Metals are recognized as electromagnetic interference (EMI) shielding materials owing to their high electrical conductivity. However, the need for light and flexible EMI shielding materials has emerged, owing to the heavyweight and inflexible nature of metals. Carbon nanotube (CNT)/polymer composites have been studied as promising flexible EMI shielding materials because of their lightweight nature due to the low density of CNTs and their high electrical conductivity. CNTs evenly dispersed in the polymer form an electrically conductive network, and the aspect ratio of the CNTs, which are one-dimensional nanofillers, is an important factor affecting electrical conductivity. In this study, we prepared three types of multi-walled carbon nanotubes (MWNTs) with different aspect ratios and fabricated polydimethylsiloxane (PDMS)/MWNT composites. Subsequently, the electrical conductivities and electrical percolation thresholds of the three PDMS/MWNT composites with different MWNT aspect ratios were measured to analyze the behavior of electrically conducting network formation according to the aspect ratio. Furthermore, the total EMI shielding effectiveness of each composite was determined to evaluate the effect of the MWNT aspect ratio on the EMI shielding. Reflection and absorption of electromagnetic wave were measured for the PDMS/MWNT composite with the largest aspect ratio to analyze the EMI shielding mechanism of the composite. Additionally, the effects of the MWNT content on the conductivity and EMI shielding performance were examined. The results provide valuable guidance for designing polymer MWNT composites with good electrical conductivity and EMI shielding performance under different aspect ratios of MWNTs.

Investigation of electromagnetic interference shielding effectiveness and electrical percolation of carbon nanotube polymer composites with various aspect ratios
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Fabrication of PDMSMWNT composites
        2.3 Electrical conductivity
        2.4 EMI shielding effectiveness
    3 Results and discussion
    4 Conclusion
    Acknowledgements 
    References

• Dong‑Kwan Lee(Department of Mechanical Engineering, Soongsil University, Seoul 06978, Republic of Korea)
• Jongchan Yoo(Department of Mechanical Engineering, Soongsil University, Seoul 06978, Republic of Korea)
• Hyunwoo Kim(Department of Mechanical Engineering, Soongsil University, Seoul 06978, Republic of Korea)
• Sung‑Hoon Park(Department of Mechanical Engineering, Soongsil University, Seoul 06978, Republic of Korea) Corresponding author