Electromagnetic properties and performance of exfoliated graphite (EG) - Thermoplastic polyurethane (TPU) nanocomposites at microwaves

Nanocomposite materials based on commercial thermoplastic polyurethane (TPU) loaded with exfoliated graphite (EG) in concentration between 0 and 20 wt.% have been prepared with EG via melt mixing and compression molding. The materials' electromagnetic properties have been measured with wave-guide technique between 8.2 and 12.3 GHz. They had shown a clear proportional dependence of complex permittivity with EG content. Above 16 wt.% permittivity becomes frequency dependent. These results are discussed in view of material microstructure by means of scanning electron microscope (SEM) observations. Samples, with 20 wt.% EG and 4 mm thick, show an average value of 20 dB of shielding effectiveness (SE), which make them suitable as shielding material for commercial application. Simulations of metal backed configuration showed that important narrowband EM absorption (>-15 dB) can be achieved at 1 mm thickness, while multilayer structures are necessary to obtain EM broadband absorption (>-10 dB between 8.5 and 12 GHz) can be achieved in 6 mm thick samples. (C) 2015 Elsevier Ltd. All rights reserved.