RHEOLOGICAL PROPERTIES AND ELECTRIC-CONDU CTIVITY OF CARBON-BLACK REINFORCED COMPOSITES ON THE BASIS OF POLYETHYLENE AND PROPYLENE

Coagulation structure forms upon filling polypropylene and low density polyethylene with carbon black in a melt of composite at low content of filler (phi almost-equal-to 2 vol %). This structure is a spatial f rame of carbon black particles, separated by thin interlayers of polym er. As a result, flow limit appears, that is independent of the polyme r type. Increase in the concentration of filler at the percolation thr eshold phi(c), brings about the formation of condensation structure wi th the contacting particles of carbon black, resulting in an avalanche -like growth of electric conductivity of composite. Filler concentrati on phi(c), necessary for the appearance of condensation structure, dep ends on the type of polymer (5 vol % for PP and 9 vol % for LDPE), bec ause of the differences in polymer interaction with the surface of car bon black particles. On the strength of percolation model, the equatio n is suggested for the description of concentration dependence of elec tric conductivity. The model includes the parameters of concrete syste ms PP-carbon black and LDPE-carbon black, that describe, in particular , the interaction between polymer and carbon black.