Skip to main content

Silk fiber and invention of silk fiber



Silk, the most elegan
t fiver, was discovered in China by Empress Si Ling Chi when she was sitting beneath a mulberry tree in the palace garden enjoying a cup of tea. Suddenly, a cocoon, which had been attached to the tree, fell into the Empress’ tea cup. Attempting to remove it, she was fascinated to discover a very fine thread started to unravel.

The filaments of silk that form the cocoon are triangular in shape and are composed of two fibers of fibroin and a supporting matrix of sericin. Sericin makes up 20% to 30% of the filaments and acts as a support to glue the cocoon together and also as a lubricant during spinning.

Fibroin has an average diameter of about 10 to 18 microns and is a protein that abounds in non-polar amino acids such as glycine and alanine. Whereas sericin is a protein that is water-soluble and composed of amino acids such as serine and aspartic acid. The sericin that envelopes the filaments is highly tenacious and requires high temperature alkaline processing to remove it completely in order to obtain raw silk. The tenacity and gum-like quality of sericin itself makes if a good candidate for biomedical joining and sealing applications.

Physical properties
Silk fibers have a triangular cross section with rounded corners. This allows light to hit at many different angles, so silk is a bright fiber and has a natural shine. It has a smooth, soft texture that is not slippery, unlike many synthetic fibers. Its denier is 4.5 g/d when dry and 2.8 – 4.0 g/d when wet. Silk is one of the strongest natural fibers but loses up to 20% of its strength when wet. It has a good moisture regain of 11%. Its elasticity is moderate to poor. if elongated even a small amount it remains stretched. It can be weakened if exposed to too much sunlight. It may also be attacked by insects, especially if left dirty. 
Silk is a poor conductor of electricity and thus susceptible to static cling.

Unwashed silk chiffon may shrink up to 8% due to a relaxation of the fiber macrostructure. So silk shoulder either be pre-washed prior to garment construction, or dry cleaner. Dry cleaning may still shrink the chiffon up to 4%. Occasionally, this shrinkage can be reversed by a gentle steaming with a press cloth. There is almost no gradual shrinkage or shrinkage due to molecular-lever deformation.
Silk is sensitive to higher temperatures. It should be, therefore, subjected to ironing at moderate temperature. Silk is sensitive to light than any other natural fibers. Yellowing of the fiber is generally accompanied by photo-degradation that is mainly occurred due to action of UV radiation of light.

Chemical properties
Action of Acids: Hot concentrated acids readily decomposes silk. The degree of hydrolysis is much greater with acid than with alkali and is pH dependent. Weak (5% solution) and cold hydrofluoric acid does not have any harmful action on silk. Dilute organic acids show little effect on silk at room temperature.
Action of Alkali: Dilute alkali temperature does not cause any considerable chemical and structural damage of silk, but the luster of the fiver may be decreased depending on the exposure time. Caustic soda, when it is hot and strong, dissolves the silk fiber.
Action of oxidizing and reducing agent: Silk fibroin is not severely affected by hydrogen peroxide solution. The action of chorine solution on the silk fibroin is more harmful than does the solution of hypochlorite. The reducing agents that are commonly found in use in textile processing such as hyposulphite, sulfurous acids and their salts do not exercise any destructive action on the silk fiber.

Uses of Silk
Silk’s good absorbency makes it comfortable to wear in warm weather and while active. Its low conductivity keeps warm air close to the skin during cold weather. It is often used for clothing such as shirts, blouses, formal dresses, high fashion clothes, negligees, pajamas, robes, skirt suits, sun dresses and underwear.

Silk’s elegant, soft luster and beautiful drape makes it perfect for many furnishing applications. It is used for upholstery, wall coverings, window treatments (if blended with another fiber), rugs, bedding and wall handing. Silk is also used for parachutes, bicycle tires, comforter filling and artillery gunpowder bags.

Early bulletproof vests were made from silk in the era of black powder weapons until roughly world war I. A special manufacturing process makes it suitable as non-absorbable surgical sutures. Chins doctors have used it to make prosthetic arteries. Silk cloth is also used as a material to write on.

Comments

Popular posts from this blog

macro-structure of cotton fiber | Under a microscope cotton

Under a microscope a cotton fiber appears as a very fine, regular fiber, looking like a twisted ribbon or a collapsed and twisted tube. These twists are called convolutions there are about sixty convolutions per centimeter. The convolutions give cotton an uneven fiber surface, which increases inter-fiber friction and enables fine cotton, yearns of squatted strength to be spun. The appearance of the cotton fiber’s cross sections is referred as being kidney-shaped. The micro structure of cotton The cotton fiber is a single plant cell. Its cross-section is oval, compared with the normal hexagonal plant cell. Cotton has a district cuticle, well developed primary and secondary walls and a lumen. Layer 1 the cuticle is a waxy protective layer that provides water resistance to the fibers as they are growing. This lawyer is removed by scouring during processing before spinning.

Importance of twisted structure of textile fiber

Trelor in his Mather lecture, titled “Twisted Structures” adequately recognizes the role of twist in yarns and the part it plays in the design of textile structures .He discusses the obvious necessity of twist in the natural and staple fibers by pointing out “ Twist is essential to provide a certain minimum coherence between fibers, without a yarn having a significant tensile strength cannot be made. This coherence is dependent on the frictional forces brought into play by the lateral pressures between fibers arising from the application of a tensile stress along the yarn axis. With the introduction of continuous filament yarns, however, the role of twist must be reconsidered. In continuous filament yarns, twist is not necessary for the attainment of tensile strength (in fact, it reduces it) but it is necessary for the achievement of satisfactory resistance to abrasion, fatigue, or other types of damage associated with stresses other than a simple tensile stress, and typified ...

Types of Yarn twist | different types of yarn twist | S twist | Z twist

Types of Yarn twist different types of yarn twist S twist Z twist“S” TWIST: A single yarn has “S” twist if when it is held in the vertical direction , the fibers inclined to the conform in direction of slope of the contact portion of the letter “S”. axis of the yarn “Z” TWIST. A single has “Z” twist if when it is held in the vertical direction, the fibers inclined to the yarn axis conform in the direction of the slope to the central portion of the letter “Z”. DIRECTION OF TWIST: In the designation of yarns, it is essential to specify the direction of twist. Besides its importance in simplifying the trade, it is of great technical importance in designing fabrics. For example, in a twill fabric, the direction of twist in the yarn is of particular importance in determining the predominance of twill effect. For a   right-handed twill, the best contrasting effect will be obtained when a yarn with Z twist is used; on the other-hand a left-handed twist will produce a fabric ha...