Efficient Construction of Hierarchical Polyurethane Composite Foam for High Microwave Absorption Performance
The proliferation of 5G communications and smart electronic devices has intensified electromagnetic wave (EMW) pollution, necessitating microwave absorption materials (MAMs) with high efficiency, lightweight, and flexibility. Traditional MAMs suffer from high density and narrow effective absorption bandwidth (EAB). This work presents a lightweight, flexible microwave-absorbing composite fabricated by in-situ polymerization foaming of polyurethane (PU) with multi-walled carbon nanotubes (MWCNTs) and flaky carbonyl iron (FCI). The hierarchical PU composite foam, designated 3*PFC 0.5-1.0-1.5, achieves an EAB of 15.7 GHz, covering 98.1% of the tested 2–18 GHz range, including S, C, X, and Ku bands. This performance stems from synergistic conductive and magnetic losses, along with impedance matching facilitated by the hierarchical porous structure. The composite maintains low density and high compressibility, offering a promising solution for EMW absorption in 5G, military stealth, and smart devices. The in-situ method ensures strong interfacial adhesion between fillers and matrix, enhancing durability compared to impregnation methods. This study demonstrates a scalable approach to fabricate high-performance MAMs with broad bandwidth and mechanical robustness.