Cooperative flame retardancy of ammonium polyphosphate and magnesium–aluminum-layered double hydroxide (LDH) in EVA blends

melt blending, with MgAl-LDH as the primary additive and a small amount of APP as the auxiliary flame retardant. The flame-retardant properties, mechanical performance, and char residue characteristics of these blends were systematically evaluated using the limiting oxygen index (LOI) test, UL-94 vertical burning test, cone calorimeter test (CCT), tensile test, and char residue analysis. The results indicated that when the APP content was 8% and the MgAl-LDH content was 47%, the EVA blend achieved a UL-94 V-0 rating, exhibited an LOI value of 29.3%, and demonstrated an elongation at break 52.8% higher than that of the neat EVA (EVA0). This superior performance is primarily attributed to the strong cooperative flame retardant effect of the APP/MgAl-LDH combination, which effectively reduces heat and smoke release during combustion. Furthermore, the incorporation of APP promotes the formation of a dense and continuous char layer on the composite surface, thereby significantly enhancing flame retardant performance. This study is expected to provide a valuable reference for the practical application and green development of flame-retardant EVA materials in the wire and cable industry and construction sector.