gutta-percha

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gutta-percha

(gŭt`ə-pûr`chə), natural latexlatex,
emulsion of a polymer (e.g., rubber) in water (see colloid). Natural latexes are produced by a number of plants, are usually white in color, and often contain, in addition to rubber, various gums, oils, and waxes.
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 obtained from Palaquium gutta and several other evergreen trees of East Asia. The latex, collected by felling or girdling the tree, is allowed to coagulate and is then washed, purified, and molded into bricks for shipping. Like caoutchouccaoutchouc
, natural rubber obtained as a latex from various tropical plants, e.g., the Pará rubber tree. It is much more elastic than balata or gutta-percha. It is the most familiar and widely used of the natural rubbers.
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, gutta-percha is a polyterpene, i.e., a polymer of isoprene (see rubberrubber,
any solid substance that upon vulcanization becomes elastic; the term includes natural rubber (caoutchouc) and synthetic rubber. The term elastomer is sometimes used to designate synthetic rubber only and is sometimes extended to include caoutchouc as well.
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), but, unlike caoutchouc, it is not very elastic; the reason for the difference is that the polymer molecules in gutta-percha have a trans structure, whereas those of caoutchouc have a cis structure (see isomerisomer
, in chemistry, one of two or more compounds having the same molecular formula but different structures (arrangements of atoms in the molecule). Isomerism is the occurrence of such compounds. Isomerism was first recognized by J. J. Berzelius in 1827.
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). Gutta-percha is an excellent nonconductor and is often employed in insulating marine and underground cables. It is also used for golf-ball coverings, surgical appliances, and adhesives.

Gutta-Percha

 

a metabolic product of gutta-percha-yielding plants. The main constituent of gutta-percha (up to 90 percent)—high-molecular-weight trans-polyisoprene (gut-ta) with the empirical formula (C5H8)n—is an isomer of cis-polyisoprene, a hydrocarbon of natural rubber. The average molecular weight of gutta is about 50,000. Besides gutta, industrial gutta-percha contains resins, proteins, moisture, and other substances.

At room temperature, industrial gutta-percha is a solid skinlike substance that is white to yellowish-brown in color, with a density of 0.945–0.955 g/cm3, and an index of refraction nD20 = 1.523. Gutta-percha is resistant to the action of acids, including hydrochloric and hydrofluoric acids. When heated (50°-100° C), gutta-percha softens and becomes plastic and soluble in aromatic and chlorinated hydrocarbons. Its most valuable properties are waterproofness (moisture absorption in two years does not exceed 0.2 percent) and high electric insulation properties (dielectric permeability, 2.6; specific volume electric resistance 1012 ohm․m [1014 ohm •cm]). Like natural rubber, gutta-percha can be vulcanized with sulfur. The tensile strength of vulcanized gutta-percha is 17–30 meganewtons/m2 (170–300 kilograms-force/cm2) and the relative elongation, 500–550 percent.

Gutta-percha is used mainly as insulation for underwater cables and in the manufacture of acid-resistant and adhesive substances. The use of gutta-percha is declining because it is being replaced by synthetic trans-polyisoprene, trans-polychloroprene (so-called synthetic gutta-percha), and some other synthetic polymers.

REFERENCES

Voinovskii, A. B. Guttapercha. Moscow-Leningrad, 1951.
Spravochnik rezinshchika. Materialy rezinovogo proizvodstva. Moscow, 1971. Page 251.

gutta-percha

[¦gəd·ə′pər·chə]
(materials)
A leathery, thermoplastic substance consisting of gutta hydrocarbon with some resin obtained from the latex of certain Malaysian sapotaceous trees; used as insulation for submarine cables, and in golf balls and other products.

gutta-percha

1. any of several tropical trees of the sapotaceous genera Palaquium and Payena, esp Palaquium gutta
2. a whitish rubber substance derived from the coagulated milky latex of any of these trees: used in electrical insulation and dentistry