Microporous transition metal phosphide flame retardant toughened PA6 composites with excellent thermal conductivity and ferroelectric response

Polyamide 6 (PA6) is a widely used engineering polymer with excellent mechanical and thermal properties. However, its inherent flammability, low thermal conductivity, and limited understanding of its nanomechanical and ferroelectric properties limit its engineering applications in high-performance composites. Herein, we fabricate a multi-functional PA6 composite with excellent flame retardancy, enhanced thermal conductivity, and improved ferroelectric response using Microporous Transition Metal Phosphides (MTMP). An optimal 3 wt% MTMP loading resulted in 83 % and 87 % improvement in the fire performance index and the flame retardancy index, respectively. Furthermore, a 30 % reduction in fire growth rate, a 67 % improvement in the smoke-to-heat release ratio, a 35.8 % increase in the LOI value, and a V-0 rating was achieved due to the enhanced radical quenching and condensed phase mechanism of MTMP. The thermal conductivity improved by ∼205 % and the maximum polarization of the composite reached 1.53 μC-cm −2 at 200 Kv/cm. The average permittivity increased to 83.8 with an approximate capacitance of 14.8 pF at the least resistance of ∼1.63 GΩ due to the enhanced ferroelectric response resulting from the charge storage and field-induced phase switching effects of MTMP. A significant improvement in nanoindentation hardness and Young's modulus was obtained with a 129 % improvement in the bulk material tensile strength due to the physically restrictive topological polymer chain interlock mechanism. This study offers an important perspective on the development of multi-functional polymer composites with potential applications in the energy, electronics, aerospace, and automotive sectors. A multi-functional supertough PA6 composite with 83 % and 87 % enhancement in the fire performance index and flame retardancy index. The composites possess high thermal conductivity and an improved capacitance of 14.8 pF with the least resistance of ∼1.63 GΩ at 80 kV/cm. • Single and composite transitional metal phosphides were successfully synthesized. • Metallic phosphide PA6 composites improved the FP1 and FRI by 83 % and 87 %. • The thermal conductivity improved by ∼205 % along with increased maximum polarization. • The composite achieved approximate capacitance of 14.8 pF at the least resistance of ∼1.63 GΩ. • A significant improvement in nanoindentation hardness and bulk material tensile strength was obtained.