Eco-friendly mechanochemical synthesis of hybrid phosphide flame retardants for enhanced fire safety in epoxy resins

Traditional synthesis methods for metal phosphides are often inefficient and not environmentally friendly due to complex procedures. Here, we propose an eco-friendly and efficient mechanochemical method for phosphide flame retardant synthesis through high-energy ball milling. Specifically, solid red phosphorus and Ti3AlC2 were directly reacted in the milling jar, producing a hybrid flame retardant with TiP and AlP as the main active components (TiP/AlP@C). It demonstrates that the TiP/AlP@C exhibited excellent performances, reducing the maximum thermal decomposition rate of epoxy resin by 35.3%, the maximum carbon monoxide release rate by 29.3%, and the maximum smoke release rate by 11.3%. These findings suggest that the synthesized TiP/AlP@C primarily exerts its flame-retardant effect by catalyzing the formation of a protective char layer, which acts as a barrier during combustion. This study confirms the effectiveness and scientific validity of the innovative mechanochemical synthesis method for advanced flame retardants.Highlights Hybrid phosphide flame retardants were prepared by high energy ball milling. The milling speed and time are crucial for the mechanochemical reaction. Hybrid phosphide additive is efficient in reducing fire hazard of epoxy resin. A synergistic charring effect from hybrid metal phosphides is proposed.