Electrical properties of exfoliated‐graphite filled polyester based composites

Abstract Work has been done to develop and optimize a procedure for the preparation of electrically conductive exfoliated‐graphite filled unsaturated polyester composites. The exfoliated graphite flakes impart excellent electrical properties to the polyester composite. EMI (electromagnetic interference) shielding effectiveness, comparable to that of exfoliated graphite alone, has been observed over a frequency range of 0 to 1000 MHz with composite samples containing as little as 4 weight percent of exfoliated graphite. The resistivities approached the value for exfoliated graphite in the c‐direction (0.03 μ‐cm) at a graphite loading of 11 weight percent. It has been observed that the mechanical integrity of the composite remained good up to graphite loadings of some 17 weight percent. The polyester readily wets the graphite and penetrates most of the graphite open pore volume during processing. Flow visualization measurements have been made in a transparent compression molding apparatus. No effect of the flow conditions on the apparent electrical properties has been found.