高分子材料与应用(英文版)-Chapter-7-Coatings-and-Adhesives.ppt

,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Chapter 7,Adhesives and Coatings,Introduction,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,pigments,solvents,and additives.,Introduction,Why Coatings?,For decoration:,Color,Gloss,etc.,For some functions:,erosion resistance,abrasion resistance,slip control,fungal resistance,etc.,Application field,Architecture and furniture,(paint,漆,);,Original equipments manufacture,(OEM,used in factory);,Special Coatings,(used out of factory,for ship,equipment repair,road signs etc.),Introduction,Classification,Based on resin type:,alkyd,polyurethane,polyester,epoxy,.,Based on environment impact:,Traditional solvent coatings,:VOC,pollution,Environment-friendly:,Waterborne,High Solid,Powder,UV-curing,Based on,finish(,漆；末道漆,)system:,One-coat,Multicoat primers,Intermediate coats,and Top coats,2.Coating Resins,Alkyds,Synthesis:,fatty Acid+Polyacid+Polyol,Advantages:,low cost;,interior exposures generally good.,Disadvantages:,exterior durability only fair,Application,finishing metal and wood products.,Polyester,Synthesis:,Polyacid+Polyol+(Styrene,),Advantages:,good interior&exterior durability,Disadvantages:,cost is higher,Application:,furniture,appliances,automobiles,magnet wire,2 components:glass-,reinforced plastic bathtubs,lavatories,boats,cars,Coating Resins,Epoxies,medium-to high-priced,good adhesion(,primers for automotive,),heat resistance(,electrical insulation,),excellent erosion and chemical resistance.,poor ultraviolet-light resistance:,used outdoors,tend to chalk and discolor,.,Acrylics,outstanding weather resistance(,architectural coatings,),;,lacquers and enamels(,the top coats for the automotive),;,excellent exterior durability,Coating Resins,Polyurethanes,price alkyds but 4.5 nm,For water-born coating:need dispersants;ionic interaction,hydrophobic and hydrophilic balance.,4.Additives,Function,affect various areas such as color,water resistance,slip control,foam control,and gloss.,Antioxidant,easily cleavage,form free radical;,e.g.,Phenolic compounds,naphthol,primary and secondary amines,Additives,Thickening Mechanism,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。,Additives,Other additives,Accelerator,Curing agents,Light stabilizers,Defoamer,Dispersing agent(dispersant),Wetting agents,Surfactant,Coating Film Defects,Leveling(,流平,),driven force:surface tension(,).,peak area:coating layer solvent volatilization,valley area flow from peak to valley.,control factors:viscosity,layer thickness.,Sagging(,流挂,),control factors:viscosity,layer thickness,Surface shrinkage(,表面起皱,),Surface volatilization(cure)bulk surface form film first Surface shrinkage,Control factors:layer thickness,volatilization(cure)speed.,6.,Environment friendly coatings,UV-curable coatings,Low VOC,minimum thickness change,Basic components of UV curable coatings,UV-curable Coatings,Advantages,Low VOC,low energy cost,low equipment investment.,Disadvantages,Thickness limit:pigment;,polymerization shrinkage,Photoinitiator leftover:poor exterior durability.,Applications,printings inks;paper coatings;photo-resists for printed circuits and microeletronics,Waterborne coatings,Water-reducible coatings,Water+Solvent as film-forming vehicles,Can use high Mw Resin,Low nonvolatile weight,Water-soluble coatings,Water as solvent,Low water resistant,Latex coatings,(,乳胶漆,),Low VOC,High Mw.,Difficulty to form high glossy coating,Additive complication:dispersants,thickeners,etc.,Used in architecture.,Powder Coatings,Resin type,Thermoplastic&Thermosetting,Film formation on preheated products,Coating Methods,Fluidized-bed powder coating.,Electrostatic fluidized-bed powder coating,Electrostatic-spray powder coating,Advantages&disadvantages,Low VOC;thickness up to 500,m;low energy cost.,Explosion Risk;cannot be used in thermosensitive products.,Summary,Traditional coatings have four basic ingredients.,Environment-friendly coatings have bright future.,Coating industries are really technology-intensive.,ADHESIVES,TYPES OF ADHESIVE,Can be divided 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 adhesives,COMPONENTS 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,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 use 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 Glues,CASEIN GLUES,It is derived as a precipitate from skimmed milk 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 porous material is good,Its moisture resistance is superior than animal glue,Casein Glue A Dry Glue Derived From Milk,VEGETABLE 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 paper envelopes.,Cellulose Powder A Type of Vegetable Adhesive,Wheat Paste A Type of Vegetable Adhesive,THERMOSETTING ADHESIVES,UREA 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 permanently 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.,It 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 on heating to 100,C,Give good weather resistance&expensive than urea formaldehyde adhesive,PHENOL FORMALDEHYDE,available as liquids that polymerise on heating to temperature over 100,C.,Used for assembly of plywood sheets,The resin is applied,the sheets formed and the laminates is then subjected to a hot 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 glass,metal,thermosetting plastics and concrete.,Have excellent mechanical strength,Have excellent creep resistance,Resistant to weather,acids,alkalis and most hydrocarbon.,Epoxy Resin,Epoxy Resin,Alkyl Cyanoacrylate Adhesives,Have advantage of polymerising very rapidly when spread in 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 avoid 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 ACETATE,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 absorption of the moisture,cohere to form a tough,clear film which is no longer water soluble.,Polyvinyl Acetate Used For Book Binding,BITUMINOUS(,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 combination of elasticity and strength.,Can be obtained in 3 form that is a)Water Based Emulsionb)Solvent Types,c)Hot-Applied Varieties,Water 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 flooring and PVC or thermoplastic tiles,Hot-Applied Varieties,-Used for wood-block flooring and in built-up felt roofing.-Application temperature in the region of 150,C,200C,Solvent Types,-Used in laying linoleum and for PVC and thermoplastic tiles though test should be carried out to ensure that staining 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 ADHESIVES,The most important rubber based adhesives in the construction industry are contact adhesives,The adhesive is applied to both 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,