How Is Styrene Butadiene Rubber Made? Production Process Explained
Whether it be seat belts, tyres, seals, or gaskets, all of these are made of styrene-butadiene rubber. It is a rubber used for general purposes serving a wide range of applications. It fills a major part in modern-day technology, the reason being its long-range elasticity and wide applications.
The German scientists invented this back in the 1930s when the supply of natural rubber was cut off. It is one of the staple elements of the industrial and automotive sectors.
Let us provide you with the uses of styrene-butadiene rubber, the properties of SBR, its structure and all that you need to know.
What is SBR- Styrene Butadiene Rubber?
It is synthetic. The production of this takes place by the copolymerization of butadiene and styrene. The copolymer so formed contains:
Styrene Content: This is present in the range of 10-25%. This contributes majorly to good bonding and wearing characteristics.
Butadiene Unit: This is composed of 60-70% of the trans unit. 15-20% of cis-1,4 units. The configurations of these polymers happen at 50℃.
It gains high wear and abrasion resistance and strength through styrene.
The styrene-butadiene polymer takes place in two different forms, providing them with different properties.
Emulsion SBR is produced through both hot and cold types, which bring in changes in the properties of rubber. At low temperatures, emulsion SBR has good abrasion resistance. Alongside, this type of styrene-butadiene rubber provides good tensile and tear strength along with low resilience.
Approximately 75% of the SBR produced is solution SBR. This has more molecular weight and smaller distribution of molecules. It also has lower rolling resistance, high tensile strength, and flexibility, making it expensive compared to emulsion SBR.
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Properties of Styrene Butadiene Rubber
SBR Styrene Butadiene Rubber was first manufactured from Buna-S from Butadiene and Styrene through an emulsion in an aqueous solution.
After this, the production started off commercially during the 1960s, producing random SBR grades.
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The Key Properties of Styrene-Butadiene Rubber are as Mentioned Below:
It is widely used, pertaining to its availability and affordability.
SBR offers high tensile strength, abrasion resistance and resilience.
It has decent resistance and is flexible in low temperatures.
It is also resistant to organic acid, water, chemical, alcohol, ketone, and aldehydes.
It is crack resistant which allows it to accommodate fillers in large amounts hence enhancing its properties.
Carbon black: Increases the strength, abrasion and UV resistance of SBR.
China clay: It is used in the production of rubbers that are not black, which adds strength and reinforcement.
Calcium carbonate: This reduces the final amount of the product.
Silica: This increases the thermal conductivity, dimensional stability and electrical insulation.
Filaments: Reduces the ability to stretch for the finished products.
Uses of SBR
There are several uses of styrene-butadiene rubber, majorly across automotive and industries. The key applications that styrene-butadiene polymer serves are as follows:
It is used in car tires in lessening proportions and even in heavy-duty and high-performance tires. This is because of its high heat resistance.
In lighter-duty tires, cold emulsion SBR is used.
In speciality applications, solution SBR is commonly used. This happens because of its high cost—for example, motorcycle treads and radial car tyres.
One of the most common styrene-butadiene rubber uses is in automotive parts. For example, drive couplings.
It serves several industrial applications, including wire insulation and cabling, belting, roll coverings, haul-off pads, hoses, seals, gaskets, abrasion resistance and metal adhesion.
In commercial aspects, sbr polymer uses range from shoe soles, moulded rubber goods to carpet backing adhesive.
Production and Processing of Styrene-Butadiene Resin
The production starts off by mixing elastomers with the additives. This is followed by shaping the rubbers using different processing methods.
The Compounding of Additives with SBR Usually happens With:
Sulfur for vulcanization
Enhancing the mechanical properties by reinforcing fillers. Extending the rubber to reduce the cost.
Vulcanization
This process involves cross-linking elastomer molecules, which plays a key role in making the rubber stiff and strong. Alongside, this retains the extensibility of the rubber.
The vulcanization of styrene-butadiene rubber mainly occurs through the addition of sulfur, peroxides and sulfur donor system. As compared to natural rubber, sulfur is added in comparatively smaller amounts.
FAQs on Styrene Butadiene Rubber: Key Properties and Applications
1. What is Styrene-Butadiene Rubber (SBR)?
Styrene-Butadiene Rubber, commonly known as SBR or Buna-S, is a synthetic rubber derived from the copolymerization of two monomers: styrene (about 25%) and 1,3-butadiene (about 75%). It is one of the most widely produced synthetic rubbers and serves as a substitute for natural rubber in many applications due to its excellent abrasion resistance and aging stability.
2. How is Styrene-Butadiene Rubber (SBR) prepared according to the CBSE syllabus?
SBR is prepared through the process of emulsion polymerization. In this process, an emulsion of styrene and 1,3-butadiene is heated, typically between 40-60°C, in the presence of a free-radical initiator like potassium persulfate. This initiates a copolymerization reaction where the two monomer units link together to form the long polymer chains of SBR.
3. What are the most important properties of SBR?
Styrene-Butadiene Rubber exhibits several key properties that make it useful for various applications. These include:
- High Abrasion Resistance: It is very durable and wears down slowly, making it ideal for tyre treads.
- Good Tensile Strength: When reinforced with fillers like carbon black, it becomes very strong.
- Aging Stability: It resists degradation from heat and weathering better than natural rubber.
- Poor Oil and Ozone Resistance: It is susceptible to damage from oils, solvents, and ozone exposure.
4. What are the common uses of Styrene-Butadiene Rubber?
The primary application of SBR is in the automotive industry, accounting for a significant portion of its use. Common uses include:
- Vehicle Tyres: It is the main material used for the treads of passenger car tyres.
- Footwear: Used for making shoe soles and heels due to its durability.
- Industrial Hoses and Belting: Its toughness makes it suitable for conveyor belts and industrial hoses.
- Gaskets and Seals: Used in applications where oil resistance is not a critical factor.
5. Why are fillers like carbon black added to SBR during production?
Fillers are added to Styrene-Butadiene Rubber because, in its raw form, SBR has relatively low tensile strength and tear resistance. Additives like carbon black act as powerful reinforcing agents. They integrate into the polymer matrix and drastically increase its strength, hardness, abrasion resistance, and tear strength. Carbon black also provides protection against degradation from UV radiation, enhancing the overall durability of the final product.
6. What are the main disadvantages or limitations of SBR compared to natural rubber?
Despite its advantages, SBR has several limitations when compared to natural rubber. Its primary disadvantages are lower resilience and higher heat buildup during flexing, which makes it less suitable for applications like large truck tyres that generate significant heat. Additionally, SBR has poorer tensile strength and tear resistance without reinforcement and is more vulnerable to degradation from oils and solvents.
7. How does the copolymer structure of SBR influence its properties?
The structure of SBR as a copolymer is directly responsible for its unique properties. The flexible 1,3-butadiene units provide the classic rubber-like elasticity. In contrast, the bulky phenyl groups from the styrene units disrupt the polymer chain's regularity, preventing crystallization and contributing to the rubber's excellent abrasion resistance and hardness. This combination of a flexible component and a rigid component creates a balanced material that is tougher and more wear-resistant than natural rubber.
8. What is the key difference between the preparation of SBR (Buna-S) and Buna-N?
The key difference lies in the monomers used for their preparation. Both are copolymers, but:
- SBR (Buna-S) is formed by the copolymerization of 1,3-butadiene and styrene. It is primarily used for its abrasion resistance in tyres.
- Buna-N (Nitrile Rubber) is formed by the copolymerization of 1,3-butadiene and acrylonitrile. The presence of the polar nitrile group gives it excellent resistance to oils, fuels, and other chemicals, making it ideal for seals, gaskets, and fuel hoses.
