Enhancement of Electromagnetic Interference Shielding Efficiency of Polyaniline through Mixture and Chemical Doping

Abstract

Electromagnetic interference (EMI) shielding efficiency (SE) of undoped and doped polyanilines and their mixtures with silver (Ag), graphite, and carbon black powder are measured in the frequency range from 10 MHz to 1 GHz by using ASTM (D 4935–89) technique. The measured SEs of the systems are from 20 dB to 50 dB, which agrees with theoretical values obtained from a good-conductor approximation. The SE of the system increases with increasing dc conductivity. This implies that the SE can be controlled by the intrinsic properties such as conductivity and dielectric constant. For the mixture of emeraldine base (EB) form of polyaniline and Ag powder doped with hydrochloric acid (ES/Ag), the SE is ∼46 dB with 70 μm thickness, indicating the capability of commercial applications to EMI shielding. Chemical doping in polyaniline mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed.