?

Around this time, chemists were actively searching for rubbery materials which could be manufactured artificially. Kuzma [13] notes that the Russians, in 1910, prepared such a rubber, known chemically as polybutadiene. In the 1930s, the Germans began commercial production of a synthetic rubber called Buna-S (styrene butadiene copolymer) [14, 15]. With the outbreak of the Second World War, both the USA and Europe were extremely vulnerable to a shortage of supply of natural rubber, which could have had a catastrophic effect on the war effort. A huge R & D project was initiated, between government and industry in the United States. Styrene butadiene rubber was improved, then manufactured on a large scale and called Government Rubber-Styrene (GR-S), later to be known generically as SBR, which today is a major material in the rubber industry.

Although SBR is the most significant synthetic rubber in terms of tonnage, other rubber materials were produced around the same time, and play an important role in today’s market. A priest synthesized a chemical building block which led to the discovery of a rubber by DuPont who marketed it as Duprene [16], in 1931, then changed the name to Neoprene. Although the generic term for this material is polychloroprene (CR, chloroprene rubber) it is still most often referred to by its DuPont name. Bryant [17] points out that in 1934 production was started in Germany, of an oil resistant rubber called Buna-N, the name later changed in 1937 to Perbunan. Its generic name is nitrile rubber (NBR, nitrile butadiene rubber).

Butyl rubber (IIR, isobutylene isoprene copolymer) was developed in the 1940s. Other significant materials are Hypalon (CSM, chlorosulphonated polyethylene) and Viton (FKM, fluoroelastomer) by DuPont (now DuPont Dow Elastomers) in the 1950s and ethylene propylene terpolymer rubber (EPDM) in the 1960s. It is interesting to note that a commercially successful synthetic analogue of NR did not appear until around 1960, when it was commercialized by Shell as ‘Shell Isoprene Rubber’ and shortly after by Goodyear as Natsyn. It is chemically known as polyisoprene (IR), and while it has not in any way displaced its natural cousin, it has found a niche in the market place. An important material discovered by Bayer in the 1950s is polyurethane, which can be a coating or a rubber (and a rubbery stretch fabric), depending on its exact chemical composition (polyurethanes may have other forms such as thermoplastics and foams but these do not normally exhibit rubbery properties). A significant recent 7 addition to the armory of the rubber industry is a class of materials called thermoplastic elastomers which are gaining increasing prominence in the marketplace. They behave like rubber at room temperature but soften like plastic when heated. When cooled down, they return to their rubbery state.

The rubber that started it all, NR, has survived the onslaught of the synthetic rubbers exceptionally well and today still represents nearly one-third of all rubber in the marketplace. The new awareness of our environment gives NR the added advantage of being seen as a renewable resource, because most synthetic elastomers are derived from petroleum oil based starting materials.