Symmetric sandwich-like rubber composites for "green" electromagnetic interference shielding and thermal insulation

Electromagnetic interference (EMI) shielding rubber composites with thermally insulating properties are necessary for some specific sealing fields, but their fabrication is challenging because it is difficult to realize a balance between high electrical conductivity and low thermal conductivity. Herein, symmetric sandwich-like rubber composites composed of an unfoamed core sandwiched by two foamed layers were prepared using a layer-by-layer vulcanization procedure. Importantly, a segregated Fe3O4@carbon nanotube (Fe3O4@CNT) network was constructed within the entire composite. This structure improved the shielding effectiveness (SE) and decreased the thermal conductivity of Fe3O4@CNT/rubber composites. When the density of the foamed layers was 0.60 g/cm3, the thermal conductivity, electrical conductivity, and SE of the resultant composites were 0.14 W/m K, 21.5 S/m, and 40.7 dB, respectively, and their green index (gs) was 2.13, implying that the prepared materials were "green" EMI-shielding composites. This study provides directions on fabricating EMI shielding materials with thermally insulating performance.