Effect of a silane coupling agen

PolymerInternationalPolymInt50:606±611(2001)DOI:10.1002/pi.673Effectofasilanecouplingagentonthe

propertiesofwhitericehuskash–

polypropylene/naturalrubbercomposites

HIsmail,*LMegaandHPSAbdulKhalil

SchoolofIndustrialTechnology,UniversitiSainsMalaysia,11800Minden,Penang,Malaysia

Abstract:Whitericehuskash(WRHA)±polypropylene(PP)/naturalrubber(NR)compositeswerepreparedusingaBrabenderPlasticorderat180°Candarotorspeedof50revminÀ1.Themechanicalandwater-absorptionpropertieswerestudied.TheincorporationofWRHAintothePP/NRmatrixhasresultedintheimprovementofthetensilemodulus;however,thetensilestrength,elongationatbreakandstressatyielddecreasedwithincreasingWRHAloading.Poor®llermatrixinteractionsarebelievedtoberesponsibleforthedecreaseintheproperties.Incorporationofasilanecouplingagent,3-aminopropyltriethoxysilane(3-APE),improvedtensilemodulus,tensilestrengthandstressatyieldofthecomposites.Water-absorptionstudiesindicatethattheuseofthecouplingagentreducedtheamountofwaterabsorbedbythecomposites.#2001SocietyofChemicalIndustry

Keywords:silanecouplingagent;whitericehuskash;polypropylene;naturalrubber;mechanicalpropertiesandwaterabsorption

INTRODUCTION

Thermoplasticelastomer(TPE)isablendofrubberandthermoplasticandmostprobablythefastestgrowingsectorinthepolymermarket.1±3TPEsarematerialswhichcanbemouldedlikeplasticsatappropriateprocessingtemperatures,butwhichretainsomeofthe¯exibilityandresilienceofrubbersatnormaltemperatures.4StudiesonTPEswithvarioustypesofelastomerandpolyole®nhavebeenreportedbymanyresearchers.5±8

Compoundingofcellulosic®llerswiththermoplas-ticsorTPEsincreasesthestiffnessofthecompositesbuttendstoreducestrengthandtoughness.9±11Thepoorstrengthpropertiesresultfromalackofadhesionbetweenthehydrophobicpolymerandhydrophilic®ller.Couplingorcompatibilizingagentshavebeenusedtoimprovedispersion,adhesionandcompat-ibilityforsystemscontainingahydrophiliccelluloseandahydrophobicpolymer.Theseagentsmodi®edtheinterfacebyinteractingwithboththe®breandthepolymer,thusformingalinkbetweenthecompo-nents.12,13

Whenburntintheopenair,thewastefromaricemillyieldedtwotypesof®llers,whitericehuskash(WRHA)andblackricehuskash(BRHA).TheupperlayeroftheRHAmoundwassubjectedtoopenburninginairandyieldedBRHAintheformofacarbonizedlayer,whereastheinnerlayerofthemound,beingsubjectedtoahighertemperature,yieldedWRHA.Inourpreviouswork,14±16wereportedtheuseofWRHAasa®llerfornaturalrubbercompounds.Thisstudyinvestigatestheeffectofacouplingagentand®llerloadingonthemechanicalpropertiesandwaterabsorptionofWRHA-®lledpolypropylene(PP)/naturalrubber(NR)composites.Scanningelectronmicroscopy(SEM)ofthefracturesurfacesofthecompositeshasalsobeencarriedout.EXPERIMENTALMaterialsNR(SMRL)andPPwereobtainedfromtheRubberResearchInstituteofMalaysia(RRIM)andTitanPPPolymers(M)SdnBhd,respectively.The®llerusedwasWRHA,obtainedfromBernasDominals(M)SdnBhdKedah,havingthefollowingcharacteristics:mainparticlesize5.4mm;surfacearea1.4m2gÀ1anddensity2.2gmÀ3.Acouplingagent,3-aminopropyltriethoxysilane(3-APE),wassuppliedbyBumiSainsSelangor,Malaysia.FillertreatmentThecouplingagent3-APEwasdeliveredinliquidform;beforeapplicationitwasdilutedinethanoltomakea20%solution.Theamountof3-APEusedwas1%byweightofthe®ller.The®llerwaschargedintoabench-toptumblermixerandthesolutionwasaddedslowlytoensureuniformdistributionof3-APE.Aftercompletionofthesilaneaddition,the®llerwas*Correspondenceto:HIsmail,SchoolofIndustrialTechnology,UniversitaiSainsMalaysia,11800Minden,Penang,Malaysia

(Received19June2000;revisedversionreceived31October2000;accepted7December2000)

#2001SocietyofChemicalIndustry.PolymInt0959±8103/2001/$30.00606

continuously®llercompletewasthenmixedevaporationdriedforatanother30min.Thetreatedof100the°ethanol.Cforabout5htoallowCompoundingandprocessing

TheBrabenderblendsofPPandNRwereprepareda180mixermeasuringPlasticorderheadmodelPLE331coupledinwitha10min°Cshowsincludingandarotora1minspeed(W50H)atatemperatureofpreheatingof50revminÀ1foraboutthetheformulationusedthroughoutperiod.thisstudy.TableAt1throughendofSamplesa10min,thelaboratoryblendmillwastakenoutandsheetedanoftheblendswerecompressionat2.0mmnipmouldedsetting.inprocedureselectricallyfollowedinvolvedheatedpreheatinghydraulicatpress.180Hotpressture,andbypressingfor4minatthesame°C,fortempera-6mintotalmouldingsubsequenttimewascooling13min.underpressure.TheTesting

TensileD4122mmontestsatensometerwerecarriedM500.outaccordingtoASTMWallacethickwerecutfromthemouldedDumb-bellsheetsspecimenswithawasspecimensuseddieandcutter.Acrossheadspeedof50cmminÀ1eachcase.

weretheusedtestsandweretheperformedaveragewasatcalculated25°C.FiveinWaterabsorptiontest

Thewatercompositebyat30°C.Thesampleswaterwereimmersedindistilledbalanceweighingthesamplesatabsorptionregularintervals.wasdeterminedAMettlerThecalculatedpercentagetypeAJ150by

waterwascontentused,withatanyaprecisiontimet(Mof1mg.t)wasMt??

WwÀWd

d

Â100%

whereafterexposure,respectively.WdandWwareoriginaldryweightandweightMorphologicalstudy

StudiessurfacesonLeicaofthemorphologyofthetensilefracturescope.CambridgethecompositesS-360scanningwerecarriedelectronoutusingaregardingThe®llerobjectivedispersionwastoandobtainbondingsomeinformationmicro-qualitybe-Table1.WRHA-?lledPP/NRblendswithandwithoutasilanecouplingagent,3-APE

IngredientSeries(A)Series(B)PP(%)7070NR(%)30

30

WRHA(%)a0,15,30,45,60

15,30,45,60

3-APE(%)b

±

1

aFillerloadingbasedontotalweightofPPandNR.

b

1%ofacouplingagentwasusedbasedon®ller

weight.

PolymInt50:606±611(2001)Whitericehuskash-polypropylene/naturalrubbercomposites

tweenmicrodefects,if®llerandmatrix,http://wendang.chazidian.comyeronaluminiumendsofgoldtostubsofavoidandtheelectrostaticsputter-speci-RESULTSANDDISCUSSION

Figureandwithouttensile1showsmodulustherelationshipbetween®llerloadingseenWRHAthatthethesilanetensilecouplingofPP/NRmodulusagent,http://wendang.chazidian.compositeswithandincreaseswithItcanbeparticulateloading.electronformTheascan®llerbeusedseenininthisthestudyincreasingisinthemicrographinFig2.AccordingtoNielsen,scanning17inreaseadditionofrigidandstiffparticulate®llerwouldintroductionthemoduluspolymerportedmolecules.ofrestrictionsofthecompositesbecauseoftheMaitiandonthemobilityoftheloadingthefromforincrementiPP/woodin¯ourmodulusSubbarao18composites.withincreasingalsore-Itcanbe®llermodulusFig1thatatasimilar®llerseenAPEofWRHA-®lledPP/NRloadings,thecompositeswithtensile3-3-APE.ishigherAPEmatrixhasThisthanthatofsimilarcompositeswithoutcausedresultindicatesthatthepresenceof3-agentpoortointerfacialasigni®cantmodifythebonding.improvementinthe®llerWRHAWithoutsurfacecharacteristics,anycouplingexpected.wettingoftheparticlesbythePP/NRmatrixisbetweenweaktheThisWRHAgivesriseandtoPP/NRpoorinterfacialmatrix,resultingadhesioninstrengthFigureinterfacial3showsregions.

theeffectof®llerloadingontensilewithoutofdecreases3-APE.WRHA-®lledthesteadilyItascanPP/NRcompositeswithandtheloadingbeseenthattensilestrengthresearcherscomposites.19,20alsoThisreportedisnotofthatsuprising,asWRHAincreasesinincorporationotherof

Figure1.Relationshipbetween?llerloadingandtensilemodulusof

WRHA-?lledPP/NRcompositeswithandwithoutasilanecouplingagent,3-APE.

607

HIsmail,LMega,HPSAbdulKhalil

Figure2.ScanningelectronmicrographofWRHA(magni?cation2000Â

).

Figure3.Tensilemodulusversus?llerloadingofWRHA-?lledPP/NRcompositeswithandwithoutasilanecouplingagent,

3-APE.

®llerincreaseintotheandthetensilepolymerstrengthmatrixofamaycomposite.notnecessarilyMansonculate-®lledSperling21causecomposites,discontinuityandNielsen17reportedisthatcreatedinparti-interphaseofpoorerationandthisstressgeneratestransferatthe®llerpolymerbe-polymerofthe®llerparticlesweakandstructure.dewettingAgglom-ofthecreatingirregularstressattheconcentrationinterphaseaggravatepoints.WRHAthesituation®llersarebyeffectiveItcanbeandtheinseenformagglomeratesasshowninFig2.increasingalsointheFig3thattheuseof3-APEisincreasingtensilestrengthstillshowstensileadecreasingstrength.trendHowever,withparticulateWRHASubbarao18®llersandloading.wasalsoThisreportedsituationbyisnormalforenhancingTheuseofforacouplingiPP/wood¯ourcomposites.

Maitiandofhydrophobicsystemstheagentwasproveneffectiveinconsistingdispersion,adhesionofandcompatibilityinteractionmatrix.Withathehydrophilicuseofcoupling®llerandagent,amodi®cationbetweenofthepolymercomponents®lleroccurredinterphase.through22Ac-608

cordingabouttoRozmanetal,23theinteractionisgroupsbysurface,andand(i)thehydrogenbondingbetweenthebroughtsilanolbetweentheremaining(ii)ahydroxylvanchaindergroupsWaalsoflignocellulosicofsilanetypeandofinteractionPP/NR.atFigureIncorporationbreak4Eshowstherelationshipbetweenelongationbandpolymerof®llers®llerthatloadingofthecomposites.alignmentmatrixincreased,moreprocessseemsofthetochains.causehavepoorWheninterruptionadhesiontothe®llerloadingintheis®llerBecausesurfaceinterfacialcracksandweaktraveltheinterfacialregionsbetweenthemorePP/NReasilymatrixthrougharetheformed.degreeFigureofexhibit4elongationregions,thecompositesfractureataweakerloweralsoshowswiththatincreasingcomposites®llercontent.19APE.lowerEwith3-APEbvaluesthanthecompositesAPEstrengthhasAsdiscussedbefore,themodi®cationwithoutwith3-3-rigidity,theofincreasedthecomposites.thetensileWithmodulusandtensilequentlytheductilityofcompositesthedecreases;enhancementconse-inhaveFigureThisbetter5compositesshowsyieldstressthatbreaktheatlowerelongation.thancompositescompositeswithwithout3-APEit.6surfacesandobservation7.canbeexplainedbyreferringtoFigsweightofFigure6and7showthetensilefracturedispersionof®llerWRHA-®lledeffects,suchof®llers(magni®cationsPP/NRgivesrise400compositesÂand700Âat).Poor15%manceprocessinginservice,poorasreducedproducttocertainlife,poordetrimentalperfor-surfacescharacteristics.product24ItcanappreancebeandpooragglomeratesexhibitpoordispersionandunwettedseenthatWRHAboth®llergoodmeansinthePP/NRmatrix.ThepolarityoftheNRtherecomposites.®ller±matrixthatitisobviouslynotcapableofformingaHowever,ininteractionthewithpresencethenon-polarofPP/bondingisanbetweenindicationthe®llerofimprovementandPP/NR

composites,as

ininterfacial3-APE,Figure4.ElongationatbreakEbversus?llerloadingofWRHA-?lledPP/NRcompositeswithandwithoutasilanecouplingagent,3-APE.

PolymInt50:606±611(2001)

Figure5.Yieldstressversus?llerloadingofWRHA-?lledPP/NRcompositeswithandwithoutasilanecouplingagent,

3-APE.

Figure6.ScanningelectronmicrographoftensilefracturesurfaceofWRHA-?lledPP/NRcompositewith15%?llerloadingatmagni?cation400Â

.

Figure7.ScanningelectronmicrographoftensilefracturesurfaceofWRHA-?lledPP/NRcompositewith15%?llerloadingatmagni?cation700Â

.

canandbeadhesion®rmlyseenembeddedinFigs8andinthe9.FillerPP/NRparticlesmatrix,andwerecoatedbetterbecausebetteroccurredbridgingbetweenat®llertheinterfaceandpolymerisinmatrix;place,

PolymInt50:606±611(2001)

Whitericehuskash-polypropylene/naturalrubbercomposites

Figure8.Scanningelectronmicrographoftensilefracturesurfaceof

WRHA-?lledPP/NRcompositewith15%?llerloadingtreatedwith3-APEatmagni?cation400Â

.

Figure9.Scanningelectronmicrographoftensilefracturesurfaceof

WRHA-?lledPP/NRcompositewith15%?llerloadingtreatedwith3-APEatmagni?cation700Â

.

Figure10.ScanningelectronmicrographoftensilefracturesurfaceofWRHA-?lledPP/NRcompositewith45%?llerloadingatmagni?cation400Â.

bettercantransferofstressisweightbeseeninFigs10andexpected.11forcompositesAsimilarwithsituation45%surfaceof®ller.Figure10showsthetensilefracture400agglomerateÂ).ofItcancompositewithout3-APE(magni®cationpull-out,whichbeseenthatistheresponsiblesurfaceshowsforthe

®llerpoor

609

HIsmail,LMega,HPSAbdulKhalil

Figure11.ScanningelectronmicrographoftensilefracturesurfaceofWRHA-?lledPP/NRcompositewith45%?llerloadingtreatedwith3-APEatmagni?cation700Â

.

tensile3-APEstrength.However,thesimilarcompositewithembedded(Figbondingin11)theshowsPP/NRthatthecompositesWRHA®llerswerestressthoseofattheinterface.Thisexplainwhywiththegoodyieldofcompositescompositeswithwithout3-APE3-APE.

isofhighervaluethanabsorptionFigure12NRandshows®llertheloadingrelationshipofthebetweenwatersitescomposites.curveswithout®llerWaterwasabsorptionforWRHAPP/NR®lledcompo-PP/similar(exceptthatfortooPP/NRlow,iecomposite)lessthan0.5%.exhibitAllbeginningpattern,ieequilibriumandincreaseswaterabsorptionslowlyishigherattheationstagecanbeseen,andlatertheon.waterNoabsorp-clearwaterisexpectedloading.absorptiontoincreasesincreaseslowly.ItcanbeseenthatSiOThismightbeduetowithhigherincreasingcontentofWRHAsilica,contains2inWRHA,iebondswithÐOHwatergroupsabout95%.WRHAispolarandmolecules.whichWhencantheform®llerhydrogenloading

Figure12.Effectof?llerloadingonwaterabsorptionofWRHA-?lledPP/NRcomposites.

610Figure13.Waterabsorptionversus?llerloadingofWRHA-?lledPP/NRcompositeswithandwithoutasilanecouplingagent,

3-APE.

increases,morehydroxylhydrogenbondingoccursbetweenabsorptionFiguregroups13showsandthewatermolecules.

weightthatof®llerofWRHA-®lledcomparisonwithandPP/NRbetweencompositetheatwater15%APEatwithout3-APE.Itcanbeseenthehasasimilarreducedabsorptiontheamounttimesofwaterincorporationabsorptionofby3-WRHA-®lledcomposites.ThelowerwaterabsorptionofthemayabeattributedPP/NRtothecompositeabilityofthetreatedchemicalwithto3-APEformconsequentlyprotectiveeculesintothepreventslayeratWRHA.directtheinterfacialdiffusionofzone,whichwatermol-CONCLUSIONS

Theconclusionsmadefromthisstudyareasfollows:(1)ThematrixincorporationoftheWRHAmodulus.resultedinanimprovementinintheaPP/NR

tensilebreakHowever,tensilestrength,elongationat®llerandstressatyielddecreasedwithincreasingattributedloading.toThethereductionpoorWRHA±PP/NRofthesepropertiesmatrixis(2)interaction.

TheAPE)incorporationproducedofasilanecouplingagent(3-(3)modulus,tensilecompositesTheresistanceincorporationstrengthofthecomposites.

of3-APEandwithalsostressimprovedtensileimprovedatyield.

water

REFERENCES

1DeSKandBhowmickAK(Eds),ThermoplasticElastomersfrom

23CoranRubber±PlasticBhowmickAYandPatelBlendsR,,EllisRubberHorwood,NewChemTechnolYork56:1045(1990).NewDevelopmentsAKandStephensandTechnologyHL(Eds),(1983).,MHandbookofElastomers±

4Elliott(1988).

arcelDekker,NewYorkDJ,NRTechnology123:59

(1981).

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