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 films were prepared by the variation of dopant loading and solvent types．When dopant camphor sulphonic acid／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)．The 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．The total shielding efficiency(SET) of highly conducting polyaniline films was measured at 10 GHz of microwave frequency．The dependence of SET on thickness of polyaniline films was studied．When the thickness of the film is l8 μm

the calculated SET is up to 40 dB．The SET result shows that the electromagnetic shielding property of highly conducting PANl film can meet the desire of commercial standard．Electromagnetic shielding efficiencies of films with different thickness are calculated by the far-field shielding theory．The practical measured SET values are compared with the calculated values．It is found that the measured SET values are very consistent with the theoretically calculated ones．