Gutta-percha refers both to trees of the genus Palaquium in the family Sapotaceae and the rigid, naturally biologically inert, resilient, electrically nonconductive, thermoplasticlatex produced from the sap of these trees, particularly from Palaquium gutta. It is a polymer of isoprene which forms a rubber-like elastomer. The word gutta-percha comes from the plant's name in Malay: getah translates as 'latex'. Percha or perca is an older name for Sumatra.
Description
Palaquium gutta trees are tall and up to in trunk diameter. The leaves are evergreen, alternate or spirally arranged, simple, entire, long, glossy green above, and often yellow or glaucous below. The flowers are produced in small clusters along the stems, each flower with a white corolla with four to seven acute lobes. The fruit is an ovoid berry, containing one to four seeds; in many species, the fruit is edible. In Australia, gutta-percha is a common name specifically used for the euphorbiaceous tree Excoecaria parvifolia, which yields an aromatic, heavy, dark-brown timber.
Chemistry
Chemically, gutta-percha is a polyterpene, a polymer of isoprene, or polyisoprene, specifically. The cis structure of polyisoprene is the common latex elastomer. While latex rubbers are amorphous in molecular structure, gutta-percha crystallizes, leading to a more rigid material.
Uses
Historic
Scientifically classified in 1843, it was found to be a useful natural thermoplastic. In 1851, of gutta-percha was imported into Britain. During the second half of the 19th century, gutta-percha was used for many domestic and industrial purposes, and it became a household word. In particular, it was needed as insulation for underwater telegraph cables, which, according to author John Tully, led to unsustainable harvesting and collapse of supply. According to Harvey Wickes Felter and John Uri Lloyd's Endodontology:
Electrical
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 through samples sent to England by William Montgomerie, although the people of its Malayan habitat had used it for many 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 UK. It served as the insulating material for early undersea telegraph cables, including the first transatlantic telegraph cable. The material was a major constituent of Chatterton's compound used as an insulating sealant for telegraph and other electrical cables. The dielectric constant of dried gutta-percha ranges from 2.56 to 3.01. Resistivity of dried gutta-percha ranges from 25 x 1014 to 370 x 1014 ohm-cm. Since about 1940, polyethylene has supplanted gutta-percha as an electrical insulator.
Other
In the mid-19th century, gutta-percha was used to make furniture, notably by the Gutta Percha Company, established in 1847. Several of these ornate, revival-style pieces were shown at the 1851 Great Exhibition in Hyde Park, London. The company also made a range of utensils. The "guttie" golf ball revolutionized the game. Gutta-percha was used to make "mourning" jewelry, because it was dark in color and could be easily molded into beads or other shapes. Pistol hand grips and rifle shoulder pads were also made from gutta-percha, since it was hard and durable, though it fell into disuse when synthetic plastics such as Bakelite 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 in his attack on Senator Charles Sumner.
Gutta-percha remained an industrial staple well into the 20th century, when it was gradually replaced with superior synthetic materials such as Bakelite, though a similar and cheaper natural material called balatá was often used in gutta-percha's place. The two materials are almost identical, and balatá is often called gutta-balatá.
Flotsam
Blocks of flotsam, about the size of a chopping-board, bearing the name "Tjipetir", were washed up on the beaches of northern Europe for some time through 2013 and 2014. They are believed to be blocks of gutta-percha from the Japanese liner Miyazaki Maru, which was sunk west of the Isles of Scilly in 1917.
