Construction of multifunctional linear polyphosphazene and molybdenum diselenide hybrids for efficient fire retardant and toughening epoxy resins

Epoxy resins (EP) are deemed as one kind of most commonly used thermosets, but immanently suffer from inflammability and brittleness. Herein, we report a newly designed hierarchical molybdenum diselenide (MoSe2) nanotubes assembled from several-layered nanosheets, and then merged with linear polyphosphazene (LPP) for constructing LPP-MoSe2 hybrids. LPP-MoSe2 possesses great advantages in improving the properties of EP for their typical nanotube structure and the combination effect of transition metal, phosphorous and nitrogenous compounds. The developed EP/LPP-MoSe2 composites present obvious reduction in flammability, obtaining a high LOI value of 29% and reaching V-0 rating in UL-94 test. They also exhibit obvious reduction in the heat hazards of EP, such as peak heat release rate (39.0%) and total heat release (24.8%), as well as the toxicity hazards including total smoke production (31.3%) and the yields of CO and CO2. Gas-phase and condensed-phase mechanism are elucidated to explain the contribution of LPP-MoSe2 to the fire retardation of EP. Moreover, the addition of LPP-MoSe2 can also obviously enhance the mechanical properties of EP. The impact strength of EP is only 9 kJ/m2, while EP/LPP-MoSe2 3.0 can reach up to 14.2 kJ/m2. Based on tensile test, the well-dispersed LPP-MoSe2 also leads to significant elevation in tensile strength (74.6%) and elongation at break (100%) of EP. Our data demonstrate that LPP-MoSe2 shows impressive performance in developing high-performance EP composites, thereby broadening the practical application of EP.