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Effect of Sodium Chloride on Structure of Collagen Fiber Network in Pickling and Tanning 
by Xinxin Li, Ya-nan Wang, Jing Li and Bi Shi
Volume: 111      Number: 6     Page: 230-237     Year: 2016
Tannery wastewater usually contains a high salinity due to the use of sodium chloride (NaCl) in curing and pickling. Although some no pickle tanning and salt-free pickling technologies were developed, few of them have been widely used due to relatively poor mechanical and bulk properties of the resultant leathers. Therefore, the role of NaCl in pickling and tanning should be investigated in the first place. In this study, bated pelts were pickled by salt-free pickling and conventional salt-assisted pickling processes, respectively, and then tanned by chrome tanning agent. The hierarchical structures of collagen fiber network of the pickled pelts and leathers were observed by optical microscope and SEM, while the porosity of leathers was measured. The results showed that the fiber bundles of the pelt pickled in the presence of NaCl were more sufficiently dispersed compared with those of salt-free pickled pelt. Both of the chrome tanned leathers had a regular arrangement of collagen fibers, but the leather with salt assisted pickling presented remarkably higher degree of fiber dispersion, as well as larger porosity. Moreover, the role of NaCl in organic tanning using an amphoteric organic tanning agent was investigated. The results also showed that the presence of NaCl in tanning could improve the opening up of collagen fiber network and the porosity of the leather. In general, NaCl used in leather processing presented a positive effect in consideration of leather quality.
 
 
Performance of Antimicrobial Agents for the Preservation of Chrome Leather 
by J. Fontoura, D. Ody and M. Gutterres
Volume: 111      Number: 6     Page: 221-229     Year: 2016
Fungal growth in leathers causes significant damages like stains, surface roughness and loss of physical-mechanical resistance. This raises the need to develop control strategies by the use of antimicrobial agents. Considering the improving processes with regard to the use of antimicrobial agents added in skins and leathers to prevent their contamination by fungi, this study aims to evaluate the performance of six antimicrobial agents conventionally used in the leather industry, against four different fungi. These agents were applied during the chrome tanning process. Accelerated microbiological assays (tests plating and incubation on tropical chamber) were performed, as well as sorption and wash-out testing of three selected antimicrobial agents by UV/VIS spectrophotometry and verification of surface biodeterioration through SEM. Antimicrobial agents 2-thiocyanomethylthio benzothiazole (TCMTB) and Aqueous dispersion of 2-n-octyl-4-isothiazolin-3-one + methyl Nbenzimidazol- 2-ylcarbamate (OIT+BMC/water) showed antifungal capacity against different fungi tested applied in concentration of 0.2% (weight leather base). In the tropical chamber test, for the five samples of wet-blue leather treated with antimicrobial agents the growth of fungus was not observed. From the antimicrobial agents subjected to sorption testing and wash out, the TCMTB based antimicrobial agent presented rapid and high sorption in wet blue leather and also has resistance to washing.
 
 
An Examination of Antimicrobial Activity of Lining Leathers Fatliquored with Essential Oils 
by E. Bielak, E. Marcinkowska, J. Sygula-Cholewinska and J. Golnka
Volume: 111      Number: 6     Page: 213-220     Year: 2016
To prevent losses caused by microbiological decay of leathers during technological processing, biocidal and biostatic chemical agents are used. They are introduced into the material structure at various stages of the tanning process. It has been shown that some of these agents are not neutral to human health and to the environment. Thus, substitutes for chemical preparations of appropriate efficiency in control of bacteria and fungi, but being safe to humans and the environment are sought. Suitability has been adequately confirmed by research performed worldwide on essential oils. In this paper antimicrobial resistance of lining leathers protected with essential oils extracted from plants Cinnamomum verum, Eucalyptus globulus, Origanum vulgare, Leptospermum scoparium and Thymus vulgaris is investigated. They were introduced into the leather at the fatliquoring stage at 5% per weight of leather. Antimicrobial activity of samples oiled with essential oils and controls (without these oils) was evaluated against bacteria Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and yeasts Candida albicans after 1 and 6 months. The growth inhibition zone around leather samples and microorganism growth, or lack of growth, within the sample-medium contact zone was determined. Investigations have confirmed the efficiency of three of five proposed oils: oregano, cinnamon and thyme. The strongest and most longlasting antimicrobial activity was observed for leathers preserved with oregano oil. Insufficient effect was found for leathers oiled with manuka and eucalyptus oils.
 
 
Effect of Different Unhairing Methods on the Ionic Liquid Based Fiber Opening Process 
by M. Azhar, G. Jayakumar, J. Raghava Rao and N. Fathima
Volume: 111      Number: 6     Page: 206-212     Year: 2016
Leather processing is known to impact the environment, especially the pre-tanning processes. Lime sludge is one of the major concerns for the industry. Application of ionic liquid (1- butyl 3- methylimidazolium chloride) instead of conventional reliming practice can reduce this problem to a large extent. In this study, the effect of different unhairing process on the fiber opening using ionic liquids has been studied. The extent of fiber opening was assessed for both control and experimental pelts through SEM analysis. The experimental pelts were found to have better fiber opening than the control. The ionic liquid fiber opened pelts were tanned and the spent liquors were assessed for the chrome content, COD, TDS. The results indicate that all the environmental parameters are better or on par with the conventional process. The final leathers made were also found to have physical characteristics similar to that of conventionally limed leathers.
 
 
Preparation of Biobased Sponges from Un-tanned Hides 
by A. Siddique, N. Latona, M. Taylor and Cheng-Kung Liu
Volume: 111      Number: 5     Page: 192-199     Year: 2016
One of our research endeavors to address ongoing challenges faced by the U.S. hide and leather industries 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, green composites, and films from collagen fiber networks, which were extracted from un-tanned hides and from tannery solid wastes, such as splits or trimmings. Recently, we investigated the preparation of biobased sponges from un-tanned, specifically limed hides, which have potential commercial applications in medical care. We also investigated the effects of processing steps such as bating and alkaline treatments using sodium hydroxide (NaOH) on the morphology and viscoelasticity of resultant sponges from un-tanned hides. Results showed that the treatments of fiber networks have significant effects on the properties of resultant sponges. The dynamic mechanical analysis showed alkaline treatments yielded stiffer sponges than limed and bated samples. SDS-PAGE analysis showed the molecular weights of sponges were maintained in the range as those of commercial collagen samples. Lastly the resultant sponges are in the desirable apparent density range for a potential application as a medical sponge.
 
 
Low Carbon Products to Design Innovative Leather Processes. Part IV: Manufacture of Automotive Leather using Tara 
by L. Olle, J. Diaz, C. Casas, and A. Bacardit
Volume: 111      Number: 5     Page: 185-191     Year: 2016
In three previous studies, it has been used the fruit of the tara tree (Cæsalpinia Spinosa) as a pre-tanning agent1. This new tailored tara product will be able to facilitate the penetration of the tannin molecules through the leather section, avoiding or reducing the use of aldehydes, syntans, common vegetable tannins and other mineral salts. The aim of this part of the study is to manufacture final articles meeting the parameters set by different regulations, and assess if this modified tara can be marketed and used in the industry to replace some less sustainable products.
 
 
The Effect of CloisiteŽNa+ Nanoclay Filler on the Morphology and Mechanical Properties of Loose Leather 
by S. Prabakar, C. Whitby, A. Henning and G. Holmes
Volume: 111      Number: 5     Page: 178-184     Year: 2016
Looseness describes a structural fault in leather, which leads to the development of wrinkles on the surface when the leather is bent inwards. It causes up to 7% of hides processed to finished leather to be downgraded or rejected at final inspection, requiring replacement and causing delay in meeting orders. Fillers can fill the interstitial spaces in loose leathers and make the looseness less pronounced. Here, the effect of CloisiteŽNa+, ananoclay filler, on loose cattle hides is investigated by electron microscopy and mechanical characterization. Whilst SEM studies show an apparent filling effect in the grain-corium boundary at increasing concentrations of filler, TEM images show that at an optimum concentration of 3% uniform dispersion of the filler along with good handle can be obtained. A gradual increase in tensile and tear strength is observed with increasing concentration of CloisiteŽ Na+, however softness measurements correlated with microscopic observations in that only at optimum concentrations can both good handle and mechanical strength be achieved. We discuss a possible mechanism for the change in mechanical properties and handle of the loose leather after treating with CloisiteŽNa+. The mechanistic study of such treatments on low quality hides will result in the production of leathers with more uniform cutting area and added functionality.
 
 
Accelerated Liming Process Using Phase Transfer Catalyst 
by N. Vedaraman, K. Sandhya, K. Velappan and C. Muralidharan
Volume: 111      Number: 5     Page: 171-177     Year: 2016
In the present work, effect of using phase transfer catalysts (PTC) was studied in liming and re-liming processes of goat skin, for decrease in the processing time, thereby increasing productivity. Three different Phase Transfer Catalysts; Tetramethylammonium Hydroxide (TMAH), Tetraethylammonium Hydroxide (TEAH) and Tetrabutylammonium Hydroxide (TBAH) were chosen and experiments were conducted on liming and re-liming of goat skin to select suitable catalyst in comparison with the conventional liming process. The monitoring parameters were ease of hair removal and increase in pelt weight to find the maximum swelling and plumping. After determining the optimal PTC amount, studies were also carried out on reuse of liquor containing PTC with replenishment. Use of TMAH in liming process was found to bring about significant time reduction and could bring improved swelling in liming and re-liming processes.
 
 
Reaction of Protein and Carbohydrates with EDC for Making Unique Biomaterials 
by M. Taylor, L. Bumanlag, E. Brown and C.-K. Liu
Volume: 111      Number: 4     Page: 155-164     Year: 2016
Prior research from this laboratory has demonstrated the feasibility of using chemical and enzymatic treatments on protein and carbohydrate waste products for the purpose of making fillers to enhance the properties of leather. These treatments (microbial transglutaminase, genipin, and polyphenols in the form of vegetable tannins), were effective in reacting with gelatins, whey protein concentrate (WPC), and/or chitosan, alone or in combinations, to give products with interesting functional properties. All crosslinkers were either natural products and/or sustainable materials. In our continuing studies of chemoenzymatic methods to crosslink collagen and collagen by-products, we investigated the extensively reported 1-ethyl-3-(3 dimethylaminopropyl) carbodiimide hydrochloride (EDC), which has been used to crosslink proteins for purpose of making biomaterials. This present study examined the reactivity of various concentrations of EDC with gelatin, chitosan and combinations of both, in the presence and absence of N-hydroxysuccinimide (NHS) at optimal times, and temperatures, and the effect these parameters had on physical properties, molecular weight distribution and free amine content. It was found that both gelatin and chitosan had reactivity with EDC and the physical properties reflected the concentration of both the carbodiimide and gelatin. It was found however that when the gelatin and chitosan were reacted together in the presence of the carbodiimide, the physical properties improved significantly over the protein and carbohydrate when reacted separately, resulting in unique products. This study provides a better understanding of the reactivity of carbodiimide and optimal conditions for developing appropriate products.
 
 
A Polyurethane-based Retanning Agent with Fluorescent Effect 
by Saiqi Tian, Peikun Zhang, Haojun Fan, Yi Chen, Jun Yan and Bi Shi
Volume: 111      Number: 4     Page: 148-154     Year: 2016
A novel fluorescent waterborne polyurethane retanning agent (FWPRA) was prepared through chemically incorporation of fluorescer, disodium 4, 4’-bi s[4 - a n i l i no - 6 - hydroxyethylamino-6-(2-choloronilino-1,3,5 triazin-2-yl) amino]stilbene-2,2’-disulphonate (RSW), into polyurethane backbone as a chain extender. The chemical structure was characterized by FTIR, 1H NMR and UV−vis spectrophotometer, and fluorescence performances of FWPRA, RSW together with resultant leather were investigated systematically. The results indicate that polymerization has a positive effect on optical performance; FWPRA shows enhanced fluorescence intensity in comparison with fluorescer RSW. In the retanning process, no decay of optical performance can be found when chromium(III) salt and chestnut extract are used together, which reveals that FWPRA presents good fluorescence stability to other chemicals. For wet blue retanned by FWPRA, the shrinkage temperature, thickness as well as mechanical properties are improved. Most importantly, the resultant leather exhibits magic fluorescence effect under UV lamp.