The pattern of change in the cohesive strength of the adhesive layer of Teflon high-temperature tape after high-temperature aging.

I.PatternofChangeinAdhesiveLayerCohesionUnderHigh-TemperatureAging

Post-curingrisingstage:Intheearlystageofhigh-temperatureexposure(e.g.,200–260°C),residualreactivegroupscontinuetocross-link,leadingtoasignificantincreaseincohesion.Theadhesivelayerbecomestougher,anditsresistancetoadhesivesqueeze-out(overflow)isenhanced.

Stableequilibriumstage:Cross-linkingapproachescompletion,andcohesionremainsstableoveralongperiod.Atthisstage,thetapeexhibitsoptimalperformanceandcanwithstandcontinuousoperationatitsdesigntemperature.

Degradationanddeclinestage:Underexcessivetimeortemperature,themainchainundergoesdegradation,causingcohesiontodecreasecontinuously.Theadhesivelayersoftensandbecomestacky,makingithighlysusceptibletocohesivefailureandsqueeze-out.

II.RootCausesofCohesiveFailureandAdhesiveSqueeze-Out

Rootcauseofcohesivefailure:Whenthecohesivestrengthoftheadhesivelayerislowerthantheinterfacialadhesionstrength,internaltearingoccurs,leavingadhesiveresidue.Thisstemsfrominsufficientcohesionorhigh-temperaturedegradation.

Rootcauseofsqueeze-out:Atelevatedtemperatures,themodulusdecreases,andtheadhesivelayerundergoescoldflow,beingextrudedfromtheedgesbythermalstress.Theunderlyingcausesareinsufficientcross-linkingdensityorexcessivemolecularchainmobility.

Relationshipbetweenthetwo:Long-termdegradationexacerbatesbothissuessimultaneously;insufficientcross-linkingdirectlyleadstosqueeze-outintheearlystage.

III.PreventionThroughAdhesiveFormulationandProcess

Formulationdesign:Usehigh-phenylsilicone,employaddition-curingsystemswithprecisecross-linkingcontrol,balanceMQresinratios,addreinforcingfillers,andeliminatelow-molecular-weightplasticizers.

Coatingandcuring:Implementthoroughpost-curingtreatmenttoremovelow-molecular-weightsubstancesandpreventsqueeze-outduringthefirstheatexposure.

Adhesivelayerstructure:Theadhesivethicknessshouldbekeptthin(≤25μm),anda0.5–1mmadhesive-freesafetymarginshouldbeprovidedattheedgestophysicallyblocksqueeze-out.

IV.PreventionThroughSubstrateandOperatingConditions

Substrateanchoring:PTFEfilmrequiresetchingorplasmatreatment,combinedwithaprimertomatchinterfacialandcohesivestrengths,preventingexcessiveanchoringthatcouldleadtocohesivefailure.

Temperaturecontrol:Strictlyfollowtheratedtemperaturespecificationsforuse,applygradualstepwiseheating,andavoidthermalshock.

Storageandhandling:Storeflatatlowtemperaturestopreventcoldflow,allowthetapetoreturntoroomtemperaturebeforeuse,andensurethebondingsurfaceiscleanandfreeofoil.

TheaboveinformationisprovidedbyJiangsuOKNewMaterialTechnologyCo.,Ltd.

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