Text and Science Care

Textile Science and Care 3(2+1)

Lesson 05 : Silk Fibre

Properties of Silk

Physical properties
Lustre: Silk is a highly lustrous fibre among all natural fibres. Wild silk is not as lustrous as cultivated silk.
Structure: Silk is a transparent, lustrous filament with slightly irregular diameter. In cross section the filament shows wedge shape. The silk that comes from each cocoon has two filaments held with their wedge shape together with sericin. Silk is the only natural filament fibre. Silk fibre is estimated o be 70-75% crystalline and correspondingly 30-25 % amorphous.
Strength: silk fibre has the highest tenacity of the protein fibres and also strongest of all natural fibres. When compared to synthetic fibres, its tenacity may fall in mid range. The degree of fibre orientation and hydrogen bonding accounts for its good strength. Highly durable fabrics can be made from silk at lower weight also. The durability of fabric depends on the use of ply/double yarns and compactness of construction.
Elasticity: Silk has medium elongation at break. At 2 % elongation the elastic recovery of silk is 90 %. The elasticity of silk in fabric form may vary based on the type of the yarn used and the construction of the fabric.
Resiliency: The resiliency of silk may be graded as medium range. But silk fabrics retain their shape and resist winkling. Delayed recovery is observed. Leaving wrinkled silk fabrics overnight will help in recovering the shape of silk. Heavily weighted fabrics wrinkle more and show decreased resilience.
Abrasion resistance: Silk has moderate abrasion resistance. Its smooth surface and wedge shape helps in resisting the abrasion.
Drapability: Silk is one of the best fabrics that possess excellent drapability. Its use for rich draperies speaks about its drape. The suppleness and pliability aided by its resilience and elasticity accounts for its drapability.
Density: Silk fibre has a specific gravity or density of 1.64 gm/cubic centimeter. It is possible to make light weight fabrics without sacrificing the strength.
Absorbency: Silk fabric can absorb water up to 1/3rd its weight without feeling wet to the touch. This property enables silk to take up dyes very well during dyeing and printing..
Dimensional stability: Silk fabrics retain their shape very well as the shrinkage in washing is found to be minimum. Crepe fabrics shrink more during laundering but can be restored back with careful steaming.