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Control of Microorganisms on Tanned Leather: From Fungicide to Antimicrobial Function Leather 
by Haibin Gu, Li Zhao, Jun Ma, Yingjie Yang, Changqing Zhao and Wuyong Chena
Volume: 111      Number: 2     Page: 69-87     Year: 2016
To inhibit the microbial growth on tanned leathers including wetblue, crust leathers, finished leathers and their goods (shoes, garments, bags, etc.), fungicides are usually applied during various leather-making processes. Under the situation of increasingly strict environmental legislation, all kinds of ecofriendly fungicides were explored recently to replace the currently used noxious ones in leather industry. Meanwhile, a nontraditional new type of leather, called antimicrobial function leather, attracted more and more attention from leather chemists and technologists, because of its tempting antimicrobial protection provided and wide application prospects in many fields such as medical materials, health products, daily products, public transport vehicles, and so on. Based on the literatures published in the past decade, especially in the past five years, this review systematically and comprehensively summarizes current status and development trend about leather fungicides and antimicrobial function leather. The discussed antimicrobials contain traditional organic synthetic fungicides with small molecular weight, natural essential oils, macromolecular polymers and chitosan derivatives, and nano-inorganic antimicrobials (nanosilver, nano-ZnO, nano-TiO2, nano-SiO2, etc.). Finally, several proposals are addressed for the development of new leather fungicides and antimicrobial function leather, and especially, a new viewpoint, in which the antimicrobial leather is prepared based on various tanning mechanisms, is demonstrably presented to solve the problem of loose combination between antimicrobial substances and leather fibers.
 
 
Recovery, Purification and Reuse of Contaminated Sodium Chloride Obtained from Tanneries for Raw Goat Skin Preservation 
by N. Vedaraman, K. Sandhya, V. Brindha, A. Selvi, K. Velappan and C. Muralidharan
Volume: 111      Number: 2     Page: 62-68     Year: 2016
Large quantity of sodium chloride is used for raw skin preservation. Significant amount of salt is removed from raw skin through a mechanical process before taking for further processing in tanneries. This recovered salt is contaminated with various dirt, proteinous materials and microorganisms and gets accumulated, which creates a serious waste disposal problem for tanneries. In this study the recovered contaminated waste salt was purified and reused for skin preservation. The recovered contaminated salt from tannery was dissolved in water, filtered, treated with activated charcoal to remove the undesired components and subjected to ozone treatment for the removal of microbial contamination. The ozonized solution was subjected to solar evaporation. Improved evaporation techniques were employed to facilitate evaporation of salt solution. Dried purified salt obtained was checked for microbial contamination. Then the dry salt was used for the preservation of a fresh batch of animal skin. After a minimum storage period of 21 days, the skins were processed into leather as per the usual procedure and compared with the leathers obtained by conventional fresh salt preserved skins. The physical tests, chemical analysis and organoletic properties of experimental leathers show that the quality of leather obtained from animal skins preserved using purified salt was comparable to leathers obtained from conventional pure salt preserved skins. The approach minimizes salinity concerns of tanning by providing simple and practical solution.
 
 
Optimization of Enzyme-assisted Phenolic Reactions Applied to Thermal Stabilization of Collagen using Response Surface Methodology 
by L. Santos, S. Allen and A.P. Antunes
Volume: 111      Number: 2     Page: 53-61     Year: 2016
Vegetable tannins used in tanning of hides and skins are limited by surface reactions as well as large molecular weights, reducing penetration into the skin and lowering the thermal stability or tanning effect. Investigation into the utilization of small phenolic compounds such as catechin to improve penetration with subsequent in situ enzymecatalysed polymerization may provide a novel and alternative tanning agent. In this study, catechin was oxidized by enzymatic catalysis using laccase, with the polymerization confirmed by FT-IR and UHPLC. Tanning experiments were undertaken to measure the effect of laccase-catalysed polymerization of catechin in the thermal stabilization of collagen, i.e., the change in shrinkage temperature between the treated and untreated sample of hide powder (ÄTs). A factorial design was subsequently used to study process parameters that may affect enzymatic reactions: temperature, substrate concentration, enzyme concentration and incubation period. The statistically significant variables were found to be temperature and incubation period, and were thus chosen to be studied further for process optimization using response surface methodology. Maximum ÄTs can be obtained for a temperature of 34.6°C and incubation period of 25 hours. This study demonstrates that the stabilization of collagen (ÄTs) is increased with the use of enzyme-assisted polymerization.
 
 
Development of Aluminum-melamine Formulations for Retanning Application 
by M. Sathish, Z. Azhar, R. Aravindhan, K.J. Sreeram and J. Raghava Rao
Volume: 111      Number: 2     Page: 44-52     Year: 2016
The process of preparation of a large number of syntans is based on enhancement of the molecular weight of low molecular weight aromatic/aliphatic monomers etc., through addition polymerization and condensation reactions. The disadvantage associated with condensation process is the use of formaldehyde, which is a proven carcinogen. In addition, one of the major drawbacks with chrome tanning, the lack of fullness, is addressed during post tanning processes by employing synthetic tanning agents. With these issues in focus, formaldehyde free aluminum based melamine syntan has been prepared having particle size distribution in the range of 450-700 nm and stable up to pH 4.5. The prepared syntan has been used as retanning agent in leather processing. The experimental leather exhibits superior organoleptic properties such as fullness, grain tightness, and physical strength characteristics such as tensile, tear strength compared to control leather. Also, experimental leather exhibits higher dye intensity compared to control leather. It is evident from the air permeability and pore size distribution analysis that the prepared product has significantly arrested the pores thereby increasing the fullness of leather. Scanning electron microscopic image shows that the experimental leathers have a flat and compact fiber structure.
 
 
Collagen Hydrolysate Extraction from Chromed Leather Waste for Polymeric Film Production 
by B. Scopel, D. Lamers, E. Matos, C. Baldasso and A. Dettmer
Volume: 111      Number: 1     Page: 30-40     Year: 2016
The generation of hazardous wastes and the overuse of nonrenewable sources in polymeric materials production are two major concerns for researchers worldwide. In this paper, an innovative approach to changing chromed leather waste (CLW) into a raw material for polymeric film production was studied. Collagen hydrolysate was extracted from CLW through alkaline hydrolysis. Time, temperature, agitation speed, type and mass of alkalinizing agent were tested. The optimum condition for collagen hydrolysate production (the one that results in a high protein and low chromium content) was determined. According to statistical analysis, hydrolysis performed for 6 h using a proportion of 4 g of MgO for each 50 g of CLW and 250 ml of water at 70°C and 180 rpm of agitation speed led to the best protein/chromium ratio in the collagen hydrolysate (TKN: 2,185.7 mg/L, Cr: <0.04 mg/L). The collagen hydrolysate obtained with optimum condition of production was then mixed with starch - a renewable source for polymeric material production - and glycerol - a byproduct of biodiesel production - to produce polymeric films by casting technique. Mechanical properties of four different compositions (with and without the presence of collagen hydrolysate and glycerol) of films were compared. The films produced with the addition of glycerol and collagen hydrolysate presented mechanical properties similar to the ones of commercial biodegradable films applied as mulches in agriculture. They also have in their composition a compound present in fertilizers - nitrogen - and possible traces of chromium, which is a micronutrient. Therefore, they can be an alternative to synthetic polymers.
 
 
Use of Viscoelastic Changes to Demonstrate the Relationship Between Drying Parameters - A Preliminary Study 
by W. Wise, A. Covington, K. Flowers and A. Peruzzi
Volume: 111      Number: 1     Page: 24-29     Year: 2016
Dynamic mechanical thermal analysis (DMTA) is routinely used for mechanical analysis by the polymer industry to provide information on the viscoelastic properties of a material. This report reveals how DMTA has been used to further previous studies by providing insight into the differences between post-tanned leathers (chromium and chromium-free). It demonstrates the potential to correlate the results with an industrial application such as optimization of the drying conditions during cell rotary conditioning (CRC). DMTA can indicate leather fiber response to changes in atmospheric humidity and temperature, potentially facilitating real-time adaptation of conditions during leather drying. Initial DMTA results show that post-tanning, particularly fatliquoring, changes the rate of drying and allows scientists to advise on optimal leather drying conditions based on viscoelastic changes.
 
 
Short-term Preservation of Hide and Skins Using Peracetic Acid 
by V. Valeika, K. Beleska and J. Sirvaityte
Volume: 111      Number: 1     Page: 1-9     Year: 2016
Treatment with a mixture of sodium hydroxide, hydrogen peroxide and acetic anhydride at 15 20oC during 2 h allows preservation of hide during 20 days at temperature 22±1oC. Prolongation of the treatment duration more than 2 h and increase of the treatment temperature higher than 20oC do not markedly increase the preservation effect but affects hide structure at these higher level. The application of short term preservation methods leads to substantial decrease of materials consumption. Preserved by oxidative method hide is more sensitive to chemicals during technological processes than ones cured by sodium chloride, and its derma structure is opened in higher level. It binds more chromium compounds during chroming. The crust leather produced from hide preserved by oxidative method characterized by satisfactory strength properties. The use of proposed short term preservation of hide allows reduction of Cl–concentration in wastewater more than 11 times.
 
 
Eco-Friendly, Rapid and Efficient Analytical Procedure for Carcinogenic Aryl Amines in Dyes and Consumer Products 
by S. Suresh, R. Ganeshjeevan, N. Priya and C. Muralidharan
Volume: 111      Number: 1     Page: 17-23     Year: 2016
This study addressed the analysis of aromatic amines from azo dyes and dyed consumer articles mainly based on leather as they are subjected to screening for release of any of the 24 hazardous aryl amines listed by the European agency. This study involves a reverse phase SPE approach for enriching, and cleaning-up of the matrices to facilitate further analysis by UPLC. The proposed study does away with tertiary butyl ether, other solvents and subsequent evaporation steps thereby cutting down the solvent usage to a major extent (from close to 80ml into 2ml) in sample preparation and the further analysis developed by UPLC, cut short the gradient analysis from 40 min to 6 min enabling additionally the reduction of solvent for mobile phase. Thus the procedure is improvised to serve as Green analytical procedure. The present study offers the scope to complete the sample preparation in 45 min in comparison to 180min by the official procedure (excluding the degreasing step in both these cases). The proposed procedure is simple to adopt with more efficient recovery values in the range 52-104% for all the analytes. The LOD and LOQ of the analysis were 2μg g -1 and 9μg g -1.
 
 
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.