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Polybutadiene
Polybutadiene is a synthetic rubber that is a polymer formed from the polymerization process of the monomer 1,3-butadiene. Polybutadiene has a high resistance to wear and is used especially in the manufacture of tires, which consumes about 70% of the production. Another 25% is used as an additive to improve the mechanical strength of plastics such as polystyrene and acrylonitrile butadiene styrene (ABS). Polybutadiene rubber accounted for approx. a quarter of total global consumption of synthetic rubbers in 2012.〔(【引用サイトリンク】url=http://www.ceresana.com/de/marktstudien/kunststoffe/synthetischer-gummi/ )〕 It is also used to manufacture golf balls, various elastic objects and to coat or encapsulate electronic assemblies, offering high electrical resistivity.〔Heinz-Dieter Brandt, Wolfgang Nentwig, Nicola Rooney, Ronald T. LaFlair, Ute U. Wolf, John Duffy, Judit E. Puskas, Gabor Kaszas, Mark Drewitt and Stephan Glander in "Rubber, 5. Solution Rubbers" Ullmann's Encyclopedia of Industrial Chemistry, 2011, Wiley-VCH, Weinheim. 〕
== Polymerization of butadiene ==
1,3-Butadiene is an organic compound that is a simple conjugated diene hydrocarbon (dienes have two carbon-carbon double bonds). Polybutadiene forms by linking many 1,3-butadiene monomers to make a much longer polymer chain molecule. In terms of the connectivity of the polymer chain, butadiene can polymerize in three different ways, called ''cis'', ''trans'' and ''vinyl''. The cis and trans forms arise by connecting the butadiene molecules end-to-end, so-called 1,4-polymerisation. The properties of the resulting isomeric forms of polybutadiene differ. For example, "high cis"-polybutadiene has a high elasticity and is very popular, whereas the so-called "high ''trans''" is a plastic crystal with few useful applications. The vinyl content of polybutadiene is typically no more than a few percent. In addition to these three kinds of connectivity, polybutadienes differ in terms of their branching and molecular weights.
File:1,3-Butadiene Polymerization.PNG
The ''trans'' double bonds formed during polymerization allow the polymer chain to stay rather straight, allowing sections of polymer chains to align to form microcrystalline regions in the material. The ''cis'' double bonds cause a bend in the polymer chain, preventing polymer chains from aligning to form crystalline regions, which results in larger regions of amorphous polymer. It has been found that a substantial percentage of ''cis'' double bond configurations in the polymer will result in a material with flexible elastomer (rubber-like) qualities. In free radical polymerization, both ''cis'' and ''trans'' double bonds will form in percentages that depend on temperature. The catalysts influence the ''cis'' vs ''trans'' ratio.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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