Morphologies and electromagnetic interference shielding performances of microcellular epoxy/multi-wall carbon nanotube nanocomposite foams

Microcellular epoxy/multi-wall carbon nanotube (EP/MWCNT) composite foams loaded with 0.5, 1.0, 2.0 and 3.0 wt% of multi-walled carbon nanotubes (MWCNTs) were prepared by a batch foaming process with supercritical carbon dioxide (scCO₂). The morphologies of EP/MWCNT composite foams were analyzed by scanning electron microscopy (SEM). It was found that there was a synergic effect between the formation of microcellular structure and the addition of MWCNTs on improving the performances of EP/MWCNT composite foams. The addition of MWCNTs promoted the formation of microcellular structure, and the growth of cells in turn induced the redistribution of MWCNTs. Furthermore, the electromagnetic interference (EMI) shielding effectiveness (SE) of EP/MWCNT solid and foamed composites was investigated. The results indicated that the foaming improved the specific EMI SE from 5.2 to 21.3 dB cm³/g at the MWCNT content of 1.0 wt%. The introduction of MWCNTs and microcellular structure synergistically enhanced the EMI shielding performance of epoxy-based composites.