Contents I. Introduction
The advent of carbon nanotubes (CNTs) and recent studies in polymer–CNT composites [1] has motivated study of their use for electromagnetic interference (EMI) applications as lightweight, high shielding efficiency materials. At the very outset, in EMI shielding, the effects of both reflection and absorption of the incident EM radiation have to be considered [2]. The intensity of the reflected radiation () is related to the difference of the characteristic impedances () of the incident medium (i.e., air of impedance ) and the material () through . The absorption () is quantified through the skin depth (), the extent to which the radiation, of frequency f, penetrates the material through , where is the magnetic permeability and the electrical conductivity. Consequently, while metallic materials (with low and high ) are obviously efficient shielding materials, issues such as cost and bulk preclude their wide-scale application. Such issues have encouraged the use of polymers where the intrinsic poor conductivity could be compensated through the use of filler materials that form a conducting network. (It is to be noted that electrically conducting polymers are currently expensive, difficult to process, and need considerable improvement in their mechanical properties [3].)
