Enhanced mechanical property and flame retardancy of halogen‐free PE/EVA composites through crosslinking and carbon fiber inclusion

Abstract Due to the exceptional flame retardancy, environmental protection, cost‐effectiveness, and ease of processing, halogen‐free flame‐retardant polyethylene (PE) composites are attracting wide attention. However, the addition of halogen‐free flame retardants usually leads to significantly decreased mechanical properties of PE composites, which greatly limits its application. Herein, we report a halogen‐free flame‐retardant PE/ethylene‐vinyl acetate copolymer composite (PE/EVA) with excellent flame retardancy and mechanical properties by combining compatibilizer, crosslinking agent, and carbon fiber. The presence of compatibilizer not only improves the compatibility of halogen‐free flame retardants and matrix, but also interacts with the crosslinking agent to form a cladding structure on the surface of carbon fiber. The enhanced interaction between carbon fiber surface and matrix then results in significantly enhanced flame retardancy and mechanical properties of the composite. Specifically, adding 4 phr compatibilizer, 0.5 phr crosslinking agent, and 10 phr carbon fiber will lead to the halogen‐free flame‐retardant PE/EVA composite with a UL‐94 V‐1 level, limiting oxygen index of 27.1, and an increased tensile strength by 84.02% reaching 19.12 MPa. Moreover, further carbon fiber surface modification can further enhance the flame retardancy of the composite probably due to a synergistic flame‐retardant effect caused by the surface modified nitrogen and silicon elements. As a result, the composite achieves UL‐94 V‐0 level and the limiting oxygen index of 27.7 with well‐retained high tensile strength of 15.19 MPa. This work provides a practical strategy for enhancing the flame retardancy and mechanical property of PE‐based composite simultaneously. Highlights Compatibilizer interacts with crosslinking agent to form a cladding structure on the surface of carbon fiber. Crosslinking agent promotes the formation of chemical bonds between modified carbon fiber, compatibilizer, and matrix. Carbon fiber surface modification can enhance the flame retardancy of the composite due to the synergistic flame‐retardant effect.