BDS Butadiene Styrene block copolymers

BDS (SB has also been used but is not recommended as the same initials have been used for HIPS. SBB standing for styrene butadiene block copolymer would be better). 

Styrene and butadiene can be put together in various ways so as to produce a wide range of rubbers and plastics. A en each is polymerized on its own then homopolymers are produced, for example, polystyrene and polybutadiene. When styrene is polymerized onto polybutadiene then the graft copolymer, TPS may be produced. If the two monomers are polymerized together then the random copolymer known as styrene butadiene rubber (SBR) is obtained this contains approximately 75% styrene and 25% butadiene. 

if 75% styrene and 25% butadiene are polymerized together in a different way then, a totally different material results it is a plastic rather than a rubber. This is done by sequential, anionic polymerization in solution. As a result a material is produced which contains long lengths (or blocks) of polystyrene and long lengths (or blocks) of polybutadiene may contain up to, for example, six blocks. The molecules of the final plastic are star shaped as the initial multiblocks are coupled together by a polyfunctional material, for example, epoxidised linseed oil. (Because of the polymerization technique employed, plastics with a narrow molecular weight distribution may be produced if required). 

After the formation of the star-shaped blocks there is a phase separation of the polystyrene and the polybutadiene into domains or regions the links between the two phases are 

A relatively easy flow material, for example, similar to a medium flow TPS. As with other plastics raising the temperature eases flow but care should be taken as above, approximately, 250° C (482° F) the rubber will start to crosslink, ease of flow will decrease and the moldings will appear hazy. This crosslinking can also occur at lower temperatures if the material is kept at that temperature for too long a time period. 

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