Intrinsically conducting nanocomposites: high performance electromagnetic shielding materials

The new ways of processing intrinsically conducting polymers as polyaniline (PANI) permits to conceive nano-composites with high conductivities. The blends of PANI with polyurethane showed a very low percolation threshold (<1%) and the dielectric properties can be tuned easily and precisely with the mass fraction of PANI in the blends. The performances of the materials in term of electromagnetic shielding (SE) were evaluated on a wide range of frequencies (50 MHz-100 GHz). Electromagnetic shielding effectiveness from 30 to 90 dB were found for mono or multi layer samples in the X and Ku band. From the measured physical properties (conductivity, permittivity) of the materials used as a data base, the genetic algorithm permits to optimize the electromagnetic shielding effectiveness to obtain very lightweight materials with a thickness below one millimeter with a SE superior to 40 dB in the 50 MHz-100 GHz band. By optimizing the materials for a desired value of shielding effectiveness, the quantity of PANI in the blends is reduced and then their mechanical properties are nearly those of the polyurethane. An other important advantage for industrial applications is a reduction of the cost of production of the materials.