Effect of Tanning on the Contents of Different Types of Water in Skin Collagen

The contents of free water and bound water in inorganic Cr(Ⅲ), TWLZ and organic TWS tanned leathers were studied by centrifugal dehydration-rehydration method to explore the effect of tanning on the structure of skin collagen fibers. Results showed that both Cr(Ⅲ) and TWS crosslinking increased the free water in the skin fibers by more than 60%, while TWLZ crosslinking decreased it by 8%, reflecting the difference in the dispersion degree of the skin fibers by the tanning agents. Bound water is divided into side-chain and main-chain bound water. TWS tanning decreased the main-chain bound water of collagen by nearly 10%, while the main-chain bound water of two kinds of inorganic tanned collagen increased by more than 10%. The double water bridge of inorganic tanned collagen increased by 24%, indicating the conformational change of collagen. Taking the ratio of equilibrium rehydration content/main-chain bound water as the parameter, the lower the value indicated the higher thermal stability of crust. These results provide a theoretical basis for understanding the relationship between the structure and properties of complex skin fibers.