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Purification of Protein Hydrolyzate Recovered from Chrome Tanned Leather Shavings Waste 
by R. Chaudhary and A. Pati
Volume: 111      Number: 1     Page: 10-16     Year: 2016
Environmental constraints have become key issue for sustenance of industries worldwide. Waste management approach insists tanners look for an innovative way of creating wealth from waste. Chrome tanned leather shavings (CTLS) are generated in leather making process and requires a major attention on disposal. There are developed processes for recovery of protein and chromium from CTLS through acid/ alkaline/enzymatic hydrolysis process. However, the derived protein hydrolyzate contains impurities such as chromium and neutral salts. In this study, an attempt has been made to purify protein hydrolyzate through protein precipitation process. Protein purification studies have been carried out to study the influence of factors such as salt concentrations, pH and time. The purity of protein hydrolyzate before and after purification process is found to be 95 and 99.4% respectively. This is further evidenced from amino acid analysis of protein hydrolyzate before and after purification. The recovered protein hydrolyzate could be used in a wide range of products such as fertilizer, animal feed and bio-composites.
Elimination of Chromium Oxidation for Effective Chromic Oxide Detections 
by M. Hooks, M. Hayes and R. Maendle
Volume: 110      Number: 12     Page: 420-424     Year: 2015
Inductively Coupled Plasma Optical Emission Spectrophotometer (ICP-OES) was used to accurately determine the Chromic Oxide content in 90 total Wet Blue, Crust, and Finished Leather samples. Accuracy was verified on each sample by testing retained composite material using ASTM D2807 Perchloric Digestion / Sodium Thiosulfate Titration Method. The ICP-OES Method correlated to ASTM D2807 with less than 2% deviation from the averaged mean value and less than 3% deviation from the averaged standard deviation value. The Chromic Oxide mean values for ASTM D2807 and ICP-OES were 3.11 ± 0.70% and 3.17 ± 0.68% respectively. The new method maintains a highly consistent statistical capability with Cpk at 2.15 vs. 2.17. Oxidation of chromium in leather samples is not required for chromic oxide detection. Perchloric acid more than doubles the required consumables cost, test time and hazard required to validate chromic oxide levels in leather materials. The ICP-OES method eliminates the crystal formation explosion hazard and chlorinated waste environmental hazards associated with Perchloric acid. Replacing ASTM D2807 with the proposed method by tannery validation laboratories is cheaper, faster, safer and more environmentally sustainable than titration by our classic technique.
Correlation of Visual and Instrumental Color Measurements to Establish Color Tolerance Using Regression Analysis 
by M. Jawahar, S. Kanth, R. Venba and N.K. Chandra Babu
Volume: 110      Number: 12     Page: 409-419     Year: 2015
Color is one of the important parameter considered in the determination of quality for fashion materials like leather. The color variation in each piece of leather sample in a batch should be within the acceptable range. Visual assessment is currently used in leather industry for quality control and color sorting. The current method used is subjective and often leads to disagreement between buyer and seller. Color measurement using reflectance spectrophotometer evaluates color consistently and is an objective assessment system. However, there is always an apprehension that the instrumental color assortment may not agree with the human perception of color difference. Hence, in the present investigation, an attempt was made to screen four color difference formulae, viz., CIELAB76, CMC (2:1), CIE94 and CIE2000 for their suitability in obtaining pass/fail decisions, which would be in conformity with that of the average human observer. Regression analysis was performed to find a correlation between visual and instrumental color assessments and the results indicate that CM (2:1) formula may be the most suited for the purpose. A detailed analysis of visual and instrumental color values revealed visual non uniformity towards sensitivity to hue, chroma and lightness. This difference in sensitivity was also taken into consideration in instrumental color sorting and pass/fail tolerance was established that led to closer conformity between visual and instrumental methods.
Preparation and Characterization of Nano-reinforced Leather Waste Fiber-epoxy Nano Composite 
by V. Sivakumar, T. Swathi, R. Mohan and A. Mandal
Volume: 110      Number: 12     Page: 401-408     Year: 2015
Significant quantities of leather waste fibers are generated from the leather industry. Confinement and utilization of leather waste fibers by converting them in to useful materials such as nano-composites is desirable. Earlier studies on making composites from leather waste fibers suffer from strength properties for different applications. In this paper, preparation and characterization of nano composite from leather fiber–epoxy polymer reinforced with nano TiO2 has been studied and reported for the first time. Physical testing of these nano composites shows better strength and other properties for improved performance as versatile material. TGA and DSC studies revealed better thermal stability (up to 330°C) for these nano composites. FTIR analysis shows possible chemical interaction between epoxy polymer and leather fiber. Better solvent resistant property was also noticed for the nano-composites prepared. SEM analysis indicates uniform nano-composite structure and distribution of nano TiO2 in the matrix. The present approach not only offers a solution to the disposal problem regarding leather solid wastes like buffing dusts, but also offers a versatile nano composite material.
Biopolymers Produced from Gelatin and Chitosan Using Polyphenols 
by M. Taylor, L. Bumanlag, E. Brown and C.-K. Liu
Volume: 110      Number: 12     Page: 392-400     Year: 2015
Chitin, and its derivative chitosan, is an abundant waste product derived from crustaceans (e.g. crab). It has unique properties, which enable its use in, but not limited to, cosmetic, medical and food applications. Chitosan has recently been studied, in conjunction with other waste carbohydrates and proteins, for the purpose of making biopolymer products with unique functional properties. Furthermore use of renewable polyphenols to assist in these reactions is a topic of growing interest. In prior research, we investigated the use of polyphenols, specifically gallic acid and the vegetable tannins quebracho and tara, to modify gelatin. We improved the physical properties of gelatin and were able to demonstrate that these products could be used effectively as fillers. At present, gelatin is scarce and becoming increasingly more expensive so we produced biopolymers from modification of gelatin and whey using the vegetable tannin tara, and made products to augment the gelatin; we further demonstrated that the resulting product could be used as a filler for leather. This present study investigated the preparation of a biopolymer using gelatin and chitosan, modified with the vegetable tannin tara, to make products that could be used either in leather making process, e.g. as fillers or coatings or could have other potential uses such as in film-making or as flocculants. Optimal conditions necessary for polyphenols to react with gelatin and chitosan were determined and physical properties showed that unique products were produced. The gels were examined for thermal stability and for fluorescence. We thus demonstrated that gelatin/chitosan/tara products are feasible and that gelatin products could be supplemented using an inexpensive abundant waste product, chitosan.
Inhibitory Effect of Protein Filling Agent from Bovine Hair on the Oxidation of Cr(III) 
by Yue Yu, Weicai Zeng, Ya-nan Wang and Bi Shi
Volume: 110      Number: 12     Page: 385-391     Year: 2015
In consideration of the fact that the hydrolysate of hair contains antioxidant and free radical scavenging groups, the inhibitory effect of protein filling agent prepared from bovine hair (HPFA) on the oxidation of Cr(III) was investigated. The results demonstrated that HPFA possessed remarkable reducing ability to transfer Cr(VI) to Cr(III) in solution when pH was lower than 6.0. The reduction reaction was enhanced with rise of temperature, extension of reaction time and increase of HPFA dosage. Meanwhile, the HPFA also presented a high activity to inhibit the oxidation of Cr(III) in chrome liquor in the presence of unsaturated fish oil fatliquor. More interestingly, the HPFA achieved satisfactory inhibitory effect on Cr(III) oxidation in leather in the temperature range from 20oC to 100oC. Its inhibitory activity was much higher than that of commercial protein filling agent made from collagen hydrolysate. All the results suggested that bovine hair could be used as a potential resource for preparing protein filling agent with both filling and Cr(III) oxidation inhibiting properties.
Effect of Finishing Auxiliaries on Permeability of Leathers 
by M. Sthish, Z. Azhar, N. Fathima and J. Raghava Rao
Volume: 110      Number: 11     Page: 372-378     Year: 2015
The unique fibrous arrangement and architectural marvel of collagen in skin matrix are the basis for various physical properties of leather. Air permeability is one of the unique features of skin, which makes the leather matrix superior to synthetic materials. In leather manufacturing finishing process determines the air permeability of the final leather. Therefore, knowledge of the impact of different finishing auxiliaries on the permeability of leather may helpful in selecting an appropriate finishing system for a particular type of leather. In this work, an attempt has been made to analyze the effect of various auxiliaries used in protein, acrylic and polyurethane (PU) based finish coatings on the air permeability of leather. Capillary flow porometer was used to monitor the air permeability (Flow rate cc/sec) at different pressures (psi). The results show that the effect of wax/filler/slip and dye solution on air permeability reduction is low when compared to pigment and binder. In protein and PU finishes, the binder alone and season (combination of all finishing auxiliaries like pigment, binder, and other auxiliaries) has a strong influence on permeability reduction whereas in case of an acrylic based finish, the pigment and binder plays an important role in permeability reduction. Leather coated solely with protein binder shows minimal permeability reduction than compared to leather coated with acrylic or polyurethane binders, whereas in season, acrylic based finishing has a lower permeability profile than that of protein and PU. In that case the permeability profile of protein and PU season coated leathers is almost similar.
Chrome-Reduced Combination Tanning for Cleaner Dyed Sheep Fur Processing 
by Wei Ding, Yihan Cheng, Ya-nan Wang and Bi Shi
Volume: 110      Number: 11     Page: 363-371     Year: 2015
Chrome tanning is essential for conventional processing of dyed sheep fur as it can provide fur with high hydrothermal stability suitable for dyeing of wool at a temperature around 70°C. However, a long float length and a big offer of chrome tanning agent (16 g/L) are required for the tanning process, which lead to poor uptake of chrome and excessive discharge of chrome in wastewater. In this study, reduction of chrome offer in dyed sheep fur production was investigated to develop a cleaner tanning technology. It was found that the even distribution of chrome and satisfactory dispersion of fur collagen matrix were achieved even though chrome tanning agent offer was reduced to 2 g/L and 4 g/L. But the shrinkage temperature of the furs was only 79°C and 85°C, respectively, which resulted in a sharp area shrink of fur in following high temperature dyeing. In the combination tannage using 10 g/L amphoteric organic tanning agent (TWT) and 2 g/L or 4 g/L chrome tanning agent, the shrinkage temperature of fur was higher than 90°C accompanied by a higher utilization of chrome. These combination tanned furs were capable of enduring dyeing process at 68°C for 8 h, and presented a high uptake of post tanning chemicals because they had an isoelectric point close to that of chrome tanned fur. More importantly, the physical properties of the combination tanned dyed furs were comparable to the dyed fur made by conventional chrome tanning using 16 g/L chrome tanning agent.
Fatliquor Effects on Collagen Fibril Orientation and D-spacing in Leather during Tensile Strain 
by K. Sizeland, G. Holmes, R. Edmonds, N. Kirby, A. Hawley, S. Mudie and R. Haverkamp
Volume: 110      Number: 11     Page: 355-362     Year: 2015
Strength is a very important property of leather and is known to depend on the arrangement of the collagen fibrils within the material. The addition of fatliquor (penetrating oils) is an essential part of the manufacture of leather and enhances the strength and feel of leather. However, the mechanism by which fatliquor leads to increased strength is not understood. Here we use synchrotron based small angle X-ray scattering (SAXS) to monitor the collagen fibril rearrangement and internal strain of leather during tension. Differences in internal structural changes under strain with varying levels of fatliquor are investigated. It is found that when a strain of up to 40-70% was applied to leather, the orientation index (OI) of the collagen fibrils changed up to 21.8% and the d-spacing changed by up to 1.8% with no consistent differences at different levels of fatliquor. The extensibility of leather increases by 11.3% with as little as 2% fatliquor addition and the elastic modulus decreases with fatliquor addition but not in proportion to the amount of fatliquor. This change in extensibility is not reflected in differences in OI or d-spacing changes during strain. As reported previously, the fatliquor modifies the d-spacing of collagen. While fatliquor is traditionally considered to lubricate the fibers in leather, here the evidence suggests that this does not occur at the level of collagen fibrils. This provides an insight in the action of fatliquor in leather manufacture.
Chemistry of Syntans and Their Influence on Leather Quality 
by J. Ammenn, C. Huebsche, E. Schilling and B. Dannheim
Volume: 110      Number: 11     Page: 349-354     Year: 2015
The first syntan, Neradol D, was a condensate of phenolsulfonic acid and formaldehyde. While this chemistry allowed more efficient use of vegetable tannins, it was not advantageous to be applied on leather alone and has to be considered an auxiliary. Incorporating urea into the phenolsulfonic acid - formaldehyde condensation established a second generation of syntans with significantly improved lightfastness. Replacement syntans were developed to substitute vegetable tannins, giving rise to leathers of good softness and fullness. The formaldehyde condensation of dihydroxy diphenyl sulfone (sulfone) can be considered a further development of the replacement syntans with lower residual monomers. In order to compare these four generations of syntans, poly-condensates of a comparable molecular size had to be synthesized. These tested in hydrothermic denaturation of skin powder and applied in sole tanning and re tanning. The resulting leathers were compared in various aspects of performance including shrinkage temperature, softness, fullness, light fastness, and rest monomers.