Supramolecular wrapped sandwich like SW-Si₃N₄ hybrid sheets as advanced filler toward reducing fire risks and enhancing thermal conductivity of thermoplastic polyurethanes

A sandwich-like melamine/phytic acid/silicon nitride hybrid (SW-Si₃N₄) sheets were prepared by supramolecular wrapping as the hybrid flame retardants for thermoplastic polyurethane (TPU). The introduction of Si₃N₄ sheets as a template could not only induce the generation of two-dimensional phytic/melamine (PAMA) capping layers, but also produce the synergistic flame-retardant effect on TPU composites. Cone test showed that heat release rate (HRR), smoke production rate (SPR) and total smoke production (TSP) values of TPU were decreased obviously by adding SW-Si₃N₄. TG-IR test indicated the dramatic inhibition of aromatic compound, hydrocarbons, CO and HCN release. Besides, the thermal conductivity of composites was obviously improved by adding SW-Si₃N₄. This work may provide better reference for developing multi-functional TPU composites for diverse application.