Electrically conducting graphene-based polyurethane nanocomposites for microwave shielding applications in the Ku band

Electrically conducting, thermally reduced graphene nanosheets (TRG) were synthesized through thermal exfoliation and subsequent annealing of graphene oxide at 800 A degrees C. Thermoplastic polyurethane (TPU)-based nanocomposites with different concentrations (ranging between 0 and 5.5 vol%) of TRG nanosheets were prepared by the solution blending method. Morphology, phase purity, and conducting properties of TPU and TPU/TRG nanocomposites were investigated through scanning electron microscopy, X-ray diffraction, conductive atomic force microscopy (C-AFM) and Raman spectroscopy. C-AFM images show the presence of electrically conducting TRG nanosheets embedded in the TPU matrix. Electromagnetic interference (EMI) shielding measurements were also undertaken on 2-mm-thick rectangular pellets. Shielding parameters such as shielding effectiveness, DC electrical conductivity, and dielectric properties, i.e., real and imaginary parts of permittivity were investigated. Our results show that the TPU/TRG nanocomposite at 5.5 vol% loading exhibits an enhanced electrical conductivity of the order of 3.1 x 10(-2) S/m and shows a superior EMI SE of similar to-26 to -32 dB in the Ku band frequency region. EMI shielding values were found to be dominated by the material's absorption behavior. The dielectric properties of TPU/TRG nanocomposites were also analyzed, and they demonstrate a good correlation with EMI shielding.