Electromagnetic interference shielding materials

J. A. Marins, B. G. Soares, H. S. Barud, and S. J. L. Ribeiro, Flexible magnetic membranes based on bacterial cellulose and its evalution as electromagnetic interference shielding material. Mater. Sci. Eng. C 33, 3994-4001 (2013). 

Electromagnetic interference shielding effectiveness of about 18 dB was achieved with 10 vol% MWCNT-PMMA film which was found to be primarily an EMI absorbing composite material. Figure 7.15 shows the variation of EMI shielding effectiveness due to reflection... 

D. D. L. Chung, Materials for Electromagnetic Interference Shielding. / Mater Eng Perform 2000,9,350-354. 

X. C. Tong, Advanced Materials and Design for Electromagnetic Interference Shielding, CRC Press Boca Raton, 2009. 

Antistatic additives are capable of modifying properties of plastics in such a way that they become antistatic, conductive, and/or improve electromagnetic interference shielding (EMI). Carbon fibers, conductive carbon powders, and other electrically conductive materials are used for this purpose. 

Hughes Aircraft, Graphite fibre reinforced silica matrix composite, UK Pat. Appl. GB2208076 A. Chung DDL, Materials for electromagnetic interference shielding, J Mater Eng Performance 9(2), 2000. 

Xiaoping Shui, Chung DDL, Submicron nickel filaments made by electroplating carbon filaments as a new filler material for electromagnetic interference shielding, J Electron Mater, 24(2), 107-113, 1995. 

Conductive polymer composites (CPC) exhibit a series of unique features, such as comparatively low room temperature resistivity, percolation phenomenon, resistivity sensitivity to temperature, pressure and gas, and nonlinear voltage-current relationship [1-5]. They found wide industrial applications in the fields of antistatic materials, self-regulating heaters, over-temperature protection devices, and electromagnetic interference shielding. Therefore, fundamental and applied studies of CPC are currently of great interest. 

Electromagnetic/radio-frequency interference shielding materials have to meet much lower demands in terms of overall electrical conductivity (typically 4-5 orders of magnitude lower than a silver-flake-filled adhesive). This means that cheaper conductive fillers can be employed, for example, silver-coated copper flake, nickel flake, and carbon black. Typically the adhesive has to form a compliant joint between two mating surfaces, and hence room temperature vulcanizing or heat-cure silicone is often a convenient choice of matrix material. 

Zhang H., Yan Q., Zheng W., He Z., and Yu Z., Tough graphene-polymer microcellular foams for electromagnetic interference shielding. ACS Applied Materials Interfaces 2011, 3, 918-924. 

Unlike many doped conductive polymers, the electrical conductivity of these polymers is environmentally stable. Exposure to air for two years and water for 80 days produces little change in the conductivity. Potential applications proposed for this type of polymer include use as a matrix for advanced composites, and in electromagnetic interference shielding and electrostatic dissipation materials. 

Chung DDL. Electromagnetic interference shielding effectiveness of carbon materials. Carbon 2001 39(2) 279-85. 

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