16 сентября, 2015 
Pokraskin Within the prepolymer structure of moisture-setting polyurethane adhesives, there are still isocyanates. These polyurethane adhesives react with the ambient moisture according to the equation shown in Figure 5.20; polyureas or biurets are generated by crosslinking. Moisture-curing polyurethanes are used in the furniture-making industry, in the manufacture of motor homes, and as glazing adhesives in car manufacture.
Hydroxyl polyurethanes are thermoplastics with a hydroxyl group content of 0.5-1.0%, and are produced by a reaction of MDI with polyester diols. Typically they have a mean molar mass ranging from 50000 to 200 000 g mol-1. For the bonding of shoe soles, hydroxyl polyurethanes are end-modified with a solvent.
Moisture-setting thermoplastic polyurethane hot melts are obtained when hydroxyl polyurethanes are mixed with polyisocyanates. Their resistance to heat is increased by a crosslinking which takes place at room temperature.
Emulsifying or dispensing linear polymers in water produces aqueous polyurethane dispersion adhesives. For this purpose it is necessary either to add emulsifiers, or to incorporate hydrophilic groups or long hydrophilic polyol segments into the polymer matrix. Dispersion adhesives are used primarily in the packaging and textile industries.
70 I 5 Chemistry and Properties of Adhesives and Primers
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