Thermal performance and thermal decomposition kinetics of a novel lignin-based epoxy resin containing phosphorus and nitrogen elements

Lignin-based epoxy resins containing phosphorus (P) and nitrogen (N) elements were prepared by blending the epoxy resin (EP) with different amounts of lignin-based flame retardant additive (Lig-F). The thermal performance of EP thermosets was performed via thermogravimetric analysis coupled with Fourier transformation infrared spectroscopy (TG-FTIR). The results showed that the presence of Lig-F had significant influence on thermal stability (tested by TG) and flame retardancy (determined by limited oxygen index, vertical burning and cone calorimeter) of EP thermosets. H-1 NMR and FTIR analyses confirmed the successful synthesis of flame retardant (DOPO-PA) and modification of lignin, and the evolution of gas produced by thermal decomposition was different with different quantities of Lig-F added. Finally, the activation energy (E) of cured 10% Lig-F/EP was measured by two different methods, namely Flynn-Wall-Ozawa and Kissinger-Akahira-Sunoe, which was obviously higher than that of neat EP.