Synthetic Fibres and Plastics

Silk

The birthplace of Silk fibre is China. China produces the best quality of silk fibre. There are different types of Silk- cultivated silk and wild silk. Cultivated silk is also known as commercial silk or bombyx silk. Commercial or mulberry silk is white in colour and the diameter of the silk is 10 to 14 microns. The commercial silks are round in cross-section. Mulberry silk is mainly produced from cocoons of the mulberry silkworm. Mulberry silkworm or Bombyx mori is a caterpillar that eats mulberry leaves and from this cocoons, mulberry or commercial silk is produced.

Silk is a fine continuous monofilament fibre. It has high lustre and strength and it is very much popular as prestige fibre. There are various types of silkworm produced in India such as mulberry silk, Muga silk, tussar silk and Eri silk. The cost of the silk is very high. Tussar silk, Muga silk, eri silk are mainly wild silk.

Silk

                                                                                                                  Silk

Manufacturing Process of Silk

There are different varieties of silkworm are available from which the silk fibre can be made. The fibre obtained from the larva of bombyx Mori is of commercial value hence it is known as commercial silk. The manufacturing process of making silk from bombyx Mori requires very careful observation of the cocoons.

This cocoons puts through the spinning process and produces commercial silk or mulberry silk. Cultivation of silkworm for the production of raw silk is known as sericulture. Sericin is a type of silk gum which connects the continuous filament fibre consisting of fibroin together.

Fibroin is a natural protein which is secreted from two salivary glands of the silkworm. There are mainly four stages in the life cycle of moth. First, the egg which develops into a larva or caterpillar this is a silkworm. Then the silkworm spins its cocoon for protection. This develops the pupa or chrysalis. Now the chrysalis emerges as moth from the cocoon of the silkworm. And the female moth continuing their life and they lay eggs.

Cultivation of Cocoons

Cultivation of cocoons is known as sericulture. Now the silk moth lays eggs and these eggs hatch into ant which is a larva. The size of the larva is about \(\frac{1}{8}\) inches or \(3mm\) in length. The larva at this stage requires very good nourishment. They need chopped mulberry leaves five times a day. After reaching their full growth the size of the larva is about cm long. In this period they change their skin four times.

After full growth, the larva ceases their interest in food and they give their full concentration on spinning their cocoons. The silkworm begins to secrete a protein like substance through a small opening under the caterpillar’s jaw which is the spinneret. The silk solidifies when it comes in contact with the outside environment.

It takes twenty-four hours for the silkworm to hide inside the cocoons and in three days the cocoon is complete to a size. The shape of the cocoon is like a peanut shell. The filament is in the form of a double strand of fibroin which is held together by a gummy substance is sericin or silk gum. As this cutting through damages the cocoon, the filament cannot be unwound in one long thread. Stoving or stifling is the process in which the life cycle of the cocoons is terminated. The cocoons are subjected to heat to suffocate the chrysalis.

The delicate silk filament is not harmed during the process. If the silk filament is not harmed the chrysalis inside the cocoon complete the life cycle and develops into a moth within two weeks. To emerge, the moth breaks open the cocoon by secreting an alkaline liquid which dissolves the filament. To unwind silk cocoons are subjected to a different process and they are delivered to a factory which is known as filature.

First, the cocoons are subjected to sorting cocoons then softening the sericin and then reeling the filament. The cocoons mainly sorted according to their colour, shape, size and texture. The colours of the cocoons are different in a different area. The colour of the cocoons in China is white; Japanese cocoons are creamy-white and yellow in colour whereas Italian cocoons are yellow.

Softening the Sericin

After the cocoons sorted according to their shape, size, the texture they are subjected to heat in boiling water which helps to soften the silk gum sericin that holds the cocoon filament in place. Raw silk mainly consists of eighty per cent fibroin protein and twenty per cent silk gum or sericin. During the softening process, the only one per cent of the sericin is removed as it is required to protect the cocoon during the further process.

Reeling the Filament

Reeling is the process where the silk filaments are unwound from the cocoon and then combine together to make a thread of raw silk. The filament made from a single cocoon is fragile, so it is important to join four to eight filaments in a row and make a reel. The reel of filament is the raw silk which is consists of forty-eight individual silk fibres. The silk gum sericin acts as an adhesive to hold the several filaments together to form a single reel. The length of the single reel is approximately a quarter of a mile long. The weight of one single reel is about five to ten pounds.

Now throwing in the process of twisting of one or more threads of raw silk into a strand for weaving or knitting. Next, the degumming of thrown silk is done. It is a process where the thrown silk yarns through final soap bath to remove the sericin. It brings the soft feel of the silk and it also reduces the weight by twenty-five per cent. After degumming process removes the gum, the colour of the silk becomes creamy white and it gives the luxuriant softness.

FAQs about Silk

Q.1 Why silk is more delicate than other materials?

Answer: Mainly silk is more susceptible than other materials to stains and damage from heat and light. So it needs more care to avoid stains and damage from heat and light. Hence silk is more delicate than other materials.

Q.2: How silk pillowcase minimizes sleep wrinkles?

Answer: Silk pillowcase minimizes because silk reduces friction on delicate skin and it helps to retain moisture.

Q.3: Describe Sericin.

Answer: Sericin is a type of silk gum which connects the continuous filament fibre consisting of fibroin together.

Q.4: Describe Charmeuse.

Answer: Charmeuse is a type of weaving silk reels into a certain pattern which creates a smooth finish on one surface and matte finish on the other side. All mulberry silk go through Charmeuse processing to give a smooth and matte finish to the silk reel.

Q.5: Give the definition of Momme.

Answer: Momme is the weight measurement units of silk. Less than twenty Momme is a lightweight silk reel.

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