Intrinsically modified EVA-DC/MH composite cable materials: Triple breakthroughs from tensile strength and long-term aging resistance to fire safety

An intrinsically modified ethylene-vinyl acetate copolymer (EVA) matrix is designed for EVA/MH composite cable materials to improve their mechanical properties, aging resistance and fire safety. In this study, diphenylphosphinic chloride (DC) containing reactive phosphorus groups and benzene ring structure was grafted onto EVA to form EVA-DC. When the EVA-DC content is 40%, the EVA-6 cable has demonstrated high rigidity (Tensile strength increased by more than 50%) and significantly improved aging resistance (retention rate of elongation at break reached 92% at 150 °C after 7 days). Meanwhile, EVA-6 cable material reaches V-0 rating and LOI value as high as 37%, and the peak of smoke production rate decreased by 75%. Furthermore, the peak of heat release rate of EVA-6 material has decreased by over 85%, indicating that EVA-DC possesses enhanced flame retardancy. The flame retardant mechanism of EVA-DC cable materials was also studied. Therefore, intrinsically modified EVA-DC polymer effectively enhances the fire safety, mechanical properties and long-term aging resistance of EVA-DC/MH composite cable materials. Unlike conventional additive flame-retardant systems that often suffer from poor compatibility, this matrix modification approach ensures long-term stability and durability while significantly improving tensile strength.