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1、Nov21,2002ReactiveHotMeltAdhesives EdwardM.Petrie,MemberofSpecialChemTechnicalExpertTeam.IntroductionChemistryCuringandProcessingPropertiesEquipmentRequirementsApplicationsOtherReactiveHotMeltSystemsSummaryIntroductionAreactivehotmeltadhesiveisanythermoplasticadh
2、esiveorsealantthatcanbeappliedatelevatedtemperaturesasaliquidmelt,coolstobecomeasolidatroomtemperature,andthensubsequentlyreactstobecomeathermosettingpolymerwithenhancedphysicalproperties.Hotmeltadhesivescanbemadetobereactiveinseveralways.Reactivehotmeltadhesives
3、havebeenavailablesincethe1980s.Duetotheirthermoplasticnatureduringapplication,theyhavemanyofthedesirableprocessingcharacteristicsofconventionalhotmelts,suchasnosolventspresent,nomixingrequirements,andimmediategreenstrength.Althoughconventional,nonreactivehotmelta
4、dhesives(e.g.,ethylenevinylacetate,polyalphaolefin,polyester,andpolyamide)arewidelyusedinmanyindustrialapplications,theyhavecertainperformancelimitations,suchaspoorheatresistance,waterorsolventpermeation,andcreep.Theselimitationsgenerallypreventtheiruseinmanycrit
5、icalorstructuralbondingapplications.Bybeingcapableofcuringtoathermosettingmaterial,reactivehotmeltadhesiveseliminateorgreatlyreducemanyoftheperformanceproblemsassociatedwithconventionalhotmeltadhesives.Inaddition,reactivehotmeltadhesiveshavetheabilitytobondtomany
6、differentsubstratesand,generally,havelongerservicelifetimes.Theadvantagesofthesesystems,however,donotcomewithoutsomecost-generallyahighmaterialpriceandmoredifficultapplicationprocesses.Table1summarizestheadvantagesanddisadvantagesinusingreactivehotmeltadhesives.A
7、dvantagesDisadvantagesLowerapplicationtemperaturesthanconventionalhotmeltsallowforreducedenergycostsandlowersafetyconcerns.Highermaterialcost.LowornoVOCs.Fullcuretakesseveraldays.Nomixingrequired(singlecomponent).Opentimemaybeshort(seconds)dependingonthesubstrate
8、.Immediategreenstrengthandfastdevelopmentofcohesivestrength(crosslinking).Moisturesensitivitycouldcausematerialto"set"intheapplicatornecessitatingpurgingandcle
