{{this|the plant secretion}}
[[Image:Resin with insect (aka).jpg|thumb|Insect trapped in resin.]]
'''Resin''' is a [[hydrocarbon]] [[secretion]] of many [[plant]]s, particularly [[Pinophyta|coniferous trees]], valued for its chemical constituents and uses such as [[varnish]]es, [[adhesive]]s, as an important source of raw materials for [[organic synthesis]], or for [[incense]] and [[perfume]]. [[Fossil]]ized resins are the source of [[amber]].  The term is also used for synthetic substances of similar properties.

==Chemistry==
[[Image:Résine.jpg|thumb|Resin of a pine]]
The resin produced by most plants is a [[Viscosity|viscous]] [[liquid]], typically composed mainly of volatile fluid [[terpene]]s, with lesser components of dissolved non-volatile solids which make resin thick and sticky. The most common terpenes in resin are the bicyclic terpenes [[alpha-Pinene|alpha-pinene]], [[pinene|beta-pinene]], [[carene|delta-3 carene]] and [[sabinene]], the monocyclic terpenes [[limonene]] and [[terpinolene]], and smaller amounts of the tricyclic [[sesquiterpene]]s [[longifolene]], [[caryophyllene]] and [[cadinene|delta-cadinene]]. Some resins also contain a high proportion of [[resin acid]]s.  The individual components of resin can be separated by [[fractional distillation]]. 

A few plants produce resins with different compositions, most notably [[Jeffrey Pine]] and [[Gray Pine]], the volatile components of which are largely pure [[heptane|''n''-heptane]] with little or no terpenes. The exceptional purity of the ''n''-heptane distilled from Jeffrey Pine resin, unmixed with other [[isomer]]s of [[heptane]], led to its being used as the defining zero point on the [[octane rating]] scale of [[petrol]] quality. Because heptane is highly flammable, distillation of resins containing it is very dangerous. Some resin distilleries in [[California]] exploded because they mistook Jeffrey Pine for the similar but terpene-producing [[Ponderosa Pine]]. At the time the two pines were considered to be the same species of pine; they were only classified as separate species in [[1853]].

Some resins when soft are known as ''oleo-resins'', and when containing [[benzoic acid]] or [[cinnamic acid]] they are called [[balsam]]s. Other resinous products in their natural condition are a mix with [[natural gum|gum]] or [[mucilaginous]] substances and known as [[gum resin]]s. Many compound resins have distinct and characteristic odors, from their admixture with [[essential oil]]s.

Certain resins are obtained in a fossilized condition, [[amber]] being the most notable instance of this class; [[Africa]]n [[copal]] and the [[kauri]] gum of [[New Zealand]] are also procured in a semi-fossil condition.

==Derivatives==
Solidified resin from which the volatile terpene components have been removed by distillation is known as [[rosin]]. 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. It is insoluble in water, mostly soluble in alcohol, essential oils, ether and hot fatty oils, softens and melts under the influence of heat, is not capable of [[sublimation]], and burns with a bright but smoky flame. This comprises a complex mixture of different substances including organic acids named the [[resin acid]]s. These are closely related to the terpenes, and derive from them through partial [[oxidation]]. Resin acids can be dissolved in [[alkali]]s to form [[resin soap]]s, from which the purified resin acids are regenerated by treatment with acids. Examples of resin acids are [[abietic acid]] (sylvic acid), C<sub>20</sub>H<sub>30</sub>O<sub>2</sub>, [[plicatic acid]] contained in cedar, and [[pimaric acid]], C<sub>20</sub>H<sub>35</sub>O<sub>2</sub>, a constituent of [[gallipot resin]]. Abietic acid can also be extracted from rosin by means of hot alcohol; it crystallizes in leaflets, and on oxidation yields [[trimellitic acid]], [[isophthalic acid]] and [[terebic acid]]. Pimaric acid closely resembles abietic acid into which it passes when distilled in a [[vacuum]]; it has been supposed to consist of three isomers.

==Synthetic resins==
Synthetic resins are materials with similar properties to natural resins—[[viscosity|viscous]] liquids capable of hardening. They are typically manufactured by [[esterification]] or [[soap]]ing of [[organic compounds]].
The classic variety is [[epoxy|epoxy resin]], manufactured through [[polymerization]]-polyaddition or polycondensation reactions, used as a [[thermoset]] polymer for adhesives and [[composite material|composite]]s.  One more category, which constitutes 75% of resins used, is unsaturated polyester resin.  [[Ion exchange resin]] is another important class with application in [[water purification]] and [[catalysis]] of [[organic reaction]]s.  See also [[AT-10 Resin]].

==Uses==
[[Image:Frankincense_2005-12-31.jpg|thumb|Lumps of dried [[Frankincense]] resin]]
The hard transparent resins, such as the [[copal]]s, [[dammar]]s, [[mastic]] and [[sandarac]], are principally used for [[varnish]]es and [[cement]], while the softer odoriferous oleo-resins ([[frankincense]], [[elemi]], [[turpentine]], [[copaiba]]) and gum resins containing essential oils ([[ammoniacum]], [[asafoetida]], [[gamboge]], [[myrrh]], and [[scammony]]) are more largely used for therapeutic purposes and [[incense]].

Resin in the form of [[rosin]] is used for the upkeep of bows for stringed instruments (i.e. [[violin]], [[viola]], [[cello]], [[double bass]]), because of its quality for adding friction to the hair.

Resin has also been used as a medium for sculpture by artists such as [[Eva Hesse]], and in other types of artwork.

==References==
{{Unreferenced|date=December 2006}}

{{Commons|Resin}}

[[Category:Resins|*]]
[[Category:Botany]]

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