外文翻译---20世纪到21世纪水性涂料面临的技术挑战 英文版.pdf

DOI:10.1126/science.1075707,976(2002)；297Scienceetal.RobertR.Matheson,Jr.,SoftCoatings20th-to21st-CenturyTechnologicalChallengesinThiscopyisforyourpersonal,non-commercialuseonly.clickingherecolleagues,clients,orcustomersby,youcanorderhigh-qualitycopiesforyourIfyouwishtodistributethisarticletoothers.herefollowingtheguidelinescanbeobtainedbyPermissiontorepublishorrepurposearticlesorportionsofarticles(thisinformationiscurrentasofMarch23,2010):Thefollowingresourcesrelatedtothisarticleareavailableonlineatwww.sciencemag.orghttp:/www.sciencemag.org/cgi/content/full/297/5583/976versionofthisarticleat:includinghigh-resolutionfigures,canbefoundintheonlineUpdatedinformationandservices,foundat:canberelatedtothisarticleAlistofselectedadditionalarticlesontheScienceWebsiteshttp:/www.sciencemag.org/cgi/content/full/297/5583/976#related-content7article(s)ontheISIWebofScience.citedbyThisarticlehasbeenhttp:/www.sciencemag.org/cgi/collection/mat_sciMaterialsScience:subjectcollectionsThisarticleappearsinthefollowingregisteredtrademarkofAAAS.isaScience2002bytheAmericanAssociationfortheAdvancementofScience；allrightsreserved.ThetitleCopyrightAmericanAssociationfortheAdvancementofScience,1200NewYorkAvenueNW,Washington,DC20005.(printISSN0036-8075；onlineISSN1095-9203)ispublishedweekly,exceptthelastweekinDecember,bytheScienceonMarch23,2010www.sciencemag.orgDownloadedfromwhereRisthereflectanceofthesample,H9270isthedistanceonthesurfacebetweentwopoints,H9275istheangularfrequency,kisthewavenumber,fisthefocallengthoftheincidentradiation,andH9268isthermsheightofthesurface.A2DanalysisoftheopticshasbeencarriedoutbyOgilvy(35).Whitehouseconcluded(34)(forundulationswithlengthscalegreaterthanthewavelengthoftheincidentradiation)thatthesurfaceappearedglossyiftheprobabilitydensityoftheslopesonthesurfacewasstrictlyconfinedtoanarrowangle.Biocompatibility.Finally,biologicalinterac-tionswithasurfacehavealsobeenfoundtodependonitstopography.AgoodreviewofthetopologicalcontrolofcelladhesionandactivityonasurfacehasbeenmadebyCurtisandWilkinson(36),andamoregeneralreviewoftheroleofpolymerbiomaterialsmayalsobefound(37).Suchconsiderationsarerelevantforanumberofinvivoandinvitroapplications,suchasbiologicalsensors,hipreplacements(38),andmorecomplextissueimplantssuchasreplacementbone,wherethegrowthofcellswithintheartificialstructureistobeencour-aged.Forexample,thesizeandmorphologyofcrystalsatthesurfaceofoctacalciumphos-phatecoatedcollagenhavebeenshowntoaf-fecttheinteractionofcellswiththesurface,asillustratedinFig.4.Thelargerscaletopographywasfoundtoleadtolessfavorablespheroidalcellsthatformedfewerintercellularconnections(39).Insomecases,thetopographyofasurfacemaybecarefullycontrolledtopromotecelladhesion(40,41).ConclusionThetopographyofasurfaceisadirectresultofthenatureofthematerialthatdefinesit.Theanalysisofthetopographyofasample,madepossibleonthenanoscalebythedevel-opmentofAFMtechniques,needstobecare-fullyconsideredinordertorelatethecom-plexityofa2Dsurfacetothematerialsproperties.Theresultwillbethebettercon-trolofanumberofproperties,suchasopticalfinish,andoftheinteractionofasurfacewithasecondarymaterial,whetherthatbeanad-hesive,asecondarycomponentofacompos-ite,orabiologicalspecies.ReferencesandNotes1.J.D.Afnitoetal.,ThinSolidFilms291,63(1996).2.J.A.DeAro,K.D.Weston,S.K.Buratto,U.Lemmer,Chem.Phys.Lett.277,532(1997).3.Y.Nabetani,M.Yamasaki,A.Miura,N.Tamai,ThinSolidFilms393,329(2001).4.M.Sferrazzaetal.,Phys.Rev.Lett.78,3693(1997).5.E.Scha¨ffer,T.Thurn-Albrecht,T.P.Russell,U.Steiner,Europhys.Lett.53,218(2001).6.D.G.Bucknall,G.A.D.Briggs,MRSSymp.Ser.:Nanopatterning:Ultralarge-ScaleIntegrationBio-technol.705,151(2002),L.Merhari,K.E.Gonsalves,E.A.Dobisz,M.Angelopulss,D.Herr,Eds.7.S.Walheim,E.Scha¨ffer,J.Mlynek,U.Steiner,Science283,520(1999).8.J.Heier,E.Sivaniah,E.J.Kramer,Macromolecules32,9007(1999).9.T.Thurn-Albrecht,J.DeRouchey,T.P.Russell,Mac-romolecules33,3250(2000).10.A.Karimetal.,Macromolecules31,857(1998).11.X.P.Jiang,H.P.Zheng,S.Gourdin,P.T.Hammond,Langmuir18,2607(2002).12.G.Goldbeck-Woodetal.,Macromolecules35,5283(2002).13.V.N.Bliznyuk,K.Kirov,H.E.Assender,G.A.D.Briggs,Polym.Preprints41,1489(2000).14.F.Dinelli,H.E.Assender,K.Kirov,O.V.Kolosov,Polymer41,4285(2000).15.C.Rauwendaal,PolymerExtrusion(Hanser,Munich,1985).16.S.-J.Liu,Plast.RubberComposites30,170(2001).17.B.Monasseetal.,Plast.ElastomeresMag.53,29(2001).18.Y.Oyanagi,Int.Polym.Sci.Technol.24,T38(1997).19.A.Guinier,X-rayDiffractioninCrystals,ImperfectCrystals,andAmorphousBodies(W.H.Freeman,SanFrancisco,1963).20.V.N.Bliznyuk,V.M.Burlakov,H.E.Assender,G.A.D.Briggs,Y.Tsukahara,Macromol.Symp.167,89(2001).21.W.M.Tong,R.S.Williams,Annu.Rev.Phys.Chem.45,401(1994).22.P.Meakin,Fractals,ScalingandGrowthFarfromEquilibrium(CambridgeUniv.Press,Cambridge,1998).23.C.M.Chan,T.M.Ko,H.Hiraoka,Surf.Sci.Rep.24,3(1996).24.E.M.Liston,L.Martinu,M.R.Wertheimer,J.AdhesionSci.Technol.7,1091(1993).25.Q.C.Sun,D.D.Zhang,L.C.Wadsworth,TappiJ.81,177(1998).26.V.Bliznyuketal.,Macromolecules32,361(1999).27.N.Zettsu,T.Ubukata,T.Seki,K.Ichim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ionispossible,thenitwillsoftenanddeformonceagain.More-over,becausemostcoatingfilmsareeitheramorphousorsemicrystalline,theirabilitytoretainaminimumhardnessandtoresistsustainedloadsbeginstofalloffquiteno-ticeablyattemperatureswellbelowthosewhererapidflowandlevelingareachieved(3).Acceptablesolventsubstitutionbasicallyamountstousingtheliquidformofsubstanc-esthatarenaturallypresentasgasesintheatmosphere(suchaswaterandcarbondiox-ide).Liquidorsupercriticalcarbondioxideislimitedtoindustrialapplicationsbecauseoftherequirementsforhighpressure.Wateriseasiertousewidelyasacoatingsolvent,butitisnotapanacea.Oneexampleofaproblemthatcomeswithwateristheinevitablywidevariationindryingtimesthataccompaniesapplicationinenvironmentsofdifferentrel-ativehumidity.Becauserelativehumiditycanchangealmosthourly,thisisaseriouscomplication.Infact,virtuallyallwaterbornecoatingstodaycontainquitesubstantiallevelsoforganic“cosolvents.”TheVOCcontentofwaterbornecoatingsisgreatlyreducedascomparedtothatofolder,conventionalsolvent-bornecoatings,butitisnotfullyeliminated.Amajoractivityinmoderncoat-ingdevelopmentisthesearchforbalancedchemistrythatwillpushbacktheselimitsonenvironmentallymorefavorablelacquerswhileretainingtheattractivesimplicity,thesyntheticcontrol,andthelowcostofthetechnology.VOCreleaseisnottheonlyenvironmen-talimpactfactorthatisimportantfordrivingchangeincoatingtechnology.IntheUnitedStates,regulationsonso-calledhazardousairpollutants(HAPs)areimportant(4).Thisisanexplicitlistofsolvents,typicallyaromatic,thatareusedinlargequantitiesandareeitherknowntocauseorsuspectedofcausinghu-manhealthproblemswithchronicexposure.Avarietyofother,similarlylocalconstraintsforparticularingredientsexistaroundtheglobe.Oneverywidelyexperiencedrestric-tionisthatonheavymetals.Therearemanyhistoricalexampleswherefairlylargeamountsofparticularmetalshavefounduseinsoftcoatings(5).Someexamplesaretheuseofleadforanticorrosionincathodicelec-trocoatcoatings,ofhexavalentchromiuminmetalcoatings,ofbothleadandcadmiuminvariouspigments,ofdivalenttininantifoul-ingmarinecoatings,andevenofmercuryasanantifungalagentforsomeinteriorpaints.Incommonwithotherareasofmaterialsprocessing,coatingtechnologynowhastolookforalternativeingredientswithoutun-controllable,long-termenvironmentalconse-quences.Nosimilarlygeneraltechnicalsolu-tionshaveyetbeenfound,althoughprogressisbeingmade,particularlywithrespecttoanticorrosioncoatings.BeatingBacktheEnvironmentChemicalandmechanicalresistancetoenvi-ronmentalinsultisacommonfeatureofmanycoatingsystemsandakeyreasonfortheirapplication.Biologicalattacksareclas-sicproblemsencounteredovertheyears,andtheircatalogdefinesthecurrentfrontier.Un-derwatercoatingsthatcanresisttheattach-mentanddegradationofaqueousorganisms(suchaswormsandbarnacles)areneededforshippingandforstructures.Exteriorcoatingsthatcanresistparticularinsect,bird,andplantexcretionsarefrequentlyneededinlo-calgeographies.Interiorcoatingsthatcanresistmildew,otherfungaldamage,molds,andbacteriaarefrequentlydesired.Thegen-eralchallengeisnearlyalwaysthesame:specificresistancetoadefinedclassofbio-logicalinsultwithoutnonspecifictoxicityorirritation.Itisnaturaltoworktowardthissetofobjectiveswithadditivestailoredtoeachtask.Experienceshowsthisnaturalpathtobeexpensiveandusuallyimperfect,butocca-sionallyfruitful.Still,itisprobablyfairtosaythatnoexamplesexistwheretheperformanceofthebroadlytoxic,heavymetalbasedad-ditiveshasbeenachievedwiththemorespe-cificmoderntools.AnewideaistoproducecounteragentsinsitubytappingthechemicalreactionsthatmustaccompanybiologicalattackorevensimpleweatheringintheactiveenvironmentsnearEarthssurface(6).Forexample,bio-logicaldamagemaybeaccompaniedbyhy-drolyticscissionofcoatingcomponents.Ifthosecanbedesignedtohydrolyzeintoanti-septic,antifouling,oranti-whateverproductstailoredtothetask,thenperhapsaneffectivesolutioncanbefound.MaximizingControlThroughMolecularArchitecturesItisimportanttolookbeyondenvironmentalattackonthecoatingitself.Theclassicalroleofcoatingsistoprotectsomethingelsefromtheenvironment.Thisprotectioncanbeme-chanicalorchemicalinnature.Varnisheshavebeendevelopedparticularlyforthesepurposes,becauseinsituor“onthework”cross-linkingisaveryeffectivetechniqueforaugmentingthecoatingsmaterialpropertieswhileavoidingcompromisesinapplication.Anextremelyactiveareaofdevelopmentinmoderncoatingsisdirectedtoimprovingthecontrolofsuchreactions.Inevitably,thesemustbecarriedoutinavarietyofworkenviron-ments.Nearoneextremearecoatingsusedincontrolledchambers,asfortheradiationorthermalcuringofacoatingusedtosealaconnectionbetweenelectroniccomponents.Thevariablesofconcernmaybefilmthicknessatvariouspoints,surfacecleanliness,andsmalltemperaturegradientsarisingfrommaterialsofdifferentthermalconductivity.Neartheotherextremearethegrosslyfluctuatingenviron-mentsthatcanbefoundinarailroadlocomo-tiveshed,wherehumidity,temperature,airflow,applicationrate,surfacepreparation,andmaybeevensurfacematerialareallvariables.Oneideaformeetingthesechallengesiswww.sciencemag.orgSCIENCEVOL2979AUGUST2002977MATERIALSSCIENCE:SOFTSURFACESonMarch23,2010www.sciencemag.orgDownloadedfromtotakegreatcareinsynthesizingthevar-nishingredientssothatnoespeciallytrou-blesomereactionscaneveroccur.Somesidereactionsareunderstandablymoredel-eteriousthanothers,andthegoalistoleavenoopportunityforthemosttroublesome,nomatterwhatconditionsmightappear.Thisleadstotheuseofcontrolledpolymer-izationtechniquesexemplifiedbutcertain-lynotlimitedtogrouptransferpolymeriza-tion(7)foracrylicmaterials,rigorousexclusionofnonfunctional(unabletopar-ticipateincuring)matrixmaterials,andoptimizingmolarmassdistributionstoavoiduntimelyimmiscibilityduringcureandsimilarstrategies.Thespecificfieldofautomotivecoatinghasbeeninthefore-frontofthisactivitybecauseoftheex-tremelyhighperformancestandardsandpowerfuleconomicincentivesfoundinmass-producingautomobiles.Someofthenewsyntheticandanalyticaltechniquesbe-ingintroducedforcontrollingandmonitor-ingautomotiveenamelshavebeende-scribed(8).Decorativecoatingsinparticularneedtoincorporatepigments,dyes,reflectivemetal,andmicaflakesformanyapplications.Onecommontechniqueforeffectivelydistribut-ingsuchparticlesistocovertheirsurfaceswithdispersantsthataidintheirdispersioninthebulkofthecoatingandpreventreagglom-erationunderthevarietyofcircumstancesthatmightariselater.Exquisitecontrolofthemolecularstructureisneededinordertoachievegooddistributionoftheparticles,minimalmobilityonceappliedtoasurface,theabilitytoresistforcesthatdrivere-agglomeration,andcompatibilitywiththebulkcoatingandyetnotinduceproblemswithadhesion,application,orlong-termper-formance.Becausepigmentsareveryfre-quentlythemostexpensiveingredientsinadecorativecoating,itisimportanttousethemefficiently.Additionally,assolventconcen-trationandvarietyaredecreasedbecauseoftheenvironmentalpressurespreviouslycited,opportunitiesformanagingdispersionprob-lemsbymodifyingthecoatingmedium(thecoatingvehicle)decrease.Smallwonderthatthechemistryusedtomakemoderndispers-antsprovidesanexceptionallyclearpictureofthestateoftheartinmolecularcontrolincoatings.Techniquesformakingblockco-polymers(eachblockdesignedforaffinitytoeitherasurfaceorthesolventenvironment)havebeendevelopedandcommercializedandarestillbeingimproved.Thepatentartisextensiveandgrowing,butthatfromC.Ho-sotte-Filbert(9)isarepresentativeexample.FunctionalCoatingsAfourthmodernfrontierintheworldofsoftcoatingscanbedescriptivelycalled“postcurereactivity”forvarnishes,orperhaps“in-usereactivity”forlacquers.Suchreactionshavebeenrecognizedforalongtimeinexamplessuchasthelong-termoxidationofalkydvar-nishesandmanylacquersbasedonnaturalproducts.Historically,thesehavebeenviewedastroublesomeinstabilities.Howev-er,ithasbeenlearnedthatsomeinstancesofpostcurechemistryhaveadvantages,withoneexamplebeingtheslowcondensationandinterchangeofsiloxanebondsinorganosilaneenamels(10).Thesecanacttorelaxstressesthatotherwisegrowuncompensatedinlight-andoxidation-stressedexteriorcoatings.Het-erogeneouscoatingsthatreacttocracksorfracturesbyreleasingpostcurerepairingre-dientshavebeenpostulated(11).Evenmoresophisticatedusesincon-trolledreleaseorothertransportcontrolprob-lemscanbesketchedtoday.Itshouldbenotedthatagreatmanyinstancesexistinwhichcoatingsareusedtomanipulate(gen-erallytoretard,delay,orprevent)thetrans-portandexchangeofmaterials.Atmosphericoxygencontactingfood,carbondioxideexit-ingcarbonatedbeverages,thereleaseofpharmaceuticalsintothebody,electricalchargeleakingintoadevicecomponent,heatexitinganisothermalenvironment,orwaterandionicmaterialscontactingcorro-sion-susceptiblemetalsareexampleswherethetransportcharacteristicsofcoatingsareimportantindeterminingperformance.Thelong-termcapabilityofacoatingtoim-proveorattheleastreacttocompensateforadecliningtransportcharacteristicmaybejustasusefulasthesameabilitytooffsetdecliningmechanicalcharacteristics.IndustrialScaleChallengesAfinalclassofproblemsdrivinginnovationinmoderncoatingscanbefoundinthecostsandlimitationsoftheheatingstepinenamelprocessing.Notsurprisingly,theseproblemsincludethecapitalandenergycostsassociat-edwithheatingobjectswithlargethermalmasses,damagetoheat-sensitivesubstrates,andtheinventoryproblemsthataccumulatewithlongcycletimesinanyprocess.Themostdirectapproachistoreducetherequiredbakingtemperatureand/ortime.Thereisscopeherefornovelchemicalreactionsandcatalystinnovations,bothofwhichcommandattentiontoday.Alternatively,ifthecuringreactionscanbeactivatedbyamechanismotherthansimpleheating,thenproblemscanbeminimizedwithoutlosingthecure-in-ducedimprovementsincoatingperformance.Muchcurrentworkisdirectedtoradiation-curable(withultravioletlight,electronbeams,andevenvisiblelight)coatingsandeffortstoextendtheircurrentembodimentstocomplexarticlesandlong-termuse(12).Powdercoatingsandliquidcoatingsarebothobjectsofstudyandinnovation.Themajorchallengefacedinsuchdevelopmentarisesfromlimitationsontheuniformityofcureforincompletelytransparentcoatings(shadowedareasdonotreceivethesamefluxofradia-tion)orcoatingsoncomplexshapes.Examplesofspecificnewproductsarisinginresponsetooneoranotherofthesefivegeneraldevelopmentareascanbefoundinmanyplacesandfrommanydevelopmentlab-oratories.Perhapsnoexampleexiststhatillus-tratesall,butthereisatleastonethatcomesclose.Aneedexistsintheautomotiveworldforapaintingsystemwithlowerenvironmentalemissions(particularlyVOCs),improvedresis-tancetoenvironmentaldamage(particularlymechanicalscratching),outdoordurabilityap-proachingadecade,corrosionresistanceofthecoatedmetalforthesameperiodoftime,andimprovedapplicationrobustness.Thisneedhasbeenrecentlymetwithwhatmightbeconsid-eredanexemplarymoderncoatingsystem.Fourlayersofcoatingareused:First,ananti-corrosioncoating(nowfreeofheavymetals)isappliedbycathodicelectrodeposition；second,apowderprimer(nowwithzeroVOCs)；third,awaterbornelayercontainingpigments(nowwithminimalVOCsandminimalHAPswithmodernpolymericdispersantmolecules)；andfinally,anewclearcoat(nowwithmorethan20%lowerVOCs,greatlyimprovedscratchresistance,andexcellentresistancetoacidrain,chemicalattack,andphotochemicalexposure).Allthisisappliedwiththeuseofexistinginfrastructure,includingbothautomaticandmanualequipmentwhenrequired,atcommer-cialratesandwithlowertotalenergyinputandimprovedvisualquality.Theautomotiveuseenvironmentisharshforcoatings,andthisnewsystemhasonlybeguntobeused.Itisriskytoforetelldecade-longsuccesssofarinadvance,butthestepappearstobeanimportantoneintheevolutionofsoftcoatingsthatcanresistallthemajorpressures.LookingForwardThefivegeneraldevelopmentfrontiersap-peartoindicatetwostrongtrendsintodayssoftcoatingdevelopment.Thefirstisatrendtowardever-improvingcontrolofstructureatalllengthscales.Whetherincure-sitedistri-butionsformorerobustvarnishes,molarmassdistributionsinenvironmentallyfriend-lylacquers,oropticalpathdistributionsforultravioletcurables,thepathofimprovementandinnovationgoesalongthelineofim-provedstructuraluniformityandcontrol.Thesecondtrendisthehistoricallyfamiliaronetowardblurringthedistinctionsbetweenandtherebyremovingsomelimitationsfromfamiliarcoatingclasses.Whetherbyslowin-usereactionsfornominallacquersandam-bientvarnishesorbyradiation-assistedcross-linkinginnominalenamels,thetechnologytrendistowardtheboundarieslaiddownbythedescriptors.Onecanphrasethesetrendsintheformoftwostrategicquestionsfor9AUGUST2002VOL297SCIENCEwww.sciencemag.org978MATERIALSSCIENCE:SOFTSURFACESonMarch23,2010www.sciencemag.orgDownloadedfrom