Conductive principle of conductive carbon black and factors affecting the conductivity of carbon black?

Conductive carbon black conductive principle:

1. The carbon black particles are connected to each other to form a chain, and the conduction phenomenon is generated by the movement of the chain atoms. This is the conduction channel theory.

2. In addition to the contact between particles, but also due to the electron conduction generated by the migration of electrons in the gaps of carbon black particles dispersed in the matrix, which is called the tunnel effect theory. Or the emission current is generated due to the high-intensity electric field between the carbon particles, which is the so-called electric field emission theory.

Factors affecting the conductivity of carbon black:

1. Carbon black particle size Theoretically, the smaller the particle size of carbon black, the more particles per unit volume, which is beneficial to improve the electrical conductivity. This is normal in rubber products. However, when used in conductive plastic products, if the carbon black particles are too small, the dispersibility is poor due to the small shear force after plastic plasticization. The performance is reduced and the practical value is lost. Therefore, it is necessary to control the particle size of carbon black within a certain range to ensure that carbon black can not only obtain good dispersion in plastics, but also greatly increase the number of carbon black particles per unit volume, improve the electrical conductivity of plastic products, and at the same time not Destroy or less damage the mechanical properties of plastic products.

2. The size of the DBP value of the carbon black structure represents the level of the carbon black aggregate structure. Generally speaking, when the DBP value is high, the carbon black presents a chain branched structure, and the electrical conductivity is better. The DBP values of carbon blacks, by-products of various heavy oil and gas production, are very high, and they are found to be hollow shell microstructures from electron microscopy, indicating that their structures are not very high. Its high electrical conductivity may be due to the larger volume per unit mass, and the shearing destroys part of the primary structure, resulting in a large number of new particles. In order to obtain good electrical conductivity in plastics, carbon black must have a large particle size, and the structure should not be too high. It is best to make the structure of carbon black into a linear structure. On the one hand, it can promote the dispersion of carbon black in plastics, and on the other hand, it is conducive to the formation of a conductive network, and a small amount of carbon black can achieve electrical conductivity.

3. Roughness of carbon black Because the electrical conductivity of carbon black requires a certain roughness, so that the carbon black forms a conductive channel, so the difference between the nitrogen adsorption surface area of carbon black and the surface area of CTAB is required to be large.

4. Surface volatile matter The volatile matter on the surface of carbon black is mainly composed of some organic groups and the oil film that has not been completely cracked to form an insulating layer, which increases the potential barrier between carbon black particles and seriously affects the conductivity. Control the volatile content in a low range.

5. Ash and moisture The high ash and moisture content of carbon black actually reduces the content of carbon black, which also has an adverse effect on electrical conductivity. Attention should be paid to controlling the content of ash and moisture in carbon black during production.