Enhanced Flame Retardancy in <scp>PA12</scp> Composites via the Synergy of Aluminum Diethylphosphonate and Melamine Polyphosphate

ABSTRACT To enhance the flame‐retardant properties of polyamide 12 (PA12) and expand its application range, flame‐retardant PA12 composites were developed through melt blending with aluminum diethylphosphonate (AlPi) and melamine polyphosphate (MPP). Testing revealed that a 5:1 ratio of AlPi to MPP achieved outstanding flame‐retardant performance when the total flame‐retardant content was maintained at 25.0 wt%. The synergistic effect of AlPi and MPP significantly enhances the flame retardancy of PA12, achieving a V‐0 rating in the UL‐94 test, with a limiting oxygen index (LOI) value of 30.7%. Additionally, the peak heat release rate (PHRR) is reduced by 52.8% compared with neat PA12, while the carbon residue increases to 2.82 wt%. Scanning electron microscopy (SEM) analysis reveals that the incorporation of AlPi and MPP improves the continuity and homogeneity of the char layer formed during combustion. This enhanced char layer effectively inhibited heat transfer and further degradation of the material. Furthermore, the combination of MPP and AlPi restricted the mobility of polymer chains, increased melt viscosity, and reduced the formation of melt droplets during combustion. The synergistic effect of AlPi and MPP in both the condensed and gas phases contributed to the flame‐retardant performance by forming an effective thermal barrier and diluting heat.