Gutta-percha

Gutta-percha (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).

The word 'gutta-percha' comes from the plant's name in Malay, getah perca, which translates as "percha sap".

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

Gutta-percha latex is biologically inert, resilient, and is a good electrical insulator due to 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 local population 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 unvulcanized rubber already in use.

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 adhesive sealant for telegraph and other electrical cables. Polyethylene is now used as a cable insulator owing to its superior electrical properties.

In the mid-19th century, gutta-percha was also used to make furniture, notably by the Gutta-Percha Company (established in 1847). Several of these highly ornate, revival-style pieces were shown at the 1851 Great Exhibition in Hyde Park, London. Molded furniture forms, emulating carved wood, were attacked by proponents of the design reform movement, who advocated truth to materials. It was also 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. Gutta-percha found use in canes and walking sticks as well; in 1856, Representative Preston Brooks used a cane made of gutta-percha as a weapon in his infamous attack on Senator Charles Sumner.

The material was quickly adopted for numerous other applications. The "guttie" golf ball (which had a solid gutta-percha core) revolutionized the game. Gutta-percha remained an industrial staple well into the 20th century, when it was gradually replaced with superior (generally synthetic) materials, though a similar and cheaper natural material called balatá is often used in gutta-percha's place. The two materials are almost identical, and balatá is often called gutta-balatá.

Dentistry

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 undergone endodontic therapy. Its physical and chemical properties, including but not limited to its inertness and biocompatibility, melting point, ductility and malleability, afford it an important role in the field of endodontics.

See also

• Natural rubber
• Polyisoprene

References and external links

• Germplasm Resources Information Network: Palaquium
• Gutta-percha on the Transatlantic cable site
• The Gutta Percha Company on the History of the Atlantic Cable site