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

Abstract

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 (∼0.06vol%) 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.