Layered structural design of flexible waterborne polyurethane conductive film for excellent electromagnetic interference shielding and low microwave reflectivity

A highly efficient electromagnetic interference (EMI) shielding waterborne polyurethane (WPU) composite film with low microwave reflectivity is designed by constructing an FeCo alloy decoration reduced graphene oxide (FeCo@rGO)/nano silver (Ag) layered structure. The FeCo@rGO layer formed by natural sedimentation at the bottom of the WPU film acts as a microwave absorption layer, and the ultra-thin Ag layer covered on the top surface serves as a highly efficient shielding layer. This unique layered structure combines the microwave-reflecting characteristic of nano Ag and the microwave-absorbing characteristic of rGO@FeCo to achieve strong microwave shielding effectiveness (SE) with low microwave reflection. The obtained Ag/rGO@FeCo/WPU composite film (10 wt% rGO@FeCo and Ag layer of 500 nm in thickness), which is only 300 mu m in thickness, possesses an outstanding EMI SE of 50.5 dB and the microwave reflection coefficient is as low as 0.49 (average SER of 3.2 dB). This flexible and highly efficient shielding film with extremely low reflectivity is suitable for application in portable and wearable smart electronics, and this strategy offers a new method for designing the flexible electromagnetic interference shielding materials with low reflection characteristic.