Composites of multi-walled carbon nanotubes and shape memory polyurethane for electromagnetic interference shielding

Multi-walled carbon nanotubes (MWCNTs) and shape memory polyurethane (SMP) were used to prepare MWCNT/SMP composites for electromagnetic interference (EMI) shielding. The uniform distribution of MWCNTs was confirmed by field emission scanning electron microscopy (SEM). The electrical conductivity of the composites was tested by the four-probe method, and the results suggested that the conductivity of the samples was significantly increased by the presence of MWCNTs. The conductivity reached 35 S/m when the MWCNT loading was 9 wt%. Dynamic mechanical analysis (DMA) revealed that the composites exhibited higher storage moduli than pure SMP. In addition, the shielding effectiveness (SE) of composites with various MWCNT loading and thickness were measured over 4-7 and 13-16 GHz. The highest SE achieved was close to 35 dB for MWCNT/SMP composites with the thickness of 2mm and MWCNT loading of 9 wt%. The SE increased as the thickness and conductivity of the composites increased. Moreover, the SE was enhanced as the frequency increased.