Lightweight composite foams for electromagnetic interference shielding with high absorption and excellent mechanical properties

Abstract

Electromagnetic radiation and its associated secondary pollution significantly disrupt the proper functioning of electronic devices and may even pose a threat to human health. Therefore, the design of absorption-dominated electromagnetic shielding materials is of paramount importance. In this study, ethylene propylene diene monomer (EPDM) and polyolefin elastomer (POE) were used as the matrix materials, while carbon black (CB), carbon nanotubes (CNTs), and ferric oxide (Fe₃O₄) were used as fillers. The composite foams with dual loss mechanisms and porous structures were prepared by hot press foaming. The foam exhibits high electromagnetic interference shielding efficiency (EMI SE) and an absorption-dominated shielding mechanism. The dual loss mechanisms consist of dielectric loss from CB and CNTs, and magnetic loss from the incorporation of Fe₃O₄, which mitigates the impedance mismatch between the material and space, thereby enhancing electromagnetic wave absorption. Consequently, the composite foam demonstrates an optimal EMI shielding effectiveness of 34 dB and an absorption coefficient of 0.58, thereby confirming a shielding mechanism dominated by absorption. Moreover, the composite foam exhibits excellent mechanical properties, elastic recovery, shielding durability, and thermal stability, making it well-suited for both conventional environments and potential long-term use in complex and extreme conditions.