英文文献参考模板.docx
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英文文献参考模板.docx
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英文文献参考模板
EffectsandOptimizationofProcessingParameters
inWater-AssistedInjectionMolding
1ABSTRACT:
Experimentsofwater-assistedinjectionmoldedpolypropylenecurvedpipewerecarriedoutonnewlydevelopedequipmentinthislab.First,fourprocessingparameters,includingshort-shotsize,melttemperature,waterinjectiondelaytime,andwaterpressure,wereinvestigatedintermsoftheireffectsonthewaterpenetrationlengthandresidualwallthicknessofcurvedpipe.Second,anorthogonalarrayofTaguchi,theS/Nratio,andANOVAwereutilizedtofindtheoptimalprocessingparametersresultinginmaximumwaterpenetrationlength.Finally,thecrystallizationbehaviordifferencebetweenthebeginningandtheendofthewaterchannelofthecurvedpipewasanalyzedusingdifferentialscanningcalorimetry.Itwasinterestingtofindthatthecrystallinityofsamplefromthemiddleishigherthanthosefrombothouterandinnerlayersatpositionnearthewaterinlet.Thesamplestakenfromtheouterlayer,middle,andinnerlayershowsimilarmeltingpeakandcrystallinityatpositionneartheendofwaterchannel.
Keywords:
crystallization;differentialscanningcalorimetry(DSC);injectionmolding;poly(propylene)(PP)
2INTRODUCTION
Overaperiodofrecentyears,fluid-assistedinjectionmoldingtechnologies,includinggas-assisted1–6andwater-assisted7–18injectionmolding,haveattractedmoreandmoreattentioninresearchesandapplications,duetothattheyofferpotentialtotheproductionofcomplex,highlyintegratedpartsinvirtuallyoneprocessstep.Water-andgas-assistedinjectionmolding(WAIMandGAIM)aresimilarprocessesandtheybothutilizehigh-pressurefluidswithviscositiesmuchlowerthanthepolymermeltviscositytodisplacethepolymermeltwithinthicksectionsofthecavity.Justbeforedemolding,thefluidisreleasedfromthecoretoprovideahollowbutfullyformedgeometry.TheGAIMisawell-knowntechnologyforproducinghollowpartslikemediaducts,handlesorclutchpedals.TheadvantagesoftheWAIMhavemadethistechnologyaninterestingalternativetotheGAIMoverthelastfewyears.
InWAIM,waterisusedastheactuatingmedium.Themainbenefitofusingwaterinsteadofgasisthemuchbettercoolingabilityofwater.Theconsiderablymoreefficientcoolingeffectandhighheatcapacityofwaterresultinaveryefficientdoublesidedcoolingoftheparts.Sincethewaterisindirectcontactwiththemoltenpolymer,coolingfromtheinsideisevenbetterthancoolingfromtheoutsidebymetal.Areductionincycletimesofabout50–70%wasachievedwithWAIM,whensimilarplasticsandpartgeometrieswerecompared.Thispotentialcycletimereductionshowstheproductivityimprovementpossibilities.Moreover,WAIMhasbeenreportedtoformathinnerresidualwallthicknessthanstandardGAIMandtoformchannelsaroundchangesindirectionthataremoreconcentricthanstandardGAIM;thegreaterinertiaofthewateristhoughttocontributetothiseffect.18Theincompressibility,lowcost,andeaseofrecyclingthewatermakesitanidealmediumfortheprocess.SoWAIMopensnewpossibilitiesfornewandexcitingapplications.Forexample,automotivemanufacturershavethepotentialforabroadrangeofcostsavingswiththeproductionoffluidmediapipingandcardoorhandles
DespitetheadvantagesassociatedwiththeWAIMprocess,themoldingwindowandprocesscontrolaremorecriticalanddifficultsinceadditionalprocessingparametersareinvolved.Thesenewwaterrelatedprocessingparametersincludetheamountofmeltinjection,waterpressure,watertemperature,andwaterinjectiondelaytime.13Sincethistechniqueisrelativelynewandstillinitsinfancy,in-depthresearchontheproductdesign,machinedesign,molddesign,thecontrolofprocessparameters,andthequalityoftheproducthasnotyetbeenconducted.CertainprocessingparametersinWAIMplayanimportantroleinachievingahighqualityhollowpart.Moreover,tothebestknowledgeoftheauthors,noresearchpaperhaseverreportedthecrystallizationbehaviorofwater-assistedinjectionmoldedpart.
Figure1Schematicofexperimentalsetupforwaterassistedinjectionmolding.
Fortheabove-mentionedreasons,inthiswork,fourprocessingvariableswereinvestigatedintermsoftheireffectsonthewaterpenetrationlengthandresidualwallthicknessinwater-assistedinjectionmoldedpolypropylene(PP)curvedpipe.ThenTaguchimethodwasemployedtooptimizetheprocessingparameterstomaximizethepenetrationlength.Finally,thesamples,takenfromtwopositions,nearthebeginningandtheendofthewaterchannel,respectively,wereusedtoanalyzethecrystallizationbehaviorofmoldedpart.
3EXPERIMENTAL
Experimentalset-upandmaterialAwaterinjectionunit,whichmainlyconsistsofahighpressurewaterformingandconveyingunit(includingitstemperaturecontrolling),awaterinjector,andacontrolcircuit,wasrecentlydevelopedinthislaboratory.Thewaterinjectorusedwasanorifice-type.WAIMexperimentalinvestigationswerecarriedoutusingthenewlydevelopedwaterinjectionunitcombiningwithan80-tonconventionalinjectionmoldingmachine,whichhasahighestinjectionrateof84cm3/s.Figure1schematicallyshowstheexperimentalsetupforwater-assistedinjectionmolding.ThemoldusedforexperimentsisschematicallyshowninFigure2.Themoldcavityisacurvedonewithacircularcrosssectionof/18mm.Thecurvedmoldcavityhasanunwoundlengthof387.5mm.Thetemperatureofthemoldcouldberegulatedbyawater-circulatingmoldtemperaturecontroller.
Inthiswork,ashort-shotprocesswasused,inwhichthemoldcavityisfirstlypartiallyfilledwiththepolymermeltfollowedbyinjectingwaterintothecoreofthepolymermeltthroughthewaterinjector.Thewaterpenetratesintothecoreofthemeltandpushesthemeltagaintothemoldwall.Finally,thepolymercoolsdownandsolidifiesandahollowproductisobtained.
AninjectionmoldinggradePP,gradeCJS700fromPetrochinaGuangzhouPetrochemical,wasusedinthiswork.Itsmeltflowindexisabout8.35g/10min(at2308Cand2.16kg).
3.1Experimentalmethodology:
Thepresentexperimentswerecomposedoftwostages:
apreliminaryexperimentandanorthogonalexperiment.First,fourprocessingparameters,includingshort-shotsize,melttemperature,waterinjectiondelaytime,andwaterpressure,wereselectedandapreliminaryexperimentwasconductedbychangingoneoftheparametersineachexperiment.Indoingso,itwaspossibletobetterunderstandtheeffectofeveryprocessingparameter
Figure2Schematicofmoldusedforwater-assistedinjectionmolding.Alldimensionsareinmm.
JournalofAppliedPolymerScienceDOI10.1002/app
TABLEI
ProcessingParametersUsedinPreliminaryExperiments
Processing
Parameters
Short-shot
size(%)
Melt
temp(C)
Water
pressure(MPa)
Delay
time(s)
1
68.5
190
6
3
2
73.2
200
7
4
3
77.6
210
8
5
4
-
9
6
5
-
10
7
6
-
11
8
onthewaterpenetrationlengthandresidualwallthicknessofthewater-assistedinjectionmoldedcurvedpipe.Moreover,therangesofprocessingparameterscouldbedeterminedbyconductingafewexperiments.TableIliststhevaluesoftheseprocessingparameters.Preliminaryexperimentwasperformedbychangingoneparameteratatimeandkeepingtheothersconstant(highlightedinTableI).Thatis,whenchangingoneparameterineachexperiment,thevalueshighlightedwereusedforotherprocessingconditions.
Second,usingthesamefourfactorsasthoseinthepreliminaryexperiment,anorthogonalexperimentwasconductedtodeterminethebestsetofprocessingconditionthatmaximizesthewaterpenetrationlength.ThreelevelsforeachfactorwerechosenusingTaguchimethodasshowninTableII.SonineexperimentalrunsbasedontheorthogonalarrayL9(34)asshowninTableIIIwereconducted.Thesignal-to-noise(S/N)ratiowasusedtomeasurethequalitycharacteristicdeviatingfromthedesiredvalueinTaguchimethod.ThewaterpenetrationlengthsobtainedinexperimentswerethenanalyzedtocalculatetheS/Nratiotooptimizethewaterpenetration.ThemaximizationoftheS/Nratioleadstotheminimizationofanypropertythatissensitivetonoise.Alargerwaterpenetrationlengthisnormallyrequiredinmostindustrycasesbecausethatthelongerthewaterpenetrates,themorethewaterpressurecanpackthepolymermeltagainstthemoldwall.Bymaximizingthewaterpenetrationlength,theshrinkageaswellasthesinkmarkatthefarendofmoldedpartscanbeminimized.Therefore,thelarger-the-bettercharacteristicofS/Nratiohwasemployedfortheoptimizationofpenetrationlength:
wherenisthenumberofexperimentsandyiisthemeasuredproperty(waterpenetrationlengthinthiswork)fortheithexperiment.
ThentheresponsetableandfigureoftheS/Nratiowereobtained,fromwhichthesignificantfactorscouldbeidentified.ThecombinationofeachfactoratthelevelthatproducesthehighestS/Nratiowouldbetheoptimumprocessingcondition.Usingthisoptimumsetoffactorscouldgivethemaximumpenetrationlengthvalueinthisdesignofexperiment.
Tofurtherexaminetherelativesignificanceoftheprocessingparametersonthewaterpenetrationlength,astandardanalysisofvariance(ANOVA)wasperformed.
Duringexperiments,thecontrolcircuitinthewaterinjectionunitreceivedasignalfromtheinjectionmoldingmachineandcontrolledthetimeandpressureoftheinjectedwater.Fivepartsweremoldedforeachsetofprocessingconditions.
3.2Characterizationsofmoldedparts
Thelengthofwaterpenetrationinmoldedcurvedpipewasmeasured.Theresidualwal
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