Absorption and Shielding Effect of Electromagnetic Wave at GHz Frequency by Multi-walled Carbon Nanotube/Polymer Composites

The complex permittivity at 5.8 GHz of the composites of epoxy resin with multi-walled carbon nanotubes (MWCNTs) with their 20-70 nm diameters and 10-20 mum lengths at the concentration of 0.1-0.5% in weight was measured using a waveguide in order to develop the electromagnetic wave absorber (EMA) in the GHz frequency region. The EM absorbing efficiency was the highest at the MWCNT concentration of 0.2%, although the electric resistivity of the composite decreased and the electromagnetic interference shielding efficiency at 1-18 GHz increased with concentration of MWCNT over 0.5%. Such was observed even in various polymers including polycarbonate, polyacetal, polystyrene, acrylonitrile-butadiene-styrene copolymer, polymethylmethacrylate, and poly-etheretherketone