Wikipedia

Natural rubber

(Redirected fromRubber)
"Rubber" and "India rubber" redirect here. For other uses, seeRubber (disambiguation).
"Caoutchouc" redirects here. For the painting by Francis Picabia, seeCaoutchouc (Picabia).
This article is about the polymeric material "natural rubber". For human-made rubber materials, seeSynthetic rubber.

Rubber,also calledIndia rubber,latex,Amazonian rubber,caucho,orcaoutchouc,[1]as initially produced, consists ofpolymersof the organic compoundisoprene,with minor impurities of other organic compounds.Thailand,Malaysia,Indonesia,andCambodiaare four of the leading rubber producers.[2][3][4]

Photo of pieces of natural rubber in a glass jar.
Pieces of naturalvulcanizedrubber atHutchinson's Research and Innovation Center in France.
Latex being collected from atappedrubber tree,Cameroon
Rubber treeplantation inThailand

Types ofpolyisoprenethat are used as natural rubbers are classified aselastomers.

Currently, rubber is harvested mainly in the form of thelatexfrom thePará rubber tree(Hevea brasiliensis) or others. The latex is a sticky, milky and white colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex then is refined into the rubber that is ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup. The coagulated lumps are collected and processed into dry forms for sale.

Natural rubber is used extensively in many applications and products, either alone or in combination with other materials. In most of its useful forms, it has a large stretch ratio and high resilience and also is buoyant and water-proof.[5][6]

Industrial demand for rubber-like materials began to outstrip natural rubber supplies by the end of the 19th century, leading to the synthesis ofsynthetic rubberin 1909 by chemical means.[citation needed]

Varieties

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Amazonian rubber tree (Hevea brasiliensis)

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The major commercial source of natural rubber latex is the Amazonian rubber tree (Hevea brasiliensis),[1]a member of thespurgefamily,Euphorbiaceae.Once native to Brazil, the species is now pan-tropical. This species is preferred because it grows well under cultivation. A properly managed tree responds to wounding by producing more latex for several years.[citation needed]

Congo rubber (Landolphia owariensisandL. spp.)

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Congo rubber,formerly a major source of rubber, which motivated theatrocities in the Congo Free State,came from vines in the genusLandolphia(L. kirkii,L. heudelotis,andL. owariensis).[7]

Dandelion

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Dandelionmilk contains latex. The latex exhibits the same quality as the natural rubber fromrubber trees.In the wild types of dandelion, latex content is low and varies greatly. InNazi Germany,research projects tried to use dandelions as a base for rubber production, but failed.[8]In 2013, by inhibiting one key enzyme and using modern cultivation methods and optimization techniques, scientists in theFraunhofer Institute for Molecular Biology and Applied Ecology(IME) inGermanydeveloped a cultivar of the Kazakh dandelion (Taraxacum kok-saghyz) that is suitable for commercial production of natural rubber.[9]In collaboration withContinental Tires,IME began a pilot facility.

Other

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Many other plants produce forms of latex rich in isoprene polymers, though not all produce usable forms of polymer as easily as the Pará.[10]Some of them require more elaborate processing to produce anything like usable rubber, and most are more difficult to tap. Some produce other desirable materials, for examplegutta-percha(Palaquium gutta)[11]andchiclefromManilkaraspecies. Others that have been commercially exploited, or at least showed promise as rubber sources, include the rubber fig (Ficus elastica), Panama rubber tree (Castilla elastica), various spurges (Euphorbiaspp.),lettuce(Lactucaspecies), the relatedScorzonera tau-saghyz,variousTaraxacumspecies, including common dandelion (Taraxacum officinale) and Kazakh dandelion, and, perhaps most importantly for its hypoallergenic properties,guayule(Parthenium argentatum). The termgum rubberis sometimes applied to the tree-obtained version of natural rubber in order to distinguish it from the synthetic version.[12]

History

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See also:Rubber boom

The first use of rubber was by the indigenous cultures ofMesoamerica.The earliest archeological evidence of the use of natural latex from theHeveatreecomes from theOlmecculture, in which rubber was first used for making balls for theMesoamerican ballgame.Rubber was later used by theMayaandAzteccultures: in addition to making balls, Aztecs used rubber for other purposes, such as making containers and to make textiles waterproof by impregnating them with the latex sap.[13][14]

Charles Marie de La Condamineis credited with introducing samples of rubber to theAcadémie Royale des Sciencesof France in 1736.[15]In 1751, he presented a paper byFrançois Fresneauto the Académie (published in 1755) that described many of rubber's properties. This has been referred to as the first scientific paper on rubber.[15]In England,Joseph Priestley,in 1770, observed that a piece of the material was extremely good for rubbing offpencilmarks on paper, hence the name "rubber". It slowly made its way around England. In 1764, François Fresnau discovered thatturpentinewas a rubbersolvent.Giovanni Fabbroniis credited with the discovery ofnaphthaas a rubber solvent in 1779.[16][17]Charles Goodyearredevelopedvulcanizationin 1839, althoughMesoamericanshad used stabilized rubber for balls and other objects as early as 1600 BC.[18][19]

South America remained the main source of latex rubber used during much of the 19th century. The rubber trade was heavily controlled by business interests but no laws expressly prohibited the export of seeds or plants. In 1876,Henry Wickhamsmuggled 70,000 Amazonian rubber tree seeds from Brazil and delivered them toKew Gardens,England. Only 2,400 of these germinated. Seedlings were then sent toIndia,British Ceylon(Sri Lanka),Dutch East Indies(Indonesia),Singapore,andBritish Malaya.Malaya (nowPeninsular Malaysia) was later to become the biggest producer of rubber.[20]

In the early 1900s, theCongo Free Statein Africa was also a significant source of natural rubber latex, mostly gathered byforced labor.[21]King Leopold II's colonial state brutally enforced production quotas due to the high price of natural rubber at the time.[22]Tactics to enforce the rubber quotas included removing the hands of victims to prove they had been killed. Soldiers often came back from raids with baskets full of chopped-off hands. Villages that resisted were razed to encourage better compliance locally.[22][23](SeeAtrocities in the Congo Free Statefor more information on the rubber trade in the Congo Free State in the late 1800s and early 1900s.)

The rubber boom in the Amazon also similarly affected indigenous populations to varying degrees. Correrias, or slave raids were frequent in Colombia, Peru and Bolivia where many were either captured or killed. The most well known case of atrocities generated from rubber extraction in South America came from thePutumayo genocide.Between the 1880s–1913Julio César Aranaand his company that would become the Peruvian Amazon Company controlled the Putumayo river. W.E. Hardenburg,Benjamin Saldaña RoccaandRoger Casementwere influential figures in exposing these atrocities. Roger Casement was also prominent in revealing the Congo atrocities to the world. Days before entering Iquitos by boat Casement wrote "'Caoutchouc was first called 'india rubber,' because it came from the Indies, and the earliest European use of it was to rub out or erase. It is now called India rubber because it rubs out or erases the Indians."[24][25]

"Enslaved natives with a load of rubber weighing 75 kilos, they have journeyed 100 kilometers with no food given"

InIndia,commercial cultivation was introduced by British planters, although the experimental efforts to grow rubber on a commercial scale were initiated as early as 1873 at theCalcutta Botanical Garden.The first commercialHeveaplantations were established at Thattekadu inKeralain 1902. In later years the plantation expanded toKarnataka,Tamil Naduand theAndaman and Nicobar Islandsof India. Today, India is the world's 3rd largest producer and 4th largest consumer of rubber.[26]

In Singapore and Malaya, commercial production was heavily promoted bySir Henry Nicholas Ridley,who served as the first Scientific Director of theSingapore Botanic Gardensfrom 1888 to 1911. He distributed rubber seeds to many planters and developed the first technique for tapping trees for latex without causing serious harm to the tree.[27]Because of his fervent promotion of this crop, he is popularly remembered by the nickname "Mad Ridley".[28]

Pre–World War II

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Before World War II significant uses included door and window profiles, hoses, belts, gaskets,matting,flooring, and dampeners (antivibration mounts) for theautomotiveindustry. The use of rubber in cartires(initially solid rather than pneumatic) in particular consumed a significant amount of rubber.Gloves(medical, household, and industrial) and toyballoonswere large consumers of rubber, although the type of rubber used is concentrated latex. Significant tonnage of rubber was used asadhesivesin many manufacturing industries and products, although the two most noticeable were the paper and the carpet industries. Rubber was commonly used to makerubber bandsand pencilerasers.

Rubber produced as a fiber, sometimes called 'elastic', had significant value to the textile industry because of its excellent elongation and recovery properties. For these purposes, manufactured rubber fiber was made as either an extruded round fiber or rectangular fibers cut into strips from extruded film. Because of its low dye acceptance, feel and appearance, the rubber fiber was either covered by yarn of another fiber or directly woven with other yarns into the fabric. 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. The textile industry turned toneoprene(polymer ofchloroprene), a type of synthetic rubber, as well as another more commonly used elastomer fiber,spandex(also known as elastane), because of their superiority to rubber in both strength and durability.

Properties

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Rubber latex

Rubber exhibits unique physical and chemical properties. Rubber's stress–strain behavior exhibits theMullins effectand thePayne effectand is often modeled ashyperelastic.Rubberstrain crystallizes.Because there are weakenedallylicC-H bonds in eachrepeat unit,natural rubber is susceptible tovulcanisationas well as being sensitive toozone cracking.The two mainsolventsfor rubber areturpentineandnaphtha(petroleum). Because rubber does not dissolve easily, the material is finely divided by shredding prior to its immersion. Anammonia solutioncan be used to prevent thecoagulationof raw latex. Rubber begins to melt at approximately 180 °C (356 °F).

Elasticity

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Main article:Rubber elasticity
Rubber latex elasticity

On a microscopic scale, relaxed rubber is a disorganized cluster of erratically changing wrinkled chains. In stretched rubber, the chains are almost linear. The restoring force is due to the preponderance of wrinkled conformations over more linear ones. For the quantitative treatment seeideal chain,for more examples seeentropic force.

Cooling below theglass transition temperaturepermits local conformational changes but a reordering is practically impossible because of the largerenergy barrierfor the concerted movement of longer chains. "Frozen" rubber's elasticity is low andstrainresults from small changes ofbondlengths and angles: this caused theChallengerdisaster,when the AmericanSpace Shuttle's flattenedo-ringsfailed to relax to fill a widening gap.[29]The glass transition is fast and reversible: the force resumes on heating.

The parallel chains of stretched rubber are susceptible to crystallization. This takes some time because turns of twisted chains have to move out of the way of the growingcrystallites.Crystallization has occurred, for example, when, after days, an inflated toy balloon is found withered at a relatively large remaining volume. Where it is touched, it shrinks because the temperature of the hand is enough to melt the crystals.

Vulcanizationof rubber createsdi-andpolysulfidebonds between chains, which limits thedegrees of freedomand results in chains that tighten more quickly for a given strain, thereby increasing the elastic force constant and making the rubber harder and less extensible.

Malodour

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Raw rubber storage depots and rubber processing can produce malodour that is serious enough to become a source of complaints and protest to those living in the vicinity.[30]Microbial impurities originate during the processing of block rubber. These impurities break down during storage or thermal degradation and produce volatile organic compounds. Examination of these compounds usinggas chromatography/mass spectrometry(GC/MS) and gas chromatography (GC) indicates that they contain sulfur, ammonia,alkenes,ketones,esters,hydrogen sulfide,nitrogen, and low-molecular-weight fatty acids (C2–C5).[31][32]When latex concentrate is produced from rubber,sulfuric acidis used for coagulation. This produces malodourous hydrogen sulfide.[32]The industry can mitigate these bad odours withscrubber systems.[32]

Chemical makeup

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Chemical structure of cis-polyisoprene, the main constituent of natural rubber. Synthetic cis-polyisoprene and natural cis-polyisoprene are derived from distinct precursors,isopentenyl pyrophosphateandisoprene.

Rubber is the polymer cis-1,4-polyisoprene – with amolecular weightof 100,000 to 1,000,000daltons.Typically, a small percentage (up to 5% of dry mass) of other materials, such asproteins,fatty acids,resins,and inorganic materials (salts) are found in natural rubber. Polyisoprene can also be created synthetically, producing what is sometimes referred to as "synthetic natural rubber", but the synthetic and natural routes are distinct.[12]Some natural rubber sources, such asgutta-percha,are composed of trans-1,4-polyisoprene, astructural isomerthat has similar properties. Natural rubber is an elastomer and athermoplastic.Once the rubber is vulcanized, it is athermoset.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. The final properties of a rubber item depend not just on the polymer, but also on modifiers and fillers, such ascarbon black,factice,whiting and others.

Biosynthesis

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Rubber particles are formed in thecytoplasmof specialized latex-producing cells calledlaticiferswithin rubber plants.[33]Rubber particles are surrounded by a singlephospholipidmembrane withhydrophobictails pointed inward. The membrane allows biosynthetic proteins to be sequestered at the surface of the growing rubber particle, which allows new monomeric units to be added from outside the biomembrane, but within the lacticifer. The rubber particle is an enzymatically active entity that contains three layers of material, the rubber particle, a biomembrane and free monomeric units. The biomembrane is held tightly to the rubber core by the high negative charge along the double bonds of the rubber polymer backbone.[34]Free monomeric units and conjugated proteins make up the outer layer. The rubber precursor isisopentenyl pyrophosphate(anallyliccompound), which elongates by Mg2+-dependent condensation by the action of rubber transferase. The monomer adds to the pyrophosphate end of the growing polymer.[citation needed]The process displaces the terminal high-energy pyrophosphate. The reaction produces a cis polymer. The initiation step is catalyzed byprenyltransferase,which converts three monomers of isopentenyl pyrophosphate intofarnesyl pyrophosphate.[35]The farnesyl pyrophosphate can bind to rubber transferase to elongate a new rubber polymer.

The required isopentenyl pyrophosphate is obtained from themevalonatepathway, which derives fromacetyl-CoAin thecytosol.In plants, isoprene pyrophosphate can also be obtained from the 1-deox-D-xyulose-5-phosphate/2-C-methyl-D-erythritol-4-phosphate pathway within plasmids.[36]The relative ratio of the farnesyl pyrophosphate initiator unit and isoprenyl pyrophosphate elongation monomer determines the rate of new particle synthesis versus elongation of existing particles. Though rubber is known to be produced by only one enzyme, extracts of latex host numerous small molecular weight proteins with unknown function. The proteins possibly serve as cofactors, as the synthetic rate decreases with complete removal.[37]

Production

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Rubber is generally cultivated in large plantations. The image shows a coconut shell used in collecting latex, in plantations inKerala,India.
Sheets of natural rubber

More than 28 million tons of rubber were produced in 2017, of which approximately 47% was natural. Since the bulk is synthetic, which is derived from petroleum, the price of natural rubber is determined, to a large extent, by the prevailing global price of crude oil.[38][39]Asia was the main source of natural rubber, accounting for about 90% of output in 2021.[40]The three largest producers,Thailand,Indonesia,[41]and Malaysia, together account for around 72% of all natural rubber production.[when?][citation needed]Natural rubber is not cultivated widely in its native continent of South America because of the South American leafblight,and other natural predators there.

Cultivation

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Rubber latex is extracted from rubber trees. The economic life of rubber trees in plantations is around 32 years, with up to 7 years being an immature phase and about 25 years of productive phase.

The soil requirement is well-drained, weathered soil consisting oflaterite,lateritic types, sedimentary types, nonlateritic red oralluvialsoils.

The climatic conditions for optimum growth of rubber trees are:

  • Rainfall of around 250 centimetres (98 in) evenly distributed without any marked dry season and with at least 100 rainy days per year
  • Temperature range of about 20 to 34 °C (68 to 93 °F), with a monthly mean of 25 to 28 °C (77 to 82 °F)
  • Atmospheric humidity of around 80%
  • About 2,000 hours sunshine per year at the rate of six hours per day throughout the year
  • Absence of strong winds

Many high-yielding clones have been developed for commercial planting. These clones yield more than 2,000 kilograms per hectare (1,800 lb/acre) of dry rubber per year, under ideal conditions.

Rubber production has been linked to deforestation. Rubber therefore is one of seven commodities included in the 2023EU Regulation on Deforestation-free products(EUDR), which aims to guarantee that the productsEuropean Union(EU) citizens consume do not contribute to deforestation orforest degradationworldwide.[42]

Collection

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Main article:Rubber tapping
Vintage tobacco card, Tapping a Rubber Tree, India, Products of the World series, Player's Cigarettes, 1909

In places such as Kerala and Sri Lanka, where coconuts are in abundance, the half shell of coconut was used as the latex collection container. Glazed pottery or aluminium or plastic cups became more common inKerala-Indiaand other countries. 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 agalvanised"spout" knocked into the bark.Rubber tappingnormally 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 on alternate or third days, although many variations in timing, length and number of cuts are used. "Tappers would make a slash in the bark with a small hatchet. These slanting cuts allowed latex to flow from ducts located on the exterior or the inner layer of bark (cambium) of the tree. Since the cambium controls the growth of the tree, growth stops if it is cut. Thus, rubber tapping demanded accuracy, so that the incisions would not be too many given the size of the tree, or too deep, which could stunt its growth or kill it. "[43]

A woman inSri Lankaharvesting rubber, c. 1920

It is usual to tap a panel at least twice, sometimes three times, during the tree's 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-containing 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 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 and then start collecting the liquid "field latex" at about midday.

Field coagula

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Mixed field coagula.

The four types of field coagula are "cuplump", "treelace", "smallholders' lump", and "earth scrap". Each has significantly different properties.[44]Some trees continue to drip after the collection leading to a small amount of "cup lump" that 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. Latex that drips onto the ground, "earth scrap", is also collected periodically for processing of low-grade product.

Cup lump
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Cup lump rubber coagula in aMyanmarroad stall.

Cup lump is the coagulated material found in the collection cup when the tapper next visits the tree to tap it again. It arises from latex clinging to the walls of the cup after the latex was last poured into the bucket, and from late-dripping latex exuded before the latex-carrying vessels of the tree become blocked. It is of higher purity and of greater value than the other three types.

'Cup lumps' can also be used to describe a completely different type of coagulate that has collected in smallholder plantations over a period of 1–2 weeks. After tapping all of the trees, the tapper will return to each tree and stir in some type of acid, which allows the newly harvested latex to mix with the previously coagulated material. The rubber/acid mixture is what gives rubber plantations, markets, and factories a strong odor.

Tree lace
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Tree lace is the coagulum strip that the tapper peels off the previous cut before making a new cut. It usually has higher copper and manganese contents than cup lump. Both copper and manganese are pro-oxidants and can damage the physical properties of the dry rubber.

Smallholders' lump
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Smallholders' lump is produced by smallholders, who collect rubber from trees far from the nearest factory. Many Indonesian smallholders, who farm paddies in remote areas, tap dispersed trees on their way to work in the paddy fields and collect the latex (or the coagulated latex) on their way home. As it is often impossible to preserve the latex sufficiently to get it to a factory that processes latex in time for it to be used to make high quality products, and as the latex would anyway have coagulated by the time it reached the factory, the smallholder will coagulate it by any means available, in any container available. Some smallholders use small containers, buckets etc., but often the latex is coagulated in holes in the ground, which are usually lined with plastic sheeting. Acidic materials and fermented fruit juices are used to coagulate the latex – a form of assisted biological coagulation. Little care is taken to exclude twigs, leaves, and even bark from the lumps that are formed, which may also include tree lace.

Earth scrap
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Earth scrap is material that gathers around the base of the tree. It arises from latex overflowing from the cut and running down the bark, from rain flooding a collection cup containing latex, and from spillage from tappers' buckets during collection. It contains soil and other contaminants, and has variable rubber content, depending on the amount of contaminants. Earth scrap is collected by field workers two or three times a year and may be cleaned in a scrap-washer to recover the rubber, or sold to a contractor who cleans it and recovers the rubber. It is of low quality.

Processing

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Removing coagulum from coagulating troughs.

Latex coagulates in the cups if kept for long and must be collected before this happens. The collected latex, "field latex", is transferred into coagulation tanks for the preparation of dry rubber or transferred into air-tight containers with sieving for ammoniation. Ammoniation, invented by patent lawyer and vice-president of theUnited States Rubber CompanyErnest Hopkinson around 1920, preserves the latex in a colloidal state for longer periods of time. Latex is generally processed into either latex concentrate for manufacture of dipped goods or 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. Processing for these grades is a size reduction and cleaning process to remove contamination and prepare the material for the final stage of drying.[45]

The dried material is then baled and palletized for storage and shipment.

Molecular structure

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Rubber is a natural polymer ofisoprene(polyisoprene), and anelastomer(a stretchy polymer). Polymers are simply chains of molecules that can be linked together. Rubber is one of the few naturally occurring polymers and prized for its high stretch ratio, resilience, and water-proof properties. Other examples of natural polymers includetortoise shell,amber,andanimal horn.[46]When harvested, latex rubber takes the form of latex, an opaque, white, milky suspension of rubber particles in water. It is then transformed through industrial processes to the solid form widely seen in manufactured goods.

Vulcanized rubber

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Main article:Sulfur vulcanization
Torn latex rubber dry suit wrist seal

Natural rubber is reactive and vulnerable to oxidization, but it can be stabilized through a heating process called vulcanization. Vulcanization is a process by which the rubber is heated andsulfur,peroxide,orbisphenolare added to improve resistance andelasticityand to prevent it from oxidizing.Carbon black,which can be derived from a petroleum refinery or other natural incineration processes, is sometimes used as an additive to rubber to improve its strength, especially in vehicle tires.[47][48]

During vulcanization, rubber's polyisoprene molecules (long chains of isoprene) are heated and cross-linked with molecular bonds to sulfur, forming a 3-D matrix. The optimal percentage of sulfur is approximately 10%. In this form, the polyisoprene molecules orientation is still random but they become aligned when the rubber is stretched. This sulfur vulcanization makes the rubber stronger and more rigid, but still very elastic.[49]And through the vulcanization process, the sulfur and latex are meant to be totally used up in individual form.

Transportation

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Natural rubber latex is shipped from factories inSoutheast Asia,South America,andWestandCentral Africato destinations around the world. As the cost of natural rubber has risen significantly and rubber products are dense, the shipping methods offering the lowest cost per unit weight are preferred. Depending on destination, warehouse availability, and transportation conditions, some methods are preferred by certain buyers. In international trade, latex rubber is mostly shipped in 20-foot ocean containers. Inside the container, smaller containers are used to store the latex.[50]

Rubber shortage and global economics

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There is growing concern for the future supply of rubber due to various factors, including plant disease, climate change, and the volatile market price of rubber.[51][52][53][54]Producers of natural rubber are mostly small family-held plantations, often serving large industrial aggregators. High volatility in the price of rubber affects rubber plantation investment, and farmers may remove their rubber trees if the international market spot price of a seemingly more profitable crop (for examplepalm oil) surges in relation to rubber.

For instance, during the 2020 and 2021 internationalCOVID-19 pandemic,demand forrubber glovessurged, leading to a spike in rubber prices of about 30%. In addition to the pandemic, demand exceeded supply in part because long term plantations had been torn out and replaced with other crops over the previous 5–10 years, and other areas were affected by climate-fueled natural disasters. In this environment, producers did increase their prices in keeping with supply and demand dynamics, putting upward price pressure on the whole downstream supply chain.[54]

Uses

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Compression molded (cured)rubber bootsbefore theflashesare removed

Uncured rubber is used for cements;[55]for adhesive, insulating, and friction tapes; and for crepe rubber used in insulating blankets and footwear.Vulcanized rubberhas many more applications. Resistance to abrasion makes softer kinds of rubber valuable for the treads of vehicle tires and conveyor belts, and makes hard rubber valuable for pump housings and piping used in the handling of abrasive sludge.

Theflexibilityof rubber is appealing in hoses, tires and rollers for devices ranging from domestic clothes wringers to printing presses; its elasticity makes it suitable for various kinds of shock absorbers and for specialized machinery mountings designed to reduce vibration. Its relative gasimpermeabilitymakes it useful in the manufacture of articles such as air hoses, balloons, balls and cushions. Theresistance of rubber to waterand to the action of most fluid chemicals has led to its use in rainwear, diving gear, and chemical and medicinal tubing and as a lining for storage tanks, processing equipment and railroad tank cars. Because of theirelectrical resistance,soft rubber goods are used as insulation and for protective gloves, shoes, and blankets;hard rubberis used for articles such as telephone housings and parts for radio sets, meters, and other electrical instruments. The coefficient offrictionof rubber, which is high on dry surfaces and low on wet surfaces, leads to its use forpower-transmission belting,highly flexible couplings,[56]and for water-lubricated bearings in deep-well pumps. Indian rubber balls orlacrosse ballsare made of rubber.

Compression molding machine for rubber parts

Around 25 million tonnes of rubber are produced each year, of which 30 percent is natural.[57]The remainder is synthetic rubber derived from petrochemical sources. The top end of latex production results in latex products such as surgeons' gloves, balloons, and other relatively high-value products. The mid-range which comes from the technically specified natural rubber materials ends up largely in tires but also in conveyor belts, marine products, windshield wipers, and miscellaneous goods. Natural rubber offers good elasticity, while synthetic materials tend to offer better resistance to environmental factors such as oils, temperature, chemicals, and ultraviolet light. "Cured rubber" is rubber that has been compounded and subjected to the vulcanisation process to create cross-links within the rubber matrix. Rubber can be added to cement to improve its properties.[58]

Allergic reactions

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Main article:Latex allergy

Some people have a seriouslatex allergy,and exposure to natural latex rubber products such aslatex glovescan causeanaphylactic shock.Theantigenic proteinsfound inHevealatex are greatly reduced by about 99.9 percent (though not eliminated)[59]through vulcanization processing.

Latex from non-Heveasources, such asguayule,can be used without allergic reaction by persons with an allergy toHevealatex.[60]

Some allergic reactions are not to the latex itself, but from residues of chemicals used to accelerate the cross-linking process. Although this may be confused with an allergy to latex, it is distinct from it, typically taking the form ofType IV hypersensitivityin the presence of traces of specific processing chemicals.[59][61]

Microbial degradation

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Natural rubber is susceptible to degradation by a wide range of bacteria.[62][63][64][65][66][67][68][69] The bacteriaStreptomyces coelicolor,Pseudomonas citronellolis,andNocardiaspp. are capable of degrading vulcanized natural rubber.[70]

See also

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References

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Citations

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  1. ^abDunstan, Wyndham Rowland (1911)."Rubber".InChisholm, Hugh(ed.).Encyclopædia Britannica.Vol. 23 (11th ed.). Cambridge University Press. p. 795.
  2. ^Sirimaporn Leepromrath, et al. "Rubber crop diversity and its influential factors in Thailand."Journal of Rubber Research24.3 (2021): 461–473.
  3. ^Muhammad Fadzli Ali, et al., "The dynamics of rubber production in Malaysia: Potential impacts, challenges and proposed interventions."Forest Policy and Economics127 (2021): 102449.
  4. ^Fadhlan Zuhdi, "The Indonesian natural rubber export competitiveness in global market."International Journal of Agriculture System8.2 (2021): 130–139online.
  5. ^Dananjaya, Vimukthi; Somarathna, Yashoda; Siriwardena, Susantha; Sirimuthu, Narayana; Karunanayake, Laleen; Abeykoon, Chamil (1 May 2024)."Effects of latex type and processed-mica waste loading on the structural and thermo-physical properties of natural rubber latex foam composites".International Journal of Lightweight Materials and Manufacture.7(3): 450–466.doi:10.1016/j.ijlmm.2023.12.002.ISSN2588-8404.
  6. ^Phomrak, Sirilak; Nimpaiboon, Adun; Newby, Bi-min Zhang; Phisalaphong, Muenduen (29 August 2020)."Natural Rubber Latex Foam Reinforced with Micro- and Nanofibrillated Cellulose via Dunlop Method".Polymers.12(9): 1959.doi:10.3390/polym12091959.ISSN2073-4360.PMC7565547.PMID32872461.
  7. ^Legner, Erich Fred."Rubber and Other Latex Products".University of California, Riverside.
  8. ^Heim, Susanne(2002).Autarkie und Ostexpansion: Pflanzenzucht und Agrarforschung im Nationalsozialismus.Wallstein Verlag.ISBN978-3-89244-496-1.
  9. ^"Making Rubber from Dandelion Juice".Science Daily.28 October 2013.Retrieved22 November2013.
  10. ^Smith, James P. Jr/ (2006)."Plants & Civilization: An Introduction to the Interrelationships of Plants and People. Section 8.4, Latex Plants".Humboldt State University Botanical Studies Open Educational Resources and Data, Humboldt State University Digital Commons.pp. 137–141.Retrieved8 June2019.
  11. ^Burns, Bill."The Gutta Percha Company".History of the Atlantic Cable & Undersea Communications.Retrieved14 February2009.
  12. ^abHeinz-Hermann Greve "Rubber, 2. Natural" inUllmann's Encyclopedia of Industrial Chemistry,2000, Wiley-VCH, Weinheim.doi:10.1002/14356007.a23_225
  13. ^Emory Dean Keoke, Kay Marie Porterfield. 2009. Encyclopedia of American Indian Contributions to the World: 15,000 Years of Inventions and Innovations. Infobase Publishing
  14. ^Tully, John (2011).The Devil's Milk: A Social History of Rubber.NYU Press.ISBN978-1-58367-260-0.
  15. ^ab"Charles Marie de la Condamine".bouncing-balls.com.
  16. ^"Oops There Goes Another Rubber Tree Plant: the History of Natural Rubber".Petroleum Service Company.Retrieved20 April2024.
  17. ^"Rubber | Metallurgy for Dummies".Retrieved20 April2024.
  18. ^Hosler, D.; Burkett, S.L.; Tarkanian, M.J. (1999). "Prehistoric polymers: Rubber processing in ancient Mesoamerica".Science.284(5422): 1988–1991.doi:10.1126/science.284.5422.1988.PMID10373117.
  19. ^Slack, Charles (2002).Noble obsession: Charles Goodyear, Thomas Hancock, and the race to unlock the greatest industrial secret of the nineteenth century.Hyperion.ISBN978-0-7868-6789-9.
  20. ^Jackson, Joe (2008).The Thief at the End of the World.Viking.ISBN978-0-670-01853-6.
  21. ^"Belgian King Establishes Congo Free State".education.nationalgeographic.org.Retrieved20 April2024.
  22. ^ab"King Leopold's ghost: The legacy of labour coercion in the DRC".CEPR.14 August 2019.Retrieved20 April2024.
  23. ^"Young Boy Forced to Collect Rubber · Antislavery Usable Past".antislavery.ac.uk.Retrieved20 April2024.
  24. ^Goodman, Jordan (2009).The Devil and Mr Casement.Verso. p. 83.ISBN978-1-84467-334-6.Retrieved13 August2023.
  25. ^Casement, Roger (1997).The Amazon Journal of Roger Casement.Anaconda Editions. p. 85.ISBN1-901990-00-1.Retrieved13 August2023.
  26. ^"Natural rubber in India".Archived fromthe originalon 1 October 2016.
  27. ^Cornelius-Takahama, Vernon (2001)."Sir Henry Nicholas Ridley".Singapore Infopedia.Archived fromthe originalon 4 May 2013.Retrieved9 February2013.
  28. ^Leng, Dr Loh Wei; Keong, Khor Jin (19 September 2011)."Mad Ridley and the rubber boom".Malaysia History.Archived fromthe originalon 27 July 2013.Retrieved9 February2013.
  29. ^"Casing Joint Design"(PDF).Report – Investigation of the Challenger Accident.US Government Printing Office.Archived(PDF)from the original on 9 October 2022.Retrieved29 August2015.
  30. ^Nur Fadhilah Idris; Nor Hidayaty Kamarulzaman; Zairossani Mohd Nor (2012)."Determination of Volatile Fatty Acids from Raw Natural Rubber Drying Activity by Thermal Desorption-Gas Chromatography"(PDF).Chemical Engineering Transactions.30.doi:10.3303/CET1230030.S2CID7469231.Archived fromthe original(PDF)on 15 December 2017.Retrieved14 December2017.
  31. ^Hoven, Vipavee P.; Rattanakaran, Kesinee; Tanaka, Yasuyuki (1 November 2003). "Determination of Chemical Components that Cause Mal-Odor from Natural Rubber".Rubber Chemistry and Technology.76(5): 1128–1144.doi:10.5254/1.3547792.
  32. ^abc"Info"(PDF).aidic.it.Archived(PDF)from the original on 9 October 2022.
  33. ^Koyama, Tanetoshi; Steinbüchel, Alexander, eds. (June 2011)."Biosynthesis of Natural Rubber and Other Natural Polyisoprenoids".Polyisoprenoids.Biopolymers. Vol. 2. Wiley-Blackwell. pp. 73–81.ISBN978-3-527-30221-5.
  34. ^Paterson-Jones, J.C.; Gilliland, M.G.; Van Staden, J. (June 1990). "The Biosynthesis of Natural Rubber".Journal of Plant Physiology.136(3): 257–263.Bibcode:1990JPPhy.136..257P.doi:10.1016/S0176-1617(11)80047-7.ISSN0176-1617.
  35. ^Xie, W.; McMahan, C.M.; Distefano, A.J. DeGraw, M.D.; et al. (2008)."Initiation of rubber synthesis: In vitro comparisons of benzophenone-modified diphosphate analogues in three rubber producing species".Phytochemistry.69(14): 2539–2545.Bibcode:2008PChem..69.2539X.doi:10.1016/j.phytochem.2008.07.011.PMID18799172.Archived fromthe originalon 2 October 2021.Retrieved24 November2019.{{cite journal}}:CS1 maint: multiple names: authors list (link)
  36. ^Casey, P.J.; Seabra, M.C. (1996)."Protein Prenyltransferases".Journal of Biological Chemistry.271(10): 5289–5292.doi:10.1074/jbc.271.10.5289.PMID8621375.
  37. ^Kang, H.; Kang, M.Y.; Han, K.H. (2000)."Identification of Natural Rubber and Characterization of Biosynthetic Activity".Plant Physiol.123(3): 1133–1142.doi:10.1104/pp.123.3.1133.PMC59076.PMID10889262.
  38. ^"Overview of the Causes of Natural Rubber Price Volatility".En.wlxrubber.com. 1 February 2010. Archived fromthe originalon 26 May 2013.Retrieved21 March2013.
  39. ^"Statistical Summary of World Rubber Situation"(PDF).International Rubber Study Group. December 2018.Archived(PDF)from the original on 5 February 2019.Retrieved5 February2019.
  40. ^"Natural rubber leading producers worldwide 2021".Statista.Retrieved18 February2023.
  41. ^Listiyorini, Eko (16 December 2010)."Rubber Exports From Indonesia May Grow 6%–8% Next Year".bloomberg.com. Archived fromthe originalon 4 November 2012.Retrieved21 March2013.
  42. ^"Regulation on Deforestation-free products".European Union.Retrieved24 July2024.
  43. ^Keoke, Emory (2003).Encyclopedia of American Indian contributions to the world 15,000 years of inventions and innovations.Checkmark Books. p. 156.
  44. ^This section has been copied almost verbatim from thepublic domainUNFood and Agriculture Organization(FAO), ecoport.com article:Cecil, John; Mitchell, Peter; Diemer, Per; Griffee, Peter (2013)."Processing of Natural Rubber, Manufacture of Latex-Grade Crepe Rubber".ecoport.org.FAO, Agricultural and Food Engineering Technologies Service.Retrieved19 March2013.
  45. ^Basic Rubber Testing.ASTM International. pp. 6–. GGKEY:8BT2U3TQN7G.
  46. ^"Science of Plastics".Science History Institute.18 July 2016.Retrieved18 February2023.
  47. ^Schuster, Jens; Lutz, Johannes; Shaik, Yousuf Pasha; Yadavalli, Venkat Reddy (1 October 2022)."Recycling of fluoro-carbon-elastomers – A review".Advanced Industrial and Engineering Polymer Research.Recycling of Rubbers.5(4): 248–254.doi:10.1016/j.aiepr.2022.08.002.ISSN2542-5048.S2CID251658624.
  48. ^Asaro, Lucia; Gratton, Michel; Seghar, Saïd; Aït Hocine, Nourredine (1 June 2018). "Recycling of rubber wastes by devulcanization".Resources, Conservation and Recycling.133:250–262.Bibcode:2018RCR...133..250A.doi:10.1016/j.resconrec.2018.02.016.ISSN0921-3449.S2CID115671283.
  49. ^Ducháček, Vratislav; Kuta, Antonín (October 1986). "Long-time sulfenamide-accelerated sulfur vulcanization of natural rubber/chlorobutyl rubber compounds".Journal of Applied Polymer Science.32(5): 4849–4855.doi:10.1002/app.1986.070320507.ISSN0021-8995.
  50. ^Transportation of Natural Rubber– Industry Source
  51. ^Espinoza, Mauricio (1 November 2012)."US seeks domestic rubber as global shortage worsens".Ohio State University.Retrieved13 March2021.The importance of developing alternative sources of natural rubber becomes clear when considering that there has been a shortage in the supply of this critical resource every year since 2004. By 2020, the global shortfall of natural rubber is projected to be more than the entire amount (1.2 million metric tonnes) the U.S. imports every year.
  52. ^"Natural rubber shortage".The Rubber Economist.Retrieved13 March2021.
  53. ^Meyer, Robert (9 September 2019)."Situation Report: The looming crisis of natural rubber. The Chief Executive's view".Retrieved13 March2021.
  54. ^abSwain, Frank (8 March 2021)."The wonder material we all need but is running out:Climate change, capitalism and disease are threatening to strike a mortal blow to the world's rubber trees. Do we need to find alternative sources of rubber before it's too late?".BBC Future.Retrieved13 March2021.
  55. ^Horath, Larry (2017).Fundamentals of Materials Science for Technologists: Properties, Testing, and Laboratory Exercises(2nd ed.). Waveland Press.ISBN978-1-4786-3518-5.
  56. ^VULKAN Couplings System Competence – Compound Research,22 November 2016,archivedfrom the original on 11 December 2021,retrieved9 June2021
  57. ^"Rubber Faqs".Archived fromthe originalon 13 September 2016.
  58. ^Liu, Luqing; Wang, Chaohui; Liang, Qing; Chen, Feng; Zhou, Xiaolei (15 March 2023)."A state-of-the-art review of rubber modified cement-based materials: Cement stabilized base".Journal of Cleaner Production.392:136270.Bibcode:2023JCPro.39236270L.doi:10.1016/j.jclepro.2023.136270.ISSN0959-6526.S2CID256564049.
  59. ^ab"Premarket Notification [510(k)] Submissions for Testing for Skin Sensitization To Chemicals in Natural Rubber Products"(PDF).FDA.Retrieved22 September2013.
  60. ^"New Type of Latex Glove Cleared".Food and Drug Administration.
  61. ^American Latex Allergy Association."Allergy Fact Sheet".Archived fromthe originalon 13 March 2012.Retrieved22 September2013.
  62. ^Rook, J.J. (1955)."Microbiological deterioration of vulcanized rubber".Appl. Microbiol.3(5): 302–309.doi:10.1128/aem.3.5.302-309.1955.PMC1057125.PMID13249390.
  63. ^Leeang, K.W.H. (1963). "Microbiologic degradation of rubber".J. Am. Water Works Assoc.53(12): 1523–1535.Bibcode:1963JAWWA..55l1523L.doi:10.1002/j.1551-8833.1963.tb01176.x.
  64. ^Tsuchii, A.; Suzuki, T.; Takeda, K. (1985)."Microbial degradation of natural rubber vulcanizates".Appl. Environ. Microbiol.50(4): 965–970.Bibcode:1985ApEnM..50..965T.doi:10.1128/AEM.50.4.965-970.1985.PMC291777.PMID16346923.
  65. ^Heisey, R.M.; Papadatos, S. (1995)."Isolation of microorganisms able to metabolize puri¢ed natural rubber".Appl. Environ. Microbiol.61(8): 3092–3097.Bibcode:1995ApEnM..61.3092H.doi:10.1128/AEM.61.8.3092-3097.1995.PMC1388560.PMID16535106.
  66. ^Jendrossek, D.; Tomasi, G.; Kroppenstedt, R.M. (1997). "Bacterial degradation of natural rubber: a privilege of actinomycetes?".FEMS Microbiology Letters.150(2): 179–188.doi:10.1016/s0378-1097(97)00072-4(inactive 20 April 2024).PMID9170260.{{cite journal}}:CS1 maint: DOI inactive as of April 2024 (link)
  67. ^Linos, A. and Steinbuchel, A. (1998) Microbial degradation of natural and synthetic rubbers by novel bacteria belonging to the genus Gordona. Kautsch. Gummi Kunstst. 51, 496–499.
  68. ^Linos, Alexandros; Steinbuchel, Alexander; Spröer, Cathrin; Kroppenstedt, Reiner M. (1999)."Gordonia polyisoprenivorans sp. nov., a rubber degrading actinomycete isolated from automobile tire".Int. J. Syst. Bacteriol.49(4): 1785–1791.doi:10.1099/00207713-49-4-1785.PMID10555361.
  69. ^Linos, Alexandros; Reichelt, Rudolf; Keller, Ulrike; Steinbuchel, Alexander (October 1999)."A Gram-negative bacterium, identified as Pseudomonas aeruginosa AL98, is a potent degrader of natural rubber and synthetic cis-1,4-polyisoprene".FEMS Microbiology Letters.182(1): 155–161.doi:10.1111/j.1574-6968.2000.tb08890.x.PMID10612748.
  70. ^Helge B. Bode; Axel Zeeck; Kirsten Plückhahn; Dieter Jendrossek (September 2000)."Physiological and Chemical Investigations into Microbial Degradation of Synthetic Poly(cis-1,4-isoprene)".Applied and Environmental Microbiology.66(9): 3680–3685.Bibcode:2000ApEnM..66.3680B.doi:10.1128/AEM.66.9.3680-3685.2000.PMC92206.PMID10966376.

Sources

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  • Ali, Muhammad Fadzli, et al. "The dynamics of rubber production in Malaysia: Potential impacts, challenges and proposed interventions."Forest Policy and Economics127 (2021): 102449.

Further reading

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  • Dean, Warren.(1997)Brazil and the Struggle for Rubber: A Study in Environmental History.Cambridge University Press.
  • Grandin, Greg.Fordlandia: The Rise and Fall of Henry Ford's Forgotten Jungle City.Picador Press 2010.ISBN978-0-312-42962-1
  • Weinstein, Barbara (1983)The Amazon Rubber Boom 1850–1920.Stanford University Press.
  • Tully, John A.The Devil's Milk; A Social History of Rubber.New York: Monthly Review Press, 2011.
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