Electrically conductive thermosetting resins containing low concentrationsof carbon black

A cured vinyl ester resin containing electrically conductive carbon black ( CB)particles shows electrical percolation at very low CB concentration (<0. 5 phr). CB particles have a strong tendency to agglomerate in a low-viscosi ty resin, such as vinyl ester, unsaturated polyester resin, and epoxy resin s. The agglomeration process in the low-viscosity vinyl ester resin generat es electrically conductive paths already in the resin's liquid state, which undergo partial fixation by room temperature curing and full fixation by h ot postcuring. The fully cured castings containing CB concentrations above percolation are characterized by a constant, temperature-independent conduc tivity, over a wide temperature range. The current-voltage relationships of the cured vinyl ester/CB castings obey a power-law dependency. The presenc e of the continuous CB paths in the vinyl ester casting is clearly observed in fracture surfaces formed at 100 degrees C. (C) 2000 John Wiley & Sons, Inc.