What is SBS Rubber?

SBS rubber

Poly(styrene-butadiene-styrene), or SBS, is a hard rubber that's used for things like shoe soles, tire treads, and other places where durability is important. It's a type of copolymer called a block copolymer. Its backbone chain is made up of three segments. The first is a long chain of polystyrene, the middle is a long chain of polybutadiene, and the last segment is another long section of polystyrene, as shown below.

SBS block copolymer

Polystyrene is a tough hard plastic, and this gives SBS its durability. Polybutadiene is rubbery, and this gives SBS its rubber-like properties. Additionally, the polystyrene chains tend to clump together. When one styrene group of one SBS molecule joins one clump, and the other polystyrene chain of the same SBS molecule joins another clump, the different clumps become tied together with rubbery polybutadiene chains. This gives the material the ability to retain its shape after being stretched.

SBS is made with the chemistry called living anionic polymerization.

SBS is also a type of unusual material called a thermoplastic elastomer. These are materials that behave like elastomeric rubbers at room temperature, but can be processed like plastics when heated. Most types of rubber are difficult to process because they are crosslinked. However, SBS and other thermoplastic elastomers manage to be rubbery without being crosslinked, making them easy to process into nifty useful shapes.

(This article is reproduced from The Macrogalleria.)