The process of carbon black dispersion refers to the formation of a rubber containing high concentration of carbon black after wetting, which is dispersed under the action of ultrasonic cavitation force and becomes smaller agglomerates. This agglomerate is a primary structure that is dispersed throughout the entire rubber material, forming a bonded rubber with the rubber. During the mixing process, rubber molecules break chains and generate large molecule free radicals that can bind to the active sites on the surface of carbon black particles, as well as to the newly formed surfaces with higher activity generated by the rubbing of carbon black aggregates during mixing. Alternatively, rubber that has already been bound to carbon black can be further entangled or crosslinked to form a product that is insoluble in rubber solvents, known as bound rubber.[1]

Combining the generation of rubber helps to disperse the particles of the compounding agent, which is beneficial for improving the performance of rubber. The production and quantity of rubber are related to the properties of rubber and compounding agents, as well as the mixing process conditions. Rubber has high unsaturation, high activity, and is prone to forming bonded rubber; The particle size of the compounding agent is small, the structure is high, the surface activity is high, and it is easy to generate bound rubber; The higher the mixing temperature, the easier it is to generate bonded rubber. So, for many low unsaturation rubbers such as butyl rubber and ethylene propylene rubber mixed with carbon black, high mixing temperature can be used to increase the amount of bound rubber. However, for high unsaturated rubber such as natural rubber and polybutadiene rubber, the mixing temperature should not be too high because the combined rubber gradually increases at the initial stage of mixing, otherwise many carbon black gel hard particles combined with rubber will be generated at a time, which will be difficult to further disperse.