THE ELECTRICAL CONDUCTANCE OF CARBON BLACK

Abstract : The electrical properties of elastomers and plastics are significantly affected by the presence of the conductive reinforcing carbon black particles. A study of the resistance of carbon black indicates that the relation between logarithm of resistance and cube root of specific volume is linear over the entire range investigated. Most lines intersect by extrapolation in a single point, corresponding to an open packing at the resistance of solid carbon, independent of the presence of particle chains. These results are incompatible with a through-going path concept of electrical conductance. It is shown that field emission and electron tunneling through gaps accounts quantitatively for the observed phenomena. The influence of particle size, porosity and structure as well as the effect of surface oxygen complexes of the blacks has been assessed. It appears that the presence of carboxyl groups on the carbon black surface imparts a high electrical resistance to a vulcanizate. Chemical modification of the carbon black surface may lead to highly electrically insulating and completely water-resistant vulcanizates. (Author)