Styrene-butadiene

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Styrene-butadiene
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Identifiers
CAS number 9003-55-8 YesY
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Styrene-butadiene or styrene-butadiene rubber (SBR) describe families of synthetic rubbers derived from styrene and butadiene (the version developed by Goodyear is called Neolite[1]). These materials have good abrasion resistance and good aging stability when protected by additives. In 2012, more than 5.4 million tonnes of SBR were processed worldwide. [2] About 50% of car tires are made from various types of SBR. The styrene/butadiene ratio influences the properties of the polymer: with high styrene content, the rubbers are harder and less rubbery.[3] SBR is not to be confused with a thermoplastic elastomer made from the same monomers, styrene-butadiene block copolymer.

Types of SBR[edit]

SBR is derived from two monomers, styrene and butadiene. The mixture of these two monomers is polymerized by two processes: from solution (S-SBR) or as an emulsion (E-SBR).[4]

Emulsion polymerization[edit]

E-SBR produced by emulsion polymerization is initiated by free radicals. Reaction vessels are typically charged with the two monomers, a free radical generator, and a chain transfer agent such as an alkyl mercaptan. Radical initiators include potassium persulfate and hydroperoxides in combination with ferrous salts. Emulsifying agents include various soaps. By "capping" the growing organic radicals, mercaptans (e.g. dodecylthiol), control the molecular weight, and hence the viscosity, of the product. E-SBR is more widely used. Typically, polymerizations are allowed to proceed only to ca. 70%, a method called "short stopping". In this way, various additives can be removed from the polymer.[3]

Solution polymerization[edit]

Solution-SBR is produced by an anionic polymerization process. Polymerization is initiated by alkyl lithium compounds. Water is strictly excluded. The process is homogeneous (all components are dissolved), which provides greater control over the process, allowing tailoring of the polymer. The organolithium compound adds to one of the monomers , generating a carbanion that then adds to another monomer, and so on. Relative to E-SBR, S-SBR is increasingly favored because it offers improved wet grip and rolling resistance, which translate to greater safety and better fuel economy, respectively.[5]

Buna S[edit]

The material was initially marketed with the brand name Buna S. Its name derives Bu for butadiene and Na for sodium (natrium in several languages including Latin, German and Dutch), and S for styrene.[6][7]

Properties[edit]

Property S-SBR E-SBR
Tensile strength (MPa) 18 19
Elongation at tear (%) 565 635
Mooney viscosity (100 °C) 48.0 51.5
Glass transition temperature (°C) -65 -50
Polydispersity 2.1 4.5

Applications[edit]

The elastomer is used widely in pneumatic tires, shoe heels and soles, gaskets and even chewing gum. It is a commodity material which competes with natural rubber. Latex (emulsion) SBR is extensively used in coated papers, being one of the cheapest 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.It is also used by speaker driver manufacturers as the material for Low Damping Rubber Surrounds.


Additionally, it is used in some rubber cutting boards.

History[edit]

SBR is a replacement for natural rubber. It was originally developed prior to World War II in Germany by chemist Walter Bock.[8] Industrial manufacture began during World War 2, and was used extensively by the U.S. Synthetic Rubber Program to produce Government Rubber-Styrene (GR-S); to replace the Southeast Asian supply of natural rubber which, under Japanese occupation, was unavailable to Allied nations.[9][10]

See also[edit]

References[edit]

  1. ^ Steven Di Pilla (2 June 2004), Slip and Fall Prevention: A Practical Handbook, CRC, p. 82, ISBN 978-0-203-49672-5 
  2. ^ Market Study Synthetic Rubber[1], published by Ceresana, June 2013
  3. ^ a b Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion Rubbers" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.o23_o01
  4. ^ International Institute of Synthetic rubber Producers, Inc. (IISRP) article on S-SBR (retrieved 2011-12-02)
  5. ^ H.-D.Brandt et al. "Rubber, 5. Solution Rubbers" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.o23_o02
  6. ^ Mark Michalovic (2000) "The Story of Rubber. Germany: The Birth of Buna" from The Polymer Learning Center and Chemical Heritage Foundation
  7. ^ Evonik Industries Invention and Production of Buna
  8. ^ Malcolm Tatum What is syrene-butadiene rubber from Wisegeek
  9. ^ Wendt, Paul (1947). "The Control of Rubber in World War II". The Southern Economic Journal (Southern Economic Association) 13 (3): 203–227. doi:10.2307/1053336. 
  10. ^ Rubber Matters: Solving the World War II Rubber Problem & Collaboration. chemheritage.org. Retrieved July 11, 2013.