Styrene Butadiene Rubber is a popular general-purpose rubber that is known for its low cost and high abrasion resistance. After natural rubber supplies were cut off in the 1930s, Scientists invented SBR, which has since been a staple of the automotive and industrial sectors. In this article, we’ll go through the fundamentals of SBR rubber, such as its composition, properties and applications.
WHAT IS STYRENE BUTADIENE RUBBER?
Styrene Butadiene Rubber is the most commonly used synthetic rubber, replacing natural rubber in many applications. SBR is a general-purpose rubber made up of a copolymer of 75 per cent styrene and 25 percent butadiene.
The term copolymer refers to when the molecules of two different materials combine to form a single molecule of several units. The addition of styrene reduces the cost of SBR while increasing bonding and blending capabilities.
SBR’s wear and abrasion resistance and its resilience are all due to the styrene.
APPLICATIONS OF SBR
The bulk of SBR is used in automotive tyres and parts for light applications. It is used in decreasing proportions in car tyres due to its inferior heat resistance to natural rubber. Airplane tyres, for example, are made entirely of natural rubber and require greater heat resistance.
Cold emulsion SBR is more widely used in lighter duty tyres, while solution SBR is more commonly used in specialized applications, such as radial car tyres and motorcycle treads, due to its higher cost.
Automotive components, such as drive couplings, are often made of SBR. Because of its abrasion resistance, SBR can be used in industrial applications such as belting, wire and cable insulation, haul-off pads, roll coverings, hoses, gaskets, seals and coated fabrics, in addition to automotive applications.
Because of its metal adhesion and abrasion resistance, SBR is widely used for rubber gaskets. Styrene Butadiene Rubber is used in consumer items such as shoe soles, carpet backing adhesive, and molded rubber goods.
PROPERTIES OF SBR
Because of its low cost and widespread availability, SBR rubber is widely used, despite its high tensile and impact strength, toughness and abrasion resistance.
It has good heat resistance and is flexible in low temperatures. Air, organic acid, ketones, chemicals, alcohol, and aldehyde are all immune to SBR.
This form of rubber also ages better than natural rubber and is more resistant to cracking while allowing for large quantities of filler to improve its properties.
However, without fillers, Styrene Butadiene Rubber is one of the weaker rubbers. Ozone, oxidation, fatigue, solvent and weathering are all threats to this form of rubber.
It also has poor tear strength and durability when compared to natural rubber, particularly at high temperatures. SBR, like natural rubber, swells and weakens when exposed to hydrocarbon oils.
STRUCTURE OF SBR
SBR is a mixture of butadiene (CH2=CH-CH=CH2) and styrene (CH2=CHC6H5) that contains about 75% butadiene and 25% styrene. In most cases, these two compounds are copolymerized, their single-unit molecules are connected to form long, multiple-unit molecules in an emulsion phase, which involves dispersing or emulsifying the materials in a water solution with a soaplike surface acting agent.
Free radical initiators, which start the polymerization process, and stabilizers, which keep the finished product from deteriorating, are among the other materials in the solution.
The repeating units of styrene and butadiene are randomly arranged along the polymer chain after polymerization. During the vulcanization process, the polymer chains are cross-linked.
There are two major forms of Styrene Butadiene Rubber on the market today, each with its unique properties based on the manufacturing process:
Emulsion SBR is rapidly gaining popularity, with hot and cold manufacturing methods that alter the rubber’s properties. Emulsion SBR has strong abrasion resistance and performs better at lower temperatures.
However, it has poor tensile strength and durability. The branching polymer in hot emulsion SBR is higher than in cold emulsion SBR, making it ideal for extrusion, more stable, and less shrinkable.
Cold emulsion SBR has higher tensile strength and is more abrasion-resistant.
With a higher molecular weight and a smaller molecular weight distribution, solution SBR still accounts for roughly 75 per cent of all SBR made.
This material is more expensive than emulsion SBR, but it has higher stability and tensile strength and lowers rolling resistance.
ADVANTAGES AND DISADVANTAGES OF SBR
Rubber made of styrene-butadiene has a variety of advantages. Because of its similar properties and lower cost, it is used as a direct substitute for natural rubber. Rubber made of styrene butadiene has outstanding abrasion resistance and crack endurance.
It also holds up well over time, has a strong compression, and is water-resistant. SBR’s beneficial strength, abrasion, and bonding properties and its affordability are due to the addition of the organic compound styrene.
The low sunlight and ozone tolerance of SBR is some of its major drawbacks. As a result, it’s less useful in outdoor applications. SBR rubber is also susceptible to oil and steam, which cause it to swell and weaken over time.
The tensile and abrasion strength of styrene butadiene rubber can only be achieved with reinforcement, such as a filler like carbon black. Chemicals, ozone, heavy acids, greases, fats, and other hydrocarbons are not compatible with SBR rubber.
We hope you can use this knowledge to source more efficiently for your needs, now that we have covered the basics of SBR rubber, such as what it is, its properties and its applications.
However, Styrene Butadiene is only one of the several common types of rubbers, each with its own set of characteristics and applications.
Check out our types of rubber guide if you want to learn more about how different rubbers compare to one another or follow us on social media to stay updated