Particle size evolution of chrome tanning agent on tanning effect / Yahui Wang in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXIV, N° 8 (08/2019)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXIV, N° 8 (08/2019) . - p. 279-286 Titre : Particle size evolution of chrome tanning agent on tanning effect Type de document : texte imprimé Auteurs : Yahui Wang, Auteur ; Haojun Fan, Auteur ; Yi Chen, Auteur ; Jun Yan, Auteur Année de publication : 2019 Article en page(s) : p. 279-286 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Croûte (cuir) On entend par "cuir en croûte" des cuirs ayant subi les opérations jusqu'au tannage, à l'exclusion de toute opération de corroyage ou de finissage, mais qui, par opposition aux wet-blue ont été séchés. pH -- Mesure Stabilité hydrothermale Taille des particules Tannage au chrome Température Température de retrait Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : In a traditional method of chrome tanning, the particle size (PS) of tanning agent is critical for its penetration and the performance of resultant leather. The temperature, pH value and concentration of chrome solution are the important parameters to influence the size scale of the chromium complex. In present study, the PS evolution of chrome tanning agent (CTA) with pH value and temperature changes was investigated firstly, then the influence of the evolution of PS on the tanning process and hydrothermal stability of crust leather was also investigated. The results indicated that with the temperature varied from 25°C to 30°C and 35°C, the pH of the chrome solution increased from 2.5 to 3.8, the PS of CTA increased from 982 nm to 2899 nm, 1265 nm to 3384 nm and 1289 nm to 3630 nm, respectively, showing a rapid increasing tendency. Correspondingly, due to the PS of CTA increased, the chromium absorption rate increased from 31.0% to 53.6% at 25°C, 33.8% to 55.9% at 30°C and 34.5% to 56.4% at 35°C, whilst the uniformity of the chromium distribution in crust leather was gradually reduced. At the same initial tanning temperature, the shrinkage temperature (Ts) of wet blue tend to increase first and then decrease with the increase of the CTA’s PS, and reached above 100°C when the PS was in a range from 2000 nm-2700 nm. As the PS continues to increase, the inner layer was insufficient tanned due to excessive tanning of surface, leading to a decrease in hydrothermal stability of crust leather. Note de contenu : - EXPERIMENTAL : Materials - Preparation chrome tanning solution with different pH value - Particle size measurement - Tanning trial - Property assessments of tanned leathers determination of chromium concentration in spent tanning solutions - Determination of chromium content and distribution in tanned leathers - Shrinkage temperature of tanned leathers - RESULTS AND DISCUSSION : Evaluations PS of CTA with pH and temperature - The effect of PS on absorptivity of chromium - Effect of PS on chromium distribution in tanned leathers - Hydrothermal stability of tanned leathers En ligne : https://drive.google.com/file/d/1FFPGoUDxNCsOlGVOtl9FbehxOfxCTAjU/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=32787 [article]

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Particle size evolution of melamin-formaldehyde tanning agent on tanning effect / Mengmeng Chen in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXIII, N° 5 (05/2018)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXIII, N° 5 (05/2018) . - p. 151-162 Titre : Particle size evolution of melamin-formaldehyde tanning agent on tanning effect Type de document : texte imprimé Auteurs : Mengmeng Chen, Auteur ; Yahui Wang, Auteur ; Haojun Fan, Auteur ; Yi Chen, Auteur ; Jun Yan, Auteur ; Yu Liu, Auteur Année de publication : 2018 Article en page(s) : p. 151-162 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Agents de tannage Copolymère mélamine-formaldéhyde Cuirs et peaux -- Propriétés mécaniques Polycondensation Stabilité hydrothermale Taille des particules Tannage organique Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Melamine-formaldehyde [MF] resin is a tanning agent. Its average particle size [PS] is important for penetrating the skin and thus endowing performance of its resultant leather. The synthesis parameters for MF resin such as pH, molar ratio of formaldehyde to melamine, temperature and reaction time affect its PS. We investigated in detail the growth of MF’s PS and its consequent effects on hydrothermal stability, mechanical properties and the apparent properties of leather. The data showed that a broad range of average PS was formed at the different synthesis stages of MF resin. For example, the first reaction stage of methylolation gave an average particle diameter of 250 nm with a narrow size distribution under the conditions of 45°C, 3:1 molar ratio, a pH of 8.5, and a reaction time of 3 hrs. In this case the resultant leather was poor as it had a low shrinkage temperature, lacked fullness and showed a low-valued elongation at break. During the second polycondensation stage, the PS of MF resin increased with increasing reaction temperature and the molar ratio of formaldehyde to melamine. Furthermore, PS increased more rapidly by lowering the pH of the polycondensation and extending its reaction time. Thus, the new average diameter of MF resin particles reached above 3000 nm when the polycondensation reaction was done inside the skin for 2 hours at a pH of 4.5. Consequently, the resultant leather was white and full. It had a high hydrothermal stability and mechanical strength as evidenced by its fully satisfactory elongation at break. Clearly, the cross-links were formed by multiple site interactions between MF resin with large PS and collagen fibers, which enhanced the tanning effect. Note de contenu : - EXPERIMENTAL : Materials - Reaction of melamine and formaldehyde - Tanning trial - Assessment of properties of tanned leathers - RESULTS AND DISCUSSION : Parameters affecting the particle size of MF resin tanning agent - The effect of tanning agent's PS on properties of tanned leather En ligne : https://drive.google.com/file/d/1nqOi07mAnm5Xjiy0M0yrCKEJqM67qm-7/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30533 [article]

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