外文翻译-玻璃纤维增强复合材料水辅注塑成型的实验研究

附录附录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.玻璃纤维增强复合材料水辅注塑成型的实验研究摘要：本报告的目的是通过实验研究聚对苯二甲酸丁二醇复合材料水辅注塑的成型工艺。实验在一个配备了水辅注塑统的80吨注塑机上进行，包括一个水泵，一个压力检测器，一个注水装置。实验材料包括PBT和15%玻璃纤维填充PBT的混合物以及一个中间有一个肋板的空心盘。实验根据水注入制品的长度的影响测得了各种工艺参数以及它们的机械性能。XRD也被用来分别材料和结构参数。最后,作了水辅助和气体辅助注塑件的比较。实验发现熔体压力,熔融温度，及短射类型是影响水注塑行为的决定性参数。材料在模具一面比在水一面展示了较高的结晶度。气辅成型制品也要比水辅成型制品结晶度高。另外，制品表面的玻璃纤维大部分取向与流动方向一致，而随着离制品表面距离的增加，越来越多的垂直与流动方向。关键词：水辅注塑成型，玻璃纤维增强PBT，工艺参数，机械性能，结晶，1．前言依靠重量轻，成型周期短，消耗低，水辅注塑成型技术在塑料制品制造方面已经取得了突破。在水辅注塑成型中，模具行腔被部分注入聚合物熔体，而后向这些聚合物中心注入水。水辅注塑成型的原理如图1图1水辅注塑成型的原理如图水辅注塑成型能够在更短的循环时间内生产出收缩小，翘曲小，表面质量好的各种薄厚的制品。水辅注塑成型工艺也可根据工具及设备的承受压力在设计，节省材料，减轻重量，减少成本方面取得更大的自由。典型的应用有棒，管材，水路管网建设用的大型复合结构管。另一方面，尽管有很多优势，由于加入了额外的工艺参数，模具和工艺控制变的更加严峻和困难。水也可能腐蚀模具钢，同时一些材料包括热塑性塑料难以成型。成型后水的清除也是对这个新技术的一个挑战。表1列出了水辅注塑成型技术的优势和局限性。表1优势局限性1，成型周期短2，成本低（水更便宜而且可方便地循环利用）3，制品内部不产生泡沫现象。1，水腐蚀模具2，需要较大的注塑元件。（容易陷入聚合物熔体）3，一些材料难以成型（尤其是非晶态热塑性材料）4，成型后需要清除水表12．实验步骤2.1材料实验材料包括PBT（牌号1111FB，南亚塑料，台湾）和15%玻璃纤维填充PBT的混合物（牌号1210G3，南亚塑料，台湾）。表3列出了此混合材料的特征。表3纤维增强PBT复合材料特征性质ASTMPBT15%G.F.PBT屈服应力(kg/cm2)弯曲应力(kg/cm2)硬度热变形温度（℃）MFI冲击强度熔点（℃）D-638D-570D-785D-648D-1238D-256DSC60090011960405224100015001202002552242.2水辅注塑元件一个实验室注水元件，包括一个水泵，一个压力检测器，一个注水阀，一个配备了温度调节装置的水箱，以及一个控制电路。这个孔板型注水阀每边有两个孔，用来成型制件。实验过程中，注水阀的控制电路收到由注塑机产生的信号实现对时间和注水压力的控制。在注入模具行腔之前，水在有温控装置的水箱里加热30分钟。2.3注塑机和模具水辅注塑成型实验在一个最高注塑速率109cm3/s的为了对水辅和气辅注塑成型制件进行比较，气辅注塑成型实验使用了一个商用气辅注塑成型元件，其具体配置可参考RCFS。气辅注塑成型工艺控制和水辅注塑成型一样，除了气