There are many factors that affect the dispersion of carbon black pigment . Among them, the particle size/specific surface area of carbon black pigment is one of the factors that affects the dispersion of carbon black, and it is also a very important one.
The primary particle diameter of carbon black pigment determines the dispersion of carbon black to a large extent. The reason is that the specific surface area plays a role. Although the primary particles have been fused into primary aggregates, their specific surface area is still a major factor.
The finer the primary particles, the higher the inherent specific surface area manifested in the primary aggregates.
Therefore, carbon black pigment with finer primary particles is more difficult to disperse than carbon black with coarse particles. The reason for this is that the larger the specific surface area, the higher the “wetting” energy required. Another important factor is: when the particles are finer, the number of aggregates per unit weight of carbon black in a certain volume of dispersion medium is greater. This results in smaller distances between aggregates, thus creating greater attractive forces between aggregates.
It should be noted that a side effect is that as the specific surface area increases (the primary particle size decreases), the amount of binder (solid resin) required also increases. When other properties are the same, fine particle carbon black has a higher oil absorption value than coarse particle carbon black. Higher, so the demand for connecting material per unit weight is greater.
When other conditions remain unchanged, the finer the particle shape of carbon black pigment, the higher its specific surface area, and the worse the dispersion of carbon black pigment , but the blackness is better. At this time, it is necessary to purchase granular carbon black pigment products with low specific surface area. Of course, other factors that affect the dispersion of carbon black can be changed to achieve high dispersion.
