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Is spectrophotometry a reliable technique for determination of Cr(VI) in leather samples ? / R. Milacic in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 82, N° 3 (05-06/1998)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 82, N° 3 (05-06/1998) . - p. 91-94 Titre : Is spectrophotometry a reliable technique for determination of Cr(VI) in leather samples ? Type de document : texte imprimé Auteurs : R. Milacic, Auteur ; J. Scancar, Auteur ; M. Urbanc, Auteur Année de publication : 1998 Article en page(s) : p. 91-94 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Chromium (VI) in coloured and non-coloured leather samples was determined by the standard spectrophotometric procedure DIN 53314 and also by extraction of the chromium (VI)-HC1 complex (277 K) into methyl isobutyl ketone (MIBK). Chromium (VI) was determined in the organic phase by flame atomic absorption spectrometry (FAAS). Both techniques were found to be sensitive enough for the determination of chromium (VI) in the samples analysed. The limit of detection for the spectrophotometry was 2.0 mg Cr(VI) kg-1 and for MIBK extraction 0.2 mg Cr(VI) kg-1 of leather. The interference effects of coloured species in leather extracts were investigated by employing the spectrophotometric technique. For this purpose diluted and non-diluted sample extracts were analysed. The results obtained were critically evaluated and compared to the MIBK extraction technique. The applicability of the spectrophotometric procedure for determination of chromium (VI) in coloured leather samples was estimated. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=7900 [article]

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Lime-free unhairing : Part 2 / Virgilijus Valeika in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 82, N° 3 (05-06/1998)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 82, N° 3 (05-06/1998) . - p. 95-98 Titre : Lime-free unhairing : Part 2 : Influence of added salts on NaOH unhairing and on hide properties Type de document : texte imprimé Auteurs : Virgilijus Valeika, Auteur ; J. Balciuniene, Auteur ; Kestutis Beleska, Auteur ; A. Skrodenis, Auteur ; V. Valeikienè, Auteur Année de publication : 1998 Article en page(s) : p. 95-98 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The influence of the system containing NaOH, Na2S and a salt such as NaCl, Na2SO4, HCOONa or Na2HPO4 on the properties of pelt in the unhairing process was investigated. The process of unhairing was separated into two stages : (i) degradation of the hair and (ii) opening up the dermal structure. The opening up stage was carried out in the liquor from the hair degradation after dilution with water. It was established that the above salts added to the solution for opening up the dermal structure influence the kinetics of the removed collagen and non-collagen proteins and also swelling of the hide. The supplementary use of salts is not convenient because it is more convenient to regulate the properties of the pelt by using a suitable quantity of water in the opening up the stage. The technology of lime-free production of pelt was developed based on the results of these investigations. Application of this technology of lime-free production of pelt was developed based on the results of these investigations. Application of this technology showed that the quality indexes of the garment leather produced using this method meet the manufacturer's requirements. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=7901 [article]

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The Seymour-Jones lecture. IULTCS congress 1997 - How, why and who / Graham Lampard in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 82, N° 3 (05-06/1998)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 82, N° 3 (05-06/1998) . - p. 99-103 Titre : The Seymour-Jones lecture. IULTCS congress 1997 - How, why and who Type de document : texte imprimé Auteurs : Graham Lampard, Auteur Année de publication : 1998 Article en page(s) : p. 99-103 Note générale : Bibliogr. Langues : Anglais (eng) Tags : Cuir  Tannage  chrome  (III)  synthétique  Terres  rares  Ultrason  Séchage  cuir  Temps  réhydratation Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The IULTCS Congress was held in London from 11-14 september 1997. This paper discusses some of the lectures and posters given at the congress and suggests an alternative process for the 21st century. This will include controlled drying, gaseous pickling, totally synthetic tannages or chromium (III) tannages with its efficacy by rare earth elements, and power ultrasound to speed up processing times. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=7902 [article]

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Collagen : a not so simple protein / A. J. Bailey in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 82, N° 3 (05-06/1998)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 82, N° 3 (05-06/1998) . - p. 104-110 Titre : Collagen : a not so simple protein Type de document : texte imprimé Auteurs : A. J. Bailey, Auteur ; R. G. Paul, Auteur Année de publication : 1998 Article en page(s) : p. 104-110 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Collagène Cuirs et peaux Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Collagen is the major protein of animal bodies from simple sponges to homo sapiens and exists in various froms from skin, tendon and bone to cornea and basement membrane of the capillaries. This biological variation can now be accounted for on the basis of a whole family of genetically distinct collagens. OVer the past two decades 19 different collagens have been identified, although the major types are the fibrous types I, II and III and the non-fibrous type IV of basement membrane. They all possess the basic triple helix based on multiple repeats of the simple tri-peptide Gly-W-Y, but this varies in length and forms different supramolecular aggregates to achieve optimum function for particular tissues. The major function of collagenis to provide shape and mechanical strength and the latter is achieved by intermolecular crosslinking of the collagen molecules in the supramolecular aggreate. The monomeric molecules in the aggregates are stabilised by two different pathways. Initially cross-linking occurs through an enzymic mechanism involving oxidation of specific lysine and hydroxylysine residues providing divalent cross-linking which subsequently matures to multivalent cross-links. As the rate of turnover decreases a non-enzymic pathway takes over, which is mediated throug the adventitious accretion of glucose. Collagen therefore, unlike other proteins shows considerable changes with age which in turn affect its physical properties. These changes must be taker into accoung when preparing collagen based products ? All the amino acid side chains project radially for the rod-like triple helix and the quarter-staggered array of the molecules allows highly specific intermolecular cross-linking either naturally, or artificially with bifunctional reagents. Reactions with basic or acid groups can therefore be carefully controlled and in some case their location predicted. Synthetic cross-links bind the molecules closer together and increase intermolecular interactions, thus increasing the shrinkage temerature and resistance to enzymic degradation. The turnover of collagen is generally slow but in fact can vary from 2/3 days for periodontal ligament to several years for skin and tendon. Mature collagen fibres arehighly resistant to enzymes and degradation is achieved by specific collagenase that can cleave the triplehelix at one particular point. The shorter helical fragments can then unravel and denature to gelatin when ogher metalloproteinases (MMPs) degrade it to amino acids. A family of 14 metalloproteinases have been identified along with some specific tissue inhibitors (TIMPS). The sharp denaturation temperature of collagen attests to the almost crystalline character of the triple helix and the variation in shrinkage temperature between species is primarily due to the number of hydroxyproline based water hydrogen bridges. The presence of a hydroxyproline deficient thermally labile domain near the carboxy terminus of the molecule initiates the melting process allowing the triple helix to unzip along its length. Recent studies have demonstrated that collagen is not an inert structural material but interacts with other molecules to control the development of collagenous tissues. Despite the ancient lineage of this ubiquitous protein, collagen is still revealing exciting new scientific features. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=7903 [article]

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Clean technologies, targets already achieved and trends for the coming years / R. Augusto in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 82, N° 3 (05-06/1998)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 82, N° 3 (05-06/1998) . - p. 111-113 Titre : Clean technologies, targets already achieved and trends for the coming years Type de document : texte imprimé Auteurs : R. Augusto, Auteur ; Moraes Maia, Auteur Année de publication : 1998 Article en page(s) : p. 111-113 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The leather industry, as well as most other potential polluters is continuing to improve its environmentally friendly procedures inproportion to the regulatory legislation. As a result of such problems, even more emphasis has been given to clean technologies and waste reduction. Nowadays nearly every part of the tanning process has several cleaner or environmentally friendlier alternatives that have been discussed in seminars and workshops, tested in pilot scale and even adopted by some tanneries. Worldwide, many experiences in full scale have been related considering the usage of these procedures which are also being adopted in Brazil. Among these applications we would mention a chromium-free tanning using combinations of metallic cations, such as aluminium, titanium and zirconium, post-tanning operations free from chromium during retanning. Of environmentally risky dyestuffs, of benzidine in dyes, of halogenated oils in fatliquors which are also related. The substitution of organic solvents by water and pigments free from environmental risky heavy metals are clean improvements in finishing operations. The well-known procedures of chromium recovery, lime recycling and the substitution of ammonia salts by CO2 during deliming, are exemplified with figures relating to current Brazilian conditions. In the coming years, research must be concentrated at an early stage before application on an industrial scale, by means of a partnership between the research centers and the industries which supply the chemical products, so that more viable options can be offered to tanneries. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=7904 [article]

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Studies on the application of recovered chromium in chrome tanning / J. R. Rutkowski in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 82, N° 3 (05-06/1998)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 82, N° 3 (05-06/1998) . - p. 114-116 Titre : Studies on the application of recovered chromium in chrome tanning Type de document : texte imprimé Auteurs : J. R. Rutkowski, Auteur ; K. Kosinska, Auteur ; M. Urbaniak, Auteur Année de publication : 1998 Article en page(s) : p. 114-116 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Research work was carried out on recovered chrome tannin application in the processing of unsplit cattls hide tanning. In these experiments 20-80 % of "Regenerate" was used in individual trials of tannings with chromal. Taking into consideration the tannin content in spent tanning floats from tanning trials with a changing share of "Regenerate", statement can be made that with an increase in the "Regenerate" share, negligible deterioration of its exhaustion occurs. The general content of tannin in wet-blue from tanning trials with different shares of recovered chrome liquor remains on the level of 4.0-4.4 % Cr2O3 and shows a falling tendency with the increasing share of "Regenerate". In additiona disadvantageous effect of a different tannin distribution in the cross-section of the leather was confirmed. The content of CrO3 in the middle layer decreases with the increase in the "Regenerate" share. Distinct deterioration of both indicators, i.e. total chromium content and its distribution in the layers of the leathers tanned exclusively with "Regenerate" was observed. The physical test results of garment leather and footwear leather showed that all the leathers from tanning trials with a partial use of "Regenerate" comply with the Polish Standards for the parameters needed for quality leathers. Each time the leathers tanned with 100 % "Regenerate" stood out from the others : garment leather with the highest tear strength values and the lowest elongation, footwear leather with the lowest strength values, the lowest extension at burst and the lowest elongation at break. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=7905 [article]

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