Styrene butadiene rubber is considered one of the most used polymer materials. It is suitable for the manufacture of tires and other rubber products of high quality.
The named polymer material is made from inexpensive raw materials, and its manufacturing technology is considered quite affordable, having a clear algorithm of actions. The resulting styrene butadiene rubber has excellent performance and chemical characteristics. It is produced in significant volumes and is represented by the manufacturer in a wide range.
Raw materials for production
Let us consider in more detail the production of styrene-butadiene rubbers. Butadiene-1,3 or alpha-methylstyrene are selected as the starting material for this polymer material. Get styrene-butadiene rubber by solution technology or emulsion copolymerization. In the second method, styrene-butadiene solution rubbers are formed.
Emulsion Polymerization
How is styrene butadiene rubber produced? The reaction involves the joint polymerization of styrene and butadiene in an emulsion. The final product resulting from this interaction is called styrene butadiene rubber (SCS).
At the moment, in the domestic rubber industry, a variety of polymer products are manufactured on the basis of this chemical.
How is styrene butadiene rubber divided? Manufacturers offer the following options:
- rubbers that do not contain oil (SKS-ZOARK);
- materials with an average percentage of oil (SKM-ZOLRKM-15);
- with an increased amount of oil (SKS-ZODRKM-27);
- with excellent dielectric characteristics (SKS-ZOARPD).
Name Specificity
The first figures in the given names tell about the quantitative content of styrene in the initial charge selected for the polymerization process:
- "A" implies the implementation of the low-temperature polymerization process (not more than +5 degrees).
- "M" indicates that it contains oil, not only styrene.
- Styrene-butadiene rubber with the letter "R" talks about the polymerization reaction without a regulator.
- "K" indicates the use in the manufacture of rubber rosin emulsifier.
- The letter "P" symbolizes the material obtained in the presence in the initial mixture of salts of fatty, synthetic acids, which are the products of partial oxidation of saturated paraffins.
What is characterized by styrene butadiene rubber? Getting it is based on the polymerization process, which is familiar even to high school students studying in secondary schools and colleges.
So, for the production of plantar rubbers in industry, resin-filled styrene-butadiene rubber is used, the formula of which is no different from ordinary diene hydrocarbon. Rubbers made on the basis of styrene-butadiene resin have increased resistance to mechanical abrasion and good skin-like characteristics.
Carry out the process of emulsion polymerization in a special industrial installation. What is characterized by this styrene butadiene rubber? Getting it is carried out on a clear and well-established technology. The average duration of a chemical reaction is 12-15 hours. After completion of the polymerization, latex is formed, which contains about 30-35 percent of the polymer substance. Neon D. is introduced into latex as an antioxidant.
From latex, rubber is produced by coagulating electrolytes that contain sulfuric acid. Considering that rosin oil and soap created on the basis of synthetic fatty acids act as emulsifiers, in addition to coagulation, the formation of fatty acids is also observed, which have a positive effect on the technological characteristics of the finished product.
Thanks to the addition of sulfuric acid, the soap is converted into free organic acids, latex coagulation is completed and styrene-butadiene rubber is formed. The use of finished material is multifaceted, depending on the type of production. Mostly rubber is a common raw material in the chemical industry.
Rubber structure
What structure does styrene butadiene rubber have? The physical properties of this substance are determined by the features of its structure. Upon receipt of the polymer by ozation, a polymer of irregular structure is formed. In the rubber, monomer units are randomly located, the molecule has a branched appearance.
Almost 80 percent of all links have a trans configuration, and only 20 percent is characterized by a cis structure.
Specifications
Let us analyze styrene butadiene rubber. The properties of this substance are associated with its high molecular weight. On average, it is 150,000-400,000. And the technology for the manufacture of oil-filled rubbers involves the selection of materials with a large relative molecular weight. This option allows you to eliminate the negative impact of oil on the quality of rubber, to maintain excellent technological characteristics of rubber for a long period.
Styrene-butadiene rubber can be obtained from ethylene by conducting a process chain using activators, emulsifiers, regulators, as well as other substances, partly in the process of interaction being converted into the resulting rubber.
Distinctive features
We characterize styrene butadiene rubber. The formula of this substance indicates that it is resistant to mechanical deformation, aggressive solvents. To increase the frost resistance and elasticity of the rubber, the amount of styrene is reduced in the initial mixture. The resulting polymer is soluble in gasoline and aromatic solvents.
What else stands out styrene butadiene rubber? The properties and attitude to concentrated acids, ketones, and alcohol are stable; moreover, the polymer has excellent gas and water permeability. During heating of the rubber, serious structural changes are observed, which negatively affects the physical and mechanical properties of the resulting rubber.
Thermal oxidation at temperatures from 125 ° C causes a decrease in stiffness and degradation. Subsequent oxidation involves serious structuring of the polymer, affects the increase in its rigidity.
Application features
Styrene butadiene rubber is used to create the rubber compound. The properties and application of this representative of the class of diene hydrocarbons are fully consistent with the features of its structural formula.
The presence of side phenyl groups affects the increased resistance to the negative effects of radiation exposure in comparison with other varieties of these polymers.
Rubber compounds, which are made on the basis of styrene-butadiene rubbers, have low stickiness and increased shrinkage during calendaring and extrusion. This negatively affects the implementation of technological processes, as well as during the gluing (assembly) of blanks of rubber products.
Low-temperature rubbers have improved technological properties, they are called "hot" rubbers.
Types of rubbers
Soft styrene butadiene low temperature rubbers have a low viscosity, so they do not plasticize.
Hard rubbers are produced in small quantities, subjecting them to thermo-oxidative plasticization in air at a temperature of about 1400 ° C using activators of the destruction process.
Unfilled vulcanizers have a low tensile strength. With a decrease in the amount of bound styrene in the polymer compound, the resistance and abrasion resistance decrease, frost resistance increases, and elasticity increases.
Soothen-filled (with carbon black ) styrene-butadiene rubber vulcanizers have excellent heat resistance and wear resistance, but to some extent they are inferior to conventional rubbers in terms of elasticity and deformation resistance. Used vulcanizers have additional resistance to concentrated and dilute acids, alcohols, alkalis, ethers. In rubber solvents they swell.
All the obtained polymers are used in the manufacture of tires, the manufacture of a variety of non-molded and molded products. For example, conveyor belts for forestry production are made from styrene-butadiene rubber, rubber shoes are produced. Due to the increased radiation resistance, all these rubbers are used in the manufacture of rubbers having optimal resistance to gamma radiation.
For the production of products characterized by excellent frost-resistant characteristics, raw materials are used, which contain a minimum styrene content.
Characterization of styrene-butadiene rubbers of solution polymerization
In the domestic industry, production of styrene-butadiene rubbers of solution polymerization having different styrene contents has been established:
- DSSK-10.
- DSSK-25.
- DSSK-18.
- DSSK-50.
- DSSK-25D (has increased dielectric characteristics).
On sale there is also rubber, which includes microblocks of aromatic styrene, intended for processing by casting.
In addition, there are oil-filled rubbers of solution polymerization, which contain up to 27% oil. Thanks to solution polymerization, in the presence of organolithium catalysts, the main parameters of the molecular structure are adjusted:
- branching chains;
- molecular weight;
- macrostructure.
The distinguishing characteristics of such rubbers are the significant presence of the polymer itself (up to 98%), the minimum amount of impurities. The polymers have a linear structure in comparison with styrene butadiene emulsion rubbers.
The resulting polymer materials have higher ductility, wear resistance, frost resistance, and increased resistance to cracking. We also note the high dynamic endurance of these materials. With less shrinkage, they have a higher Mooney viscosity, since the macromolecules have a linear structure, can be filled with a large number of soot (carbon black) and oil without negatively changing the mechanical and physical properties of the vulcanizers.
There are some technological advantages in the production of mortar rubbers in comparison with emulsion options, but there is a much greater requirement for the purity of the monomers used. Mortar polymerization rubbers are used in the tire industry to create durable conveyor belts, shoe soles, rubber sleeves, and numerous rubber parts. Styrene and buadiene-1,3 are considered as the initial components for the production of polymer materials of this type. Rubbers are obtained by solution or emulsion copolymerization.
In modern production, not only the technology for manufacturing unfilled rubbers is used, but also the production of polymers is established, which include resins, carbon black, oil. Of all the polymer materials produced, styrene butadiene rubber accounts for more than half of all production capacities.
The reason for this scale is the high homogeneity of the physical and chemical characteristics of the product, the availability of the starting monomers (styrene and butadiene), as well as an established production line.
A large mass of styrene-butadiene rubber in modern production is obtained by emulsion copolymerization of styrene and butadiene.
Classification of rubbers by structure
Taking into account the polymerization conditions and the composition of the components used, the production of styrene-butadiene rubbers is established, which differ in properties and composition. A statistical, irregular distribution of the structural units of styrene and butadiene in the macromolecule is allowed.
With decreasing temperature, a decrease in the quantitative content of low molecular fractions in the rubber being created is observed. In addition, there is a decrease in structural branching, an increase in the regular structure of the polymer, which positively affects the technical and operational characteristics of the finished product.
In the development of domestic production of synthetic materials, an important point was the establishment of production of styrene-butadiene materials by polymerization by a radical mechanism. Currently, such materials of high quality and at an affordable price are produced at the plants of Krasnoyarsk, Omsk, Tolyatti, Sterlitamak, Voronezh.
Technology features
If desired, a polymer having certain parameters can be obtained. For example, with a given average molecular weight, which is regulated during polymerization by introducing regulators capable of chain transfer. With an increase in the quantitative content of regulators, a decrease in the molecular weight of the polymer is observed.
What can be considered as emulsifiers suitable for the production of stable emulsions of monomers, as well as for the creation of final polymerization products, latexes? Potassium or sodium salts of synthetic synthetic fatty carboxylic acids, hydrogenated rosin, and also salts of alkyl sulfonates are considered as the main chemical components.
When choosing rosin, it is first subjected to special processing. In the process of disproportionation of the catalyst (palladium), it acquires the properties necessary for the rubber chain.
Production specifics
For copolymerization using a battery of polymerization. When preparing the mixture, purified and pre-dried styrene, butadiene, a solvent (it may be cyclohexane) are mixed in a ratio of 5/1. Further, the components of the initial charge are fed into the diaphragm mixer for high-quality mixing. Then the mixture is sent for chemical fine purification from a variety of small impurities.
Organolithium compounds are fed into the apparatus, titrated at a temperature of 25 ° for 20 minutes. The degree of purification is determined by the color of the mixture. If there are no impurities, the mixture has a faint brown color. Before polymerization, the mixture is mixed with a catalyst, polar additives.
The process is carried out in a battery, which consists of three standard devices, by sequential supply of the charge. The temperature inside the polymerizers is maintained in the range from 50 to 80 ° C. The average duration of the entire chemical process is 6 hours.
Conclusion
In any area of life and activity of a timely person, there are materials based on styrene-butadiene rubber. First of all, we note the creation of rubber soles for shoes, automobile rubber tires, and a variety of watering hoses.
Statistical copolymers of styrene and butadiene are widely used in the creation of electrical insulating materials, various products for the automotive industry, including the creation of high-quality tires. Innovative technologies used by modern manufacturers of styrene-butadiene rubbers allow them to create products with specified physical and chemical parameters, desired performance characteristics.
Among the features of this production, we note the use of high quality catalysts. Depending on the structure of the synthesized rubbers, the duration of the process of their creation, as well as the final cost of rubber products manufactured on the basis of rubber, significantly differs.