Electrical conductivity of polymers containing carbon black

Abstract

Abstract Changes in volume resistivity with temperature of carbon‐black‐filled polymers and a random copolymer of styrene and butyl methacrylate were measured. For polystyrene containing 20 wt % carbon black, of surface area 24 m 2 /g, the resistivity changes abruptly from 10 13 to 10 6 ohm‐cm above 150°C. Poly(butyl methacrylate) did not show well‐defined changes in resistivity on heating. The random copolymer containing 16.7 or 28.6 wt % carbon black, of surface area 24 m 2 /g, showed a resistivity exceeding 10 13 ohm‐cm, that decreased to about 10 7 ohm‐cm on heating above 120°C. This Copolymer containing 16.7 wt % carbon black, of surface area 625 m 2 /g, shows a resistivity of about 108 ohm‐cm that decreases sharply to 10 3 ohm‐cm by 150°C. Decreases in resistivity on increasing the temperature in the quiescent state are correlated with the observation of a yield stress at low shear rates in rheological studies. It is suggested that carbon black agglomerates at elevated temperature and forms an independent conductive network that prevents flow.