Microstructure–conductivity relationship in conducting polypyrrole/epoxy composites

Four dispersing methods were used to disperse increasing amounts of Polypyrrole (PPy), synthesized either via dispersion (PPyd) or suspension polymerization (PPys), in an insulating epoxy matrix in order to make it electrically conductive. As shown in SEM micrographs and by the physical characteristics, PPyd particles exhibit higher density and smaller particle size than PPys. In addition, optical micrographs of the blends show that PPyd form compact agglomerates and PPys aerated clusters. It is deduced from conductivity measurements, that energy intensive methods or larger particle size (PPys) provide low percolation threshold, indeed, energy intensive methods, by breaking the PPyd agglomerates, favour the formation of conductive network of fine particles and therefore lower the PPy concentration at percolation. Similarly, larger PPys particles are arranged in clusters allowing a more homogeneous distribution of PPy particles in the resin and a smaller percolation threshold. The microstructure of the blends are observed by TEM. (C) 1998 Elsevier Science Ltd. All rights reserved.