433 research outputs found
Reduction of the formaldehyde content in leathers treated with formaldehyde resins by means of plant polyphenols
Formaldehyde has applications in many industrial processes, including synthesis of resins and syntans to be used in the retanning process of leather. When resins are employed, they can hydrolyse, releasing formaldehyde. Due to the carcinogenicity of formaldehyde, its presence in leather should be avoided or kept below allowable limits.
The aim of this study is to determine the effect of polyphenols contained in vegetable compounds (mimosa, quebracho and tara) in the reduction of the formaldehyde content in leathers treated with resins synthesized with formaldehyde (melamine-formaldehyde and dicyandiamide-formaldehyde). The formaldehyde content in leathers treated only with resin increases with time while the formaldehyde content in leathers treated additionally with vegetable compounds is reduced. The lower the formaldehyde content in the leather, the higher the ability of vegetable compounds to reduce such content. Mimosa shows the strongest ability to reduce the formaldehyde content, and this capacity increases with ageing. The addition of 4% (on shaved wet-blue weight) of mimosa gives rise to an 85% reduction in the formaldehyde content 140 days after leather processing of split hides treated with a formaldehyde resin of low formaldehyde content. However, this reduction is 68% in splits hides treated with a resin of high formaldehyde content. This is of great importance in baby’s leather articles, in which the formaldehyde content is low; therefore, the addition of a small amount (3%) of vegetable compounds (especially mimosa) guarantees that the formaldehyde content is below the allowed limits (16 mg/kg in the most restrictive regulation). Reducing the formaldehyde content using the polyphenols contained in vegetable compounds constitutes a good alternative not only in the leather sector but also in other industrial sectors (wood, textile, etc.) that use formaldehyde resins.Peer ReviewedPostprint (published version
Calcul des doses d'irrigation pour les sols salés : application d'une méthode géochimique de calcul à un sol tunisien
La méthode de prévision du volume de lessivage recommandée par la FAO (méthode classique) néglige la précipitation des minéraux à partir de la solution du sol. La méthode dite géochimique prend en compte ces phénomènes par le biais d'un modèle thermodynamique. L'application de ces deux méthodes à la station de Cherfech en Tunisie permet de comparer leur validit
Ricard FarrĂ© Climent: alcalde republicĂ de l'Espluga de FrancolĂ, afussellat pel franquisme (1894-1939)
DescripciĂł del judici militar de les autoritats franquistes contra l'industrial espluguĂ Ricard FarrĂ© i la seva esposa Rosa Tarrats, el primer, el 1931 havia estat escollit democrĂ ticament alcalde de la seva vila, abans s'aporten les seves dades biogrĂ fiques, en especial la seva activitat polĂtica, quan secularitzĂ el cementeri municipal. L'autor resumeix les declaracions jurades dels testimonis davant els jutges militar i municipa
Taller de geofĂsica : geomagnetisme
El magnetisme i en particular el camp magnètic de la Terra s'ensenya als alumnes des de la primĂ ria fins al batxillerat en diferents moments i amb un aprofundiment progressiu. Aquest article pretĂ©n complementar l'estudi del camp magnètic al batxillerat amb una acti-vitat prĂ ctica sobre una tempesta magnètica enregistrada a l'Observatori de l'Ebre. El treball consta d'una introducciĂł als conceptes bĂ sics que permeten comprendre el camp geomagnètic, les tempestes magnètiques i l'enregistrament que se'n fa en un ob-servatori magnètic. L'objectiu final serĂ donar una mesura de l'activitat magnètica. La re-soluciĂł d'un qĂĽestionari ajudarĂ a reforçar aquests conceptes i facilitarĂ la mesura dels Ăndexs d'activitat magnètica
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