Leather and Footwear Journal

Volume 23, no 1

Contents
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REDUCTION OF POLLUTANTS IN THE TANNING INDUSTRY USING THE REVERSE TANNING METHOD AGAINST THE PHYSICAL PROPERTIES OF LEATHER
- Pages 3-10
  Heru Budi SUSANTO, Swatika JUHANA*
  - Department of Leather Processing Technology, Politeknik ATK Yogyakarta, Sewon, Bantul, 55281, Yogyakarta, Indonesia, swatika.rustiawan@gmail.com
  ABSTRACT. This study aims to tan the skin with reverse tanning based on the order of pH, thereby reducing the use of chemicals and water due to the pH regulation process. The reverse tanning method will result in a faster tanning process and reduce the use of many chemicals, so that the pollutant load released from the tanning process will be much reduced. Conventional leather tanning is carried out through many processes starting from the BHO (Beam House Operation) process, tanning, post-tanning, and finishing; this process is carried out through a 14-15 step process that produces a large number of pollutants. This is because in conventional leather processing a lot of pH adjustment processes are carried out that go back and forth. In this study the leather processing steps were ordered based on the pH of the tanning process, the chemicals and the pH of the process were regulated by the sequence of the process steps to avoid some repeated acidification and basification/neutralization as in conventional leather processing. The process begins with soaking, liming, fleshing, deliming, tanning, dyeing, fatliquoring, and chrome tanning. This process begins with an alkaline pH of 11 and ends with an acidic pH of 3.8. Chrome tanning is done with variations in the amount of chrome of 2%, 3%, 4%. The results showed that leather with 4% chromium produced the highest Ts of 103 °C, tensile strength of 39.86 N, tearing strength of 13.19 N/mm, seam strength of 12.8 N/mm, elongation of 46.87%, Cr content (VI) 1.68 ppm. These results have met the standard ISO/TR 20879:2007 Footwear. The reverse tanning process with a process from high to low pH without adjusting the pH back and forth by adding solutions and salts means reducing liquid waste in the leather tanning process. So, this process can reduce the amount of liquid waste or pollutants.
  
  KEY WORDS: reverse tanning, leather processing, chrome tanning, shrinkage temperature
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EFFECT OF ISOCYANATE AS CROSS-LINKER TO REDUCE DELAMINATION OF FINISHED LEATHER FOR AUTOMOTIVE SEAT COVER
- Pages 11-18
  Prasetyo HERMAWAN, Sekar Nirwana SARI, Wahyu Fajar WINATA*, Elis NURBALIA
  - Program Studi Teknologi Pengolahan Kulit, Politeknik ATK Yogyakarta, Indonesia, wahyufajarwinata88@gmail.com
  ABSTRACT. This study aims to improve the quality of finished leather for seat covers by knowing the effect of isocyanate as a cross-linker to reduce delamination on the finished leather. Delamination is a condition where the three layers of finish (base coat, medium coat, and top coat) do not stick together, resulting in the lifting of the top coat during the adhesion test. The raw material used in the trial is C60 quality crust dyed cowhide, 1.1 mm to 1.4 mm thick with an area of ± 3 sqft. The stages of the finishing process include semi-finished selection, stacking, spraying (base coat), rest, stacking, roller embossing, rest, milling, stacking, spraying (medium coat, top coat), rest, stacking, laboratory, and measuring. The formulation of the improved seat cover article was carried out by increasing the percentage of cross-linker in the base coat mixture. The production formulation used 2% cross-linker, trial 1 used 3% cross-linker, and trial 2 used 4% cross-linker. The best results are with the addition of 4% cross-linker to reduce delamination and have an adhesion resistance value of 24.5 N. The conclusion is that the greater the addition of cross-linker as much as 4% in the base coat of the article seat cover will reduce delamination, increase thickness from 1.1 mm to 1.2 mm, improve color fastness resistance to a value of 4, and reduce softness value from 3.92 mm to 3.42 mm.
  
  KEY WORDS: leather, cross-linker, delamination, adhesion
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THE EFFECT OF HEATING TIME ON THE THERMAL STABILITY OF CHROME-TANNED LEATHER
- Pages 19-30
  Gresy GRIYANITASARI^{1, 2}, Ambar PERTIWININGRUM², Nanung Agus FITRIYANTO², Yuny ERWANTO^{2, *}
  - ¹Center of Standardization and Services for Leather, Rubber, and Plastics Industry, Ministry of Industry, Jl. Sokonandi No. 9 Yogyakarta, Indonesia 55166
  - ²Division of Animal Products Technology, Faculty of Animal Science, Universitas Gadjah Mada, Jl. Fauna No. 03, Bulak Sumur, Yogyakarta, Indonesia 55281
  ABSTRACT. Chrome tanning is an essential process to convert raw animal skin into leather, in which collagen, as the main structure of leather, is stabilized against degradation through cross-linking using chromium, consisting of two steps: penetration and basicity. However, the uptake of chrome in leather still needs to be improved. The purpose of this study was to find the best heating time in the chrome tanning process by thermal analysis. Pickled sheepskin was used as raw material for the chromium tanning process. The samples were varied into four categories: heated at the penetration stage of the tanning process (Initial Heating), heated at the basification stage of the tanning process (Final Heating), and heated both at the penetration and basification stage (Continuous Heating). In this study, the thermal stability of wet blue leather was evaluated by shrinkage temperature behavior (Ts), thermogravimetry analysis (TGA/DTG), and differential scanning calorimetry (DSC). The tanning efficiency was measured by Cr₂O₃ content. The results demonstrated that wet blue samples heated continuously shows better thermal characteristics. In conclusion, the results can be used for finding the best possible technique for the leather tanning process using chrome salts to gain thermal stability.
  
  KEY WORDS: chrome tanning, leather, thermal stability
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STUDY OF ADHESION-COHESION INTERACTIONS BETWEEN POLYMERS IN ADHESIVE COMPOSITIONS
- Pages 31-42
  Darina ZHELEVA*, Rashko DIMITROV†
  - University of Chemical Technology and Metallurgy, Sofia, Bulgaria, Kl. Ohridski blvd., 8, e-mail: darinajeleva@abv.bg
  ABSTRACT. The results of the research prove that adhesives based on chloroprene rubber can be obtained not only in combination with phenol-formaldehyde resins, but also with other polymers. Selected chlorobutyl rubber (CIIR) and high styrene rubber (KER) proved to be substitutes for phenolic resins, which were used to obtain adhesive compositions with good properties. Despite the existing opinion on the same polarity of the components of the adhesive composition, guaranteeing the most favorable properties, it was shown that compositions with different polarity have all the parameters of quality adhesives. Components with different polarity also show the effect of mutual reinforcement, which determines the alignment, orientation ability of macromolecular chains and occurrence of cohesion and adhesion interactions. The observed textures obtained after mechanical impact proved this claim. Adhesives with more developed textures have better adhesive properties. The selected research methods successfully predict the properties of the components and facilitate their selection and amount.
  
  KEY WORDS: adhesives, rubbers, mutual reinforcement, morphology
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AN APPLICATION OF PARETO ANALYSIS AND CAUSE-AND-EFFECT DIAGRAM IN RAW HIDE AND SKIN DEFECTS MINIMIZATION IN ETHIOPIA: SELECTED CASE DIRE DAWA CITY SLAUGHTERHOUSE (ETHIOPIA)
- Pages 43-54
  Berihun NEGASH*
  - Dire Dawa University, Institute of Technology, Postal Address: 1362, Postal Code: 3000, Dire Dawa, Ethiopia, email: negashber2005@gmail.com
  ABSTRACT. According to the reports of CSA (Central Statistics Agency) 2020 Ethiopia is the 10^th in the world and 1^st in Africa by cattle production. Furthermore, the leather sector is the priority sector in Ethiopia. Leather industries are facing challenges in improving productivity and quality in the competitive market nowadays. The input materials for leather industries are goat and sheep skin, and cattle hide in Ethiopia. However, there are raw hide and skin defects due to preslaughter, during slaughter and post-slaughter process. This study focuses on the minimization of the major defects in preslaughter and during the slaughter of raw hide and skin process by application of Pareto analysis and fishbone diagram in Ethiopia in the case of Dire Dawa city. The Pareto analysis reveals that priority should be given to solving the problems of pre-slaughter and during-slaughter defects of raw hide and skin. Based on cause-and-effect diagram analysis, the main causes are: machine, material, environment, man, measures and management, root causes, heated metal shape for brand mark, during diseases different action is taken, hit animal using different steel, grass used for food, animals home making material, drinking water, stick, topography, hot area, old area, lack of awareness about hide and skin outputs, traditional methods of water in forage for the animals during farming, traditional methods used for medications for raw hide and defects identified. Finally, a few recommendations are made to reduce raw hide and skin defects.
  
  KEY WORDS: raw hide and skin quality management in preslaughter and during slaughter, leather, Pareto and fishbone diagram
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BIODEGRADABLE POLYMER COMPOSITE BASED ON POLYVINYL CHLORIDE AND POLY (ETHYLENE-VINYL ACETATE) WASTE
- Pages 55-64
  Laurenţia ALEXANDRESCU*, Mihai GEORGESCU, Maria SÖNMEZ, Mihaela NIȚUICĂ, Maria-Daniela STELESCU, Dana GURĂU
  - INCDTP - Division: Leather and Footwear Research Institute, 93 Ion Minulescu St., sector 3, Bucharest, Romania, laurentia.alexandrescu@icpi.ro
  ABSTRACT. This paper presents experiments on developing and characterizing biodegradable polymer composites based on polyvinyl chloride and expanded poly(ethylene vinyl acetate) (EVA) post-consumer waste. This type of waste is a thermoplastic material collected from the footwear industry, residues from the production of outer and intermediate soles and used footwear. It is used due to its shock absorption properties and low density (0.6-0.8 g/cm³). To make these products, EVA is injected into molds, a process that generates waste that cannot be reused. In this paper, a method of EVA waste recovery is presented and the possibility of developing a recycled product is investigated. Expanded EVA waste is cryogenically ground to sizes of min. 500 nm, functionalized by a mechanical process at temperature with polydimethylsiloxane (PDMS) and mixed in the composite in various proportions (10, 20, 50%). This composite will be made into a low-density product, with low cost, recovery and reuse of waste, and last but not least, biodegradable. The methodology for making the new materials involves the following steps: sorting waste, grinding, functionalization and compounding. These operations are easy to manage and do not involve new equipment. Compounding, the most important operation, will be performed on an extruder-granulator. The experimented biodegradable composites were physico-mechanically characterized. Waste transformation (ground and functionalized) into new value-added products will lead to remarkable improvements in the life cycle of raw materials and the sustainable use of this waste, contributing to sustainability, improving eco-efficiency and economic efficiency and reducing the “pressure” of waste on the environment.
  
  KEY WORDS: expanded EVA waste, polymer composite, biodegradability
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