"Research Carbon Weng Says Carbon" (XV): Carbon Black, the Carbon Closest to Our Life

Seeing this title, some readers may have some questions: "You are mistaken, except that some heavily polluted cities may contain trace amounts of carbon black inhalable particles in the air and soot on the bottom of the cooking pot, where is there carbon black around us?".

In fact, carbon black does exist around us, but it has been changed. If you are writing with a non-aqueous and non-oily gel pen, there is in the ink in the pen; are you grinding ink to write and paint? Ingots contain; do you have books and newspapers with you? The printing of black ink on paper contains it. Do you have a printer? The toner in the printer cartridge contains it. Do you wear black rubber-soled shoes? The rubber soles contain it; you didn't think of it when you walked out and saw a torrent of cars, did you? Almost half of the car tires are carbon black. Therefore, carbon black can be said to be the carbon closest to human life today.

As early as the Han Dynasty more than 3000 years ago, our ancestors already used pine branches to burn smoke to make ink. The soot formed by incomplete combustion of pine branches is actually carbon black. Today, carbon black has grown into a mature industrial product. The world's output is nearly 10 million tons, and its production is the largest among all carbon materials, and the total output of other carbon materials is less than half of the carbon black output. According to the global 7 billion people, almost per capita consumption of more than 1kg. However, you should know that almost 90% of such a large amount of carbon black is used in the production of rubber products, especially in rubber for tires of automobiles and airplanes.

Because carbon black contains a large number of carbon atoms to form a hexagonal benzene ring, so it has excellent light absorption ability, its color is dark, since ancient times is the main raw material of black ink, the industrialization of carbon black is also in the 18th century in the United States with the printing industry's demand for ink developed. In 1910, after the United Kingdom discovered the reinforcing effect of carbon black on rubber, with the development of the automobile industry, it has become an indispensable basic raw material for industrial rubber products. As referred to in the carbon (X), carbon black is a black powder formed by incomplete combustion or thermal cracking of various gas phase or liquid phase carbohydrates (hydrocarbons) and carbonization in the gas phase. Carbon black was first developed by the tank method using natural gas as raw material, and furnace method and thermal cracking method appeared in the 1920 s. After the oil furnace method with liquid hydrocarbon as raw material was put into operation in the United States in 1943, this method has become the mainstream of carbon black production because of its high efficiency and good economic benefits.

After the liquid phase hydrocarbon (hydrocarbon, such as light oil) is not completely burned, the remaining carbon atoms will form polycyclic aromatic hydrocarbons condensed together on the carbon hexagonal network surface, and then form submicron basic spherical particles, and several or dozens of tiny spherical particles will be connected together to form the primary structure of aggregation state, and these aggregated structures will also form secondary structure due to the van der Waals force between molecules, the complex primary and secondary structure makes it have a large number of pores inside, and these pore sizes are directly related to the structure of carbon black. Carbon black particles produced by different methods have different sizes and structures, and correspondingly their surface areas and particles The degree of cohesion is also different.

Figure 1 Schematic diagram of carbon black production by oil furnace method.

The spherical particles in the carbon black are in turn stacked by scaly densely arranged graphene sheets, and the structural model is shown in Figure 2. Figure 3 shows the different aggregation types of carbon black particles, and the content of various aggregation types in different grades of carbon black is also different. The carbon black with low aggregation structure mainly has the first two types in Figure 3, while the carbon black with high aggregation structure is mainly the latter two types in Figure 3.

Fig.2 Structural model of carbon black

Fig.3 Different aggregation types of carbon black particles.

The surface of carbon black particles as shown in Figure 4, because there are many carbon atoms at the edge and defects, oxidation in the air will thus form a variety of oxygen-containing functional groups as shown in the figure, these structural features will affect the various practical properties of carbon black.

Fig.4 Various oxygen-containing functional groups formed on the surface of carbon black particles

As mentioned earlier, carbon black is mainly used as a reinforcing agent and filler for rubber, and its consumption is about half of the rubber consumption. In addition, it is also used as a colorant for inks, coatings and plastics, and as an ultraviolet light shielding agent for plastic products. It is also an important additive in electrodes, dry batteries, resistors, explosives, cosmetics and polishing pastes.

The production process of carbon black is not complicated, but it is not easy to produce carbon black particles with uniform structure. Because of this, although China is currently one of the largest countries in the production of carbon black and gel pens, it still needs to import a large number of gel pen inks produced from carbon black as raw materials from abroad, which is indeed worth pondering by relevant personnel!

This article is from Wang Maozhang Science Net blog.
Link address: http://blog.sciencenet.cn/blog-526286-507990.html