Electrochemically Exfoliated Graphene Synergized With MPP/ADP for In Situ Polymerized Flame-Retardant PA6 Composites

Polyamide 6 (PA6) is inherently flammable and prone to severe melt-dripping, which severely restricts its application in aerospace, rail transit, and public safety sectors. To address this, we developed a complementary flame-retardant system by incorporating electrochemically exfoliated graphene (GR), melamine polyphosphate (MPP), and aluminum diethylphosphinate (ADP) into PA6 via in situ polymerization. The thermal stability and interactions among the three components were thoroughly investigated. The results indicate that the optimized formulations exhibit significant flame-retardant enhancement. Specifically, the GR/MPP/ADP/PA6-012 and GR/MPP/ADP/PA6-75 composites achieved limiting oxygen index (LOI) values of 35% and 29%, respectively, and both passed the vertical burning test and achieved V-0 rating, without any dripping. In cone calorimetry, the GR/MPP/ADP/PA6-57 composite demonstrated the most effective heat-release suppression, with the peak heat release rate (pHRR) and total heat release (THR) significantly reduced to 76.3 kW m −2 and 37.7 MJ m −2 , respectively. Mechanistic analysis reveals that GR forms a continuous, compact physical barrier during combustion, effectively hindering heat transfer. MPP promotes the formation of an expanded char layer, enhancing condensed-phase protection. Meanwhile, ADP releases PO · radicals in the gas phase to quench flame-active species and simultaneously promotes char formation. The three components work complementarily, establishing a multi-level “barrier–charring–quenching” flame-retardant network. This study proposes an efficient and environmentally friendly flame-retardant strategy for PA6. By optimizing the ratio of each flame retardant, the resulting composites exhibit superior flame-retardant performance, offering new insights into the flame-retardant modification of engineering plastics and the design of multi-component systems. Highlights GR/MPP/ADP flame-retardant system for PA6 was developed via electrochemistry and in situ polymerization. Electrochemically exfoliated GR forms a continuous two-dimensional physical barrier in PA6 with excellent dispersibility. The ternary system achieves an LOI of 35% and vertical burning test V-0 rating without any dripping. Optimized composite reduced pHRR by 85.3% and THR by 28.5% in cone calorimetry. Synergistic GR/MPP/ADP system builds a barrier–charring–quenching flame-retardant network.