Microcellular epoxy/reduced graphene oxide/multi-walled carbon nanotube nanocomposite foams for electromagnetic interference shielding

Microcellular epoxy/reduced graphene oxide (EP/RGO) and epoxy/reduced graphene oxide/multi-walled carbon nanotube (EP/RGO/MWCNT) composite foams were fabricated through a physical foaming method with supercritical carbon dioxide (scCO₂). The morphologies of EP/RGO and EP/MWCNT/RGO nanocomposites were observed by scanning electron microscopy (SEM). It was found that there was a synergic effect between the dispersion of one-dimensional MWCNT and two-dimensional RGO. Morphological and microstructural properties of corresponding nanocomposite foams was characterized to discuss the effect of introducing MWCNT and RGO, and establish a correlation between microcellular structure and filler contents. By controlling the fillers loading and foaming conditions, EP/RGO/MWCNT nanocomposite foams with good electrical conductivity and electromagnetic interference shielding performance can be obtained. When the RGO/MWCNT content was 5 wt%, the volume conductivity of foamed EP/RGO/MWCNT nanocomposites was 9.6 × 10^-5 S/cm, the electromagnetic interference shielding effectiveness (EMI SE) of EP/RGO/MWCNT foams reached 22.6 dB, contribution of SE_A raised to 68%. It should be noted that, the EMI SE of the EP/RGO/MWCNT foams was higher than that of the EP/RGO or EP/MWCNT foams with the same filling content, which demonstrated that the simultaneous introduction of RGO and MWCNT could synergistically enhanced the EMI shielding performance of epoxy-based nanocomposite foams.