A sandwich-structured composite with fire-through electromagnetic interference shielding for extreme thermal environments

Conventional conductive polymer composites often lose electromagnetic interference (EMI) shielding capability under high-temperature or flaming conditions due to poor thermal stability and structural collapse, limiting their use in environments requiring both fire safety and signal integrity. This study presents a sandwich-structured composite to address this issue, featuring a Ti 3 C 2 T x MXene-coated ramie fabric inter layer encapsulated within thermoplastic polyurethane (TPU) layers containing a carbon black (CB)/ammonium polyphosphate (APP) system. This architecture provides structural reinforcement and enables a synergistic shielding and flame-retardant mechanism. With a 30 wt% CB loading, the composite exhibits an exceptional EMI shielding effectiveness of 56.83 dB in the X-band and achieves a UL-94 V-0 rating. Notably, it retains remarkable shielding stability under extreme thermal conditions, preserving 36.12 dB after cone calorimeter testing. Furthermore, it maintains 99.99% electromagnetic wave attenuation even after direct exposure to an alcohol lamp flame for 20 min. This performance originates from a synergistic effect, where the burning of the outer TPU/CB/APP layers promotes the formation of a protective conductive char through physicochemical interactions, which works in tandem with the intact, highly conductive ramie/Ti 3 C 2 T x MXene inter layer to maintain the shielding integrity. This work provides an innovative strategy for developing high-performance EMI shielding materials for harsh environments. • A sandwich composite maintains structural integrity and EMI shielding ability after combustion. • Achieves 56.83 dB EMI shielding (X-band, >99.999% attenuation) with UL-94 V-0 rating initially. • Shielding 99.99% EMI after 20 min alcohol lamp burning, retaining 36.12 dB even after cone calorimeter test.