High frequency electromagnetic interference shielding response of mixtures and multilayer films based on conducting polymers

The electromagnetic interference (EMI) shielding efficiency (SE) is measured for conductive polyaniline and its mixtures containing conducting powders. The frequency ranges of the EMI SE is 10 MHz–1 GHz by using the ASTM D4935-89 technique. The EMI SE of hydrochloric acid doped polyaniline containing silver (Ag) powder is ∼46 dB at room temperature, which indicates that the materials can be commercially applied to shielding against electromagnetic (EM) radiation. The theoretical SE is calculated by using measured dc conductivity, which is compared to the experimental data. We observe that the SE increases with increasing dc conductivity. A model to account for the increase of the SE through the chemical doping and mixing process is presented. The theory for the calculation of the EMI SE of multilayer films based on conducting polymers is discussed in terms of boundary conditions for electric and magnetic fields of EM plane waves. The high frequency (⩾300 MHz) EMI shielding response of the monolayer and mu...