MWCNT-Reinforced Polymethacrylimide Foams for Broadband Electromagnetic Wave Absorption

In the realm of electromagnetic wave absorption materials, achieving a combination of broad absorption bandwidth, high absorption intensity, and practical versatility presents both a scientific challenge and an engineering necessity. This study introduces a lightweight, high compressibility poly(methacrylimide) (PMI) composite foam with enhanced electromagnetic wave absorption properties. The multiwalled carbon nanotubes (MWCNT) and PMI were composited by ultraviolet (UV) photoinitiation prepolymerization, afterward combining the copolymerization curable-hot air method to prepare MWCNT/PMI composite foam. The resulting MWCNT/PMI composite foam with a minimal MWCNT content of less than 4.0 wt % exhibits a remarkable reflection loss of −55.0 dB and an extensive effective absorption bandwidth of 16.0 GHz within the 2–18 GHz range, attributable to its optimized porous structure and elevated dielectric loss. The complete frequency range of 2–18 GHz can be efficiently absorbed by MWCNT/PMI composite foam, making it ideal for broadband wave absorption. Additionally, composite foams all satisfy the requirements for lightweight design and high strength of microwave-absorbing materials due to its lightweight, good compressive strength, and heat resistance, making it more competitive in engineering applications.