Strong synergistic effects between P/N-containing supramolecular microplates and aluminum diethylphosphinate for fire-retardant PA6

•A melamine-based P/N-containing supramolecular microplate MTP was prepared.•Combining MTP and ADP enables large reductions in PHRR and THR of PA6.•Superior synergistic effects between MTP and ADP in PA6 are demonstrated. Mechanically strong polyamide 6 (PA6) is an important engineering plastic, but its inherent flammability usually causes fire hazards. Aluminum diethylphosphinate (ADP) can reduce the flammability of PA6 yet fails to effectively suppress the heat release. Herein, we report a phosphorus/nitrogen (P/N)-containing supramolecular microplate (MTP) synthesized by an aqueous reaction between melamine and amino trimethylene phosphonic acid (ATMP). Combining 5 wt% MTP and 15 wt% ADP, the resulting PA6 exhibits a 67% reduction in peak heat release rate (PHRR) and a 29 s delay in ignition time compared with those of pure PA6, as well as a UL-94 V-0 rating and a high limiting oxygen index (LOI) of 28.3%. The barrier effect of the char in the condensed phase is mainly responsible for such high fire safety. This work provides a green approach to synthesizing strong P/N-based synergists for ADP, allowing the creation of high-performance fire-retardant PA6.