Styrene-butadiene
1,3-butadiene -styrene copolymer
Fixed
Styrene -butadiene rubber is the raw material for the by far the most produced variant of synthetic rubber, in 2012 approximately 5.4 million tons are consumed worldwide. Its abbreviation is SBR, derived from the English name " Styrene Butadiene Rubber". It is a copolymer of 1,3- butadiene and styrene. His production for the first time in 1929 the German chemist Walter Bock using the emulsion polymerization. Thus, it was the first commercially viable synthetic rubber. SBR is now the most widely used synthetic rubber and finds application particularly in the manufacture of tires, gaskets and conveyor belts.
SBR typically contains 23.5% styrene and 76.5 % butadiene. With higher styrene content, the rubber is a thermoplastic, but remains curable.
For large-scale production, the emulsion is applied at 5 ° C, which is therefore also referred to as cold polymerization. Warmpolymerisation at about 50 ° C results in branched molecular chains that make the rubber gained less elastic. For elastic even at low temperatures of winter rubber tire contrast solution is used. Radical polymerization is also possible, but is not yet applied on a large scale. After polymerization, the SBR is crosslinked by means of vulcanization and thereby receives its final form.
Under the name of Buna -S SBR should make the German war economy (1939-1945) independently as part of the home textile policy on the import of natural rubber.
Properties
SBR shows good stability and little swelling in inorganic and organic acids and bases, as well as alcohols and water. It is resistant to brake fluid, but is usually replaced here by EPDM.
It is, however, strongly swelling in aliphatics, aromatics and chlorinated hydrocarbons, particularly in mineral oil, grease and gasoline.
Against weather influences it is more stable than natural rubber, however, inferior to, for example, chloroprene rubber (CR) and ethylene-propylene -diene rubber (EPDM).
Operating temperature range: -40 ° C to 70 ° C.