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Characterization of Mechanical Properties of Leather with Airborne Ultrasonics 
by C.-K. Liu, N. Latona, M. Taylor, C. Eble and M. Aldema-Ramos
Volume: 110      Number: 3     Page: 88-93     Year: 2015
A nondestructive method to accurately evaluate the quality of hides and leather is urgently needed by leather and hide industries. Effects have been made to develop airborne ultrasonic (AU) testing method using non-contact transducers to evaluate the quality of hides and leather. We previously reported the research results demonstrating the AU technology for revealing defects in hides and leather that were difficult to be found during visual inspection. Recently new research was carried out to develop AU methods to nondestructively characterize the mechanical properties of leather. Observations showed a strong correlation between the mechanical properties of leather and the corresponding AU parameters based on the distribution of the transmission time (time of flight) through leather. We also used this nondestructive method to characterize the grain break of leather. Results showed the difference in grain break could be determined from the AU parameters collected from moving the AU sensors over a leather sample. Observations showed the poorer the grain break, the higher the time of flight distribution. In short, this study demonstrated that the tensile strength, stiffness, toughness and grain break could be nondestructively determined by AU.
 
 
Studies on Tara-phosphonium Combination Tannage: Approach Towards a Metal Free Eco-benign Tanning System 
by R. Aravindhan, B. Madhan and J. Raghava Rao
Volume: 110      Number: 3     Page: 80-87     Year: 2015
One of the important criteria determining the sustainability of an industrial activity is the ecological acceptability of the processing methods. Tanners throughout the world are looking for alternative eco friendly tanning systems. In the present work, metal free tanning system using a combination of Tetrakis Hydroxymethyl Phosphonium Sulphate (THPS) and Tara has been developed. This combination tanning is expected to be an effective eco-friendly mineral free tanning. The shrinkage temperature of the leathers obtained is 88oC. The tanning system is versatile in terms of processing both upper and garment leathers. The physical strength characteristics and organoleptic properties of the leathers obtained are comparable to that of chrome tanned leather. Environmental impact assessment shows that there is reduction in total solids when compared to control chrome tanning. Tara as a combination tanning agent not only improves the leather properties but also can act as a scavenger of free formaldehyde present in THPS tanned leather.
 
 
Kinetics of Inhibition of Type I Collagenase by Dialdehyde Cellulose in Stabilization of Type I Collagen 
by G. Jayakumar, N. Usharani, A. Yasothai, S. Kanth and J. Raghava Rao
Volume: 110      Number: 3     Page: 72-79     Year: 2015
Collagen is one of the widely studied biomaterial for various industrial applications. However, search of eco-friendly and biocompatible stabilizing agent is a thrust research domain. In this research work, application of dialdehyde cellulose (DAC) was studied to understand the effect on the enzymatic and conformational stability in collagen. The secondary structure of collagen is not significantly altered on interaction with DAC. But, it was found that DAC lead to changes in the amplitude of the circular dichroic (CD) spectrum but did not alter the triple helical conformation of collagen. DAC treated collagen exhibited 93% resistance to collagenolytic hydrolysis. Conversely, DAC treated collagenase exhibited 89% inhibition against collagen degradation and the inhibition was found to be concentration dependent. The kinetics of inhibition of collagenase by DAC was derived from the extent of hydrolysis of (2-furanacryloyl-L-leucyl-glycyl-L-prolyl-L alanine), FALGPA. DAC exhibited non-competitive mode of inhibition against collagenase. CD data on DAC-modified collagenase substantiate the hypothesis that the inhibition of collagenase by DAC arises from secondary and quaternary structural changes in the enzyme. Gaining new insights in understanding the mechanism of stabilization of collagen by DAC through kinetics of inhibition of collagenase was presented.
 
 
Collagen D-spacing and the Effect of Fat Liquor Addition 
by K, Sizeland, H. Wells, G. Norris, R. Edmonds, N. Kirby, A. Hawley, S. Mudie and R. Haverkamp
Volume: 110      Number: 3     Page: 66-71     Year: 2015
The physical properties of leather are partly a result of the structure of the leather’s network of type I collagen fibrils. To achieve high strength and a soft, supple feel, penetrating oils(usually polyols) are added to leather during manufacture, and this process is known as fat liquoring. The modification of the collagen structure by fat liquoring (with a lanolin-based fat liquor) is investigated using synchrotron-based small angle X-ray scattering. The axial periodicity, or D-spacing, of the collagen changes as a result of fat liquoring. With no fat liquor, the D-spacing is 60.2 nm; spacing increases by 6% to 63.6 nm at 10% fat liquor. Pure lanolin results in a similar increase in D-spacing. We discuss mechanisms for fibril elongation brought about by fat liquoring. The observations of structural changes taking place within collagen fibrils as a result of fat liquoring provides new insight into the nature of fat liquoring and informs future processing developments.
 
 
Histological Analysis of the Skin Dermal Components in Bovine Hides Stored under Different Conditions 
by S. Montelli, L. Corain, B. Cozzi and A. Peruffo
Volume: 110      Number: 2     Page: 54-61     Year: 2015
The leather industries are interested in avoiding post-mortem alterations of the skin components, since degeneration of the dermal structures composing raw hides decreases the quality of leather. The goal of the present study is to realize a histological study of skin samples to assess the tissue alterations at different periods and under methods of conservation (salting and refrigeration) after the skinning of the animals at the slaughterhouse. The papillary region and the reticular dermis were both analyzed. The dermal components considered were the number of cell nuclei, the structure of the collagen and elastic fibers, and finally the presence of acidic polysaccharides. Results showed a progressive reduction of cellular nuclei and acid polysaccharides of the dermal layer during the passage of time in all the conditions considered. A moderate decay of collagen bundles was noted in salted hides whereas the elastic fiber networks maintained their organization over the time. No sign of accumulation of non-functional elements or other morphological alterations were observed in the dermis. These findings can be useful for the leather industry for choosing the desired curing and timing conditions to employ during refrigeration or salt-based treatment of the skins.
 
 
Waterborne Dimethylolpropionic Acid-diisocyanate Adducts with Alkali-deblockable Isocyanate Groups as Pretanning Agent for Chrome Tanning 
by Jie Liu, Zhou Xu, Yi Chen and Haojun Fan
Volume: 110      Number: 2     Page: 43-53     Year: 2015
Diisocyanates qualify as tanning agent by virtue of their strong tendency to crosslink collagen molecules by reacting with amino groups. However, due to their sensitivity to water, these compounds cannot be used directly in aqueous environment, which is the basis for leather processing. To address this problem, waterborne dimethylolpropionic acid-diisocyanate adducts (WDDAs) with temporarily-blocked isocyanate terminals were prepared in the present paper by using NaHSO3 as blocking agent, and further evaluated as a pretanning agent for chrome tanning. Fourier transform infrared (FTIR) spectra revealed that the isocyanate terminals in WDDAs were successfully blocked by NaHSO3. The blocked isocyanates were stable under ambient temperature, but prone to deblocking under alkaline condition. The regenerated isocyanates were found still capable of crosslinking collagen molecules to impart hydrothermal stability. In leather tanning, a high shrinkage temperature (Ts>110 oC) was achieved by successively treating goat skin with 5 wt% WDDAs and 4 wt% chrome powder. Stereomicroscope and SEM observation further indicated that the WDDA-chrome tanned leather exhibited tight grain surface and well opened up fiber structure in comparison with semi-chrome tanned leather. Due to the presence of carboxyl group in dimethylolpropionic acid, it was also found that WDDAs enhanced the absorption of chromium in the resultant leathers (% chrome uptake> 90%), resulting in significantly less Cr residual in the tanning wastewater. In addition, it is important to note that the usage of salt in pickling process was avoided owing to previous crosslinking of amino groups, which is very helpful for overcoming the problem of total dissolved solid (TDS) related to neutral salts. The tanning effect of WDDAs and their auxiliary function for chrome tanning allow them to be applicable as a pretanning agent, which efficiently alleviates the environmental impact of traditional chrome tanning for sustainability.
 
 
Determination of Hydrolytic Enzyme Capabilities of Halophilic Archaea Isolated from Hides and Skins and Their Phenotypic and Phylogenetic Identification 
by S.T. Bilgi, B. Mericli Ya and Ismail Karaboz
Volume: 110      Number: 2     Page: 33-42     Year: 2015
This research aims to isolate extremely halophilic archaea from salted hides, to determine the capacities of their hydrolytic enzymes, and to identify them by using phenotypic and molecular methods. Domestic and imported salted hide and skin samples obtained from eight different sources were used as the research material. 186 extremely halophilic microorganisms were isolated from salted raw hides and skins. Some biochemical, antibiotic sensitivity, pH, NaCl, temperature tolerance and quantitative and qualitative hydrolytic enzyme tests were performed on these isolates. In our study, taking into account the phenotypic findings of the research, 34 of 186 isolates were selected. These isolates were identified by 16S rRNA sequence analysis and 15 different strains of extreme halophilic archaea were identified. 13 strains of these were identified for first time from salted raw hide and skin in our study including Natrialba aegyptia, Halococcus thailandensis, Halococcus dombrowskii, Halovivax asiaticus, Halovivax sp. E107, Haloarchaeon, Natronococcus sp., Halorubrum sp., Halomicrobium zhouii, Natronococcus jeotgali, Haloterrigena thermotolerans, Natrinema versiforme, Halobacterium noricense. At the same time detecting Natrialba aegyptia in 6 of 8 hide samples showed that this strain is widely found in hide and skin samples. Research results are expected to contribute to other studies and solving microbial problems in leather industry.
 
 
Biobased Films Prepared from Collagen Solutions Derived from Un-tanned Hides 
by C.K. Liu, N. Latona, M. Taylor and M. Aldema-Ramos
Volume: 110      Number: 2     Page: 25-32     Year: 2015
The U.S. hide and leather industries are facing challenges of meeting environmental imperatives; quantifying, maintaining, and improving current hides and leather product quality; developing new processes and products; and improving utilization of waste. One of our contributions to address these ongoing challenges is to develop innovative uses and novel biobased products from hides to improve prospective markets and to secure a viable future for hides and leather industries. We had previously investigated the production of nonwoven and green composites from collagen fiber networks, which were extracted from un-tanned hides and from tannery solid wastes, such as splits or trimmings. Recently, we focused on preparing biobased films from un-tanned; specifically limed hides, which have potential commercial applications in medical care and food packaging. Collagen fiber networks were obtained from hides that have been processed to remove the noncollagenous materials through the hair removal and liming steps. We also focused on understanding the effects of processing steps such as bating and crosslinking treatments on the morphology and physical properties of biobased films from un-tanned hides. Results showed that the concentration of collagen solution and the methods of crosslinking with glutaraldehyde during the film formation process have significant effects on the properties of resultant films. Higher concentrations of collagen and addition of glutaraldehyde crosslinkers after solidification of the films yielded better mechanical properties. The encouraging results of this ongoing research are instrumental to produce biobased films, which have wide applications in both the medical field due to good biocompatibility and for food packaging because of excellent mechanical properties and acceptable edibility.
 
 
Rapid Fiber Opening Process for Skins: An Approach for Fail-Safe Chemical-Free Process 
by J. Durga, A. Ranjithkumar, R. Ramesh, C. Rose and C. Muralidharan
Volume: 110      Number: 1     Page: 7-12     Year: 2015
Conventional beam house operations adopted by the global tanning industry are coming under the close scrutiny of the environmentalists on account of the possible adverse effect on human health and environment. Lime, which is used to the tune of about 10% on the weight of the raw hides and skins, in re-liming stage contribute to generation of large quantities of sludge, the disposal of which is a serious concern. Also the process duration to achieve the required fiber opening in the re-liming process is very long, ranging from 24-72 hrs for different substrates and end products. Enzyme based beam house processes are being advocated to overcome the problems associated with the conventional processes. However, enzyme based methods need greater control over process parameters to achieve satisfactory results in leather processing and avoid damage to the pelt. To overcome the problems associated with the conventional re-liming process, an attempt has been made in the present investigation to utilize cocktail of carbohydrases for fiber opening of hides and skins. Fiber opening at optimized concentration of the above enzyme has been studied for its efficiency on goatskins. A process using optimum quantity of enzyme led to fiber opening in 30 minutes. The efficacy of enzyme on rapid fiber opening of dehaired skin was studied at different experimental conditions of pH, time and enzyme concentration. The performance of the enzyme in the given experimental conditions was assessed by quantifying the removal of carbohydrate and proteoglycan and examining the fiber opening by scanning electron microscopic studies. Effect of enzyme on the final quality of the leather was evaluated by changes in chemical characteristics, physical properties and visual examination.
 
 
Powdered Hide Model for Vegetable Tanning II: Hydrolyzable Tanni 
by E. Brown, M. Taylor ad L. Bumanlag
Volume: 110      Number: 1     Page: 19-22     Year: 2015
Vegetable tannages employ both condensed and hydrolyzable tannins. As part of our exploration of tanning mechanisms, we reported previously on interactions of the condensed tannin, quebracho, with powdered hide. In this study, the interactions of chestnut extract, a hydrolyzable tannin, with powdered hide samples are reported and compared with those of the condensed tannin. Hydrothermal stability of powdered hide treated with the hydrolyzable tannin reached a maximum of 75° C at a 40% offer, compared with 84° C for a similar offer of condensed tannin. The hydrolyzable tannin was much more effective at improving collagenase resistance, with nearly complete protection at <10% offer.