A facile way to fabricate renewable P/N/S-containing ferulic acid-derived epoxy thermosets with excellent flame retardancy

The development of sustainable epoxy thermosets combining high performance, acceptable thermal stability, and outstanding flame retardancy has remained a major challenge. Herein, a facile way were developed to fabricate flame-retardant recyclable epoxy thermosets by the ferulic acid-based epoxy resin (FAE) as matrix and a furfural-based 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-Oxide (DOPO) derivative (DOF) as reactive flame retardant. The obtained bio-based epoxy thermosets showed outstanding fire-resistance and higher glass transition temperature (Tg) compared to bisphenol A epoxy thermoset. With 1.26% loading of phosphorus, it possessed a Tg of 132 °C, a limiting oxygen index (LOI) value of 33.2% and a residual char of 42.1% at 700 °C acquired from TGA analyses. It not only exhibited excellent self-extinguishing effect and reached the UL-94 V-0 rating, but showed remarkable reduction on the heat release and smoke production. SEM observation and Raman spectrum manifested that the epoxy thermosets showed an outstanding ability on intumescent and compact char formation, which could suppress the exchange of heat, oxygen and flammable volatiles.