Synthesis And Properties Of Thermoplastic Polyurethane Hot Melt Adhesive

Polyurethane adhesives has developed very quickly because of its excellent bonding power, prominent elastic behavior, wear resistance, low temperature resistance and so on. It has been widely applied to many industrial departments such as shoemaking, packaging, timbering, automobile, light industry and textile, mechanization and electricity, spaceflight and avigation and so on. At present most polyurethane adhesives in the market are double parts or single part solution adhesives which waste much organic solvent, have high product costs, cause environmental pollution, do harm to the body of people. With strict of law of environmental protection and raising of environmental conservation consciousness of people, environmental protection adhesives becomes the mainstream of the development of the compositive adhesives; Polyurethane hot melt adhesives is a kind of environmental protection adhesive without solvent and environmental pollution which is studied and developed at present in our country and will be popular for the people.In this study, A thermoplastic polyurethane hot melt adhesives based on polyester polyol of adipic acid series as soft segments, isocyanate and chain extender as hard segments is prepared. The effect of constitute of soft segments and hard segments, structure, relative molecular weight, chain extender, isocyanate index(R) and synthesis flow condition on the mechanical properties, crystallinity, binding properties, heat-resistance properties are studied. So the relation between the structure and properties of the thermoplastic polyurethane elastomer is discussed.Polyester polyol which was used for polyurethane hot melt adhesives was synthesized by the condensation polymerization of adipic acid and ethanediol, butanediol, hexanediol. The influence of the mole ratio of alcohol and acid, catalyst and reaction condition (temperature, time, vacuum condition and so on) on the condensation polymerization was studied. The results showed that when the mole ratio of alcohol and acid was 1.25:1, the amount of catalyst was 6× 10-5mol/mol, vacuumwas 95Kpa, polyester polyol with relative molecular mass about 2000 can be prepared. The composition and structure of polyester polyol was characterized by IR and NMR. The crystallinity of the polyester polyol was measured with WAXD.Themoplastic polyurethane hot melt adhesives based on polyester polyol of adipic acid series as soft segments, MDI and low molecular weight binary glycol as hard segments is synthesized by prepolymerization. The effect of isocyanate index, kinds and amount of chain extender and relative molecular mass of polyurethane on the properties of polyurethane hot melt adhesives is studied, make sure the synthesis flow condition of polyurethane hot melt adhesives (reaction temperature, prepolymerization time, chain extender time and so on). The relation between constitute, structure and mechanical properties, binding power, heat-stability is studied by IR, DSC, TGA, GPC and so on. Measured results show that when reaction temperature was 100℃~110℃, prepolymerization time was 2 hours, chain extender reaction time was 2.5 hours, R value was 0.995, the content of chain-extender was 0.5( the mole ratio of chain extender and polyester polyol) thermoplastic polyurethane hot melt adhesive with excellent properties can be prepared. This kind of hot melt adhesive possesses excellent mechanical properties and strong binding strength, especially excellent water washing resistance and dry washing resistance. Its holding ratio of peeling strength exceeds 98 percent. And it is adapted to making excellent properties and slap-up clothing binding liner, possesses wide applying foreground.