Fabrication of flexible polyimide/rGO composite foams and their derived carbon foams for thermal insulation and EMI shielding applications

In this work, a facile microwave-assisted foaming and thermal imidization treatment method was proposed to fabricate flexible polyimide (PI)/rGO composite foams with anisotropic pore structures. The PI/rGO composite foams (PIF/rGO) were used as the starting derivatives to prepare carbon foams that demonstrated excellent anisotropic thermal insulation and electromagnetic interference (EMI) shielding applications. The directional growth of pore structures during the foaming period resulted in the formation of aligned ellipsoidal strip-like pore structure in the horizontal direction (i.e., perpendicular to the pore growth direction), which was attributed to the escape of foaming gases such as tetrahydrofuran, methanol and H2O. The homogeneous dispersion of rGO in the PI-derived carbon skeleton endowed corresponding carbon foams with excellent mechanical and thermal stability, high thermal insulation and electrical conductivity (sigma) as well as absorption dominated EMI shielding performance. The sigma and EMI shielding effectiveness (SE) of carbon foams showed an increasing trend with increasing rGO content. The sigma, EMI SE and specific EMI SE of the carbon foams reached up to 33.0 S/m, 49.0 dB and 8792.8 dB/(g/cm2) in the horizontal direction, respectively. Therefore, this work provided a facile strategy to fabricate lightweight and anisotropic pore structure rGO-containing PIFs and carbonized derivatives, which demonstrated promising applications in high-end industrial fields.

Automated summary

In this study, a facile method was proposed to fabricate flexible polyimide (PI)/rGO composite foams with anisotropic pore structures through microwave-assisted foaming and thermal imidization treatment. The PI/rGO composite foams were used as starting materials for preparing carbon foams with excellent anisotropic thermal insulation and electromagnetic interference shielding applications. The results showed that the carbon foams exhibited increasing electrical conductivity and EMI shielding effectiveness with increasing rGO content.