Tanning Technics Of Crocodylus Niloticus Bag Leather

Crocodile leather with unique pattern and rarity is regarded as one of luxury goods in high-grade leather products. However, in the domestic the breeding and tanning technics of crocodile both starts late, so the study on crocodile tanning technology has not been reported, which greatly limits the development of crocodile industry, new technology and resource utilization. Based on the understanding of present situation for crocodile leather in the domestic and foreign, this study aims to explore a set of tanning processes and uses them to treat the belly and back of crocodylus. According to the actual production evey process was optimized, as well as the physical and mechanical properties of leather were tested to make it satisfy the standard of bag leather.In this study, the trichrome-sudan IV staining method, aldehyde fuchshin staining method, scanning electron microscope and polarizing microscope were used to study the structural characteristics of the crocodylus niloticus raw materials. The results show that there is a obvious difference between the organizational structure of crocodylus niloticus and cattle, sheep, pig skin. The crocodylus niloticus organizational structure can divided into cuticle, epidermis, grain layer, reticular layer, fat layer and subcutaneous tissue layer, it does not contain hair, hair follicle. No suboriferous and blood vessels were found in the study, but in the reticular layer there is nerve fibers bundle which are composed of several nerve fibers and its diameter is between 50 to 100μm. The structure of the scale layer is compact, and the fiber bundle in grain layer and reticular layer is tight. Fiber bundle in grain layer is thin and its weaving is more random, while the fiber bundle in reticular layer is strong and its woven is very regular, and the angle between fiber bundles is about 90 degrees. The relatively thin and bent fiber bundles link two adjacent fibers layer, so that regular and tight network layer fiber system is ultimately formed.According to the characteristics of the organizational structure, the technology parameters of tanning and finishing section and the balance between every processes were ultimately determined. A set of tanning technics of crocodylus niloticus leather is obtained. The handle fleshing machine and shaving machine were used to flesh and the effect is good. The combination of multiple steps of degreasing and bating process, the technical difficulties of fat removal is solved. The combination method of "oxidative bleaching-reduction bleaching-bating-degreasing-oxidation bleaching-reduction bleaching" can completely destroy and remove the pigment in epidermal layer. The pure white acid skin with 83.5 degrees whiteness can be obtained after being salt washed in pickling. Compared with that of the limed skin, the whiteness of pickled skin increases more than 60%. At the same time, the aldehyde fuchshin staining method shows that the elastic fiber is destroyed in bating and bleaching process. The observation to wet blue by using scanning electron microscopy shows that the preparation and tanning process design is reasonable, and the interfibrillar substances has been completely removed. The Nile blue sulphate staining method shows that the fatliquor can uniformly penetrate into the skin.After tanning, the shrinkage temperature of crocodylus niloticus leather can reach to more than 110℃. The chromium element analysis to the cross section of wet blue leather indicates that chrome tanning agent can be uniformly distributed in the skin. The softness, elasticity, surface roughness and odor of the finished leather are better than those of commercially available samples. The crocodylus niloticus leather surface is smooth and the surface roughness is 2.20nm which is lower than that of cattle and sheep. In the tensile test of crocodylus niloticus leather the maximum stress is 628.8N, tensile strength is 64.83MPa, tear strength is 124.62N/mm, which are greater than that of cattle and sheep and the tearing strength is slightly larger than that of microfiber synthetic leather base.