【英文标准名称】:StandardPracticeforTransferMoldingTestSpecimensofThermosettingCompounds
【原文标准名称】:热固化合物的传递模塑试样的标准实施规程
【标准号】:ASTMD1896/D1896M-2010
【标准状态】:现行
【国别】:美国
【发布日期】:2010
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D20.09
【标准类型】:(Practice)
【标准水平】:()
【中文主题词】:
【英文主题词】:testspecimens;thermosettingcompounds;transfer-molding;Molding/extrusioncompounds/materials;Thermosettingplastics
【摘要】:Transfermoldingisparticularlysuitedtothermosettingmaterialsofintermediateplasticity.Fixedmoldingparameterscannotbespecifiedforeachtypeofmaterial.MoldingcompoundsofthesametypecomeinmanydifferentplasticitiesmeasuredinaccordancewithTestMethodsD3123andD3795.Consequently,foragivenmaterialtype,themoldingparametersrequiredtoproducesatisfactorytestspecimenswilloftenvarydependentontheplasticityofthespecificmaterialgrade.Themoldshowninthispracticeprovidesforasetoffivespecimens.However,ifonlycertainspecimensaredesired,theothercavitiescanbeblockedbyinsertinggateblanks.Typically,breathingofthemoldisnotrequiredtoreleasetrappedvolatilematterasthegasisfreetoflowfromtheventendofthemold.Thisisaparticularadvantageforheat-resistantcompoundsandreducesthetendencyformoldedspecimenstoblisterathighexposuretemperatures.Flowandknitlinesinamoldedpieceareoftensitesofmechanicalorelectricalweaknessandcanbefoundinsomedegreeofseveritythroughoutthemoldedpiece.Thesemisolidmoldingcompoundpassingthroughthegateissubjecttonon-Newtonianflowand,consequently,wrinklesandfoldsasittravelsdownthemoldcavity.Fibersandotherreinforcementsinthemoldingcompoundalignwiththeflowpatternand,consequently,canorientperpendiculartotheaxisofthebaratthecenterandparallelatthesurfaceofthebar.Moldtemperature,thermalconductivityandplasticityofthemoldingcompound,degreeofpreheat,andplungerpressureareparametersthatinfluencethetimetofillthemoldcavitiesandtheformationofknitlines.Note38212;Ifthetemperatureofthemoldisheldconstantandtheplungerpressurevariedforadesignatedthermosettingmoldingcompound,twoextremecharacteristicconditionscanbeobtained.Ifthepressureislow,thentheventendofthecavitywillnotfullyfill,andweldlineswillformbyincompleteknittingofthematerial.Ifthepressureistoohigh,themoldcavitywillfillfast,theoutsideofthespecimenwillcasehardenwhilethepressureisstillforcingmaterialoutthevent,andaball-and-socketgrainstructurewillbeobtained.Aball-and-socketstructureisanindicationofthemoldingcondition,andlowertestdatawillresult.Thermosettingcompoundscontaininglong-fiberfillerssuchasglassroving,choppedcloth,orshavingscanbeusedbutarenotrecommendedfortransfermolding.Thesefillermaterialstendtobreak,tear,orballinpassingthroughthegatesofthemold,therebynotoptimizingtheirpotentialstrength.TheIzodimpactstrengthoftransfermoldedspecimensofmoldingcompoundscontainingshortfiberswillgenerallybelowerthanthevaluesobtainedusingcompression-moldingmethods.Quiteoftentheimpactstrengthwillvaryalongtheaxisofthebarduetomoldingparameters,flowpattern,andfiberorientation.Theflexuralandtensilestrengthoftransfermoldedspecimensofmoldingcompoundscontainingshortfiberswillgenerallybehigherthanthevaluesobtainedusingcompression-moldingmethods.Flexuraltestsareparticularlysensitivetotransfermoldingduetothethinresinskinformedatthesurfaceofthebarduringthefinalfillingofthecavityandpressurebuildup.1.1Thispracticecoversageneralprocedureforthetransfermoldingofmechanicalandelectricaltestspecimensofthermosettingmoldingmaterials.Note18212;Theutilityofthispracticehasbeendemonstratedforthemoldingofthermosettingmoldingcompoundsexhib......
【中国标准分类号】:G31
【国际标准分类号】:83_140_99
【页数】:4P.;A4
【正文语种】:英语