Construction of Three-Dimensional Network Hierarchy Structure Based on Melamine Foam for Electromagnetic Shielding

With the rapid development of wireless communication and electronic equipment, there is an urgent need for lightweight and compressible electromagnetic interference (EMI) shielding materials to solve the increasingly serious problem of electromagnetic pollution. Graphene (GP) is widely used in functional materials with excellent electromagnetic interference shielding properties due to its large aspect ratio and specific surface area. Hierarchical structure attached by GP is constructed in melamine foams (MF) with the assistance of sodium alginate (SA) through simple impregnation and freeze-drying methods. Benefiting from such unique hierarchical porous structure, the composite foam achieves a high electrical conductivity of 39.1 S/m and an exceptional electromagnetic interference (EMI) shielding effectiveness (EMI SE) of 45.8 dB in the range of X-band (8.2–12.4 GHz) at only 2 mm thickness, resulting in a significant EMI shielding effectiveness as 3541.7 dB cm2 g–1. In addition, SA endows the improved compressive strength of MF with less effect on the resilience of MF due to the supporting effect of SA. The prepared foams show superior thermal stability, making it possible to expand the range of applications. This work fabricated highly efficient EMI shielding materials for reducing electromagnetic pollution, while also broadening the application areas of EMI shielding materials in complex environments.