A biobased P/N-containing 2D aggregate for boosting fire retardancy of PA6/aluminum diethylphosphinate via synergy

Engineering polyamide 6 (PA6) is preferred for its superior mechanical properties, yet the intrinsic flammability restricts its industrial applications. As one of the biomass phosphorus-containing chemicals, phytic acid (PA) is favorable for its high phosphorus content and aggregation ability, making it expected to enhance the fire retardancy of PA6. Herein, a melamine-phytate aggregate (MPA) is prepared by electrostatic interaction in aqueous solution, and applied as a synergist for aluminum diethylphosphinate (ADP) in PA6. The strong synergistic effect exists between ADP and MPA towards PA6, especially when their mass ratio is 3:1 and the total loading is 18 wt%. Compared to the neat PA6, this formula allows for remarkable decreases in peak heat release rate (PHRR), total heat release (THR), and maximum average heat release rate (MARHE) by ∼ 48%, ∼ 27%, and ∼ 30%, respectively, as well as a high synergistic efficiency of ∼ 43% in PHRR. This PA6 composite also presents a V-0 rating in the vertical burning (UL-94) test and a high limiting oxygen index (LOI) of 29.7%. This work offers an eco-friendly strategy for developing bio-based P/N fire-retardant aggregates for fabricating PA6 materials with high fire safety.