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(Palaquium) 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. Chemically, gutta-percha is
a polyterpene, a polymer of isoprene, or polyisoprene, specifically (trans-1,4-polyisoprene).
Heavy use of gutta-percha during the second half of the nineteenth century, particularly as
insulation for underwater telegraph cables, led to unsustainable harvesting and a collapse of
the supply.
The word 'gutta-percha' comes from the plant's name in Malay, getah perca, which
translates as "percha sap".
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Gutta-percha was obtained from a variety of guttiferous trees throughout the Pacific
Rim although different varieties produce materials of differing quality. The differencesgenerally reflect the quantity of resin in the product with that from Pahang having the
lowest resin content. Balata has one of the highest resin contents and was obtained
from trees in the tropical regions of South America.
There is much confusion in the literature, and amongst collectors, as to “what gutta-
percha is”. In practical terms, and when addressing collectors’ items, the material is
probably the whole residue from the latex, dried after collection from whichever tree
was its source. This material tends to range from dark yellow through red to black. It
is possible that it has undergone some degree of purification but, given the variations
in initial composition, it would be extremely difficult to confirm this, even by detailed
chemical analysis.
In the same way that commercially available natural rubber is some 95% cis
polyisoprene, the crude gutta- percha was often 30% to 50% trans polyisoprene.
That is it has the same chemical “building block” as natural rubber (C5H8)n but with
a different spacial configuration. Isolation of the pure trans polyisoprene gives a
white/very pale cream “cheesy” material which looks and feels not unlike a block of
high density polythene (m.p. about 135°C) or polypropylene (m.p. 168°C). The hard
gutta-percha softens at relativel y low temperatures (>71°C) and could then easily be
mould ed or extruded (the screw extruder was invented in 1845). At slightly lower
temperatures, around 60°C, it can easily be cut whilst at room temperature it reverts
to a hard material.
The trees are 5 –30 metres tall and up to 1 metre in trunk diameter. The leaves
are evergreen, alternate or spirally arranged, simple, entire, 8 –25 cm long, and glossy green
above, often yellow or glaucous below. The flowers are produced in small clusters along the
stems, each flower with a white corolla with 4 –7 (mostly 6) acute lobes. The fruit is an ovoid
3 –7 cm berry, containing 1 –4 seeds; in many species the fruit is edible.In Australia, gutta-percha is a common name specifically used for the tree Excoecaria
parvifolia, which yields an aromatic, heavy, dark brown timber. It is also called "northern
birch". This particular species is not related to the palaquims
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Uses
Electronics
Gutta-percha latex is biologically inert, resilient, and is a good electrical insulator with a
high dielectric strength. The wood of many species is also valuable.
Western inventors discovered the properties of gutta-percha latex in 1842, although the localpopulation in its Malayan habitat had used it for a variety of applications for centuries.
Allowing this fluid to evaporate and coagulate in the sun produced a latex which could be
made flexible again with hot water, but which did not become brittle, unlike rubber prior to the
discovery of vulcanization.
By 1845, telegraph wires insulated with gutta-percha were being manufactured in the United
Kingdom. It served as the insulating material for some of the earliest undersea telegraph
cables, including the first transatlantic telegraph cable. Gutta-percha was particularly suitable
for this purpose, as it was not attacked by marine plants or animals, a problem which had
disabled previous undersea cables. The material was a major constituent of Chatterton's
compound used as an insulating sealant for telegraph and other electrical cables.Polyethylene'ssuperior insulative property has displaced it.The same bioinertness property that made it
suitable for marine cables also means it does not readily react within the human body, and
consequently it is used for a variety of surgical devices and for dental applications
during root canal therapy. It is the predominant material used to obturate, or fill the empty
space inside the root of a tooth after it has undergoneendodontic therapy. Its physical and
chemical properties, including but not limited to itsinertness and biocompatibility, melting
point, ductility and malleability, afford it an important role in the field of endodontics.
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This material, found just a few years earlier in Malaya, was presented to Cyrus Field by
Samuel Canning who would come to be a member of the first transatlantic cable expedition.
From Samuel Canning, Mr. Field learned of the difficulties of keeping the copper wires in the
cable insulated because of the conductive medium from the ocean that surrounded the wire.Gutta-percha seemed to have the required properties for this task.
Gutta-percha was produced by evaporating the milky fluid of the guttapercha tree and
coagulating the latex from which an inelastic firm insulator resulted. This material softened
in hot water. It had a distinct advantage over India rubber that had been used in earlier
cables because, on cooling, it became hard without becoming brittle. It was ideally suited for
underwater use where the cold and pressure improved its insulating qualities. Submersion
also kept the cable away from sunlight which had a deteriorating effect on the cable. The
crossing of the Atlantic Ocean by cable was viewed by the scientists involved in the gutta-
percha work as the ultimate test of the material. Locally made items of this material were
brought to Europe from the Malay Peninsula and specimens were exhibited at the RoyalSociety of Arts in London in 1843. It was subsequently imported and used for various
applications, including jewellery making. The discovery of a form of rubber called gutta-
percha in 1843 led to the manufacture of a suitable insulation by 1847. In 1845, the S. W.
Silver & Co. of Stratford, East London, invented a means of extruding gutta-percha to cover
wire (see picture below). Gutta-percha was the best cable insulation available and it was
used to insulate the telegraph lines along the Great Western Railroad in 1843. The lines
consisted of five copper conductor wires, covered with gutta-percha and supported in
wooden blocks.
The same bioinertness property that made it suitable for marine cables also means it does
not readily react within the human body, and consequently it is used for a variety of surgical
devices and for dental applications during root canal therapy. It is the predominant material
used to obturate, or fill the empty space inside the root of a tooth after it has
undergoneendodontic therapy. Its physical and chemical properties, including but not limited
to itsinertness and biocompatibility, melting point, ductility and malleability, afford it an
important role in the field of endodontics.
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and are different from
Parthenium argentatum, commonly known as the Guayule , is a flowering shrub in
theaster 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 theMexican states of Zacatecas, Coahuila, Chihuahua, San Luis Potosí, Nuevo Leon,
and Tamaulipas.[3][4] The plant can be used as an alternate source of latex that is
also hypoallergenic, unlike the normal Hevea rubber. In pre-Columbian times, the guayule
was a secondary source of latex for rubber, the principal source being the Castilla
elastica tree. The name "guayule" derives from the Nahuatl word ulli/olli, "rubber".
Parthenium argentatum
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Genus: Parthenium
Species: P. argentatum
Binomial name
Parthenium argentatum
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Range and habitat
For sustainable production, guayule grows well in arid and semi arid areas of the southwestern United
States, North Central Mexico and regions with similar climates around the world. Because the guayule
plant produces terpene resins, which are natural pesticides, it is resistant to many pests and
diseases. Herbicides are primarily necessary for stand establishment.
Commercial rubber latex source
In the 1920s, the plant saw a brief and intense amount of agricultural research when the
Intercontinental Rubber Company in California produced 1400 tons of rubber after leaf blight
decimated the Brazilian rubber industry. Guayule would again become a replacement for Hevea tree-
produced latex during World War II when Japan cut off America's Malaysianlatex resources. The war
ended before large-scale farming of the guayule plant began, and the project was scrapped, as it was
cheaper to import tree-derived latex than to crush the shrubs for a smaller amount of latex.
Recently, the guayule plant has seen a small but growing resurgence in research and
agriculture due to its hypoallergenic properties. While Hevea -derived rubber
contains proteins that can cause severe allergic reactions in a few people, guayule does not.
With the AIDScrisis of the 1980s, the surge in rubber glove usage revealed how many
people were allergic to latex (about 10% of health care workers, according to OSHA), and
thereby created a niche market for guayule. There are synthetic alternatives for medical
device products, but they are not as stretchable as natural rubber. Guayule performs
like Hevea but contains none of the proteins that cause latex allergies.
Hypoallergenic properties
Selection of high-yielding guayule is complicated by its breeding system, which is
primarily apomixis (asexual cloning via gametes). However, the breeding system is
somewhat variable and considerable genetic variation exists within wild populations.
Selection of high-yielding lines has been successful.[5]
Medical devices
The company leading the commercialization of guayule as an industrial crop is Yulex
Corporation, founded by Daniel R. Swiger. Yulex Corporation manufactures and produces
guayule rubber for medical devices and specialty consumer products that are safe for peoplewho have latex allergy. Yulex Corporation has cultivated proprietary, high-yielding lines of
guayule with agricultural operations concentrated in Arizona as well as some operations
in Queensland, Australia. Yulex rubber is marketed as a cost-effective, clinically proven
solution to the serious health risks posed by Hevea -derived latex products.
In April 2008, the U.S. Food and Drug Administration cleared for marketing the first device
made from guayule latex, the Yulex Patient Examination Glove, which was submitted by
Yulex Corporation.
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Biofuel
Guayule's viability as a potential biofuel has been enhanced recently in light of commentary
from a variety of experts, including Lester R. Brown of the Earth Policy Institute, stating that
"[food based] biofuels pit the 800 million people with cars against the 800 million people with
hunger problems," meaning that biofuels derived from food crops (like maize) raise worldfood prices. Guayule can be an economically viable biofuel crop that does not increase the
world's hunger problem. Guayule has another benefit over food crops as biofuel - it can be
grown in areas where food crops would fail.
Hevea is a genus of flowering plants in the spurge family, Euphorbiaceous. It is also one of
many names used commercially for the wood of the most economically important species H.brasiliensis.
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Malpighiales
Family: Euphorbiaceae
Subfamily: Crotonoideae
Tribe: Micrandreae
Subtribe: Heveinae
Genus: Hevea
Aubl.
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, 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 It is of major economic importance because its sap-like extract
(known aslatex) is the primary source of natural rubber .
Rubber tree plantation
In the wild, the tree can reach a height of up to 100 feet (30 m). The white or yellow latex occurs in
latex vessels in the bark, mostly outside the phloem. These vessels spiral up the tree in a right-
handed helixwhich forms an angle of about 30 degrees with the horizontal, and can grow as high as
45 ft.
In plantations, the trees are kept smaller, up to 78 feet (24 m) tall, so as to use most of the
availablecarbon dioxide for latex production.
The tree requires a climate with heavy rainfall and without frost. If frost does occur, the results can be
disastrous for production. One frost can cause the rubber from an entire plantation to become brittle
and break once it has been refined.
Harvest of latex
Once the trees are 5 –6 years old, harvesting can begin: incisions are made orthogonally to the latex
vessels, just deep enough to tap the vessels without harming the tree's growth, and the sap iscollected in small buckets. This process is known as rubber tapping. Older trees yield more latex.
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