Electric and electromagnetic shielding properties of highly conducting polyaniline films

Abstract

The increasing use of commercial, military, and scientific electrical products and electronic devices has raised the problem of electromagnetic interference (EMI), also called electromagnetic environmental pollution, so there is an increased interest in EMI shielding. By use of mechanical mixing doping method, highly conducting polyaniline (PANI) films were prepared by the variation of dopant (camphor sulphonic acid) loading and solvent types in this paper. When dopant/emeradine base repeat unit molar ratio is 0.5/1, the conductivity of doped PANI is maximum. The conductivity results show that using m-cresol as solvent is better than N-methyl-2-pyrrolidinone (NMP). Using such mechanical mixing doping method is better than other doping methods. It employs less solvent and less dopant. The maximum conductivity of the prepared films is up to 370 S/cm. Total shielding efficiency (SE/sub T/) of highly conducting polyaniline films was measured at 10 GHz of microwave frequency. Their dependence of SE/sub T/ on thickness of polyaniline films was studied. Shielding efficiencies (SE/sub T/) of PANI films were also measured in shielding room according to MIL-STD-285 standard in a different frequency. When the thickness of the film is 45 /spl mu/m, the measured SE/sub T/ is more than 40 dB. The SE/sub T/ result shows that the electromagnetic shielding property of highly conducting PANI film can meet the desire of commercial standard. Electromagnetic shielding efficiencies of different thickness films are calculated by far-field shielding theory. The practical measured SE/sub T/ values are compared with the calculated values. It is found that the measured SE/sub T/ values are very consistent with the theoretical calculated ones.