Resin

/rez"in/, n.

a male given name.

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Any natural or synthetic organic compound consisting of a noncrystalline (amorphous) solid or viscous liquid substance or mixture.

Natural resins are usually transparent or translucent yellow to brown and can melt and burn. Most are exuded from trees, especially pines and firs (see conifer), when the bark is injured or stripped. The fluid secretion usually dries out and hardens into a material that can be worked. Natural resins have been used in perfumes and medicines (e.g., balsams), in paints and varnishes (e.g., turpentine and shellac, the latter derived from the secretion of an insect), and in decorative ware (e.g., amber, Oriental lacquer). Synthetic resins are all plastics; the term resin, though still used in the modern industry, dates from the years when synthetics began to replace natural resins. Thermoplastic resins are plastics such as polyethylene that can be shaped repeatedly on reheating, whereas thermosetting resins are plastics such as epoxy that set permanently and cannot be reshaped.

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▪ chemical compound

      any natural or synthetic organic compound consisting of a noncrystalline or viscous liquid substance. Natural resins are typically fusible and flammable organic substances that are transparent or translucent and are yellowish to brown in colour. They are formed in plant secretions and are soluble in various organic liquids but not in water. Synthetic resins comprise a large class of synthetic products that have some of the physical properties of natural resins but are different chemically. Synthetic resins are not clearly differentiated from plastics.

      Most natural resins are exuded from trees, especially pines and firs. Resin formation occurs as a result of injury to the bark from wind, fire, lightning, or other cause. The fluid secretion ordinarily loses some of its more volatile components by evaporation, leaving a soft residue at first readily soluble but becoming insoluble as it ages. The ancient Chinese, Japanese, Egyptians, and others used resins in preparation of lacquers and varnishes.

      Natural resins may be classified as spirit-soluble and oil-soluble. Among the former are balsams, long popular as a healing agent; turpentines used as solvents; and mastics, dragon's blood, dammar, sandarac, and the lacs, all used as components of varnishes. The oil-soluble resins include rosin, derived along with turpentine from the long-leaf pine and long used for a variety of applications, including soapmaking; copals, used in varnishes; amber, the hardest natural resin, fabricated into jewelry; Oriental lacquer, derived from a tree native to China; and cashew-nutshell oil, derived from cashew nuts.

      In modern industry natural resins have been almost entirely replaced by synthetic resins, which are divided into two classes, thermoplastic resins, which remain plastic after heat treatment, and thermosetting resins, which become insoluble and infusible on heating.

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