Styrene-Butadiene Rubber Definition
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
1. What are the Fillers that are Added during the Production of SBR as Additives?
Ans: The key classes of fillers that are added during the process include:
Carbon black: It is obtained in a colloidal carbon form. This happens through the decomposition of hydrocarbons. This leads to:
Increase in tensile strength. This is followed by resistance in tearing and abrasion.
Protection is provided from UV radiation.
China clays: Its reinforcement is less as compared to carbon black. It is mainly used for non-black applications.
Calcium carbonate: This filler is non-reinforcing. It is mainly added for cost reduction.
Silica: It serves functions of both reinforcement and non-reinforcement.
Steel and fibreglass also play the role of reinforcements.
2. What are the Limitations in the Properties of SBR?
Ans: Without fillers, SBR Styrene Butadiene Rubber is one of the weakest forms of rubbers. This makes it vulnerable to oxidation, fatigue, ozone, weathering and solvents.
When compared with nature, SBR has bad tear strength and low resilience, especially with high temperatures. Just like natural rubber, the addition of hydrocarbon oils swells it up and makes it weaker.
