In situ observation of electric field induced agglomeration of carbon black in epoxy resin

This letter reports on the influence of a static electric field applied by metal electrodes on the agglomeration process of carbon black (CB) in epoxy resin. The growth of dendrites from the anode into the material is observed in situ by optical transmission microscopy, A percolating network is seen to form, combined with a drastic reduction in the sample resistivity. This behavior can be explained by taking into account the electrostatic interaction of the charged CB particles. The final resistance for composites with a given CB content can be controlled within a range of several decades by varying the applied voltage and the curing temperature of the mixture. (C) 1998 American Institute of Physics.