Leather Technology

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http://etd.aau.edu.et/handle/12345678/131

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Browsing Leather Technology by Author "Berhanu, Assefa (PhD)"

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    Characterization and Optimization of Chrome Free Tanning System Using Combination of Chestnut and Tetrakis Hydroxymethyl Phosphonium Sulfate
    (Addis Ababa University, 2021-09) Haftom, Girmay; Berhanu, Assefa (PhD)
    Currently, chrome tanning accounts for more than 90% of global leather manufacturing. This tanning system result in significant material loss and considerable environmental concerns. In the present work, chrome free combination tanning system using a combination tanning system based on Chestnut and THPS is presented. The processing method for Experimental tanning trials were carried out with different percentages of Chestnut as a tannage followed by varying percentages of THPS as a re-tannage for process optimization. The leathers obtained were characterized for their physical strength characteristics, comfort & organoleptic properties, scanning electron microscopic analysis, reflectance measurements and environmental characteristics. The Chestnut-THPS leathers tanned using 20% chestnut followed by 2% THPS resulted in shrinkage temperature of 95OC. The hydrothermal stability of the combination has been found better than the Chestnut alone and THPS alone tanned leathers, respectively. The strength properties and comfort properties of leathers obtained are on par with or better than the control chrome, Chestnut alone and THPS alone tanned leathers. The organoleptic properties of the experimental crust leathers exhibit good grain smoothness, fullness, grain tightness, general appearance compared to control chrome tanned crust leathers. Environmental impact assessment shows the combination tanning system results a significant reduction in TS, TDS, TSS and BOD in the waste water when compared to that of control tanning system. The study presented in this paper established the use of Chestnut and THPS combination tanning system as an effective alternative cleaner tanning methodology.
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    Extraction and Characterization of Elastin from Raw Hide Trimmings using Autoclave Extraction Technology
    (Addis Ababa University, 2018-06) Zerihun, Yoseph; Berhanu, Assefa (PhD)
    During leather processing, raw skins/hides are trimmed and thrown as wastes and accounting for pollution load in leather industry. Elastin is a fibrous protein with multifaceted applications in biomedical field due to its intrinsic biological annotations viz elasticity and cell interactions, the extraction process is challenging task due to their cell interactive properties, the application is versatile and the price is in current international market is highly expensive. In this context, leather solid wastes specifically raw hide trimmings have been found out in the research as the potential source of raw material for elastin extraction. In this research, the raw Hide Trimming elastin content was estimated between in the range of 122 mAUmin and 97 mAUmin using the combination of FPLC, UV-Spectroscopy, SDS-PAGE protein scientific characterization techniques. The Elastin was extracted from leather waste through autoclaving technology, the method yield was found to be 90%. In addition, the biocompatibility study confirms that there is no toxic nature of extracted elastin for biological application. This implies that the selected extraction process was effective and efficient. The physical characterization using DSC result indicates that the melting peak of elastin was -0.5420 watt/g at 103.23 C, elastin showed very high denaturation temperature of 275.82 o C and TGA studies confirm that elastin have six mass loss degradation steps. The chemical characterization result using o C Solid state NMR and FTIR that elastin shows random coil, α-helix and β-strand secondary structure. Moreover, the FTIR confirm that amide A, I, II, III, IV, V, VI, and VII functional group existed in the elastin fiber. The biological characterization using amino acid analysis result show that the amino acid composition chain of the product have high amount of glycine, non-polar amino acid, low amount of acidic amino acids, low amount of hydroxyl amino acid and there is no hydroxylsine, tryptophan and Cysteine amino acids in the amino acid composition of the protein fiber. The little variations were the existence of high amount of basic amino acids in the protein amino acid composition due to the presence of collagen residues. Finally, the biocompatibility study shows that there is no toxicity nature of the extracted elastin fiber for human keratinocyte cells culture. There result is scientifically justified and confirmed that the raw hide trimmings extracted elastin makes feasible for biological and biomedical applications.
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    Improvement of Colour Uniformity During Dyeing Operation: The Case of Dress Gloving Leather
    (Addis Ababa University, 2018-06-17) Wondwossen, Mamuye; Berhanu, Assefa (PhD); Aravindhan, R. (PhD); Jawahar, Malathy (Mrs.)
    In leather industry, the tanner produces a production lot with large number of leather samples to match a colour provided by a client. However, even when the leathers are dyed with the same colorants under well monitored conditions may show some colour non-uniformity. This is highly challenging today for leather manufacturers, especially glove producers to sort colour of leathers consistently. The present study is focused on identifying the factors of colour variation during dyeing operation and reducing colour non-uniformity by managing the factors with welldesigned dyeing recipe. Dyeing properties of the dyestuffs was investigated, by choosing two commercially available dye stuffs. Factors of colour non-uniformity are identified by conducting dye trials on possible causes of colour non-uniformity with four different well-designed dyeing recipes. When concentration of dyestuff, substance of skin or length of dyeing float are varied individually keeping others factors the same, a perceivable total colour difference (∆E*≥0.5) is observed. Controlling and monitoring of colour non-uniformity is analyzed by conducting dye trials using four different well-designed dyeing recipes viz. reverse dyeing recipe, regular dyeing recipe, the multiple stage dyeing recipe and regular dyeing recipe with dye levelling agent. The total colour difference (∆E*) values obtained using multiple stage dyeing recipe was smallest as compared to the other three recipes by varying all possible factors of colour non-uniformity individually. From these observations, multiple stage dyeing recipe was the best alternative way to manage colour non-uniformity.