10.3 Wool

Wool is the most important fiber and produced in the largest amount. Wool is the fur-like covering of sheep that are raised in many countries around the world. It is obtained by shearing the fibrous covering from the sheep.

Wool fibers are composed of protein in which the repeated unit is amino acid. The amino acids are linked to each other by the peptide bond （—CO—NH—） to form the protein polymer. Chemically，the most important component in wool is keratin that is a complex protein and composed of 16 to 18 different amino acids. Kertain is amphoteric in nature. So wool can be dyed with acid or reactive dyes.

Most wool fibers have a white or creamy color，although some breeds of sheep yield brown or black wool. Wool fibers have a tendency to return completely to their original shape after small deformations，which is great asset in apparel fabrics. The natural crimp in wool is of great importance，since it results in making a yarn fluffy，thereby trapping air in the interstices between the fibers. This trapping of air helps in forming an insulating layer，thus imparting the characteristic of warmth. Wool has several disadvantages: it is very sensitive to alkaline substance，it is readily attacked by moths and carpet beetles unless treated to resist them，it is difficult to bleach，and it felts easily.

According to their fineness and length wool can be divided into four types: fine wool，long wool，medium wool and carpet wool. Wool is used primarily in apparel and home furnishings.