Thermal performance and thermal decomposition kinetics of lignin-based epoxy resins

Lignin-based epoxy resins derived from depolymerized Kraft/organosolv lignins were blended with a commercial bisphenol A (BPA)-type epoxy resin at various percentages to prepare bio-based epoxy composites. The thermal stability and thermal decomposition kinetics of lignin-based epoxy composites were investigated using thermogravimetric analysis coupled with Fourier transformation infrared spectroscopy (TGA-FTIR) and compared with the conventional BPA-based epoxy resin. The activation energy of the decomposition process of the cured lignin-based epoxy composites was calculated by Kissinger, Kissinger-Akahira-Sunoe (KAS), and Flynn-Wall-Ozawa (FWO) methods. The presence of lignin-based epoxy resin demonstrated a significant effect on the activation energy of the decomposition process in particular at the early and the final stages of decomposition. The increase in the percentage of lignin-based epoxy resins in the composites reduced the initial activation energy of the system. Carbon oxides, methane, carbonyl compounds, amines and aromatic compounds were identified as the principal components during the thermal decomposition of the bio-based epoxy composites.