Fabrication and Performance Regulation of Lightweight Porous Electromagnetic Absorbing Materials via CO2 Nucleation-Free Foaming of EP

In this study, CO₂ reacted with a curing agent through nucleophilic addition to form ammonium salts, enabling stable capture and internal release of CO₂, thereby achieving gas-phase nucleation and foaming of epoxy resin without the use of nucleating agents. Further, absorbing agent is in-troduced to coupling the absorbing mechanism and assist uniform foaming. The gas-phase nucle-ation-free foaming process, relying on the induced growth of initial gas nuclei and the synergistic effect of wave-absorbing nucleating agents, effectively eliminates the uneven foaming issues caused by traditional solid nucleating agents. The dual mechanisms synergistically optimize the lightweight mesoporous structure and wave absorption performance. Ultimately, a type of light-weight epoxy foam-based absorbing material (LFAMs) was obtained. BET indicate that adding 2.0 wt% carbon-based wave-absorbing agents (LFAMs-A2) expanded the material's volume to 4.6 times its original volume, forming a relatively uniform porous structure. VNA tests showed that in the frequency range of 12–18 GHz, the material containing 2.0 wt% carbon-based wave-absorbing agents (LFAMs-A2) achieved minimum reflection loss (RLmin) reaching -13.25 dB and effective absorption bandwidth (EAB) of 5 GHz. The material containing 2.0 wt% fer-rite-based wave-absorbing agents (LFAMs-C2) achieved minimum reflection loss (RLmin) of -26.83 dB at 16.6 GHz and effective absorption bandwidth (EAB) of 6 GHz, covering the Ku band. Meanwhile, DSC indicate that the material maintains good thermal stability at 150°C. The pre-sent work provides a research approach for lightweight thick coatings and structure-performance synergistic optimization, demonstrating its application potential in 5G communication, micro-wave anechoic chambers, and aerospace fields.