Fabrication of ultra-high strength MWCNTs/CI /PI rigid composite foam with excellent microwave absorption performance by pressure foaming method

Polyimide (PI) foam exhibits excellent high-temperature resistance and outstanding physical and chemical stability, making it an ideal matrix for absorbing materials. However, the growing demand for absorbing materials that can serve as load-bearing components has revealed that existing polyimide composite foams often fall short of practical application requirements due to their low mechanical properties. The study employed a simple foaming method using isocyanate-based polyimide as the foam base under a 0.2 MPa atm. Multi-walled carbon nanotubes (MWCNTs) and carbonyl iron (CI) powder were added sequentially to the precursor solution. Under the filling parameters of 2.0 % MWCNTs and 10 % CI powder, the compressive strength of polyimide composite foam reaches 16.2 MPa and exhibits excellent microwave absorption properties, with a minimum reflection loss (RL_min) of −62.51 dB and an effective absorption bandwidth (EAB) of 7.86 GHz. Additionally, the prepared composite foam has potential infrared stealth capability. This work offers new insights for rapid and low-cost manufacturing of high-strength absorbing foam.