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
23、 have four basic ingredients.Environment-friendly coatings have bright future.Coating industries are really technology-intensive.ADHESIVES 粘接是用粘合剂将被粘物表面连接在一起的过程。2 surfaces can only be joined with the establishment of bonds between them.The exact nature of the bond depends on the adhesive and the sur
24、face to be bonded.It is important when joining materials with true adhesives that the surfaces to be completely clean.Even a thin coating of grease or similar material may reduce considerably the effective surface tension of the surface,impairing the bond.INTRODUCTIONTYPES OF ADHESIVECan be divided
25、into 3 types:a)Natural adhesives -can be made from animal,vegetable or mineral sources b)Synthetic resin based adhesives i)Thermosetting adhesives ii)Thermoplastic synthetic adhesives c)inorganic adhesivesCOMPONENTS OF ADHESIVE(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 Natural AdhesivesANIMAL G
26、LUES have been used for centuries in carpentry and joinery Obtained from the skin/bones of cattle and sheep Animal glues usually sold in powder and melted in warm water to give a solution of suitable viscosity.Cooling of the liquid after application results in rapid gelling,producing some strength a
27、nd drying finally produces a tough and rigid product.Removal of the water from glue during curing is essential;the wood assist in this process,due to absorption.Glued joints in wood should be as strong as the wood.Damp condition will reduce strength of glue.Animal glue is not suitable for external u
28、se unless adequately protected from moisture.The glue will harden gradually in the pot but can be softened by reheating with water.If a failure occurs in such items it is easy to carry out repairs by softening the glue with water.Animal GluesCASEIN GLUES It is derived as a precipitate from skimmed m
29、ilk by the action of acids.Glues are obtained in powder form that also contain alkaline solvent,necessary to dissolve the glue on addition of water.Mixing is carried out in cold and setting is partly by evaporation or absorption of water and partly by a natural gelation process.Its adhesion to porou
30、s material is good Its moisture resistance is superior than animal glueCasein Glue A Dry Glue Derived From MilkVEGETABLE GLUE Made from starches(淀粉)or dextrin(糊精)low cost limited strength and limited moisture resistance Gum Arabic is a water soluble vegetable adhesive often used on stamps and gummed
31、 paper envelopes.Cellulose Powder A Type of Vegetable AdhesiveWheat Paste A Type of Vegetable AdhesiveTHERMOSETTING ADHESIVESUREA FORMALDEHYDE One of the commonest adhesives in joinery for general purposes,producing a strong rigid joint if the glue-line is thin.It provides a strong adhesion in a per
32、manently dry environment,cures fast,and is relatively cheap.To make the adhesive,formaldehyde and urea in aqueous solution are allowed to react together to a certain stage and the reaction is then stopped while the resin is still liquid.They are best suited for joining porous material such as wood.I
33、t is used for fabrication of flush colours,laminated timber and decorative laminates.It has a good water resistance but if very hot water or prolonged wetting it could breaks the resin down.MELAMINE FORMALDEHYDE RESIN ADHESIVES Supplied in powder form&mixed with water to give a colourless resin.Set
34、on heating to 100C Give good weather resistance&expensive than urea formaldehyde adhesivePHENOL FORMALDEHYDE available as liquids that polymerise on heating to temperature over 100C.Used for assembly of plywood sheets The resin is applied,the sheets formed and the laminates is then subjected to a ho
35、t press that causes hardening in a period of about 5 min.Cold-curing phenolic adhesives are also available.Can be applied for Plywood,block boards,flush doors EPOXY RESINS It form a good bond with almost any material.It is widely used for structural joints between many types of material including gl
36、ass,metal,thermosetting plastics and concrete.Have excellent mechanical strength Have excellent creep resistance Resistant to weather,acids,alkalis and most hydrocarbon.Epoxy ResinEpoxy ResinEpoxy ResinEpoxy ResinAlkyl Cyanoacrylate Adhesives Have advantage of polymerising very rapidly when spread i
37、n thin films.The reaction being catalysed by water in the very small quantities required which is present on most surfaces.Expensive so uses are confined to bonding of small objects having surfaces that closely conform to one another.They form the basis of Superglues.Must be handled with care to avo
38、id bonding of skin tissues.THERMOPLASTIC ADHESIVES Setting action of these may due to cooling,solvent evaporation or emulsion coalescence.This adhesive is more flexible but weaker and more prone to creep than thermosetting adhesives.So,they are normally not used for structural purposes.POLYVINYL ACE
39、TATE Most important thermoplastic adhesive in building.Chief application being as a wood adhesive for internal use and as a bonding agent for concrete.Most commonly used in emulsion form This polymer is obtained from acetylene&acetic acid.The adhesive sets when the solid particles,on evaporation or
40、absorption of the moisture,cohere to form a tough,clear film which is no longer water soluble.Polyvinyl Acetate Used For Book BindingBITUMINOUS(沥青)ADHESIVES Form good bonds with a number of materials Moisture resistant Flexible Natural or Synthetic rubber&solvents may be included to give the desired
41、 combination of elasticity and strength.Can be obtained in 3 form that is a)Water Based Emulsionb)Solvent Types c)Hot-Applied VarietiesWater Based Emulsions-Form an effective bond between porous materials in situations where long term tensile stresses are not present.-Also used for laying wood-block
42、 flooring and PVC or thermoplastic tilesHot-Applied Varieties-Used for wood-block flooring and in built-up felt roofing.-Application temperature in the region of 150C 200CSolvent Types-Used in laying linoleum and for PVC and thermoplastic tiles though test should be carried out to ensure that staini
43、ng doesnt occur.-Both solvent and emulsion types rely on some degree of absorbency in the substrate to allow absorption/evaporation of the water or solvent.RUBBER BASED ADHESIVESThe most important rubber based adhesives in the construction industry are contact adhesives The adhesive is applied to bo
44、th surfaces and after solvent evaporation,the surfaces are carefully brought together,giving immediate auto-adhesion.Latexes such as styrene butadiene rubber(SBR)are widely used for floor coverings.Latex-modified cements are used for bonding ceramic tiles to a variety of backgrounds,including metal.Thank You
