Electromagnetic interference shielding efficiency of polyaniline mixtures and multilayer films

Electromagnetic interference shielding efficiency (SE) of the mixtures of polyaniline(PAN) and: conducting powders such as silver (Ag), graphite, and carbon black is measured in the frequency range from 10 MHz to 1 GHz by using ASTM D4935-89 technique. The measured SEs of the mixtures are from 20 dB to 50 dB, which agree with theoretical values obtained from a good-conductor approximation. The SEs of the system increase with increasing DC conductivity. For the mixture of emeraldine base form of PAN and Ag powder doped with hydrochloric acid, the SE is similar to 46 dB with similar to 70 mu m thickness. Chemical doping in PAN mixture samples induces the increase of the SE. The model accounting for the increase of the SE in the mixture system is discussed. The effects of multilayer of PAN on the SE are presented.