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 the stable capture and internal release of CO₂, which achieved gas-phase nucleation and foaming. Additionally, the introduction of wave-absorbing agents improved the absorption mechanism and promoted uniform foaming. This nucleation-free foaming process relies on the induced growth of gas nuclei and the synergistic effect of the wave-absorbing agents, effectively preventing the uneven foaming issues caused by traditional nucleating agents. Ultimately, a lightweight epoxy foam absorbing material (LFAM) was developed. BET tests showed that 2.0 wt% carbon-based wave-absorbing agents (LFAMs-A2) expanded the material's volume to 4.6 times its original size, forming a uniform porous structure. VNA tests revealed that LFAMs-A2 achieved a minimum reflection loss of -13.25 dB and an absorption bandwidth of 3.7 GHz in the 12-18 GHz range. The material with 2.0 wt% ferrite-based wave-absorbing agents (LFAMs-C2) achieved a minimum reflection loss of -26.83 dB at 16.6 GHz and an absorption bandwidth of 5.3 GHz, nearly covering the Ku band. DSC tests indicated that the material maintained good thermal stability at 150 °C. This study provides a new approach for lightweight coatings and structural optimization, with broad application potential in 5G communications, microwave anechoic chambers, and aerospace fields.