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"An oil on wood"
Oleo sobre tabla 1984. 1,83 x 3,65
LUIS PUNTES
NATURAL RUBBER
According to the renowned historian, Antonio Herrera, Christopher Columbus himself, during his trip to America from 1493 to 1496, would have had knowledge of a game played by the indigenous people of La Española in which they used balls made of an elastic resin. Information has been found that refers to games of this type dating back to the 11th century in the Mayan civilisation.
In 1615, Juan de Torquemada describes in his work, "De la Monarquía Indiana" [The Indian Monarchy], the manufacture of a product called "ulei," prepared by the indigenous people of Mexico using latex from a tree ("ule") in order to waterproof their clothes.
In the 18th century, the Frenchman, La Condamine, during his expedition to South America (1736-1744), observed how some tribes of the Amazons made cuts in the bark of a tree they called "Heve." The liquid obtained had a milky white look, which subsequently darkened and solidified gradually when exposed to the air. The Maina Indians called this material "caucho," formed by connecting the words, caa (wood) and ochu (to cry). The first proposals for using this product likewise appear during this period, which proposals were put forward by the French engineer, Fresneau.
In addition to the trees of the Hevea genus in America, there are various plants throughout the world that are capable of producing similar substances. However, the only one that has been fully implemented for industrial use is Hevea Brasiliensis, which almost all natural rubber on the market comes from.
When a cut is made in the bark of the Hevea, the laticiferous vessels are cut crosswise, thereby causing latex to be secreted, which is a milky white looking liquid that contains about 30% rubber. After a few hours, spontaneous coagulation occurs, and the cut closes. This practice is customarily called "bleeding."
Currently, the useful life of a plantation is approximately 30 years. The main producing countries are located in Southeast Asia (Thailand, Indonesia, Malaysia, Vietnam...) and Equatorial Africa (the Ivory Coast, Nigeria, Cameroon...). For many years, Malaysia was the main manufacturer and exporter and the pioneer in standardising natural rubbers.
The structure and chemical composition of natural rubber is cis 1.4-polyisoprene. Rubber without any additive only has the property of plastic deformation, and it cannot recover, wherefore its initial applications were very limited. In 1839, Charles Goodyear discovered that when sulphur was heated, it caused rubber to harden, and its elastic properties appeared. This is how the first vulcanisation agent appeared (the process of hardening raw rubber is called vulcanisation), and the natural rubber industry was born.
SYNTHETIC RUBBERS
At the end of the 19th century and at the beginning of the 20th century, Great Britain, Germany and the USA attempted to synthesise rubber. However, it wasn't until the First World War that the first large-scale production of synthetic rubber began in Germany using very low quality metallic rubbers.
In the period between wars, during the 30's, the first synthetic rubbers were developed at an industrial level:
- Butadiene S (SBR) and nitrile N (NBR) in Germany between 1935-1937
- Neoprene (CR) in the United States starting 1931.
During the Second World War, in addition to the development of the butadienes in Germany, there was a great push in manufacturing synthetic rubbers in the United States caused by the loss of the supply from Southeast Asia. During this period, GR-S (SBR), GR-I (Butyl) and GR-A (NBR) appear, as well as the first developments in silicone rubbers.
In 1954, natural rubber (cis 1.4-polyisoprene) was synthesised at an industrial scale for the first time in the United States, and subsequently in 1958 the first fluorinated rubbers (Viton) were developed.
In 1961 in Italy, the first EPDM rubbers were produced.
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