Aresin is a solid or highlyviscous liquid that can be converted into apolymer.[1] Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures oforganic compounds insoluble in water, predominantlyterpenes. Technically, resins should not be confused withgums, which consist predominantly of water-solublepolysaccharides, although these two terms are often interchangeable in the less formal context. Common resins include pineoleoresins,amber,hashish,frankincense,myrrh and the animal-derived resin,shellac. Resins are used invarnishes,adhesives,food additives,incenses andperfumes.
Resins protect plants from insects and pathogens, and are secreted in response to injury. Resins repelherbivores, insects, and pathogens, while the volatilephenolic compounds may attract benefactors such as predators of insects that attack the plant.[2]
Amber isfossil 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 asacetone orchloroform is placed on it.[3]Africancopal and the kauri gum of New Zealand are also procured in a semi-fossil condition.
Rosin is a solidified resin from which thevolatile terpenes have been removed by distillation. Typical rosin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, non-odorous or having only a slight turpentine odour and taste. Rosin is insoluble in water, mostly soluble in alcohol,essential oils,ether, and hot fatty oils. Rosin softens and melts when heated and burns with a bright but smoky flame.
Rosin consists of a complex mixture of different substances including organic acids named theresin acids. Related to the terpenes, resin acid isoxidized terpenes. Resin acids dissolve inalkalis to formresin soaps, from which the resin acids are regenerated upon treatment with acids. Examples of resin acids areabietic acid (sylvic acid), C20H30O2,plicatic acid contained in cedar, andpimaric acid, C20H30O2, a constituent ofgalipot resin. Abietic acid can also be extracted from rosin by means of hot alcohol.
Rosin is obtained frompines and some otherplants, mostlyconifers.[4] Plant resins are generally produced as stem secretions, but in some Central and South American species ofDalechampia andClusia they are produced as pollination rewards, and used by somestingless bee species in nest construction.[5][6]Propolis, consisting largely of resins collected from plants such aspoplars andconifers, is used byhoney bees to seal small gaps in their hives, while larger gaps are filled with beeswax.[7]
The wordresin comes from Frenchresine, from Latinresina "resin", which either derives from or is acognate of the Greekῥητίνηrhētínē "resin of the pine", of unknown earlier origin, though probably non-Indo-European.[9][10]
The word "resin" has been applied in the modern world to nearly any component of a liquid that will set into a hardlacquer orenamel-like finish. An example is nail polish. Certain "casting resins" andsynthetic resins (such asepoxy resin) have also been given the name "resin".
Some naturally derived resins, when soft, are known as 'oleoresins', and when containingbenzoic acid orcinnamic 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 withgum or mucilaginous substances and known asgum resins. Several natural resins are used as ingredients in perfumes, e.g., balsams of Peru and tolu, elemi, styrax, and certain turpentines.[4]
Other liquid compounds found inside plants or exuded by plants, such assap,latex, ormucilage, are sometimes confused with resin but are not the same. Saps, in particular, serve a nutritive function that resins do not.
Plant resins are valued for the production ofvarnishes,adhesives, and foodglazing agents. They are also prized as raw materials for thesynthesis of other organic compounds and provide constituents ofincense andperfume. 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.[11]
Lumps of driedfrankincense resinCaranna, a hard, brittle, resinous gum from species ofProtium
^"Resin".IUPAC Compendium of Chemical Terminology. 3.0.1 (3rd ed.). International Union of Pure and Applied Chemistry. 2019.doi:10.1351/goldbook.RT07166.
^Bittrich, V.; Amaral, Maria C. E. (1996). "Flower morphology and pollination biology of some Clusia species from the Gran Sabana (Venezuela)".Kew Bulletin.51 (4):681–694.Bibcode:1996KewBu..51..681B.doi:10.2307/4119722.JSTOR4119722.
^Gonçalves-Alvim, Silmary de Jesus (2001). "Resin-collecting bees (Apidae) on Clusia palmicida (Clusiaceae) in a riparian forest in Brazil".Journal of Tropical Ecology.17 (1):149–153.doi:10.1017/s0266467401001092.S2CID85842020.
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