Wool is a protein fiber and it is formed in the skin of sheep hence it is called animal fiber. It is produced from different types of sheep all over the world. Nowadays, it is a very important textile fiber in the textile sector.
Like all textile fibers, Wool has its own physical and chemical properties which are required to know for better processing in spinning, weaving, knitting, dyeing, printing as well as finishing. Here, I have written about physical and chemical properties of wool fiber.
Physical Properties of Wool Fiber:
The following are the physical properties of wool fibers. They are-
- Color: The color of wool fiber could be white, near white, brown, or black.
- Tensile Strength: The tensile strength of wool in dry conditions is 1 – 1.7 and 0.8 – 1.6 in wet conditions.
- Elongation at break: Standard elongation is 25 – 35% and 25 – 50% in wet conditions.
- Elastic Recovery: Good
- Specific Gravity: Specific gravity is 1.3 – 1.32.
- Moisture Regain (MR %): Standard moisture regain is 16 – 18%.
- Resiliency: Excellent.
- Luster: Luster of course fiber is higher than fine fiber.
- Effect of Heat: Heat affects the wool fiber greatly consequently wool becomes weak to heat. It softens when heated or treated with boiling water for a long time. At 1300C it decomposes and chars at 3000C. Wool does not continue to burn when it is removed from a flame.
- Effect of Sun Light: The main chemical components (keratin) of wool decomposes under the action of sunlight. The sulpher in wool is converted into H2SO4. The fibers become discolored and develop a harsh feel.
- Stored: No problem.
Chemical Properties of Wool Fiber:
Wool is a protein fiber and it has some chemical properties. The following are the chemical properties of wool fiber. They are-
- Effect of Acids: Wool is attacked by hot concentrated sulphuric acid and decomposes completely. It is in general resistant to mineral acids of all strengths even at high temperatures though nitric acids tend to cause damage by oxidation. Dilute acids are used for removing cotton from mixtures of two fibers; Sulphuric acid is used to remove vegetable matter in the carbonizing process.
- Effects of Alkalis: The chemical nature of wool keratin is such that it is particularly sensitive to alkaline substances. Wool will dissolve in caustic soda solutions that would have little effect on cotton. Strong alkaline affects wool fiber but weak alkaline does not affect wool.
- Effect of Organic Solvent: Wool does not affect by organic solvents.
- Effects of Insects: Wool is affected by insects.
- Effect of Micro Organism: It is affected by mildew if it remains wet for a long time.
- Dyeing ability: Wool fiber could be dyed with the basic dye, direct dye, and acid dye.
In sum, all the wool fiber is not the same in characteristics and it varies depending on the wool’s country of origin and sheep type.
So, choose your wool fiber after confirming the physical and chemical properties of wool fiber.