Natural rubber - Wikipedia

Natural rubber – Wikipedia

Polymer harvested from sure timber

Photo of pieces of natural rubber in a glass jar.

Items of pure vulcanized rubber at Hutchinson’s Analysis and Innovation Middle in France.

Pure rubber, additionally referred to as India rubber, latex, Amazonian rubber, caucho or caoutchouc, as initially produced, consists of polymers of the natural compound isoprene, with minor impurities of different natural compounds, plus water. Thailand and Indonesia are two of the main rubber producers. Sorts of polyisoprene which can be used as pure rubbers are categorized as elastomers.

Presently, rubber is harvested primarily within the type of the latex from the rubber tree or others. The latex is a sticky, milky colloid drawn off by making incisions within the bark and accumulating the fluid in vessels in a course of referred to as “tapping”. The latex then is refined into rubber that’s prepared for business processing. In main areas, latex is allowed to coagulate within the assortment cup. The coagulated lumps are collected and processed into dry types on the market.

Pure rubber is used extensively in lots of purposes and merchandise, both alone or together with different supplies. In most of its helpful types, it has a big stretch ratio and excessive resilience, and is extraordinarily waterproof.

Varieties[edit]

Hevea brasiliensis[edit]

The foremost business supply of pure rubber latex is the Amazonian rubber tree (Hevea brasiliensis), a member of the spurge household, Euphorbiaceae. This species is most popular as a result of it grows effectively underneath cultivation. A correctly managed tree responds to wounding by producing extra latex for a number of years.[citation needed]

Congo rubber[edit]

Congo rubber, previously a serious supply of rubber, got here from vines within the genus Landolphia (L. kirkii, L. heudelotis, and L. owariensis).[1]

Dandelion[edit]

Dandelion milk comprises latex. The latex displays the identical high quality because the pure rubber from rubber timber. Within the wild varieties of dandelion, latex content material is low and varies vastly. In Nazi Germany, analysis tasks tried to make use of dandelions as a base for rubber manufacturing, however failed.[2] In 2013, by inhibiting one key enzyme and utilizing trendy cultivation strategies and optimization strategies, scientists within the Fraunhofer Institute for Molecular Biology and Utilized Ecology (IME) in Germany developed a cultivar of the Russian dandelion (Taraxacum kok-saghyz) that’s appropriate for business manufacturing of pure rubber.[3] In collaboration with Continental Tires, IME started a pilot facility.

Different[edit]

Many different vegetation produce types of latex wealthy in isoprene polymers, although not all produce usable types of polymer as simply because the Pará.[4] A few of them require extra elaborate processing to supply something like usable rubber, and most are tougher to faucet. Some produce different fascinating supplies, for instance gutta-percha (Palaquium gutta)[5] and chicle from Manilkara species. Others which have been commercially exploited, or a minimum of confirmed promise as rubber sources, embrace the rubber fig (Ficus elastica), Panama rubber tree (Castilla elastica), numerous spurges (Euphorbia spp.), lettuce (Lactuca species), the associated Scorzonera tau-saghyz, numerous Taraxacum species, together with widespread dandelion (Taraxacum officinale) and Russian dandelion, and maybe most significantly for its hypoallergenic properties, guayule (Parthenium argentatum). The time period gum rubber is typically utilized to the tree-obtained model of pure rubber in an effort to distinguish it from the artificial model.[6]

Historical past[edit]

The primary use of rubber was by the indigenous cultures of Mesoamerica. The earliest archeological proof of the usage of pure latex from the Hevea tree comes from the Olmec tradition, wherein rubber was first used for making balls for the Mesoamerican ballgame. Rubber was later utilized by the Maya and Aztec cultures – along with making balls Aztecs used rubber for different functions comparable to making containers and to make textiles waterproof by impregnating them with the latex sap.[7][8]

Charles Marie de La Condamine is credited with introducing samples of rubber to the Académie Royale des Sciences of France in 1736.[9] In 1751, he introduced a paper by François Fresneau to the Académie (printed in 1755) that described lots of rubber’s properties. This has been known as the primary scientific paper on rubber.[9] In England, Joseph Priestley, in 1770, noticed {that a} piece of the fabric was extraordinarily good for rubbing off pencil marks on paper, therefore the identify “rubber”. It slowly made its method round England. In 1764, François Fresnau found that turpentine was a rubber solvent. Giovanni Fabbroni is credited with the invention of naphtha as a rubber solvent in 1779.[citation needed]Charles Goodyear redeveloped vulcanization in 1839, though Mesoamericans had used stabilized rubber for balls and different objects as early as 1600 BC.[10][11]

South America remained the principle supply of latex rubber used throughout a lot of the 19th century. The rubber commerce was closely managed by enterprise pursuits however no legal guidelines expressly prohibited the export of seeds or vegetation. In 1876, Henry Wickham smuggled 70,000 Amazonian rubber tree seeds from Brazil and delivered them to Kew Gardens, England. Solely 2,400 of those germinated. Seedlings had been then despatched to India, British Ceylon (Sri Lanka), Dutch East Indies (Indonesia), Singapore, and British Malaya. Malaya (now Peninsular Malaysia) was later to change into the most important producer of rubber.[12]

Within the early 1900s, the Congo Free State in Africa was additionally a major supply of pure rubber latex, largely gathered by pressured labor.[citation needed] King Leopold II’s colonial state brutally enforced manufacturing quotas. Techniques to implement the rubber quotas included eradicating the palms of victims to show that they had been killed. Troopers typically got here again from raids with baskets filled with chopped-off palms. Villages that resisted had been razed to encourage higher compliance regionally. See Atrocities within the Congo Free State for extra info on the rubber commerce within the Congo Free State within the late 1800s and early 1900s.[citation needed]

In India, business cultivation was launched by British planters, though the experimental efforts to develop rubber on a business scale had been initiated as early as 1873 on the Calcutta Botanical Gardens. The primary business Hevea plantations had been established at Thattekadu in Kerala in 1902. In later years the plantation expanded to Karnataka, Tamil Nadu and the Andaman and Nicobar Islands of India. India right this moment is the world’s third largest producer and 4th largest shopper.[13]

In Singapore and Malaya, business manufacturing was closely promoted by Sir Henry Nicholas Ridley, who served as the primary Scientific Director of the Singapore Botanic Gardens from 1888 to 1911. He distributed rubber seeds to many planters and developed the primary method for tapping timber for latex with out inflicting critical hurt to the tree.[14] Due to his fervent promotion of this crop, he’s popularly remembered by the nickname “Mad Ridley”.[15]

Pre–World Battle II[edit]

Earlier than World Battle II vital makes use of included door and window profiles, hoses, belts, gaskets, matting, flooring and dampeners (antivibration mounts) for the automotive trade. The usage of rubber in automotive tires (initially stable reasonably than pneumatic) specifically consumed a major quantity of rubber. Gloves (medical, family and industrial) and toy balloons had been giant shoppers of rubber, though the kind of rubber used is concentrated latex. Vital tonnage of rubber was used as adhesives in lots of manufacturing industries and merchandise, though the 2 most noticeable had been the paper and the carpet industries. Rubber was generally used to make rubber bands and pencil erasers.

Rubber produced as a fiber, generally referred to as ‘elastic’, had vital worth to the textile trade due to its glorious elongation and restoration properties. For these functions, manufactured rubber fiber was made as both an extruded spherical fiber or rectangular fibers minimize into strips from extruded movie. Due to its low dye acceptance, really feel and look, the rubber fiber was both lined by yarn of one other fiber or instantly woven with different yarns into the material. Rubber yarns had been utilized in basis clothes. Whereas rubber continues to be utilized in textile manufacturing, its low tenacity limits its use in light-weight clothes as a result of latex lacks resistance to oxidizing brokers and is broken by growing old, daylight, oil and perspiration. The textile trade turned to neoprene (polymer of chloroprene), a sort of artificial rubber, in addition to one other extra generally used elastomer fiber, spandex (often known as elastane), due to their superiority to rubber in each energy and sturdiness.

Properties[edit]

Rubber displays distinctive bodily and chemical properties. Rubber’s stress–pressure habits displays the Mullins impact and the Payne impact and is commonly modeled as hyperelastic. Rubber pressure crystallizes. As a result of presence of weakened allylic C-H bonds in every repeat unit, pure rubber is inclined to vulcanisation in addition to being delicate to ozone cracking. The 2 most important solvents for rubber are turpentine and naphtha (petroleum). As a result of rubber doesn’t dissolve simply, the fabric is finely divided by shredding previous to its immersion. An ammonia resolution can be utilized to forestall the coagulation of uncooked latex. Rubber begins to soften at roughly 180 °C (356 °F).

Elasticity[edit]

On a microscopic scale, relaxed rubber is a disorganized cluster of erratically altering wrinkled chains. In stretched rubber, the chains are nearly linear. The restoring power is as a result of preponderance of wrinkled conformations over extra linear ones. For the quantitative therapy see superb chain, for extra examples see entropic power.

Cooling under the glass transition temperature permits native conformational modifications however a reordering is virtually not possible due to the bigger vitality barrier for the concerted motion of longer chains. “Frozen” rubber’s elasticity is low and pressure outcomes from small modifications of bond lengths and angles: this prompted the Challenger catastrophe, when the American Area Shuttle’s flattened o-rings didn’t calm down to fill a widening hole.[16] The glass transition is quick and reversible: the power resumes on heating.

The parallel chains of stretched rubber are inclined to crystallization. This takes a while as a result of turns of twisted chains have to maneuver out of the best way of the rising crystallites. Crystallization has occurred, for instance, when, after days, an inflated toy balloon is discovered withered at a comparatively giant remaining quantity. The place it’s touched, it shrinks as a result of the temperature of the hand is sufficient to soften the crystals.

Vulcanization of rubber creates di- and polysulfide bonds between chains, which limits the levels of freedom and ends in chains that tighten extra rapidly for a given pressure, thereby growing the elastic power fixed and making the rubber more durable and fewer extensible.

Malodour[edit]

Uncooked rubber storage depots and rubber processing can produce malodour that’s critical sufficient to change into a supply of complaints and protest to these dwelling within the neighborhood.[17] Microbial impurities originate through the processing of block rubber. These impurities break down throughout storage or thermal degradation and produce unstable natural compounds. Examination of those compounds utilizing gasoline chromatography/mass spectrometry (GC/MS) and gasoline chromatography (GC) signifies that they include sulphur, ammonia, alkenes, ketones, esters, hydrogen sulphide, nitrogen, and low molecular weight fatty acids (C2-C5).[18][19] When latex focus is produced from rubber, sulphuric acid is used for coagulation. This produces malodourous hydrogen sulphide.[19] The trade can mitigate these dangerous odours with scrubber methods.[19]

Chemical make-up[edit]

(1)trans-1,4-polyisoprene is called gutta-percha. (2)in natural rubber various chains are held together by weak Van Der Waal's interactions and has a coiled structure.so it can be stretched like a spring and exhibits elastic propeeties

Chemical construction of cis-polyisoprene, the principle constituent of pure rubber. Artificial cis-polyisoprene and pure cis-polyisoprene are derived from distinct precursors, isopentenyl pyrophosphate and isoprene.

Latex is the polymer cis-1,4-polyisoprene – with a molecular weight of 100,000 to 1,000,000 daltons. Sometimes, a small proportion (as much as 5% of dry mass) of different supplies, comparable to proteins, fatty acids, resins, and inorganic supplies (salts) are present in pure rubber. Polyisoprene will also be created synthetically, producing what is typically known as “artificial pure rubber”, however the artificial and pure routes are distinct.[6] Some pure rubber sources, comparable to gutta-percha, are composed of trans-1,4-polyisoprene, a structural isomer that has related properties. Pure rubber is an elastomer and a thermoplastic. As soon as the rubber is vulcanized, it’s a thermoset. Most rubber in on a regular basis use is vulcanized to some extent the place it shares properties of each; i.e., whether it is heated and cooled, it’s degraded however not destroyed. The ultimate properties of a rubber merchandise rely not simply on the polymer, but in addition on modifiers and fillers, comparable to carbon black, factice, whiting and others.

Biosynthesis[edit]

Rubber particles are shaped within the cytoplasm of specialised latex-producing cells referred to as laticifers inside rubber vegetation.[20] Rubber particles are surrounded by a single phospholipid membrane with hydrophobic tails pointed inward. The membrane permits biosynthetic proteins to be sequestered on the floor of the rising rubber particle, which permits new monomeric items to be added from exterior the biomembrane, however throughout the lacticifer. The rubber particle is an enzymatically energetic entity that comprises three layers of fabric, the rubber particle, a biomembrane and free monomeric items. The biomembrane is held tightly to the rubber core as a result of excessive unfavorable cost alongside the double bonds of the rubber polymer spine.[21] Free monomeric items and conjugated proteins make up the outer layer. The rubber precursor is isopentenyl pyrophosphate (an allylic compound), which elongates by Mg2+-dependent condensation by the motion of rubber transferase. The monomer provides to the pyrophosphate finish of the rising polymer.[citation needed] The method displaces the terminal high-energy pyrophosphate. The response produces a cis polymer. The initiation step is catalyzed by prenyltransferase, which converts three monomers of isopentenyl pyrophosphate into farnesyl pyrophosphate.[22] The farnesyl pyrophosphate can bind to rubber transferase to elongate a brand new rubber polymer.

The required isopentenyl pyrophosphate is obtained from the mevalonate pathway, which derives from acetyl-CoA within the cytosol. In vegetation, isoprene pyrophosphate will also be obtained from the 1-deox-D-xyulose-5-phosphate/2-C-methyl-D-erythritol-4-phosphate pathway inside plasmids.[23] The relative ratio of the farnesyl pyrophosphate initiator unit and isoprenyl pyrophosphate elongation monomer determines the speed of recent particle synthesis versus elongation of present particles. Although rubber is thought to be produced by just one enzyme, extracts of latex host quite a few small molecular weight proteins with unknown operate. The proteins presumably function cofactors, because the artificial fee decreases with full removing.[24]

Manufacturing[edit]

Rubber is usually cultivated in giant plantations. The picture exhibits a coconut shell utilized in accumulating latex, in plantations in Kerala, India.

Greater than 28 million tons of rubber had been produced in 2017, of which roughly 47% was pure. For the reason that bulk is artificial, which is derived from petroleum, the value of pure rubber is decided, to a big extent, by the prevailing world value of crude oil.[25][26][27] Asia was the principle supply of pure rubber, accounting for about 94% of output in 2005. The three largest producers, Thailand, Indonesia [28] and Malaysia, collectively account for round 72% of all pure rubber manufacturing. Pure rubber shouldn’t be cultivated extensively in its native continent of South America as a result of existence of South American leaf blight, and different pure predators.

Cultivation[edit]

Rubber latex is extracted from rubber timber. The financial life interval of rubber timber in plantations is round 32 years, as much as 7 years of immature part and about 25 years of productive part.

The soil requirement is well-drained, weathered soil consisting of laterite, lateritic varieties, sedimentary varieties, nonlateritic pink or alluvial soils.

The weather conditions for optimum development of rubber timber are:

  • Rainfall of round 250 centimetres (98 in) evenly distributed with none marked dry season and with a minimum of 100 wet days per yr
  • Temperature vary of about 20 to 34 °C (68 to 93 °F), with a month-to-month imply of 25 to 28 °C (77 to 82 °F)
  • Atmospheric humidity of round 80%
  • About 2,000 hours sunshine per yr on the fee of six hours per day all year long
  • Absence of robust winds

Many high-yielding clones have been developed for business planting. These clones yield greater than 2,000 kilograms per hectare (1,800 lb/acre) of dry rubber per yr, underneath superb situations.

Assortment[edit]

A girl in Sri Lanka harvesting rubber, c. 1920

In locations comparable to Kerala and Sri Lanka, the place coconuts are in abundance, the half shell of coconut was used because the latex assortment container. Glazed pottery or aluminium or plastic cups grew to become extra widespread in Kerala and different international locations. The cups are supported by a wire that encircles the tree. This wire incorporates a spring so it will probably stretch because the tree grows. The latex is led into the cup by a galvanised “spout” knocked into the bark. Tapping usually takes place early within the morning, when the inner strain of the tree is highest. tapper can faucet a tree each 20 seconds on a regular half-spiral system, and a standard day by day “activity” measurement is between 450 and 650 timber. Bushes are normally tapped on alternate or third days, though many variations in timing, size and variety of cuts are used. “Tappers would make a slash within the bark with a small hatchet. These slanting cuts allowed latex to movement from ducts situated on the outside or the inside layer of bark (cambium) of the tree. For the reason that cambium controls the expansion of the tree, development stops whether it is minimize. Thus, rubber tapping demanded accuracy, in order that the incisions wouldn’t be too many given the scale of the tree, or too deep, which might stunt its development or kill it.”[29]

It’s regular to faucet a pannel a minimum of twice, generally thrice, through the tree’s life. The financial lifetime of the tree depends upon how effectively the tapping is carried out, because the vital issue is bark consumption. A normal in Malaysia for alternate day by day tapping is 25 cm (vertical) bark consumption per yr. The latex-containing tubes within the bark ascend in a spiral to the suitable. For that reason, tapping cuts normally ascend to the left to chop extra tubes. The timber drip latex for about 4 hours, stopping as latex coagulates naturally on the tapping minimize, thus blocking the latex tubes within the bark. Tappers normally relaxation and have a meal after ending their tapping work, then begin accumulating the liquid “subject latex” at about noon.

Discipline coagula[edit]

Smallholder’s lump at a remilling manufacturing facility

The 4 varieties of subject coagula are “cuplump”, “treelace”, “smallholders’ lump” and “earth scrap”. Every has considerably completely different properties.[30] Some timber proceed to drip after the gathering resulting in a small quantity of “cup lump” that’s collected on the subsequent tapping. The latex that coagulates on the minimize can also be collected as “tree lace”. Tree lace and cup lump collectively account for 10%–20% of the dry rubber produced. Latex that drips onto the bottom, “earth scrap”, can also be collected periodically for processing of low-grade product.

Cup lump[edit]

Cup lump rubber coagula in a Myanmar highway stall.

Cup lump is the coagulated materials discovered within the assortment cup when the tapper subsequent visits the tree to faucet it once more. It arises from latex clinging to the partitions of the cup after the latex was final poured into the bucket, and from late-dripping latex exuded earlier than the latex-carrying vessels of the tree change into blocked. It’s of upper purity and of higher worth than the opposite three varieties.

Tree lace[edit]

Tree lace is the coagulum strip that the tapper peels off the earlier minimize earlier than making a brand new minimize. It normally has increased copper and manganese contents than cup lump. Each copper and manganese are pro-oxidants and may harm the bodily properties of the dry rubber.

Smallholders’ lump[edit]

Smallholders’ lump is produced by smallholders, who acquire rubber from timber removed from the closest manufacturing facility. Many Indonesian smallholders, who farm paddies in distant areas, faucet dispersed timber on their technique to work within the paddy fields and acquire the latex (or the coagulated latex) on their method dwelling. As it’s typically not possible to protect the latex sufficiently to get it to a manufacturing facility that processes latex in time for it for use to make top quality merchandise, and because the latex would anyway have coagulated by the point it reached the manufacturing facility, the smallholder will coagulate it by any means obtainable, in any container obtainable. Some smallholders use small containers, buckets and so forth., however typically the latex is coagulated in holes within the floor, that are normally lined with plastic sheeting. Acidic supplies and fermented fruit juices are used to coagulate the latex — a type of assisted organic coagulation. Little care is taken to exclude twigs, leaves, and even bark from the lumps which can be shaped, which can additionally embrace tree lace.

Earth scrap[edit]

Earth scrap is materials that gathers across the base of the tree. It arises from latex overflowing from the minimize and operating down the bark, from rain flooding a group cup containing latex, and from spillage from tappers’ buckets throughout assortment. It comprises soil and different contaminants, and has variable rubber content material, relying on the quantity of contaminants. Earth scrap is collected by subject employees two or thrice a yr and could also be cleaned in a scrap-washer to recuperate the rubber, or offered to a contractor who cleans it and recovers the rubber. It’s of low high quality.

Processing[edit]

Eradicating coagulum from coagulating troughs.

Latex coagulates within the cups, if saved for lengthy and should be collected earlier than this occurs. The collected latex, “subject latex”, is transferred into coagulation tanks for the preparation of dry rubber or transferred into air-tight containers with sieving for ammoniation. Ammoniation preserves the latex in a colloidal state for longer intervals of time. Latex is usually processed into both latex focus for manufacture of dipped items or coagulated underneath managed, clear situations utilizing formic acid. The coagulated latex can then be processed into the higher-grade, technically specified block rubbers comparable to SVR 3L or SVR CV or used to supply Ribbed Smoke Sheet grades. Naturally coagulated rubber (cup lump) is used within the manufacture of TSR10 and TSR20 grade rubbers. Processing for these grades is a measurement discount and cleansing course of to take away contamination and put together the fabric for the ultimate stage of drying.[31]

The dried materials is then baled and palletized for storage and cargo.

Vulcanized rubber[edit]

Torn latex rubber dry swimsuit wrist seal

Pure rubber is commonly vulcanized – a course of by which the rubber is heated and sulfur, peroxide or bisphenol are added to enhance resistance and elasticity and to forestall it from perishing. Carbon black is commonly used as an additive to rubber to enhance its energy, particularly in automobile tires, which account for about 70% (~9 million tons) of carbon black manufacturing.

Transportation[edit]

Pure rubber latex is shipped from factories in Southeast Asia, South America, and West and Central Africa to locations around the globe. As the price of pure rubber has risen considerably and rubber merchandise are dense, the delivery strategies providing the bottom price per unit weight are most popular. Relying on vacation spot, warehouse availability, and transportation situations, some strategies are most popular by sure consumers. In worldwide commerce, latex rubber is usually shipped in 20-foot ocean containers. Contained in the container, smaller containers are used to retailer the latex.[32]

Uncured rubber is used for cements;[33] for adhesive, insulating, and friction tapes; and for crepe rubber utilized in insulating blankets and footwear. Vulcanized rubber has many extra purposes. Resistance to abrasion makes softer sorts of rubber worthwhile for the treads of car tires and conveyor belts, and makes laborious rubber worthwhile for pump housings and piping used within the dealing with of abrasive sludge.

The flexibleness of rubber is interesting in hoses, tires and rollers for gadgets starting from home garments wringers to printing presses; its elasticity makes it appropriate for numerous sorts of shock absorbers and for specialised equipment mountings designed to cut back vibration. Its relative gasoline impermeability makes it helpful within the manufacture of articles comparable to air hoses, balloons, balls and cushions. The resistance of rubber to water and to the motion of most fluid chemical substances has led to its use in rainwear, diving gear, and chemical and medicinal tubing, and as a lining for storage tanks, processing tools and railroad tank automobiles. Due to their electrical resistance, mushy rubber items are used as insulation and for protecting gloves, footwear and blankets; laborious rubber is used for articles comparable to phone housings, elements for radio units, meters and different electrical devices. The coefficient of friction of rubber, which is excessive on dry surfaces and low on moist surfaces, results in its use for power-transmission belting and for water-lubricated bearings in deep-well pumps. Indian rubber balls or lacrosse balls are manufactured from rubber.

Round 25 million tonnes of rubber are produced annually, of which 30 p.c is pure.[34] The rest is artificial rubber derived from petrochemical sources. The highest finish of latex manufacturing ends in latex merchandise comparable to surgeons’ gloves, balloons and different comparatively high-value merchandise. The mid-range which comes from the technically specified pure rubber supplies finally ends up largely in tires but in addition in conveyor belts, marine merchandise, windshield wipers and miscellaneous items. Pure rubber gives good elasticity, whereas artificial supplies have a tendency to supply higher resistance to environmental components comparable to oils, temperature, chemical substances and ultraviolet mild. “Cured rubber” is rubber that has been compounded and subjected to the vulcanisation course of to create cross-links throughout the rubber matrix.

Allergic reactions[edit]

Some folks have a critical latex allergy, and publicity to pure latex rubber merchandise comparable to latex gloves may cause anaphylactic shock. The antigenic proteins present in Hevea latex could also be intentionally lowered (although not eradicated)[35] via processing.

Latex from non-Hevea sources, comparable to Guayule, can be utilized with out allergic response by individuals with an allergy to Hevea latex.[36]

Some allergic reactions are to not the latex itself, however from residues of chemical substances used to speed up the cross-linking course of. Though this can be confused with an allergy to latex, it’s distinct from it, usually taking the type of Kind IV hypersensitivity within the presence of traces of particular processing chemical substances.[35][37]

Microbial degradation[edit]

Pure rubber is inclined to degradation by a variety of micro organism.[38][39][40][41][42][43][44][45]
The micro organism Streptomyces coelicolor, Pseudomonas citronellolis, and Nocardia spp. are able to degrading vulcanized pure rubber.[46]

See additionally[edit]

References[edit]

Citations[edit]

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  2. ^ Heim, Susanne (2002). Autarkie und Ostexpansion: Pflanzenzucht und Agrarforschung im Nationalsozialismus. Wallstein Verlag. ISBN 978-3-89244-496-1.
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  4. ^ Smith, James P., Jr/ (2006). “Crops & Civilization : An Introduction to theInterrelationships of Crops and Folks. Part 8.4, Latex Crops”. Humboldt State College Botanical Research Open Instructional Sources and Knowledge, Humboldt State College Digital Commons. pp. 137–141. Retrieved Eight June 2019.
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  21. ^ Paterson-Jones, J.C.; Gilliland, M.G.; Van Staden, J. (June 1990). “The Biosynthesis of Pure Rubber”. Journal of Plant Physiology. 136 (3): 257–263. doi:10.1016/S0176-1617(11)80047-7. ISSN 0176-1617.
  22. ^ 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. doi:10.1016/j.phytochem.2008.07.011. PMID 18799172.
  23. ^ Casey, P.J.; Seabra, M.C. (1996). “Protein Prenyltransferases”. Journal of Organic Chemistry. 271 (10): 5289–5292. doi:10.1074/jbc.271.10.5289. PMID 8621375.
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Sources[edit]

Additional studying[edit]

  • Dean, Warren. (1997) Brazil and the Battle for Rubber: A Examine in Environmental Historical past. Cambridge College Press.
  • Grandin, Greg. Fordlandia: The Rise and Fall of Henry Ford’s Forgotten Jungle Metropolis. Picador Press 2010. ISBN 978-0312429621
  • Weinstein, Barbara (1983) The Amazon Rubber Increase 1850-1920. Stanford College Press.

Exterior hyperlinks[edit]

  • Media associated to Rubber at Wikimedia Commons
  • The dictionary definition of pure rubber at Wiktionary


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