Superior electromagnetic interference shielding and dielectric properties of carbon nanotube composites through the use of high aspect ratio CNTs and three-roll milling

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• Highly entangled CNTs are separated and dispersed in the polymer through the use of three-roll milling techniques.
• High aspect ratio CNTs and an effective fabrication process enable a superior EMI shielding efficiency (SE).
• Increased permittivity of the CNT composites can be attributed to the formation of a robust resistor–capacitor network.

We report superior electromagnetic interference shielding and dielectric properties of carbon nanotube (CNT) composites achieved through the use of high aspect ratio CNTs and three-roll milling. Highly entangled CNTs are separated and then evenly dispersed within the polymer matrix using three horizontally positioned rotating rolls that apply a strong shear force to the composite. Very high aspect ratio CNTs combined with an effective fabrication process result in a low percolation threshold (∼0.06 vol%) and excellent electromagnetic interference (EMI) shielding efficiency (SE). The achieved SE is one of highest ever reported for the given CNT loading and measurement conditions. A model consisting of a network of resistors and capacitors formed within the nanocomposite was used to describe the microwave properties of the multi-walled carbon nanotubes/polydimethylsiloxane composites (MWNT/PDMS). Enhancement of this network is attained through the use of high aspect ratio CNTs and a fabrication process that evenly disperses and randomly orients this filler within the PDMS.