Natural rubber sources

Prior to 1940, the use of synthetic elastomers in linings was negligible, but the advent of the Second World War, and the consequent loss of natural rubber sources to the Allies, led to the use of synthetic rubber, namely a styrene-butadiene copolymer which, whilst not having all the properties of natural rubber, proved to have adequate anti-corrosive performance. 

Natural rubber is a polymer of isoprene- most often cis-l,4-polyiso-prene - with a molecular weight of 100,000 to 1,000,000. Typically, a few percent of other materials, such as proteins, fatty acids, resins and inorganic materials is found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber". Owing to the presence of a double bond in each and every repeat unit, natural rubber is sensitive to ozone cracking. Some natural rubber sources called gutta percha are composed of trans-1,4-poly isoprene, a structural isomer which has similar, but not identical properties. Natural rubber is an elastomer and a thermoplastic. However, it should be noted that as the rubber is vulcanized it will turn into a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both, i.e., if it is heated and cooled, it is degraded but not destroyed. 

Guajule An Alternative Source of Natural Rubber, National Academy of Sciences, Washington, D.C., 1977. 

In 1942 the Japanese overran Malaya and the then Dutch East Indies to cut off the main sources of natural rubber for the United States and the British Commonwealth. Because of this the US Government initiated a crash programme for the installation of plants for the manufacture of a rubber from butadiene and styrene. This product, then known as GR-S (Government Rubber-Styrene), provided at that time an inferior substitute for natural rubber but, with a renewed availability of natural rubber at the end of the war, the demand for GR-S slumped considerably. (Today the demand for SBR (as GR-S is now known) has increased with the great improvements in quality that have been made and SBR is today the principal synthetic rubber). 

An alternative source of the frani-1,4-polyisoprene is balata, obtained from Mimosups balata, occurring in Venezuela, Barbados and Guyana. The latex is thin and may be tapped in the same way as natural rubber. 

Natural rubber can be obtained from the sap of a number of plants and trees, the most common source is the Hevea brasiliensis tree. Although natural rubber was known in Central and South America before the arrival of Christopher Columbus in 1492, the first use as an adhesive was established in a patent dated in 1891. As rubber became an important part of the industrial revolution, the rubber adhesives market grew in importance. To comply with the increasing demand on natural rubber materials, plantations of Hevea brasiliensis trees were established in southeast Asia in the early 20th Century, mainly to supply the demand from the automobile industry. 

The rubber industry has a long and colorful history. Natural rubber is produced from latex, a milky fluid found in cells that lie between the bark and the wood of many plants. You may have seen latex flow from the broken stalks of milkweed plants, but the source of commercial rubber is the Hevea tree, a native of Brazil. When the bark of this tree is slashed, its milky white sap oozes out and can be collected in cups mounted on the tree s trunk. The people of the Amazon jungle made bouncing balls, shoes, and water Jars out of rubber, and Portuguese explorers sent waterproof boots and a rubber-coated coat back to their king. The first commercial exports included some rubber shoes shipped to Boston in 1823. 

Rubber obtained from botanical sources. The bulk of natural rubber is obtained from the Hevea Brasiliensis free with small amounts from other vines, shrubs and plants mainly the Guayule shrub and the Kok-Saghyz plant. See Isoprene. 

A convenient term for any material possessing the properties of a rubber but produced from other than natural sources. A synthetic version of natural rubber has been available for many years with the same chemical formula, i.e., cis-1,4-polyisoprene, but it has not displaced the natural form. See also Butyl Rubber, Chloroprene Rubber, Ethylene-Propylene Rubber, Nitrile Rubber, Silicone Rubber and Styrene-Butadiene Rubber. 

Synthetic rubber(s), 1 693, 21 761. See Ethylene-propylene polymers. See also Butyl rubber acetylene-derived sources, 1 228 synthesis of first butyl rubber after disruption of natural rubber supply in WW II, 4 433... 

Renewable raw materials are made or derived from short-term renewable sources (one to a few years or a few tens of years) such as plants, trees, wood wastes and other agricultural products. Not all these materials are necessarily biodegradable. Natural rubber, for example, comes from the latex of a tree (Hevea brasiliensis) and is not biodegradable. Renewable materials are often considered as opposites to fossil sources such as petroleum that are not renewable on a human timescale. On the other hand, some synthesized plastics such as certain polyesters are biodegradable. 

During World War II, the Japanese cut ofFU.S. access to sources of natural rubber, giving the Americans a strategic imperative to develop and expand the manufacture of synthetic rubber. The C4 streams in refineries were a direct source of butadiene, the primary synthetic rubber feedstock. As a coincidence, the availability of this stream was growing rapidly with the expansion of catalytic cracking to meet wartime gasoline needs. Additional butadiene was manufactured by dehydrogenation of butane and butylene also. 

Figure 18.1 U.S. consumption of natural rubber vs. SBR production. Source Chemical and Engineering News and Chemical Economic Handbook)...

Emulsion polymerization was first employed during World War II for producing synthetic rubbers from 1,3-butadiene and styrene. This was the start of the synthetic rubber industry in the United States. It was a dramatic development because the Japanese naval forces threatened access to the southeast Asian natural-rubber (NR) sources, which were necessary for the war effort. Synthetic mbber has advanced significantly from the first days of balloon tires, which had a useful life of 5000 mi to present-day tires, which are good for 40,000 mi or more. Emulsion polymerization is presently the predominant process for the commercial polymerizations of vinyl acetate, chloroprene, various acrylate copolymerizations, and copolymerizations of butadiene with styrene and acrylonitrile. It is also used for methacrylates, vinyl chloride, acrylamide, and some fluorinated ethylenes. 

Field latex and field coagulum are the source materials for all varieties and grades of dry natural rubber that include the conventional International grades as well as the Technically Specified Rubbers (TSR). 

Starch has been considered an attractive raw material for polymer applications for almost 200 years. Kirchoff s discovery in 1811 that treatment of starch with an acid yields a sweet substance was an unexpected result of the search for a low-cost substitute for natural rubber.1 Considerable research in the development of starch-based polymer materials has been stimulated by the facts that starch is produced from wide variety of sources, is an annually renewable resource and is inherently biodegradable. 

World War II brought a renewed urgency for synthetic rubber. When the Japanese occupied the Malay Peninsula and adjacent islands, the primary source of natural rubber to the United States was cut off. Rubber companies and university scientists cooperated in developing a procedure for manufacturing a synthetic rubber called GR-S (Government Rubber—Styrene). By the late 1930s,... 

Faraday discovered in 1826 that natural rubber was composed of a hydrocarbon with a ratio of five carbons to eight hydrogen atoms and in 1860, G. Williams isolated isoprene by collecting the distillate from the heating of natural rubber. By 1887, scientists in France, England, and Germany had converted isoprene back into a rubbery material. Because this offered a potential for manufactured natural rubber, research was undertaken to find ways to obtain isoprene from sources other than rubber itself.21... 

Because of Germany s isolation from adequate sources of petroleum and natural rubber, she had already converted much of her industry during World War One to use coal as a substitute source of hydrocarbons for making synthetic liquid fuels as well as a vast assortment of chemical substances, including synthetic rubber. Millions of tons of carbon monoxide were produced as part of this technology and would have been more than enough to kill the entire population of Europe many times over. 

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