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1、PVDFMembraneFormationbyDiffusion-InducedPhaseSeparation-MorphologyPredictionBasedonPhaseBehaviorandMassTransferModeling11222LIAO-PINGCHENG,DAR-JONGLIN,CHIEN-HSIEHSHIH,AN-HWADWAN,CARLC.GRYTE1DepartmentofChemicalEngineering,TamkangUniversity,TaipeiHsien,Taiwan,Republico
2、fChina251372DepartmentofChemicalEngineeringandAppliedChemistry,ColumbiaUniversity,NewYork,NewYork10027Received26October1998;revised8February1999;accepted10February1999ABSTRACT:Theequilibriumphasebehaviorofwater(nonsolvent)-DMF(solvent)-PVDFsystemat25°Cwasinvestigatedv
3、iaboththeoreticalandexperimentalap-proaches.Usingbinaryinteractionparameters,xij,obtainedpreviously,thetheoreticalphaseboundarieswerecomputedandwerefoundtomatchcloselythemeasuredbinodalandcrystallization-inducedgelationdata.Membraneswerepreparedusingtheisothermalimmer
4、sion-precipitationprocessesinvariousdopeandbathconditions.Theformedmembranesdemonstratedabroadspectrumofmorphologies:Atoneextreme,asymmetricstructurewasobtainedfeaturingacontinuoustightskinandasublayercomposedofparallelmacrovoidsandcellularpores;attheotherlimit,skinle
5、ssmicro-porousmembranewasproducedwithsphericalparticlespackedintoabi-continuousstructure.ThecrystallinecharactersofPVDFgelsandmembraneswereexaminedbysmallanglelightscattering,scanningelectronmicroscopy,anddifferentialscanningcalorimetrytechniques.Inaddition,diffusiont
6、rajectoriesandconcentrationpro®lesinthemembranesolutionbeforeprecipitationwerecalculatedfortheimmersionprocess.Theseresultspredictedreasonablythevariousmorphologiesobservedinthemembranes.©1999JohnWiley&Sons,Inc.JPolymSciB:PolymPhys37:2079±2092,1999Keywords:poly(vinyli
7、dene¯uoride);membrane;phasediagram;immersionprecip-itation;diffusionINTRODUCTIONcourseofphasedemixing,thepolymer-richphasedensi®esintoasolidmatrix,whilethepolymer-Mostcommercialmicroporousmembranessuit-poorphasedevelopsintothepores.Thereareableforbacteria®ltrationproc
8、essesaremanufac-severalphaseinversionmethodscommonlyem-1±3turedbytheªphaseinversionºmethod.Phaseployedinmembranesynthesis,su
