1. Particle Size

The particle size of carbon black refers to the primary particle size of carbon black, which is measured by electron microscopy and is the average of a certain number of particle sizes.

2. Tinting strength

Tinting strength refers to the coloring ability of carbon black when white or colored pigments are mixed with it. That is to say, the degree to which carbon black enhances the light absorption of the mixture system. It is usually expressed in percentage form and can be measured by using a blackness reflectometer to measure the data obtained from carbon black diluted paste.

3. Surface area

The surface area of carbon black refers to the total surface area of carbon black particles per unit mass or volume, measured in m2/g. Specific surface area, like particle size, is one of the fundamental properties of carbon black. Generally speaking, the specific surface area of relatively smooth carbon black (such as rubber carbon black) is inversely proportional to the particle size, meaning that the smaller the particle size, the larger the specific surface area, and vice versa. So, if carbon black particles are assumed to be spherical, the specific surface area can be calculated from the particle size data.  

The specific surface area of carbon black is divided into external specific surface area (also known as smooth specific surface area), internal specific surface area (also known as pore specific surface area), and total specific surface area. The total specific surface area is equal to the sum of the external specific surface area and the internal specific surface area. There are many methods for measuring specific surface area, including nitrogen adsorption method (BET method), iodine adsorption value method, CTAB method, t-value method and electron microscopy method.

4. DBP absorption value

The structure of carbon black can be measured by the DBP (dibutyl phthalate) absorption value. Based on experience, the DBP absorption value per 100g of low structure pigment carbon black should not exceed 70ml; In high structured pigment carbon black, the DBP absorption value per 100g of carbon black should not be less than 110ml. Medium structured carbon black falls between the two. The structure has a substantial impact on the applicability of pigment carbon black.

5. PH value

The pH value is related to the number of surface functional groups. The surface functional groups of furnace carbon black are few, and there are a small amount of soluble salts, so the carbon black itself is mostly neutral or alkaline. In order to improve the viscosity, stability, and fluidity of carbon black, some pigment carbon black can change the number of surface functional groups through surface treatment, thus becoming acidic.

The specific surface area and structure of carbon black have an impact on its application performance. The following is the relationship between surface area and structure and the performance of carbon black.