What is the relationship between particle size and specific surface area in pigments?

Definition

1. What is pigment particle size: Pigment Particle Size refers to the volume size or dimension of a pigment particle. Pigment particles can be tiny particles and their sizes are usually measured in micrometers (μm) or nanometers (nm).

2. What is specific surface area: It is the surface area per unit mass or per unit volume of the pigment. In simple terms, it is the ratio of the total surface area of a pigment particle to its mass or volume.

Pic# A

Relationships between particle size and specific surface area in pigments?

1. The effect of particle size on specific surface area. (See Pic#A)

1-1. As the size of a pigment particle decreases, its surface area increases. This is because the surface area of a particle is calculated from its surface area integral, and the smaller the particle, the greater the result of the surface area integral.

The smaller the particle, the greater the result of the surface area integration. On the other hand, as the size of the pigment particle increases, its surface area decreases.

2. The importance of specific surface area:

2-1. Specific surface area is an important index to measure the surface activity and reactivity of pigment. The larger the specific surface area is, the higher the surface activity and reactivity of the pigment is.

2-2. In practical application, the size of specific surface area affects the pigment's coloring power, covering power, light resistance, weather resistance and other properties.

What kind of important role does the relationship between specific surface area and particles play in Technical Data Sheet of pigments?

In fact, the relationship between specific surface area and particles mainly affects the index of oil absorption. Oil absorption, to a certain extent, can tell us how big the specific surface area of the pigment is. Specific surface area is like the “skin area” of the pigment. If the particles of the pigment are very small, then its “skin area” will be larger, and more oil needs to be infiltrated, so the oil absorption will be higher. On the other hand, if the pigment particles are very large, the “skin area” will be small, the oil needed will be less, and the oil absorption will be low.

Actual Cases from iSuoChem Effect Pigments：

1. Organic pigment. In this products, we usually use oil absorption in TDS. Like Pigment yellow PY 83, its oil absorption is 40-50 ml/100g.

2. Pearlescent pigment. Pearl pigment also uses oil absorption to tell the customers whether this code is what they need. Like AS300 Gold luster pearl pigment, its oil absorption is 70-90 g oil/100g powder.