Boosting flame retardancy of thermoplastic polyurethane: Synergistic effect of nickel phosphide nanoparticles and molybdenum disulfide nanosheets

For the first time, a novel nanohybrid based on nickel phosphide (Ni₂P) nanoparticles and molybdenum disulfide (MoS₂) nanosheets was facilely synthesized for enhancing flame retardancy and smoke suppression of thermoplastic polyurethane (TPU). The synergistic effect on flame retardancy is proposed. TPU composite with 2 wt% Ni₂P/MoS₂ hybrid exhibits the best overall flame retardancy, while TPU composites with the same amount of individual Ni₂P nanoparticles and MoS₂ nanosheets are average in performance. Specifically, the 41.2% reduction of peak heat release rate (PHRR) is achieved for TPU/Ni₂P/MoS₂ composite, which is only 16.8% and 26.4% for TPU/Ni₂P and TPU/MoS₂ composites, respectively. In addition, a more intact protective char layer of TPU/Ni₂P/MoS₂ composite can be observed. These results clearly suggest the synergistic effect between Ni₂P nanoparticles and MoS₂ nanosheets. It is hypothesized that physical barrier effect and chemical catalytic ability of Ni₂P/MoS₂ hybrid contribute to the dramatic reduction of heat release and smoke production. The strategy proposed here is a simple yet efficient approach to fabricate high-performance MoS₂-based flame retardants.