Novel Thermal Latent Curing Agents for Epoxy Resins Based on Dual-Locked Aminopyridines by Amidation and <i>N</i>-Oxidation
Yukai Ito, Daisuke Aoki, Koji Arimitsu
Abstract
High Resolution Image Download MS PowerPoint Slide Thermal latent curing agents are very important industrially because they can cure epoxy resins at a set temperature and can be stored as one-component systems. However, it remains difficult to achieve both a long pot life and high reaction efficiency. Herein, we present a dual-locked thermal latent curing agent based on aminopyridines, protected by amidation and N -oxidation, designed to enhance both pot life and final curing efficiency. We demonstrated that this dual-locked aminopyridine undergoes stepwise deprotection during the epoxy curing process, as evidenced by 1 H NMR and MALDI-TOF MS analyses of model epoxy polymerizations. The curing temperature of epoxy resin with the dual-locked aminopyridines was modifiable within the range 120–154 °C, influenced by the electron density on the N -oxide. Furthermore, the dual-lock strategy was found to significantly improve the storage stability of one-component epoxy resins and promote the curing of epoxy with high efficiency compared to unprotected aminopyridines.