Physical And Chemical Properties Of Carbon Black

Various carbon blacks differ mainly in surface area (or particle size), aggregate morphology, mass distribution of particles and aggregates, and chemical composition.
Surface area:
One of the important properties used to identify and classify carbon black. Surface area is measured using gas or liquid phase adsorption methods. The most classic determination method is the low-temperature nitrogen adsorption method (BET method). Since nitrogen molecules are relatively small and can enter the micropores of carbon black, the results measured by this method represent the total surface area of carbon black. In recent years, macromolecule adsorption methods (such as CTAB) have been successfully studied. Since macromolecules cannot enter micropores, the measurement results represent the outer surface area of carbon black, that is, the "smooth" surface area. Most rubber carbon blacks are non-porous, so the BET measurement results are consistent with the CTAB measurement results. For some pigments, carbon black is used. The difference between the two surface area measurements represents the roughness or porosity of the carbon black. Another measurement method, the iodine absorption method, is also widely used in production control and product classification. It is simple and fast, but the measurement results are affected by the degree of oxidation of the carbon black surface.
Structure:
The second important property of carbon black. The structure of carbon black depends on aggregate size, shape, and the number and average mass of particles per aggregate. These characteristics all affect the packing state of aggregates and the void volume of powders. Usually, the structure of carbon black is expressed by DBP (dibutyl phthalate, dibutyl phthalate) oil absorption value. The DBP value of carbon black after being compressed 4 times at 170MPa is customarily called the compression oil absorption value or 24M4DBP value. The compression oil absorption value more truly reflects the state of carbon black aggregates in the rubber compound.