Low thickness electromagnetic wave absorbing polyurethane and IIR composites by interfacial polarization of multi-layer structure

Electromagnetic cooperative strategy has been proved to be an effective approach that can significantly decrease the matching thickness required for reflection loss. However, improving the electromagnetic wave (EMW) absorbing effectiveness with low matching thickness remains challenging for current single-phase absorbing materials. A layer-by-layer construction design is used in our study via a combination with iso-butyl isoprene rubber (IIR) and mixed polyurethane (MPU) as the matrix, with the single-wall carbon nanotubes (SWCNTs) and magnetic powder as fillers. This bilayer composite design resulted in a decrease in matching thickness and a shift in absorption bandwidth to higher frequencies by 40 %–50 %. Furthermore, the trilayer structure of MPU/IIR/MPU was found to stabilize permeability, enhance the thermal stability of the magnetism and improve the shielding effectiveness significantly. The thickness corresponding minimum absorption loss of the trilayer composites decreased and the absorption bandwidth of −10 dB widened by 50 % from 8.2 GHz–9.5 GHz to 10.2 GHz–12.4 GHz.