Basic knowledge of carbon black

1. What is carbon black

The main component of carbon black is carbon, and its basic particle size is between 10 and 100 nm. Therefore, carbon black has excellent rubber reinforcement, coloring, conductive or antistatic properties, as well as ultraviolet absorption functions. It is the earliest nano level material developed and applied by humans.

2. Application fields of carbon black

As a functional material, carbon black plays an irreplaceable role in many fields. Carbon black is a rubber reinforcing filler, which is the second largest rubber raw material after raw rubber. Carbon black is also widely used as a colorant, ultraviolet shielding agent, antistatic agent, or conductive agent in many industries such as plastics, chemical fiber, ink, coatings, electronic components, leather chemicals, and dry batteries. Carbon black can also be used as a high purity carbon material in the metallurgical and carbon industries.

3. Manufacturing method of carbon black

Carbon black is produced by incomplete combustion or thermal decomposition of hydrocarbon compounds (liquid or gaseous), mainly composed of carbon elements, and exists in the form of colloidal particles similar to spheres and aggregates with colloidal size. The appearance of carbon black is black powder.

4. Classification of carbon black

Carbon black can be divided into two categories according to its use, namely rubber carbon black and special carbon black.

Rubber carbon black can be divided into hard carbon black and soft carbon black according to its reinforcement properties. Hard carbon black has a strong reinforcement effect on rubber. The rubber compound filled with hard carbon black has high hardness, good strength, elongation, and wear resistance. It is mainly used for the tread of tires, also known as tread carbon black. Soft carbon black has low hardness and good elasticity, and is mainly used in the carcass of tires, also known as carcass carbon black.

Special carbon black can be divided into carbon black for printing ink, coating, sealant, color masterbatch, and building materials according to its use.

5. Bulk density of carbon black

According to the structure and physical morphology of carbon black, the bulk density of carbon black varies greatly among various levels of carbon black. Due to the presence of closed air, the bulk density of carbon black is lower than its true density (specific gravity). The true density (specific gravity) of carbon black aggregates is approximately 1.8 grams per cubic centimeter (112.5 pounds per cubic inch).

6. Shelf life of carbon black

When stored in a dry and sealed environment, carbon black is not susceptible to decomposition, and its shelf life is not limited. Over time, carbon black absorbs moisture until it reaches an equilibrium value. If the impact of moisture is important, carbon black should be stored in a dry environment and sealed as much as possible.

7. Particle size

The size and distribution of carbon black particles is one of the most important properties of carbon black. Almost all carbon black particles do not exist alone, but exist in an aggregate state during the production process of carbon black. The aggregate is the smallest unit of carbon black that exists alone. The particle size directly affects the other properties and usability of carbon black. The particle size of carbon black is mainly measured by electron microscopy.

8. Method for measuring the structure of carbon black

The dibutyl phthalate oil absorption value method is a measurement method used to measure the structure of carbon black. Higher oil absorbent paper corresponds to a higher carbon black structure.

9. Specific surface area

The specific surface area of carbon black refers to the sum of the surface areas of carbon black particles per unit mass or volume, expressed in m2/g or 103m2/kg. Specific surface area is one of the basic properties of carbon black as well as particle size. Due to its convenient testing methods, it replaces particle size as the basis for classification of carbon black. For carbon black with a smooth surface, the specific surface area is inversely proportional to the particle size, that is, the smaller the particle size, the greater the specific surface area, and vice versa. The particles of carbon black are very small, so the specific surface area is large. The specific surface area of pigment carbon black is between 150-710m2/g. There are many methods for measuring specific surface area, including nitrogen adsorption method, iodine absorption value method, CTAB method, etc. The iodine absorption value method is expressed as the mass of iodine adsorbed per gram of carbon black, in mg/g.

10. Structure of carbon black

Carbon black aggregates exhibit a chain like shape and are very complex in shape. Aggregates attract each other to form larger agglomerates, collectively referred to as carbon black structures. There are two methods for determining the structure of carbon black, namely, the oil absorption value method and the compression specific volume method. Both methods are based on measuring the void volume in carbon black to characterize the structure of carbon black. The oil absorption value method is based on the determination of the minimum amount of dibutyl phthalate (DBP) required to saturate the pores and surfaces filled with dendritic structures, known as the DBP oil absorption value. High structure carbon black has a more developed chain branch structure, which is more loose when stacked, and therefore has a higher oil absorption value, and vice versa. The oil absorption value of carbon black also has a certain relationship with its specific surface area. Carbon black with a large specific surface area has a higher oil absorption value. In other words, only when the specific surface area is the same, can the oil absorption value objectively reflect the structure of carbon black.

11. Coloring strength of carbon black

The coloring strength is based on the measurement of the reflectance of a slurry composed of carbon black and zinc oxide in the oil, which is used to measure the ability of carbon black to reduce the amount of reflected light. Higher coloring power can be achieved by reducing the particle size of the primary particles.

12. Surface Properties of Carbon Black

Carbon black is mainly composed of carbon elements, with a carbon content of 90% - 99%, and also contains a small amount of hydrogen, oxygen, nitrogen, etc. These elements are mainly derived from the raw materials of carbon black.

13. Conductivity of carbon black

Carbon black is a semiconductor that can significantly reduce the resistivity of materials that typically have high electrical resistance by adding carbon black.

14. Acetylene carbon black

Acetylene carbon black is made by the thermal cracking reaction of acetylene, and is a very pure carbon black. It is the closest graphite structure of all carbon blacks, so its electrical conductivity is relatively good.

15. Thermal conductivity of carbon black

There is little available data on the thermal conductivity of carbon black. Data studies on the thermal conductivity of rubber compounds containing carbon black and rubber compounds without carbon black indicate that carbon black improves the thermal conductivity of rubber.

16. Surface oxidized carbon black

In order to improve a certain property of carbon black, the chemical adsorption amount of oxygen on the surface of carbon black is increased through later oxidation treatment, thereby improving the dispersion and stability of carbon black and reducing its viscosity.

17. Primary particle

The initial particles formed during the manufacturing process of carbon black become primary particles. Almost all primary particles of carbon black do not exist alone, but exist in an aggregate state during the production process of carbon black, which is the smallest unit of carbon black that exists alone.

18. The preparation of carbon black dispersion requires the use of dispersants or surfactants

In the optimal dispersion system, the dispersant is continuously dispersed in a single layer around the carbon black aggregate, so the amount of dispersant required to form a fluid dispersion is related to the surface area of the carbon black used. For a given amount of carbon black added, carbon black with a large surface area requires more dispersants.

19. Factors affecting the glossiness of paste inks

In paste inks, the gloss depends on the quality of the dispersion and the particle size of the carbon black aggregate. The smaller the aggregate, the better the dispersion, and the higher the glossiness.

20. Factors affecting the fading phase of ink carbon black

The particle size and dispersion of the primary aggregate affect the fading phase. The smaller the initial aggregate, the lower the fading phase.

21. Manufacturing process of carbon black

The manufacturing process of carbon black includes oil furnace method, lamp smoke method, spray method, slot method, hot cracking method, drum method and aerosol method. At present, more than 95% of carbon black is produced by oil furnace method.

Method for measuring the morphology of carbon black dispersion in liquids

A widely accepted method for quickly measuring the mass of dispersions in paint is the use of a Hergmann fineness meter. For ink, use G-1, G-2, and G-3 meters. However, these types of instruments cannot measure differential dispersion, which largely determines the performance of carbon black. A better way to measure carbon black dispersion is by displaying color and glossiness. For example, the glossiness count together can record the dispersion time and determine the time point at which carbon black is dispersed to its maximum extent in the final product.

23. Grade of carbon black

The properties of carbon black require special formulation to suit specific applications. The properties of carbon black can usually be controlled by changing its surface properties.

24. Carbon black absorbs moisture

Carbon black absorbs moisture until it reaches equilibrium. This value is usually expressed as% by weight, and varies with different grades of carbon black.

25. Porosity of carbon black

Traditional furnace process carbon black contains very few pores, and any pores that exist are limited to the range of micropores (nanoscale). Such pores can be quantified as total micropore volume through nitrogen adsorption isotherm analysis.

26. Decomposition of carbon black

Typically, in air and oxygen, carbon black begins to decompose between 450 and 500 degrees Celsius. Carbon black does not decompose in nitrogen at these temperatures. The ash content of carbon black is usually measured at 550 degrees Celsius.

27. Application of carbon black in electrochemical applications

Due to the conductivity and relatively low resistance of carbon black, it can be used in various electrode components used in oxidation and reduction equipment.

28. Mechanism of providing electrical conductivity in carbon black like polymers

Carbon black has more conductivity than polymers, rubber, or resins. Adding carbon black will form a conductive network in the polymer matrix, thereby reducing the resistivity. The carbon black level has been developed to optimize conductive performance at a lower load while meeting all other key properties in conductive applications.

29. How carbon black helps form the covering power of the final product

Carbon black is a high-quality opacifier that can be used in a variety of applications. This property stems from the ability of carbon black to absorb visible spectral radiation. This excellent absorption ability can greatly reduce the absorption and projection of light.

30. Physical morphology of carbon black

All grades of carbon black can be made in powder or fluffy form, bead or granular form.

31. CAS number of carbon black

1333-86-4

32. PH value of carbon black

The PH value of carbon black refers to the amount of oxygen adsorbed on the surface of carbon black. For most grades, low concentrations of oxygen compounds and a small amount of water-soluble salts on furnace process carbon black can neutralize the slightly alkaline pH value. In order to enhance specific properties, carbon black is subjected to surface oxidation to increase the presence of chemical oxygen groups. These products typically have an acidic pH value.

33. Chemical formula of carbon black

C

34. Primary particles of carbon black

The particle size of the primary particles of carbon black can be controlled during production. The particle size can range from 8 nm to 75 nm.

35. Dispersibility of carbon black

The dispersibility of carbon black usually refers to its easy or difficult dispersibility. Typically, it is a relative measure of dispersion of standard carbon black. As the surface area of carbon black decreases/the structure increases, the dispersion of carbon black increases. However, other properties of carbon black will change with changes in surface area and structure.

36. Solubility of carbon black

Normal carbon black is insoluble in water, and the carbon black after post treatment is soluble in water.

37. Volatile content of carbon black

Volatile content is a unit of measure (expressed as a percentage of weight loss) that measures the amount of chemically adsorbed oxygen groups that will be released when the carbon black is heated to a high temperature. The value of the volatile content does not include absorbed moisture. This is not related to the traditional volatile content, which refers to the content of absorbed organic compounds. Under heating conditions, chemically adsorbed oxygen groups can be decomposed and disappear by converting them into gases, such as carbon dioxide and water.

38. Mixing of carbon black

Mixing carbon black is an important step in dispersing carbon black, which refers to the use of resins or solvents to wet the surface of carbon black. Essentially, it refers to replacing closed air and completely covering the surface of the aggregate to obtain a dispersible mixture that is easy to process.

39. Method of influencing the dispersion rate by the physical form of carbon black

Powdered carbon black or more dense granular carbon black can be directly used. Granular carbon black is easier to handle and mixes faster than powdered carbon black. However, granular carbon black is difficult to disperse because the densification process increases the proximity of the agglomerate, thereby increasing the Van der Waals force that must be served during the dispersion process.

40. Use of carbon black

Carbon black can be used to reinforce rubber, and can be used in various industries such as ink, paint, paint, sealant, cement, building materials, and plastics.

41. The structure of carbon black affects the glossiness

Due to its high oil absorption, high structure carbon black has a greater reduction in the glossiness of the finished product than low structure carbon black.

42. The principle that the structure of carbon black affects the dispersion rate

Carbon black with a high structure is generally more easily dispersed than carbon black with a similar specific surface area and a low structure. The aggregates in high structure carbon black consist of many primary particles, which form pellets and have a considerable number of branching and chain structures. Therefore, the aggregation effect of the aggregates is poor, reducing the attraction between the aggregates. Low structure carbon black is more compact, allowing aggregates to be closer together, resulting in greater attraction between aggregates, making dispersion more difficult. However, although dispersing low structure carbon black requires more energy, its higher density makes it easier to wet because it removes less air.

43. How surface oxidation of carbon black affects electrical conductivity

Under the same surface area and structure conditions, the conductivity of oxidized carbon black is weaker than that of non oxidized carbon black. Due to the greater insulation of the surface after adsorption of oxygen containing groups, the electrical conductivity is reduced.

44. The principle that the surface area and structural properties of carbon black affect product viscosity

Structure is the primary factor affecting product viscosity, followed by surface area. When studying the effects of structural changes in carbon black, using high structure carbon black to replace low structure carbon black with the same surface area will result in higher viscosity of the final product. Using high surface area carbon black to replace low surface area carbon black with the same structure will test the final product to obtain a higher viscosity.

45. The principle that the surface area of carbon black affects the dispersion rate

Compared to low surface area carbon black with the same structure, carbon black with a higher surface area is more difficult to disperse, partly due to the higher level of wetting surface area and the higher energy required. Similarly, as the primary particles become smaller, a certain volume of carbon black per unit weight contains more aggregates, resulting in smaller distances between aggregates, more contact points, and stronger attraction between aggregates.

46. Relationship between color properties and surface area of carbon black

Carbon black with a larger surface area appears darker, while carbon black with a smaller surface area appears grayer.

47. Effect of carbon black structure on color characteristics

Compared to specific surface area, the structure of carbon black has a smaller impact on color, but the color of high structure carbon black is weakened, and due to its better dispersion, the color phase is bluer than that of ground structure carbon black with the same surface area.

48. Effect of Surface Chemistry of Carbon Black on the Dispersion Rate of Carbon Black

After treatment, the content of adsorbed oxygen on the surface of carbon black is increased, which can improve the wettability and make it easier to disperse. The dispersion stability of carbon black is also improved, and the viscosity of the product is reduced.

49. Content of carbon black used in the formula

Generally, if carbon black is used for coloring in plastics, it should be provided to a color master manufacturer who disperses the carbon black at a high load (25% to 50% by weight, depending on the type of carbon black, the type of plastic resin, and the type of mixing equipment). The master batch supplier provides it to the mixing processor, who dilutes the master batch to the final use level (0.5% - 3%). Carbon black may be difficult to disperse, so blending is performed under high loads to enhance shear strength, thereby dispersing carbon black. Dispersion is important for product quality because it facilitates the color development, surface quality, mechanical properties, and processing of plastic compounds.

50. Particle size reduction affects the properties of plastic compounds

As the particle size of carbon black decreases, the following properties will change: the main color tone or blackness becomes darker, the coloring intensity becomes stronger, the masterbatch viscosity becomes higher, and the dispersion of carbon black becomes more difficult.

51. Factors to Consider when Choosing to Use Powdered or Granular Carbon Black

Granular carbon black is easier to store, transport, and handle than powdered carbon black. With less dust, it is easier to clean and reduces production management issues. Granular carbon black is not as good as