Proteinaceous fibre

Wools and other similar mammalian hairs are largely composed of keratin proteins. However, unlike the other natural proteinaceous fibre, silk, wool is cellular in nature the fibres consist of relatively hard, flattened, overlapping cuticle cells, which surround the central cortical cells in some fibres, these may in turn surround a hollow medulla (Figure 23). 

Animal fibres and filaments, proteinaceous substances taken from hair or fur (e.g., wool), down or feathers, and cocoon materials. 

Wool, hair and other animal fibres have a hierarchical microstruclure and no reliable model has been developed for prediction of the failure stress of lhe.se fibres which encompasses all the relevant length scales. Three models are available to explain the tensile properties of a-keratin fibres all deal with a system of parallel microfibrils embedded in a proteinaceous matrix at a scale of 10 nm. In 1959, Feughelman laid the foundations of stmctural interpretation of the stress-strain curve with his two-phase model of microfibrils imbedded in a matrix, a model that was improved in 1994 (Feughelman, 1994). In the same year, Wortmann and Zahn (1994) proposed another version of the microfibril model. The third model, the Chapman and Hearle model (Hearle, 1967 Chapman, 1969) is based on the mechanics of stress transfer in a composite system consisting of microfibrils, which undergo an a p transition, in parallel with an elastomeric amorphous matrix. The Wortmann and Zahn model does not explicitly mention breakage of fibres, but it is implicit that this must be triggered... 

Like all polymeric structures, keratin fibres consist of long, tightly bound molecular chains held together in many different ways from covalent bonds to weaker interactions such as hydrogen bonds, Coloumbic interactions, van der Walls interactions and, when water is present, hydrophobic bonds. Hair reactivity is complex and depends not only on the presence of reactive groups in the fibre, but also on their availability. The latter is significantly affected by fibre morphology and molecular structure [2]. Hair is mostly proteinaceous in nature, while structural hpids and other materials represent only a minor fraction of its constituents. 

Hair is complex multicomponent fibre with both hydrophilic and hydrophobic properties. It consists of 65-95% by weight of protein and up to 32% water, lipids, pigments and trace elements. The proteins are made of structured hard a-keratin embedded in an amorphous, proteinaceous matrix. Human hair is a modified epidermal structure, originating from small sacs called follicles that are located at the... 

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