Effect of low‐content carbon nanotubes on the dielectric and microwave absorption properties of graphite/polymer nanocomposites

Abstract

ABSTRACTHoneycomb cores (HCs) coated with graphite and multiwalled carbon nanotubes (MWCNTs) filled in a thermoplastic resin are proposed as microwave absorbers. The MWCNT contents varied from 0.2 to 0.6 wt % in a graphite‐filled (15 wt %) thermoplastic resin. The HCs were coated with three different types of coating materials for the sake of comparison: graphite, MWCNTs, and graphite plus MWCNTs. The dielectric properties [the real and imaginary parts of complex permittivity (ε′ and ε″, respectively)] and reflection loss (RL) of all of the coated HCs were measured and compared. We observed that the permittivities and RL increased significantly with increased weight percentage of the MWCNTs in the graphite‐filled thermoplastic resin. The RL measurements showed a maximum loss of −20 dB around 7 GHz and a bandwidth of 2.7 GHz at −10 dB in the HCs coated with the 0.4 wt % MWCNT plus graphite. There was also a shift in the RL peak position from the x band to the c band after the increase of MWCNT content. We also observed from the measurements that a combination of graphite and MWCNTs resulted in a broadband microwave absorber; a bandwidth of 13 GHz was observed for 80% RL when the MWCNT content increased to 0.6 wt % in the graphite‐incorporated resin. The possible mechanism that increased RL with the incorporation of MWCNTs in the graphite‐mixed thermoplastic resin is discussed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40891.