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The mechanical properties of chrome tanned sheepskin. Variation of properties with position / Poulter Ward in JOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS, Vol. 50, N° 4 (04/1966)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS > Vol. 50, N° 4 (04/1966) . - p. 130-138 Titre : The mechanical properties of chrome tanned sheepskin. Variation of properties with position Type de document : texte imprimé Auteurs : Poulter Ward, Auteur ; A. G. Ward, Auteur Année de publication : 1966 Article en page(s) : p. 130-138 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cuirs et peaux -- Propriétés mécaniques Cuirs et peaux de moutons Essais dynamiques Tannage au chrome Traction (mécanique) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : The investigation of the variability of the mechanical properties of side and calf leather by Popplewell and Ward has been extended to chrome tanned sheepskin. The plastic set and stress for constant extension have been determined for strips from various positions on the tanned skin. The plastic set showed large variability between neighbouring samples. There was a tendency for strips from the belly region, tut parallel to the backbone, to give higher values of the set, on average, than elsewhere. The stress at constant extension varied systematically with position, the pattern resembling in main features that already reported for full chrome calf and side leather. The results have been related to observations of the fibre weave, as shown by the light microscope. Note de contenu : - EXPERIMENTAL : Tannage - Sampling - Conditioning - Testing - EXPERIMENTAL RESULTS : Set - Stress for 10 % and 20 % extension - Instron tensile test measurement - Appearance of sections. Fibre structure - Table 1 : Characteristics of samples for microscopie examination - Table 2 : % Set for the regions of the skin - Table 3 : Maximum and minimum stresses for 10% and 20% extension - Table 4 : Mean values of 5 strips Temperature c. 20°c. Instron machine Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35680 [article]

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The kinetics of chrome tannage-V. A possible explanation of the mode of action of glucose reduced chrome liquors / Stanley Briggs in JOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS, Vol. 50, N° 4 (04/1966)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS > Vol. 50, N° 4 (04/1966) . - p. 139-143 Titre : The kinetics of chrome tannage-V. A possible explanation of the mode of action of glucose reduced chrome liquors Type de document : texte imprimé Auteurs : Stanley Briggs, Auteur Année de publication : 1966 Article en page(s) : p. 139-143 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cuirs et peaux -- Analyse Liqueurs de tannage Masquage Tannage au chrome Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Chrome tannages on hides in the i.e.p. condition show that the period of uptake and the distribution of chromium in the leather are favourably influenced by the use of mixtures of organic acid masking salts, rather than by the use of any one alone. Note de contenu : - Table XXIV : Variation in analysis of leather by type of masking addition - Table XXV : Tannages of i.e.p. hide at 33% basicity and 0.33 gr. eq. masking agent per Cr 100% float [Cr2O3] a = 2.6 - Table XXVI : Tannages of i.e.p. hide at 42% basicity and 0.33 gr. eq. masking agent per Cr 100% float [Cr203] o = 2.6 - Table XXVII : Average effect of masking salts used alone or mixed Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35681 [article]

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The function of the basic groups of collagen in its reaction with vegetable tannins / Karl Helmer Gustavson in JOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS, Vol. 50, N° 4 (04/1966)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS > Vol. 50, N° 4 (04/1966) . - p. 144-160 Titre : The function of the basic groups of collagen in its reaction with vegetable tannins Type de document : texte imprimé Auteurs : Karl Helmer Gustavson, Auteur Année de publication : 1966 Article en page(s) : p. 144-160 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Tanins végétaux Tannage végétal Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : A resumé of investigations into the function of the basic groups of collagen in its binding of vegetable tannins is given. The main fixation of vegetable tannins by collagen is generally agreed to be of the nature of hydrogen bonding of the polyphenolic tannins to the backbone polypeptide groups of collagen. Evidence is presented for the acceptor function of the oxygen atoms of these links, partial crosslinking resulting. However, a number of findings indicate the participation of the basic protein groups in the attachment and irreversible fixation of tannins by stronger valence forces than hydrogen bonds, particularly in the case of tannins belonging to the condensed class. The fortifying of the crosslinks by this supplementary fixation of condensed tannins, in some instances quantitatively comparable with the hydrogen bonding reaction, manifests itself in several respects, compared with the effect of hydrolysable tannins Thus, the greater stability is evidenced by the hydrothermal stability, ATs, the greater resistance to proteinases (trypsin), and to hydrogen-bond breaking agents, such as urea, as well as to the detanning action of acid, alkali and degrading compounds generally. Dissimilarities in the reactions of the two classes of tannins with collagen are also discussed, and factors such as pli and temperature. The nature of the reaction of vegetable tannins with the basic protein group is not known. Electrovalent binding appears only feasible for tannins carrying the carboxyl group, mainly ellagi-tannins, in a limited pH range. Constitutionally, the condensed tannins possess the qualification of covalent binding of some of their constituents on the basic groups, quinone-like structures possibly being involved, particularly on ageing. Numerous findings are presented in support of the view that the fixation of condensed tannins, such as mimosa and quebracho, involves the formation of stable compounds of crosslinking function on the basic groups of collagen by other than a hydrogen bonding mechanism. Note de contenu : - 1. The complete inactivation of the basic groups - 2. Inactivations of the e-amino groups of lysine by diazotisation - 3. Tannin displacement by acids, and the reverse reaction - 4. Acid binding capacity of vegetable tanned collagen - 5. The pH function in tanning - 6. Degree of tannage and AT, - 7. The temperature function - 8. The binding of tannins by chromed collagen - 9. Effect of hydrogen-bond-breaking agents - 10. Detanning with alkali - 11. Resistance to trypsin - 12. Effect of fixed tannins on the isoelectric point of collagen - 13. Binding of tannins by amines - 14. Reaction of tannins with non-proteins and some prototypes - Table 1 : Fixation of tannins by collagen and collagen with its basic groups inactivated - Table 2 : Stripping of fixed tannins by 8 M solution of urea Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35682 [article]

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