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1、570COATINGMETHODS,POWDERTECHNOLOGYVol.5COATINGMETHODS,POWDERTECHNOLOGYIntroductionPowdercoatingisaprocessforapplyingcoatingsonasubstrateusingheatfusiblepowders.Materialsusedintheprocessarereferredtoascoatingpowders,finelydividedparticlesoforganicpolymer,eitherthermoplasticorthermosetting,whichus
2、uallycontainpigments,fillers,andotheradditives.Afterapplicationtothesubstrate,theindividualpowderparticlesaremeltedinanovenandcoalescetoformacontinuousfilmhavingdecorativeandprotectivepropertiesassociatedwithconventionalorganiccoatings.Theoriginofpowdercoatingtechnologydatesbacktothelate1940swhen
3、powderedthermoplasticresinswereappliedascoatingstometalandothersub-stratesbyflamespraying.Inthisprocess,apowderedplasticwasfedthroughaflamesprayingapparatuswheretheplasticparticlesaremeltedandpropelledbythehotgasestothesubstrate.ApatentissuedinGreatBritaintoSchoriMet-allisingProcess,Ltd.,in1950de
4、scribedaprocessforformingacoatinginwhichpowderedthermoplasticswereappliedtoaheatedsubstratebydippingorrollingtheheatedarticleintheplasticpowder(1).Thisprocesswasdifficulttopractice,however,andneverachievedcommercialsuccess.Amajorbreakthroughinpowdercoatingoccurredinthemid-1950s,whenErwinGemmerco
5、nceivedthefluidized-bedcoatingprocess,inwhichaheatedobjectisdippedintoafluidizedbedofpowder.GemmerwasinvolvedindevelopingflamesprayingprocessesandmaterialsinthelaboratoriesofKnapsack-Griesheim(Hoechst),amanufacturerofspecialtygases,andwassearchingforamoreefficientmethodthanflamesprayingforcoatingobj
6、ectswithpowder.ThefirstpatentapplicationswerefiledinGermanyinMay1953,andthebasicpatentwasissuedEncyclopediaofPolymerScienceandTechnology.CopyrightJohnWiley&Sons,Inc.Allrightsreserved.Vol.5COATINGMETHODS,POWDERTECHNOLOGY571inSeptember1955(2).ThefirstUnitedStatespatentwasissuedin1958(3),andthePolyme
7、rCorp.,Reading,Pa,acquiredrightstotheKnapsack-Griesheimpatents.ThePolymerCorp.mountedanaggressiveefforttodevelop,license,andsellfluidized-bedcoatingtechnologyinNorthAmerica.However,acceptanceofthiscoatingprocesswasratherslow.In1960