Synergistic Flame Retardancy of a Bio-based Additive and Intumescent System for Enhanced Fire Safety in Flexible Polyurethane Foams

In recent years, the development of bio-based flame retardants for flexible polyurethane foam (FPUF) has become essential, particularly due to environmental and health concerns associated with traditional petrochemical-derived additives. This study reports the successful synthesis of a novel bio-based flame retardant, NMDPLA, using renewable precursors: meglumine, phytic acid, and phenylboronic acid. NMDPLA was combined with protonated chitosan and ammonium polyphosphate through electrostatic self-assembly to create an intumescent flame retardant (APCS). The incorporation of NMDPLA and APCS notably enhances both mechanical properties and flame retardancy of FPUF. The formulation containing 40 wt% NMDPLA in total polyol and 3.0 wt% APCS achieved a Limiting Oxygen Index (LOI) of 23.6, showed no droplet formation in UL-94 tests, and produced a complete carbon residue. Cone calorimetry results demonstrated reductions in total heat release (THR) and peak heat release rate (PHRR) by 22.65% and 20.48%, respectively, compared to pure foam. Balancing mechanical performance and flame retardancy poses a significant challenge, as traditional additives often compromise one for the other. This work underscores the necessity of developing bio-based alternatives that effectively address this balance, enhancing fire safety while preserving material integrity and supporting the transition to sustainable solutions.