Polarized wave electromagnetic shielding of anisotropic carbon nanomodifier-based LLDPE composites

Abstract

The polarized wave electromagnetic shielding (EM SE) of nanocomposites containing 10 vol% of carbon nanomodifiers in a semicrystalline matrix is reported. Heat-treated carbon nanofibers, Pyrograf® III PR-19 heat treatment (HT) and multiwalled carbon nanotubes (MWNT) HT were dispersed in a linear low-density polyethylene matrix to produce flow-induced orientation of the nanomodifiers in the spun microfilaments. Consequently, the electrical conductivity of the resulting nanocomposites exhibited anisotropic behavior due to the nanomodifier orientation. The in-plane conductivity in the longitudinal direction (PR-19 HT comp.: ∼0.02 S/m; MWNT HT comp.: ∼3 S/m) was at least an order of magnitude higher than that along the transverse direction. As measured with a rectangular waveguide (WR510, 1.45–2.2 GHz), the PR-19 HT- and MWNT HT-oriented nanocomposites (1-mm thick) displayed EM SE values of 0.7 dB and 3.0 dB, respectively, when the nanomodifiers were transversely oriented with the polarized electric field. In contrast, when the orientation of the nanomodifiers was parallel with the field, EM SE values of 3.2 and 9.0 dB were obtained, respectively. The higher EM SE values are consistent with high conductivities observed in the direction of preferred orientation of the modifiers. POLYM. ENG. SCI., 55:299–307, 2015. © 2014 Society of Plastics Engineers