Inorganic residues of refractory material, rust and metal particles from the process, and coke particles (“grit”) formed during the carbon black synthesis are frequent sources of solid contaminants in carbon black. Even low levels of grit can have a significant deleterious effect on dynamic applications such as many filled rubber compounds. Metal impurities and anion impurities like halogenides, sulfates, nitrates, and phosphates are the most important impurities that occur in carbon black and could have an influence on the stability of the carbon black-filled polymer system.
Electrical and Thermal Conductivity
Carbon black materials are semiconducting with intrinsic electrical resistivity values between 101 and 10~2 ^ cm. For all carbon black types, the intrinsic electrical resistivity decreases with increasing applied pressure. A certain electrical resistivity level is usually achieved at lower volume density of the carbon black material the higher its structure is. Elevated resistivity values at high compression density observed for some of the carbon black materials could be explained by the microstructure or the high volatile content.
More details on this topic can be found in the ? Chap. 19, “Carbon Black for Electrically Conductive Polymer Applications”.
Typical Properties of Filler-Grade Carbon Blacks
Typical properties of furnace blacks used as polymer fillers are presented in Table 2.