What are the basic properties of carbon black

The basic properties of carbon black mainly include particle size, structure and surface properties, which have an important influence on the process performance and reinforcement effect of rubber.

① The particle size of carbon black refers to the size of single particle carbon black or primary particles in aggregates. The average particle size of carbon black for rubber is generally between 11 and 500 nm. The smaller the particle size of carbon black, the larger the total surface area of carbon black particles per unit mass or unit volume (real volume), that is, the larger the specific surface area of carbon black, the larger the contact area between carbon black and rubber, and the active points in the same mass of carbon black. The more it is, the better the chemical bonding and physical adsorption of carbon black to rubber can be exerted, and the better the reinforcing effect of carbon black is. The particle size of carbon black is related to the manufacturing method and production conditions. For the oil furnace method, the higher the degree of oil atomization of carbon black raw materials, the higher the furnace temperature, the greater the air-oil ratio; the greater the airflow speed in the furnace, the generated carbon black particles. smaller. The determination methods of carbon black particle size are: electron microscopy, nitrogen adsorption method (BET method), iodine adsorption method, macromolecular adsorption method (including anionic surfactant OT method and cationic surfactant CTAB method).

②The structure of carbon black refers to the form of carbon black. When carbon black is generated in the high temperature region of incomplete combustion, the particles are chemically combined to form three-dimensional aggregates, that is, the primary structure of carbon black. The primary structure of carbon black is not easily damaged during the processing of rubber, and it is the smallest dispersion unit of carbon black in rubber. Two or more aggregates are agglomerated into loose-structured aggregates due to van der Waals forces, that is, the secondary structure of carbon black. The secondary structure of carbon black is easily damaged by mechanical shearing force during rubber processing. The structure of carbon black includes - secondary structure and secondary structure. The structure of carbon black refers to the degree of carbon black-substructure. The looser the structure of carbon black, the higher the structure, the more complex the shape, the more branches, the larger the internal void, and the more occluded rubber formed by combining with the rubber. The structure of carbon black is related to its production method and the raw materials used. Generally, the structure of thermal carbon black is lower than that of channel carbon black. The structure of carbon black from natural gas is higher than that of carbon black from aromatic oil. low sex. The determination method of carbon black structure can be used oil absorption value method. In the quantitative carbon black, adding appropriate dibutyl phthalate (DBP), the more DBP volume required to fill the carbon black voids, the higher the carbon black structure. high.

③ The surface properties of carbon black include surface roughness and surface chemical properties. Surface roughness refers to the existence of micropores of several nanometers to several nanometers on the surface of carbon black particles, which are generated by the erosion of carbon black by high-temperature oxidizing gas during the formation process. Because the micropores are small, rubber molecules cannot enter these micropores, so that the surface area for carbon black and rubber to have an effective effect is reduced, so the reinforcing effect is low. The surface roughness of carbon black is related to its manufacturing method. Generally, the surface roughness of the channel carbon black particles is the largest, and the surface roughness of the carbon black particles by the furnace method and the thermal cracking method is smaller and the surface is smoother. The surface roughness can be measured by an electron microscope method, a nitrogen adsorption method, or the like. The surface chemical properties of carbon black are related to the chemical composition of carbon black and the surface state of carbon black particles. Carbon black is mainly composed of carbon elements, with a carbon content of 90% to 99%, as well as a small amount of oxygen, hydrogen, nitrogen and sulfur and a small amount of volatile matter and ash. Carbon atoms are covalently bonded to form hexagonal layers, so carbon black has some aromatic properties. During the production and storage process of carbon black, due to oxidation, the surface contains oxygen-containing functional groups such as hydroxyl carboxyl group, lactone quinone group, and phenol group. In addition, there are a lot of free radicals on the surface of carbon black. These chemical properties make the surface of carbon black particles have a certain chemical activity. The greater the chemical activity, the more the number of bound rubbers, and the better the reinforcing effect of carbon black.