ELECTRICAL AND MECHANICAL-PROPERTIES OF ELECTRICALLY CONDUCTIVE POLYETHERSULFONE COMPOSITES

Electrically conductive polyethersulphone (PES) composites containing carbon fibres, nickel fibres, stainless steel fibres or aluminium flakes at various volume fractions up to 40% were fabricated and tested. For electromagnetic interference (EMI) shielding effectiveness > 50 dB, the minimum filler volume fraction was 40% for carbon fibres of length 200 or 400 mu m, 20% for nickel or stainless steel fibres, and 30% for aluminium flakes. The tensile strength first increased and then decreased with increasing filler content, such that the highest tensile strength occurred at 30 volume% (vol%) for carbon fibres (of length 200 or 400 mu m) as the filler and at 10 vol% for nickel or stainless steel fibres. However, for carbon fibres (of length 100 mu m) and aluminium flakes, the tensile strength increases up to at least 40 vol%. The best overall performance was provided by aluminium flakes at 40 vol%; the resistivity was 7 x 10(-5) Omega cm, the EMI Shielding effectiveness was > 50 dB and tensile strength was 67 MPa. The resistivity of the aluminium flake composites was not affected by heating in air at 140 degrees C for up to at least 144 h.