Synergistic carbonaceous components reinforced multifunctional polyimide foams for fire safety, thermal insulation and microwave absorption

The development of lightweight polymer foams with enhanced thermal stability and fire safety is highly desirable for applications in harsh environments. However, simultaneously improving flame retardancy, thermal protection, and multifunctional capabilities remains challenging due to the complex interplay among polymer degradation, combustion behavior, and structural stability. Herein, multifunctional polyimide foams were fabricated via a facile isocyanate-mediated one-pot strategy by introducing synergistic carbonaceous components, including graphene oxide (GO), carbon black (CB), and carbonized iron–cobalt–nickel Prussian blue analogue derivatives (CPBA), into the polyimide matrix during foam formation. The incorporation of these components effectively modulated the thermal degradation behavior and combustion characteristics of the polyimide foam by constructing interconnected carbon networks, heterogeneous interfaces, and catalytic active sites. Compared with pristine polyimide foam, the composite foam exhibited improved fire safety, with a 23.2% reduction in peak heat release rate, a 55.68% decrease in total smoke production, and a 29.82% increase in char residue. TG-IR analysis and residual char characterization revealed that the enhanced flame-retardant performance was attributed to the synergistic suppression of volatile degradation products and the formation of compact protective char layers. Furthermore, the porous composite structure provided improved thermal insulation, limiting the back-surface temperature increase to only 13.2 °C after heating at 120 °C for 210 s. Meanwhile, the optimized composite foam retained excellent microwave absorption performance, achieving a minimum reflection loss below −40 dB and a maximum radar cross-section reduction of 23.18 dB·m 2 . This work provides new insights into the regulation of polymer degradation behavior through carbon component engineering and offers a feasible strategy for developing multifunctional polyimide foams with enhanced thermal stability and fire safety.