Improved electromagnetic interference shielding performance of silicone rubber/CNTs composites by porous structure design via green supercritical CO2 foaming

Abstract

In this study, the relationship between porous structure and electromagnetic interference (EMI) shielding performance of polymer foams is established. A green supercritical CO2 foaming technology is utilized to construct silicone rubber (PMVS)/carbon nanotubes (CNTs) foams with tunable porous structures (porosity, cell size, cell density and cell gradient structure). Notably, the introduction of moderate porosity (within 40 %) simultaneously enhanced the total EMI shielding effectiveness (SET) and absorption coefficient (A). PMVS/CNTs foam reached a maximum SET of 62.3 dB, a 35.4 % increase over solid PMVS/CNTs composite. Additionally, small-cell PMVS/CNTs foam shows a higher A under the same porosity, while large-cell foam exhibits higher SET. Moreover, gradient porous PMVS/CNTs, combining advantages of large and small cells, maintains a high A (78 %) and exhibits superior SET (52.7 dB), along with exceptional EMI shielding stability (with SET and A retaining 97.7 % and 99 %, respectively, after 1000 cycles of compression). This work provides a theoretical foundation for optimizing EMI shielding performance by regulating porous structures.