Development of amine-based latent accelerator for one-pot epoxy system with low curing temperature and high shelf life

摘要

One-pot epoxy system is widely used in prepreg applications. Achieving a long storage life and at the same time, a low curing temperature is a real challenge in one-pot systems. To deal with these challenges, we developed adducts as latent accelerators for one-pot epoxy/dicyandiamide system through the addition reaction of epoxy, phthalic anhydride and different types of alkanolamine/phenol amines. Fourier transform infrared spectroscopy (FTIR), C-13 nuclear magnetic resonance spectroscopy (NMR) and thermogravimetric analysis (TGA) showed that the so-prepared adducts were long chain tertiary amines. Non-isothermal differential scanning calorimetry (DSC) proved the effectiveness of adducts towards significant reduction of the curing peak temperature of epoxy/dicyandiamide. The analysis of variance (ANOVA) revealed that the acceleration capacity is controlled by adduct ingredients of amine type, amine and phthalic anhydride content. The activation energies (E-alpha) projected by isoconversional methods revealed different E-alpha-conversion profiles for each system that were in agreement with chemorheological results. According to Malek method, Sestak-Berggren model was the most appropriate to fit the experimental reaction rates. Furthermore, for all one-pot epoxy/dicyandiamide samples, no viscosity build-up and epoxide group consumption were detected after 4 months indicating for their relatively long shelf lives.