Influence of Carbon Fiber on the Combustion Behavior, Thermal Stability and Mechanical Properties of Ethylene-vinyl Acetate Copolymer (eva) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (dopo) Composites

Ethylene-vinyl acetate copolymer (EVA) is widely used due to its good processability, low density, and low temperature resistance. However, it burns easily and has several disadvantages, such as a high heat release rate and melt dripping, and it emits large amounts of smog and toxic harmful gases. These disadvantages greatly limit the application of EVA in the wire and cable field. In this study, a series of carbon fiber (CF)/9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)/EVA composites are prepared through melt compounding to improve the flame retardancy and mechanical properties of EVA. The flame retardancy, thermal stability, and mechanical properties of the composites are studied through microscale combustion calorimeter experiments, cone calorimeter tests, thermogravimetric analysis, digital camera, and tensile measurements. Results indicate that among the six samples, the EVA-5 composite with 4.0 wt% CF, 16.0 wt% DOPO, and 80 wt% EVA has the highest limiting oxygen index value (25.1%) and reaches the V-1 level of the Underwriters Laboratory-94 test. Compare with that of pure EVA, the peak heat release rate of the EVA-5 composite has reduced by 30.2% and 47.7%. In addition, the total heat release of EVA-5 reduces by 17.0% and 34.8% relative to that of pure EVA. Data of thermogravimetric analysis show that the thermal stability of CF/DOPO/EVA improves with the increase in CF loading. Moreover, the tensile strength and elongation-at-break values of EVA-5 are 14.30 MPa and 1142.87%, respectively, indicating that this material can maintain good mechanical properties. CF not only enhances the tensile properties of EVA but also acts as a skeleton during burning. This action could increase the strength of the carbon layer and enhance the flame-retardant effect of DOPO. CF and DOPO have an enhanced synergistic effect that could improve the flame retardancy, thermal stability, and mechanical properties of EVA composites. This work provides a theoretical basis for the preparation and production of CF/DOPO/EVA composites with good comprehensive performance.