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Drying of raw goat and sheepskins by heat pump : an alternative to salting / Agusti Marsal in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 81, N° 4 (07-08/1997)
[article]
Titre : Drying of raw goat and sheepskins by heat pump : an alternative to salting Type de document : texte imprimé Auteurs : Agusti Marsal, Auteur ; E. Gratacos, Auteur ; M. Portavella, Auteur Année de publication : 1997 Article en page(s) : p. 156-159 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : In wet countries, the curing of raw woolskins is carried out by salting however, this method causes problems to the tanners given the high salt content in the soaking effluents. In order to avoid this salinity problem, the curing of woolskins by drying is preferred. But in countries where climatic conditions are not adequate, hot air drying can be used, which may cause irreversible damage to the skins.
In this paper, laboratory drying trials on raw woolskin at different temperatures are reported to demonstrate the damage arising from inadequate drying conditions. In additions, some recommendations on the most suitable drying conditions are offered. Briefly, drying must be carried out under the following conditions :
. Well stretched out skins with the flesh side outwards
. Gentle air flow, at no more than 20°C, at low relative humidity.
These conditions which are rarely supplied by the climate in many countries can be easily achieved by means of a heat pump dryer.
The results of a semi-industrial drying trial on raw wollskin in a pilot plant operated by a heatpump are reported. Satisfactory drying was achieved in 20 hours using air at a temperature between 28-22°C and a relative humidity of 30-40 %.En ligne : https://drive.google.com/file/d/11m5Fao05AffbB69nqvWFfznwWB_FAnyt/view?usp=share [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8024
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 81, N° 4 (07-08/1997) . - p. 156-159[article]Réservation
Réserver ce documentGrain strain in sheepskins produced during flaying : Part 2 / E. Gratacos in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 75, N° 1 (01-02/1991)
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Titre : Grain strain in sheepskins produced during flaying : Part 2 Type de document : texte imprimé Auteurs : E. Gratacos, Auteur ; R. Costa, Auteur ; J. Sans, Auteur ; M. Portavella, Auteur Année de publication : 1991 Article en page(s) : p. 1-9 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Following on from the extensive bibliographical data survei and the section on traction and ball burst tests in part 1, part 2 deals with more intensive testing.
Data on wool pulling and tensile testing are followed by the comprehensive section on industrial slaughterhouse investigations. Part 2 concludes with final recommendations.En ligne : https://drive.google.com/file/d/1pxhJx-i-ilINLsKVlmVnDCXKAdl5KK1k/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8651
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 75, N° 1 (01-02/1991) . - p. 1-9[article]Réservation
Réserver ce documentGrain strain in sheepskins produced during flaying : Part 2 / E. Gratacos in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 75 (Année 1991)
[article]
Titre : Grain strain in sheepskins produced during flaying : Part 2 Type de document : texte imprimé Auteurs : E. Gratacos, Auteur ; R. Costa, Auteur ; J. Sans, Auteur ; M. Portavella, Auteur Année de publication : 1991 Article en page(s) : p. 1-9 Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Following on from the extensive bibliographical data survey and the section on ftraction and ball burst tests in Part 1, Part 2 deals with more intensive testing.
Data on wool pulling and tensile testing are followed by the comprehensive section on industrial slaughterhouse investigations. Part 2 concludes with final recommendations.En ligne : https://drive.google.com/file/d/1pxhJx-i-ilINLsKVlmVnDCXKAdl5KK1k/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8669
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 75 (Année 1991) . - p. 1-9[article]Réservation
Réserver ce documentGrain strain in sheepskins produceed during flaying : Part I / E. Gratacos in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 74 (Année 1990)
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Titre : Grain strain in sheepskins produceed during flaying : Part I Type de document : texte imprimé Auteurs : E. Gratacos, Auteur ; R. Costa, Auteur ; J. Sans ; M. Portavella Année de publication : 1990 Article en page(s) : p. 174-184 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Following a description of the defect and its characteristics a bibliographical review follows.
Mechanised flaying is highlighted as the culprit of the sharp increase in the number of damaged skins reported recently. Also highlighted is the need to discover, inside the slaughterhouses, the reasons for these defects.
Previous studies dealing with the physical properties of skin are also reviewed due to their relevance to the problem in question. From this review, the following conclusions have been reached :
Directional changes in the external muscle fibres of the animal's body also determine anatomical variations and changes in the collagen fibre tissue of the adjacent skin, including changes in the direction of hair follicles.
From these anatomical variations, directional and strength variations are produced in terms of values of the skin's physical resistances.
The flanks of sheepskins, due to their structure and thinness, are less resistant to damage than the central part of the skin. This resistance is even less in situations of traction parallel to the backbone rather than in those perpendicular to it.
A consignment of sheepskins from a recently mechanised slaughterhouse gave 93,5 % strained skins. Th seriousness of this damage gave rise to this extensive progrramme of study.
By contrast, a manual slaughterhouse with skilled workers was producing crack-free skins. Using these skins to measure the forces associated with grain strain produced the following results :
Forty kg of traction, parallel to the backbone and applied perpendicularly to the backbone, did not produce any cracks.
The cracks alwaysopened perpendicularly (ie. at right angles) to the line of traction, tending to be located in the flancks of the skin.
With a "large ball" burst test, the action of the slaughterman's punch was imitated, this did not crack the grain even when the skin was perforated.
Further tests were carried out consisting of manually pulling the wool which clearly showed that pulling mainly in the weak areas of the skin, would crack the grain.
Two raw skins were sub-divided into 4 cm wide strips, each of which was stretched to 20 kg, load under tensile test. Cracks only occurred in the strips of the flanks cut parallel to the backbone.
In view of these results, three flaying variations were applied in a mechanised slaughterhouse. These clearly showed that hand-easing of the skin onn all four legs, before mechanically stripping, noticeably reduces the cracks produced.
By eliminating strong pulls on the skin during hammock work and avoiding pulling the wool we believe that : even in mechanised work, total elimination of cracks can be achieved.
The study concludes by giving the following recommendations :
Don't pull the wool.
Don't strain the flanks of the skin, especially parallel to the backbone.En ligne : https://drive.google.com/file/d/1oVnrwhFVq8SQ_TY5TfyzEKD2iQ1dK7on/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=8793
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 74 (Année 1990) . - p. 174-184[article]Réservation
Réserver ce documentThe swelling of pelt at neutral pH as a result of the conditions of the previous pickle / M. Portavella in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 60 (Année 1976)
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Titre : The swelling of pelt at neutral pH as a result of the conditions of the previous pickle Type de document : texte imprimé Auteurs : M. Portavella, Auteur ; M. Soldevila, Auteur Année de publication : 1976 Article en page(s) : p. 37-45 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cuirs et peaux de moutons
Gonflement (physique)
Matériaux -- Epaisseur
pH
PicklageLe picklage consiste à faire absorber à la peau en tripe une quantité importante d'acide, en présence de sel neutre (NaCl) pour réprimer le gonflement que provoquerait l'acidité du milieu.
Température de retrait
Volumétrie (chimie analytique)Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Tanners who process pickled sheepskins which have benn stored for a long time have probaly noticed taht sometimes the pelts are liable to swell a great deal after having been returned to the pelts state (for example, after being depickled to pH 7, and thoroughly washed).
The published literature covering the deterioration produced on the skin by the preserving pickle does not refer to this swelling. There are many papers which deal with the attacks of acids (without salt) on collagen, and others which treat the acid pretreatment of collagen in order to obtain gelatin. Some of them mention that this king of acidic attack has also been observed in the presence of common salt, with the consequent swelling at neutral pH. The conditions which produce this swelling have not been studied systematically as yet.
In this paper, variations of both swelling at neutral pH and the shrinkage temperature of the pelts (Spanish sheepskins after a conventional beamhouse process) are investigated as a result of the conditions of the previous pickle (NaCl in the bath: 6 and 12°/Bé; H2SO4: 1.3 and 9% on pelt weight; temp.: 20 and 40°C and time 0, 1, 6, 8 and 34 days).
It has been found that both the degree of swelling and the decrease of shrinkage temperature depend on the conditions of the previous pickle. Both increase when the pickle action has been more intense.
Furthermore, the effects of the acidic attack produced by a strong pickle are studied specifically on: (a) variations in the percentage of swelling and shrinkage temperature at different pH values; (b) titration curves; (c) the amount of chrome taken up by the skin in a conventional tanning; and (d) physical tests of the leather obtained, measured in the Lastrometer.
Accordind to the results, and relating them to the fidings of other authors, some theoretical aspects of the possible causes of this swelling are discussed.
In conclusion, a simple method to assist the sheepskin tanner is presented. This method aids in establishing the degree of deterioration of the skins caused by the combined action of the beamhouse process and the preserving pickle. The method does not require specialised personnel or instrumments.Note de contenu : - Fig. 1 : Precentage of swelling at neutral pH as a function of pickle and storage conditions
- Fig. 2 : Shrinkage temperature of pelts as a function of pickle and storage conditions
- Fig. 3 : Precentage of swelling at different pH values
- Fig. 4 : Shrinkage temperature as a function of pH. Measurements in Na2SO4 (13° Bé°) solution
- Fig. 5 : Titrage curves
- Table 1 : Swelling precentage and shrinkage temperature of pelts as a function of pickle and storage conditions
- Table 2 : Swelling precentage as a function of pH
- Table 3 : Shrinkage temperature as a function of pH
- Table 4 : Titrage curves data
- Table 5 : Shrinkage temperature and ash precentage oh the chrome tanned leathers
- Table 6 : Thickness and physical strenght (Lastometer)En ligne : https://drive.google.com/file/d/1kVXgbu949t9Aq3hCSuO5dLUzBroZN8OU/view?usp=drive [...] Format de la ressource électronique : Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31801
in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 60 (Année 1976) . - p. 37-45[article]The swelling of pelt at neutral pH as a result of the conditions of the previous pickle / M. Portavella in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 60, N° 2 (03-04/1976)
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