Facile Preparation of Nickel Phosphide (Ni₁₂P₅) and Synergistic Effect with Intumescent Flame Retardants in Ethylene–Vinyl Acetate Copolymer

In this paper, nanoporous nickel phosphide (Ni₁₂P₅) was synthesized by using a novel hydrothermal method, and its structure was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Then it was used as a synergistic agent with intumescent flame retardant (IFR) in the ethylene–vinyl acetate (EVA) copolymer. With the addition of 2 wt % Ni₁₂P₅ and 28 wt % IFR, the LOI value increased from 30.5 to 34.5. The UL-94 test showed that EVA with 25 wt % IFR burned and had no rating, but with the addition of 2 wt % Ni₁₂P₅ and 23 wt % IFR, it could reach V-0 rating. The CCT results revealed that the Ni₁₂P₅ and IFR system could result in excellent flame retardance. The TGA data indicate that Ni₁₂P₅ can increase the thermal degradation temperature and the charred residues after burning. Moreover, the mechanical and electrical properties of EVA composites are also investigated.