Comments on "Shielding effectiveness of conductive polymers

The authors comment that K. Naishadham (see ibid., vol.34, no.1, p.47-50, 1992) calculated the plane-wave shielding effectiveness of conductive polymers as a function of frequency. As indicated, a comparison to the measured result of the DC conductivity indicates that the microwave conductivity at room temperature is within a small percentage of the DC result, and therefore can be used for a wide frequency range. The conductivity of the polymers is given by /spl sigma/=2/spl pi/f/sub 0//spl epsiv//sub 0//spl epsiv/" and is assumed invariant for all frequencies. Based on the invariability of polymers\´ conductivity for all frequencies, they calculated the shielding effectiveness of the polymers. Discrepancies are found by comparing these figures to those of Naishadham. It is concluded that shielding effectiveness calculated by Naishadham was done under the assumption of frequency-invariant /spl epsiv/" instead of /spl sigma/.