Flexible TPU/MWCNTs Composite Foams with Dual‐Gradient Structure for High Absorption and Stable Electromagnetic Interference Shielding Performance

With the rapid development of portable electronic devices, lightweight, and flexible electromagnetic interference (EMI) shielding composites have been widely used, but the problem of secondary radiation pollution caused by impedance mismatch needs to be solved urgently. In this study, flexible thermoplastic polyurethane (TPU)/multi‐walled carbon nanotubes (MWCNTs) composite foams with dual‐gradient structure are successfully obtained by the design of filler gradient distribution combined with supercritical carbon dioxide foaming. Thanks to the synergistic effect of the gradient of conductive filler and cell structure, composite foams with dual‐gradient structure show optimized impedance matching and effectively improved absorption of electromagnetic waves compared with homogeneous foams, whose A value could reach 0.75. The dual‐gradient structure design can generate the reflection and polarization of multiple interfaces, and achieve superior impedance matching, so as to improve absorption ability to electromagnetic waves of EMI shielding composite foams, which provides a simple strategy to alleviate the issue of secondary radiation pollution.