A polymer compound containing a large number of carbamate chain links in its molecular structure is called polyurethane resin. It is produced from isocarbamate and active hydrogen-containing compounds. Coatings that use polyurethane resin as the main film-forming substance are called polyurethane coatings. In its coating film, in addition to containing a large number of urethane bonds, it also contains ester bonds, ether bonds, unsaturated oil double bonds, biuret and allophanate bonds, etc.
Chemical reaction of polyurethane powder It is a stepwise polymerization or addition polymerization reaction, which is a type of polymerization reaction. Isocyanate r-n=c=o has two accumulated double bonds. It is very reactive and easily reacts with other compounds containing active hydrogen atoms. And its electron distribution is related to the r group.
Oxygen atoms have the highest electron density, so they are electronegative. Nitrogen atoms have a slightly lower electron density, but they are also electronegative. Carbon atoms have the lowest electron density and are electropositive, so the isocyanate group is electron-philic during the reaction and is easily attacked by new nuclear reagents. Both oxygen atoms and nitrogen atoms are electronegative, but the nitrogen atom is more basic, so it preferentially accepts protons to form carbamate.
This melon is an exothermic reaction. Since the paint film formed by polyurethane coatings may contain, in addition to urethane bonds, ester bonds, ether bonds, biuret bonds, allophanate bonds, etc., polyurethane coatings have a variety of excellent properties. Performance, the coating film is not only hard, flexible, wear-resistant, bright, plump, and has strong adhesion, but also is oil-resistant, acid-resistant, solvent-resistant, chemical-resistant, and has good electrical insulation properties. It can be deformed at low temperature or room temperature, and is miscible with a variety of resins. The formula can be adjusted within a relatively wide range to make it suitable for wood, flooring, aircraft, automobiles, machinery, electrical appliances, instruments, plastics, leather, paper, and fabrics. , petrochemical industry, railway vehicles, household appliances and other coatings have been widely used.
At the same time, To correctly understand the material polyurethane, we must also note that with the development of coating technology, new types of polyurethane are constantly emerging. To fully and accurately understand polyurethane resin, we must deepen our knowledge of them. .
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