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Preparation,

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Preparation,

    Preparation,

    CHEM.RES.CHINESEUNIVERSITIES2010,26(5),85l856

    Preparation,CuringReactivityandThermalPropertiesof

    Titanium-dopedSiliconeResins

    WANGXue.mei,WUYa.hong,HAOZhi.feng,YUJianandYULin

    FacultyofChemicalEngineeringandLightIndustry,GuangdongUniversityof Technology,Guangzhou510006,PR.China

    AbstractNeveltitanium.dopedsiliconeresinsweresynthesizedfromlow-costsilanemonomersandtetrabuty1ti-

    tanateasrawmaterialsandhydrochloricacidascatalyst.withtitaniumelementasdopantintoprincipalchainOf

    Si.O.Si.TheresinswerecharacterizedbymeansofFTIR.HNMRand"CNMRspectra,

    eirthermalproperties

    andcuringpropertieswereinvestigatedandtheircorrespondingfilmsweredetermined.Theresultsshowthatthe

    thermalstabilityandstoragestabilityoftheresinswereinfluencedbythetypesofsilanemonomerscontainingdif-

    ferentcarbonatomicitiesoforganicgroup.Thethermalstabilityofthetitanium

    dopedsiliconeresinwithamolarra-

    tioofsilanemonomerB(n-propyltriethoxysilane)tosilanemonomerC(n-octyltriethoxysilane)being1:1issuperior

    tothatoftheresinwithamolarratioofsilanemonomerBtosilanemonomerCbeing1:3.However,thestoragesta-

    bilityoftheformerisinferiortothatofthelatter.Thisworkalsoshowedthattl1esynthesizedtitaniumdopedsilicone

    resinshavethehiestthermalstabilityupto450

    500.Cwithanatomicitymolarratioof1:4oftitaniumtosilicon

inthereactants.ButthebeststoragestabilityOfmeresinpreparedfromthereactantswithanato

    micitymolarratioof

    1:6(Ti):,z(Si)

    wasobtained.Theeffectofthetypeandcontentofcuringagentonthecuringpropertiesofthere

    sin

    wasalsostudied.Moreover,thermalmechanismandcuringmechanismwereproposedinthis

    work.

    KeywordsTitanium.dopedsiliconeresin;Synthesis;Thermalstability;Curing;Mechanism

    ArticleID1005.9040(2010,.05.851.06

    1lntroduction

    Siliconeresinshavebroadapplicationinindustry, becausetheyareofexcellentthermalresistancedueto thehighbondingenergyoftheprincipalchainof Si-OSi.Thesiliconeresinvarnishmaygenerallybear atemperatureof2OO250.C.Usuallyatempe

    ratureof200.Corhigheroneisnecessarytocure siliconeresinswithlongcuringtime.Thehighcuring temperatureandlongcuringtimecauseproblemsin energyconsumptionandequipmentrequirementfor processing.Moreover,inmanycases,thepropertiesof theproductsaredefectivesuchaspooradhesiontothe substrate[1-31.

    Greateffortshavebeenmadetoreducethecu

    ringtemperatureofsiliconeresins.Organicaminesin combinationwithsolublemetalsaltsareusedasaddi

    tives.However,thesecombinedcatalystsmayimpair theheatresistanceofthesiliconeresincoatingsto varyingdegrees.Inaddition,ethylenediamineand polyethyleneiminehavebeenproposedtobeusedas

curingagentsofsiliconeresins.Theyenablethesili

    coneresinstocureat15O.Cin30minwithoutaf- fectingtheirthermalstabilities.Nevertheless.thetoxic by..productssuchasethylenediaminewouldbelibe.- ratedduringthecuringprocessI.

    Todate.mostheat.resistantsiliconeresinscon- tainphenylgroupsinthebranchedchainsbecausethe

    highphenylcontentcanenhancethethermalstability andelongatethethermalagingtime.However,phenyl chlorosilaneorphenylalkoxylsilaneasrawmaterials inthesynthesisofpheny1.dopedsiliconeresinsare expensive,whichresultsinhighcostsintheprepara

    tionofheat.resistantsiliconresins.Therefore.thede

    velopmentofheat.resistantsiliconeresinswith low-costandhighcuringactivityiscurrentlyanim-? portantdirectioninthisfield.

    Inordertoimprovethethermalstabilityofsili

    coneresins,titaniumelementwasusedasdopantinto principalchainofSi--O--Sibecauseofthehighbonding energyofTiO.Therearequitefewreportsaboutthe synthesisroutesandmethodsofSi.O-Ticompounds. andevenmuchfeweronesaboutthepracticalapplica- tionofthemtocoatingindustry.Wangpjustonly Correspondingauthor.E-mail:haozhi~ng3377@163.com ReceivedSeptember14,2009;acceptedNovember20,2009. SupportedbytheScienceandTechnologyProjectofGuangdongProvince,China(No.2009B

    011000012)

    852CHEM.RES.CHINESEUNIVERSITIESVlo1.26 introducedfourtheoreticalmethodsaboutthesynthe- sisofSi.o-1'|compounds.Moreover,therelated

    researchesoftitanium.dopedcompoundswere focusediustonthesynthesesofSiTiCOfibers.J

    andTiO2-SiO,so1-gelfilms【一10_

    Wleusedthelow.costsilanemonomersasraw materia1insteadofpheny1.silanemonomers.Inaddi

    tion.titaniumwasdopedintotheprincipalchainof Si.oSiwithtetrabutyltitanateasrawmaterialwhich ismuchcheaperthanpheny1.silaneandcanimprove theheatresistanceofsyntheticresin.Moreover,the curingactivityofsyntheticresinwasincreasedgreatly, astetrabuty1titanatehadbeenusedascuringagent. 2Experimental

    2.1Materials

    SilanemonomerswerepurchasedfromGuang

    zhouJCZYorganicsiliconeCo.,Chinaandusedas received.Absolutealcohol,nbutanol,xylene,tetra-

    buryltitanateandhydrochloricacidwerepurchased fromGuangzhouHuaxininstrumentCo..Chinaand usedasreceived.

    2.2Charaeterization

    Fouriertransforminfraredspectra(FTIR1were recordedonaNicoletMagna380Fouriertransform infraredspectrometer.Solution'Hand"CNMR spectraweremeasuredonarian$400spectro

    meteratroomtemperaturewithtetramethylsi

    lane(TMS)astheinternalstandard.Thermogravime- tricanalysis(TGA)anddifferentia1thermalanalysis rDTA)wereperformedonaNetzschSTA409PC thermogravimetricanalyzerundernitrogengas(40 mL/min)ataheatingrateof10.C/min.Ge1Permea-

tionChromatography(GPC)wasperformedona

    tersl515gelpermeationchromatograph.

    2.3SynthesisofSiliconeResin

    2.3.1Hy&dysiSofSilaneMonomerandTetrabutyl ~tanate

    Areactionmixtureofsilane,absolutealcoholand hydrochloricacidwasloadedintoa250mL

    four-neckedflaskequippedwithamechanicalstirrer, awatercondenser,athermometer,andafunne1.The mixturewasvigorouslystirredandheatedto65.C, and6mLdeionizedwaterwasaddeddropwisetothe stirredmixtureinabout20min.Aftertheaddition,the reactionsolutionwaskeptisothermallyat65.Cand stirredfor2h.Asolutionoftetrabutyltitanatediluted withanhydrousxylenewasaddeddropwisetothe flaskin30min.Then0.83mLofdeionizedwaterwas addeddropwisetothestirredmixture.Thereaction mixturewaskeptrefluxingfor1hat65.C.thenthe hydrolysatewasobtained.

    23.2Polvcondensation

    Titanium.dopedsiliconeresinwaspreparedfrom thecondensationreactionwhichwascarriedoutina 250mLthree.neckedflaskequippedwithathermo- meter,acapillary,andadistillationsystemconnected toavacuum.Thehydrolysatewasdistilledunderva

    chumtoremovetheethano1andxylenewhenthe reactionmixturereached60lo0.C,andheatedup

    to120140.Cf0r30mintogiveacanaryyellow

    transparentviscousliquidwhichwascalledtita- nium-dopedsiliconeresin.

2.4PreparationandPropertiesofFilm

    Asolutionoftitanium.dopedsiliconeresinin .

    butanolwasmixedwithagivenamountofcuring agent.Thefilmwasmadebycastingthesolutiononto tinplateplatesonErichsenapplicator.Drynessdegrees ofthefilmcuredatroomtemperature(25.C1and 100.Cweredeterminedatevery5min.Aftercuring, titanium.dopedsiliconeresinfilmswithathicknessof 25100gmwereobtained.

    HardnesswasdeterminedonaQHQpencil

    scratchhardnesstesteraccordingtoGB/T6739?1996. AdhesionofthefilmwastestedonaQFZcoatingad- hesiontesteraccordingtoGB172079(89).Theim-

    pactresistanceonfilmswasdeterminedonaQCJ ImpactFlexibilityTester.

    3ResultsandDiscussion

    Inthiswork.thenoveltitanium-dopedsilicone resinswerepreparedandtheirthcrnlalpropertiesand curingsystemswereinvestigated.Themeanmolecu- larweightofthetitaniumdopedsiliconeresinswasin

    arangeof3180--3550,whichwasdeterminedby GPC.Thechemicalstructureoftitanium-dopedsili- coneresinsisshowninScheme1.

    ,

    Ill

    i.Si--OT

    i

    O

    0HOH

    Si,AAA/V'

    I

    

    si0Si),wf

    0C|{2CH3

    Scheme1Chemicalstructureoftitaniumdoped

    siliconeresins

    NO.5WANGXue.meietal853

    3.1StructuralCharacterization Thechemicalstructureoftitanium.doped siliconeresinwascharacterizedbymeansofFTIR,

    HNMRand"CNMRspectroscopy.

    Fig.1showstheFTIRspectraoftitaniumdoped

    siliconeresin(curve)andpuresiliconeresin(curve,

    inwhichtheabsorptionsfortheOHstretching

    vibrationsofSi0Hcanbeobservedatabout3400 cm(.Theabsorptionbandsat28502980cm

    fromSi(CH2CH3wereobserved.Thecharacte

    risticabsorptionsfortheSioSilinkageofsilo

    xaneweredetectedintheregion0f1050ll3Ocm(.

    MoreoveLasshowninFig.1curvea.anewabsorp

    tionpedkappearsat923cm-,whichconfirmsthe presence0fSiOTibondingii.

    40003500300025002000l500l000500 /cm

    Fig.1FTIRspectraoftitanium-dopedsilicone resin(a)andpuresiliconeresin(b)

HNMR(CDC13),:3.72(t,2H,oH),2.69(d,

    2H,OCH2),2.3l(t,3H,CH3),1.59(q,4H,

    --

    SiCH2CH2),1.39(q,8H,CH2),1.26(t,20H,

    

    CH2),0.94(t,4H,--TiCHzCH2),0.88(t,5H,

    TiCCCH2CH3),0.605(s,6H,CH3).

    "CNMR(CDC13),:62.7(d,OCH2),58.0(s,

    

    oCH2CH3),34.7(s,SiCH2),33.1(s,

    --

    SiCH2CH2),31.9[s,Si(CH2)2CH3,22.6[s,

    

    SiCH2CH2(CH2)5,l8.8(s,TiCH2),18.2(s,

    

    TiCH2CH2),17.7[s,TiCH2CH2CH2],l6.4[s,

    

    Ti(CH2)3CH3,13.8[d,Si(CH2)7CH3.

    3.2ThermalandCuringProperties

    3.2.1lnfluenceofSilaneMonomersBandConthe PropertiesofResin

    Thefirstimportantfactorthatinfluencesthe thermalstabilityofsiliconeresinisthetyDeOfsilane monomerwhosestructureisshowninScheme2.Two silanemonomers(silaneBandsilaneC,werechosen accordingtothestoragestabilityofsyntheticresin. ThesiliconeresinswiththemolarratiosOf1:1.1:2 andl:3OfsilaneBtosilaneChavebeensynthesized. Thermogravimetricanalysisshowsthattheircorres-

    pondingmaximumdecompositionratesoftheresins withdirentmolarratioswere490.C.450.Cand 451.C.Theweightretentionpercentagesat800.C respectivelyamountto36.56%.32.83%and3l-38%. Theobservedresultisconsistentwimthetheoryof inductiveeffect[12.becausetheelectron.releasingin

    ductiveeffectofthesiliconatomincreasestheelec- trondensityofalkylchainandthushindersthebreak-

    Cbond(Scheme21.HoweveLthein- ingoftheC

    ductiveeffectissignificantforashortchain(e.g.1ess thanthreecarbonatoms)andsuchakindofect

    sharplyweakensalongthecarbonchain.Obviously, thenumberofthecarbonatomsinsilaneBwas smallerthanthatinsilaneC.whichmeansthethermal stabi1itVofsilaneBisbetterthanthatofC.andthe lesssilaneCusedasstartingmateria1.thebe~erthe thermalstabilitVOfresin.

    R

    I

    CH3CH20Si0CH2CH3

    l

    OCH:CH

    Scheme2Chemicalstructureofsilanemonomer R=CH7orCsHI7.

    However,siliconeresinswithamolarratioOfl:l orl:2OfBtOCwereunstableandwouldturntogelin aweekintheprocessofpreservation.Theresinwitha molarratioOfl:3OfBtOChasthelong-termstorage stability.Thereasonispossiblytheexistenceofsteric hindrance03].andalongeralkylchainofsilaneCmay

    hindertheglasstransitionofsyntheticresin.Conse. quentl~thesiliconeresinwithflmolarratioOfl:3 waschosentostudyitsthermalstabilityandstorage stability.

    32.2InfluenceofTitaniumContent

    Theefrectoftitaniumincorporationonthether

    malstabilityofsiliconeresinwasinvestigatedby thermogravimetricanalysis(TGA).Inordertostudy thethermalstabilitv.thetitaniumdopedsilicone

    resinswithamolarratioOfl:20,l:l0,1:8,1:6,1:5, l:4.1:3orl:2ofTitoSi(themolarratiomeansmolar ratiooftitaniumatomsfromtetrabuty1titanateand siliconatomsfromthereactant)weresynthesizedand studied.Fig.2showstheTGAdiagramsofthesilicone resinswithdifferentcontentsoftitaniumdoped.They exhibitverysimilarthermallyoxidativedegradation stabilitV.Nosignificantmasslosebelow450.Cwere observedforthetitaniumdopedsiliconeresinswhich

    indicatesabetterthermalstabilityincomparison withageneralsiliconeresin(200--300.C,anda 854CHEM.RES.CHINESEUN?ERSITIESV_01.26

    phenyldopedsiliconeresin(400.C1一引.TGAdata

    revealthatthesynthesizedresinsareofhightempera

    tureresistanceandmeintroductionofTilinkage (Tiobond)inthepolymerstructurecanimprove thethermalstabilityofsynthesizedresins,which couldbeattributedtoahigherbonddissociation enerOfTiObond[,.

    100

    90

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