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