From Plastics Wiki, free encyclopedia
Synthetic rubber is a type of artificially-made polymer material which acts as an elastomer. An elastomer is a material with the mechanical (or material) property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation. Synthetic rubber serves as a substitute for natural rubber in many cases, especially when improved material properties are needed.
Natural rubber coming from latex is mostly polymerized isoprene with a small percentage of impurities in it. This will limit the range of properties available to it. Also, there are limitations on the proportions of cis and trans double bonds resulting from methods of polymerizing natural latex. This also limits the range of properties available to natural rubber, although addition of sulfur and vulcanization are used to improve the properties.
However, synthetic rubber can be made from the polymerization of a variety of monomers including isoprene (2-methyl-1,3-butadiene), 1,3-butadiene, chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for cross-linking. Furthermore, these and other monomers can be mixed in various desirable proportions to be copolymerized for a wide range of physical, mechanical, and chemical properties. The monomers can be produced pure and addition of impurities or additives can be controlled by design to give optimal properties. Polymerization of pure monomers can be better controlled to give a desired proportion of cis and trans double bonds.
An urgent need for synthetic rubber that is derived from widely distributed feedstocks grew out of the expanded use of motor vehicles, and particularly motor vehicle tires, starting in the 1890s. Political problems that resulted from great fluctuations in the cost of natural rubber led to enactment of the Stevenson Act in 1921. This act essentially created a cartel which supported rubber prices by regulating production (see OPEC). By 1925 the price of natural rubber had increased to the point that companies such as DuPont were exploring methods of producing synthetic rubber to compete with natural rubber. In the case of Dupont the effort lead to the discovery of Neoprene which is a synthetic rubber that is too expensive to be used in tires, but has some very desirable properties that make it possible to use rubber in applications that would be unsuitable for natural rubber.
Uses of Synthetic Rubber
- molded: plumbing fixture; gaskets; hose; mechanical seal; mechanical belt; solid rocket propellant; tires
- sheet: Rigid-hulled inflatable boat; diving suit; glove; sleepsack; Knee high boots; protective clothing; radar absorbent material