Rubber

Rubber

Overview
Natural rubber, also called India rubber or caoutchouc, is an elastomer
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...

 (an elastic
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....

 hydrocarbon
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....

 polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

) that was originally derived from latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...

, a milky colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...

 produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined into a usable rubber. The purified form of natural rubber is the chemical polyisoprene
Isoprene
Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...

, which can also be produced synthetically.
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Encyclopedia
Natural rubber, also called India rubber or caoutchouc, is an elastomer
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...

 (an elastic
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....

 hydrocarbon
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....

 polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

) that was originally derived from latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...

, a milky colloid
Colloid
A colloid is a substance microscopically dispersed evenly throughout another substance.A colloidal system consists of two separate phases: a dispersed phase and a continuous phase . A colloidal system may be solid, liquid, or gaseous.Many familiar substances are colloids, as shown in the chart below...

 produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined into a usable rubber. The purified form of natural rubber is the chemical polyisoprene
Isoprene
Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...

, which can also be produced synthetically. Natural rubber is used extensively in many applications and products, as is synthetic rubber. It is normally very stretchy and flexible and extremely waterproof.

Varieties


The commercial source of natural rubber latex is the para rubber tree
Para rubber tree
Hevea brasiliensis, 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...

 (Hevea brasiliensis), a member of the spurge family, Euphorbiaceae
Euphorbiaceae
Euphorbiaceae, the Spurge family are 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, also this means that the tree is able to photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

e more.

Other plants containing latex include gutta-percha
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. The same term is used to refer to an inelastic natural latex produced from the sap of these trees, particularly from the species...

 (Palaquium gutta), rubber fig (Ficus elastica
Ficus elastica
Ficus elastica, also called the rubber fig, rubber bush, rubber tree, rubber plant, or Indian rubber bush is a species of plant in the fig genus, native to northeast India and southern Indonesia....

), Panama rubber tree (Castilla elastica
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...

), spurges (Euphorbia spp.), lettuce
Lettuce
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...

, common dandelion (Taraxacum officinale
Taraxacum officinale
Taraxacum officinale, the common 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...

), Russian dandelion (Taraxacum kok-saghyz
Taraxacum kok-saghyz
Taraxacum kok-saghyz, often abbreviated as TKS and commonly referred to as the Russian Dandelion or Rubber Root, is a species of dandelion native to Uzbekistan and Kazakhstan that is notable for its production of high quality rubber. T...

), Scorzonera
Scorzonera
Scorzonera is a genus of the sunflower family , subfamily Lactucoideae, tribe Lactuceae, subtribe Scorzonerinae.It comprises about 100 species, the best-known of which is the edible black salsify...

 (tau-saghyz)
, and guayule
Guayule
Parthenium argentatum, commonly known as the Guayule , is a flowering shrub in the aster family, Asteraceae, that is native to the southwestern United States and northern Mexico. It can be found in the US states of New Mexico and Texas and the Mexican states of Zacatecas, Coahuila, Chihuahua, San...

 (Parthenium argentatum). Although these have not been major sources of rubber, Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 attempted to use some of these during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 when it was cut off from rubber supplies. These attempts were later supplanted by the development of synthetic rubber
Synthetic rubber
Synthetic rubber is 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...

s. 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
Charles Marie de La Condamine was a French explorer, geographer, and mathematician. He spent ten years in present-day Ecuador measuring the length of a degree latitude at the equator and preparing the first map of the Amazon region based on astronomical observations.-Biography:Charles Marie de La...

 is credited with introducing samples of rubber to the Académie Royale des Sciences of France in 1736. In 1751, he presented a paper by François Fresneau
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.-References:...

 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.

When samples of rubber first arrived in England, it was observed by Joseph Priestley
Joseph Priestley
Joseph Priestley, FRS was an 18th-century English theologian, Dissenting clergyman, natural philosopher, chemist, educator, and political theorist who published over 150 works...

, in 1770, that a piece of the material was extremely good for rubbing off pencil
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
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...

 gathered thousands of para rubber tree seeds from Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, and these were germinated in Kew Gardens, England. The seedlings were then sent to Ceylon (Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

), Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

, Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

 and British Malaya
British Malaya
British Malaya loosely described a set of states on the Malay Peninsula and the Island of Singapore that were brought under British control between the 18th and the 20th centuries...

. Malaya (now Malaysia) was later to become the biggest producer of rubber. About 100 years ago, the Congo Free State
Congo Free State
The Congo Free State was a large area in Central Africa which was privately controlled by Leopold II, King of the Belgians. Its origins lay in Leopold's attracting scientific, and humanitarian backing for a non-governmental organization, the Association internationale africaine...

 in Africa was also a significant source of natural rubber latex, mostly gathered by forced labour. Liberia
Liberia
Liberia , officially the Republic of Liberia, is a country in West Africa. It is bordered by Sierra Leone on the west, Guinea on the north and Côte d'Ivoire on the east. Liberia's coastline is composed of mostly mangrove forests while the more sparsely populated inland consists of forests that open...

 and Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 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...

 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. The first commercial Hevea plantations in India were established at Thattekadu in Kerala
Kerala
or Keralam is an Indian state located on the Malabar coast of south-west India. It was created on 1 November 1956 by the States Reorganisation Act by combining various Malayalam speaking regions....

 in 1902. In the 19th and early 20th century, it was often called "India rubber." In 2010, India's natural rubber consumption stood at 0.978 million tons per year, with production at 0.893 million tons; the rest was imported with an import duty of 20%.

Properties



Rubber exhibits unique physical and chemical properties. Rubber's stress-strain behavior exhibits the Mullins effect
Mullins effect
The Mullins effect is a particular aspect of the mechanical response in filled rubbers in which the stress-strain curve depends on the maximum loading previously encountered...

, the Payne effect
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...

, and is often modeled as hyperelastic
Hyperelastic material
A hyperelastic or Green elastic material is a type of constitutive model for 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.For many materials, linear elastic...

. Rubber strain crystallizes
Strain crystallization
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...

.

Owing to the presence of a double bond
Double bond
A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...

 in each repeat unit
Repeat unit
An essential concept which defines polymer structure, the repeat unit or repeating unit is a part of a polymer chain whose repetition would produce the complete polymer by linking the repeat units together successively along the chain, like the beads of a necklace.A repeat unit is sometimes called...

, natural rubber is sensitive to ozone cracking
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...

.

Solvents


There are two main solvents for rubber: turpentine
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...

 and naphtha
Naphtha
Naphtha normally refers to a number of different flammable liquid mixtures of hydrocarbons, i.e., a component of natural gas condensate or a distillation product from petroleum, coal tar or peat boiling in a certain range and containing certain hydrocarbons. It is a broad term covering among the...

 (petroleum). The former has been in use since 1764 when François Fresnau made the discovery. Giovanni Fabbroni
Giovanni Fabbroni
Giovanni Valentino Mattia Fabbroni was an Italian naturalist, economist, agronomist and chemist....

 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
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 solution can be used to prevent the coagulation
Flocculation
Flocculation, in the field of chemistry, is a process wherein colloids come out of suspension in the form of floc or flakes by the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually...

 of raw latex while it is being transported from its collection site.

Chemical makeup


Latex is a natural polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 of isoprene
Isoprene
Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...

 (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
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. The same term is used to refer to an inelastic natural latex produced from the sap of these trees, particularly from the species...

 are composed of trans-1,4-polyisoprene, a structural isomer which has similar, but not identical, properties.

Natural rubber is an elastomer
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...

 and a thermoplastic
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...

. 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
Coil spring
A Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces...

, the elastic behavior is caused by bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...

 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
Thermal energy
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system's temperature....

.

In its relaxed state, rubber consists of long, coiled-up polymer chains that are interlinked
Disulfide bond
In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...

 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
Room temperature
-Comfort levels:The American Society of Heating, Refrigerating and Air-Conditioning Engineers has listings for suggested temperatures and air flow rates in different types of buildings and different environmental circumstances. For example, a single office in a building has an occupancy ratio per...

, rubber stores enough kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...

 so that each section of chain oscillates chaotically, like the above piece of rope being shaken violently. The entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

 model of rubber was developed in 1934 by Werner Kuhn
Werner Kuhn
Werner Kuhn is a Swiss physical chemist who developed the first model of the viscosity of polymer solutions using statistical mechanics. He is known for being the first to apply Boltzmann's entropy formula:S = k \log W \!...

.

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
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

 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
Rubber band
A rubber band is a short length of rubber and latex formed in the shape of a loop and is commonly used to hold multiple objects together...

 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
Endothermic
In thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...

, 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
Adiabatic process
In thermodynamics, an adiabatic process or an isocaloric process is a thermodynamic process in which the net heat transfer to or from the working fluid is zero. Such a process can occur if the container of the system has thermally-insulated walls or the process happens in an extremely short time,...

 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
Ideal gas
An ideal gas is a theoretical gas composed of a set of randomly-moving, non-interacting point particles. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.At normal conditions such as...

, and relaxation is equivalent to its expansion. Note that a compressed gas also exhibits "elastic" properties, for instance inside an inflated car tire
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...

. 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
Vulcanization
Vulcanization or vulcanisation is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent "curatives." These additives modify the polymer by forming crosslinks between individual polymer chains. Vulcanized material is...

 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
Strain (materials science)
In continuum mechanics, the infinitesimal strain theory, sometimes called small deformation theory, small displacement theory, or small displacement-gradient theory, deals with infinitesimal deformations of a continuum body...

, 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
O-ring
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The 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. Today Asia is the main source of natural rubber, accounting for around 94% of output in 2005. The three largest producing countries, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

, Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

 (2.4m tons) and Malaysia, together account for around 72% of all natural rubber production. Natural rubber is not cultivated widely in its native continent of South America due to the existence of South American leaf blight, and other natural predators of the rubber tree.

Cultivation



Rubber 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. (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 and ideal field.

Collection


In places like Kerala
Kerala
or Keralam is an Indian state located on the Malabar coast of south-west India. It was created on 1 November 1956 by the States Reorganisation Act by combining various Malayalam speaking regions....

, where coconuts are in abundance, the half shell of coconut is used as the collection container for the latex but glazed pottery or aluminium or plastic cups are more common elsewhere. The cups are supported by a wire that encircles the tree. This wire incorporates a spring so it can stretch as the tree grows. The latex is led into the cup by a galvanised "spout" knocked into the bark. Tapping normally takes place early in the morning, when the internal pressure of the tree is highest. A good tapper can tap a tree every 20 seconds on a standard half-spiral system, and a common daily "task" size is between 450 and 650 trees. Trees are usually tapped alternate or third daily, although there are many variations in timing, length and number of cuts. The latex, which contains 25–40% dry rubber, is in the bark, so the tapper must avoid cutting right through to the wood or the growing cambial layer will be damaged and the renewing bark will be badly deformed, making later tapping difficult. It is usual to tap a pannel at least twice, sometimes three times, during the trees' life. The economic life of the tree depends on how well the tapping is carried out, as the critical factor is bark consumption. A standard in Malaysia for alternate daily tapping is 25 cm (vertical) bark consumption per year. The latex tubes in the bark ascend in a spiral to the right. For this reason, tapping cuts usually ascend to the left to cut more tubes.

The trees will drip latex for about four hours, stopping as latex coagulates naturally on the tapping cut, thus blocking the latex tubes in the bark. Tappers usually rest and have a meal after finishing their tapping work, then start collecting the latex at about midday. Some trees will continue to drip after the collection and this leads to a small amount of cup lump which is collected at the next tapping. The latex that coagulates on the cut is also collected as tree lace. Tree lace and cup lump together account for 10–20% of the dry rubber produced.

The latex will coagulate in cup if kept for long. The latex has to be collected before coagulation. The collected latex is transferred in to coagulation tanks for the preparation of dry rubber or transferred into air-tight containers with sieving for ammoniation. Ammoniation is necessary to preserve the latex in colloidal state for long.

Latex is generally processed into either latex concentrate for manufacture of dipped goods or it can be coagulated under controlled, clean conditions using formic acid. The coagulated latex can then be processed into the higher grade technically specified block rubbers such as SVR 3L or SVR CV or used to produce Ribbed Smoke Sheet grades.

Naturally coagulated rubber (cup lump) is used in the manufacture of TSR10 and TSR20 grade rubbers. The processing of the rubber for these grades is basically a size reduction and cleaning process to remove contamination and prepare the material for the final stage of drying.

The dried material is then baled and palletized for storage and shipment in various methods of transportation.

Transportation


Natural Rubber Latex is shipped from their factories in Asia, South America and North Africa to destinations around the world. As cost of natural rubber has risen significantly, the shipping methods which offer the lowest cost per unit (kg, tonne or pound) are preferred. Depending on the destination, warehouse availability, transportation conditions, some methods are more suitable to certain buyers than others. In international trade, latex rubber is mostly shipped in 20 foot ocean containers. Inside the ocean container, various types of smaller containers are used by factories to store latex rubber.

1. Steel Drums:

55 gallon steel drum205 kilogram or 55 gallon drum steel drums are the traditional method of packaging of natural latex. The drum is typically made of steel with a rubbed outer to improve rigidity and durability. A 20 foot container can store 80 of such 55 gallon drums for a net weight of 16.40 metric ton (16,400 kilogram or 36,080 "wet" pound) of latex. The use of drums allows bulk transportation to save cost yet permits flexibility in retail distribution. A broker can sell in small quantity such as 1 or 2 drums.

2. ISO Tanks:

These tanks are in fact the ocean container itself. They all have standard size of 20 foot x 8 foot x 8’6 foot. Their capacity is between 17,500 to 25,000 liters depending on the cylinder size and shape. These ISO tanks can also be used for transportation of liquid chemicals and food stuffs. This is the costliest shipping method, but also provides most convenient handling in some countries. Usually the buyer has to buy the entire tank to enjoy the benefit of bulk saving.

3. Flexitank or Flexibag inside 20 foot container:

Flexitanks offer a much cheaper method of shipping than ISO tank, and they are widely used nowadays. The flexitank itself is a big PE bag with a valve to for loading and later, unloading of the liquid content. The PE bag is placed inside a 20 foot container with proper reinforcement near the container doors. The latex is then pumped into the PE bag (picture 3), which is "blown up" as the amount of liquid increases. Maximum of 21 tons of liquid latex can be stored inside a flexitank as this is a limit weight allowable on public streets and highways in many countries. The container doors are closed, sealed, and are ready for load onto sailing ship. At destination, the rubber latex is pumped out using hydrolic pumps. The flexitank is discarded after use.
4. Other Methods:

Totes made of PE or corrugated paper of different sizes are sometimes used to transport latex rubber. Their footprints (bases) are often similar to the size of a standard pallet (40 in x 48 in). However, these totes are less common as the other methods make the majority of shipment volume in international trades.

Uses


The use of rubber is widespread, ranging from household to industrial products, entering the production stream at the intermediate stage or as final products. Tires and tubes are the largest consumers of rubber. The remaining 44% are taken up by the general rubber goods (GRG) sector, which includes all products except tires and tubes.

Prehistoric uses


The first use of rubber was by the Olmec
Olmec
The Olmec were the first major Pre-Columbian civilization in Mexico. They lived in the tropical lowlands of south-central Mexico, in the modern-day states of Veracruz and Tabasco....

s, who centuries later passed on the knowledge of natural latex from the Hevea tree in 1600 BC to the ancient Mayans
Maya civilization
The Maya is a Mesoamerican civilization, noted for the only known fully developed written language of the pre-Columbian Americas, as well as for its art, architecture, and mathematical and astronomical systems. Initially established during the Pre-Classic period The Maya is a Mesoamerican...

. They boiled the harvested latex to make a ball for a sport.

Manufacturing


Other significant uses of rubber are door and window profiles, hoses, belts, matting, flooring and dampeners (antivibration mounts) for the automotive industry in what is known as the "under the bonnet" products. Gloves (medical, household and industrial) and toy
Toy
A toy is any object that can be used for play. Toys are associated commonly with children and pets. Playing with toys is often thought to be an enjoyable means of training the young for life in human society. Different materials are used to make toys enjoyable and cuddly to both young and old...

 balloon
Balloon
A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...

s are also large consumers of rubber, although the type of rubber used is that of the concentrated latex. Significant tonnage of rubber is used as adhesive
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...

s in many manufacturing
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...

 industries and products, although the two most noticeable are the paper
Paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

 and the carpet
Carpet
A carpet is a textile floor covering consisting of an upper layer of "pile" attached to a backing. The pile is generally either made from wool or a manmade fibre such as polypropylene,nylon or polyester and usually consists of twisted tufts which are often heat-treated to maintain their...

 industries. Rubber is also commonly used to make rubber band
Rubber band
A rubber band is a short length of rubber and latex formed in the shape of a loop and is commonly used to hold multiple objects together...

s and pencil eraser
Eraser
An eraser or rubber is an article of stationery that is used for rubbing out pencil markings. Erasers have a rubbery consistency and are often white or pink, although modern materials allow them to be made in any color. Many pencils are equipped with an eraser on one end...

s. Many aircraft tires and inner tubes are still made of natural rubber due to the high cost of certification for aircraft use of synthetic replacements.

Textile applications


Additionally, rubber produced as a fiber sometimes called elastic, has significant value for use in the textile industry because of its excellent elongation and recovery properties. For these purposes, manufactured rubber fiber is made as either an extruded round fiber or rectangular fibers that are cut into strips from extruded film. Because of its low dye acceptance, feel and appearance, the rubber fiber is either covered by yarn of another fiber or directly woven with other yarns into the fabric. In the early 1900s, for example, rubber yarns were used in foundation garments. While rubber is still used in textile manufacturing, its low tenacity limits its use in lightweight garments because latex lacks resistance to oxidizing agents and is damaged by aging, sunlight, oil, and perspiration. Seeking a way to address these shortcomings, the textile industry has turned to Neoprene
Neoprene
Neoprene or polychloroprene is a family of synthetic rubbers that are produced by polymerization of chloroprene. Neoprene in general has good chemical stability, and maintains flexibility over a wide temperature range...

 (polymer form of Chloroprene
Chloroprene
Chloroprene is the common name for the organic compound 2-chlorobuta-1,3-diene, which has the formula CH2=CCl-CH=CH2. This colorless liquid is the monomer for the production of the polymer polychloroprene, a type of synthetic rubber...

), a type of synthetic rubber as well as another more commonly used elastomer fiber, spandex
Spandex
Spandex or elastane is a synthetic fibre known for its exceptional elasticity. It is strong, but less durable than natural Latex, its major non-synthetic competitor. It is a polyurethane-polyurea copolymer that was co-invented in 1959 by chemists C. L. Sandquist and Joseph Shivers at DuPont's...

 (also known as elastane), because of their superiority to rubber in both strength and durability.

Vulcanization



Natural rubber is often vulcanized
Vulcanization
Vulcanization or vulcanisation is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent "curatives." These additives modify the polymer by forming crosslinks between individual polymer chains. Vulcanized material is...

, a process by which the rubber is heated and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

, peroxide
Peroxide
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...

 or bisphenol
Bisphenol
The bisphenols are a group of chemical compounds with two hydroxyphenyl functionalities. Most of them based on diphenylmethane. The exceptions are Bisphenol S, P, and M ....

 are added to improve resistance and elasticity
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....

, and to prevent it from perishing. The development of vulcanization is most closely associated with Charles Goodyear
Charles Goodyear
Charles Goodyear was an American inventor who developed a process to vulcanize rubber in 1839 -- a method that he perfected while living and working in Springfield, Massachusetts in 1844, and for which he received patent number 3633 from the United States Patent Office on June 15, 1844Although...

 in 1839. Carbon black
Carbon black
Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio, although its...

 is often used as an additive to rubber to improve its strength, especially in vehicle tires.

Allergic reactions


Some people have a serious latex allergy
Latex allergy
Latex allergy is a medical term encompassing a range of allergic reactions to natural rubber latex.-Type I:The most serious and rare form, type I is an immediate and potentially life-threatening reaction, not unlike the severe reaction some people have to bee stings...

, and exposure to certain natural rubber latex products such as latex gloves can cause anaphylactic shock. Guayule
Guayule
Parthenium argentatum, commonly known as the Guayule , is a flowering shrub in the aster family, Asteraceae, that is native to the southwestern United States and northern Mexico. It can be found in the US states of New Mexico and Texas and the Mexican states of Zacatecas, Coahuila, Chihuahua, San...

 latex is hypoallergenic
Hypoallergenic
Hypoallergenic, meaning "below normal" or "slightly" allergenic, was a term first used in a cosmetics campaign in 1953. It is used to describe items that cause or are claimed to cause fewer allergic reactions...

 and is being researched as a substitute to the allergy-inducing Hevea
Hevea
Hevea is a genus of flowering plants in the spurge family, Euphorbiaceae. It is also one of many names used commercially for the wood of the most economically important species H. brasiliensis.-Selected species:* Hevea benthamiana Müll.Arg....

latexes. Unlike the sappable Hevea tree, these relatively small shrubs must be harvested whole and latex extracted from each cell. Chemical processes may also be employed to reduce the amount of antigenic protein in Hevea latex, resulting in alternative Hevea-based materials such Vytex Natural Rubber Latex
Vytex Natural Rubber Latex
Vytex Natural Rubber Latex is a brand of natural rubber latex produced and marketed by Vystar Corporation. Vytex NRL is an alternative material to petroleum-based synthetics and traditional, or Hevea, natural rubber latex...

 that, while not completely hypoallergenic, do provide lessened exposure to latex allergens.

Some allergic reactions are not from the latex but from residues of other ingredients used to process the latex into clothing, gloves, foam, etc. These allergies are usually referred to as multiple chemical sensitivity
Multiple chemical sensitivity
Multiple chemical sensitivity is a chronic medical condition characterized by symptoms the affected person attributes to exposure to low levels of chemicals. Commonly suspected substances include smoke, pesticides, plastics, synthetic fabrics, scented products, petroleum products and paints...

(MCS).

See also

  • Akron, Ohio
    Akron, Ohio
    Akron , is the fifth largest city in the U.S. state of Ohio and the county seat of Summit County. It is located in the Great Lakes region approximately south of Lake Erie along the Little Cuyahoga River. As of the 2010 census, the city had a population of 199,110. The Akron Metropolitan...

    , center of the rubber industry in the USA
  • Condom
    Condom
    A condom is a barrier device most commonly used during sexual intercourse to reduce the probability of pregnancy and spreading sexually transmitted diseases . It is put on a man's erect penis and physically blocks ejaculated semen from entering the body of a sexual partner...

    s, also called "rubbers"
  • Emulsion dispersion
    Emulsion dispersion
    An emulsion dispersion is thermoplastics or elastomers suspended in a waterphase with help of emulsifiers.-Preparation:Emulsions are thermodynamically unstable liquid/liquid dispersions that are stabilized, in general, by surfactants...

  • Fordlândia
    Fordlândia
    Fordlândia is a now-abandoned, prefabricated industrial town established in the Amazon Rainforest in 1928 by American industrialist Henry Ford to secure a source of cultivated rubber for the automobile manufacturing operations of the Ford Motor Company in the United States...

    , failed attempt to establish a rubber plantation in Brazil
  • Reinforced rubber
    Reinforced rubber
    Although seldom shared under this name, one of the largest groups of composite materials worldwide is that of the reinforced rubber products. Familiar examples are automobile tyres, hoses and conveyor belts.-Composite reinforced structure:...

  • Resilin
    Resilin
    Resilin is an elastomeric protein found in many insects. The protein was first discovered by Torkel Weis-Fogh in the locust wing-hinge. As of 2005 it is the most efficient elastic protein known . The elastic efficiency of the resilin isolated from locust tendon has been reported to be 97 %...

    , a rubber substitute
  • Rubber seed oil
    Rubber seed oil
    Rubber seed oil is oil extracted from the seeds of rubber trees. In the latex manufacturing process, rubber seeds are not historically collected and commercialized. Recent analysis shows that rubber seed oil contained the following fatty acids:...

  • Rubber technology
    Rubber technology
    Rubber technology is the subject dealing with the transformation of rubbers or elastomers into useful products, such as automobile tires.The materials includes latex, natural rubber, synthetic rubber and other polymeric materials, such as thermoplastic elastomers.-Vulcanization:Most rubber products...

  • Stevenson Plan
    Stevenson Plan
    The Stevenson Plan, also known as the Stevenson Restriction Scheme, was an effort by the British government to stabilize low rubber prices resulting from a glut of rubber following World War I.-Background:...

    , historical British plan to stabilize rubber prices
  • Charles Greville Williams
    Charles Greville Williams
    Charles H. Greville Williams , was an English Scientist and analytical Chemist who published many scientific papers . He was born at Cheltenham, Gloucestershire...

    , researched natural rubber being a polymer of the monomer isoprene

Sources

  • Rubbery Materials and their Compounds by J.A Brydson
  • Rubber Technology by Maurice Morton

External links


History

Associations

Other