Leather fibrous structure

Surface evaporation can be a limiting factor in the manufacture of many types of products. In the drying of paper, chrome leather, certain types of synthetic rubbers and similar materials, the sheets possess a finely fibrous structure which distributes the moisture through them by capillary action, thus securing very rapid diffusion of moisture from one point of the sheet to another. This means that it is almost impossible to remove moisture from the surface of the sheet without having it immediately replaced by capillary diffusion from the interior. The drying of sheetlike materials is essentially a process of surface evaporation. Note that with porous materials, evaporation may occur within the solid. In a porous material that is characterized by pores of diverse sizes, the movement of water may be controlled by capillarity, and not by concentration gradients. 

Leather is the material made from animal skin by the process of tanning, which entails chemically altering the composition of the skin so as to make it durable and resistant to decay. Leather is therefore not a protein but a protein derivative. Although the tanning process alters the composition of skin, leather retains the fibrous structure and utilitarian functionality that make skin suitable for multifarious applications. Shelter, clothing, and decorative objects made from leather are, unlike skin or hide, stable to physical, chemical, and biological decay under dry or wet conditions (O Flaherty et al. 1965 ... 

The first known structure of a fibrous protein was that of keratin. It comes in two forms, a- and -keratin, and their structures are what their designations imply. a-Keratin is the major protein of hair, nails, feathers, and skin, and is entirely a-helical, but it also has a higher order structure, with three strands of a-helix twisted around each other like strands of spaghetti. This results in a filament of increased stiffness and tensile strength. Leather is practically all a-keratin. /3-Keratin, on the other hand, is largely made up of antiparallel /3-pleated sheets. It is the principal protein of birds beaks and claws and of silk. 

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