I. Average Primary Particle Size

The average primary particle size of pigment carbon black, often referred to simply as particle size, is one of its key indicators.The particle size of carbon black is largely determined by its production process. Among them, the furnace process produces carbon black with the widest range of primary particle sizes for pigment carbon black, for example, from 10 nanometers to 80 nanometers.The average primary particle size and particle size distribution fundamentally determine the properties of pigment carbon black, especially its blackness and tinting strength.

II. Structure

The degree of aggregation of the primary carbon black particles is generally referred to as structure. It is mainly divided into two categories:

• High-structure carbon black (highly aggregated carbon black)

• Low-structure carbon black (lowly aggregated carbon black)

Primary particles of pigment carbon black do not exist as isolated individual particles; they also form fused aggregates and agglomerates.The degree of aggregation of furnace-process carbon black can be adjusted by modifying the process parameters, whereas that of contact-process carbon black is difficult to control due to its open production process (requiring adjustment by experienced technicians).

III. Surface Activity

Carbon black is mainly composed of carbon, with a carbon content of approximately 90% to 99%, and also contains trace amounts of oxygen, hydrogen, nitrogen, sulfur, and other elements.

Surface activity of carbon black:

• For acidic carbon black: refers to the amount of oxygen-containing surface groups formed on the surface of carbon black particles, mainly carboxyl groups, phenolic hydroxyl groups, quinone groups, lactone groups, etc.

• For basic carbon black: refers to the basic oxides present on the carbon black surface.

These factors affect the physical and chemical properties of carbon black, such as wettability and dispersibility, catalytic activity, and electrochemical performance.