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Rubber

Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. The major commercial source of the latex used to create rubber is the Para rubber tree, Hevea brasiliensis (Euphorbiaceae). This is largely because it responds to wounding by producing more latex. Other plants containing latex include figs (Ficus elastica), euphorbias, and the common dandelion. Although these have not been major sources of rubber, Germany attempted to use such sources during World War II when it was cut off from rubber supplies. These attempts were latter supplanted by the development of synthetic rubber. Its density is 920 kg/m.

     In places like Kerala, where coconuts are in abundance, the shell of half a coconut is used as the collection container for the latex. The shells are attached to the tree via a short sharp stick and the latex drips down into it overnight. This usually produces latex up to a level of half to three quarters of the shell. The latex from multiple trees are then poured into flat pans and this is mixed with formic acid, which serves as a coagulant. After a few hours, the very wet sheets of rubber are wrung out by putting them through a press before they are sent onto factories where vulcanization and further processing is done. Aside from a few natural product impurities, natural rubber is essentially a polymer of isoprene units, a hydrocarbon diene monomer. Synthetic rubber can be made as a polymer of isoprene or various other monomers. Rubber is believed to have been named by Joseph Priestley, who discovered in 1770 that dried latex rubbed out pencil marks. The material properties of rubber make it an elastomer

History

In its native Central America and South America, rubber has been collected for a long time. The Mesoamerican civilizations used rubber mostly from Castilla elastica. The Ancient Mesoamericans had a ball game using rubber balls (see: Mesoamerican ballgame), and a few Pre-Columbian rubber balls have been found (always in sites that were flooded under fresh water), the earliest dating to about 1600 BC. According to Bernal Daz del Castillo, the Spanish Conquistadores were so astounded by the vigorous bouncing of the rubber balls of the Aztecs that they wondered if the balls were enchanted by evil spirits. The Maya also made a type of temporary rubber shoe by dipping their feet into a latex mixture. Rubber was used in various other contexts, such as strips to hold stone and metal tools to wooden handles, and padding for the tool handles. While the ancient Mesoamericans did not have vulcanization, they developed organic methods of processing the rubber with similar results, mixing the raw latex with various saps and juices of other vines, particularly Ipomoea alba, a species of Morning glory. In Brazil the natives understood the use of rubber to make water-resistant cloth. A story says that the first European to return to Portugal from Brazil with samples of such water-repellent rubberized cloth so shocked people that he was brought to court on the charge of witchcraft.

When samples of rubber first arrived in England, it was observed that a piece of the material was extremely good for rubbing out pencil marks on paper. This was the origin of the material's English name of 'rubber'. Blocks of the material are still used for this purpose, and known as 'rubbers' in British English, causing occasional amusement to speakers of American English, to whom a 'rubber' is a condom (usually made from latex). (American English uses 'eraser' to refer to the rubber block.)The para rubber tree initially grew in South America, where it was the main source of what limited amount of latex rubber was consumed during much of the 19th century. About 100 years ago, the Congo Free State in Africa was a significant source of natural rubber latex, but after repeated efforts it was successfully cultivated in Southeast Asia, where it is now widely grown.

Current sources of rubber

Today Asia is the main source of natural rubber. Over half of the rubber used today is synthetic, but several million tonnes of natural rubber are still produced annually, and is still essential for some industries, including automotive and military. Hypoallergenic rubber can be made from Guayule. Early experiments in the development of synthetic rubber led to the invention of Silly Putty. Natural rubber is often vulcanized, a process by which the rubber is heated and sulfur is added to improve resilience and elasticity. The process of vulcanization greatly improved the durability and utility of rubber from the 1830s on. The successful development of vulcanisation is most closely associated with Charles Goodyear. Carbon black is often used as an additive to rubber to improve its strength, especially in vehicle tires.Rubber as a clothing material is fetishized by some people, perhaps on the basis that the garment forms a "second skin" that acts as a surrogate for the wearer's own skin. This is known as rubber fetishism
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Brief History of Rubber (based on Wade Davis, One River 1996)

Rubber is one of the most important products to come out of the rainforest. Though indigenous rainforest dwellers of South America have been using rubber for generations, it was not until 1839 that rubber had its first practical application in the industrial world. In that year, Charles Goodyear accidentally dropped rubber and sulfur on a hot stovetop, causing it to char like leather yet remain plastic and elastic. Vulcanization, a refined version of this process, transformed the white sap from the bark of the Hevea tree into an essential product for the industrial age.

With the invention of the automobile in the late 19th century, the rubber boom began. As demand for rubber soared small dumpy river towns like Manaus, Brazil, were transformed into over night into bustling centers of commerce. Manaus, situated on the Amazon where it is met by the Rio Negro, became the opulent heart of the rubber trade. Within a few short years Manaus had Brazil's first telephone system, 16 miles of streetcar tracks, and an electric grid for a city of a million, though it had a population of only 40,000. Vast fortunes were made by individuals, and "flaunting wealth became sport. Rubber barons lit cigars with $100 bank notes and slaked the thirst of their horses with silver buckets of chilled French champagne. Their wives, disdainful of the muddy waters of the Amazon, sent linens to Portugal to be laundered...They ate food imported from Europe...[and] in the wake of opulent dinners, some costing as much as $100,000, men retired to any one of a dozen elegant bordellos." The citizens of Manaus "were the highest per capita consumers of diamonds in the world."

The opulence of the rubber barons could only be exceeded by their brutality. Wild Hevea trees, like all primary rainforest trees are widely dispersed, an adaptation that protects species from the South American leaf blight which easily spreads through and decimates plantations. Thus to make a profit, barons had to acquire control over huge tracts of land. Most did so by by hiring their own private armies to defend their claims, acquire new land, and capture native laborers. Labor was always a problem so barons got creative. One baron created a stud farm, enslaving 600 Indian women whom he bred like cattle. Other barons like Julio Cesar Arana simply used terror to acquire and hold on to Indian slaves. Indians captured usually submitted because resistance only meant more suffering for the families. Young girls were sold as whores, while young men were bound, blindfolded, and had their genitals blasted off. As the Indians died, production soared: in the 12 years that Arana operated on the Putumayo River in Colombia, the native population fell from over 30,000 to less than 8,000 while he exported over 4000 tons of rubber earning over $75 million. The only thing that stopped the holocaust was the downfall of the Brazilian rubber market.

The Brazilian rubber market was crushed by the rapid development of the more efficient rubber plantations of Southeast Asia. However, the prospects of developing plantations did not begin on a high note. Rubber seeds, rich with oil and latex, could not survive the long Atlantic journey from Brazil. Finally, in 1876, an English planter, Henry Wickham, collected 70,000 seeds and shipped them to England. This shipment remains "a source of controversy. Brazilians, conveniently forgetting their entire agricultural economy is based on six imported plants-African oil palm, coffee from Ethiopia, cacao from Colombia and Ecuador, soybeans from China, and sugarcane from Southeast Asia-still speak of the "rubber theft" as a moment of infamy. Wickham himself, in his memoirs, lent a note of mystery to the deed, no doubt intending to elevate his own profile in the eyes of his peers. In fact, all evidence suggests that the exportation was a straight forward affair conducted in the open and actively facilitated by the Brazilian authorities in Belm." In either case, 2800 of the seeds germinated and were sent to Colombo, Ceylon (present day Sri Lanka). After several false starts, including one planter in northern Borneo who felled his plantation after finding no rubber balls hanging from the branches, the prospects were grim. One major obstacle was the success of tea (Ceylon) and coffee (Malaya) gave planters no reason to try an untested crop.

Finally in 1895, Henry Ridley, head of Singapore's botanical garden, persuaded two coffee growers to plant two acres (.8 ha) of Hevea trees. Twelve years later more than 300,000 ha of rubber grew in plantations in Ceylon and Malaya. New innovations increased efficiency and production doubled every two years. Rubber could be produced at only a fraction of the cost of collecting wild rubber in Brazil. By 1910, Brazilian production had fallen to 50%. In 1914, Brazil's market share was down around 30%; 1918 - 20%, and 1940 - 1.3%.

However the second world war threatened to shift the rubber wealth. With Japan occupying prime rubber producing areas in Southeast Asia, the US feared it would run out of the vital material. Every tire, hose, seal, valve, and inch of wiring required rubber. The Rubber Development Corporation, the chief overseer of rubber acquisition, sought out other sources including establishing a rubber program that sent intrepid explorers into the Amazon seeking rubber specimen that would be used to produce high yields, superior product, and possibility of resistance against leaf blight. The ultimate goal of the program was to establish rubber plantations close to home. In addition to searching the Amazon and establishing experimental plantations in Latin America, the program came up with some novel plans to produce rubber including planting Dandelions in 41 states. Extensive work on synthetic rubber yielded a product that, in time, economists predicted would replace natural rubber. By 1964 synthetic rubber made up 75% of the market.

However the situation changed drastically with the OPEC oil embargo of 1973 which doubled the price of synthetic rubber and made oil consumers more conscious of their gas mileage. The concern over gas mileage brought an unexpected threat to the synthetic market: the widespread adoption of the radial tire. The radial tire replaced the simple bias tires (which made up 90% of the market only 5 years earlier) and within a few years virtually all cars were rolling on radials. Synthetic rubber did not have the strength for radials; only natural rubber could provide the required sturdiness. By 1993 natural rubber had recaptured 39% of the domestic market. Today nearly 50% of every auto tire and 100% of all aircraft tires are made of natural rubber. 85% of this rubber is imported from Southeast Asia meaning that the US is highly susceptible to disruptions caused by an embargo or worse, the unintentional or intentional introduction of leaf blight into plantations. None of the trees in plantations across Southeast Asia has resistance to blight so "a single act of biological terrorism, the systematic introduction of fungal spores so small as to be readily concealed in a shoe, could wipe out the plantations, shutting down production of natural rubber for at least a decade. It is difficult to think of any other raw material that is as vital and vulnerable."
"This particular project is very exciting because the Mesoamerican rubber ball game was such a fundamental ritual and political event in these societies, and the ball game could not have developed without inventing the technology to process rubber." Dr. Dorothy Hosler.
Rubber. Our cars would certainly give a worse ride without the stuff. But what is rubber, exactly? And where does it come from?

ANCIENT RUBBER
Until recently modern thinkers believed rubber originated in 19th century Europe. According to a Tech Talk article published by Massachusetts Institute of Technology on Wednesday, July 14, 1999, Professor Dorothy Hosler, Assistant Professor Sandra Burkett and an undergraduate named Michael Tarkanian learned that the Mayan people in ancient Mesoamerica made and used rubber as long ago as 1600 BCE.
The ancient Mayan people used latex to make rubber balls, hollow human figures, and as bindings used to secure axe heads to their handles and other functions. Latex is the sap of various plants, most notably the rubber tree. When it is exposed to the air it hardens into a springy mass. The Mayans learned to mix the rubber sap with the juice from morning glory vines so that it became more durable and elastic, and didn't get quite as brittle. Both the rubber tree and the morning glory were important plants to the Mayan people- the latter being a hallucinogen as well as a healing herb. They two plants tended to grow close together. Combining their juices, a black substance about the texture of a gum-type pencil eraser was formed.
The rubber balls were about the size of a beach ball and weighed over 15 pounds (7 kilograms). These were used in an important ritual game called Tlachtlic. The game was a cross between football and basketball, but had religious significance as recorded in the Popul Vuh, a Mayan religious document. Spanish invaders in the sixteenth century reported that the game also involved gambling for various possessions including land and slaves. It is believed that the game ended in a human sacrifice at least some of the time. Versions of the game were played in the middle American region ranging from southern Arizona to northern South America. Native peoples in the region still make rubber in the same way.

VULCANIZED RUBBER
In 1736 several rolled sheets of rubber were sent to France where it fascinated those who saw it. In 1791, an Englishman named Samuel Peal discovered a means of waterproofing cloth by mixing rubber with turpentine. English inventor and scientist, Joseph Priestly, got his hands on some rubber and realized it could be used to erase pencil marks on sheets of paper.
Charles Goodyear, an American whose name graces the tires under millions of automobiles, is credited with the modern form of rubber. Before 1839, rubber was subject to the conditions of the weather. If the weather was hot and sticky, so was the rubber. In cold weather it became brittle and hard. Goodyear's recipe, a process known as vulcanization, was discovered when a mixture of rubber, lead and sulfur were accidentally dropped onto a hot stove. The result was a substance that wasn't affected by weather, and which would snap back to its original form if stretched. The process was refined and the uses for rubber materials increased as well. This new rubber was resistant to water and chemical interactions and did not conduct electricity, so it was suited for a variety of products. The process of making the rubber product improved as time went by, and now various chemicals are added before the mix is poured into molds, heated and cured under pressure.
An Englishman named Sir Henry Wickham collected about seventy thousand rubber tree seeds in Brazil in 1876 and took them to the East Indies where he started rubber plantations. In 1877 an American named Chapman Mitchell learned to recycle used rubber into new products.

MODERN RUBBER
Today about three quarters of the rubber in production is a synthetic product made from crude oil. World War II cut the United States off from rubber supplies worldwide, and they stepped up production of synthetic rubber for use in the war effort. There are about 20 grades of synthetic rubber and the intended end use determines selection. In general, to make synthetic rubber, byproducts of petroleum refining called butadiene and styrene are combined in a reactor containing soap suds. A milky looking liquid latex results. The latex is coagulated from the liquid and results in rubber "crumbs" that are purchased by manufacturers and melted into numerous products.
There is only one kind of natural rubber. Because the rubber plant only thrives in hot, damp regions near the equator, so 90% of true rubber production today occurs in the Southeast Asian countries of Malaysia and Thailand and in Indonesia. Indonesia's production has dropped in recent years and new plantations were started in Africa to take up the slack.

     Rubber is primarily used in organbuilding for rubber cloth and shock absorption pads.

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