Shear rate effect on the resistivity of HIPS/LLDPE/carbon black extrudates

The effect of shear level on the structure and resultant resistivity of CB-containing high impact polystyrene/linear low density polyethylene (HIPS/LLDPE) extrudates produced by a capillary rheometer, as a function of blend composition and CB content, was studied. The data were compared with results obtained by various processing methods such as compression molding, extrusion, and injection molding. The conductivity of systems consisting of a single polymer matrix is more sensitive to shear rate than are those with HIPS/LLDPE matrices. Increased temperature tends to increase resistivity at high shear rates, and has practically no effect at low shear rates. Capillary entrance effects determine the CB structure and resultant resistivity of the extrudates. Apparently, the combined effects of CB location and flow-induced structuring may explain the enhanced conductivity of some of the extrudates.