Synthesis of a curing agent containing trifunctional epoxy groups for powder coatings and its curing reaction kinetics

In this work, tris(oxiran-2-ylmethyl) benzene-1,3,5-tricarboxylate (TOTC) was synthesized by a new two-step method without using harmful epichlorohydrin and served as a curing agent for polyester powder coatings. The chemical structure of TOTC was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The curing behavior and the curing reaction kinetics of TOTC/polyester resin (NH-3307) system were studied by dynamic differential scanning calorimetry. The activation energy Ea was 71.75 kJ mol-1 according to Flynn–Wall–Ozawa method, and the curing reaction of TOTC/NH-3307 system was described by Friedman method. It was found that the curing reaction of TOTC/NH-3307 system was a two-parameter autocatalysis which followed the Šestάk–Berggren model. The nonisothermal curing reaction rate was simulated according to the Šestάk–Berggren model and the experimentally parameters. What is more, the thermogravimetric analysis results showed that the TOTC/NH-3307 system had good thermal stability with an initial decomposition temperature of 374.92°C. The TOTC/NH-3307 cured film exhibited excellent leveling performance by SEM. The results demonstrated that TOTC has efficient curing ability and huge market potential.