Influence of composite electrical properties on the VHF-UHF electromagnetic shielding characteristics of polyethylene-carbon nanoparticle composites

The influence of composite electrical properties on the plane-wave electromagnetic shielding effectiveness (EM SE) of carbon nanoparticle/polyethylene nanocomposites is reported in the VHF and UHF bands (30 MHz-1.5 GHz). Two highly graphitic carbon nanoparticles (heat-treated Pyrograf® III PR-19 carbon nanofibers and CheapTubes® multi-walled carbon nanotubes) were dispersed in a linear low density polyethylene (LLDPE) matrix to produce a nominally random in-plane particle orientation. For a concentration of 10 vol% nanoparticles and a sample thickness of 2.5 mm, EM SE values of 24 dB and 22 dB were obtained for MWNT HT and PR-19 HT nanocomposites, respectively. At a high concentration of 40 vol%, EM SE values as high as 68 dB and 55 dB were obtained for the PR-19 HT and MWNT HT nanocomposites, respectively. Because such nanocomposites possess only moderate electrical conductivity, the composite permittivity was also used to predict the plane wave EM SE and its components. Based on the material properties of the nanocomposites, the predicted values of EM SE were found to be consistent with the experimental values.