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Aggregate: what is a carbon black aggregate?


Aggregates are the smallest functional unit of carbon black. They are formed through the fusion of smaller units, called primary particles, into a three dimensional branched chain structure.
Carbon black: How is carbon black produced?


Ninety-five percent of all carbon black is made using 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 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 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.
Masstone: what is this?


Masstone is a measure of the blackness of a particular grade of carbon black.
Under what environment does carbon black decompose?


Typically, carbon black begins to decompose between 450 degrees C to 500 degrees C, under air or oxygen. Carbon black does not decompose at these temperatures under a nitrogen atmosphere. Ash testing of carbon black is typically done at 550 degrees C.
What is meant by the structure of carbon black?


Aggregates of carbon black are formed through the fusion of smaller units, called primary particles, into a three dimensional branched chain structure or cluster. This fusion can be controlled in the reactor to give varying degrees of clustering. Grades of carbon black in which the particles are allowed to cluster into relatively large, complex aggregates are known as high structure grades. Grades where the extent of aggregation is minimized are known as low structure grades.
What is the size of a carbon black aggregate?


Carbon black aggregate size is dependent on the grade of carbon black with each grade of carbon black having its own mean aggregate size. Mean aggregate sizes are generally in the range of 0.01- 1.0 microns.
Will carbon black pick up moisture?


Carbon black will pick up (adsorb) moisture up to an equilibrium absorption value. This value is generally stated as a wt% and thus will vary among the grades of carbon black depending on surface area and surface chemistry.