More About Silk

Silk is one of the oldest and most useful animal fibres known to man. Silk Thread is a product of the silk-producing glands of certain insects that create net around themselves or form cocoons. The larva of a silk moth develops by feeding on mulberry leaves and coils cocoon with filament 12-20 µm in diameter and up to 1.5 km long. Silkworm domestication and silk production began in China more than 5000 years ago. A mulberry silkworm was brought to Europe in the 6th century AD [1,2].

Silk fibre consists of two proteins: fibroin is in the inner layer (72–83% of fibre weight), which gives strength to a fibre; sericin is in the outer layer, which binds fibroin filaments together (17–28%); there are also 0.8–1.0% of fatty and waxy substances, 1.0–1.4% of mineral substances and 11% of water [1]. The amino acid profile of silk fibroin consists of 17 amino acids, most of which are glycine (43%), alanine (30%) and serine (12%) [3,4].

The strength properties of silk have long been considered to be beyond the reach of synthetic fibres [5]. Silk thread with a cross-sectional area of 1 mm2 can bear a load of 45 kg. Silk is used for manufacturing parachutes, descent space vehicles, tyres of high-end racing bicycles and strings of musical instruments. Being a hypoallergenic material, silk is used not only in the textile industry, but also in the cosmetic industry. In addition, being biologically resistant, natural silk is used for surgical sutures and as a bioengineering material.

The largest producer of raw silk is China (50% of the world production), with India (15%), Uzbekistan (3%) and Brazil (2.5%) producing significantly less. The global volume of raw silk averages 80,000 tonnes per year and approximately 70% comes from China. The silk industry is supported by the government and is developing rapidly in Uzbekistan, Kazakhstan, Tajikistan and Azerbaijan. Some raw silk is produced in Europe; however, the demand there is still considerable. Consequently, the European market needs to import raw materials from outside the European Union [6].
Nevertheless, silk production has declined with the development of chemical fibres, despite having significant advantages as an excellent material for garment, medical and technical textiles. Silk has been partly replaced by viscose and polyesters in the textile industry and by polyamide and aramid fibres in the defence industry. The major sericultural productions are under threat of being closed down due to the industrialisation of Asia. However, silk continues to be one of the most important and expensive textile fibres. According to MegaResearch, the minimum average price for dry cocoons on the global market is USD 15 per kg. The increase in the raw silk price, which is mainly regulated by China, has a strong impact on the price of fabric and textile products.
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