双螺杆反应挤出制备碳纤维增强尼龙6复合材料的研究-英文-

9320092167121819(2009)320620204ScienceTechnologyandEngineeringVol19No13Feb.2009Z2009Sci1Tech1Engng163(,266071)6,32:1SLJ-35B,20:1;,6;TQ327;A200810153:,,,E2mail:[e-mail]listofengineeringplas2tics,andtheirusehasbecomepopularduetotheirat2tractiveproperties.Butnylonmatrixcanabsorbmois2ture,whichaffectsthelongtermstructuraldurabilityandpropertiesofthematerials[1,2].Sincehighper2formancecarbonfibers(CF)absorblittleornomois2turecomparedtothematrix.TheCFreinforcednylon(CFRPA)compositenotonlyimprovesphysicalprop2ertiesofthecomposite,butalsoadvancesretentionofphysicalpropertiesinhumidenvironments.SotheCFRPAcompoundsarewidelyusedinavarietyofap2plications,suchasaerospace,masstransit,automotiveandsportinggoods.NowthemethodsmanufacturingCFRPAcompositearemainlyprepreg,laminatedmouldingandinjectionmoulding[5,6].Eachmethodusedhasitsadvantagesintermsofphysicalcontrolandprocesscosts,theimpor2tanceofunderstandinghowtoincorporatethefibersin2toamatrixofpolymer,hasbeenunderestimatedforalongtime.Goodcontrolovervariousmixingparametersareessentialtoobtainhomogeneouscompositemateri2als[79],meanwhilecontinuousprocessandlarge2scaleproductionarealsoimportant.Inviewofabovethreepoints,CFRPAcompositemanufacturingwascar2riedoutinaSLJ-35Btwin2screwextruderinthisarti2cle.DispersionofCF,physicalpropertiesinhumidenvironmentsandthefiber2matrixbondwerealsostud2ied.1Experimental1.1MaterialsNylon6(PA6)pelletssuppliedbytheChinaPet2rochemicalBaLingCompanyLtd.TheCFwerecutto5mm.Surfacewastreatedby65wt%nitricacidsolu2tionin80waterbathfor2h.Afterwardsthefiberswerewashedwithdistilledwatertoeliminatetheexcessofreagents.Finallythefiberswerestarchedbytitanatecouplingagent.1.2PreparationofsamplesPA6pelletswerefirstdry2mixedwiththeshort2cutCF.Theblendswith5wt%CFcontentwerethenfedintotheextruderundertherequiredconditions.Theprocessingtemperatureinthefirstheatingzonewasheldat120,whiletheotherzoneswerecontrolledat(210230).Therotatingspeedofscrewswasmaintainedat80r/min.Finallythedrypelletswereinjectedintostandardsplines.1.3CharacterizationTensilestressandtensilemodulusweremeasuredaccordingtostandardISO11841983byusinganelectronictensiletester.NotchedimpactstrengthwasmeasuredaccordingtoISO1791982standardmeth2odusingstandardnotchedspecimens.InterfaceofcompositewasexaminedwithaSEM(JSM6390LV)ofJapaneseJeolCompanyrunningatanacceleratingvoltageof20kV.2Resultsanddiscussion2.1Length2diameterratioanddispersionofCFinCFRPA6WhencarbonfibersandPA6pelletsaremixedinthetwin2screwextruder,itisimportanttokeepthelength2diameterratioofCFasbiggeraspossibleunderthepremiseofgooddispersionofCFinCFRPA6.Thebiggerthelength2diameterratioofCF,thebetterthereinforcementofCFinCFRPA6.Throughselectingreasonablescrewpartsandextrusionprocessinthispa2per,transportation,plasticization,shearandmixingoftherawmaterialobtainedprominenteffect.Figure1showedthattheCFwiththelongestlengthof0.2mmweredispersedhomogeneouslyinthecomposite.MostCFdiameterswere56m;CFincompositewiththelength2diameterratioabove241accountedfor7%,andCFincompositewiththelength2diameterratiobe2tween121241accountedfor65%.Sothedistribu2tionoflength2diameterratiointhispaperaccordedwiththedistributionruleofgeneralreinforcingfiber.Ac2cordingtothemicroscopeobservation,itwasconfirmedthattheuniformlydispersedCFRPA6compositewaspreparedinatwin2screwextruder.Figure1CFRPA6surfacemorphology(100foldamplification)2.2RetentionofphysicalpropertiesofCFRPA6inhumidenvironmentsThissectionabatchofinjectedstandardsplinesweretestedafterdriedina80vacuumovenfor8h,andtheotherbatchofinjectedstandardsplinesweretestedaftermoistureabsorptioninroomtemperaturefor1week.Moistureabsorptionleadstochangesinthephysicalcharacteristicsofthematrixbyplasticizationandhydrolysisandresultsinthelossofmicrostructuralintegrity.Matrixdominatedpropertiessuchastensilestrength,tensilemodulusandimpactresistancearemoststronglyaffected.Butcomparedtotheneatny2lon6resin,theCFRPA6compositefeatureimprovedretentionofphysicalpropertiesinhumidenvironments.Tensilestrengthoftheneatnylonresindecreased20.4%aftermoistureabsorption,whilethe5wt%treatedcarbonfiberreinforcednylon6compositede2creasedonly0.5%(Table1);Waterabsorptionoftheneatnylonresinwas0.61%,andthatof5wt%treatedcarbonfiberreinforcednylon6compositewas0.40%;Dimensionchangingrateoftheneatnylonresinwas1.32%,andthatof5wt%treatedcarbonfiberreinforcednylon6compositewas0.66%.Analy2sissuggestedthatthefiber2matrixbondhasformed1263,:6stronginterface,whichimprovedmicrostructuralinteg2rityanddecreasedmicro2cracksofcompositethatwastheimportantpathformoisturepenetration.Table1ThechangesofphysicalpropertiesofCFRPA6inhumidenvironmentsPropertyBeforemoistureabsorptionAftermoistureabsorptionRC21RC22RC21RC22Tensilestrength(MPa)65.773.752.370.2Tensilemodulus(MPa)1757226315332168Notchedimpactstrength(KJ/m2)11.814.812.515.3Weight(g)19.04419.41319.15819.480Length(mm)120.26120.76121.78121.56RC21:theneatnylon6RC22:5wt%treatedcarbonfiberrein2forcednylon6composite2.3TensilefracturesurfacemorphologyofCFR2PAObservationoftheSEMwasusedtorevealth