Carbon Blacks for Highly Conductive Rubber

Abstract

Abstract The mechanism of the conductance of the electric current through a carbon black dispersion is still a problem which has not been completely solved. Rubber is an insulator and forms a homogeneous liquid phase, while carbon black is a semi-conductor and forms a dispersible solid phase. Mixtures of these two show electrical properties ranging from a near insulator to a near semiconductor. The picture which has been generally accepted for the mechanism of conductivity in rubber-carbon black compounds is one based on through-going paths of carbon black particles. These through-going paths are formed by carbon black particles either touching or situated so close to adjoining carbon black particles that the electrons have a reasonable chance to jump across the gap. This concept implies that each carbon particle must practically touch its neighbor or else the continuous chain will be broken. The definition of “touching” is not given in this concept. The number of conducting or through-going paths will be a function of loading and the particle size of the carbon black. In addition to the number of the paths, the intrinsic conductivity of the carbon blacks themselves, which is mainly a contact resistance, is of paramount importance. This picture is useful only if it is consistent with the various characteristics of electrically conductive rubber-carbon black compounds.