Lightweight and flexible silicone rubber foam with dopamine grafted multi-walled carbon nanotubes and silver nanoparticles using supercritical foaming technology: Its preparation and electromagnetic interference shielding performance

Abstract

Herein, dopamine is grafted onto multi-walled carbon nanotubes (MWCNTs), and then grafted dopamine is used as a chemical activation point to initiate the in-situ synthesis of silver nanoparticles (Ag-NPs). The foam technology with supercritical N2 (Sc-N2) gas was used to prepare a lightweight and flexible silicone rubber foam material with efficient electromagnetic shielding performance. The prepared material has uniform cells and a density of only 0.3 g/cm3. The electrical conductivity can be achieved as high as 5.69 S/m. At the same time, the optimal modified conductive filler MWCNTs conditions are determined: DOPA concentration is 2 g/L, deposition time is 18 h, formaldehyde concentration is 5 g/L and AgNO3 concentration is 16 g/L. From the perspective of electromagnetic interference shielding performance (EMI SE), the value of prepared silicone rubber foam with 15 parts of MWCNT-PDA-Ag (VMPA15) can reach 36 dB, far exceeding the commercial requirement (20 dB). The EMI shielding performance is also improved with the increased thickness of the sample. When the sample thickness is 10 mm, the EMI SE value can be as high as 52 dB; more importantly, this type of VMPA foam has a shielding mechanism based on absorption, which is the most effective for solving the problem of secondary magnetic pollution caused by electromagnetic wave reflection.