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PET连续固相缩聚工艺及主要影响因素.docx

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PET连续固相缩聚工艺及主要影响因素 Introduction Polyethyleneterephthalate(PET)isawidelyusedthermoplasticpolymerinthepackagingindustryduetoitsexcellentphysicalproperties,suchashighstrength,stiffness,andtransparency,aswellasgoodgasbarrierandthermalresistance.Theprocessofcontinuoussolid-statepolycondensation(CSSP)isusedtoimprovethepropertiesofPET,whichinvolvesthemeltingandsubsequentcoolingofPETflakesorchipsunderavacuumatmospheretoremovevolatilesandcreateamorecrystallinepolymer.ThispaperaimstoreviewthePETCSSPprocessanditsmaininfluencingfactors,includingtemperature,residencetime,vacuumpressure,andfeedrate. Processdescription ThemainobjectivesoftheCSSPprocessaretoincreasethedegreeofpolymerizationandimprovethethermalpropertiesofPETflakesorchips.TheprocessinvolvesheatingthePETmaterialtoatemperatureofaround225-260°Ctomeltit,followedbyloweringthetemperaturetoabout190-215°Ctoinitiatethepolymerizationreaction.Thematerialisthencooledtoroomtemperature,andtheprocessisrepeateduntilthedesiredpropertiesareachieved.Theprocessistypicallycarriedoutunderavacuumatmospheretoremovevolatilesgeneratedduringthereactionandpromotepolymerization. Influencingfactors Temperature:TemperatureisthemostimportantfactoraffectingtheCSSPprocess.Thetemperatureofthepolymermustbehighenoughtoinitiatethereactionbutlowenoughtopreventthermaldegradation.Highertemperaturesincreasetherateofpolymerizationbutalsoincreasetherateofdegradation.Therefore,carefulcontroloftemperatureisessentialtoensurethatthereactionproceedsoptimallywithoutanysignificantdegradation. Residencetime:ResidencetimeisanothercriticalparameterintheCSSPprocess,asitdeterminesthedegreeofpolymerizationandthemolecularweightofthefinalproduct.Longerresidencetimesleadtohighermolecularweightandimprovedthermalproperties.However,excessiveresidencetimescanleadtodegradation,andlowermolecularweight.Therefore,itisessentialtooptimizetheresidencetimetoachievethedesiredmolecularweightandthermalproperties. Vacuumpressure:ThevacuumpressureappliedduringCSSPiscriticaltotheremovalofvola