Notes on the structure and characteristics of wool

Wool is a major animal fiber that grows from the skin of sheep as hair. Its manufacture as a textile fiber includes either in their natural state or after some sort of treatment that lend them for being used for spinning or felting. Wool fibers vary in length from V2 inch to 14 inches. The fiber is composed of three layers: (a) The cuticle or horny outer layer, (b) The cortex or the inner structure is made up of cortical cells, and (c) The medulla is the canal which gives the colour to the fiber. The quality of the wool fiber is determined by the breeding, climate, food, general care and health of the sheep. The chief wool producing countries are Argentina, Australia, The British Isles, India, South Africa and the United States.

Wool fibers of different qualities and lengths are prepared in a special manner to be woven into different kinds of fabrics. For clothing, besides felts, wool fibers are used for the manufacture of two principal classes of fabrics, namely 1. Worsted and 2. Woolens.

Structure

Wool has a rod-like structure with rough surface of overlapping horny scales. The fiber varies in length from two to eighteen inches and also varies greatly in fineness. The wool fibers are covered with minute scales, which cling to each other and enable the short fibers to be spun into thread.

Longitudinal view of fiber;

1. Rough surface

2. Crimp very evident

3. Scales present

4. More or less circular

5. Lack of lusture.

Characteristics

1. Composition:

The chief constituent of the fiber is a protein substance called ‘Keratin’. It is composed of basic elements in these approximate proportions: carbon 49 percent; oxygen 24 percent; nitrogen 16 percent; hydrogen 7 percent; sulphur 4 percent.

2. Strength:

Wool is the weakest of the natural textile fibers.

3. Elasticity:

It has got good elastic capacity depending upon the quality of wool. The fiber may be stretched from 25 to 30 percent of its natural length before breaking.

4. Resilience:

Wool fiber has a high degree of resilience hence, it wrinkles less than others.

5. Heat conductivity:

Wool fibers are non-conductors of heat, thus, excellent for winter clothing.

6. Absorbency:

Once the moisture seeps between the scales of the fiber, it will result in ready absorption. It can absorb about 20 percent of its weight in water without feeling damp.

7. Effect of Moisture and Friction:

Wool is softened by moisture, shrinking and felting occurs when the fabric is washed.

8. Reaction to Bleaches:

Wool is affected by bleaches; hence very little wool is bleached to pure white.

9. Shrinkage:

Shrinkage is greater in woolen fabrics.

10. Effect of Heat:

Wool becomes harsh at 212° Fahrenheit, scorches at 400o and eventually chars.

11. Effect of light:

Wool is weakened by prolonged exposure to sunlight.

12. Affinity for Dyes:

Wool fabrics dye well and evenly.

13. Reaction to Alkalis:

Wool is quickly damaged by strong alkalis.

14. Reaction to Acids:

Wool is damaged by hot sulphuric acid, but not affected by other acids, even when heated.

15. Resistance to perspiration:

Wool is weakened by perspiration.