Wool Fiber | Properties | Applications


Wool Fiber properties and Their applications


Wool Fiber
Yashashree Ingle
Department of Textile Technology
Veermata Jijabai Technological Institute Mumbai, India

Wool Fiber:
Wool fiber is a natural animal fiber which is derived from the hair grown on sheep; it is composed of a protein substance called Keratin which is the major component of wool fiber. Wool is also composed of hydrogen, nitrogen and carbon, wool is the only natural fiber which also consists of sulfur in addition. Wool gives a spongy feel and acts as a good insulation material due to the presence of curls or crimps in its structure which is beneficial to the user.
It is a protein fiber basically consisting of cylindrical strands of alpha-keratin covered by minute overlapping scales which is much valued as a textile fiber. It is obtained from the fleece (dense warm coat of the sheep) of range of certain fury animals.
Wool has various properties well suited for textile production such as
  • Easy process ability.
  • Excellent dye ability and superior color fastness (absorbency).
  • Resilience (retaining its shape).

Wool’s natural crimps allow the fibers to hold together and create a very strong yarn, also creating air pockets that act as a natural layer of insulation and making it very desirable to wear in cooler weather. Owing to these properties wool finds its way in various wide ranges of applications, which apparently boosted up sheep husbandry as an important pastoral activity.

Types of Wool Fibers:
Different breeds of sheep bore different types of wool. There are various types of wool out of which the best quality of wool is obtained from merino sheep. Varieties of animals like: 
  • Angora wool (Rabbit)
  • Cashmere wool (Goat)
  • Chiengorawool (Dog)
  • Llama wool (Llama)
  • Lopi (Icelandic sheep)
  • Mohair (Angora goat)
  • Pashmina (Pashmina goat the Changthangior Kashmir Pashmina goat)
  • Shahtoosh (Tibetan Antelope) is domesticated in order to obtain wool from them.
  • Out of which angora wool, mohair and cashmere wool are of sheer prominence.

Growth and Harvesting of Wool fiber:
Wool is amongst the oldest fibers known to humans and it was one of the first fibers to be spun into the yarn and then woven into fabric. Wool not only comes from sheep, but also from different animals such as goats, camels, alpacas etc. The major producers of wool are China, Australia, Eastern Europe and New Zealand.

Harvesting of the Wool involves following procedure:
The process of removing hair from the sheep is termed as shearing. A sharing specialist can sheer 200 sheep a day. A female sheep can produce 20 pounds of wool where as a mal sheep can produce 15 pounds of wool. The sheared wool is called as the raw wool and the very first step is cleaning of the wool to get rid of all the impurities, dust and other unwanted materials.
The second step is carding, this involves brushing the wool which makes the wool fibers straight, in olden days it was carried out by hands, but now due to development of machines. The machine involves passing of wool through a series of rollers where the carded fibers are gently scraped into strands called rovings. The roving is spun into yarn that is then woven into cloth.
Fleece is a ball of wool taken from a single animal in a shearing. But not all wool is equal – even when it comes from the same animal. The highest quality wool comes from the sides, shoulders, and back. The lowest quality comes from the lower legs.

Grading of Wool Fibers:
Wool is graded for fineness and length. The length varies from place to place on the animal, but it mostly varies amongst sheep breeds. Australian Merino wool is 3-5 inches long. Breeds found in Texas and California produce fibres 2.5 inches long. Wool from other breeds and other animals may be as long as 15 inches.
Physical Properties of Wool Fiber:
  • Fiber Diameter: Fine Merino wools is 18 –21 microns, super-fine wool is 14 –17 microns, crossbred wools (for carpets) is 30 –38 microns.
  • Length: Staple length fiber governed by inheritance and environmental conditions. Staple length lower than the mean fiber length because of  crimp.
  • Specific Gravity: for dry wool is 1.304
  • Luster:  It is dependent on structure of fiber surface and size and straightness of fibers.
  • Moisture Relations: Hygroscopic in nature, absorbs moisture from moist atmosphere. Moisture content of wool is about 12-13 %
  • Frictional Properties: Greater when rubbed against the scales.

Chemical Properties of Wool Fibers:
  • Effect of water and steam: Swells when placed in water, In Cold water swells about 10% in diameter, In Boiling water has adverse effects on mechanical properties.
  • Effect of Heat: Varies according to type of fleece, coarse open fleece has maximum exposure to heat; exposure to radiation causes weathering of fiber.
  • Effect of heat and Alkalis:  Dilute acids have little effect but either hot or concentrated acids weaken or dissolve the wool fibres. Alkalis tend to make while wool yellowish, strong solutions of sodium carbonate when heated destroys the fibre sodium hydroxide is highly injurious to the wool.

Production of wool in India
The woolen industry in the country is small in size and widely scattered. It is basically located in the States of Punjab, Haryana, Rajasthan, Maharashtra and Gujarat. 40% of the woolen units are located in Punjab, 27% in Haryana, 10% in Rajasthan, while the rest of the States account for the remaining 23 % of the units.

Application of Wool Fiber:
  • Being easy to clean and lasts long, preferred for clothing.
  • The most important use of wool is for apparel coats, jackets, suits, dresses, skirts, slacks made from woven fabrics of varying weights and knitted fabrics.
  • Acts as insulator, hence used for bedding and blankets.
  • Used to line boxes, shelf linings and surfaces required to be softer.
  • In the home furnishing area, the major use of wool is in carpets and rugs where wool is used more, cover to the carpets and warm in the rugs.

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