Tinting Strength
Also known as coloring power, it refers to the coloring ability of carbon black when mixed with white or colored pigments. It is the degree to which carbon black increases the light absorption of the mixture. It is usually expressed as a percentage and can be measured by using a reflectometer to measure the data obtained from diluting carbon black ink. According to industrial standards, the ink is a mixture of carbon black, titanium dioxide (or other white pigments such as zinc oxide), and certain solvents. (The measurement of tinting strength refers to ASTM D-3849 or GB/T 7050-2003 standard).
Specific Surface Area
The specific surface area of carbon black refers to the total surface area of carbon black particles per unit mass or unit volume, expressed in m2/g. Like particle size, specific surface area is one of the basic properties of carbon black. Generally, the specific surface area of carbon black with relatively smooth surface (such as rubber-grade carbon black) is inversely proportional to the particle size, that is, the smaller the particle size, the larger the specific surface area, and vice versa. Therefore, assuming that carbon black particles are spherical, the specific surface area can be calculated from particle size data.
The specific surface area of carbon black is divided into external specific surface area (or smooth specific surface area), internal specific surface area (or pore specific surface area), and total specific surface area. The total specific surface area is the sum of the external and internal specific surface areas. There are many methods for determining specific surface area, commonly used methods include nitrogen adsorption (BET), iodine adsorption, CTAB (cetyltrimethylammonium bromide) method (polymer adsorption method), t-value method, and electron microscopy method.
DBP Absorption Value
The structure of carbon black can be measured by DBP (Dibutyl Phthalate) absorption value. According to experience, the DBP absorption value of low-structure pigment carbon black should not be higher than 70 ml per 100 g of carbon black, while that of high-structure pigment carbon black should not be lower than 110 ml per 100 g of carbon black. Medium-structure carbon black is between the two. The structure has a substantial impact on the applicability of pigment carbon black. (The measurement of oil absorption value refers to ASTM D-2414 or GB/T 7046-2003 standard).
pH Value
The pH value is related to the number of surface functional groups. Furnace black has few surface functional groups and a small amount of soluble salts, so carbon black itself is mostly neutral or alkaline. In order to improve the viscosity, stability, and fluidity of carbon black, some pigment carbon blacks can be surface-treated to change the number of surface functional groups, thus becoming acidic. (The measurement of pH value refers to GB/T 7045 standard).