ELECTROMAGNETIC IMPULSE EMI SHIELDING

most studies of CPs for EMI shielding applications have envisioned this sort of blending within a non-conductive polymer matrix. As an example, many of these studies have, evaluated DC and AC conductivity and shielding of CPs as blends in such thermoplastic matrices as poly(vinyl chloride) (PVC), acrylonitrile-butadiene-styrene (ABS), poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET). 

As mentioned in an earlier chapter, two of the most well established test methods for EMI shielding effectiveness (EMI-SE) are the ASTM (American Society for Testing and Materials, Conshohocken, PA, USA) method ES 7-83 and the US military standard MIL-STD-462. Frequencies in the 1 KHz to 1 GHz region are most commonly used. However, the cavity perturbation technique and the network analyzer technique, both used for generic microwave measurements and discussed earlier in Chapter 12, can also be used to generate EMI-SE data. 

Naishadham [475] used the cavity perturbation technique to study the overall microwave characteristics, including EMI-SE, of the CPs poly(acetylene) (P(Ac)) and poly(p-phenylene-benzobisthiazole) (P(BT)), at 8.9 and 9.89 GHz, and continuously in the 2-20 GHz frequency region. Figs. 19-la.b.c summarize some of his results. 

Makela et al. [875] carried out detailed studies of the EMI-SE properties of 1 to 30 /im thick camphor-sulfonic-acid-doped P(ANi) films having conductivities in the 10 to 100 S/cm region. Measurements were carried out in the near-field with a dual chamber, and in the far-field using a transmission line method, in 0.1 MHz to 1 GHz region. A strong correlation with surface film resistivity was found. Multi-layered structures were found to enhance shielding considerably, up to 40 dB at 100 MHz to 1 GHz. Fig. 19-3 summarizes some of their results in the near and far field. 

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The military applications of CPs have been extensively investigated during the past 25 yr with dramatic results in the following areas electromagnetic impulse (EMI) shielding conductive coatings and composites for electrostatic discharge dissipation (ESD) or... 

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