Styrene butadiene rubber (SBR) is one of the cheaper synthetic general purpose elastomers that is sometimes used as a substitute for natural rubber (NR). It can be produced by free-radical solution polymerization or by emulsion polymerization either warm at 30 to 60°C (hot rubber) or cold at temperatures near 0°C (cold rubber). Emulsion SBR (ESBR) continues to lose ground to solution SBR (SSBR) which is better suited for high-performance tires. Nevertheless, emulsion SBR grades still account for more than 75% of the total world capacity as of 2015. However, more and more SBR is produced by solution polymerization. SBR is a highly random copolymer of butadiene and 10 to 25 percent styrene.
The addition of styrene lowers the price and contributes to the good wear and bonding properties. The addition of styrene also improves the strength, abrasion resistance, and blend properties of polybutadiene.
The fatigue resistance and low temperature properties of SBR are usually inferior to natural rubber, whereas its heat-aging properties and abrasion resistance are better. Like natural rubber, SBR is vulnerable to thermal and oxidative degradation due to the presence of double bonds in the polydiene backbone. Degradation generally occurs through cross-linking, which leads to an increase in stiffness (embrittlement).
SBR also has poor chemical resistance, that is, its solvent resistance and weathering properties are inferior to most other elastomers.
COMMERCIAL SBR ELASTOMERS
Some major manufacturers of SBR rubbers are Firestone, Dynasol, Eni, Asahi-Kasei, LG Chem, GoodYear, JSR, and Lanxess.
Styrene butadiene rubber (SBR) is the highest volume general purpose synthetic rubber. It can be used in similar applications as NR / IR elastomers, except in severe dynamic application due to the inferior fatigue resistance. Typical applications include drive couplings, haul-off pads, conveyor belts, shoe soles and heels, adhesives, roll coverings and car tires (but not truck tires) and various other molded rubber goods. The typical working temperature range is -25°C to +100°C for static sealing.