Comparative study on the curing kinetics and mechanism of a lignin-based-epoxy/anhydride resin system

Curing kinetics and mechanism of liquid lignin based epoxy resin (LEPL)-maleic anhydride (MA) system accelerated with benzyldimethylamine (BDMA) were studied by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). In order to investigate the difference in the curing process, heating FTIR was used to study the change of the functional group. Complete consumption of the epoxides has been observed after the heating temperature was higher than 110 °C. E constant method and E variable method, to study the dynamic DSC curves, were deduced by assuming a constant and a variable activation energy, respectively. With E constant method, the cure reaction activation energy E, the frequency factor A and overall order of reaction n + m are calculated to be 59.68 kJ mol−1, e20.6 and 1.462, respectively. With E variable method, E is proved to decrease initially, and then increases as the cure reaction proceeds. The value of E spans from 60.16 to 87.80 kJ mol−1. With the E constant method, E variable method and heating FTIR spectra used together, we can have a comprehensive and profound understanding of the cure reactions of the LEPL-MA system.