Molecular design and properties of intrinsic flame‐retardant P‐N synergistic epoxy resin

Abstract In recent years, the poor weather resistance and aging resistance of additive flame retardants have caused researchers to pay attention to reactive flame retardants. A novel P‐N coacting epoxy curing agent with intrinsic flame retardancy was designed and synthesized. The mechanical properties, crosslinking curing properties and flame‐retardant properties of intrinsic flame‐retardant epoxy resin were characterized. The results show that the cross‐linking curing performance of hexa (3,5‐diamino‐1,2,4 triazolyl)‐cyclotriphosphonitrile) (VCP) is lower than that of DDM. This is due to the decrease in cross‐linking density caused by the VCP ring molecular structure. Therefore, the mechanical properties of the epoxy resin cured with VCP decreased, but the flame‐retardant properties of the material significantly improved. The limiting oxygen index of the VCP/EP flame retardant epoxy thermosets was 27.3%, reaching the UL 94 V‐1 level. The peak heat release rate and total heat release rate of the VCP/EP flame retardant epoxy thermosets were significantly reduced. The flame retardancy mechanism was studied by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and x‐ray photoelectron spectroscopy. The results show that the intrinsic flame‐retardant P‐N coacting epoxy resin has excellent curing and flame‐retardant properties.