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Viscose was the first man made fiber introduced in textile production.
Viscose has excellent properties that can be engineered and optimized
for different textile and nonwoven applications.
The name was adopted in 1924, in preference to ‘artificial
silk’, by the U.S. Dept. of Commerce and various commercial
associations. As early as 1665 the English naturalist Robert Hooke
had suggested the possibility of making artificial silk, but the
first artificial textile fiber was produced in 1884 by a French
scientist, Hilaire de Chardonnet, and was manufactured by him in
1889.
Unpopular at first because it was too lustrous and laundered poorly,
it has been steadily improved. Cellulose, originally from cotton
linters but now chiefly from wood pulp, washed, bleached, and pressed
into sheets, is dissolved by chemicals, then forced under pressure
through minute holes in a metal cap (spinneret), emerging as filaments
that unite to form one continuous strand solidified by passage through
a suitable liquid or warm air.
The spinning solution may be forced through a larger orifice or
slit to produce a monofilament, a ribbon, or a sheet. Filaments
are doubled and twisted into smooth, silk-like yarns or cut into
staple lengths and spun. Spun rayon can be treated to simulate wool,
linen, or cotton.
There are four methods of manufacturing rayon, using different
materials and processes:
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In the nitrocellulose process developed by Chardonnet and
no longer of commercial importance, cellulose is treated with
nitric and sulphuric acids.
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In the viscose process, discovered in 1892, it is treated
with carbon disulphide, then dissolved in caustic soda, forced
through a spinneret, and hardened in sulphuric acid. Viscose
rayon is the most important type commercially, being used in
most kinds of wearing apparel, furniture fabric, and carpets.
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For cuprammonium rayon, the cellulose is dissolved in copper
oxide and ammonia, forced through holes larger than the intended
diameter, then, by a process known as stretch spinning, is elongated
and twisted under tension to yield a very fine, strong yarn
used for sheer fabrics and hosiery.
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Rayon produced by these three methods is classified
as regenerated, since the final product, like the original material,
is cellulose.
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The fourth type, saponified acetate rayon, originated in
England in 1918 and is an acetate derivative of cellulose made
by steeping cellulose in acetic acid, then treating it with
acetic anhydride. Acetate rayon is more resistant to stains
and creasing, is plasticized by heat, and requires special dyes,
thus allowing two-tone effects with a single dye when acetate
is combined with other fibers. Acetate filler is used to make
shatterproof glass. |
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