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

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.