Styrene-butadiene
Encyclopedia
Styrene-Butadiene or Styrene-Butadiene-Rubber (SBR) is a synthetic rubber
copolymer consisting of styrene and butadiene. It has good abrasion resistance and good aging stability when protected by additives, and is widely used in car tires, where it may be blended with natural rubber. It was originally developed prior to World War II
in Germany, but during the War was used extensively by the USA to replace natural rubber supplies from the far-east, that had been captured by the Japanese.
SBR can be produced by two basically different processes ; (a) from solution or (b) as emulsion. In the first instance the reaction is ionic polymerisation, in the emulsion polymerization case the reaction is via free radical polymerization. In that process; Low pressure reaction vessels are required and usually charged with styrene and butadiene, the two monomers, a free radical generator and a chain transfer agent such as an alkyl mercaptan and water. Mercaptans controls molecular weight and high viscosity product from forming. The anionic polymerization process is initiated by alkyl lithium and water not involved. High styrene content rubbers are harder but less rubbery.
It is not to be confused with a thermoplastic elastomer
made from the same monomers, styrene-butadiene block copolymer.
(natrium in several languages including Latin, German and Dutch), and S for styrene.
is used widely in pneumatic tire
s, shoe heels and soles, gasket
s and even chewing gum
. It is a commodity material which competes with natural rubber. Latex (emulsion) SBR is extensively used in coated paper
s, being one of the most cost-effective resins to bind pigmented coatings. It is also used in building applications, as a sealing and binding agent behind renders as an alternative to PVA, but is more expensive. In the latter application, it offers better durability, reduced shrinkage and increased flexibility, as well as being resistant to emulsification in damp conditions. SBR can be used to 'tank' damp rooms or surfaces, a process in which the rubber is painted onto the entire surface (sometimes both the walls, floor and ceiling) forming a continuous, seamless damp proof liner; a typical example would be a basement.
Additionally, it is used in some rubber cutting boards.
Synthetic rubber
Synthetic rubber is is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation...
copolymer consisting of styrene and butadiene. It has good abrasion resistance and good aging stability when protected by additives, and is widely used in car tires, where it may be blended with natural rubber. It was originally developed prior to World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
in Germany, but during the War was used extensively by the USA to replace natural rubber supplies from the far-east, that had been captured by the Japanese.
SBR can be produced by two basically different processes ; (a) from solution or (b) as emulsion. In the first instance the reaction is ionic polymerisation, in the emulsion polymerization case the reaction is via free radical polymerization. In that process; Low pressure reaction vessels are required and usually charged with styrene and butadiene, the two monomers, a free radical generator and a chain transfer agent such as an alkyl mercaptan and water. Mercaptans controls molecular weight and high viscosity product from forming. The anionic polymerization process is initiated by alkyl lithium and water not involved. High styrene content rubbers are harder but less rubbery.
It is not to be confused with a thermoplastic elastomer
Thermoplastic elastomer
Thermoplastic elastomers , sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers which consist of materials with both thermoplastic and elastomeric properties...
made from the same monomers, styrene-butadiene block copolymer.
Buna S
The material was initially marketed with the brand name Buna S. It derives this name from: Bu for butadiene, Na for sodiumSodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
(natrium in several languages including Latin, German and Dutch), and S for styrene.
Properties
- Glass transition temperature approximately -55 °C, but varies with styrene content
- Possible temperature range of use: approximately -40 C
- Chemical Type: styrene-butadiene (copolymer)
- Trade names (common): GRS, Buna S, SBR
- Elongation (%): 450-500
- Shore A hardnessShore durometerDurometer is one of several measures of the hardness of a material. Hardness may be defined as a material's resistance to permanent indentation. The durometer scale was defined by Albert F. Shore, who developed a measurement device called a durometer in the 1920s. The term durometer is often used...
: 50-90 - Major application characteristics: good physical properties; excellent abrasion resistance; but sensitive to oil, wastewater and ozoneOzoneOzone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
; electrical properties good, but not outstanding
Applications
The elastomerElastomer
An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...
is used widely in pneumatic tire
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
s, shoe heels and soles, gasket
Gasket
thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...
s and even chewing gum
Chewing gum
Chewing gum is a type of gum traditionally made of chicle, a natural latex product, or synthetic rubber known as polyisobutylene. For economical and quality reasons, many modern chewing gums use rubber instead of chicle...
. It is a commodity material which competes with natural rubber. Latex (emulsion) SBR is extensively used in coated paper
Coated paper
Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...
s, being one of the most cost-effective resins to bind pigmented coatings. It is also used in building applications, as a sealing and binding agent behind renders as an alternative to PVA, but is more expensive. In the latter application, it offers better durability, reduced shrinkage and increased flexibility, as well as being resistant to emulsification in damp conditions. SBR can be used to 'tank' damp rooms or surfaces, a process in which the rubber is painted onto the entire surface (sometimes both the walls, floor and ceiling) forming a continuous, seamless damp proof liner; a typical example would be a basement.
Additionally, it is used in some rubber cutting boards.