Silk fiber | History, Properties, Cultivation, Composition | Manufacturing process

 

Silk

Silk fiber

The word silk comes from Old English: Sioloc, from ancient Greek: σηρικός, Romanized: serikos, "silken", finally compare Mandarin from Asian sources Mandarin s ī "silk". Silk fiber is a natural protein fiber that we get from insects that can be woven into textiles. Silk protein fibers are composed mainly of fibroin and some insect larvae produce cocoons. The most well-known silk gun (sericulture) mulberry silkworm is obtained from the larvae cocoon of Bombyx mori. The shiny appearance of silk is due to the triangular prism structure of silk fiber which allows the silk fabric to reflect the light coming from different angles, thus producing different colors. The silk fiber is produced by several insects but moth caterpillar silks are used to make textiles. There have been some studies on other types of silk, which differ at the molecular level. Silk is generally produced by the larvae of fully transformed insects, but some insects like web spinners and racist crickets make lifelong silk.

Silk fiber

History of Silk

Neolithic 1st silk production in China. During the last half of the first millennium BC, the Silk Road was confined to China until it reached a certain stage. China has maintained a virtual monopoly on silk production for thousands of years. Not limited to clothing, silk was also used for many other applications, including composition, and the color of the silk worn was an important guide to social class during the Tang Dynasty.

Silk cultivation spread to Japan around 300 AD and during Byzantine time silkworm eggs were able to hatch and silkworm farming was started. The Arabs also started producing silk at the same time. As a result of silk cultivation, Chinese silk exports became less important even though they still dominated the luxury silk market. The Crusades brought silk production to Western Europe, especially to many states in Italy that saw the export of silk to the rest of Europe at an economic pace. The Industrial Revolution changed much of Europe's silk industry. Due to the invention of spin cotton, it became much cheaper to make cotton and as a result, more expensive silk production became less mainstream.

New weaving technologies, however, have increased production efficiency. Among these was the Jacquard loom, which was made for silk embroidery. Epidemic production of several silkworm diseases declined, especially in France, where the industry never recovered. In the twentieth century, Japan and China regained their former role in silk production, and China is now again the world's largest producer of silk. The emergence of new fabrics like nylon has reduced the prevalence of silk around the world and silk is now again a rare luxury good, less important than its turbulent days.

Properties of silk fiber

i. Silk filament is very strong due to its linear, beta configuration polymers and very crystalline polymer system. Its strength reduces when wet.

ii. Degummed silk's specific gravity is 1.25.

iii. It is flexible enough and if used to make garments then the fabric drapes well.

iv. It has an elongation at a break of 20-25% under normal conditions.

v. It is a poor conductor of electricity and tends to form a static charge when it is handled.

vi. It is considered to be more plastic than elastic because it's very crystalline polymer does not permit the amount of polymer movement which could occur in a more amorphous system

vii. It is less absorbent than wool but more absorbent than cotton but it is a crystalline polymer.

viii. Silk fiber dissolves in concentrated mineral acid but organic acids do not harm it.

ix. It is not as sensitive as wool to alkalis, but it can be damaged if the concentration and the temperature are high enough.

x. Strong bleaches destroy silk fiber, but hydrogen peroxide does not affect it.

xi. Raw silk is more resistant to light than degummed silk.

xii. It is resistant to mildew effects.

xiii. It has a very good affinity to dyes such as acid, basic and direct dyes.

Silk fiber composition

Fibroin - 76%

Sericin - 22%

Fat & wax - 1.5%

Mineral salt - 0.5%

Cultivation of Silk

Silk moths lay their eggs mainly on prepared paper. Eggs are hatched and dried fresh mulberry leaves are fed. After about 35 days and 4 hatchings, the caterpillars become 10,000 times heavier than the cubs and are ready to start cutting a cocoon. A straw frame is placed on top of the caterpillar tray and each caterpillar moves its head in a pattern and begins to spin a cocoon. The two glands produce liquid silk and force it through the opening of the head called spinnerets. Liquid silk is coated with sericin, a water-soluble protective gum, and solidifies in contact with air. Within 2-3 days, the caterpillar spins about 1-mile filament and is completely enclosed in a cocoon. Silk farmers heat the cocoons to kill them and turn some into insects to breed the next generation of dry ones. The cut cocoons are boiled and the silk fibers soaked in water hold the silk fibers together to form a cocoon. The fibers are then unwrapped to form unbroken threads. Since the single thread is very delicate and fragile for commercial use, three to ten strands are cut together anywhere to make a single thread of silk.

Silk cocoons

Silk fiber manufacturing process

The silk fiber manufacturing process manual is as follows-

i. Sericulture

The cultivation of silkworms to produce silk is called sericulture. The best raw silk is obtained from insects of the species Bombyx mori. Silkworms breed once a year but can be kept up to three times a year under scientific conditions. About 3 mm larvae emerge from the eggs. Female silkworms lay 300 to 500 eggs. Silkmoth eggs form larvae or caterpillars known as silkworms. The larvae feed on the leaves of the larvae. After growing several times, the silkworm pulls out a silk fiber and forms a net to hold itself. It always itself from side to side distributes saliva which will make silk. Silk hardens when in contact with air. The silkworm spins about a mile of filament and in about two or three days completely encloses itself in a cocoon. As a result, about 2,500 silkworms are needed to produce about one thousand pounds of raw silk. The intact cocoon is cooked, the silkworm kills the pupa. Silk is obtained by brushing the useless cocoon to find the outer edge of the filament. The filaments of silk are then wound into a relay. A cocoon contains about 1000 yards of silk filament. Silk at this stage is known as raw silk. A thread has 48 separate silk filaments.

ii. Shorting cocoons

The cocoons are selected according to color, shape, and texture, as they all affect the final quality of the silk. Cuckoos can range in color from white or yellow to gray, depending on the source and type of food when eating at the insect stage. Cocoons from China are white, Japanese cocoons are creamy-white and yellow, Italian cocoons are yellow.

iii. Softening sericin

After the cocoons are picked and the silk gum is called sericin, which cements the filaments. Sericin is removed by placing the cocoon in hot water, which frees the silk fibers and prepares them for reeling. This is known as the degumming process. Immersion in hot water also kills silk math pupa.

iv. Reeling

Reeling can be achieved manually or automatically. The end of the cocoon fiber is brushed to identify. The method is as simple as it is laborious. It is threaded through a porcelain eyelet, and the fiber is reeled on a wheel. Meanwhile, diligent operators check for filament errors as they are being relayed. As soon as each filament is almost finished reeling, a new fiber is bent into it, creating a long, unbroken thread. Ceresin contributes to the attachment of fibers to each other. The average cocoon reels about three hundred yards away in a single thread.

v. Throwing

The production of yarn from silk, known as throwing, involves adding or twisting a twist and twisting these strands to the desired shape. The single filaments are joined together to form a thread, which is drawn by pulling through several guides and hitting the reels. Threads can be driven to make yarn. After drying, the raw silk is packed according to the quality.

Silk fiber manufacturing process

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