One-step and green synthesis of a bio-based high-efficiency flame retardant for poly (lactic acid)

The synthesis of bio-based high-efficiency flame retardants in accordance with green and facile method is critical yet very challenging for bioplastics, e.g., poly (lactic acid) (PLA). In this study, a bio-based flame retardant named as PF is synthesized by the reaction between phytic acid (PA) and furfurylamine (FA) in water. PF improves the flame retardancy of PLA at low addition. For instance, PLA composite containing only 2 wt% PF passes a UL-94 V-0 classification, and that containing 4 wt% PF exhibits a limiting oxygen index (LOI) of 28.5%, which is 46.2% higher than that of pure PLA. PF slightly reduces the peak heat release rate (PHRR) and total heat release (THR) of PLA in cone calorimeter test (CCT). In detail, 4 wt% PF reduces the PHRR from 362.2 kW/m2 to 332.7 kW/m2 by 8%. Additionally, PLA/PF composite is comparable to the neat PLA in terms of mechanical properties and thermal stability when a UL-94 V-0 rating is achieved. The flame-retardant mechanism analyses demonstrate that PF takes action in both gaseous and condensed phases. It is proposed that PF accelerates the generation of melting droplets to take away heat, suppresses the release of combustible gases and improves the compactness of char layer during combustion. This study provides a green and facile strategy to create bio-based high-efficiency flame retardants for the preparation of fire-safe bioplastics holding a promising future in the industry.