resin
Any of various hard, brittle, solid, or semi-solid
amorphous, organic, fusible substances that are
insoluble in water but soluble in organic
solvents, and which are classified as natural or
synthetic. Resins contain a high proportion of
carbon but little oxygen, and have an indefinite
and often high molecular weight. The natural
resins are excretion or exudation products
principally of plant origin (a notable exception
being shellac), fusible, usually yellowish to dark
brown in color, and transparent to translucent.
"Recent resins" are those obtained from living
plants, while those dug from the earth where they
were deposited, are known as "fossil resins."
Chemically, resins consist of complex mixtures of
organic (resin) acids and alcohols, which are
generally aromatic in nature, and inert substances
(known as resenes), together with extraneous
fatty, mineral, or other materials. Gum resins
contain carbohydrate gums, while oleoresins are
mixtures of resins and volatile oils. The
non-volatile residue of conifer resins is called
ROSIN , which is
the most important resin used in the manufacture
of paper. Other more-or-less familiar resins
include copal and dammar, which are natural resins
used in the manufacture of varnish, accroides,
amber, elemi, ester gum, manila copal, mastic,
sandarac, and shellac. See also: SYNTHETIC RESINS .
(17 , 233 , 235 , 309 )
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