What other knowledge do you not know? As a basic industrial raw material - carbon black has many treasure uses, and these uses of carbon black also provide great convenience to our life. Let's talk about the reinforcement of carbon black, the coloring of carbon black, the conductive function of carbon black and how these functions of carbon black are used in all aspects of our lives.
The main component of carbon black is carbon, and its basic particle size is between 10 and 100nm. Therefore, it has excellent rubber reinforcement, coloring, conductivity or antistatic, and ultraviolet absorption functions. It is the earliest nanomaterial developed and applied by humans. As a functional material, carbon black can endow other materials or products with some special performance, and plays an irreplaceable role in many fields. Carbon black is a rubber reinforcing filler and the second rubber raw material after raw rubber. Carbon black is also used as a colorant, UV shielding agent, antistatic agent or conductive agent, widely used in plastics, chemical fibers, inks (including copier toner, inkjet printing inks, etc.), coatings, electronic components, leather chemicals and dry batteries And other products in many industries. Carbon black can also be used in metallurgy and carbon material industries as high-purity carbon materials.
Carbon black is the first to be manufactured and applied in my country. As early as 3000 years ago, the technology of burning smoke to make ink has been mastered, but it has remained at the stage of handicraft production for a long time. In 1872, the industrialized production of channel carbon black was first realized in the United States. In the early 20th century, the reinforcing effect of carbon black in rubber was first discovered in the United Kingdom. With the development of the world's automobile and tire industries, the carbon black industry has also developed. Market reports predict that global demand for carbon black will rise to 17 million tons per year by 2030.
1. Carbon black reinforcement function
1. What is the reinforcement of carbon black
Carbon black is one of the main raw materials in the rubber industry and is a powder material. The amount of carbon black is quite large, almost equivalent to the amount of rubber itself. In rubber processing, fillers are divided into reinforcing agents and fillers. Rubber reinforcement refers to the behavior of adding a substance to rubber to improve the properties of vulcanized rubber such as wear resistance, tear strength, tensile strength, modulus, and swelling resistance. Any substance that has this effect is called a reinforcing agent. Common reinforcing agents: carbon black, silica, short fibers, inorganic nanomaterials, etc.
2. Carbon black for rubber
According to worldwide statistics, the consumption of carbon black for rubber accounts for about 89.5% of the total carbon black, of which 67.5% is for tires, 9.5% is for automotive rubber products, and 12.5% is for other rubber products. Non-rubber carbon black (also known as special carbon black or special carbon black) accounts for about 10.5%, of which plastics account for 4.5%, inks account for 3.8%, coatings account for 0.9%, and other products account for 1.3%.
Carbon black is the most important reinforcing filler in the rubber industry. It is no exaggeration to say that without the carbon black industry, there would be no booming rubber industry. According to the role of carbon black in rubber, carbon black is divided into hard carbon black and soft carbon black. Hard carbon black: carbon black with a particle size below 40nm and high reinforcing performance, such as super wear-resistant, medium super wear-resistant, high wear-resistant carbon black, etc. Soft carbon black: Carbon black with a particle size above 40nm and low reinforcing properties, such as semi-reinforcing carbon black, thermal black, etc.
Carbon black for rubber is generally classified and named according to the ASIM-1765-81 standard. The naming system consists of four parts. The first English letter represents the vulcanization speed, N represents the normal vulcanization speed, and S represents the slow vulcanization speed. Followed by three numbers, the first represents the average particle size range of carbon black, which is divided into 0~9 grades. The second and third numbers are designated by the D24.41 committee of the American Society for Testing and Materials responsible for carbon black and terminology, reflecting different structural degrees, that is, the approximate high and low structures of carbon black, which are somewhat arbitrary. Relatively speaking, the larger the number, the taller the structure. ASIM's carbon black classification nomenclature.
The reinforcing effect of carbon black lies in its surface activity and its ability to combine with rubber. The rubber can be well adsorbed on the carbon black surface, wetting the carbon black. Adsorption is a physical process, that is, the attractive force between carbon black and rubber molecules is greater than the cohesive force between rubber molecules, that is, physical adsorption. This binding force is relatively weak and is not sufficient to account for the main reinforcing effect. The main reinforcing effect lies in the inhomogeneity of carbon black. Some active points with high activity have unpaired electrons and can chemically interact with rubber. Rubber is adsorbed on the surface of carbon black and several points are chemically combined with the surface of carbon black. This effect is called chemical adsorption, and chemical adsorption is much larger than pure physical adsorption. The characteristic of this chemical adsorption is that the molecular chain is relatively easy to move on the surface of carbon black, but it is not easy to separate from carbon black. In this way, the rubber and carbon black form a strong bond that can slip. This bond creates a second reinforcing effect. The first reinforcement effect is that when the rubber is deformed by an external force, the slippage of the molecular chain and a large amount of physical adsorption can absorb the impact of the external force, and act as a buffer for the friction or hysteresis deformation caused by the external force; the second effect is Make the stress distribution even. The result of these two effects is an increase in rubber strength. Resists tearing without overly compromising the elasticity of the rubber (i.e. the movement of the molecular chains). This is the basic principle of carbon black reinforcement.
Carbon black is an indispensable raw material for the rubber industry. About 94% of carbon black is used in rubber products. There are many kinds of rubber products with different service conditions and performance requirements. The main products are rubber hoses, rubber damping products, rubber sealing products, rubber rollers, conductive or antistatic rubber products, hard There are several categories of products such as rubber and rubber shoes, and each type of rubber products is subdivided into several varieties according to the purpose and conditions of use.
Carbon black is used as an important reinforcing agent in rubber products. It can improve the wear performance of tires, and increase the tensile strength and tear strength of rubber compounds. In carbon black for rubber, about 75% of the carbon black is made into tires, and the rest is used to make rubber hoses, tapes, etc.
3. Reinforcement mechanism of carbon black
At present, the strengthening mechanism of carbon black mainly includes molecular chain sliding theory, bonding glue theory, filler network theory, carbon black surface structure theory and van der Waals network theory, etc.
(1) Molecular chain sliding theory
The molecular chain sliding theory believes that the rubber molecular chains adsorbed on the surface of carbon black have certain mobility. When there is stress, the rubber molecular chain slides on the surface of the carbon black particles. After the external force is removed, the rubber shrinks. After a long period of recovery, the adsorption and desorption reach a new dynamic balance, and the rubber returns to or is close to the original state.
(2) Combined with the theory of double-layer model glue
According to the theoretical model, the bonding adhesive adsorbed on the periphery of carbon black is composed of an inner vitrified hard layer and an outer viscous hard layer. When the stress gradually increases, due to the orientation of the viscous hard layer, the modulus increases The large contribution is very large, because the movement of the polymer molecules in the vitrified hard layer is restricted, and it has no effect on the modulus increase.
(3) Packing network theory
With the increase of carbon black content, filler network structure can be formed between carbon black particles. For the formation of the filler network, the interaction between filler and filler, filler and polymer, and the distance between aggregates are important influencing factors.
(4) Carbon black surface structure theory
The theory holds that the surface of the active filler is uneven, and the reinforcement of the elastomer is affected by the roughness and size range of the surface structure of the active filler. This structure has a huge impact on volume effects or interactions between fillers and aggregates.
(5) Van der Waals network theory
The theory holds that when the rubber deforms, the deformation of the suction rubber between the filler particles is much greater than the macroscopic deformation, so the filler particle aggregates can produce internal slippage. The reinforcing effect of the rubber is related to the thickness distribution of the occluded rubber, and the critical stress that separates the particles is the van der Waals stress between the particles.
Since the 21st century, due to the advancement of science and technology, the properties of rubber have been continuously developed and applied. At present, rubber products have existed in all aspects of people's lives, supporting people's basic necessities of life. The role of rubber is so great, and carbon black also plays a very important role in it, which can be said to be the greatest contribution.
Second, the coloring effect of carbon black
After talking about the reinforcement of carbon black, the editor below will take you to understand another major function of carbon black-coloring. Everyone knows that carbon black is a very common industrial raw material, and everyone already has a certain understanding of carbon black. Next, the editor has to propose a new concept-pigment carbon black.
Pigment carbon black refers to the pigment used as a colorant in coatings, inks, plastics, chemical fibers and leather chemicals.
Its main function is coloring. The Chinese national standard GB/T 7044-1993 "Technical Conditions for Pigment Carbon Black" stipulates the classification, variety name and code of pigment carbon black. Generally divided into high, medium and low pigment three categories. Generally divided into high, medium and low pigment three categories. According to its blackness and manufacturing method, it can be divided into: high pigment tank black (HCC), high pigment furnace black (HCF), medium pigment tank black (MCC), medium pigment furnace black (MCF), ordinary pigment tank black ( RCC), regular pigment furnace black (RCF) and low pigment furnace black (LCF). Pigment carbon black color black is carbon black used as coloring pigments in inks, paints, coatings and other products. According to the coloring strength (or blackness) and particle size, it is generally divided into four types: high pigment carbon black, medium pigment carbon black, ordinary pigment carbon black and low pigment carbon black. It is mainly produced by contact method and oil furnace method.
Pigment carbon black is generally good for coloring plastics. Pigment carbon black can be selected according to coloring characteristics or physical and chemical properties. The choice of carbon black for coloring basically depends on the blackness of the finished product. Very fine pigment carbon black can be used to complete coloring with particularly high blackness requirements; products such as PE garbage bags, plastic bags, and cable materials only need a medium level of blackness, and carbon black varieties with low specific surface area and high structure can be used ;When plastics are toned, small errors in carbon black weighing and ingredients will lead to obvious color differences. Larger, the weighing error is relatively smaller, and it has the advantages of better dispersion and lower price.
For gray plastics, the use of fine-grained pigment carbon black tends to show a brownish gray, while the use of coarse-grained pigmented carbon black can produce a blue-shaded gray.
Compared with other organic pigments, carbon black has better properties except that it is difficult to disperse. The scientific amount of carbon black can provide better antistatic or electrical conductivity.
Carbon black is basically non-toxic, but it is easy to fly and pollute, so it is often used in the plastic industry in the form of masterbatch, which improves the dispersion of carbon black in plastics while eliminating pollution.
The basic idea of choosing carbon black:
The first thing users need to consider before choosing carbon black is: What requirements do you want to use carbon black to achieve? Coloring, toning, UV resistance or conductivity. The most important thing is to communicate with professional technical engineers of carbon black to conduct technical evaluation on the material system and select more suitable carbon black varieties. Usually the situation is:
For coloring - choose carbon black with high blackness and small particle size, but it must be ensured that the carbon black is properly and completely dispersed, otherwise it will run counter to the original requirements.
For color matching - choose carbon black with low blackness, large particle size and easy dispersion.
Anti-ultraviolet - mainly used in plastics and rubber and plastics, carbon black with medium particle size and slightly higher structure is selected, and their anti-ultraviolet performance is the best.
3. Conductivity of carbon black
The last function of carbon black that I want to introduce today is to conduct electricity. Yes, carbon black can also conduct electricity. Naughty boys must have been very interested in the used batteries at home when they were young. Everyone must have dismantled them by themselves. In fact, there is also carbon black in it, and carbon black plays a vital role in the conductivity of the battery.
Conductive carbon blacks are carbon blacks with low or high electrical resistance properties. It can impart conductive or antistatic effect to the product. It is characterized by small particle size, large and rough specific surface area, high structure, clean surface (less compounds) and other characteristics.
Conductive carbon black is based on the characteristics of carbon black itself, such as electrical conductivity, high structural properties, irregular aggregates and very small nanoscale, and easy mixing with other materials. It can form three-dimensional in insulator plastics, rubber inks, and paints. The conductive path of the network structure makes the insulator product have a conductive function under the action of conductive carbon black, so that the insulator material has antistatic and conductive capabilities. Effectively increase the performance and scope of the product, such as replacing mine ventilation pipes with steel pipes with conductive plastic pipes, utilizing the aging resistance of plastics, being able to export static electricity, and being easy to operate. Conductive carbon black has the characteristics of small particle size, high structure, pure surface, rough, porous and hollow shape, which can effectively form a three-dimensional network structure in the insulator and effectively improve conductivity. Conductive (carbon black) Carbon black is used in rubber, plastics, coatings and other industries. It can play a good anti-static role and avoid discharge caused by charge accumulation, which affects production safety. Conductive carbon black is the product with the best effect among all conductive fillers, low cost, and not easy to cause deterioration of the physical properties of the product.
Preparation of conductive carbon black by electrolysis of tar:
Conductive carbon black characteristics
1. Large specific surface area
The larger the specific surface area, the smaller the size of carbon black particles, the more particles per unit volume, the easier it is to contact each other to form a network path, so the larger the specific surface area, the better the conductivity.
2. Good dispersion performance
High structure and soft particle appearance, easy to process and disperse, balance the electrical/mechanical properties of the material, and the appearance of the final product is smooth and smooth.
3. Surface chemical properties
In the process of carbon black production, some active oxygen-containing groups are often formed on the surface of carbon black. The existence of these functional groups affects the migration of electrons and reduces the conductivity. The pH value can be used to characterize this index. Carbon black with few surface functional groups Usually weakly alkaline or neutral.
4. Excellent electrical conductivity
High-structure carbon black can achieve excellent electrical conductivity with a very low addition amount, and the electrical conductivity is basically not affected after secondary crushing.
Conductive carbon black products have great flexibility. Metal coating, particle core type, particle size and particle shape can be selected according to different application needs to meet different conductive and shielding requirements.
How to choose high-performance conductive carbon black?
Conductive carbon black is a special type of carbon black. They must have these basic characteristics, such as large specific surface area, less impurities for capturing electrons, and better crystallinity.
The structure of conductive carbon black refers to the degree of aggregation of very fine carbon black particles into chains or grapes, which is determined by the size and shape of the aggregate and the number of particles in each aggregate; the more particles that make up the aggregate , the higher the structure; the greater the probability of forming a network structure, the better the conductivity:
Carbon black composed of agglomerates composed of a large number of branched and cross-linked primary particles is called "high structure" carbon black. A higher structural property means that the chain or grape-like structure is more developed, it is easy to form a space network channel, and it is not easy to be damaged.
The high-structure carbon black particles are fine, the network chains are tightly packed, the specific surface area is large, and there are many particles per unit mass, which is conducive to the formation of a chain-type conductive structure in the polymer.
Generally, the oil absorption value (DBP) is used to characterize the porosity of carbon black, that is, the structure. The larger the oil absorption value DBP, the higher the carbon black structure and the better the conductivity.
The main application of conductive carbon black:
1. Anti-static products: conductive foam tube, charging roller, static eliminator, anti-static conveyor belt, anti-static rubber sheet, anti-static box, hollow board, anti-static tube, medical rubber products, carpet, copier roll, printing machine Rolls, packaging films for electronic components, explosion-proof cables; there are also anti-static table mats, anti-static soles, etc.
2. Conductive products: cable shielding materials, planar heating elements, conductive films, elastic electrodes, printed circuits, conductive coatings, conductive inks, conductive fibers, conductive leather products and adhesives. Mine conveyor belts, mine plastic pipes, mine air ducts, etc.
Why can conductive carbon black be widely used in batteries?
Conductive carbon black can be widely used in batteries for the following reasons:
(1) Conductive carbon black has a unique branch form, a large number of conductive contact points.
(2) Superconducting carbon black has high conductivity, and a small amount of addition can achieve high conductivity.
(3) The amount used is small, so that it can be filled with more active materials and increase the capacity of the battery.
(4) In the process of charging and discharging, the size of the battery resistance does not change with the continuous change of the battery volume, which increases the stability of the battery.
The microstructure of conductive carbon black Carbon black particles have a microcrystalline structure. In carbon black, the arrangement of carbon atoms is similar to that of graphite, forming a hexagonal plane. Usually, 3 to 5 such layers form a microcrystal. Due to the carbon black microstructure In each graphite layer of the crystal, the arrangement of carbon atoms is orderly, and the arrangement of carbon atoms between adjacent layers is disordered, so it is also called quasi-graphite crystal.
The above is the whole content of the introduction of the three major functions of carbon black, and we have learned a lot about carbon black. I hope that the editor's article can be helpful to everyone. If you have any questions, you can comment. The editor will know everything and say everything!