The Effects of Mold Designon the Pore Morphology ofPolymers Produced withMuCell_ Technology.doc
太阳能电动汽车数字仪表盘设计（全套含CAD图纸）
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THEEFFECTSOFMOLDDESIGNONTHEPOREMORPHOLOGYOFPOLYMERSPRODUCEDWITHMUCELL_TECHNOLOGYABSTRACTINTHISSTUDYTWOMOLDSWEREDESIGNEDANDUSEDINMUCELL_TECHNOLOGYTOGENERATEIMPLANTSWITHAPOROUSSTRUCTURETOARRIVETHEDESIREDPORESTRUCTUREMANYPROCESSPARAMETERSWEREINVESTIGATEDFORINDICATINGTHEEFFECTSOFPROCESSPARAMETERSONTHEPOREMORPHOLOGYTHISPROCESSPARAMETERINVESTIGATIONWASPERFORMEDONEACHMOLDRESPECTIVELY,SOTHATTHEINFLUENCESOFTHEMOLDDESIGNONTHEPOREMORPHOLOGYHAVEBEENRESEARCHEDBYTHESAMEPROCESSPARAMETERSETTINGITWASFOUNDTHATTHEMOLDDESIGNALSOHADEFFECTSONTHEPORESTRUCTUREINMUCELL_TECHNOLOGYAPROPERMOLDDESIGNCOULDIMPROVETHEGENERATEDPORESTRUCTURE,SUCHASPOROSITY,POREDIAMETER,ANDINTERCONNECTIVITYKEYWORDSMOLDDESIGN,CELLMORPHOLOGY,MUCELL_,INJECTIONMOLDING,MEDICALIMPLANT,POROUSPOLYMER,POLYURETHANEINTRODUCTIONMUCELLTECHNOLOGY,ASANEFFECTIVEMICROCELLULARINJECTIONMOLDINGPROCESS,ISWIDELYUSEDINAUTOMOBILEANDFURNITUREINDUSTRIESINMOSTCASES,MUCELL_TECHNOLOGYISUSEDTOSAVERAWMATERIALS,BUTITISALSOUSEDTOPRODUCEIMPLANTSWITHCLOSEDPOROUSSTRUCTURE1ITUSESCO2ASBLOWINGAGENT,WHICHISINJECTEDINTHEPLASTICIZATIONSECTIONOFTHEINJECTIONMOLDINGMACHINEFIGURE1THEBLOWINGAGENTISINJECTEDINTOTHEPOLYMERMELTTHROUGHTHEGASSUPPLYLINEANDINJECTOR,INITSSUPERCRITICALSTATE,BYTHEPLASTICIZATIONPHASEOFTHEINJECTIONMOLDINGMACHINEAFTERTHEPLASTICIZATIONTHEMIXTUREOFPOLYMERMELTANDGASISINJECTEDTHROUGHTHENOZZLEINTOTHEMOLD,WHERETHEFOAMSTRUCTURECANBEGENERATEDDUETOTHEQUICKPRESSUREDROPINTHEMOLDTHEMAINPRODUCTSWHICHAREPRODUCEDTODAYWITHMUCELL_TECHNOLOGYHAVECLOSEDCELLULARFOAM24THEMUCELLMICROCELLULARFOAMINJECTIONMOLDINGTECHNOLOGYISACOMPLETEPROCESSANDEQUIPMENTTECHNOLOGYWHICHFACILITATESEXTREMELYHIGHQUALITYANDGREATLYREDUCESPRODUCTIONCOSTSTHEMUCELLPROCESSINVOLVESTHECONTROLLEDUSEOFGASINITSSUPERCRITICALSTATETOCREATEAFOAMEDPARTTHEMUCELLTECHNOLOGYISTARGETEDATPRECISIONANDENGINEEREDPLASTICCOMPONENTSWITHMAXIMUMWALLTHICKNESSESOFLESSTHAN3MMTHEMUCELLPROCESSGENERALLYOFFERSA5075IMPROVEMENTINKEYQUALITYMEASURES,SUCHASFLATNESS,ROUNDNESS,ANDWARPAGE,ALSOELIMINATINGALLSINKMARKSTHESEIMPROVEMENTSRESULTFROMTHEFACTTHATRELATIVELYUNIFORMSTRESSPATTERNSARECREATEDINTHEMOLDEDPARTRATHERTHANNONUNIFORMSTRESSCHARACTERISTICOFSOLIDMOLDINGASADIRECTRESULTOFTHEUNIFORMSTRESSANDSHRINKAGEASSOCIATEDWITHTHEMUCELLPROCESSWHICHOCCURSBECAUSETHEPACKANDHOLDPHASEOFTHEMOLDINGCYCLEISELIMINATED,THEPARTSTHATAREPRODUCEDTENDTOCOMPLYFARMORECLOSELYWITHTHEMOLDSHAPEAND,PRESUMABLY,THEDIMENSIONALSPECIFICATIONSOFTHEPARTITSELFTHISMEANSTHATWHENUSINGTHEMUCELLPROCESS,FEWERMOLDITERATIONSARENEEDEDTOPRODUCEACOMPLIANTPART,SAVINGTIMEANDCOSTTHEQUALITYADVANTAGESOFTHEMUCELLPROCESSARECOMPLEMENTEDBYCERTAINDIRECTECONOMICADVANTAGES,INCLUDINGTHEABILITYTOPRODUCE2033MOREPARTSPERHOURONAGIVENMOLDEDMACHINE,ANDTHEABILITYTOMOLDPARTSONLOWERTONNAGEMACHINESASARESULTOFTHEVISCOSITYREDUCTIONANDTHEELIMINATIONOFTHEPACKINGREQUIREMENTTHATACCOMPANIESTHEUSEOFSUPERCRITICALGASTHIS25PAGEPROCESSINGHANDBOOKCOVERSALLASPECTSOFTHEPROCESSFROMSETUPTOTROUBLESHOOTINGTOOPTIMIZINGRESULTSITISPRIMARILYUSEFULTOCOMPANIESWHOAREMANUFACTURINGORAREPLANNINGTOMANUFACTUREPARTSUSINGTHEMUCELLINJECTIONMOLDINGPROCESSPLEASECONTACTTREXELFORACOPYOFTHISPUBLICATIONTHEMUCELLINJECTIONMOLDINGPROCESSINVOLVESTHEHIGHLYCONTROLLEDUSEOFGASINITSSUPERCRITICALSTATESCFTOCREATEDMILLIONSOFMICRONSIZEDVOIDSINTHINWALLMOLDEDPARTSLESSTHAN3MMWITHTHECORRECTEQUIPMENTCONFIGURATION,MOLDDESIGN,ANDPROCESSINGCONDITIONSTHESEMICROCELLULARVOIDSARERELATIVELYUNIFORMINSIZEANDDISTRIBUTIONTHEVOIDSARECREATEDORNUCLEATEDASARESULTOFHOMOGENEOUSNUCLEATIONTHATOCCURSWHENASINGLEPHASESOLUTIONOFPOLYMERANDGASCOMMONLYNITROGEN,BUTOCCASIONALLYCARBONDIOXIDEPASSESTHROUGHTHEINJECTIONGATEINTOTHEMOLDTHESINGLEPHASESOLUTIONISCREATEDTHROUGHTHEOPERATIONOFACONVENTIONALINJECTIONMOLDINGMACHINEWHICHHASBEENMODIFIEDTOALLOWTHECREATIONOFASINGLEPHASESOLUTIONTHEKEYMODIFICATIONSTOTHESYSTEMINVOLVETHEUSEOFAPRECISIONSCFDELIVERYSYSTEMTODELIVERSCFTOSPECIALINJECTORSBASEDONMASSFLOWMETERINGPRINCIPLESTHESCFISTHENINJECTEDINTOTHEBARRELWHEREITISMIXEDWITHTHEPOLYMERVIAASPECIALLYDESIGNEDSCREWASHUTOFFNOZZLEMAINTAINSTHESINGLEPHASESOLUTIONWHILETHEINJECTIONMOLDINGSCREWMAINTAINSSUFFICIENTBACKPRESSUREATALLTIMESTOPREVENTPREMATUREFOAMINGORTHELOSSOFPRESSUREWHICHWOULDALLOWTHESINGLEPHASESOLUTIONTORETURNTOTHETWOPHASESOLUTIONTREXELHASRECENTLYPUBLISHEDACOMPREHENSIVEMUCELLPROCESSGUIDEINENGLISH,CHINESE,JAPANESE,ANDGERMANWHICHEXPLAINSINSTEPBYSTEPDETAILHOWTOAPPLYTHEMUCELLPROCESSINTHEMANUFACTUREOFMUCELLINJECTIONMOLDEDCOMPONENTSTHIS25PAGEPROCESSINGHANDBOOKCOVERSALLASPECTSOFTHEPROCESSFROMSETUPTOTROUBLESHOOTINGTOOPTIMIZINGRESULTSITISPRIMARILYUSEFULTOCOMPANIESWHOAREMANUFACTURINGORAREPLANNINGTOMANUFACTUREPARTSUSINGTHEMUCELLINJECTIONMOLDINGPROCESSPLEASECONTACTTREXELFORACOPYOFTHISPUBLICATIONTHEMUCELLMICROCELLULARFOAMINJECTIONMOLDINGPROCESSFORTHERMOPLASTICSMATERIALSPROVIDESUNIQUEDESIGNFLEXIBILITYANDCOSTSAVINGSOPPORTUNITIESNOTFOUNDINCONVENTIONALINJECTIONMOLDINGTHEMUCELLPROCESSALLOWSFORPLASTICPARTDESIGNWITHMATERIALWALLTHICKNESSOPTIMIZEDFORFUNCTIONALITYANDNOTFORTHEINJECTIONMOLDINGPROCESSTHECOMBINATIONOFDENSITYREDUCTIONANDDESIGNFORFUNCTIONALITYOFTENRESULTSINMATERIALANDWEIGHTSAVINGSOFMORETHAN20BYREPLACINGTHEPACKMAKINGCONSUMERPRODUCTSPERFECTLYSUITABLEFORRECYCLINGWITHINTHEORIGINALPOLYMERCLASSIFICATIONANDALLOWINGREGRINDMATERIALTOREENTERTHEPROCESSFLOWTHENUMEROUSCOSTANDPROCESSINGADVANTAGESHAVELEDTORAPIDGLOBALDEPLOYMENTOFTHEMUCELLPROCESSPRIMARILYINAUTOMOTIVE,CONSUMERELECTRONICS,MEDICALDEVICE,PACKAGINGANDCONSUMERGOODSAPPLICATIONSMICROCELLULARFOAMSREFERTOTHERMOPLASTICFOAMSWITHCELLSOFTHEORDEROF10MINSIZETYPICALLYTHESEFOAMSARERIGID,CLOSEDCELLSTRUCTURESALTHOUGHRECENTLYTHEREISMUCHINTERESTINCREATINGOPENCELL,POROUSSTRUCTURESTHATHAVECELLSINTHISSIZERANGETHEMICROCELLULARPROCESSTHATSPARKEDTHEGROWTHINTHISFIELDOVERTHEPASTTWODECADESWASINVENTEDATMASSACHUSETTSINSTITUTEOFTECHNOLOGY,USA,INEARLYEIGHTIES1,INRESPONSETOACHALLENGEBYFOODANDFILMPACKAGINGCOMPANIESTOREDUCETHEAMOUNTOFPOLYMERUSEDINTHEIRINDUSTRIESASMOSTOFTHESEAPPLICATIONSUSEDSOLID,THINWALLEDPLASTICS,REDUCINGTHEIRDENSITIESBYTRADITIONALFOAMINGPROCESSESTHATPRODUCEDBUBBLESLARGERTHAN025MMWASNOTFEASIBLEDUETOEXCESSIVELOSSOFSTRENGTHTHUSWASBORNTHEIDEATOCREATEMICROCELLULARFOAM,WHEREWECOULDHAVE,FOREXAMPLE,100BUBBLESACROSSONEMMTHICKNESS,ANDEXPECTTOHAVEAREASONABLESTRENGTHFORTHEINTENDEDAPPLICATIONSITWOULDBEREASONABLETOSAYTHATTHEPOTENTIALOFMICROCELLULARFOAMSHASYETTOBEREALIZEDTHESEMATERIALSHAVENOTYETAPPEAREDINMASSPRODUCEDPLASTICITEMS,ANDTHEPROMISEDSAVINGSINMATERIALSANDASSOCIATEDCOSTSHAVEYETTOMATERIALIZETHISISLARGELYDUETOMANUFACTURINGDIFFICULTIESENCOUNTEREDINSCALINGUPFORLARGESCALEPRODUCTIONHOWEVER,ENTHUSIASMFORTHESEMATERIALSREMAINSHIGH,ANDTODAYRESEARCHERSANDCOMMERCIALENTERPRISESONEVERYCONTINENTAREINAGLOBALRACETOHARNESSTHEPOTENTIALBENEFITSMUCHHASBEENLEARNEDABOUTTHEPROCESSINGANDPROPERTIESOFMICROCELLULARFOAMSSINCETHEFIRSTPATENTWASGRANTEDIN19842ANEARLYREVIEWOFTHESUBJECTAPPEAREDIN19933INTHISCHAPTERTHESTATEOFTHEARTOFPROCESSINGWILLBEREVIEWEDINTHENEXTSECTION,FOLLOWEDBYADISCUSSIONOFSTRUCTUREANDPROPERTIESTHISCHAPTERWILLCONCLUDEWITHALOOKATSOMEOFTHECURRENTRESEARCHDIRECTIONSINVOLVINGMICROCELLULARTECHNOLOGYALTHOUGHINNOVATIONSINPROCESSINGHAVEDEVELOPEDATARAPIDPACE,THEPROPERTYDATAONMICROCELLULARFOAMSHASBEENSLOWINCOMINGTHEEARLYPUBLICATIONSONMICROCELLULARFOAMSCONJECTUREDTHATTHEMICROCELLULARSTRUCTURE,BELIEVEDTOBEONASCALETHATWASSMALLERTHANTHECRITICALFLAWSIZEFORPOLYMERS,WOULDENABLETHESEFOAMSTORETAINTHEIRMECHANICALPROPERTIESEVENASTHEDENSITYWASREDUCEDNOQUANTITATIVEINFORMATIONONTHECRITICALFLAWSIZEWASEVERPRESENTED,NORWASANYPROPERTYDATAPRESENTEDINSUPPORTOFTHEHYPOTHESISTHISISLIKELYTOBEDUETOTHEEMPHASISPLACEDONPROCESSDEVELOPMENT,ASOPPOSEDTOPROPERTYCHARACTERIZATION,INTHEEARLYYEARSOFEVOLUTIONOFTHISFIELDOVERTIME,HOWEVER,THISCONJECTUREHASBECOMEAMYTHTHATMICROCELLULARMATERIALSAREASSTRONGASTHESOLIDPOLYMERSBUTHAVEALOWERDENSITY,THUSPROVIDINGANOPPORTUNITYTOLOWERCOSTSWITHNOPENALTYINPERFORMANCETHETENSILEPROPERTYDATA4SHOWSTHATTHETENSILESTRENGTHOFMICROCELLULARFOAMSDECREASESINPROPORTIONTOTHEFOAMDENSITY,ANDCANBEAPPROXIMATEDQUITEWELLBYTHERULEOFMIXTURESTHUSA50RELATIVEDENSITYFOAMCANBEEXPECTEDTOHAVE50OFTHESTRENGTHOFTHESOLIDPOLYMERFIGURE115SHOWSRELATIVETENSILESTRENGTHASAFUNCTIONOFRELATIVEFOAMDENSITYFORANUMBEROFMICROCELLULARPOLYMERSINTHISFIGURETHERELATIVETENSILESTRENGTH,ISOBTAINEDBYDIVIDINGTHETENSILESTRENGTHOFTHEFOAMBYTHETENSILESTRENGTHOFTHESOLIDPOLYMERSIMILARLY,THERELATIVEDENSITYISFOAMDENSITYDIVIDEDBYTHESOLIDPOLYMERDENSITYINFIGURE116WEHAVEPLOTTEDTHESTRENGTHDATAONASPECIFICBASISTHUSTHESPECIFICRELATIVETENSILESTRENGTHFORTHEFOAMOFAGIVENRELATIVEDENSITYISOBTAINEDBYDIVIDINGTHERELATIVETENSILESTRENGTHBYTHERELATIVEDENSITYFIGURE116SHOWSTHATONASPECIFICBASIS,THETENSILESTRENGTHOFMICROCELLULARFOAMSISESSENTIALLYCONSTANTOVERTHEENTIRERANGEOFFOAMDENSITIESUNFORTUNATELY,SIMILARDATAONCONVENTIONALFOAMSISNOTREADILYAVAILABLEFORADIRECTCOMPARISONWITHMICROCELLULARFOAMSAUNIQUEASPECTOFDATAINFIGURE115ISTHATINTHERELATIVEDENSITYRANGEOF01TO05,THEMICROCELLULARFOAMSREPRESENTNOVELMATERIALSFORTHEENGINEERWITHPROPERTIESNOTPREVIOUSLYAVAILABLEMOSTCONVENTIONALFOAMSFALLEITHERINTHELOWDENSITYREGIONRELATIVEDENSITYLESSTHAN01ORBELONGINTHESTRUCTURALFOAMSCATEGORYRELATIVEDENSITYGREATERTHAN05THEMODULUSOFMICROCELLULARFOAMSCANBEREASONABLYESTIMATEDBYTHEGIBSONASHBYCUBICCELLMODEL5,WHICHPREDICTSTHATTHERELATIVETENSILEMODULUSEQUALSTHESQUAREOFTHERELATIVEDENSITYTHEGASCOMPOSITIONINTHECELLMAYAFFECTTHELONGTERMTHERMALCONDUCTIVITYOFTHEFOAMS6MICROSTRUCTURES,TENSILESTRENGTH,ANDTHERMALEXPANSIONPROPERTIESFORANUMBEROFLOWDENSITYFOAMSHAVEBEENREVIEWEDBYWILLIAMSANDWROBLESKI7FATIGUEANDCREEPBEHAVIOURSOFMICROCELLULARPOLYCARBONATEFOAMSHAVEBEENINVESTIGATED810ANINTERESTINGRESULTFROMFATIGUESTUDIESISTHATINTRODUCTIONOFVERYSMALLBUBBLESINPC,WITHLESSTHAT1REDUCTIONOFDENSITY,LEDTOATHIRTYFOLDINCREASEINFATIGUELIFECOMPAREDTOTHESOLIDPCTHISMIGHTSUGGESTAPROCESSSIMILARTOHEATTREATMENTOFMETALS,WHEREAPCPARTMAYBESATURATEDWITHCARBONDIOXIDEAT5MPAANDTHENHEATEDTOSAY60CTOINTRODUCETHEMICROCELLULARSTRUCTUREWITHOUTANAPPRECIABLEDENSITYCHANGE,TOINCREASETHEFATIGUELIFEOFAPARTDUETOTHELOWPROCESSINGTEMPERATURES,VERYLITTLEDIMENSIONALCHANGEWASOBSERVEDINTHEEXPERIMENTSTHETENSILEDATAFORALLGASPOLYMERSYSTEMSINVESTIGATEDFALLSONONEREDUCEDPLOTWHERERELATIVETENSILESTRENGTHCANBEPLOTTEDAGAINSTTHERELATIVEDENSITY,ASISSHOWNINFIGURE115HOWEVER,ENERGYABSORPTIONMEASURES,SUCHASANIMPACTTEST,AREMORESENSITIVETOVARIATIONSFROMPOLYMERTOPOLYMER,ANDTHERESULTSCANNOTBEGENERALIZEDGARDNERIMPACTSTRENGTHFORPVCFOAMS11WITHRELATIVEDENSITIESOF05ANDHIGHERITISSEENTHATTHEIMPACTSTRENGTHDECREASESLINEARLYWITHFOAMDENSITYTHISRESULTISCONTRARYTOTHEPOPULARBELIEF,LONGHELDWITHOUTPROOF,THATTHEMICROCELLULARSTRUCTUREWILLALWAYSIMPROVETHEENERGYABSORPTIONBEHAVIORDUETOTHEINCREASEDRESISTANCETOCRACKPROPAGATIONOFFEREDBYTHEMICROVOIDS12SOMESTUDIESHAVEINVESTIGATEDTHERELATIONSBETWEENTHEKEYPROCESSPARAMETERSINMUCELL_TECHNOLOGYANDPRODUCEDCELLULARFOAMSTRUCTURE1,5,6ITWASFOUNDTHATTHEPOREMORPHOLOGYINMUCELL_PROCESSCOULDBEADJUSTEDTHROUGHVARYINGTHEPROCESSPARAMETERSHOWEVER,THEREISCURRENTLYNOLITERATUREREGARDINGTHEEFFECTSOFMOLDDESIGNONTHEPOREMORPHOLOGYBYMUCELL_TECHNOLOGYINTHISSTUDYTWOMOLDSWEREDESIGNEDANDUSEDINMUCELL_PROCESSTOGENERATEIMPLANTSWITHAPOROUSSTRUCTUREFORMEDICALUSETHERESEARCHOFPROCESSPARAMETERSWASINDEPENDENTLYPERFORMEDONTHESETWOMOLDSBYCOMPARINGTHEPORESTRUCTUREOFIMPLANTSMADEFROMTWOMOLDSATTHESAMEPROCESSPARAMETERSETTING,THEINFLUENCESOFTHEMOLDDESIGNONTHEPOROUSSTRUCTUREWEREINVESTIGATEDFIGURE1DRAFTOFTHEMUCELL_TECHNOLOGYMATERIALSANDMETHODSPOLYMERPROCESSINGMEDICALGRADETHERMOPLASTICPOLYURETHANETPUTEXIN_985,BAYER,PA,USAWASCHOSENASRAWMATERIALFORTHEIMPLANTANINJECTIONMOLDINGMACHINEKM125520C2,KRAUSSMAFFEITECHNOLOGIESGMBH,MUNICH,GERMANYWITHATEMPERATURECONTROLUNITFORCOOLINGTHEMOLD90S/6/TS22/1K/RT45,REGLOPLAS,STGALLEN,SWITZERLANDWASUSEDFORTHEPRODUCTIONOFTHESAMPLESTHEINJECTIONMOLDINGMACHINEWASEQUIPPEDWITHAMUCELL_PACKAGEBYTHETREXELINC,WOBURN,MA,USATHEMUCELL_PACKAGEISSCHEMATICALLYSHOWNINFIGURE1THEBLOWINGAGENTISINJECTEDINTOTHEPOLYMERMELTTHROUGHTHEGASSUPPLYLINEANDINJECTOR,INITSSUPERCRITICALSTATE,BYTHEPLASTICIZATIONPHASEOFTHEINJECTIONMOLDINGMACHINEAFTERTHEPLASTICIZATIONTHEMIXTUREOFPOLYMERMELTANDGASISINJECTEDTHROUGHTHENOZZLEINTOTHEMOLD,WHERETHEFOAMSTRUCTURECANBEGENERATEDDUETOTHEQUICKPRESSUREDROPINTHEMOLDCO2WASUSEDASBLOWINGAGENTCO2PROTECTIVEGASDIN32525C1,WESTFALENAG,MUNSTER,GERMANYINORDERTOPRODUCETHEIMPLANT,TWOPARTICULARMOLDSWEREDESIGNEDANDUSEDTHETECHNICALDRAWINGSOFMOLDEDPARTSFROMMOLDAANDMOLDBARESHOWNINFIGURE2THEMOLDAHADSIXRINGSHAPEDIMPLANTSANDWASJUSTUSEDFORTHEPRELIMINARYTESTOFTHEFEASIBILITYOFTHEFOAMINGPROCESSANDPARAMETERRESEARCHTHEMOLDBWASDESIGNEDWITHSIXSOLIDDISKSHAPEDIMPLANTBASEDONTHERESULTSOFINVIVOTESTOFIMPLANTSFROMMOLDA,FORAHIGHERBIOLOGICALREQUIREMENTANDPROSPECTIVEPRODUCTIONFIGURE2DIFFERENTMOLDDESIGNSTWOMOLDSHAVESIMILARGATE,RUNNER,ANDSPRUESTHEMOLDBHASASHORTERPOLYMERMELTFLOWOFMOLDCAVITYANDTHEL/DLENGTH/THICKNESSOF28,WHEREASTHISL/DFORMOLDAIS47THISMEANSTHEMOLDEDPARTFROMMOLDBISRELATIVELYTHICKERBUTSHORTERTHEADVANTAGEOFMOLDBISTHATTHEENERGYLOSSOFMELTFLOW,WHICHDOMINATESTHECELLNUCLEATIONANDGROWTH,ISREDUCEDDUETOTHESHORTERFLOWPATHLOWL/DASARESULTBETTERPOREMORPHOLOGY,SUCHASBIGGERMEANPORESIZE,HIGHERPOROSITY,ANDSOON,COULDBEEXPECTEDONTHEOTHERHANDTHEMOLDBHASABIGGERCAPACITYWHICHMEANSMOREPOSSIBILITIESOFPARAMETERVARIATIONTHEDISADVANTAGEOFMOLDBISTHATRELATIVETHICKERMOLDEDPARTWILLLEADTOANINCOMPLETEFILLINGOFTHECAVITYOFMOLDB,ALONGCOOLINGTIME,ANDSIGNIFICANTSHRINKAGEOFMOLDEDPART,INNORMALINJECTIONMOLDINGPROCESSTHESEPROBLEMSCOULDBEPARTIALLYORWHOLLYRESOLVEDIFTHEFOAMINGPROCESSISAPPLIEDDUETOTHEEXPANSIONOFFOAMEDPOLYMEREXPERIMENTALSTRATEGYTHECHOICEOFTHECHANGEABLEPARAMETERSWASMADEBASEDONTHEKNOWLEDGEGIVENBYNUCLEATIONTHEORYANDLITERATURESEARCH5,7THERANGESOFVARIABLEPARAMETERSANDTHEVALUESOFFIXEDPARAMETERSAREPRESENTEDINTABLE1THEEXPERIMENTSWEREDONEBYVARYINGONEOFVARIABLEPARAMETERSWHILEKEEPINGTHEOTHERSCONSTANTTHEWHOLEPROCESSPARAMETERSINVESTIGATIONWASPERFORMEDONTWOMOLDSRESPECTIVELYTHEIMPLANTSFROMTWOMOLDS,WHICHWEREUSEDTOBECOMPARED,WEREPRODUCEDATEXACTLYSAMEPROCESSPARAMETERS,SOTHATTHEEFFECTSOFDIFFERENTMOLDSWERESHOWNCHARACTERIZATIONOFMACROANDMICROSTRUCTURESSCANNINGELECTRONMICROSCOPYSEMJEOLJSM6060LV,JEOLLTD,TOKYO,JAPANWASUSEDFORTHEOBSERVATIONOFTHEPOREMORPHOLOGYOFTHECROSSSECTIONOFIMPLANTTHESAMPLESWERESLICEDWITHASCALPELANDTHENCOATEDWITHATHINGOLDLAYERBYUSINGASPUTTERCOATERSCD005,BALTECAG,BALZERS,LICHTENSTEINUNDERHIGHVACUUMWITHAVOLTAGERANGEBETWEEN5AND15KVCHARACTERISTICSOFPOROUSSTRUCTURESUCHASPORESIZEANDPOROSITYCANBECALCULATEDBYCOUNTINGTHEAVERAGECELLNUMBERANDSIZEOFSEVERALSEMIMAGESFROMONESAMPLEONECUTAREAWITHCERTAINSIZEWASCHOSENANDALLPORESWEREMEASUREDMANUALLYWITHTHEHELPOFSOFTWAREOFDIGITALMICROSCOPEVHX500,KEYENCECORPORATION,OSAKA,JAPANTHEAVERAGEDIAMETEROFPORESWASCALCULATEDASDMEASUREDDUETOTHEFACTTHATTHEPORESSHOWNINTHEMICROGRAPHSARE2DPROJECTIONSOF3DOBJECTS,THEIRMAXIMUMDIAMETERMAYNOTBEREPRESENTEDINTHEIMAGEFOLLOWINGEQUATIONWASUSEDFORDETERMINATIONOFTHEMAXIMUMSPHERICALDIAMETER,NAMEDCORRECTEDMEDIANPOREDIAMETER,FROMTHEMEASUREDPOREDIAMETER1（1）MICROCTSKYSCAN1172,SKYSCAN,KONTICH,BELGIUMWASUSEDTOQUANTITATIVELYMEASURETHEPOROUSINTERCONNECTIVITYOFIMPLANTSTHREE8MM_11MMCYLINDRICALSAMPLESFROMEACHIMPLANTN3AT7MMRESOLUTIONUSINGAVOLTAGEOF59KV,ANDACURRENTOF167MAIMAGERECONSTRUCTIONANDANALYSISWERECONDUCTEDUSINGTHESOFTWAREPACKAGEPROVIDEDBYSKYSCANSAMPLESWEREROTATED1808AROUNDTHEIRLONGAXISANDTHREEABSORPTIONIMAGESWERERECORDEDEVERY0400OOFROTATIONTHESERAWIMAGESOFTHESAMPLESWERERECONSTRUCTEDWITHTHESTANDARDSKYSCANRECONSTRUCTIONSOFTWARENRECONTOSERIALCORONALORIENTEDTOMOGRAMSUSING3DCONEBEAMRECONSTRUCTIONALGORITHMFORTHERECONSTRUCTION,BEAMHARDENINGWASSETTO20ANDRINGARTEFACTREDUCTIONTO12THEIMAGEANALYSISOFTHERECONSTRUCTEDAXIALBITMAPIMAGESWASPERFORMEDUSINGTHESTANDARDSKYSCANSOFTWARECTANANDCTVOLFIRST,ATHRESHOLDINGANALYSISWASPERFORMEDTODETERMINETHETHRESHOLDVALUEFORWHICHTHEGREYSCALETOMOGRAMSOFSCAFFOLDSWEREMOSTACCURATELYREPRESENTEDBYTHEIRBINARISEDCOUNTERPARTSINTERMSOFPOROSITYTHETHRESHOLDVALUEWASSETBETWEEN65AND225FORTHISSTUDYADDITIONALNOISEWASREMOVEDBYTHEDESPECKLINGFUNCTIONALLOBJECTSSMALLERTHAN500VOXELSANDNOTCONNECTEDTOTHE3DBODYWERETHUSREMOVEDPRIORTOFURTHERANALYSISINORDERTOELIMINATEPOTENTIALEDGEEFFECTS,ACYLINDRICALVOLUMEOFINTERESTVOIWITHADIAMETEROF5MMANDAHEIGHTOF25MMWASSELECTEDINTHECENTREOFTHESCAFFOLDSCAFFOLDPOROSITYWASTHENCALCULATEDASFOLLOWS（2）10VOLFBINRSEDOJCTSAFLDMTERIALNVOIPORSITYALLIMAGESUNDERWENT3DANALYSIS,FOLLOWEDBYTHEQUANTIFICATIONOFINTERCONNECTIVITYUSINGTHESHRINKWRAPFUNCTION,WHICHALLOWSMEASURINGTHEFRACTIONOFPOREVOLUMEINASCAFFOLDTHATWASACCESSIBLEFROMTHEOUTSIDETHROUGHOPENINGSOFACERTAINMINIMUMSIZE8ASHRINKWRAPPROCESSWASPERFORMEDBETWEENTWO3D061MEASURDCORDMEASUREMENTSTOSHRINKTHEOUTSIDEBOUNDARYOFTHEVOIINASCAFFOLDTHROUGHOPENINGSTHESIZEOFWHICHWASEQUALTOORLARGERTHANATHRESHOLDVALUE0280MMWEREUSEDINTHISSTUDYINTERCONNECTIVITYWASCALCULATEDASFOLLOWS（3）RESULTSANDDISCUSSIONTHESEMIMAGESFIGURE3SHOWTHEPORESTRUCTURESOFFOAMEDIMPLANTSFROMTWOMOLDSINTHEINJECTIONSPEEDVARIATIONWITHVALUEOF30MM/S,WHENTHEOTHERPROCESSPARAMETERSWEREKEPTUNCHANGEDWEIGHTREDUCTIONOF35,PLASTICIZINGTEMPERATUREOF1808C,PLASTICIZINGPRESSUREOF180BAR,MOLDTEMPERATUREOF258C,ANDGASCONTENTOF2ITWASFOUNDTHATTHELEFTIMAGE,WHICHCAMEFROMTHEFOAMEDIMPLANTFROMMOLDB,SHOWEDASIGNIFICANTLARGERPORESIZETHANRIGHTIMAGEFROMMOLDATHEINTERCONNECTIVEPORESIZE9,10WHICHMEANSTHEWINDOWBETWEENTWOCONNECTIVEPORESHASALSOTHESAMECHANGETRENDFROMFIGURE3ITCOULDBEQUALITATIVELYSEENTHATTHEIMPLANTSFROMMOLDBHADALARGERPORESIZEANDINTERCONNECTIVEPORESIZEANDPOSSIBLYHADAHIGHERPOROSITYTHANTHOSEFROMMOLDAATTHESAMEPROCESSPARAMETERFIGURE3DIFFERENTPORESTRUCTURESOFMOLDBLEFTANDMOLDARIGHTATTHEINJECTIONSPEEDOF30MM/SSHRINKWAPMV10INTERCOTIVYFIGURE4DIFFERENCESOFTHEPOROSITYATINJECTIONSPEEDVARIATIONITWASFOUNDFROMFIGURE4THATTHEIMPLANTSFROMMOLDBATEVERYDIFFERENTINJECTIONSPEEDHADAHIGHERPOROSITYTHANTHEIMPLANTSFROMMOLDATHEPOROSITYRANGEOFIMPLANTSFROMMOLDBWASBETWEEN73AND79,WHEREASBYMOLDATHISPOROSITYRANGEWASBETWEEN60AND67ATTHESAMETIMETHESTANDARDDEVIATIONOFTHEPOROSITYFROMMOLDBWASSIGNIFICANTLYSMALLERTHANTHEDEVIATIONBYMOLDAFIGURE5THEMEANPORESIZEFROMTWOMOLDSATDIFFERENTINJECTIONSPEEDSFIGURE5SHOWSTHEMEANPORESIZEOFTWOMOLDSBYDIFFERENTINJECTIONSPEEDSTHEPORESIZEDECREASEDWITHRISEOFTHEINJECTIONSPEEDFORTWOMOLDSTHESAMERESULTWASALSOFOUNDBYOTHERSTUDY11THEPOREDIAMETEROFTHEIMPLANTSFROMMOL
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