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How does carbon black impart electrical conductivity to polymeric systems?


Carbon black is more conductive than polymers, resins, or rubber. Addition of carbon black reduces the electrical resistivity by forming a conductive network through the polymeric matrix. Grades of carbon black have been developed to optimize conductivity at lower loadings while meeting all other critical performance requirements for conductive applications.
How does carbon black structure affect dispersion rate?


Higher structure carbon blacks are generally more easily dispersed than low structure carbon blacks of similar surface area. A high structure carbon black is one in which the aggregates are composed of many prime particles clustered together with considerable branching and chaining. As a result, the aggregates pack more poorly reducing the inter-aggregate attractive forces. Low structure carbon blacks are more compact, allowing closer packing and thus greater inter-aggregate attractive forces which makes dispersion more difficult. However, while more energy is necessary to disperse lower structure carbon blacks, their higher density allows them to "wet" or incorporate easier because there is less occluded air to displace.
How does carbon black structure affect gloss?


As a result of higher oil absorption (vehicle demand), high structure grades of carbon black detract from the gloss of a finished product to a greater extent than do low structure grades.
How does carbon black surface chemistry affect dispersion rate?


Some grades of carbon black are post treated to increase the amount of chemisorbed oxygen on their surfaces. In some end use applications, this improves the rate of dispersion by improving the rate of wetting. Dispersion stability of the carbon black also increases and product viscosity is reduced.
How does surface oxidation of carbon black affect electrical conductivity?


An oxidized carbon black is less electrically conductive than an unoxidized carbon black of the same surface area and structure. The reduction in electrical conductivity occurs because of the insulating nature of the chemisorbed surface oxygen groups.
How does the surface area of carbon black affect dispersion rate?


Higher surface area carbon blacks are more difficult to disperse than lower area carbon blacks of similar structure. This is due in part to the higher energy needed to "wet" or incorporate the higher surface area grades. Also, as the primary particles become smaller (surface area increases) there are more aggregates per unit weight of carbon black in a given volume. This results in smaller inter-aggregate distances and an increasing number of contact points which lead to greater attractive forces between aggregates.
How is carbon black made?


Ninety-five percent of all carbon black is made by the furnace process. The feedstock (oil) is injected into a high-temperature reactor where the hydrocarbon is cracked and dehydrogenated to form carbon with a quasi-graphitic microstructure. Carbon black is composed of very small primary particles, which fuse to form branched aggregates. Post reactor operations include beading the “fluffy” low density black for improved storage and handling. Grades optimized for plastics use special manufacturing technology for improved dispersion, cleanliness and other targeted critical properties to enhance performance for specific applications.
How is the size of a primary particle measured?


The primary particle sizes represent typical arithmetic mean diameters of a sufficient number of primary particles to characterize a particular grade. Diameters are determined from Transmission Electron Microscope measurements.
How is the size of the carbon black primary particle related to surface area?


Primary particle size is inversely proportional to surface area. For example, as the primary particle decreases in size the surface are increases.
How is the structure of carbon black measured?


The structure of carbon black is measured through an oil absorption process, called dibutylphthalate absorption (DBPA or DBP). Thus, high structure grades of carbon black are distinguished from low structure grades by their higher oil absorptions.