALIDSINCETHEREISNOREACTIONATAZEROCONVERSIONANDTHEREFORE THEREISNOREACTIONRATECONSTANT#OMPARINGTHESEDATAWITHTHEK VALUESFROM4ABLEITISVERIlEDTHATBOTHAREOFTHESAMEORDEROF MAGNITUDE &IGURESHOWSTHE!RRHENIUSPLOTLNKVS4 FOR$'%"!$$3 FORMULATION4HECURVEREPRESENTSTHEACTIVATIONENERGYANDTHEVALUE FOUNDISK*MOL !CCORDINGTOTHELITERATURECHEMICALREACTIONS HAVEACTIVATIONENERGIESINBETWEENANDK*MOL 4HEACTI VATIONENERGYOFVERYVISCOUSSYSTEMSISSMALLER K*MOL  4HEREFORETHEVALUEOFACTIVATIONENERGYFOR$'%"!$$3SYSTEM AGREEDWITHTHEVALUESFOUNDINLITERATURE  -ECHANISMOF!UTOCATALYTIC#URE 4ABLESHOWSRESULTSFOR$'%"!$$-FORMULATIONOBTAINEDBY ISOTHERMALREACTIONRUNS4HEDATAWERECALCULATEDBYTHEh)SOTHERMAL KINETICSvSOFTWARE )T IS OBSERVED THAT AS FOR THE $'%"!$$- SYSTEM THE ISO THERMAL$(THERATECONSTANTANDTHEKINETICEXPONENTNINCREASE PROPORTIONALLYASAFUNCTIONOFTEMPERATURE4HENAHIGHERNUMBEROF MOLECULESACQUIRESENOUGHENERGYFORCOLLISIONREACHINGTHEREACTION ACTIVATIONBARRIERANDCONSEQUENTLYINCREASINGTHEREACTIONRATE /NTHEOTHERHANDTHEKINETICEXPONENTMDECREASESASTEMPERATURE INCREASEDUETOTHEEFFECTOFTHETHERMALCATALYSISSUPERSEDINGTHE AUTOCATALYTICEFFECTOFM&IGUREILLUSTRATESTHEVARIATIONOFMAND NWITHTHETEMPERATURE )TCANBEVERIlEDIN&IGURETHATAT—#THEKINETICEXPONENTS MANDNHAVETHESAMEVALUEMN 4HISMEANSTHATATTHE EARLYBEGINNINGOFTHEPOLYMERIZATIONREACTIONTHEAUTOCATALYTICEFFECT ISTHESAMEASTHETHERMALEFFECT/NTHEOTHERHANDTHEVALUEOFM DECREASESASCURETEMPERATUREINCREASESAPPROACHINGZEROWHENTHE TEMPERATUREREACHESNEARLY—#)TSHOULDBENOTEDTHATAVALUE NEARLYCONSTANTFORTHETOTALREACTIONORDERMN ISOBTAINED THROUGHOUT THE POLYMERIZATION REACTION WITH N CORRESPONDING TO NEARLYANDMTOOFTHETOTALREACTIONORDER 4HEISOTHERMALREACTIONRATEASFUNCTIONOFTIMEOBTAINEDFORTHE $'%"!$$-AUTOCATALYTICSYSTEMISSHOWNIN&IGURESAND4HE CONVERSIONAISALSOSHOWN%ACHCUREISOTHERMHASAMAXIMUMAT THEDADTPARAMETERWHICHISTYPICALFORANAUTOCATALYTICMECHANISM OFNORDER)NTHISCASETHECURVESAREMOREDElNEDTHATTHEONES SHOWNIN&IGURESANDACCORDINGTOPREVIOUSRESULTSPRESENTED BY3EFERIS &IGURESANDALSOSHOWTHEINmUENCEOFTHETEMPERATUREONTHE REACTIONRATE4HECURVEOBTAINEDATTHELOWESTTEMPERATURE—# PRESENTSTHELOWESTSLOPEANDTHEREACTIONTAKESLONGERTOREACHTHE MAXIMUMCONVERSIONRATEDADT !STEMPERATUREINCREASES^ —# THECURVESBECOMESTEEPERREACHINGTHEMAXIMUMREACTION RATEINASHORTTIME4HEREFOREINORDERTOGETATIGHTCONTROLOFTHE POLYMERIZATIONREACTIONDURINGCOMPOSITEPROCESSINGITISADVISABLE TOUSELOWERTEMPERATURESINTHEBEGINNINGOFTHECURECYCLE4HIS PREVENTS UNCONTROLLED REACTIONS WHICH COULD LEAD TO A COMPOSITE HAVINGPOORMECHANICALPROPERTIES 4HE MAXIMUM REACTION RATE OCCURS AT NEARLY  OF CONVER SION&IGURE SUGGESTINGTHATWHENTHECUREREACTIONREACHESITS 7DEOH5HVXOWVRIHQWKDOS\RIWKHLVRWKHUPV$+LVRDQGNLQHWLFSDUDPHWHUV NQDQGPRIWKH'*(%$''0V\VWHP 7—&     $+LVR -J     K4 N M                   —# —# —# —#  %K*MOL     LNK4 DADT                    A &IGURE)SOTHERMALREACTIONRATEASAFUNCTIONOFTHECONVERSIONAT—# —#—#AND—#FORTHESYSTEM$'%"!$$3     4+    &IGURE !RRHENIUS PLOT OF THE ISOTHERMAL REACTION RATE CONSTANTS FOR THE $'%"!$$3SYSTEMS 9RO1R  )NmUENCEOF!ROMATIC!MINE(ARDENERSINTHE#URE+INETICSOFAN%POXY2ESIN5SEDIN!DVANCED#OMPOSITES  N M  +INETICSEXPOENTSNM   NM 4—#       4—#           4EMPERATURE—# )LJXUH(IIHFWRIWKHWHPSHUDWXUHRQWKHNLQHWLFH[SRHQWVPDQGQRIWKH '*(%$''0V\VWHP )LJXUH  ,VRWKHUPDO UHDFWLRQ UDWH YV FRQYHUVLRQ A IRU WKH '*(%$''6 V\VWHP   —# —# —# —#   %K*MOL   LNK4 DADT                       4+  4IMES )LJXUH,VRWKHUPDOUHDFWLRQUDWHYVWLPHIRUWKH'*(%$''0V\VWHP )LJXUH$UUKHQLXVSORWIRUWKH'*(%$''0V\VWHP HIGHESTCONVERSIONRATEOFTHETOTALEPOXYGROUPSHAVEALREADY BEENCONSUMED &IGURESHOWSTHEACTIVATIONENERGYOBTAINEDFROMTHESLOPEOF THE!RRHENIUSPLOTOFLNKASAFUNCTIONOFINVERSEABSOLUTETEMPERA TURE4 4HEVALUEOFK*MOL WASOBTAINEDFORTHEACTIVATION ENERGYWHICHISWITHINTHERANGEOF K*MOL USUALLYFOUND INTHELITERATURE  4HE $'%"!$$- FORMULATION HAS A REACTION ORDER M N HIGHERTHANTHE$'%"!$$3FORMULATIONANDASACONSEQUENCE AHIGHERREACTIONRATE4HISMEANSTHATDURINGTHEPREPREGPREPARA TIONWITH$$-ISNECESSARYTOCARRYOUTAVERYTIGHTCONTROLOFTHE CURECYCLE 4HEISOTHERMSHAPESARERELATEDTOTHEREACTIONORDERFOREACH FORMULATION4HEWELL DElNEDISOTHERMSOBTAINEDWITHTHE$'%"! $$-FORMULATIONSARECHARACTERISTICSOFANAUTOCATALYTICREACTION /NTHEOTHERHANDWITHTHE$'%"!$$3FORMULATIONSTHEISOTHERMS AREFORMEDNEARLYTHEZEROTIMEWITHOUTDElNITIONINDICATINGREAC TIONOFORDERN 4HEACTIVATIONENERGYOFBOTH$'%"!$$-AND$'%"!$$3 REACTIONSAREVERYCLOSETOEACHOTHERANDWITHINTHERANGEFOUND INTHELITERATURE #ONCLUSION 4HEPOLYMERIZATIONTEMPERATUREFORTHE$'%"!$$-MIXTURE ISLOWERTHANFORTHE$'%"!$$3SYSTEM4HE$$-CURINGAGENT HASALOWERMELTINGPOINTTHAN$$3ANDCONSEQUENTLYLESSENERGY IS REQUIRED TO MELT AND START THE POLYMERIZATION REACTION "ESIDES THATTHERELATIVEREACTIVITIESOFTHE$$3AND$$-CURINGAGENTARE DIFFERENTDUETOTHEDIFFERENCESELECTRONDENSITYOFTWOMOLECULES $$3SHOULDBELESSREACTIVESINCETHESULFONEMOIETYWILLPULLELECTRON DENSITYAWAYFROMTHEAMINEGROUPSWHEREASTHEMETHANEMOIETY IN$$-WILLNOT !CKNOWLEDGMENTS 4HEAUTHORSACKNOWLEDGETHElNANCIALSUPPORTRECEIVEDRESPEC TIVELYFROM&!0%30UNDERGRANT AND#.0Q  &RVWDHWDO 2EFERENCES  ,EE3-EDITOR)NTERNATIONAL%NCYCLOPEDIAOF#OMPOSITESV6#( 0UBLISHERS.EW9ORK  #HOU47EDITOR0OLYMERMATRIXCOMPOSITESINSTRUCTUREANDPROPER TIESOFCOMPOSITESV-ATERIAL3CIENCEAND4ECHNOLOGY3ERIES6#( 0UBLISHERS.EW9ORK 0DWHULDOV5HVHDUFK  3HIN $$ (AHN ( 4! CONSISTENT CURE KINETIC MODEL FOR!3 GRAPHITEEPOXY#OMPOSITES0ART!    6ARLEY2*(ODGKIN*((AWTHORNE$'3IMON'0-C#ULLOCH$ 4OUGHENINGOFATRIFUNCTIONALEPOXYSYSTEM0ART)))+INETICANDMORPHO LOGICALSTUDYOFTHETHERMOPLASTICMODIlEDCUREPROCESS0OLYMER     %NGINEERED-ATERIALS(ANDBOOK6OL#OMPOSITE53!#HAPMANAND (ALL  :VETKOV6,#OMPARATIVE$3#KINETICSOFTHEREACTIONOF$'%"!WITH AROMATIC DIAMINES ) ON ISOTHERMAL KINETIC STUDY OF THE REACTION OF $'%"!WITHM PHENYLENEDIAMINE0OLYMER    #OSTA-,%STABLISHINGOFPROCESSPARAMETERSOFSTRUCTURALCOMPOSITES BYTHERMALANDVISCOSIMETRICANALYSES3áO*OS£DOS#AMPOS)NSTITUTO 4ECNOL˜GICODE!ERONÕUTICA  "ASICSFORMULATIONSWITHEPOXYRESINS$OW$OW3!4ECHNICAL "ULLETINP  *ANG7!REVIEWOF$3#KINETICSMETHODS53!$U0ONT)NSTRUMENTS   4HE 0ERKIN %LMER #ORPORATION /PERATING )NSTRUCTION FOR THE $3#  )SOTHERMAL+INETICS3OFTWARE+IT  "ERGLUND ,! 0ROCESSING 3CIENCE FOR (IGH 0ERFORMANCE 4HERMOSET #OMPOSITES3AMPE*OURNAL    AM*3EFERIS*#!PPLICATIONOFTHEKINETICCOMPOSITEMETHODOLOGYTO AUTOCATALYTIC TYPETHERMOSETPREPREGCURES*OURNALOF!PPLIED0OLYMER 3CIENCE    #OSTA-,2EZENDE-#0ARDINI,#-£TODOSDEESTUDODACIN£TICADE CURADERESINASEPXI0OLÔMEROS#IóNCIAE4ECNOLOGIA   "YRNE#!(AGNAUER',3CHNEIDER.3,ENZ270OLYMER#OMPOSITES   4URI%EDITOR4HERMALCHARACTERIZATIONOFPOLYMERICMATERIALS!CADEMIC 0RESS53!  3TUTZ ( -ERTES * EUBECKER + ,IFETIME ASSESSMENT OF EPOXIES BY THEKINETICSOFTHERMALDEGRADATION*OURNALOF0OLYMER3CIENCE     /ZAWA4*OURNALOF4HERMAL!NALYSESAND#ALORIMETRIC   -AY#!%POXYRESINSCHEMISTRYANDTECHNOLOGY7ATSONVILLE#!-ARCEL $EKKER  #OSTA-,2EZENDE-#0ARDINI,#%STUDODAINmUãNCIADODILUENTE REATIVO0'%NACIN£TICADECURADERESINAEP˜XIUTILIZADAEMCOMP˜SITOS ESTRUTURAIS1UÔMICA.OVA    #OSTA-,0ARDINI,#2EZENDE-#!VALIAẵỏO4ÊRMICAE2EOLGICADO #ICLODE#URADO0RÊ IMPREGNADODE#ARBONO%PXI0OLÔMEROS#IóNCIA E4ECNOLOGIA    'HAEMY - 2IAHY -( +INETICS OF ANHYDRIDE AND POLYAMIDE CURING OF BISPHENOL! BASED DIGLYCIDYL ETHER USING $3# %UROPEAN 0OLYMER *OURNAL    "UGGY-4EMIMHAN4"RADDELL/#URINGOFCARBONlBREREINFORCED EPOXYMATRIXCOMPOSITES*OURNALOF-ATERIALS0ROCESSING4ECHNOLOGY      (AYES " 3 'ILBERT %  3EFERIS * # 3CALING COMPLICATIONS OF DUAL TEMPERATURE CURE RESIN PREPREG SYSTEMS IN AIRPLANE PART MANUFACTURE #OMPOSITES0ART!    -IRANDA-)'4OMEDI#"ICA)$3AMIOS$!DSCKINETICSTUDY ONTHEEFFECTOFlLLERCONCENTRATIONONCROSSLINKINGOFDIGLYCIDYLETHER OF BISPHENOL ! WITH  DIAMINODIPHENYLMETHANE 0OLYMER      -IRANDA-)'3AMIOS$!NALYSIS!ND#OMPARISON/F4HE"ARRETT &REEMAN #ARROL!ND4HE4IME 4EMPERATURE 4RANSFORMATION 4TT 3U PERPOSITION-ETHODS4HE#ASE/F!(IGH4G$IAMINE%POXY3YSTEM %UROPEAN0OLYMER*OURNAL    3YKORA63PACEK6$OBAS)4HEEIGHTHINTERNATIONALSYMPOSIUMON POLYMER ANALYSIS AND CHARACTERIZATION )30!#  -AY    3ANIBEL)SLAND&LORIDA53!*OURNALOF!PPLIED0OLYMER3CIENCE    3OUROR3+AMAL-2$IFFERENTIALSCANNINGCALORIMETRYOFEPOXYCURE ISOTHERMALCUREKINETICS4HERMOCHIMICA!CTA     &LICK%7%POXY2ESIN#URING!GENTS#OMPOUNDSAND-ODIlERSAN )NDUSTRIAL'UIDESECONDED53!.OYES0UBLICATIONP  %LLIS"#HEMISTRYAND4ECHNOLOGYOF%POXY2ESINS53!#HAPMANAND (ALL53!P ... STUDY THE CURE KINETICANDHASASEXAMPLEHOW AROMATIC AMINE HARDENERS INmUENCE THE CURE KINETICS OF AN EPOXY RESIN USED IN ADVANCED COMPOSITES 4HEINVESTIGATIONWASCARRIEDOUTBYUSING THE $3#TECHNIQUEANDITWASFOUND THATDEPENDINGON THE SYSTEM USED THE CURE KINETICS OF THE FORMULATIONOBEYSORDERNORAUTOCATALYTICORDER... CALORIMETRY$3# 4HEUNDERSTANDING OF THE CURE KINETICS THATWILL DELINEATE THE CURE CYCLETOBE USED IN THE PROCESSING OF PREPREGSIS OF FUNDAMENTALIMPORTANCEFORGOODQUALITY ADVANCED COMPOSITES 4HE CURE KINETICS CANBEFOLLOWEDBYUSINGTWO$3#METHODSDYNAMIC... HASTOKNOW IN DEEP THE CURE KINETICS OF MATRIXWHICHHELD THE lBERSTOGETHER4HISWORKDESCRIBESAPROCEDURETO STUDY THE CURE KINETICANDHASASEXAMPLEHOW AROMATIC AMINE HARDENERS INmUENCE THE CURE KINETICS OF AN EPOXY