Ultralow-threshold and efficient EMI shielding PMMA/MWCNTs composite foams with segregated conductive network and gradient cells

Abstract

In this paper, a kind of lightweight poly(methyl methacrylate) (PMMA)/multi-walled carbon nanotubes (MWCNTs) composite foam with high electromagnetic interference (EMI) shielding performance was successfully fabricated by using solution coating process and supercritical fluid-assisted foaming technology. Due to the selective distribution of MWCNTs at the boundary of PMMA phases and the concentrating of MWCNTs within cell walls, the composite foam exhibits good electrical conductivity under low filler content and its percolation threshold was as low as 0.019 vol%. Moreover, trimodal microcellular structure was generated due to the gradient MWCNT concentration along the radial direction of PMMA microspheres. As a result of the segregated structure and multimodal cell structure, the PMMA/MWCNTs (5.0 wt%) foam have a good combination of low density (0.49 g/cm3), high electrical conductivity (3.19 S/m) and high shielding effectiveness (35.9 dB). Its specific shielding effectiveness is as high as 356.5 dB・cm2/g, which is superior to many reported polymer nanocomposites. The nanocomposite foams also had good mechanical properties. This work provides an optional strategy for designing multifunctional nanocomposites for efficient EMI shielding.

Keywords

• polymer composites
• nanocomposite foams
• segregated structure
• gradient cells
• emi shielding