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高分子材料与应用(英文版)Chapter7CoatingsandAdhesivesIntroductionWhatarecoatings?Anysubstancesusedtocoverasurfaceandformedanlayeronto.Morespecifically,coatingsmeanspolymerbasedmaterialsusedtocoverasurface.Fourbasicingredients:
film-formingvehicles,pigments,solvents,andadditives.IntroductionWhyCoatings?
Fordecoration:
Color,Gloss,etc.
Forsomefunctions:
erosionresistance,abrasionresistance,slipcontrol,fungalresistance,etc.ApplicationfieldArchitectureandfurniture(paint,漆);
Originalequipmentsmanufacture(OEM,usedinfactory);
SpecialCoatings(usedoutoffactory,forship,equipmentrepair,roadsignsetc.)IntroductionClassification
Basedonresintype:
alkyd,polyurethane,polyester,epoxy,…..Basedonenvironmentimpact:
Traditionalsolventcoatings:VOC→pollution
Environment-friendly:Waterborne,HighSolid,Powder,UV-curing…Basedonfinish(漆;末道漆)system:One-coat,Multicoatprimers,Intermediatecoats,andTopcoatsIntroduction
CoatingFormingProcess
1.Surfacecleaningandpretreatment2.Coatingsareapplied
dipping,spraying,electroplating…3.Theyformfilmsandcure
solventevaporation,bakingorairdrying,free-radicalpolymerization2.CoatingResins
AlkydsSynthesis:
fattyAcid+Polyacid+PolyolAdvantages:
lowcost;interiorexposuresgenerallygood.Disadvantages:
exteriordurabilityonlyfairApplication
finishingmetalandwoodproducts.PolyesterSynthesis:
Polyacid+Polyol+(Styrene)Advantages:
goodinterior&exteriordurabilityDisadvantages:
costishigherApplication:
furniture,appliances,automobiles,magnetwire2components:glass-reinforcedplasticbathtubs,lavatories,boats,carsCoatingResinsEpoxiesmedium-tohigh-priced,goodadhesion(primersforautomotive),heatresistance(electricalinsulation),excellenterosionandchemicalresistance.poorultraviolet-lightresistance:usedoutdoors,tendtochalkanddiscolor.Acrylicsoutstandingweatherresistance(architecturalcoatings);lacquersandenamels(thetopcoatsfortheautomotive);excellentexteriordurabilityCoatingResinsPolyurethanesprice>alkydsbut<epoxies.availableasoil-modified,moisturecuring,blocked,two-component,andlacquers.
abrasion-resistant,flexible,resilient,tough,chemical-resistant,andweather-resistant.
veryimportantfinishesinthetransportationindustry,includesaircraft,automobiles,railroads,trucks,andships;militarylandvehicles,ships,andaircraft(chemical&radiologicalresistance)CoatingResinsChlorinatedrubber
usedasswimmingpoolpaintsandtrafficpaints.Fluorocarbonsnonstickproperties(forcookware).Polyamidestough,wear-resistant,arelativelylowcoefficientoffriction(forofficefurniture)Polyolefinsmoistureproof(forchemical-processingandfood-handlingequipment)3.PigmentsDefinitioninsolubleparticlesdispersedintheliquidportionofthepaint.Functiongivedesiredcolorandgloss,plusprovide"hidingability"(proportionedtorefractiveIndex)andprotection.ClassificationOrganic,inorganic,metallic;White&Color.
PigmentsPigmentDispersionThreeStepsWetting;separatinglargemass;StabilizingthesmallparticlesStabilizingMechanismsForsolventcoating:Polymeradsorption(entropyexclusion):layer>4.5nmForwater-borncoating:needdispersants;ionicinteraction,hydrophobicandhydrophilicbalance.
PigmentsPigmentVolumeConcentration(PVC)CriticalPVC
WithPVC↑(upto>CPVC),thepolymerscannotfillthespacesbetweenpigmentparticles→Holesappears,strength↓,adhesion↓.FactorsthatcontrolCPVCparticlesize↓,CPVC↑;sizedistribution↑,CPVC↑4.AdditivesFunctionaffectvariousareassuchascolor,waterresistance,slipcontrol,foamcontrol,andgloss.Antioxidant
easilycleavage,formfreeradical;e.g.,Phenoliccompounds,naphthol,primaryandsecondaryaminesAdditives
AssociativethickenersFunction:thickenwater-based(mainlylatex)paintsthroughtheirhydrophobicinteractionwithotherpaintcomponentsThreeproducts:hydrophobicallymodifiedethoxylatedurethanes,HEUR,associativeacrylicthickeners,associativecelluloseetherAdditivesThickeningMechanism聚氨酯类增稠剂的增稠机理之一在于其分子可以水合溶胀而使水相增稠,其二是具有表面活性剂分子的性质,其分子是线性亲水链两端接有亲油基的高分子化合物,即在结构中具有亲水和疏水基团。这样,在它的水溶液浓度超过一定值时就形成胶束。胶束能够与乳液的聚合物粒子、已吸附有分散剂的颜料颗粒相互缔合形成空间网状结构,互相连结缠绕而使体系粘度增加。因而,聚氨酯类增稠剂也称为缔合型增稠剂。AdditivesOtheradditivesAcceleratorCuringagentsLightstabilizersDefoamerDispersingagent(dispersant)WettingagentsSurfactant5.Film-formingProcessSolventEvaporationwithsolventvolatilization,viscosity↑,Pigmentmovement↓,sotoplayerwithoutpigments→glossycoatingvolatilizetoofast→toplayerformfilmfirst→coatinglayershrinkageLatexcombinationDifficultytoformglossysurfaceFilmformingTtoolow→molecularmovement↓,latexparticlescannotcombine.Tg↑,Minimumfilmformationtemperature↑.CoatingFilmDefectsLeveling(流平)drivenforce:surfacetension(σ).peakarea:coatinglayer↑→solventvolatilization↓→σ>valleyarea→flowfrompeaktovalley.controlfactors:viscosity,layerthickness.Sagging(流挂)controlfactors:viscosity,layerthicknessSurfaceshrinkage(表面起皱)Surfacevolatilization(cure)>bulk→surfaceformfilmfirst→Surfaceshrinkage
Controlfactors:layerthickness,
volatilization(cure)speed.6.EnvironmentfriendlycoatingsUV-curablecoatingsLowVOC,minimumthicknesschangeBasiccomponentsofUVcurablecoatings
UV-curableCoatingsAdvantagesLowVOC,lowenergycost,lowequipmentinvestment.DisadvantagesThicknesslimit:pigment;polymerizationshrinkagePhotoinitiatorleftover:poorexteriordurability.Applications
printingsinks;papercoatings;photo-resistsforprintedcircuitsandmicroeletronicsWaterbornecoatingsWater-reduciblecoatingsWater+Solventasfilm-formingvehiclesCanusehighMwResinLownonvolatileweightWater-solublecoatingsWaterassolventLowwaterresistantLatexcoatings(乳胶漆)LowVOC,HighMw.DifficultytoformhighglossycoatingAdditivecomplication:dispersants,thickeners,etc.Usedinarchitecture.ElectrocoatingOrganiccoatingsaredepositedonproductsfromanelectrolyticbathResinsmustcontainingchargesAdvantagesanddisadvantagesUniformfilmthicknesses,lowVOC,lesslabor-intensive;highcapitalequipmentcosts,highermaterialcosts,andmorethoroughpretreatment.Application:BottomcoatingforCars;metalproducts.PowderCoatingsResintypeThermoplastic&ThermosettingFilmformationonpreheatedproductsCoatingMethodsFluidized-bedpowdercoating.Electrostaticfluidized-bedpowdercoatingElectrostatic-spraypowdercoatingAdvantages&disadvantagesLowVOC;thicknessupto500μm;lowenergycost.ExplosionRisk;cannotbeusedinthermosensitiveproducts.SummaryTraditionalcoatingshavefourbasicingredients.Environment-friendlycoatingshavebrightfuture.Coatingindustriesarereallytechnology-intensive.ADHESIVES粘接是用粘合剂将被粘物表面连接在一起的过程。2surfacescanonlybejoinedwiththeestablishmentofbondsbetweenthem.Theexactnatureofthebonddependsontheadhesiveandthesurfacetobebonded.Itisimportantwhenjoiningmaterialswithtrue
adhesivesthatthesurfacestobecompletely
clean.Evenathincoatingofgreaseorsimilarmaterial
mayreduceconsiderablytheeffectivesurface
tensionofthesurface,impairingthebond.INTRODUCTIONTYPESOFADHESIVECanbedividedinto3types:a)Naturaladhesives
-canbemadefromanimal,vegetableormineralsources
b)Syntheticresinbasedadhesives
i)Thermosettingadhesives
ii)Thermoplasticsyntheticadhesivesc)inorganicadhesivesCOMPONENTSOFADHESIVE(1)粘合物质(2)溶剂(3)增粘剂(4)消泡剂(5)增塑剂(6)填料(7)防腐剂(8)稀释剂NaturalAdhesivesANIMALGLUEShavebeenusedforcenturiesincarpentryandjoineryObtainedfromtheskin/bonesofcattleandsheepAnimalgluesusuallysoldinpowderandmeltedin
warmwatertogiveasolutionofsuitableviscosity.Coolingoftheliquidafterapplicationresultsinrapidgelling,producingsomestrengthanddryingfinallyproducesatoughandrigidproduct.Removalofthewaterfromglueduringcuringis
essential;thewoodassistinthisprocess,dueto
absorption.
Gluedjointsinwoodshouldbeasstrongas
thewood.Dampconditionwillreducestrengthofglue.Animalglueisnotsuitableforexternaluse
unlessadequatelyprotectedfrommoisture.Thegluewillhardengraduallyinthepotbut
canbesoftenedbyreheatingwithwater.Ifafailureoccursinsuchitemsitiseasyto
carryoutrepairsbysofteningthegluewith
water.AnimalGluesCASEINGLUESItisderivedasaprecipitatefromskimmed
milkbytheactionofacids.Gluesareobtainedinpowderformthatalso
containalkalinesolvent,necessarytodissolve
theglueonadditionofwater.Mixingiscarriedoutincoldandsettingis
partlybyevaporationorabsorptionofwater
andpartlybyanaturalgelationprocess.ItsadhesiontoporousmaterialisgoodItsmoistureresistanceissuperiorthananimal
glueCaseinGlue–ADryGlueDerivedFromMilkVEGETABLEGLUEMadefromstarches(淀粉)ordextrin(糊精)lowcostlimitedstrengthandlimitedmoisture
resistanceGumArabicisawatersolublevegetable
adhesiveoftenusedonstampsandgummed
paperenvelopes.CellulosePowderATypeofVegetableAdhesiveWheatPasteATypeofVegetableAdhesiveTHERMOSETTINGADHESIVESUREAFORMALDEHYDEOneofthecommonestadhesivesinjoineryforgeneralpurposes,producingastrongrigidjointiftheglue-lineisthin.Itprovidesastrongadhesioninapermanentlydryenvironment,curesfast,andisrelativelycheap.Tomaketheadhesive,formaldehydeandurea
inaqueoussolutionareallowedtoreacttogethertoacertainstageandthereactionisthenstoppedwhiletheresinisstillliquid.Theyarebestsuitedforjoiningporousmaterialsuchaswood.Itisusedforfabricationofflushcolours,laminatedtimberanddecorativelaminates.Ithasagoodwaterresistancebutifveryhot
waterorprolongedwettingitcouldbreaksthe
resindown.MELAMINEFORMALDEHYDERESINADHESIVES
Suppliedinpowderform&mixedwithwater
togiveacolourlessresin.Setonheatingto100°CGivegoodweatherresistance&expensive
thanureaformaldehydeadhesivePHENOLFORMALDEHYDEavailableasliquidsthatpolymeriseonheating
totemperatureover100°C.UsedforassemblyofplywoodsheetsTheresinisapplied,thesheetsformedandthe
laminatesisthensubjectedtoahotpressthat
causeshardeninginaperiodofabout5min.Cold-curingphenolicadhesivesarealso
available.CanbeappliedforPlywood,blockboards,
flushdoorsEPOXYRESINSItformagoodbondwithalmostanymaterial.Itiswidelyusedforstructuraljointsbetween
manytypesofmaterialincludingglass,metal,
thermosettingplasticsandconcrete.HaveexcellentmechanicalstrengthHaveexcellentcreepresistanceResistanttoweather,acids,alkalisandmost
hydrocarbon.EpoxyResinEpoxyResinAlkylCyanoacrylateAdhesivesHaveadvantageofpolymerisingveryrapidly
whenspreadinthinfilms.Thereactionbeingcatalysedbywaterintheverysmallquantitiesrequiredwhichispresent
onmostsurfaces.Expensivesousesareconfinedtobondingof
smallobjectshavingsurfacesthatclosely
conformtooneanother.TheyformthebasisofSuperglues.Mustbehandledwithcaretoavoidbondingof
skintissues.THERMOPLASTICADHESIVES
Settingactionofthesemayduetocooling,
solventevaporationoremulsioncoalescence.Thisadhesiveismoreflexiblebutweakerand
morepronetocreepthanthermosetting
adhesives.So,theyarenormallynotusedforstructural
purposes.POLYVINYLACETATEMostimportantthermoplasticadhesivein
building.Chiefapplicationbeingasawoodadhesivefor
internaluseandasabondingagentforconcrete.MostcommonlyusedinemulsionformThispolymerisobtainedfromacetylene&aceticacid.Theadhesivesetswhenthesolidparticles,on
evaporationorabsorptionofthemoisture,
coheretoformatough,clearfilmwhichisno
longerwatersoluble.PolyvinylAcetateUsedForBookBindingBITUMINOUS(沥青)ADHESIVES
Formgoo
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