Wool Fibre
Wool is possibly the oldest fibre known to humans. It was one of the first fibers to be spun into yarn and woven into the fabric. Wool is the natural highly crimped textile fibre obtained from different varieties of sheep. Major varieties of wool come from merino, alpaca, camel, goats, and other breeds of sheep. Wool is composed of a very complicated protein known as keratin along with many active side groups. Wool fibres of 5-12 cm in length are preferred for wool textile manufacture.
WOOL PRODUCING COUNTRY
Australia
Argentina
China
New Zealand
Pakistan
PRODUCTION PROCESS OF WOOL FIBRE
1. Shearing: Sheep shearing is the process by which the woolen fleece of a sheep is cut off. Another way, the haircutting process of sheep is called shearing. It is normally done in hot weather. The sheep are shorn using electric shears/trimmers. Care must be taken to avoid injuries and to ensure that the coat is separated.
2. Sorting : A process by which fleece or skin wool is divided into various qualities is called sortingof wool. In sorting, the wool is broken up into sections of different fibres quality, from different parts of the body. The best quality of wool comes from the shoulders and sides of the sheep and is used for clothing. The lesser quality comes from lower legs and is used to make rugs (Blanket).
3. Grading :
After shearing & sorting, the fleece is graded according to fineness, crimp, length,impurities and color,
4. Scouring:
Wool taken directly from the sheep is called raw or grease wool. Raw wool can contain25–70% by mass of impurities. These consist of wool grease, suint, dirt (a substance, suchas mud or dust), and vegetable matter, such as burrs and seeds.
5. Drying & Baling :The wet-scoured wool is then dried. A wool bale is a standard-sized and weighted pack of graded and sorted wool compressed by mechanical means of a wool press. Each bale contains 330 Kg of graded wool.
CARBONIZING OF WOOL FIBRE
Wool clips are contaminated with excessive vegetable matter, such as burrs, seed, and grass are carbonized using aqueous 6% sulfuric acid treatment, which is followed by heating (950C to 1200C) to convert the defective material into carbon. The acid medium is then neutralized and the wool is re-scoured to complete the process. Carbonizing occurs if wool fiber contains a high percentage of vegetable matter (around 2-3%). It is expensive, often resulting in shorter and weaker wool fibre.
PHYSICAL PROPERTIES OF WOOL FIBRE
Length: The length of merino wool is varied from 60 to 100 mm.
Fineness: The fineness of merino wool fibre varies from 15-25 µm.
Crimp: Crimp is the basic structural property of wool fibre. There are an average of 30 crimp/ inch in the Merino wool fire .
Tenacity: Tenacity of wool is 1.35 g/d
Specific gravity: The specific gravity of wool is 1.32.
Elongation: Wool has an elongation at a break of 25-30% under standard conditions.
Elastic property: Wool fibres are highly elastic and resilient. The elastic recovery of wool fibres is 65%for 20% extension and almost 100% for a short extension.
Moisture Regain: Moisture regain of wool fibre is 16%.Effect of heat: On heating, wool fibre degrades and yellows above 1500c and chars at 3000c.
WOOLLEN AND WORSTED YARNS
Woollen
yarns are thick and full; the fibres are held loosely and subjected to only a limited twist during spinning. In woolen yarns, the random arrangement of the fibres results in bulky yarns with a fuzzy surface.
Uses
Sweater
Carpets
Worsted yarns are finer, smoother, and firmer than woolen yarn. In worsted yarn, the fibres are lying more parallel and more tightly twisted, producing a thinner yarn with a smoother surface.
Uses
Suits
Dresses
Gabardines
FIBRE IDENTIFICATION
Microscopic test
:1. Longitudinal
Cylindrical, irregular, rough surface, scale-like structure, and dark medulla may appear on coarse wool fibres.
2. Cross-sectional
Nearly round or circular. It shows three layers-epidermis, cortex, and the medulla.
Chemical test:
Wool fibre dissolves in concentrated sodium hydroxide and Sodium Hydrochloride and slowly dissolves in Nitric acid (70%).
Conclusion
Wool is extensively used in textile applications where comfort and aesthetic properties are important. It is used in men’s and women’s apparel, outerwear cold weather clothing, suits, blankets, felts, and carpeting.
AUTHOR
Md.Al-Mostakim
Department of Textile Engineering
Ahsanullah University of Science and Technology.