SBR, or Styrene-butadiene rubber, is the most consumed synthetic rubber, widely used in place of natural rubber for similar applications. SBR is a general purpose rubber made up of 75% styrene and 25% butadiene joined in a co-polymer. The co-polymer means the molecules of these two materials connect into combined molecules with multiple units. The styrene added makes SBR cheaper while adding bonding and blending capabilities. The styrene also lends SBR its wear and abrasion resistance, as well as its strength.
SBR is produced in two different ways- through emulsion and solution, which lend it different properties.
- Emulsion SBR is quickly growing in popularity, with both hot and cold production types that change the properties of the rubber. Overall, however, emulsion SBR has good abrasion resistance while functioning better at lower temperatures. However, it also has low resilience, tensile strength, and tear strength.
- Hot emulsion SBR has more of a branching polymer than cold emulsion SBR, which makes it better for extrusion, more stable, and less shrinkable.
- Cold emulsion SBR is more abrasion resistant and has more tensile strength.
- Solution SBR still makes up roughly 75% of all SBR produced, with a higher molecular weight and a smaller molecular weight distribution. This material has better flexibility and tensile strength with lower rolling resistance than emulsion SBR, and is also more expensive
