Linear glycidyl carbamate (GC) resins for highly flexible coatings

An approach to the design of highly flexible coatings based on glycidyl carbamate (GC) chemistry is presented. In past work, GC resins had been synthesized by reacting polyisocyanates such as hexamethylene diisocyanate biuret or hexamethylene diisocyanate isocyanurate resins with glycidol. When crosslinked with amines, due to their high functionality, these resins form very hard and tough coatings, but the coatings have limited flexibility. To obtain coatings with good flexibility, several GC resins were synthesized using linear and cycloaliphatic diisocyanates and a combination of diols and triol with glycidol. The combination of linear diisocyanates and diols introduces a more linear structure in the GC resin compositions. Crosslinked coatings were obtained using two amine crosslinkers, para-aminocyclohexyl methane (PACM) and a commercial polyamide, Ancamide-2353 (A-2353). The flexibility of the coatings was characterized using reverse impact test, GE impact test, and elongation at break in tensile test. The coatings were further characterized to determine their chemical resistance, hardness, thermal stability, and corrosion resistance. The diisocyanate composition and composition of diols and triol influenced the performance of the coatings. In order to understand the influence of the composition of the GC resins on their performance, coatings were characterized using differential scanning calorimetry and dynamic mechanical analysis.