外文翻譯-玻璃纖維增強(qiáng)復(fù)合材料水輔注塑成型的實(shí)驗(yàn)研究

附錄附錄1Anexperimentalstudyofthewater-assistedinjectionmoldingofglassfiberfilledpoly-butylene-terephthalate(PBT)compositesAbstract：Thepurposeofthisreportwastoexperimentallystudythewater-assistedinjectionmoldingprocessofpoly-butylene-terephthalate(PBT)composites.Experimentswerecarriedoutonan80-toninjection-moldingmachineequippedwithalabscalewaterinjectionsystem,whichincludedawaterpump,apressureaccumulator,awaterinjectionpin,awatertankequippedwithatemperatureregulator,andacontrolcircuit.ThematerialsincludedvirginPBTanda15%glassfiberfilledPBTcomposite,andaplatecavitywitharibacrosscenterwasused.Variousprocessingvariableswereexaminedintermsoftheirinfluenceonthelengthofwaterpenetrationinmoldedparts,andmechanicalpropertytestswereperformedontheseparts.X-raydiffraction(XRD)wasalsousedtoidentifythematerialandstructuralparameters.Finally,acomparisonwasmadebetweenwater-assistedandgas-assistedinjectionmoldedparts.Itwasfoundthatthemeltfillpressure,melttemperature,andshortshotsizewerethedominantparametersaffectingwaterpenetrationbehavior.Materialatthemold-sideexhibitedahigherdegreeofcrystallinitythanthatatthewater-side.Partsmoldedbygasalsoshowedahigherdegreeofcrystallinitythanthosemoldedbywater.Furthermore,theglassfibersnearthesurfaceofmoldedpartswerefoundtobeorientedmostlyintheflowdirection,butorientedsubstantiallymoreperpendiculartotheflowdirectionwithincreasingdistancefromtheskinsurface.Keywords:Waterassistedinjectionmolding;Glassfiberreinforcedpoly-butylene-terephthalate(PBT)composites;Processingparameters;B.Mechanicalproperties;Crystallinity;A.Polymermatrixcomposites;1.IntroductionWater-assistedinjectionmoldingtechnology[1]hasproveditselfabreakthroughinthemanufactureofplasticpartsduetoitslightweight,fastercycletime,andrelativelylowerresincostperpart.Inthewater-assistedinjectionmoldingprocess,themoldcavityispartiallyfilledwiththepolymermeltfollowedbytheinjectionofwaterintothecoreofthepolymermelt.Aschematicdiagramofthewater-assistedinjectionmoldingprocessisillustratedinFig.1.Water-assistedinjectionmoldingcanproducepartsincorporatingboththickandthinsectionswithlessshrink-ageandwarpageandwithabettersurfacefinish,butwithashortercycletime.Thewater-assistedinjectionmoldingprocesscanalsoenablegreaterfreedomofdesign,materialsavings,weightreduction,andcostsavingsintermsoftoolingandpresscapacityrequirements[2–4].Typicalapplicationsincluderodsandtubes,andlargesheet-likestructuralpartswithabuilt-inwaterchannelnetwork.Ontheotherhand,despitetheadvantagesassociatedwiththeprocess,themoldingwindowandprocesscontrolaremorecriticalanddifficultsinceadditionalprocessingparametersareinvolved.Watermayalsocorrodethesteelmold,andsomematerialsincludingthermoplasticcompositesaredifficulttomoldsuccessfully.Theremovalofwateraftermoldingisalsoachallengeforthisnoveltechnology.Table1liststheadvantagesandlimitationsofwater-assistedinjectionmoldingtechnology.Fig.1.Schematicdiagramofwater-assistedinjectionmoldingprocess.Waterassistedinjectionmoldinghasadvantagesoveritsbetterknowncompetitorprocess,gasassistedinjectionmolding[5],becauseitincorporatesashortercycletimetosuccessfullymoldapartduetothehighercoolingcapacityofwaterduringthemoldingprocess.Theincompressibility,lowcost,andeaseofrecyclingthewatermakesitanidealmediumfortheprocess.Sincewaterdoesnotdissolveanddiffuseintothepolymermeltsduringthemoldingprocess,theinternalfoamingphenomenon[6]thatusuallyoccursingas-assistedinjectionmoldedpartscanbeeliminated.Inaddition,waterassistedinjectionmoldingprovidesabettercapabilityofmoldinglargerpartswithasmallresidualwallthickness.Table2listsacomparisonofwaterandgasassistedinjectionmolding.Withincreasingdemandsformaterialswithimprovedperformance,whichmaybecharacterizedbythecriteriaoflowerweight,higherstrength,andafasterandcheaperproductioncycletime,theengineeringofplasticsisaprocessthatcannotbeignored.Theseplasticsincludethermoplasticandthermosetpolymers.Ingeneral,thermoplasticpolymershaveanadvantageoverthermosetpolymersinpopularmaterialsinstructuralapplications.Poly-butylene-terephthalate(PBT)isoneofthemostfrequentlyusedengineeringthermoplasticmaterials,whichisformedbypolymerizing1.4butyleneglycolandDMTtogether.Fiber-reinforcedcompositematerialshavebeenadaptedtoimprovethemechanicalpropertiesofneatplasticmaterials.Today,shortglassfiberreinforcedPBTiswidelyusedinelectronic,communicationandautomobileapplications.Therefore,theinvestigationoftheprocessingoffiber-reinforcedPBTisbecomingincreasinglyimportant[7–10].Thisreportwasmadetoexperimentallystudythewaterassistedinjectionmoldingprocessofpoly-butylene-terephthalate(PBT)materials.Experimentswerecarriedoutonan80-toninjection-moldingmachineequippedwithalabscalewaterinjectionsystem,whichincludedawaterpump,apressureaccumulator,awaterinjectionpin,awatertankequippedwithatemperatureregulator,andacontrolcircuit.ThematerialsincludedavirginPBTanda15%glassfiberfilledPBTcomposite,andaplatecavitywitharibacrosscenterwasused.Variousprocessingvariableswereexaminedintermsoftheirinfluenceonthelengthofwaterpenetrationinmoldedparts,whichincludedmelttemperature,moldtemperature,meltfillingspeed,short-shotsize,waterpressure,watertemperature,waterholdandwaterinjectiondelaytime.Mechanicalpropertytestswerealsoperformedonthesemoldedparts,andXRDwasusedtoidentifythematerialandstructuralparameters.Finally,acomparisonwasmadebetweenwater-assistedandgas-assistedinjectionmoldedparts.Table1Advantagesanddisadvantagesofwater-assistedinjectionmoldingAdvantagesDisadvantages1.Shortcycletime1.Corrosionofthesteelmoldduetowater2.Lowassistingmediumcost(waterismuchcheaperandcanbeeasilyrecycled)2.Largerorificesfortheinjectionpinrequired(easiertogetstuckbythepolymermelt)3.Nointernalfoamingphenomenoninmoldedparts3.Somematerialsaremoredifficulttomold(especiallyamorphousthermoplastics)4.Removalofwateraftermoldingisrequired2.Experimentalprocedure2.1.MaterialsThematerialsusedincludedavirginPBT(Grade1111FB,Nan-YaPlastic,Taiwan)anda15%glassfiberfilledPBTcomposite(Grade1210G3,Nan-YaPlastic,Taiwan).Table3liststhecharacteristicsofthecomposite2.2.WaterinjectionunitAlabscalewaterinjectionunit,whichincludedawaterpump,apressureaccumulator,awaterinjectionpin,awatertankequippedwithatemperatureregulator,andacontrolcircuit,wasusedforallexperiments[3].Anorifice-typewaterinjectionpinwithtwoorifices(0.3mmindiameter)onthesideswasusedtomoldtheparts.Duringtheexperiments,thecontrolcircuitofthewaterinjectionunitreceivedasignalfromthemoldingmachineandcontrolledthetimeandpressureoftheinjectedwater.Beforeinjectionintothemoldcavity,thewaterwasstoredinatankwithatemperatureregulatorfor30mintosustainanisothermalwatertemperature.2.3.MoldingmachineandmoldsWater-assistedinjectionmoldingexperimentswereconductedonan80-tonconventionalinjection-moldingmachinewithahighestinjectionrateof109cm3/s.Aplatecavitywithatrapezoidalwaterchannelacrossthecenterwasusedinthisstudy.Fig.2showsthedimensionsofthecavity.Thetemperatureofthemoldwasregulatedbyawater-circulatingmoldtemperaturecontrolunit.Variousprocessingvariableswereexaminedintermsoftheirinfluenceonthelengthofwaterpenetrationinwaterchannelsofmoldedparts:melttemperature,moldtemperature,meltfillpressure,watertemperatureandpressure,waterinjectiondelaytimeandholdtime,andshortshotsizeofthepolymermelt.Table4liststheseprocessingvariablesaswellasthevaluesusedintheexperiments.2.4.GasinjectionunitInordertomakeacomparisonofwaterandgas-assistedinjectionmoldedparts,acommerciallyavailablegasinjectionunit(GasInjectionPPC-1000)wasusedforthegasassistedinjectionmoldingexperiments.DetailsofthegasinjectionunitsetupcanbefoundintheRefs.[11–15].Theprocessingconditionsusedforgas-assistedinjectionmoldingwerethesameasthatofwater-assistedinjectionmolding(termsinboldinTable4),withtheexceptionofgastemperaturewhichwassetat25C.2.5.XRDInordertoanalyzethecrystalstructurewithinthewater-assistedinjection-moldedparts,wide-angleX-raydiffraction(XRD)with2DdetectoranalysesintransmissionmodewereperformedwithCuKaradiationat40kVand40mA.Morespecifically,themeasurementswereperformedonthemold-sideandwater-sidelayersofthewater-assistedinjection-moldedparts,withthe2hanglerangingfrom7to40.Thesamplesrequiredfortheseanalysesweretakenfromthecenterportionofthesemoldedparts.ToobtainthedesiredthicknessfortheXRDsamples,theexcesswasremovedbypolishingtheTable3Characteristicsoftheglass–fiberreinforcedPBTcompositePropertyASTMPBT15%G.F.PBTYieldstrength(kg/cm2)D-6386001000Bendingstress(kg/cm2)D-5709001500Hardness(R-scale)D-785119120Heatdistortiontemperature(C)(18.6kg/cm2)D-64860200Meltflowindex(MFI)D-123840251238Impactstrength(Kg-cm/cm)D-25655Meltingtemperature(C)DSC224224samplesonarotatingwheelonarotatingwheel,firstwithwetsiliconcarbidepapers,thenwith300-gradesiliconcarbidepaper,followedby600-and1200-gradepaperforabettersurfacesmoothness.2.6.MechanicalpropertiesTensilestrengthandbendingstrengthweremeasuredonatensiletester.Tensiletestswereperformedonspecimensobtainedfromthewater-assistedinjectionmoldedparts(seeFig.3)toevaluatetheeffectofwatertemperatureonthetensileproperties.Thedimensionsofspecimensfortheexperimentswere30mm·10mm·1mm.TensiletestswereperformedinaLLOYDtensiometeraccordingtotheASTMD638Mtest.A2.5kNloadcellwasusedandthecrossheadspeedwas50mm/min.Bendingtestswerealsoperformedatroomtemperatureonwater-assistedinjectionmoldedparts.Thebendingspecimenswereobtainedwithadiecutterfromparts(Fig.3)subjectedtovariouswatertemperatures.Thedimensionsofthespecimenswere20mm·10mm·1mm.BendingtestswereperformedinamicrotensiletesteraccordingtotheASTMD256test.A200Nloadcellwasusedandthecrossheadspeedwas50mm/min.2.7.MicroscopicobservationThefiberorientationinmoldedspecimenswasobservedunderascanningelectronmicroscope(JeolModel5410).Specimensforobservationwerecutfrompartsmoldedbywater-assistedinjectionmoldingacrossthethickness(Fig.3).Theywereobservedonthecross-sectionperpendiculartotheflowdirection.Allspecimensurfacesweregoldsputteredbeforeobservation.3.ResultsanddiscussionAllexperimentswereconductedonan80-tonconventionalinjection-moldingmachine,withahighestinjectionrateof109cm3/s.AplatecavitywithatrapezoidalwaterchannelacrossthecenterwasusedforallexperimentsTable4TheprocessingvariablesaswellasthevaluesusedintheexperimentsABCDEFMeltpressure(Mpa)Melttemperature(C)Shortshotsize(%)Waterpressure(Mpa)Watertemperature(C)Moldtemperature(C)140280（270）7688080126275（265）7797575114270(260)7810707098265(255)8011656584260(250)81126060Fig.3.Schematically,thepositioningofthesamplescutfromthemoldedpartsfortensileandbendingtestsandmicroscopicobservations.3.1.FingeringsinmoldedpartsAllmoldedpartsexhibitedthewaterfingeringphenomenonatthechanneltoplatetransitionareas.Inaddition,moldedglassfiberfilledcompositesshowedmoreseverewaterfingeringsthanthoseofnon-filledmaterials,asshownphotographicallyinFig.4.Fingeringsusuallyformwhenalessdense,lessviscousfluidpenetratesadenser,moreviscousfluidimmisciblewithit.Considerasharptwophaseinterfaceorzonewheredensityandviscositychangerapidly.Thepressureforce(P2P1)onthedisplacedfluidasaresultofavirtualdisplacementdxoftheinterfacecanbedescribedby[16],whereUisthecharacteristicvelocityandKisthepermeability.Ifthenetpressureforceispositive,thenanysmalldisplacementwillbeamplifiedandleadtoaninstabilityandpartfingerings.Forthedisplacementofadense,viscousfluid(thepolymermelt)byalighter,lessviscousone(water),wecanhaveDl=l1l2>0,andU>0[16].Inthiscase,instabilityandtherelevantfingeringresultwhenamoreviscousfluidisdisplacedbyalessviscousone,sincethelessviscousfluidhasthegreatermobility.Theresultsinthisstudysuggestthatglassfiberfilledcompositesexhibitahighertendencyforpartfingerings.ThismightbeduetothefactthattheviscositydifferenceDlbetweenwaterandthefilledcompositesislargerthanthedifferencebetweenwaterandthenon-filledmaterials.Waterassistedinjectionmoldedcompositesthusexhibitmoreseverepartfingerings.Fig.4.Photographofwater-assistedinjectionmoldedPBTcompositepart.3.2.EffectsofprocessingparametersonwaterpenetrationVariousprocessingvariableswerestudiedintermsoftheirinfluenceonthewaterpenetrationbehavior.Table4liststheseprocessingvariablesaswellasthevaluesusedintheexperiments.Tomoldtheparts,onecentralprocessingconditionwaschosenasareference(boldterminTableBychangingoneoftheparametersineachtest,wewereabletobetterunderstandtheeffectofeachparameteronthewaterpenetrationbehaviorofwaterassistedinjectionmoldedcomposites.Aftermolding,thelengthofwaterpenetrationwasmeasured.Figs.5–10showtheeffectsoftheseprocessingparametersonthelengthofwaterpenetrationinmoldedparts,includingmeltfillpressure,melttemperature,moldtemperature,shortshotsize,watertemperature,andwaterpressure.TheexperimentalresultsinthisstudysuggestthatwaterpenetratesfurtherinvirginPBTthaninglassfiberfilledPBTcomposites.Thisisduetothefactthatwiththereinforcingglassfibersthecompositematerialshavelessvolumetricshrinkageduringthecoolingprocess.Therefore,theymoldpartswithashorterwaterpenetrationlength.Thelengthofwaterpenetrationdecreaseswiththemeltfillpressure(Fig.5).Thiscanbeexplainedbythefactthatincreasingthemeltfillpressureincreasestheflowresistanceinsidethemoldcavity.Itisthenmoredifficultforthewatertopenetrateintothecoreofthematerials.Thelengthofwaterpenetrationdecreasesaccordingly[3].ThemelttemperaturewasalsofoundtoreducethewaterpenetrationinmoldedPBTcompositeparts(Fig.6).Thismightbeduetothefactthatincreasingthemelttemperaturedecreasesviscosityofthepolymermelt.Alowerviscosityofthematerialshelpsthewatertopackthewaterchannelandincreaseitsvoidarea,insteadofpenetratingfurtherintotheparts[4].Thehollowcoreratioatthebeginningofthewaterchannelincreasesandthelengthofwaterpenetrationmaythusdecrease.Increasingthemoldtemperaturedecreasessomewhatthelengthofwaterpenetrationinmoldedparts(Fig.7).Thisisduetothefactthatincreasingthemoldtemperaturedecreasesthecoolingrateaswellastheviscosityofthematerials.Thewaterthenpacksthechannelandincreasesitsvoidareanearthebeginningofthewaterchannel,insteadofpenetratingfurtherintotheparts[3].Moldedpartsthushaveashorterwaterpenetrationlength.Increasingtheshortshotsizedecreasesthelengthofwaterpenetration(Fig.8).Inwater-assistedinjectionmolding,themoldcavityispartiallyfilledwiththepolymermeltfollowedbytheinjectionofwaterintothecoreofthepolymermelt[4].Increasingtheshortshotsizeofthepolymermeltwillthereforedecreasethelengthofwaterpenetrationinmoldedparts.Fortheprocessingparametersusedintheexperiments,increasingthewatertemperature(Fig.9)orthewaterpressure(Fig.10)increasesthelengthofwaterpenetrationinmoldedparts.Increasingthewatertemperaturedecreasesthecoolingrateofthematerialsandkeepsthepolymermelthotforalongertime;theviscosityofthematerialsdecreasesaccordingly.Thiswillhelpthewaterpenetratefurtherintothecoreoftheparts[3].Increasingthewaterpressurealsohelpsthewaterpenetrateintothematerials.Thelengthofwaterpenetrationthusincreases.Finally,thedeflectionofmoldedparts,subjectedtovariousprocessingparameters,wasalsomeasuredbyaprofilemeter.Themaximummeasureddeflectionisconsideredasthepartwarpage.TheresultinFig.11suggeststhatthepartwarpagedecreaseswiththelengthofwaterpenetration.Thisisduetothefactthatthelongerthewaterpenetration,themorethewaterpressurecanpackthepolymericmaterialsagainstthemoldwall.Theshrinkageaswellastherelevantpartwarpagedecreasesaccordingly.Fig.5.Effectsofmeltfillpressureonthelengthofwaterpenetrationinmoldedparts.Fig.6.Effectsofmelttemperatureonthelengthofwaterpenetrationinmoldedparts.Fig.9.Effectsofwatertemperatureonthelengthofwaterpenetrationinmoldedparts.Fig.7.Effectsofmoldtemperatureonthelengthofwaterpenetrationinmoldedparts.Fig.8.Effectsofshortshotsizeonthelengthofwaterpenetrationinmoldedparts.Fig.10.Effectsofwaterpressureonthelengthofwaterpenetrationinmoldedparts.3.3.CrystallinityofmoldedpartsPBTisasemi-crystallinethermoplasticpolyesterwithahighcrystallizationrate.Inthewater-assistedinjectionmoldingprocess,crystallizationoccursundernon-isothermalconditionsinwhichthecoolingratevarieswithcoolingtime.Heretheeffectsofvariousprocessingparameters(includingmelttemperature,moldtemperature,andwatertemperature)onthelevelofcrystallinityinmoldedpartswerestudied.MeasurementswereconductedonawideangleX-raydiffraction(XRD)with2Ddetectoranalyses(asdescribedinSection2).ThemeasuredresultsinFig.12showedthatallmaterialsatthemold-sidelayerexhibitedahigherdegreeofcrystallinitythanthoseatthewater-sidelayer.Theresultindicatesthatthewaterhasabettercoolingcapacitythanthemoldduringthecoolingprocess.Thismatchesourearlierfinding[17]bymeasuringthein-moldtemperaturedistribution.Inaddition,theexperimentalresultinFig.12calsosuggeststhatthecrystallinityofthemoldedmaterialsgenerallyincreaseswiththewatertemperature.Thisisduetothefactthatincreasingthewatertemperaturedecreasesthecoolingrateofthematerialsduringthecoolingprocess.Moldedpartsthusexhibitedahigherlevelofcrystallinity.Ontheotherhand,tomakeacomparisonofthecrysallinityofpartsmoldedbygasandwater,gas-assistedinjectionmoldingexperimentswerecarriedoutonthesameinjectionmoldingmachineasthatusedwithwater,butequippedwithahigh-pressurenitrogengasinjectionunit[11–15].ThemeasuredresultsinFig.13suggeststhatgas-assistedinjectionmoldedpartshaveahigherdegreeofcrystallinitythanwater-assistedinjectionmoldparts.Thisisduetothefactthatwaterhasahighercoolingcapacityandcoolsdownthepartsfasterthangas.Partsmoldedbywaterthusexhibitedalowerlevelofcrystallinitythanthosemoldedbygas.Fig.11.Measuredwarpageofmoldedpartsdecreaseswiththelengthofwaterpenetration.3.4.MechanicalpropertiesTensiletestswereperformedonspecimensobtainedfromthewater-assistedinjectionmoldedpartstoexaminetheeffectofwatertemperatureonthetensileproperties.Fig.14showedthemeasureddecreasesubjectedtovariouswatertemperatures.Ascanbeobserved,bothyieldstrengthandtheelongationalstrainatbreakofwaterassistedmoldedPBTmaterialsdecreasewiththewatertemperature.Ontheotherhand,bendingtestswerealsoperformedatroomtemperatureonwater-assistedinjectionmoldedparts.ThemeasuredresultinFig.15suggeststhatthebendingstrengthofmoldedpartsdecreaseswiththewatertemperature.Increasingthewatertemperaturegenerallydecreasesthecoolingrateandmoldspartswithhigherlevelofcrystallin-contentoffreevolumeandthereforeanincreasinglevelofstiffness.However,theexperimentalresultsheresuggestthatthequantitativecontributionofcrystallinitytoPBT’smechanicalpropertiesisnegligible,whilethereisamoreimportantquantitativeincreaseoftensileandbendingstrengthforthePBTmaterials.Themechanicalpropertiesofmoldedmaterialsaredependentonboththeamountandthetypeofcrystallineregionsdevelopedduringprocessing.ThefactthattheductilityofPBTdecreaseswiththedegreeofcrystallinitymayindicatethatamorecrystallineandstifferPBTdevelopedatalowercoolingrateduringprocessinganddidnotexhibithigherstressvaluesintensiletestsbecauseofalackofductility,andthereforedidnotbehaveasstrongasexpectedfromtheirstiffness[18].Nevertheless,moredetailedexperimentswillbeneededforthefutureworkstoinvestigatethemorphologicalparametersofwater-assistedinjectionmoldedpartsandtheircorrelationwiththeparts’mechanicalproperties.3.5.FiberorientationinmoldedpartsSmallspecimenswerecutoutfromthemiddleofmoldedpartsinordertoobservetheirfiberorientation.ThepositionofthespecimenforthefiberorientationobservationisasshowninFig.3.Allspecimensurfaceswerepolishedandgoldsputteredbeforeobservation.Fig.16showsthemicrostructureofthewater-assistedinjectionmoldedcompositeparts.Themeasuredresultsuggeststhatthefiberorientationdistributioninwater-assistedinjectionmoldedpartsisquitedifferentfromthatofconventionalinjectionity.Asisusuallyencounteredinsemi-crystallinethermoplastics,ahigherdegreeofcrystallizationmeansalowermoldedparts.Inconventionalinjectionmoldedparts,tworegionsareusuallyobserved:thethinskinandthecore.Intheskinregionnearthewall,allfibersareorientedparalleltotheinjectionmolding,water-assistedinjectionmoldingtechnologyisdifferentinthewaythemoldisfilled.Withaconventionalinjectionmoldingmachine,onecycleischaracterizedbythephasesoffilling,packingandcooling.Inthewater-assistedinjectionmoldingprocess,themoldcavityispartiallyfilledwiththepolymermeltfollowedbytheinjectionofwaterintothecoreofthepolymermelt.Thenovelfillingprocessinfluencestheorientationoffibersandmatrixinapartsignificantly.FromFig.16,thefiberorientationinwater-assistedinjectionmoldedpartscanbeapproximatelydividedintothreezones.Inthezonenearthemold-sidesurfacewheretheshearismoresevereduringthemoldfilling,fibersareprincipallyparallel.Forthezonenearthewater-sidesurface,theshearissmallerandthevelocityvectorgreater.Inthiscase,thefibertendstobepositionedmoretransverselyinthedirectionofinjection.Atthecore,thefiberstendtobeorientedmorerandomly.Generallyspeaking,theglassfibersnearthemold-sidesurfaceofmoldedpartswerefoundtobeorientedmostlyintheflowdirection,andorientedsubstantiallyperpendiculartotheflowdirectionwithincreasingdistancefromthemold-sidesurface.Finally,itshouldbenotedthataquantitativecomparisonofmorphologyandfiberorientation[21]inwaterassistedmoldedandconventionalinjectionmoldedpartswillbemadebyourlabinfutureworks.Fig.16.Fiberorientationacrossthethicknessofwater-assistedinjectionmoldedPBTcomposites.4.ConclusionsThisreportwasmadetoexperimentallystudythewater-assistedinjectionmoldingprocessofpoly-butylene-terephthalate(PBT)composites.Thefollowingconclusionscanbedrawnbasedonthecurrentstudy.1.Water-assistedinjectionmoldedPBTpartsexhibitthefingeringphenomenonatthechanneltoplatetransitionareas.Inaddition,glassfiberfilledcompositesexhibitmoreseverewaterfingeringsthanthoseofnon-filledmaterials.2.TheexperimentalresultsinthisstudysuggestthatthelengthofwaterpenetrationinPBTcompositematerialsincreaseswithwaterpressureandtemperature,anddecreaseswithmeltfillpressure,melttemperature,andshortshotsize.3.Partwarpageofmoldedmaterialsdecreaseswiththelengthofwaterpenetration.4.Thelevelofcrystallinityofmoldedpartsincreaseswiththewatertemperature.Partsmoldedbywatershowalowerlevelofcrystallinitythanthosemoldedbygas.5.TheglassfibersnearthesurfaceofmoldedPBTcompositepartswerefoundtobeorientedmostlyintheflowdirection,andorientedsubstantiallyperpendiculartotheflowdirectionwithincreasingdistancefromtheskinsurface.玻璃纖維增強(qiáng)復(fù)合材料水輔注塑成型的實(shí)驗(yàn)研究摘要：本報(bào)告的目的是通過實(shí)驗(yàn)研究聚對苯二甲酸丁二醇復(fù)合材料水輔注塑的成型工藝。實(shí)驗(yàn)在一個配備了水輔注塑統(tǒng)的80噸注塑機(jī)上進(jìn)行，包括一個水泵，一個壓力檢測器，一個注水裝置。實(shí)驗(yàn)材料包括PBT和15%玻璃纖維填充PBT的混合物以及一個中間有一個肋板的空心盤。實(shí)驗(yàn)根據(jù)水注入制品的長度的影響測得了各種工藝參數(shù)以及它們的機(jī)械性能。XRD也被用來分別材料和結(jié)構(gòu)參數(shù)。最后,作了水輔助和氣體輔助注塑件的比較。實(shí)驗(yàn)發(fā)現(xiàn)熔體壓力,熔融溫度，及短射類型是影響水注塑行為的決定性參數(shù)。材料在模具一面比在水一面展示了較高的結(jié)晶度。氣輔成型制品也要比水輔成型制品結(jié)晶度高。另外，制品表面的玻璃纖維大部分取向與流動方向一致，而隨著離制品表面距離的增加，越來越多的垂直與流動方向。關(guān)鍵詞：水輔注塑成型，玻璃纖維增強(qiáng)PBT，工藝參數(shù)，機(jī)械性能，結(jié)晶，1．前言依靠重量輕，成型周期短，消耗低，水輔注塑成型技術(shù)在塑料制品制造方面已經(jīng)取得了突破。在水輔注塑成型中，模具行腔被部分注入聚合物熔體，而后向這些聚合物中心注入水。水輔注塑成型的原理如圖1圖1水輔注塑成型的原理如圖水輔注塑成型能夠在更短的循環(huán)時(shí)間內(nèi)生產(chǎn)出收縮小，翹曲小，表面質(zhì)量好的各種薄厚的制品。水輔注塑成型工藝也可根據(jù)工具及設(shè)備的承受壓力在設(shè)計(jì)，節(jié)省材料，減輕重量，減少成本方面取得更大的自由。典型的應(yīng)用有棒，管材，水路管網(wǎng)建設(shè)用的大型復(fù)合結(jié)構(gòu)管。另一方面，盡管有很多優(yōu)勢，由于加入了額外的工藝參數(shù)，模具和工藝控制變的更加嚴(yán)峻和困難。水也可能腐蝕模具鋼，同時(shí)一些材料包括熱塑性塑料難以成型。成型后水的清除也是對這個新技術(shù)的一個挑戰(zhàn)。表1列出了水輔注塑成型技術(shù)的優(yōu)勢和局限性。表1優(yōu)勢局限性1，成型周期短2，成本低（水更便宜而且可方便地循環(huán)利用）3，制品內(nèi)部不產(chǎn)生泡沫現(xiàn)象。1，水腐蝕模具2，需要較大的注塑元件。（容易陷入聚合物熔體）3，一些材料難以成型（尤其是非晶態(tài)熱塑性材料）4，成型后需要清除水表12．實(shí)驗(yàn)步驟2.1材料實(shí)驗(yàn)材料包括PBT（牌號1111FB，南亞塑料，臺灣）和15%玻璃纖維填充PBT的混合物（牌號1210G3，南亞塑料，臺灣）。表3列出了此混合材料的特征。表3纖維增強(qiáng)PBT復(fù)合材料特征性質(zhì)ASTMPBT15%G.F.PBT屈服應(yīng)力(kg/cm2)彎曲應(yīng)力(kg/cm2)硬度熱變形溫度（℃）MFI沖擊強(qiáng)度熔點(diǎn)（℃）D-638D-570D-785D-648D-1238D-256DSC60090011960405224100015001202002552242.2水輔注塑元件一個實(shí)驗(yàn)室注水元件，包括一個水泵，一個壓力檢測器，一個注水閥，一個配備了溫度調(diào)節(jié)裝置的水箱，以及一個控制電路。這個孔板型注水閥每邊有兩個孔，用來成型制件。實(shí)驗(yàn)過程中，注水閥的控制電路收到由注塑機(jī)產(chǎn)生的信號實(shí)現(xiàn)對時(shí)間和注水壓力的控制。在注入模具行腔之前，水在有溫控裝置的水箱里加熱30分鐘。2.3注塑機(jī)和模具水輔注塑成型實(shí)驗(yàn)在一個最高注塑速率109cm3/s的為了對水輔和氣輔注塑成型制件進(jìn)行比較，氣輔注塑成型實(shí)驗(yàn)使用了一個商用氣輔注塑成型元件，其具體配置可參考RCFS。氣輔注塑成型工藝控制和水輔注塑成型一樣，除了氣