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,Advanced Materials,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Adhesives,Araldite,STRUCTURAL ADHESIVES,Its All In the Chemistry,AdhesivesAraldite STRUCTURAL,Adhesives Chemistry,Variations in chemical formulations produce distinct differences between:,Epoxy adhesives,Polyurethane adhesives,Methacrylate adhesives,All are,thermoset plastics,when heated:,They do not melt,They do not revert back to their pre-reacted forms.,Adhesives ChemistryVariations,Adhesives Chemistry,ALL two-part epoxies,polyurethanes and methacrylates require accurate measuring,of resin and hardener to produce a durable joint:,Use correct mix ratio,Weigh precise amounts of resin and hardener,For cartridges,dispense precisely to attain a,1:1 or 2:1 ratio,Adhesives ChemistryALL two-par,Adhesives Chemistry,ALL two-part epoxies,polyurethanes and methacrylates require thorough mixing,of resin and hardener to attain full physical properties:,Use a square-bottom mixing stick,Use containers with flat bottoms,straight sidewalls,Use paper for epoxy,plastic for,polyurethane,Mix to achieve uniform color with,no streaks,Stir gently to avoid air entrapment,Adhesives ChemistryALL two-par,Adhesives Chemistry,When using,ALL epoxies,polyurethanes,and methacrylates:,Apply adhesive to substrates,immediately,after mixing,Apply a sufficient amount of,adhesive to completely fill the,joint(the first time),Join substrates and clamp as soon as possible,Adhesives ChemistryWhen using,Adhesives Chemistry,Epoxy adhesives,include two-and one-component systems:,Two components,=“A”resin+,“B”hardener,-Epoxy resins have minimal odor,-Amine hardeners have ammonia-,like odor,-Reacting(mix)ratio-A:B-is,determined by the reactive sites,of the components,Adhesives ChemistryEpoxy adhes,Adhesives Chemistry,Epoxy adhesives,include two-and one-component systems:,One component,=contains“A”+“B”,-Epoxy resins are similar to two-component resins,-Hardeners are“chemically hindered”from reacting,until heat is applied(250F/121,C,),-Cured properties are similar to two-component,systems,Adhesives ChemistryEpoxy adhes,Adhesives Chemistry,Epoxy adhesives,characteristics include:,100%solids(contain no solvents),Exothermicgive off heat when reacting/curing,Do not release volatiles during cure,Reaction/cure speed can be accelerated with heat,Cure speed is slower at room-temperature(or cooler),Components react only with each other,Viscosities range from thin liquids to thick pastes,Easy to apply,Adhesives ChemistryEpoxy adhes,Adhesives Chemistry,Cured epoxies,feature numerous benefits:,High strength,rigid bonds,Good electrical insulating,characteristics,Excellent solvent and chemical,resistance,Bond metals,metal/metal,combinations,thermoset plastics,Adhesives ChemistryCured epoxi,Adhesives Chemistry,Araldite,polyurethanes,are two-component systems:,“A”isocyanate resins+“B”polyol hardeners,Contain 100%solids,Resins react with moisture yielding,undesirable hard foam,Reactions are non-reversible(even with heat),Secondary(desired)reactions are with hardeners,Polyol hardeners readily absorb moisture,Precise ratio control is critical;systems may,cure but will remain sticky/tacky,Have a broad range of work lives and,viscosities from liquids to pastes,Adhesives ChemistryAraldite p,Adhesives Chemistry,Cured polyurethanes,offer benefits including:,Good flexibility even at low temperature,Good adhesion to thermoplastic,substrates and dissimilar materials,High impact resistance,Good electrical insulating characteristics,Broad range of hardness(Shore 10A to,Shore 70D),Adhesives Chemistry Cured poly,Adhesives Chemistry,Polyurethane limitations,:,Service temperatures are 250F/121,C,Reactants must be kept dry,May require surface preparation,to remove dust,oils,mold,releases and other contaminants,Adhesives Chemistry Polyuretha,Adhesives Chemistry,Araldite,methacrylate adhesives,are high-strength,two-component systems that can be applied via:,Automated meter/mix dispensing,Conventional mixing,No mixingin which a fast drying lacquer can be,applied up to 30 days before the adhesive is added,to harden and bond the assembly,Adhesives Chemistry Araldite,Adhesives Chemistry,Araldite,methacrylates,feature outstanding,performance characteristics:,Gap filling up to 0.3 in./8mm thick,Good resistance to fatigue,chemicals,humidity and heat,Suitable for bonding greasy/oily,surfaces,Ideal for use on metals,thermoplastics,thermoset composites and dissimilar materials,Good lap shear and tensile strength,Adhesives ChemistryAraldite m,Adhesives Chemistry,Methacrylate adhesives,feature benefits including:,Fast cure,Produce tough bonds,Epoxy-like strength,Join thermoplastics,thermoset,composites,metals,ceramics and,glass,Require minimal surface preparation,Adhesives Chemistry Methacryla,Adhesives Chemistry,Araldite,methacrylates feature the,disadvantage of:,Detectable odor,-Detection level 0.5 ppm,-High discomfort level 25 ppm,-TLV 50 ppm,The odor serves as its
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