What is Silk?
The
word silk comes from ancient English: sioloc, from ancient Greek: σηρικός,
Romanized: serikos, "silken", finally compare from Asian sources
Mandarin s ī "silk". Silk is a natural protein fiber that we get from
insects that can be woven into textiles. Silk protein fibers are composed
primarily of fibroin and are produced by insect larvae specific to cocoon
formation. The most well-known silk captive mulberry silkworm Bombyx is found in
Mori's larvae cocoon.
Silk
is also produced by Hymenoptera (bees, seeds, and ants), Silverfish, Mayflies,
Thrips, Leafhoppers, Beetles, Lacewings, Flies, Flies, and Midge. Other types
of arthropods produce silk, especially arachnids like spiders.
Physical properties of Silk
Physical properties of silk are as below-
1. Silk fiber's cross-sectional view is triangular with rounded corners, 5–10 μm
wide.
2. It has a smooth, soft texture that is not slippery.
3. It is one of the strongest natural fibers, but it loses up to 20% of its
strength when wet.
4. It has a good moisture regain of 11%.
5.
Its elasticity is moderate to poor: if elongated even a small amount, it
remains stretched.
6. It can be weakened if exposed to too much sunlight.
7. It may also be attacked by insects, especially if left dirty.
8. It is a poor conductor of electricity and thus susceptible to static cling.
9. It has a high emissivity for infrared light, making it feel cool to the touch.
10.
Unwashed silk chiffon may shrink up to 8% due to a relaxation of the fiber
macrostructure, Dry cleaning may still shrink the chiffon up to 4%.
11.
It has a linear density of approximately 1 den or 1.1 dtex.
Chemical Properties of Silk
Chemical properties of silk are as below-
1. Silk is a natural protein fiber that consists of two main proteins, sericin,
and fibroin.
2. The high proportion (50%) of glycine allows tight packing.
3. It is resistant to most mineral acids, except for sulfuric acid, which
dissolves it.
4. It is yellowed by perspiration.
5. Chlorine bleach will also destroy silk fabrics.
6. Silk is readily decomposed by hot concentrated acids.
7. Caustic soda, when it is hot and strong dissolves the silk fiber.
8. Silk fibroin is not severely affected by the H2O2 solution.
Chemical Composition of Silk
Fibroin:
75%
Sericin:
22.5%
Fat
and
Wax:
1.5%
Ash
of Silk Fibroin: 0.5%
Mineral
Salt:
0.5%
The production process of Silk
The production process of silk begins with the Bombyx mori a small silkworm that
comes from the eggs of a silk moth. For their first year, these insects feed on
the leaves of the mulberry tree before making a cocoon with their spit. In its
original cocoon form, the raw silks are heavy and irregular.
Silk
weavers separate the completed cocoons from the mulberry bush and soak them in
a vat of boiling water to separate the silk thread from the caterpillar inside
the cocoon. The Bombyx mori generally produces silk threads of varying colors,
ranging from light gold to very light green, with lengths varying from 500 to
1,500 yards per cocoon.
A
single-thread filament is too thin to use on its own, so weaver women combine
many threads to produce a thicker and more usable fiber. They do this by spreading
the threads by hand over a wooden spindle to produce a uniform strand of raw
silk. The process is a tedious one as it takes nearly 40 hours to produce a
half kilogram of silk. Many local operations use a reeling machine for this
task, but the majority of silk thread is still hand-reeled. The difference
is that hand-rolled threads produce three grades of silk: two fine grades which
are ideal for lightweight fabrics and one dense grade for heavy material.
The
silk fabric is then soaked in hot water and bleached before dyeing to remove
the natural yellow coloring of Thai silk yarn. To do this, silk thread skins
are immersed in large tubs of hydrogen peroxide. Once washed and dried, the
silk is then woven using traditional hand-woven looms.
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