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Surface charge and isoelectric point of leather : a novel determination method and its application in leather making / Ya-Nan Wang in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXII, N° 7 (07/2017)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXII, N° 7 (07/2017) . - p. 224-231 Titre : Surface charge and isoelectric point of leather : a novel determination method and its application in leather making Type de document : texte imprimé Auteurs : Ya-Nan Wang, Auteur ; Wanli Huang, Auteur ; Hongshou Zhang, Auteur ; Ling Tian, Auteur ; Jianfei Zhou, Auteur ; Bi Shi, Auteur Année de publication : 2017 Article en page(s) : p. 224-231 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Cuir Point isoélectrique En biochimie, le point isoélectrique (pI) ou potentiel hydrogène isoélectrique (pHI) est le pH auquel une molécule est sous forme d'ion mixte ou, en physico-chimie, le pH d'une solution aqueuse dans laquelle un solide existe sous un potentiel électrique neutre. En physico-chimie : Selon Bolger, le caractère acide ou basique d'une surface s'exprime par son point isoélectrique " Is ou IEPS (Iso Electric point for the surface) " ou point de charge nulle " PCN ou PZC (Point of Zero Charge) ", défini comme étant le pH de la solution aqueuse dans laquelle le solide existe sous un potentiel électrique neutre. Si le pH de la solution est basique, la surface est acide, et inversement. La différence entre le PZC et l'IEPS est basée sur le phénomène d'adsorption spécifique. On peut considérer que si la grandeur mesurée ne dépend pas de la solution utilisée pour la mesurer (pH, concentration, nature des ions), alors on a affaire à un PZC. Dans le cas contraire, c'est un IEPS que l'on mesure. Par exemple, quand la mesure de goutte sessile à deux liquides est utilisée, on considère en général qu'il n'y a pas adsorption des ions de cette goutte et que la goutte déplace complètement l'alcane qui sert de deuxième liquide: on est alors en présence d’un PZC. Au contraire, dans les mesures de potentiel d'écoulement (streaming potential), la solution joue un rôle important et c'est un IEPS que l'on mesure. Enfin, la charge nette se définit grâce au pH de la solution aqueuse dans laquelle la surface métallique existe, dans un état électriquement neutre (c’est-à-dire [M-OH2+ surf]=[M-O- surf]) et au PZC. - Si pH < PZC alors la charge nette est positive - Si pH > PZC alors la charge nette est négative. Il existe plusieurs méthodes expérimentales permettant de décrire l’état acido-basique de la surface : la mesure du potentiel d’écoulement, la photoélectrochimie, la mesure de l’angle de contact, et la spectroscopie XPS. Potentiel zeta Surfaces -- Analyse Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Surface charge and isoelectric point (pI) of leather play an important role in leather making processes. However, a proper method for the determination of surface charge and pI of leather is unavailable nowadays due to the complexity of leather structure and property, especially for the burgeoning chrome-free tanned leathers. Therefore, it is necessary to develop a quantitative determination method. In this study, a novel method for determining zeta potential (to characterize the surface charge of leather) of solid-state leather was established using a zeta potential analyzer based on the principle of streaming potential. Test conditions including suspension concentration, sample grain size, temperature and conductivity were optimized. Then the pI (the pH value at the zero point of zeta potential) of a variety of chrome-free tanned leathers, such as mineral, vegetable, organic and combination tanned leather, were obtained by this zeta potential method. Moreover, we managed to monitor the pI and surface charge state of zirconium tanned leather during post-tanning processes using this method. As a result, application of this precise and rapid determination method enables us to reasonably regulate the pI and surface charge of chrome-free leather so as to effectively improve tanning and post-tanning performances. Note de contenu : - EXPERIMENTAL : Preparation of leather samples - Procedures for zeta potential and pI determination of leather sample - Effect of suspension concentration on zeta potential of leather - Effect of sample fiber particle size on pI of leather - Effect of temperature on pI of leather - Effect of conductivity on pI of leather - pI determination of leather tanned by a single tanning agent - pI determination of combination tanned leather - pI determination of leather from post-tanning processes - RESULTS AND DISCUSSION : Optimization of conditions for determining zeta potential and pI of leather - Application of the determination method in leather making En ligne : Pdf Format de la ressource électronique : https://www.researchgate.net/publication/318445483_Surface_charge_and_isoelectric_point_of_leather_A_novel_determination_method_and_its_application_in_leather_making Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28820 [article]

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Studies on alkaline protease from bacillus crolab MTCC 5468 for applications in leather making / Ammasi Ranjithkumar in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXII, N° 7 (07/2017)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXII, N° 7 (07/2017) . - p. 232-239 Titre : Studies on alkaline protease from bacillus crolab MTCC 5468 for applications in leather making Type de document : texte imprimé Auteurs : Ammasi Ranjithkumar, Auteur ; Jayanthi Durga, Auteur ; Ramakrishnan Ramesh, Auteur ; Victor John Sundar, Auteur ; Chellan Rose, Auteur ; Chellappa Muralidharan, Auteur Année de publication : 2017 Article en page(s) : p. 232-239 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Confitage Le confitage est une action biochimique effectuée au moyen de produits enzymatiques, qui a pour but de dégrader les fibres élastiques, contribuant ainsi à augmenter la souplesse du cuir. En outre, les enzymes complètent la dégradation des résidus épidermiques, donnant ainsi une fleur plus propre et plus lisse. Cuirs et peaux -- Analyse Cuirs et peaux de chèvres Enzymes microbiennes Peptidases Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Bating has become an indispensable operation of leather making to obtain good quality leather. Alkaline proteases are commonly used in leather manufacture in the process of unhairing and bating of hides/skins. In this study, experiments were carried out to test the bating efficacy of a new alkaline protease obtained from Bacillus crolab MTCC 5468 and compared with commercial bate. Impact of alkaline protease on porosity of enzymatically and conventionally unhaired goat skins, have been compared. New enzyme treated pelt was free from scud and pigments, with fine, clean, white, silkier grain and pliable. The result was superior to that of commercial bate treated pelts. The pore size/distribution and water vapor permeability was better than commercial bate and conventionally unhaired skins. Scanning electron microscopy and histological analysis of pelt obtained from new alkaline protease based process reveals complete removal of scud and better opening up of collagen fibers. Moreover, the collagen was not damaged and resulted in good quality of leather. The physio- chemical studies conclusively show that among the experiments, the skins unhaired with new alkaline protease was better in comfort properties than the conventionally unhaired skins as inferred by porosity measurements. Using new alkaline protease for bating led to better results than commercial bate. The study indicates improved efficiency of bacterial alkaline protease in leather processing for beam house applications. Note de contenu : - MATERIALS AND METHODS : Materials - Methods - Qualitative analysis for efficiency of bating - Analysis of unhairing and bating spent liquor - Chrome liquor analysis - Water vapor permeability measurement - Capillary flow porometry analysis - Histological analysis - Scanning electron microscopic analysis - Shrinkage temperature of the wet blue leathers - Physical and organoleptic properties of leather - RESULTS AND DISCUSSION : Qualitative analysis of bating - Protein content in unhairing and bating spent liquors - Water vapor permeability - Capillary flow porometry analysis - Scanning electron micrograph analysis - Histological analysis - Physical and organoleptic properties of leather - chrome content En ligne : https://drive.google.com/file/d/1Quyk6d9iv6UdGf9haqVeQgtytIIUdeo1/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28821 [article]

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Synthesis and properties of hydroxyl-terminated hyperbranched poly isocyanurate-ester retanning agents / Ren Long-Fang in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXII, N° 7 (07/2017)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXII, N° 7 (07/2017) . - p. 240-249 Titre : Synthesis and properties of hydroxyl-terminated hyperbranched poly isocyanurate-ester retanning agents Type de document : texte imprimé Auteurs : Ren Long-Fang, Auteur ; Zhao Yong-Xia, Auteur ; Zhang Hua, Auteur Année de publication : 2017 Article en page(s) : p. 240-249 Note générale : Bibligor. Langues : Américain (ame) Catégories : Chromatographie sur gel Cuirs et peaux -- Propriétés mécaniques Essais dynamiques Fourier, Spectroscopie infrarouge à transformée de Polyisocyanurate ester Polymères -- Synthèse Polymères à terminaison hydroxyle Polymères ramifiés Résonance magnétique nucléaire Retannage Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : AB2 monomer was synthesized by Michael addition of diethanolamine (DEA) and methyl acrylate (MA). Then the hydroxyl-terminated hyperbranched poly isocyanurate-ester with different generations (HPICEs) which were named as HPICE-I, HPICE-II and HPICE-III, were prepared respectively via three-(2-hydroxycthyl) isocyanurate (THEIC) and AB2 monomer in which THEIC was used as the core and AB2 monomer as the branching unit. The structure and mass of HPICEs were characterized by Fourier Transform Infrared Spectra (FT-IR), nuclear magnetic resonance hydrogen spectra (•H-NMR) and gel permeation chromatography (GPC). HPICEs were applied in the retanning process of wet blue leather. The results show that when the dosage of HPICEs retanning agent is 3% (basing on the weight of wet blue leather), the properties of leather retanned with HPICE-III are the best compared with those retanned with HPICE-I and HPICE-II. The thickening percentage of the back and belly were 14.88% and 20.54%, respectively. Compared with that of leather retanned with RST, a kind of acrylic retanning agent widely used in the market, the tearing strength, tensile strength and cracking strength of the leather retanned with HPICE-III are increased by 53.31%, 65.69% and 85.28% respectively. All the leather samples retanned by HPICEs exhibited better dry rub fastness but worse wet rub fastness than that retanned by RST. In addition, the samples present better surface properties as well. Note de contenu : - EXPERIMENTAL : Materials - Instruments - Synthesis of HPICE - Solid content testing - Solubility testing - the pH testing - Fourier Transform Infrared Spectroscopy (FT-IR) - Nuclear magnetic resonance hydrogen spectra (1H-NMR) - Gel permeation chromatography (GPC)1 - Retanning procedure - Test of thickening percentage - Test of tensile strength, tearing strength and cracking strength - Test of dry and wet rub fastness - Organoleptic properties of retanned leathers - RESULTS AND DISCUSSION : HPICEs characterization solubility - FT-IR analysis - H-NMR analysis - GPC analysis - Result of thickening percentage - Results of tensile strength, tearing strength and cracking strength - Results of dry and wet rub fastness - Optimization of the dosage of HPICE-III - Organoleptic properties En ligne : https://drive.google.com/file/d/1nOroC3Fpkwkl71cCtSTxUZxAk9CISNYA/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28822 [article]

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Controlling Cr(VI) in leather : A review from passive prevention to stabilization of chromium complexes / Chen Jing in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXII, N° 7 (07/2017)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXII, N° 7 (07/2017) . - p. 250-257 Titre : Controlling Cr(VI) in leather : A review from passive prevention to stabilization of chromium complexes Type de document : texte imprimé Auteurs : Chen Jing, Auteur ; Zhou Nan, Auteur ; Wuyong Chen, Auteur ; Sun Shiyu, Auteur Année de publication : 2017 Article en page(s) : p. 250-257 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Cuir -- Teneur en chrome hexavalent Cuir -- Teneur en chrome trivalent Stabilisants (chimie) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The Cr(VI) content in leather has garnered much attention in today's world of increasingly stringent environmental and safety regulations. In addition, the European Union (EU) countries have zero tolerance policies. For chromium-tanned leather, there is a risk of converting trivalent chromium into the hexavalent form in the processes of production, storage, transportation and usage. In this article, the routes for the occurrence of Cr(VI) are briefly analyzed, and the various types of Cr(VI) control technologies in leather manufacturing processes are reviewed. One control technology is passive PREVENTION, which could inhibit the hexavalent chromium to some extent through the addition of antioxidants and reducing agents, but it might not fundamentally solve the hexavalent problem. In contrast, CONSOLIDATION technologies to improve the stabilization of chromium complexes could play critical and responsible roles to effectively prevent the emergence of hexavalent chromium in leather. Several proposals are addressed for the control of Cr(VI) in leather, and CONSOLIDATION technology is determined to be more important than PREVENTION technology. In addition, a new viewpoint is presented to completely solve the problem based on the stability of Cr3+ complexes. Taking the amount of Cr(VI) as a quantitative indicator, the mechanisms and key technologies for the effect of specific coordinating compounds (ligands) on the stability of Cr3+ to prevent Cr(VI) formation would be recommended for further study toward. Note de contenu : - PASSIVE PREVENTION OF CR(VI) : Sulfur compounds and small molecule phenols - Vegetal tanning extracts - Other natural polymers - STABILIZATION OF CHROMIUM COMPLEXES : Small molecule compounds - High-molecular-weight polymers - Others En ligne : https://drive.google.com/file/d/1mYL7N8y2yVBPby2QOd5E34CzIFGOwrbS/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=28823 [article]

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