[article]
| Titre : |
The many faces of aging |
| Type de document : |
texte imprimé |
| Auteurs : |
V. Candar, Auteur ; J. J. Palma, Auteur ; Y. Eryasa, Auteur ; Ivo Reetz, Auteur |
| Année de publication : |
2001 |
| Article en page(s) : |
p. 35-42 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Catégories : |
Cuirs et peaux -- Détérioration
Vieillissement
|
| Index. décimale : |
675 Technologie du cuir et de la fourrure |
| Résumé : |
Leather aging can be divided into mechanical, chemical, an dsigns of optical degradation. Mechanical degradation can be accurately followed by measuring the shrinkage of leather, the decay in shrinkage temperature, and the deterioration of tensile strength or tear resistance. Reasons for mechanical degradation can vary : dehydration, scission (the cutting or dividing) of the protein chain or partial detanning. This aging is usually not reversible -only by drastic reprocessing an the pre-aged be reached again.
Chemical changes can include the formation of hexavalent chromium, Cr(VI°, via the oxidation of trivalent chromium. However, in contrast to other forms of aging, this process is both preventable and fully reversible. Other symptoms of chemical aging are the randid odours from aldehyde and ketonic products formed by fatliquor decomposition.
Leather also changes its looks with time. yellowing, which can occur at higher temperatures or under excessive exposure to sun, indicate the formation of conjugated double bounds in fatliquor decomposition products, or in vegetable tannins. On the other hand, fading is a bleaching reaction, where the chemical structure of the dye used is changed. |
| Note de contenu : |
- THE FATLIQUOR OXIDATION PATH
- IODINE NUMBERS OF FATLIQUORS AND RATE OF AGING : The amount of fatliquor absorbed by the leather - The reactivity of the double bond
- AVOIDING FATLIQUOR OXYDATION : Oil characteristics and processing - Radival scavengers - Reducing agents
- MINIMISING Cr(VI) BY AVOIDING FREE Cr(III)
- Cr(VI) BY DIRECT OXIDATION
- Fig. 1 : Formation of radicals and of hydroperoxides by oxidation
- Fig. 2 : Deterioration of mechanical properties of the leather matrix
- Fig. 3 : Aging for sulfited fish oils with Iodine Numbers of IN 130 and IN 160 (All IN in gl/100g). Aging for 24 hours at 80°C
- Fig. 4 : Cr(VI) values for fatliquors with different absolute IN (IN abd = IN act. conc.). Aging for 24 hours at 80°C
- DOES AGED LEATHER = HIGH C(VI) ?
- Fig. 5 : Cr(VI) formation in various, air saturated crude oils.
- Fig. 6 : Effect of a radical scavenger (RS) on various types of aging. Example of sulfited fish oil. Aging for 24 hours at 80°C
- Fig. 7 : Effect of various reducing agents on aging. Aging for 24 hours at 80°C
- Fig. 8 : Effect of protective auxiliary in comparison with tara. Cr(VI) and shrinkage temp : aging for 24 hours at 80°C
- Fig. 9 : Influence of chromium retannage and washing with complex-active washing auxiliary on extractable Cr(III) and formation of Cr(VI): aging for 24 hours at 80°C.
- Fig. 10 : Aging of leather at 80°C for 24 hours : different degrees of humidity |
| En ligne : |
https://drive.google.com/file/d/1-6wBwDhrIJ6Qhy4n7fBxgAdYd5I_8WMC/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=32189 |
in WORLD LEATHER > Vol. 14, N° 8 (12/2001 - 01/2002) . - p. 35-42
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