One-component polyurethane resin systems

The type of isocyanate, MW and -NCO functionality are controlled to balance drying time and film properties. The drying time is signi- 

E = Ester linkages U s Urethane linkages FA = Fatty acid moiety 

As discussed earlier, many polyurethane resin systems offered for coatings contain free -NCO groups, which are expected to react with appropriate cross-linkers during the curing reaction after application. Since isocyanates are reactive to water, until the 1990s, it was thought 

Component I is generally supplied as a polyol dispersion in water and component II (supplied free from water) is added to component I Just prior to application. 

Two-component polyurethane systems have become very popular for many commercial applications, as they can offer products with low VOC content while maintaining high performance. Such polyurethane systems are increasingly used in industrial coating applications. 

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