Shielding electromagnetic radiation

Percolation networks of metal-coated, conductive synthetic fibres were incorporated in polymer matrices of polypropylene (PP) and acrylonitrile-styrene-acrylic ester (ASA). Needlepunched nonwovens specially produced for this purpose from acrylic fibres were chemically coated with Ni or physically coated with Cu or Ag. The electrical conductivity of these textile structures was retained after hot press lamination with PP and ASA matrix films and also after incorporation in PP by injection moulding. Conductive composite structures with a metallised acrylic fibre content of between 7 5 and 9 wt.-% and a sample thickness of 3mm had shielding attenuation values of between 50 and 65dB at frequencies of 50 to 1000MHz (far field). This shielding performance was superior to that of a steel-fibre-filled PP material with a 10% fibre content of the same sample thickness.