Morphology and chemical structure of a wool fiber

Wool is an essential and novel animal fiber with unique properties such as crimp, insulation, flexibility, and biodegradability. The valuable features of wool fiber stem from its morphological and chemical structure, namely the cuticle (epicuticle, exocuticle, and endocuticle), cortex (orthocortex and paracortex), and amino acids. The cortex comprises nearly 80%–90% of the wool fiber and determines the main physical and chemical characteristics of the fiber such as resilience, crimp, and softness, while the medulla determines the luster of the wool fiber. The cuticle of the wool is responsible for protecting fiber against both chemical and mechanical damage and pathogen attack. Moreover, the chemical and physical features of wool fiber are affected by the genetic origin, physiological state, and nutrition of sheep. In particular, the cystine amino acid content in wool is changed by diet and nutrition. Therefore, in this chapter, a special emphasis on the morphological and chemical structure of the wool fiber is considered in detail by focusing on the cuticle, cortex, and medulla layers as well as existing bonds and amino acids.