Agriculture Reference
In-Depth Information
Fiber Structure
All fi bers generally have a similar structure. An outer layer, called the cuticle,
provides a protective coating for the inner layer, the cortex. In fi ne wools the
cuticle and the cortex are basically all there is, but in medium to coarse wools,
med fi bers, and kemp fi bers, the cortex surrounds a central layer, known as
the medulla. As fi bers move from medium wool to kemp, the medulla occu-
pies a greater part of the fi ber, with up to 60 percent of a kemp fi ber's diam-
eter taken up by medulla.
The cuticle is actually made of fl attened cells that overlap each other
like the scales of a fi sh. The scales of fi ne wool are coarser, while long wools
are smoother; this is why many long wools are more lustrous than the fi ne
wools. The cortex is what gives wool its elasticity, strength, and durability.
The medulla is a spongy material that reduces the crimp of the fi ber and may
interfere with the fi ber's ability to take up dye.
Like human hair, fi bers outside the body are dead. All growth takes place
in the skin, at the bulbous end of the root, and forces new wool up and out of
the skin. Wool is made primarily of amino acids that link together to form a
protein called keratin. The protein molecules of wool, unlike those of human
hair, are combined in a unique coiled structure that provides the amazing elas-
ticity that's common to wool fi bers. This structure is also porous, which allows
wool to absorb up to 18 percent of its weight in moisture without becoming
damp and up to 50 percent of its weight before becoming saturated.
medium wool fi ber
fi ne wool fi ber
hair fi ber
kemp fi ber
Wool, hair, and kemp fi bers have an outer cuticle that is made up of
scales and a water-resistant sheath coating, called the elasticum, that
covers the scales. The edges of the scales are more pronounced on fi ne
wools; they are smoother on coarser wools, which gives coarser wool a
more lustrous character.
 
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