Resin

In polymer chemistry and materials science, a resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers.^[1] Resins are usually mixtures of organic compounds. 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.

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.^[4] African copal and the kauri gum of New Zealand are also procured in a semi-fossil condition.

Rosin

Rosin is a solidified resin from which the volatile 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 the

Shellac is an example of an insect-derived resin.

Asphaltite and Utah resin are petroleum bitumens.

History and etymology

Human use of plant resins has a very long history that was documented in ancient Greece by Theophrastus, in ancient Rome by Pliny the Elder, and especially in the resins known as frankincense and myrrh, prized in ancient Egypt.^[9] These were highly prized substances, and required as incense in some religious rites.

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.^[10][11]

The word "resin" has been applied in the modern world to nearly any component of a liquid that will set into a hard

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 gum or mucilaginous substances and known as gum resins. Several natural resins are used as ingredients in perfumes, e.g., balsams of Peru and tolu, elemi, styrax, and certain turpentines.^[5]

Non-resinous exudates

Other liquid compounds found inside plants or exuded by plants, such as

Uses

Plant resins

Plant resins are valued for the production of varnishes, adhesives, and food glazing agents. 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.^[12]

The hard transparent resins, such as the copals,

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,^[14] and lacquerware in Sri Lanka.^{[citation needed]}

Synthetic resins

Many materials are produced via the conversion of synthetic resins to solids. Important examples are

• Amber
• Resin extraction – method of harvesting resin from trees
• Balsam of Peru – a balsam used in food and drink for flavoring, in perfumes and toiletries for fragrance, and in medicine and pharmaceutical items.
• Mastic (plant resin) – resin from the Pistacia lentiscus tree
• Pitch (resin)
• Kino (gum)
  – a plant gum similar to resin
• Biodegradable
  – plant resins are naturally biodegradable in many circumstances.
• Resin casting – casting with a resin, usually using a synthetic not a natural resin.
• Polyresin
  – a hard, synthetic resin for casting in molds

References