HISTORY OF SILK FIBRE:
The world is using silk as textile fibre for a very long time ago. Chinese were aware of the use of silk filaments as textile fibre in 2700 BC. They dominated for near about 1000 years in silk production. The got succeeded to maintain their dominance in the field of silk production. They kept a monopoly on silk production for one thousand years. Japanese learned the use of silk in 300 CE. The Arabian knew about silk at the same time. The production of silk got spread around the world. The monopoly of the Chinese got broken. As the technique got developed and the spinning wheel came into existence. The silk yarn production became developed in most of the countries.
The industrial revolution completely changed the European silk industry. Due to technology development, the production cost of silk yarn became cheaper. After all technological innovations, the silk yarn is still expensive textile.
BIOLOGICAL CLASSIFICATION OF SILK
Chemical composition of silk fibre is given below:
CHEMICAL STRUCTURE (FORMULA) OF SILK FIBRE:
Silk fibre obtained from silkworm is composed of mainly two type of proteins. One is sericin and other is fibroin. Fibroin is the structural centre of the silk, and sericin is the sticky material surrounding it. “Fibroin mainly composites of the amino acids Gly-Ser-Gly-Ala-Gly-Ala and forms beta-pleated sheets, β-keratin”.
R = H, glycine; R = CH3, alanine; R = CH2OH, serine
Hydrogen bonds form between chains and side chains from above and below the plane of the hydrogen bond network.
( fibroin protein in silk)
SILK FIBRES PRODUCTION:
Cultivation of the silkworm is called sericulture”. Many insects produce silk, but only the filament produced by Bombyx mori, the mulberry silk moth, and a few others in the same genus, are used by the commercial silk industry. Following stages come in production of silk fibre:
Hatching the eggs:
The first stage of silk production is the laying of silkworm eggs, The female deposits 300 to 400 eggs at a time. A one square foot area gets covered with the eggs of near about 100 female's eggs. The eggs are tested for any disease too. The size of each egg looks like a pinhead. The females are get died after egg deposition. The male moth also gets died after some time without damaging these eggs. A shoebox is needed to keep the silkworms. A place is decided in the room where sunlight does not hit directly but a warmness is getting felt. Now the shoeboxes are placed at the chosen place. The top of the box is covered with plastic sheets. These plastic covers help to reduce the evaporation of moisture of leaves without developing a humid atmosphere inside the shoeboxes. These eggs are lubricated for approximately one week. The eggs of silkworm are scattered all over the boxes. The larvae are developed from these eggs.
Feeding of the caterpillar:
The larvae are placed on the leaves. The new laevaes are rotated up every day. The fresh mulberry leaves are fed to them.
The eggs get developed. Now, these larvae get changed into the caterpillar. These caterpillars use mulberry leaves as food for approximately one month. The caterpillar moults through four-time skin. The weight of the caterpillar gets increased by many times.
The silkworm begins to attach themselves to a compartmented frame to spin a silk cocoon for a few days. “This period is termed pupating”. The silkworms has a pair of specially modified salivary glands called sericteries. The caterpillar uses these glands to produce the fibroin. A clear, viscous, proteinaceous fluid is forced through spinnerets( mouth organ) by the caterpillar. The liquid secretions from the two large glands in the insect come out from the spinneret, a single exit tube in the head. “The diameter of the spinneret determines the fineness of the silk filament, The secretions get hardened on exposure to the air and form twin filaments composed of fibroin, a protein material. The second pair of glands secrete a gummy binding fluid called sericin which bonds the two filaments together. The silkworm spins a 1-kilometer filament approximately. The spinning process gets continued until the development of the pupa. This cocoon works like a protection cover for the pupa to be developed just after the end of the spinning. This spinning process is ended completely almost within three days. Now cocoon is fully developed. This cocoon looks like a peanut shape and size. When the cocoon gets developed fully, the pupa is killed with the help of boiling water or steam.
Reeling the Filament:
After killing the pupas present inside the cocoon after boiling or steaming, the filament needs to convert into reel form. The filaments of four to eight cocoons are grouped together as per required yarn fineness. This process is performed with high careness. The hanks Or skeins of yarn are manufactured by the reeling process. A slight twist also provided to the yarn during reeling if needed.
“The process of the conversion of raw silk into a sufficient, strong strand by twisting is called throwing. The silk yarn gets suitable for weaving or knitting Throwing helps to prevent the thread from splitting into its constituent fibres.
Broken or waste filaments and damaged cocoons are retained, treated to remove the sericin, and combed. This is then processed into yarn, marketed as spun silk, which is inferior in character to the reeled product and much cheaper.
MAJOR SILK PRODUCING COUNTRIES:
The silk fibre is cultivated in more than 40 countries in the world. China and India main share the main silk production in the world. Around 95% of the silk production of the world comes from Asian countries. China is the biggest producer of silk today. India is the second-largest producer of silk in the world. The main silk-producing countries are being given below:
MAJOR SILK PRODUCING STATES IN INDIA:
India is the second-biggest producer of silk. It is also the largest consumer of silk in the world. It has a strong “tradition and culture-bound domestic market of silk”. In India, mulberry silk is produced mainly in the following states:
4-Jammu & Kashmir.
The non-mulberry silk is produced in the following states:
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