Silk Dresses Biography
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Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity (sericulture). The shimmering appearance of silk is due to the triangular prism-like structure of the silk fibre, which allows silk cloth to refract incoming light at different angles, thus producing different colors.
Silk is produced by several other insects, but generally only the silk of moth caterpillars has been used for textile manufacturing. There has been some research into other types of silk, which differ at the molecular level. Silk is mainly produced by the larvae of insects undergoing complete metamorphosis, but some adult insects such as webspinners also produce silk, and some insects such as raspy crickets produce silk throughout their lives. Silk production also occurs in Hymenoptera (bees, wasps, and ants), silverfish, mayflies, thrips, leafhoppers, beetles, lacewings, fleas, flies, and midges. Other types of arthropod produce silk, most notably various arachnids such as spiders.
Production process:
The entire production process of silk can be divided into several steps which are typically handled by different entities[clarification needed]. Extracting raw silk starts by cultivating the silkworms on mulberry leaves. Once the worms start pupating in their cocoons, these are dissolved in boiling water in order for individual long fibres to be extracted and fed into the spinning reel.
Properties:
Physical properties
Silk fibers from the Bombyx mori silkworm have a triangular cross section with rounded corners, 5–10 ?m wide. The fibroin-heavy chain is composed mostly of beta-sheets, due to a 59-mer amino acid repeat sequence with some variations. The flat surfaces of the fibrils reflect light at many angles, giving silk a natural sheen. The cross-section from other silkworms can vary in shape and diameter: crescent-like for Anaphe and elongated wedge for tussah. Silkworm fibers are naturally extruded from two silkworm glands as a pair of primary filaments (brin), which are stuck together, with sericin proteins that act like glue, to form a bave. Bave diameters for tussah silk can reach 65 ?m. See cited reference for cross-sectional SEM photographs.
Silk has a smooth, soft texture that is not slippery, unlike many synthetic fibers.
Silk is one of the strongest natural fibers, but it 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.
One example of the durable nature of silk over other fabrics is demonstrated by the recovery in 1840 of silk garments from a wreck of 1782: 'The most durable article found has been silk; for besides pieces of cloaks and lace, a pair of black satin breeches, and a large satin waistcoat with flaps, were got up, of which the silk was perfect, but the lining entirely gone ... from the thread giving way ... No articles of dress of woollen cloth have yet been found.
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 should either be washed prior to garment construction, or dry cleaned. 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 nor shrinkage due to molecular-level deformation.
Natural and synthetic silk is known to manifest piezoelectric properties in proteins, probably due to its molecular structure.
Silkworm silk was used as the standard for the denier, a measurement of linear density in fibers. Silkworm silk therefore has a linear density of approximately 1 den, or 1.1 dtex.
Chemical properties
Silk emitted by the silkworm consists of two main proteins, sericin and fibroin, fibroin being the structural center of the silk, and serecin being the sticky material surrounding it. Fibroin is made up of the amino acids Gly-Ser-Gly-Ala-Gly-Ala and forms beta pleated sheets. Hydrogen bonds form between chains, and side chains form above and below the plane of the hydrogen bond network.
The high proportion (50%) of glycine allows tight packing. This is because glycine's R group is only a hydrogen and so is not as sterically constrained. The addition of alanine and serine makes the fibres strong and resistant to breaking. This tensile strength is due to the many interceded hydrogen bonds, and when stretched the force is applied to these numerous bonds and they do not break.
Silk is resistant to most mineral acids, except for sulfuric acid, which dissolves it. It is yellowed by perspiration. Chlorine bleach will also destroy silk fabrics.
Uses:
Silk filaments being unravelled from silk cocoons, Cappadocia, Turkey, 2007.
Silk's 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, ties, blouses, formal dresses, high fashion clothes, lining, lingerie, pajamas, robes, dress suits, sun dresses and Eastern folk costumes. Silk's attractive lustre and drape makes it suitable for many furnishing applications. It is used for upholstery, wall coverings, window treatments (if blended with another fiber), rugs, bedding and wall hangings.[citation needed] While on the decline now, due to artificial fibers, silk has had many industrial and commercial uses, such as in parachutes, bicycle tires, comforter filling and artillery gunpowder bags.[citation needed]
Fabrics that are often made from silk include charmeuse, habutai, chiffon, taffeta, crepe de chine, dupioni, noil, tussah, and shantung, among others.
A special manufacturing process removes the outer irritant sericin coating of the silk, which makes it suitable as non-absorbable surgical sutures. This process has also recently led to the introduction of specialist silk underclothing for people with eczema where it can significantly reduce it. New uses and manufacturing techniques have been found for silk for making everything from disposable cups to drug delivery systems and holograms. To produce 1 kg of silk, 104 kg of mulberry leaves must be eaten by 3000 silkworms. It takes about 5000 silkworms to make a pure silk kimono. The production of silk is called sericulture. The major silk producers are China (54%) and India (14%).
Cultivation:
Silk moths lay eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed on fresh mulberry leaves. After about 35 days and 4 moltings, the caterpillars are 10,000 times heavier than when hatched and are ready to begin spinning a cocoon. A straw frame is placed over the tray of caterpillars, and each caterpillar begins spinning a cocoon by moving its head in a pattern. Two glands produce liquid silk and force it through openings in the head called spinnerets. Liquid silk is coated in sericin, a water-soluble protective gum, and solidifies on contact with the air. Within 2–3 days, the caterpillar spins about 1 mile of filament and is completely encased in a cocoon. The silk farmers then kill most caterpillars by heat, leaving some to metamorphose into moths to breed the next generation of caterpillars. Harvested cocoons are then soaked in boiling water to soften the sericin holding the silk fibers together in a cocoon shape. The fibers are then unwound to produce a continuous thread. Since a single thread is too fine and fragile for commercial use, anywhere from three to ten strands are spun together to form a single thread of silk.
Animal rights:
As the process of harvesting the silk from the cocoon kills the larvae, sericulture has been criticized by animal welfare and rights activists. Mohandas Gandhi was critical of silk production based on the Ahimsa philosophy which led to promotion of cotton and Ahimsa silk, a type of wild silk made from the cocoons of wild and semi-wild silk moths. Due to the death that silk production inflicts on the silkworms,[54] People for the Ethical Treatment of Animals (PETA) urges people not to buy silk items.
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
Silk Dresses Salmon Recipes Oven With Sauce Grilled Easy For Christmas Pinoy Healthy With Rice Pan Indian Style Photos
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