Factors affecting the conductive function of carbon black

1. Carbon black particle size:

In theory, the smaller the particle size of carbon black, the more particles it contains per unit volume, which is beneficial for improving conductivity. This is normal in conductive rubber products. However, when used in conductive plastic products, if the carbon black particles are too small, due to the low shear force after plastic plasticization, the looseness is poor. Carbon black exists in many small clumps in the base, which reduces the mechanical function of conductive plastic products and loses practical value. So it is necessary to control the particle size of carbon black within a certain range in order to ensure that carbon black can not only achieve obvious looseness in plastic molding, but also greatly increase the number of carbon black particles per unit volume in plastic molding, improve the conductivity function of plastic products, and together, not damage or minimize the original mechanical function of the products.

2. Carbon black structure:

The size of the DBP value represents the concavity and convexity of the aggregate structure of carbon black. Generally speaking, when the DBP value is high, carbon black exhibits a chain like structure and good conductivity. The DBP values of various by-products of heavy oil and gas production, carbon black, are very high. However, electron microscopy reveals that they have a hollow shell shaped microstructure, indicating that their structure is not very high. Its high conductivity may be due to either its larger volume per unit mass or shear damage to some primary structures, resulting in the formation of many new particles. To achieve good conductivity in plastic, it is necessary for carbon black to have a larger particle size and a structure that is not too high, so that the structure of carbon black becomes a linear structure. On the one hand, it can promote the looseness of carbon black in plastic, and on the other hand, it is conducive to forming a conductive network. A small amount of carbon black can achieve anti-static effect.

3. Carbon black roughness:

Due to the certain roughness required for the conductivity of carbon black, it is easy for carbon black to form conductive channels. Therefore, it is requested that the difference between the nitrogen absorption surface area of carbon black and the CTAB surface area is relatively large.

4. Surface transpiration fraction:

The transpiration fraction on the surface of carbon black is mainly composed of some organic groups and partially cracked oil films, forming an insulation layer that increases the potential barrier between carbon black particles and seriously affects conductivity. It is necessary to control the transpiration fraction within a lower limit.

5. Ash and moisture:

The high ash and moisture content in carbon black actually reduces the content of carbon black, which has a negative impact on conductivity. In production, attention should be paid to controlling the ash and moisture content in carbon black. In contrast, the carbon content of Ketjen BlackEC and acetylene carbon black is dominated by 9918%, while general carbon black is less than 98%. The moisture content should generally be controlled below 215%, otherwise many bubbles will occur, affecting the mechanical function of the product.

Article source: Taishan conductive mica particles

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