Enhanced electromagnetic interference shielding and mechanical properties of foamed epoxy nanocomposites containing carbon nanofiber treated with silicone surfactant

Thermosetting epoxy (EP)-based composites containing various carbon nanofiber (CNF) contents (0–5 wt %) were fabricated using high speed mechanical stirring and surfactant assisting method. Then EP/CNF composites were foamed through a supercritical CO₂ (scCO₂) foaming method. The cellular morphology of the foamed EP/CNF nanocomposites has been analyzed by scanning electron microscopy (SEM), and the results demonstrated that the CNFs could be served as heterogeneous nucleating agent to increase nucleation sites in nanocomposites, leading to higher cell density and larger cell size. The influences of foaming on conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) were investigated. Due to the introduction of microcellular structure, the conductivity was improved from 9.53 × 10⁻⁸ S/cm to 6.75 × 10⁻⁶ S/cm and the EMI SE was enhanced from 12.7 to 16.5 dB at the CNF content of 5 wt %.