Natural rubber is an elastomer An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred when referring to vulcanisates. Each of the monomers (an elastic In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform is removed. The relative amount of deformation is called the strain hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls. Aromatic hydrocarbons , alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons polymer A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties) that was originally derived from latex Latex as found in nature is a milky sap-like fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums that coagulates on exposure to air. It is usually exuded after tissue injury. In most plants, latex is white, but some have yellow, orange, or, a milky colloid A colloidal system consists of two separate phases: a dispersed phase and a continuous phase (or dispersion medium). A colloidal system may be solid, liquid, or gaseous found in the sap of some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the latex sap collected and refined into a usable rubber. The purified form of natural rubber is the chemical polyisoprene, which can also be produced synthetically. Natural rubber is used extensively in many applications and products, as is synthetic rubber.
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Varieties
The commercial source of natural rubber latex is the para rubber tree The Pará rubber tree , often simply called rubber tree, is a tree belonging to the family Euphorbiaceae and the most economically important member of the genus Hevea. It is of major economic importance because its sap-like extract (known as latex) can be collected and is the primary source of natural rubber (Hevea brasiliensis), a member of the spurge family, Euphorbiaceae The family is a large family of flowering plants with 300 genera and around 7,500 species. Most are herbs, but some, especially in the tropics, are also shrubs or trees. Some are succulent and resemble cacti. This is largely because it responds to wounding by producing more latex.
Other plants containing latex include gutta-percha Gutta-percha is a genus of tropical trees native to Southeast Asia and northern Australasia, from Taiwan south to the Malay Peninsula and east to the Solomon Islands. It is also an inelastic natural latex produced from the sap of these trees, particularly from the species Palaquium gutta. Chemically, gutta-percha is a polyterpene, a polymer of (Palaquium gutta),[1] rubber fig (Ficus elastica It is a fat bush in the banyan group of figs, growing to 30–40 metres (rarely up to 60 metres/200 feet) tall, with a stout trunk up to 2 metres (6.6 ft) diameter. The trunk develops aerial and buttressing roots to anchor it in the soil and help support heavy branches. It has broad shiny oval leaves 10–35 centimetres (3.9–14 in) long and 5–1), Panama rubber tree (Castilla elastica Castilla elastica, the Panama Rubber Tree, is a tree native to the tropical areas of Mexico, Central America, and northern South America. It was the principal source of latex among the Mesoamerican peoples in pre-Columbian times. The latex gathered from Castilla elastica was converted into usable rubber by mixing the latex sap with the juice of), spurges (Euphorbia Euphorbia is a genus of plants belonging to the family Euphorbiaceae. Consisting of about 2160 species, Euphorbia is one of the most diverse genera in the plant kingdom, maybe exceeded only by Senecio . Members of the family and genus are sometimes referred to as Spurges. Euphorbia antiquorum and Euphorbia serrata are the type species for the spp.), lettuce Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. In many countries, it is typically eaten cold, raw, in salads, sandwiches, hamburgers, tacos, and in many other dishes. In some places, including China, lettuce is typically eaten cooked and use of the stem is as important as, common dandelion (Taraxacum officinale Taraxacum officinale, commonly called Dandelion, is a herbaceous perennial plant of the family Asteraceae . It can be found growing in temperate regions of the world, in lawns, on roadsides, on disturbed banks and shores of water ways, and other areas with moist soils. T. officinale is considered a weedy species, especially in lawns and along), Russian dandelion (Taraxacum kok-saghyz), Scorzonera It comprises about 100 species, the best-known of which is the edible black salsify . Scorzonera tau-saghyz produces rubber (tau-saghyz), and guayule Parthenium argentatum, commonly known as the Guayule , is a shrub in the family Asteraceae, native to the southwestern United States and northern Mexico, in the US states of New Mexico and Texas; and the Mexican states of Zacatecas, Coahuila, Chihuahua, San Luis Potosí, Nuevo Leon, and Tamaulipas. The plant can be used as an alternate source of (Parthenium argentatum). Although these have not been major sources of rubber, Germany Nazi Germany and the Third Reich are the common English names for Germany under the government of Adolf Hitler and the National Socialist German Worker's Party , from 1933 to 1945. Third Reich (German: Drittes Reich) denotes the Nazi state as the historical successor to the mediæval Holy Roman Empire (962–1806) and to the modern German Empire (1 attempted to use some of these during World War II Albania · Australia · Austria · Azerbaijan · Belarus · Belgium · Brazil · Bulgaria · Burma · Cambodia · Canada · Ceylon (Sri Lanka) · Channel Islands · China · Czechoslovakia · Denmark · Dutch East Indies · Egypt · Estonia · Finland · France · Germany · Gibraltar · Greece · Greenland · Hong Kong · Hungary · Iceland · when it was cut off from rubber supplies[citation needed]. These attempts were later supplanted by the development of synthetic rubbers Synthetic rubber is any type of artificial elastomer, invariably a polymer. An elastomer is a material with the mechanical property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation. Synthetic rubber serves as a substitute for natural rubber in. To distinguish the tree-obtained version of natural rubber from the synthetic version, the term gum rubber is sometimes used.
Discovery of commercial potential
The para rubber tree initially grew in South America. Charles Marie de La Condamine Charles Marie de La Condamine was a French explorer, geographer, and mathematician is credited with introducing samples of rubber to the Académie Royale des Sciences The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at the forefront of scientific developments in Europe in the 17th and 18th centuries. It is one of the earliest academies of sciences of France in 1736.[2] In 1751, he presented a paper by François Fresneau François Fresneau was a French scientist, and is credited for having written the first scientific paper on rubber.He also was known for having the first early idea of water proof material to the Académie (eventually published in 1755) which described many of the properties of rubber. This has been referred to as the first scientific paper on rubber.[2]
When samples of rubber first arrived in England, it was observed by Joseph Priestley Joseph Priestley (13 March 1733 – 6 February 1804) was an 18th-century English theologian, Dissenting clergyman, natural philosopher, educator, and political theorist who published over 150 works. He is usually credited with the discovery of oxygen, having isolated it in its gaseous state, although Carl Wilhelm Scheele and Antoine Lavoisier also, in 1770, that a piece of the material was extremely good for obliterating pencil A pencil is a writing implement or art medium usually constructed of a narrow, solid pigment core inside a protective casing. The case prevents the core from breaking, and also from marking the user’s hand during use marks on paper, hence the name rubber. Later it slowly made its way around England.
South America remained the main source of the limited amounts of latex rubber that were used during much of the 19th century. In 1876, Henry Wickham Sir Henry Alexander Wickham was a British bio-pirate and explorer. He later claimed in self-aggrandising publicity that he was responsible for "stealing" about 70,000 seeds from the rubber-bearing tree, Hevea brasiliensis, in the Santarém area of Brazil in 1876. However there was, in fact, no law at the time forbidding their export and gathered thousands of para rubber tree seeds from Brazil Brazil (pronounced /brəˈzɪl/ ; Portuguese: Brasil, IPA: [bɾaˈziw]), officially the Federative Republic of Brazil (Portuguese: República Federativa do Brasil, listen (help·info)), is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population. It is the only Portuguese-speaking, and these were germinated in Kew Gardens The Royal Botanic Gardens, Kew, usually referred to simply as Kew Gardens, are 121 hectares of gardens and botanical glasshouses between Richmond and Kew in southwest London, England. The director is Professor Stephen D. Hopper, who succeeded Professor Sir Peter Crane. The Royal Botanic Gardens, Kew is also the name of the organisation that runs, England. The seedlings were then sent to Ceylon As a result of its location in the path of major sea routes, Sri Lanka is a strategic naval link between West Asia and South East Asia.[citation needed] It has also been a center of the Buddhist religion and culture from ancient times and is one of the few remaining abodes of Buddhism in South Asia, including Ladakh, Bhutan and the Chittagong Hill (Sri Lanka As a result of its location in the path of major sea routes, Sri Lanka is a strategic naval link between West Asia and South East Asia.[citation needed] It has also been a center of the Buddhist religion and culture from ancient times and is one of the few remaining abodes of Buddhism in South Asia, including Ladakh, Bhutan and the Chittagong Hill), Indonesia Indonesia , officially the Republic of Indonesia (Indonesian: Republik Indonesia), is a country in Southeast Asia and Oceania. Indonesia comprises 17,508 islands. With a population of around 230 million people, it is the world's fourth most populous country, and has the world's largest population of Muslims. Indonesia is a republic, with an, Singapore Singapore, officially the Republic of Singapore, is an island country off the southern tip of the Malay Peninsula, 137 kilometres north of the equator, in the Southeast Asian region of the Asian continent. It is separated from Malaysia by the Straits of Johor to its north, and from Indonesia's Riau Islands by the Singapore Strait to its south. A and British Malaya British Malaya loosely described a set of states on the Malay Peninsula that were colonized by the British from the 18th and the 19th until the 20th century. Before the formation of Malayan Union in 1946, the colonies were not placed under a single unified administration. Instead, British Malaya comprised the Straits Settlements, the Federated. Malaya (now Malaysia ^ b. The current terminology as per government policy is Bahasa Malaysia but legislation continues to refer to the official language as Bahasa Melayu (literally Malay language). English may continue to be used for some official purposes under the National Language Act 1967) was later to become the biggest producer of rubber. About 100 years ago, the Congo Free State The Congo Free State was a government privately controlled by Leopold II, King of the Belgians through a dummy non-governmental organization, the Association internationale africaine. Leopold was the sole shareholder and chairman, who increasingly used it for rubber, copper and other minerals in the upper Lualaba River basin . The state included in Africa was also a significant source of natural rubber latex, mostly gathered by forced labour Unfree labour is a generic or collective term for those work relations, especially in modern or early modern history, in which people are employed against their will by the threat of destitution, detention, violence (including death), or other extreme hardship to themselves, or to members of their families. Many of these forms of work may be. Liberia Liberia /laɪˈbɪəriə/ , officially the Republic of Liberia, is a country on the west coast of Africa, bordered by Sierra Leone, Guinea, Côte d'Ivoire, and the Atlantic Ocean. As of the 2008 Census, the nation is home to 3,476,608 people and covers 111,369 square kilometres (43,000 sq mi) and Nigeria Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising thirty-six states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in the north. Its coast in the south lies on also started production of rubber.
In India, commercial cultivation of natural rubber was introduced by the British planters, although the experimental efforts to grow rubber on a commercial scale in India were initiated as early as 1873 at the Botanical Gardens, Calcutta Kolkata , is the capital of the Indian state of West Bengal. Kolkata is the cultural capital of India and the commercial capital of Eastern India. It is located in eastern India on the east bank of the Hooghly River. The Kolkata metropolitan area including suburbs has a population exceeding 15 million, making it the third most populous. The first commercial Hevea plantations in India were established at Thattekadu in Kerala Kerala (Malayalam: കേരളം, pronounced [Kēraḷam]) is a state in South West India. It was created on 1 November 1956, with the passing of the States Reorganisation Act bringing together the areas where Malayalam was the dominant language in 1902. In the 19th and early 20th century, it was often called "India rubber." Some rubber plantations were also started by the British in Pakistan Pakistan (Urdu pronunciation: [paːkɪsˈtaːn] ( listen)), officially the Islamic Republic of Pakistan (Urdu: اسلامی جمہوریہ پاکِستان) (also the Federation of Pakistan), is a country in South Asia. It has a 1,046-kilometre (650 mi) coastline along the Arabian Sea and Gulf of Oman in the south, is bordered by Afghanistan and. Today (as of 2010), India's natural rubber consumption stands at 0.978 million tons per year, with production at 0.893 million tons. The rest is imported with an import duty of 20%.
Properties
Rubber latexRubber exhibits unique physical and chemical properties. Rubber's stress-strain behavior exhibits the Mullins effect The Mullins effect is the stress-strain response in filled rubbers which typically depends on the maximum loading previously encountered. The phenomenon, named for British rubber scientist Leonard Mullins, working at MBL Group in Leyland, can be idealized for many purposes as an instantaneous and irreversible softening of the stress-strain curve, the Payne effect The Payne effect is a particular feature of the stress-strain behaviour of rubber, especially rubber compounds containing fillers such as carbon black. It is named after the British rubber scientist A. R. Payne, who made extensive studies of the effect . The effect is sometimes also known as the Fletcher-Gent effect, after the authors of the first, and is often modeled as hyperelastic A hyperelastic or Green elastic material is an ideally elastic material for which the stress-strain relationship derives from a strain energy density function. The hyperelastic material is a special case of a Cauchy elastic material. Rubber strain crystallizes Strain crystallization is a phenomenon in which an initially amorphous solid material undergoes a phase transformation due to the application of strain. Strain crystallization occurs in natural rubber, and some other elastomers. The phenomenon has important effects on strength and fatigue properties.
Owing to the presence of a double bond A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, and other covalent bonds. In short, the attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding in each repeat unit An essential concept which defines polymer structure, the repeat unit is the simplest structural entity of a polymer chain. So a polymer consists of several repeat units linked together successively along the chain, like the beads of a necklace. A repeat unit is sometimes called a mer or mer unit. "Mer" originates from the Greek word &, natural rubber is sensitive to ozone cracking Cracks can be formed in many different elastomers by ozone attack, and the characteristic form of attack of vulnerable rubbers is known as ozone cracking. The problem was formerly very common, especially in tires, but is now rarely seen in those products owing to preventative measures.
Solvents
There are two main solvents A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature. Common uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene), as a paint thinner (e.g. toluene, turpentine), as nail polish removers and for rubber: turpentine Turpentine is a fluid obtained by the distillation of resin obtained from trees, mainly pine trees. It is composed of terpenes, mainly the monoterpenes alpha-pinene and beta-pinene. It is sometimes known colloquially as turps, but this more often refers to turpentine substitute (or mineral turpentine) and naphtha Naphtha normally refers to a number of different flammable liquid mixtures of hydrocarbons, i.e. a distillation product from petroleum or coal tar boiling in a certain range and containing certain hydrocarbons. It is a broad term covering the lightest and most volatile fraction of the liquid hydrocarbons in petroleum (petroleum). The former has been in use since 1764 when François Fresnau made the discovery. Giovanni Fabronni is credited with the discovery of naphtha as a rubber solvent in 1779. Because rubber does not dissolve easily, the material is finely divided by shredding prior to its immersion.
An ammonia solution can be used to prevent the coagulation of raw latex while it is being transported from its collection site.
Chemical makeup
Latex is a natural polymer of isoprene (most often cis-1,4-polyisoprene) – with a molecular weight of 100,000 to 1,000,000. Typically, a small percentage (up to 5% of dry mass) of other materials, such as proteins, fatty acids, resins and inorganic materials (salts) are found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber".
Some natural rubber sources called gutta-percha are composed of trans-1,4-polyisoprene, a structural isomer which has similar, but not identical, properties.
Natural rubber is an elastomer and a thermoplastic. However, it should be noted that once 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.
Elasticity
In most elastic materials, such as metals used in springs, the elastic behavior is caused by bond distortions. When force is applied, bond lengths deviate from the (minimum energy) equilibrium and strain energy is stored electrostatically. Rubber is often assumed to behave in the same way, but it turns out this is a poor description. Rubber is a curious material because, unlike metals, strain energy is stored thermally. Also, natural rubber is so elastic that when force is applied, on natural rubber when it is on a surface similar to carpet, it may be difficult to 'pull' across the surface. It will stick.
In its relaxed state, rubber consists of long, coiled-up polymer chains that are interlinked at a few points. Between a pair of links, each monomer can rotate freely about its neighbour, thus giving each section of chain leeway to assume a large number of geometries, like a very loose rope attached to a pair of fixed points. At room temperature, rubber stores enough kinetic energy so that each section of chain oscillates chaotically, like the above piece of rope being shaken violently. The entropy model of rubber was developed in 1934 by Werner Kuhn.
When rubber is stretched, the "loose pieces of rope" are taut and thus no longer able to oscillate. Their kinetic energy is given off as excess heat. Therefore, the entropy decreases when going from the relaxed to the stretched state, and it increases during relaxation. This change in entropy can also be explained by the fact that a tight section of chain can fold in fewer ways (W) than a loose section of chain, at a given temperature (nb. entropy is defined as S=k*ln(W)). Relaxation of a stretched rubber band is thus driven by an increase in entropy, and the force experienced is not electrostatic, rather it is a result of the thermal energy of the material being converted to kinetic energy. Rubber relaxation is endothermic, and for this reason the force exerted by a stretched piece of rubber increases with temperature. (Metals, for example, become softer as temperature increases). The material undergoes adiabatic cooling during contraction. This property of rubber can easily be verified by holding a stretched rubber band to your lips and relaxing it. Stretching of a rubber band is in some ways equivalent to the compression of an ideal gas, and relaxation is equivalent to its expansion. Note that a compressed gas also exhibits "elastic" properties, for instance inside an inflated car tire. The fact that stretching is equivalent to compression may seem somewhat counterintuitive, but it makes sense if rubber is viewed as a one-dimensional gas. Stretching reduces the "space" available to each section of chain.
Vulcanization of rubber creates more disulfide bonds between chains, so it shortens each free section of chain. The result is that the chains tighten more quickly for a given length of strain, thereby increasing the elastic force constant and making rubber harder and less extensible.
When cooled below the glass transition temperature, the quasi-fluid chain segments "freeze" into fixed geometries and the rubber abruptly loses its elastic properties, although the process is reversible. This is a property it shares with most elastomers. At very low temperatures, rubber is rather brittle; it will break into shards when struck or stretched. This critical temperature is the reason winter tires use a softer version of rubber than normal tires. The failing rubber o-ring seals that contributed to the cause of the Challenger disaster were thought to have cooled below their critical temperature. The disaster happened on an unusually cold day.
Current sources
Close to 21 million tons of rubber were produced in 2005 of which around 42% was natural. Since the bulk of the rubber produced is the synthetic variety which is derived from petroleum, the price of even natural rubber is determined to a very large extent by the prevailing global price of crude oil.[3][4] Today Asia is the main source of natural rubber, accounting for around 94% of output in 2005. The three largest producing countries (Indonesia, Malaysia and Thailand) together account for around 72% of all natural rubber production.
Cultivation
Rubber is generally cultivated in large plantations. See the coconut shell used in collecting latex, in plantations in Kerala, IndiaRubber latex is extracted from rubber trees. The economic life period of rubber trees in plantations is around 32 years – up to 7 years of immature phase and about 25 years of productive phase.
The soil requirement of the plant is generally well-drained weathered soil consisting of laterite, lateritic types, sedimentary types, nonlateritic red or alluvial soils.
The climatic conditions for optimum growth of rubber trees consist of (a) rainfall of around 250 cm evenly distributed without any marked dry season and with at least 100 rainy days per year (b) temperature range of about 20°C to 34°C with a monthly mean of 25°C to 28°C (c) high atmospheric humidity of around 80% (d) bright sunshine amounting to about 2000 hours per year at the rate of 6 hours per day throughout the year and (e) absence of strong winds.
Many high-yielding clones have been developed for commercial planting. These clones yield more than 2,000 kilograms of dry rubber per hectare per year, when grown under ideal conditions.
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The left passenger peg . rubber. cover is now loose on my Wee. My wife stands on it when climbing aboard - I guess that action must cause it to want to.
