Styrene-butadiene

Styrene-Butadiene (SBR) is an elastomeric copolymer consisting of styrene and butadiene. It has good abrasion resistance and good ageing stability when protected by additives, and is widely used in car tires where it is blended with natural rubber. It was originally developed in the USA during World War II to replace natural rubber supplies from the far east that were captured by the Japanese.

Styrene-Butadiene Monomer

SBR can be produced from solution or as emulsion. In both instances, the reaction is via free radical polymerization. Pressure reaction vessels are required and usually charged with the two monomers, a free radical acid and a chain transfer agent such as an alkyl mercaptan. The latter prevents high molecular weight and high viscosity product from forming. High styrene-content rubbers are hard, since the Tg (glass transition temperature)of butadiene is extremely low.

Properties

• Glass transition temperature approx. -55 °C [1] but varies with styrene content
• Possible temperature range of use: approx. -40 to +100 °C (-40 to +212 °F)
• Chemical Type: styrene-butadiene (copolymer)
• Trade names (common): GRS, Buna S (SBR)
• Elongation (%): 450-500
• Useful temperature range: -60 to 120 degrees Celsius (-75 to 250 degrees Fahrenheit)
• Major application characteristics: good physical properties; excellent abrasion resistance; but sensitive to oil, and ozone; electrical properties good, but not outstanding

Applications

The elastomer is used widely in pneumatic tires, shoe heels and soles and gaskets. It is a commodity material which competes with natural rubber. Latex (emulsion) SBR is extensively used in coated papers, being one of the most cost-effective resins to bind pigmented coatings.

Also see

• elastomer
• ozone cracking
• tyre

References

[1] Gent, A. N.; Campion, R. P.; American Chemical Society.Division of Rubber Engineering With Rubber : How to Design Rubber Components; Munich : Hanser Publishers: 1992.