Preparation and Properties of Epoxy/Multiwalled Carbon Nanotube Nanocomposite Foams with an Alternating Layer Structure

Multilayered epoxy/multiwalled carbon nanotube (EP/MWCNT) composite foams with a density of 0.713 g/cm³ were prepared through the chemical foaming of laminated epoxy sheets in a mold with a fixed cavity. The difference in cell morphology and properties between adjacent layers in the multilayer foams (two- and four-layer) was tuned by MWCNT or chemical foaming agent (CFA) concentration. It was found that the storage modulus and microwave-absorbing ability of the multilayered EP/MWCNT foams were strongly associated with the loading direction, the thermal diffusivity was slightly direction-dependent, and the electromagnetic interference (EMI) shielding effectiveness (SE) was direction-independent. In addition, as the layer number increased, the mechanical, thermal, and electrical conductivity properties and EMI shielding performances of the multilayered composite foams showed different change tendencies. These results indicated that the effect of the multilayer structure on the properties of composite foams was different when they underwent force, heat, or electromagnetic microwave, and the underlying reasons were investigated in detail.