Para‐Toluenesulfonyl Isocyanate‐Ethylenediamine Adduct as a Thermal Latent Curing Agent for Epoxy Resins

ABSTRACT This study focused on the synthesis, characterization, and application of a reversible thermal latent curing agent, p‐toluenesulfonyl urea ethylenediamine, obtained through the reaction of p‐toluenesulfonyl isocyanate with ethylenediamine. The chemical structure and thermal properties of the curing agent were characterized using 1 H NMR, FTIR, TGA, and DSC. The curing agent was then incorporated into diglycidyl ether bisphenol A to formulate a one‐component epoxy resin, which was analyzed using FTIR, DSC, DMA, rheometry, and optical microscopy. The curing kinetics of the one‐component epoxy resin (OCER) were investigated through dynamic and isothermal DSC analyses, demonstrating that the formulation remained stable up to 100°C and underwent complete curing at 140°C. The incorporation of the sulfonyl urea moiety effectively reduced the curing temperature compared to conventional urea‐based thermal latent curing agents. Isothermal curing at 140°C resulted in a fully crosslinked network with a glass transition temperature of 115°C, as determined by DMA. This study introduced a sulfonyl urea‐functionalized thermal latent curing agent for epoxy resins and explored the effects of urea‐based latency and sulfonyl‐mediated reversibility on curing behavior and final thermomechanical properties. The findings highlighted the potential of this approach for developing advanced one‐component epoxy resins with improved processability and tunable curing characteristics.