Sandwich-Structured Free-Standing Films with Excellent Flame Retardant Performance and Effective Electromagnetic Interference (EMI) Shielding Capability

EMI shielding films are increasingly in demand for wireless networks, wearable electronics, and navigation control systems. Given the flammability of polymers and their prolonged high power operation, it is imperative to consider the environmental and human health impact arising from fire incidents during usage. Consequently, there is a strong need to develop easily manageable and highly scalable flame-retardant EMI shielding films. Herein, we present a viable approach for fabricating a series of flexible and flame-retardant films with a sandwich structure that offers adjustable EMI shielding performance. This approach involves coating plating silver nanowires (AgNWs) assisted by polydopamine (PDA) on a commercially available nylon mesh (PA6 mesh), followed by applying a flame-retardant polyvinyl alcohol/guanidine phosphate (PVA/GP) coating. When sprayed coating 0.6 mg/cm² AgNWs, the films exhibit an EMI shielding effectiveness (SE_T) up to 55.11 dB, capable of blocking 99.999% of EM waves. Besides, such film possesses remarkable self-extinguishing property and a high thermal diffusion coefficient of 3.54 mm²/s. Therefore, the highly lightweight sandwich film holds great promise for multifunctional applications in EMI shielding on a large scale.