高分子材料与应用(英文版)-Chapter-7-Coatings-and-Adhesives课件.ppt
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- 高分子材料 应用 英文 Chapter Coatings and Adhesives 课件
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1、高分子材料与应用(英文版)Chapter 7 Coatings and AdhesivesIntroductionIntroductionWhat are coatings?What are coatings?Any substances used to cover a surface and formed an layer onto.More specifically,coatings means polymer based materials used to cover a surface.Four basic ingredients:film-forming vehicles,pigme
2、nts,solvents,and additives.IntroductionIntroductionWhy Coatings?Why Coatings?For decoration:For decoration:Color,Gloss,etc.For some functions:For some functions:erosion resistance,abrasion resistance,slip control,fungal resistance,etc.Application fieldApplication field Architecture and furniture Arc
3、hitecture and furniture(paint,漆);Original equipments manufactureOriginal equipments manufacture(OEM,used in factory);Special CoatingsSpecial Coatings(used out of factory,for ship,equipment repair,road signs etc.)IntroductionIntroductionClassificationClassification Based on resin type:alkyd,polyureth
4、ane,polyester,epoxy,.Based on environment impact:Traditional solvent coatingsTraditional solvent coatings:VOCpollution Environment-friendly:Environment-friendly:Waterborne,High Solid,Powder,UV-curingBased on finish(漆;末道漆)system:One-coat,Multicoat primers,Intermediate coats,and Top coatsIntroductionI
5、ntroduction Coating Forming ProcessCoating Forming Process 1.Surface cleaning and pretreatment 2.Coatings are applied dipping,spraying,electroplating 3.They form films and cure solvent evaporation,baking or air drying,free-radical polymerization2.Coating Resins2.Coating Resins AlkydsAlkydsSynthesis:
6、Synthesis:fatty Acid+Polyacid+PolyolAdvantages:Advantages:low cost;interior exposures generally good.Disadvantages:Disadvantages:exterior durability only fairApplicationApplication finishing metal and wood products.PolyesterPolyesterSynthesis:Synthesis:Polyacid+Polyol+(Styrene)Advantages:Advantages:
7、good interior&exterior durabilityDisadvantages:Disadvantages:cost is higher Application:Application:furniture,appliances,automobiles,magnet wire 2 components:glass-reinforced plastic bathtubs,lavatories,boats,carsCoating ResinsCoating ResinsEpoxiesEpoxies medium-to high-priced,good adhesion(primers
8、for automotive),heat resistance(electrical insulation),excellent erosion and chemical resistance.poor ultraviolet-light resistance:used outdoors,tend to chalk and discolor.AcrylicsAcrylics outstanding weather resistance(architectural coatings);lacquers and enamels(the top coats for the automotive);e
9、xcellent exterior durabilityCoating ResinsCoating ResinsPolyurethanesPolyurethanesprice alkyds but 4.5 nm For water-born coating:need dispersants;ionic interaction,hydrophobic and hydrophilic balance.PigmentsPigmentsPigment Volume Concentration(PVC)Pigment Volume Concentration(PVC)Critical PVCCritic
10、al PVC With PVC(up to CPVC),the polymers cannot fill the spaces between pigment particles Holes appears,strength,adhesion.Factors that control CPVCFactors that control CPVC particle size,CPVC;size distribution,CPVC 4.Additives4.AdditivesFunctionFunction affect various areas such as color,water resis
11、tance,slip control,foam control,and gloss.AntioxidantAntioxidant easily cleavage,form free radical;e.g.,Phenolic compounds,naphthol,primary and secondary aminesAdditivesAdditives Associative thickenersAssociative thickenersFunction:thicken water-based(mainly latex)paints through their hydrophobic in
12、teraction with other paint componentsThree products:hydrophobically modified ethoxylated urethanes,HEUR,associative acrylic thickeners,associative cellulose etherAdditivesThickening MechanismCH2CH2OOnRNHCOOCNHR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,
13、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。AdditivesAdditivesOther additivesOther additivesAcceleratorAcceleratorCuring agentsCuring agentsLight stabilizersLight stabilizersDefoamerDefoamerDispersing agent(dispersant)Dispersing agent(dispersant)Wett
14、ing agentsWetting agentsSurfactantSurfactant5.Film-forming Process5.Film-forming ProcessSolvent EvaporationSolvent Evaporationwith solvent volatilization,viscosity,Pigment movement,so top layer without pigments glossy coatingvolatilize too fast top layer form film first coating layer shrinkageLatex
15、combinationLatex combinationDifficulty to form glossy surfaceFilm forming T too low molecular movement,latex particles cannot combine.Tg,Minimum film formation temperature.Coating Film DefectsCoating Film DefectsLeveling(Leveling(流平流平)driven force:surface tension().peak area:coating layer solvent vo
16、latilization valley area flow from peak to valley.control factors:viscosity,layer thickness.Sagging(Sagging(流挂流挂)control factors:viscosity,layer thicknessSurface shrinkage(Surface shrinkage(表面起皱表面起皱)Surface volatilization(cure)bulk surface form film first Surface shrinkage Control factors:layer thic
17、kness,volatilization(cure)speed.6.Environment friendly coatingsUV-curable coatingsLow VOC,minimum thickness changeBasic components of UV curable coatingsBasic components of UV curable coatings UV-curable CoatingsUV-curable CoatingsAdvantagesAdvantages Low VOC,low energy cost,low equipment investment
18、.DisadvantagesDisadvantages Thickness limit:pigment;polymerization shrinkage Photoinitiator leftover:poor exterior durability.ApplicationsApplications printings inks;paper coatings;photo-resists for printed circuits and microeletronicsWaterborne coatingsWaterborne coatingsWater-reducible coatingsWat
19、er-reducible coatingsWater+Solvent as film-forming vehiclesCan use high Mw ResinLow nonvolatile weight Water-soluble coatingsWater-soluble coatings Water as solvent Low water resistantLatex coatingsLatex coatings(乳胶漆)Low VOC,High Mw.Difficulty to form high glossy coatingAdditive complication:dispers
20、ants,thickeners,etc.Used in architecture.ElectrocoatingElectrocoatingOrganic coatings are deposited on products from an electrolytic bathResins must containing chargeslAdvantages and disadvantages Uniform film thicknesses,low VOC,less labor-intensive;high capital equipment costs,higher material cost
21、s,and more thorough pretreatment.lApplication:Bottom coating for Cars;metal products.2 H2O4 H+O2+4 e-Polymer-COO-+H+Polymer-COOH Powder CoatingsPowder CoatingsResin typeResin type Thermoplastic&ThermosettingFilm formation on preheated productsFilm formation on preheated productsCoating MethodsCoatin
22、g MethodsFluidized-bed powder coating.Electrostatic fluidized-bed powder coatingElectrostatic-spray powder coatingAdvantages&disadvantagesAdvantages&disadvantagesLow VOC;thickness up to 500 m;low energy cost.Explosion Risk;cannot be used in thermosensitive products.SummarySummaryTraditional coatings
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