January 2018 Abstracts

Mapping Tear Strength and Collagen Fibril Orientation in Bovine, Ovine and Cervine Hides and Skins

by S. J. Kelly, R. L. Edmonds, S. Cooper, K.H. Sizeland, H.C. Wells, T. Ryan, N. Kirby, A. Hawley, S. Mudie and R. G. Haverkamp

Leather is a natural and variable material. The variation in strength has previously been shown to be due in part to the collagen fibril orientation. However, the extent of variation in strength and orientation over a skin/hide is not well established. Synchrotron small angle X-ray scattering is used to measure collagen fibril orientation (O) and orientation index (OI). Tear strength is measured in two orthogonal directions across ovine and cervine skins and bovine hides. Average normalized strengths varied between species with cervine leathers having the greatest overall strength followed by bovine then ovine leathers. Ovine had the greatest variability in strength across the skin. There were no obvious regions of generally stronger or weaker skin within individual skins or hides. The predominant collagen fibril direction was perpendicular to the backbone of all species, with the greatest perpendicular alignment in ovine followed by cervine. Collagen fibril orientation in leathers made from of ovine, bovine and cervine skins have been analyzed quantitatively and in detail. Findings suggest an unpredictable variability in collagen arrangements within each species but a notable difference in strength between species.

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Preservation of Bovine Hide using Less Salt with Low Concentration of Antiseptic,
Part I: Effectiveness of Developed Formulations

by Majher I. Sarker, Wilbert Long III and Cheng-Kung Liu

Bovine raw hides are commercially cured either with high salt concentration of about half the weight of actual hide or 95% saturated brine solution. This conventional technique is very popular due to the availability of common salt (sodium chloride) and its cost-effective procedure but it generates a huge pollution problem increasing salinity. As a result, an alternative method of using less or no salt for hide preservation needs to be developed. For the preservation of hide it is essential to arrest microbial attack on hide as the main constituent of raw hide is protein which is very susceptible for bacterial degradation. Such bacterial degradation leads to the putrefaction of raw hide before converting them into leather. Agricultural Research Services scientists at Wyndmoor, Pennsylvania, have developed antiseptic based formulations for hide curing where only 45% saturated brine solution is used. The newly developed formulations have been found more effective in limiting microbial growth for a longer time on cured skin than the regular brine process and thus preserve hides for more than 30 days. In-process analysis of cured hides during storage period reveals the compatibility of the alternative curing process in comparison to the traditional method. Therefore, this new development will not only preserve hide through better protection from microorganisms but also offers improved conservation of the environment.

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A Cleaner Deliming Process Using Sodium Gluconate for Reduction in Nitrogen Pollution in Leather Manufacture

by Yunhang Zeng, Ya-nan Wang, Ying Song, Jianfei Zhou and Bi Shi

Ammonium salts used in deliming process are the main source of high ammonia nitrogen (NH3-N) concentration in tannery wastewater. To reduce nitrogen pollution in leather manufacture without sacrificing quality of resultant leathers, a cleaner deliming agent prepared by mixing sodium gluconate (60 wt.%), citric acid (15 wt.%) and ammonium sulfate (25 wt.%) together was employed for deliming limed cattle hide pelt. The results indicated that this cleaner deliming agent penetrated the whole pelt very quickly and successfully formed a buffer system of pH 8-9 with the alkali from liming, which prevented acid swelling and damage to the fiber network of pelt. The delimed pelt had a cleaner grain surface with a higher extent of calcium removal than the conventional ammonium delimed pelt. The concentrations of NH3-N and total nitrogen (TN) in the cleaner deliming effluent were dramatically reduced by 86% and 79%, respectively. Moreover, the cleaner deliming scarcely affected subsequent bating process with trypsin.

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Improvement in Tanning Properties of Natural Leather Through Surface Modification Assisted by CO2 Low-Temperature Plasma

by Fangming Liu, Ting Su, Yuanping Jiang, Wenlan Xu, Zhengjun Li and Lixin Li

Low temperature plasma (LTP) technology is a green, solvent-free, clean, efficient environment-friendly surface treatment technology. The pioneering works were carried out by applying LTP to surface modification of natural leather in order to improve the chrome tanning exhaustion rate. The effects of different treatment time on tanning exhaustion rate, micro-structure, chemical compositions, mechanical and organoleptic properties of leather were studied. The optimal CO2 plasma treatment time is about 10 min, at which the chrome tanning exhaustion rate increases from 78.49% to 91.82% compared with untreated leather. The SEM results show that some micro-pores, fissures, deep ravines and filamentous fibers can be observed due to the surface etching effect. From the XPS analysis, compared with the untreated leather, the O1s concentration and the O1s/C1s ratio of the 10min LTP modified leather both increase from 18.75% to 28.85% and from 0.258 to 0.479, respectively. The results show that appropriate LTP process can effectively improve the chrome tanning exhaustion rate, which reduces the emission of heavy metal chromium in waste liquor and also has a good synergistic effect on improving the comprehensive performance of leather such as hydrothermal stability, physical-mechanical and organoleptic properties. The LTP modification technology may be a new potential method for cleaner high-exhaustion chrome tanning technology.

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