Dispersion technology-Core of Specialty Carbon Blacks application.
Pigment Carbon Black is an excellent and most widely applied black pigment. However, in practical application, it is often complained by customers for not corresponding to the expected quality, resulting in various problems in production. Besides problems with prime choice of carbon black, it’s more likely that customers merely concentrate on the blackness, and ignore a more important factor- dispersion of carbon black.
1. Dispersion of carbon black The definition of dispersion is quite simple, which refers to the process that the agglomeration body of carbon black is grinded or smashed (dispersed) into required grain size through dispersing equipment.
2. Significance of carbon black dispersion The degree of dispersion directly decides the performance of carbon black pigment. Carbon black cannot be applied without dispersing, due to the lack of pigment nature. Different dispersing grain size will lead to great discrepancy in finial using effects, even of the same carbon black product. Since the applied situation varies from each other, it’s very important for customers to ensure the dispersing process in the laboratory during the specific application.
3. Dispersing process of carbon black Dispersion of carbon black mainly includes: wetting; dispersing;stablizing.
Wetting—it uses grand mass to replace the air on the surface of carbon black or that among the aggregation, facilitating the next step of separation process. The difficulty of wetting depends on the surface tension of grand mass or carbon black. Failure in wetting would seriously affect the following separation process, thus wetting process should arouse enough attention in carbon black application.
Dispersing— as the main process in separation, uses mechanical equipments to put shear force on carbon black mixed with grand mass, shearing and separating it into fine particles. Choice of dispersing equipments, decision of dispersing process condition and choice of grand mass all have a great influence on shear force.
Stablizing— Specialty Carbon Blacks possesses infinitely small particle size and extremely big superficial area. It produces great surface energy after dispersing, having a strong re-flocculation (back to pig shin) tendency. By clinging to the surface of carbon clack, the dispersing agent can weaken the surface tension between carbon black and connection material, promoting carbon black to be sufficiently wetted by connection material. Meanwhile, charge repulsion between opposing ion groups carried by dispersing agent, and steric hindrance effect can prevent carbon black from returning into shin through re-flocculation.