ELECTRICAL CONDUCTIVITY OF RUBBER COMPOUNDS: REVISITING THE INFLUENCE OF FUNDAMENTAL CARBON BLACK PROPERTIES

ABSTRACT Carbon blacks are electrically conductive; however, when carbon black is used as particulate reinforcement in a rubber compound, the compound electrical conductivity can vary from insulative to fully conductive depending on the loading level and properties of the carbon black. An investigation of the influence of three fundamental properties of carbon black—particle size, structure, and porosity—on rubber compound electrical conductivity was conducted. The deconvolution of these three parameters within the study allows for conclusive results to be drawn on what drives compound electrical conductivity and the underlying principles. The work is split into two parts: (1) a determination of the influence of particle size and structure and (2) the influence of porosity. Particle size traces its influence back to the number particles that are in a given volume of rubber compound. Structure’s influence on electrical conductivity varies with the particle size of the carbon black and is for the first time traced back to the aspect ratio of the aggregates. Porosity is separated as a variable in this work by introducing discrete levels of porosity to nascent carbon blacks via gasification. The results show that the impact of carbon black porosity on electrical conductivity in rubber compounds arises from a change in its envelope density and is not due to any change in the inherent aggregate conductivity.