Application of Melem and Aluminum Diethylphosphinate in the Synergistic Flame Retardancy of <scp>PA6</scp> : Composites Preparation and Properties

ABSTRACT Triazine compounds are widely used as nitrogen‐based halogen‐free flame retardants. The commonly applied melamine has issues like low decomposition temperatures and a single flame‐retardant element. Herein, melem (MEL), the trimer melamine with higher thermal stability, was synthesized using a one‐step calcination method. It was mixed with aluminum diethylphosphinate (ADP) to obtain a synergistic flame retardant. Using the melt blending process, the polyamide 6 (PA6) composites of PA6, MEL, and ADP were produced. The composites containing MEL and ADP exhibited excellent flame‐retardant performance, including self‐extinguishing time, droplet count, and residual carbon content. When the mass ratio of MEL to ADP was 1:3 and the total loading reached 20 wt%, the PA6 composites achieved a V‐0 rating in vertical burning (UL‐94) tests, with limiting oxygen indices (LOI) reaching 33.5%. MEL decomposed into inert gases to provide gas‐phase flame retardancy, while ADP and MEL synergistically promoted the formation of a dense carbon layer, providing solid‐phase flame retardancy. The tensile strength of PA6/20MEL‐ADP‐1 was reduced by 29.61% compared to PA6. Its excellent comprehensive performance enabled its application in automobiles and electronic components. This work provides a synergistic strategy for high thermal stability triazine flame retardants and high‐performance fire‐retardant PA6.