October 2018 Abstracts

Lignin Based Colorant: Modified Black Liquor for Leather Surface Coating Application

by Pandian Balasubramanian, Sathya Ramalingam, Mohammed Abu Javid and Jonnalagadda Raghava Rao

Nowadays, much research is focused towards the development of a value-added products from industrial waste. In this concern, the preparation of pigment colorant with good covering power from the paper and pulp industry waste is less explored within the leather world. The paper and pulp industry generate huge quantity of waste, which is commercially known as black liquor. In order to prepare the pigments with good covering property the black liquor was acidified, and the insoluble organic part of black liquor was used for pigment application. In this work, the structural characterization of the prepared pigment products was analyzed by FT-IR, TGA, DSC, BET, SEM and DLS. Further sol-gel method was employed for the preparation of pigment formulation using the insoluble lignin obtained from the black liquor. The applicability of isolated insoluble as brown pigment was evaluated by using it as pigment for leather surface coating. The color characteristics of the pigment coated leather and checkered card were analyzed by using CIELAB color measurement. The results obtained clearly confirm that the insoluble lignin has potential application as a brown pigment in leather finishing application and is compatible with various auxiliaries employed in leather finishing. Utilization of the prepared brown pigment in leather finishing resulted in upgradation of finished leather through excellent surface covering and in addition, no overloading of grain was observed. Thus, this article provides an approach for converting waste black liquor from paper and pulp industry into a value-added material for pigment application.

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Effect of Cyclic Stress while Being Dried on the Mechanical Properties and Thermostability of Leathers

by Jinbao Huang, Jie Liu, Keyong Tang, Pengyuan Yang, Xialian Fan, Fang Wang, Jing Du and Cheng-Kung Liu

Various mechanical processes are usually applied in leather making and using, which inevitably affect the structure and properties of leathers, such as mechanical performance and hydrothermal stability. Cyclic stress is very common in leather making, which may cause different changes to leather, compared with constant stress. However, very few results have been reported regarding the influence of cyclic stress on leathers. In the present work, cyclic stresses were applied to leather in drying. The influences of cyclic stress on the mechanical properties, hydrothermal stability and dry heat resistance of leathers were investigated. Also, the cross section of leather was observed with SEM, and the changes of hydrogen bonds in collagen fibers were characterized and discussed with the results of FT-IR. It was indicated that stress in drying leads to orientation of collagen fibers and increased mechanical strength. A balance is set up between tensile strength and elongation at break of leathers with the action cyclic stress. Longer stretching leads to higher tensile strength and lower elongation at break. Meanwhile, stress in drying may prevent the formation of hydrogen bonds inside collagen fibers and change the weaving structure of collagen fibers, resulting in decreased hydrothermal stability of leathers. Cyclic stress may provide leathers with better dry heat resistance than constant stress. Also, a simplified model of collagen fibers movement was introduced, to establish a relationship between processing and properties of leathers from viewpoint of collagen fiber structure.

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Polyethylene Glycol as a Preservative for Pigskin and Its Interaction with Collagen

by Chunhua Wang, Huijuan Peng, Jun Sang and Wei Lin

Herein, an immersing method for the pigskin preservation by using polyethylene glycol (PEG) with different molecular weights (Mw = 200, 600, 6000) was developed and the in?uence of PEG on the conformation of type I collagen was investigated. Only PEG200 followed dehydration and rehydration patterns similar to that of salt curing and exhibits reasonably good preservative and bloodstains removal effects. Zeta potential analyses show that the collagen-PEG solutions have good dispersions stability. FT-IR and US-DSC results indicate that collagen triple helixes are kept integrated in the presence of PEG, and the highly hydrated feature of PEG helps to maintain the stability of the protein conformation. Atomic Force Microscope (AFM) images show that the collagen fibrils become more dispersed with the increasing Mw of PEG. The present work gives positive insight to partially replacing sodium chloride for the preservation of raw hide and skin, as well as the development of PEG-collagen biomaterials.

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Preservation of Bovine Hide using Less Salt with Low Concentration of Antiseptic, Part II: Impact of Developed Formulations on Leather Quality and the Environment

by Majher I. Sarker, Wilbert Long III, George J. Piazza, Nicholas P. Latona and Cheng-Kung Liu

The traditional method for bovine hide preservation requires approximately 40-50% sodium chloride on raw hide weight or 95% saturated brine solution in case of wet salting. This salt resides in wastewater after the soaking process and generates a huge environmental pollution in the form of total dissolved solids (TDS) and chlorides (Cl-) during leather processing. The current research has developed antiseptic based hide curing formulation using 45% saturated brine solution which reduces 50% salt usage in compare to traditional method. The newly developed formulations have been found more effective in limiting microbial growth on cured hide than the conventional method preserving the bovine hide for more than 30 days. In this study, post-leather analysis e.g. grain pattern, scanning electron microscopic images, mechanical properties and organoleptic evaluation reveal that the crust leather produced from alternatively cured hides are comparable to the control obtained from traditionally preserved hide. The efficacy of the alternative system is also assessed by monitoring the environmental impacts caused by the leather processing effluents on the basis of TDS and chloride content, total solids (TS), total aerobic bacterial counts in soaking liquor, Bio-Chemical oxygen demand (BOD) and Chemical oxygen demand (COD). The environmental advantages of the alternative hide curing method are determined particularly by 50% reduction of TDS and chloride content. Therefore, this new method is feasible and industrially preferable to the traditional hide curing process.

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