Designing of multiwalled carbon nanotubes reinforced polyurethane composites as electromagnetic interference shielding materials

Long length multiwalled carbon nanotubes (MWCNTs) were synthesized in-house by chemical vapor deposition and their reinforced polyurethane (PU) based composites were fabricated by solvent casting followed by compression moulding technique. Electromagnetic interference (EMI) shielding effectiveness of these composites was investigated in the frequency range of 8.2-12.4 GHz (X-band). The experimental results indicate that the EMI shielding effectiveness of the composites is achieved up to -41.6 dB at 10 wt.-% loading of MWCNT, indicating the usefulness of this material for EMI shielding in the X-band. The main reason for such a high improved shielding effectiveness has been attributed to the significant improvement in the electrical conductivity of the composites by 13 order of magnitude, i.e. from 10(-14) for pure PU to 7.9 Scm(-1) for MWCNT-PU composites. The mechanism of improvement in EMI shielding effectiveness is discussed by resolving their contribution in absorption and reflection loss. The experimental results were found in good agreement with theoretical correlations.