There is a growing interest to lower the cure temperature of powder coatings and expand the application of this technology to heat sensitive substrates. In the field of polyurethane coatings, diethylmalonate (DEM) blocked isocyanates are broadly used as crosslinkers in liquid coatings. They are well known for their long shelf life and especially for their lower curing temperature in comparison with other blocking agents. Nonetheless, so far no solid DEM materials are known that are suitable for powder coating applications. For the first time solid DEM based crosslinker was successfully designed and developed having significant application potential in the powder coatings field. A key for the design of these materials is a comprehensive knowledge of the blocking reaction, which was thoroughly investigated by Nuclear Magnetic Resonance (NMR) spectroscopy and Gel Permeation Chromatography (GPC). The cure response of the crosslinker when reacted with the hydroxyl functional resins was investigated as a function of the molecular weight, functionality, and hydroxyl number. Examples of the coatings formulations and the details of the coating properties are presented.
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