4197323 - Investigation of novel epoxy-carbamate reaction and coatings made thereof

While reactions of epoxy resins with amines and amides are well-established, this study explores the underexplored reaction between epoxides and carbamates. Carbamates contain amine moieties with reduced nucleophilicity due to adjacent ester groups. We examined the feasibility of epoxy-carbamate reactions, focusing on catalyst requirements and stoichiometric ratios needed to produce coatings with desirable properties. The reaction between diglycidyl ether of bisphenol-A (DGEBA) and carbamate of hydroxypropyl carbamate (CHPC) was initially studied using differential scanning calorimetry (DSC) under both ramped and isothermal conditions, with and without catalysts. Catalysts were screened to optimize the reaction. Coatings were then prepared using different stoichiometric ratios of epoxy to active hydrogens in CHPC. These coatings were characterized using DSC, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) Spectroscopy, and Electrochemical Impedance Spectroscopy (EIS), along with tests for hardness, adhesion, solvent resistance, flexibility, and gloss. The performance of these novel coatings was compared to commercially available epoxy coating systems. Results showed that coatings produced from the base-catalyzed epoxy-carbamate reaction demonstrated an excellent balance of flexibility and hardness. The novel coating system exhibited mechanical performance comparable to epoxy-aliphatic amine systems while surpassing them in corrosion resistance. This study highlights the potential of epoxy-carbamate reactions in developing high-performance coating systems.