High-performance cable materials for maglev trains prepared by the multiple synergistic regulation effects of the functionalized ionic liquids on EVA-based composites

By structural design, a new type of highly functional ionic liquid (NHFIL) was synthesized by combining 1-vinylimidazole with tris(2-chloroethyl) phosphate through a one-pot method. When it is melted into the polymer composite, the highly reactive vinyl of NHFIL promotes the cross-linking within the polymer system to enhance the compatibility between the inorganic filler and polymer matrix and further improve the mechanical properties of the composite, additionally, the N and P elements would generate non-flammable gas phase and carbonized layer during combustion, which endows the polymer composites with remarkable flame-retardant performance. On this basis, the low-smoke flame retardant ethylene–vinyl acetate (EVA)-based composites were prepared by introducing NHFIL into the industrial formula of the cable sheath material for maglev trains. The effects of the composition and molecular structure of NHIFL on the interfacial compatibility, microstructure, mechanical properties, and flame retardancy of composite materials have been studied in detail. The results indicate that with the addition of NHFIL, the cross-linking degree, gel content, thermal stability, mechanical properties, oil resistance, and the flame retardancy of the EVA-based composites were comprehensively improved. Significantly, with a low addition of 3.5% NHFIL, the gel content reaches 90.3%, the carbon residue reaches 42.7%, and the limiting oxygen index (LOI) reaches 36.3%, and surprisingly, the oil resistance increased by five times, which endows the composites with great application potential in cables of major transportation equipment.