Anti-salt spray and highly conductive composite foams with engineered closed-cell structures for excellent electromagnetic interference shielding

Electromagnetic interference (EMI) shielding materials with excellent shielding performance, salt spray resistance, and light weight are crucial for electronic devices operating in harsh environments. Here, anti-salt spray and conductive foams with high shielding effectiveness were successfully developed. Firstly, Ag conductive networks were constructed on the surface of melamine foams via polydopamine-assisted electroless plating. Subsequently, reduced graphene oxide (rGO) with dual functionality was introduced through dipping method. The rGO films not only enhanced the shielding effectiveness by creating multiple interfaces and conductive pathways through sealing the open-cell structures (70 dB → 92 dB), but also improved salt spray resistance by forming a protective layer over the Ag surface. Finally, an ultra-thin polydimethylsiloxane (PDMS) coating was applied to further enhance salt spray resistance through superhydrophobic surfaces (contact angle ≈ 153°), resulting from its inherent low surface energy and the surface roughness generated by the aggregated Ag particles. Moreover, PDMS increased the mechanical durability of the composite foams by encapsulating the conductive network and matrix like “glue”. The composite foams exhibited excellent EMI shielding effectiveness (90 dB) and maintained performance stability after salt spray corrosion and compression damage. This work presented a method to develop high-shielding-efficiency foams for harsh environment applications.