Bioinspired mono-component lignin endowing epoxy resin with simultaneously improving flame retardancy and mechanical properties

As an appropriate bio-based substance of flame retardant, lignin exhibits an increasing focus due to its envi-ronmental friendliness, high-efficiency charring, and renewable property. However, the conventional flame re-tardants containing lignin with high flame safety always confront with deterioration of mechanical properties of matrix. Here, a novel flame retardant (LMA) by assembling lignin with melamine and amino trimethyl phos-phonic acid through electrostatic interaction was constructed. The LMA displayed excellent interfacial strength with epoxy resin resulting from the ring-opening reaction between rich hydroxyl group in LMA and epoxy resin (EP), thereby the tensile strength, impact strength and Young???s modulus of EP-LMA7 increased by 17.9%, 53.7% and 25.7%, respectively. More importantly, EP-LMA7 passed the V-0 rating of UL-94 and the limiting oxygen index (LOI) value achieved 30.2%. Moreover, with respect to EP, the peak of heat release rate and the peak of smoke production rate of EP-LMA7 decreased by 72.3% and 77.5%, respectively. The detailed characterization illustrated that the excellent intumescent charring resulted in the satisfactory flame safety of EP. This work will further broaden the efficient utilization of lignin.