Synthetic rubber, invariably a polymer, is any type of artificial elastomer mainly synthesised from petroleum byproducts. 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. About 15 billion kilograms of rubbers are produced annually, and of that amount two thirds is synthetic. Global revenues generated with synthetic rubbers are likely to rise to approximately US$56 billion in 2020. Synthetic rubber, like natural rubber, has uses in the automotive industry for tires, door and window profiles, hoses, belts, matting, flooring and dampeners (antivibration mounts).
Natural vs. synthetic rubber
Natural rubber, coming from latex of Hevea brasiliensis, is mainly poly-cis-isoprene containing traces of impurities like protein, dirt etc. Although it exhibits many excellent properties in terms of mechanical performance, natural rubber is often inferior to certain synthetic rubbers, especially with respect to its thermal stability and its compatibility with petroleum products.
Synthetic rubber is made by the polymerization of a variety of petroleum-based precursors called monomers. The most prevalent synthetic rubbers are styrene-butadiene rubbers (SBR) derived from the copolymerization of styrene and 1,3-butadiene. Other synthetic rubbers are prepared from isoprene (2-methyl-1,3-butadiene), chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for cross-linking. These and other monomers can be mixed in various proportions to be copolymerized to produce products with a range of physical, mechanical, and chemical properties. The monomers can be produced pure and the 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.
In 1879, the Frenchman Gustave Bouchardat (1842-1918) created one form of synthetic rubber, producing a polymer of isoprene in a laboratory. The expanded use of motor vehicles, and particularly motor vehicle tires, starting in the 1890s, created increased demand for rubber. In 1909, a team headed by Fritz Hofmann, working at the Bayer laboratory in Elberfeld, Germany, also succeeded in polymerizing methyl isoprene (2,3-dimethyl-1,3-butadiene), the first synthetic rubber.
The Russian scientist Sergei Vasiljevich Lebedev created the first rubber polymer synthesized from butadiene in 1910. This form of synthetic rubber provided the basis for the first large-scale commercial production, which occurred during World War I as a result of shortages of natural rubber. This early form of synthetic rubber was again replaced with natural rubber after the war ended, but investigations of synthetic rubber continued. Russian American Ivan Ostromislensky did significant early research on synthetic rubber and a couple of monomers in the early 20th century.
Political problems that resulted from great fluctuations in the cost of natural rubber led to the enactment of the Stevenson Act in 1921. This act essentially created a cartel which supported rubber prices by regulating production (see OPEC), but insufficient supply, especially due to wartime shortages, also led to a search for alternative forms of synthetic rubber.
By 1925 the price of natural rubber had increased to the point that many companies were exploring methods of producing synthetic rubber to compete with natural rubber. In the United States, the investigation focused on different materials than in Europe, building on the early laboratory work of Nieuwland.
Studies published in 1930 written independently by Lebedev, the American Wallace Carothers and the German scientist Hermann Staudinger led in 1931 to one of the first successful synthetic rubbers, known as neoprene, which was developed at DuPont under the direction of E.K. Bolton. Neoprene is highly resistant to heat and chemicals such as oil and gasoline, and is used in fuel hoses and as an insulating material in machinery. The company Thiokol applied their name to a competing type of rubber based on ethylene dichloride which was commercially available in 1930.
The first rubber plant in Europe SK-1 (from Russian "Synthetic Kauchuk", Russian: СК-1) was established (Russia) by Sergei Lebedev in Yaroslavl under Joseph Stalin's First Five-Year Plan on July 7, 1932.
In 1935, German chemists synthesized the first of a series of synthetic rubbers known as Buna rubbers. These were copolymers, meaning the polymers were made up from two monomers in alternating sequence.
World War II
B.F. Goodrich Company scientist Waldo Semon developed a new and cheaper version of synthetic rubber known as Ameripol in 1940. Ameripol made synthetic rubber production much more cost effective, helping to meet the country's needs during World War II.
The production of synthetic rubber in the United States expanded greatly during World War II, since the Axis powers controlled nearly all the world's limited supplies of natural rubber by mid-1942 once Japan conquered Asia. Military trucks needed rubber for tires, and rubber was used in almost every other war machine. The U.S. government launched a major (and largely secret) effort to improve synthetic rubber production. A large team of chemists from many institutions were involved, including Calvin Souther Fuller of Bell Labs. The rubber designated GRS (Government Rubber Styrene), a copolymer of butadiene and styrene, was the basis for U.S. synthetic rubber production during World War II. By 1944, a total of 50 factories were manufacturing it, pouring out a volume of the material twice that of the world's natural rubber production before the beginning of the war. It still represents about half of total world production.
Operation Pointblank bombing targets of Nazi Germany included the Schkopau (50K tons/yr) plant and the Hüls synthetic rubber plant near Recklinghausen (30K, 17%), the Kölnische Gummifäden Fabrik tire and tube plant at Deutz on the east bank of the Rhine. The Ferrara, Italy, synthetic rubber factory (near a river bridge) was bombed August 23, 1944. Three other synthetic rubber facilities were at Ludwigshafen/Oppau (15K), Hanover/Limmer (reclamation, 20K), and Leverkusen (5K). A synthetic rubber plant at Oświęcim in Nazi-occupied Poland, was under construction on March 5, 1944.
Table of common synthetic rubbers
|ISO 1629 Code||Technical Name||Common Names|
|BIIR||Bromo Isobutylene Isoprene||Bromobutyl|
|CIIR||Chloro Isobutylene Isoprene||Chlorobutyl, Butyl|
|ECO||Epichlorohydrin||ECO, Epichlorohydrin, Epichlore, Epichloridrine, Herclor, Hydrin|
|EPDM||Ethylene Propylene Diene Monomer||EPDM, Nordel|
|FKM||Fluoronated Hydrocarbon||Viton, Kalrez, Fluorel, Chemraz|
|FMQ||Fluoro Silicone||FMQ, Silicone Rubber|
|HNBR||Hydrogenated Nitrile Butadiene||HNBR|
|IR||Polyisoprene||(Synthetic) Natural Rubber|
|IIR||Isobutylene Isoprene Butyl||Butyl|
|NBR||Acrylonitrile Butadiene||NBR, Nitrile rubber, Perbunan, Buna-N|
|SBR||Styrene Butadiene||SBR, Buna-S, GRS, Buna VSL, Buna SE|
|SEBS||Styrene Ethylene Butylene Styrene Copolymer||SEBS Rubber|
|VMQ||Vinyl Methyl Silicone||Silicone Rubber|
|XNBR||Acrylonitrile Butadiene Carboxy Monomer||XNBR, Carboxylated Nitrile|
|XSBR||Styrene Butadiene Carboxy Monomer|
|YSBR||Styrene Butadiene Block Copolymer|
|YXSBR||Styrene Butadiene Carboxy Block Copolymer|
In addition the term gum rubber is sometimes used to describe the tree-derived natural rubber (code NR), and to distinguish it from synthetic natural rubber (code IR).
- Desmond Threadingham, Werner Obrecht, Wolfgang Wieder, Gerhard Wachholz and Rüdiger Engehausen "Rubber, 3. Synthetic Rubbers, Introduction and Overview" in Ullmann's Encyclopedia of Industrial Chemistry, 2011, Weinheim. doi:10.1002/14356007.a23_239.pub5
- Ceresana, Market Study Synthetic Rubber, June 2013, http://www.ceresana.com/en/market-studies/plastics/synthetic-rubber/
- The Moving Powers of Rubber, Leverkusen, Germany: LANXESS AG: 20.
- The Story of Rubber - Destination Germany: A Poor Substitute
- Current Biography 1940, "SEMON, WALDO LONSBURY" pp723-24
- Stormont, John W. (March 1946) [summer of 1945], AAFRH-19: The Combined Bomber Offensive; April through December 1943, Dwight D. Eisenhower Presidential Library: Collection of 20th Century Military Records, 1918–1950 Series I: Historical Studies Box 35: AAF Historical Office; Headquarters, Army Air Force, pp. 74–5, 81, "SECRET ... Classification Cancelled ... JUN 10 1959"
- Gurney, Gene (Major, USAF) (1962), The War in the Air: a pictorial history of World War II Air Forces in combat, New York: Bonanza Books, p. 215
- Williamson, Charles C.; Hughes, R. D.; Cabell, C. P.;Nazarro, J. J.; Bender, F. P.; & Crigglesworth, W. J. (5 March 1944), Plan for Completion of Combined Bomber Offensive (Appendices C & F), Dwight D. Eisenhower Presidential Library: SMITH, WALTER BEDELL: Collection of World War II Documents, 1941–1945; Box No.: 48: HQ, U.S.S.T.A.F, "DECLASSIFIED ... 4/24/74"