Lightweight and Compressible Expandable Polymer Microspheres/Silver Flakes Composites for High-efficiency Electromagnetic Interference Shielding

It is important to exploit high-efficiency electromagnetic shielding materials to eliminate electromagnetic interference (EMI) pollution in electronic equipment. Here, a lightweight and compressible EMI shielding composite was successfully fabricated via mixing expandable polymer microspheres (EPM) with silver flakes (AgF), followed by heating expansion in a close mold. The composites with only loading 2.57 vol% AgF exhibits a superb electrical conductivity (973.56 S/m), and its EMI SE is up to 100 dB when the thickness is 5 mm in the ultra-waveband of 8 - 40 GHz. The EPM were squeezed and bonded with each other, and the AgF powders were uniformly distributed among the interfaces of the EPM, which offers a segregated conductive network, low density
${\left(0.328 \mathrm{g} / \text{cm}^{3}\right.}$
at 2.57 vol% of AgF), and high mechanical strength. In particular, it can be concluded that the EPM/AgF composites have promising potential applications in the EMI shielding materials of advanced electronic equipment via near-field testing. The average NF-EMI of EPM/AgF-2.75vol% is up to 62.7 dB, which is better than that of copper foil in the 1–9 GHz frequency range. Owing to the high elastic resilience and compressibility, the composites are a promising multifunctional material for lightweight electromagnetic shielding material.