Preparation of a novel lignin-based flame retardant for epoxy resin

A renewable and eco-friendly lignin-based flame retardant was prepared to improve the flame retardant performance of epoxy resin (EP) by green and convenient one-step reaction of Ammonium Polyphosphate (APP), Melamine (MEL) and Al-lignin. Thermal and flame retardant properties test results showed that the properties of epoxy resin were significantly improved after adding 20% of flame retardant. Its carbon residue increased by 15.3 wt % and limit oxygen index value increased from 26.7% to 36.1%. In addition, it also showed excellent smoke suppression effect and low heat release rate. Its total smoke production (TSP) was 9.9 m2 and total heat release (THR) rate was 53.1 MJ/m2. In contrast, the TSP and THR of EP were much higher than 9.9 m2 and 53.1 MJ/m2, respectively. Kinetic analysis showed that the conversion rate ranging from 0.05 to 0.85 corresponded to activation energy between 97.83 kJ mol−1 and 327.45 kJ mol−1. Flame retardant mechanism showed that the performance of this renewable and eco-friendly lignin-based flame retardant was excellent in fire suppression and smoke suppression.