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1、Polymer51(2010)3784e3792ContentslistsavailableatScienceDirectPolymerjournalhomepage:www.elsevier.com/locate/polymerInfluenceofprevioushistoryonphysicalaginginthinglassypolymerfilmsasgasseparationmembranesBrandonW.Rowe,BennyD.Freeman,D.R.Paul*DepartmentofChemicalEngineering,Te
2、xasMaterialsInstituteandCenterforEnergyandEnvironmentalResources,TheUniversityofTexasatAustin,Austin,TX78712,UnitedStatesarticleinfoabstractArticlehistory:Thephysicalagingbehaviorofthinglassypolysulfone(PSF)films(w125nm)withdifferentpreviousReceived1April2010historieswastrac
3、kedusinggaspermeabilitymeasurements.TheinitialstatesofthesematerialswereReceivedinrevisedformmodulatedbythermalannealingatfixedtemperaturesbelowtheglasstransitionorbyexposuretohigh31May2010pressure(800psig(56.2bara))CO2forvarioustimes.Regardlessoftheprevioushistory,thenature
4、oftheAccepted3June2010agingresponseinthesesampleswasconsistentwiththeagingbehaviorofanuntreatedfilmthatwasAvailableonline9June2010freshlyquenchedfromaboveTg,i.e.,permeabilitydecreasedandpuregasselectivityincreasedwithagingtime.However,theextentofaging-inducedchangesintranspo
5、rtpropertiesofthesematerialsdependedKeywords:stronglyonprevioushistory.TheagingbehaviorwasdescribedusingStruik’sagingmodelbyallowingPhysicalagingGaspermeabilitytheinitialconditionstodependoneachsample’sprevioushistory.MembranesÓ2010ElsevierLtd.Allrightsreserved.1.Introducti
6、onpropertiesofglassypolymers[12].Forinstance,therateatwhichapolymeriscooledfromabovetheglasstransitiontemperature,Tg,Allnon-equilibriumglasses,includingglassypolymers,undergohasprofoundeffectsonthematerial’sphysicalproperties[13].physicalaging,aprocessthatcausespropertychan
7、gesastheThesedifferencesarisefromthegreaterdisplacementfromequi-materialspontaneouslyrelaxestowardanequilibriumstate,andlibriuminsamplesrapidlyquenchedfromaboveTgascomparedtotheinfluenceofthesechangescanbeprofound.Physicalaginghasslowlycooledsamples.Asanexample,Cangialosieta
8、l.showedbeenstudiedextensivelyforbulkmaterialstoaidinunderstandinghigherinitialfre
