Multifunctional epoxy composites with highly flame retardant and effective electromagnetic interference shielding performances

Multifunctional epoxy composites with low flammability, high ablation resistance, superior electrical conductivity and outstanding electromagnetic interference (EMI) shielding performances are prepared by a two-step procedure. The first step involves pyrolysis of lignin-resorcinol-glyoxal pre-polymer into carbon foams, while the second step is infiltrating flame retardant epoxy resins (FREP) into the highly porous carbon foams. SEM images show that the three-dimensional network microstructure of carbon foams is integrally preserved during infiltration by the epoxy resins, which could serve as an effective pathway for electron transport. For the flame-retardant carbon foam/epoxy (FREP-CF) composite, a UL-94 V-0 classification is achieved. In the cone calorimeter measurement, the peak heat release rate and the total heat release of the FREP-CF composite are reduced by 64% and 37%, respectively, compared to those of the original epoxy resin. The FREP-CF composite can resist approximately 1000 °C flame for 10 min with the temperature on the back side lower than 200 °C, which is much better than the EP-CF composite. Additionally, a notable electrical conductivity of 216 S/m and a superior EMI shielding effectiveness of 33.5 dB are achieved for the FREP-CF composite. This multifunctional epoxy composite enables it a promising candidate for electronics, aerospace and transportation applications.