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Gutta-percha is a tree of the genusPalaquium in the familySapotaceae, which is primarily used to create a high-qualitylatex of the same name. The material is rigid, naturally biologicallyinert, resilient, electricallynonconductive, andthermoplastic, most commonly sourced fromPalaquium gutta; it is a polymer ofisoprene which forms a rubber-likeelastomer.
The word "gutta-percha" comes from the plant's name inMalay:getah translates as 'sticky gum' andpertja (perca) is the name of a less-sought-after gutta tree. The western term therefore is likely a derivative amalgamation of the original native names.[1]
Palaquium gutta trees are 5–30 metres (20–100 ft) tall and up to 1 m (3 ft) in trunk diameter. The leaves areevergreen, alternate or spirally arranged, simple, entire, 8–25 cm (3–10 in) long, glossy green above, and often yellow orglaucous below. The flowers are produced in small clusters along the stems, each flower with a whitecorolla with four to seven (mostly six) acute lobes. The fruit is an ovoid 3–7 cm (1–3 in) berry, containing one to four seeds; in many species, the fruit is edible.
In Australia, gutta-percha is a common name specifically used for theeuphorbiaceous treeExcoecaria parvifolia, which yields an aromatic, heavy, dark-brown timber.
Chemically, gutta-percha is apolyterpene, apolymer ofisoprene, orpolyisoprene, specifically (trans-1,4-polyisoprene).[3] Thecis structure of polyisoprene is the commonlatexelastomer.[3] While latex rubbers areamorphous in molecular structure, gutta-percha (the trans structure)crystallizes, leading to a more rigid material. It exists in alpha and beta forms, with the alpha form being brittle at room temperature.[4]
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Long before gutta-percha was introduced into the Western world, it was used in a less-processed form by the natives of the Malaysian archipelago for making knife handles, walking sticks, and other purposes. The first European to study this material wasJohn Tradescant, who collected it in the far east in 1656. He named this material "Mazer wood".William Montgomerie, a medical officer in imperial service, introduced gutta-percha into practical use in the West. He was the first to appreciate the potential of this material in medicine, and he was awarded the gold medal by the Royal Society of Arts, London in 1843.[5]
Scientifically classified in 1843, it was found to be a useful naturalthermoplastic. In 1851, 30,000 long cwt (1,500 t) of gutta-percha was imported into Britain.[6] During the second half of the 19th century, gutta-percha was used for many domestic and industrial purposes,[7] and it became a household word. Gutta-percha was particularly important for the manufacture ofunderwater telegraph cables.[6] Compared to rubber, it does not degrade in seawater, is not damaged by marine life, and maintains goodelectrical insulation.[8] These properties, along with its mouldability and flexibility made it ideal for the purpose, with no other material to match it in the 19th century.[9] The use in electrical cables generated a huge demand which led tounsustainable harvesting and collapse of supply.[10]
Gutta-percha latex is biologicallyinert, resilient, and is a good electrical insulator with a highdielectric strength.[8]
Michael Faraday discovered its value as an insulator soon after the introduction of the material to Britain in 1843. 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, unlikerubber prior to the discovery ofvulcanization.[11]
By 1845, telegraph wires insulated with gutta-percha were being manufactured in the UK. It served as the insulating material for early undersea telegraph cables, including the firsttransatlantic telegraph cable.[12] The material was a major constituent ofChatterton's compound used as aninsulating sealant for telegraph and other electrical cables.[13]
The dielectric constant of dried gutta-percha ranges from 2.56 to 3.01. Resistivity of dried gutta-percha ranges from25×1014 to370×1014 Ω⋅cm.[14]
Since about 1940,polyethylene has supplanted gutta-percha as an electrical insulator.[15]
In the mid-19th century, gutta-percha was used to make furniture, notably by theGutta Percha Company, established in 1847.[6] Several of these ornate, revival-style pieces were shown at the 1851Great Exhibition in Hyde Park, London. The company also made a range of utensils.[16]
The "guttie" golf ball (which had a solid gutta-percha core) revolutionized the game.[17] Gutta-percha was used to make "mourning" jewelry, because it was dark in color and could be easily molded into beads or other shapes.[18] Pistol hand grips[19] and rifle shoulder pads were also made from gutta-percha, since it was hard and durable, though it fell into disuse when syntheticplastics such asBakelite became available.
Gutta-percha was used in canes and walking sticks. In 1856, United States RepresentativePreston Brooks used a cane made of gutta-percha as a weapon inhis attack on SenatorCharles Sumner.[20]
In the 1860s, gutta-percha was used to reinforce the soles of football players' boots before it was banned byThe Football Association in the first codified set of rules in 1863.[21]
Gutta-percha was briefly used inbookbinding until the advent ofvulcanization.[22]
Gutta-percha is used as aresist in silk painting,[23][24] including some newer forms ofbatik.
The same bioinertness that made it suitable for marine cables also means it does not readily react within the human body. It is used in a variety of surgical devices and duringroot canal therapy. It is the predominant material used toobturate, or fill, the empty space inside the root of a tooth after it has undergoneendodontic therapy. Its physical and chemical properties, including its inertness andbiocompatibility,melting point,[25]ductility, andmalleability, make it important inendodontics,[5] e.g., as gutta-percha points.Zinc oxide is added to reduce brittleness and improve plasticity.Barium sulfate is added to provideradiopacity so that its presence and location can be verified in dental X-ray images.
Gutta-percha remained an industrial staple well into the 20th century, when it was gradually replaced with superior synthetic materials, such asBakelite.
A similar and cheaper natural material calledbalatá was often used in gutta-percha's place. The two materials are almost identical, andbalatáis often calledgutta-balatá.[citation needed]
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