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In polymer chemistry and materials science, a resin is a solid or highly Viscosity substance of plant or synthetic origin that is typically convertible into . Resins are usually mixtures of . This article focuses mainly on naturally occurring resins.
Plants secrete resins for their protective benefits in response to injury. Resins protect plants from insects and pathogens. Resins confound a wide range of herbivores, insects, and pathogens, while the volatile natural phenol may attract benefactors such as or predators of the herbivores that attack the plant. "Plant Resins: Chemistry, evolution, ecology, and ethnobotany", by Jean Langenheim, Timber Press, Portland, OR. 2003
Amber is fossil resin (also called resinite) from coniferous and other tree species. Copal, kauri gum, dammar and other resins may also be found as subfossil deposits. Subfossil copal can be distinguished from genuine fossil amber because it becomes tacky when a drop of a solvent such as acetone or chloroform is placed on it.David Grimaldi, Amber: Window to the Past, 1996, p 16-20, American Museum of Natural History African copal and the kauri gum of New Zealand are also procured in a semi-fossil condition.
Rosin consists of a complex mixture of different substances including organic acids named the . Related to the terpenes, resin acid is oxidation terpenes. Resin acids dissolve in to form , from which the resin acids are regenerated upon treatment with acids. Examples of resin acids are abietic acid (sylvic acid), C20H30O2, plicatic acid contained in cedar, and pimaric acid, C20H30O2, a constituent of galipot resin. Abietic acid can also be extracted from rosin by means of hot alcohol.
Rosin is obtained from and some other , mostly Pinophyta. Plant resins are generally produced as stem secretions, but in some Central and South American species of Dalechampia and Clusia they are produced as pollination rewards, and used by some stingless bee species in nest construction. Propolis, consisting largely of resins collected from plants such as poplars and , is used by to seal small gaps in their hives, while larger gaps are filled with beeswax.
Asphaltite and Utah resin are petroleum .
The word resin comes from French resine, from Latin resina "resin", which either derives from or is a cognate of the Greek ῥητίνη rhētínē "resin of the pine", of unknown earlier origin, though probably non-Indo-European.
The word "resin" has been applied in the modern world to nearly any component of a liquid that will set into a hard lacquer or Vitreous enamel-like finish. An example is nail polish. Certain "casting resins" and (such as epoxy resin) have also been given the name "resin".
Some naturally-derived resins, when soft, are known as 'oleoresins', and when containing benzoic acid or cinnamic acid they are called balsams. Oleoresins are naturally-occurring mixtures of an oil and a resin; they can be extracted from various plants. Other resinous products in their natural condition are a mix with natural gum or mucilaginous substances and known as . Several natural resins are used as ingredients in perfumes, e.g., balsams of Peru and tolu, elemi, styrax, and certain turpentines.
The hard transparent resins, such as the copals, , mastic, and sandarac, are principally used for varnishes and adhesives, while the softer odoriferous oleo-resins (frankincense, elemi, turpentine, copaiba), and gum resins containing essential oils (ammoniacum, asafoetida, gamboge, myrrh, and scammony) are more used for therapeutic purposes, food and incense. The resin of the Aleppo Pine is used to flavour retsina, a Greek resinated wine.
Non-resinous exudates
Other liquid compounds found inside plants or exuded by plants, such as Plant sap, latex, or mucilage, are sometimes confused with resin but are not the same. Saps, in particular, serve a nutritive function that resins do not.
Uses
Plant resins
Plant resins are valued for the production of , , and food . They are also prized as raw materials for the synthesis of other organic compounds and provide constituents of incense and perfume. The oldest known use of plant resin comes from the late Middle Stone Age in Southern Africa where it was used as an adhesive for hafting stone tools.
Animal resins
While animal resins are not as common as either plant or synthetic resins some animal resins like lac (obtained from Kerria lacca) are used for applications like sealing wax in India, "The art of sealing." and lacquerware in Sri Lanka.
Synthetic resins
Many materials are produced via the conversion of synthetic resins to solids. Important examples are bisphenol A diglycidyl ether, which is a resin converted to epoxy glue upon the addition of a hardener. Silicones are often prepared from silicone resins via RTV silicone. are used in and and harden or cure by exposure to oxygen in the air.
See also
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