Adhesives-Chemistries膠水化學解析課件

1、AdhesivesAraldite STRUCTURAL ADHESIVESIts All In the ChemistryAdhesivesAraldite STRUCTURAL Adhesives ChemistryVariations in chemical formulations produce distinct differences between: Epoxy adhesives Polyurethane adhesives Methacrylate adhesivesAll are thermoset plastics, when heated: They do not me

2、lt They do not revert back to their pre-reacted forms.Adhesives ChemistryVariations Adhesives ChemistryALL 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

3、For cartridges, dispense precisely to attain a 1:1 or 2:1 ratio Adhesives ChemistryALL two-parAdhesives ChemistryALL 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 wi

4、th flat bottoms, straight sidewalls Use paper for epoxy, plastic for polyurethane Mix to achieve uniform color with no streaks Stir gently to avoid air entrapmentAdhesives ChemistryALL two-parAdhesives ChemistryWhen using ALL epoxies, polyurethanesand methacrylates:Apply adhesive to substrates immed

5、iately after mixingApply a sufficient amount of adhesive to completely fill the joint (the first time)Join substrates and clamp as soon as possibleAdhesives ChemistryWhen using Adhesives ChemistryEpoxy adhesives include two- and one-component systems: Two components = “A” resin + “B” hardener - Epox

6、y 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 adhesAdhesives ChemistryEpoxy adhesives include two- and one-component systems: One component = contains “A” + “B” - Epox

7、y resins are similar to two-component resins - Hardeners are “chemically hindered” from reacting until heat is applied ( 250F/121C) - Cured properties are similar to two-component systemsAdhesives ChemistryEpoxy adhesAdhesives ChemistryEpoxy adhesives characteristics include: 100% solids (contain no

8、 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 applyAd

9、hesives ChemistryEpoxy adhesAdhesives ChemistryCured 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 epoxiAdhesives Ch

10、emistry 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

11、 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 pAdhesives Chemistry Cured polyurethanes offer benefits including: Good flexibility even at low temper

12、ature 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 polyAdhesives Chemistry Polyurethane limitations: Service temperatures are 250F/121C R

13、eactants must be kept dry May require surface preparation to remove dust, oils, mold releases and other contaminantsAdhesives Chemistry PolyurethaAdhesives Chemistry Araldite methacrylate adhesives are high-strength, two-component systems that can be applied via: Automated meter/mix dispensing Conve

14、ntional 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 ChemistryAraldite methacrylates feature outstandingperformance characteristics:Gap filling up to 0.3 in./8mm thickGo

15、od resistance to fatigue, chemicals, humidity and heatSuitable for bonding greasy/oily surfacesIdeal for use on metals, thermoplastics, thermoset composites and dissimilar materialsGood lap shear and tensile strengthAdhesives ChemistryAraldite mAdhesives 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 MethacrylaAdhesives ChemistryAraldite methacrylates feature thedisadvantage of:Detectable odor - Detection