Anales CIDEPINT 1997-98
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Examinando Anales CIDEPINT 1997-98 por Autor "Benítez, Juan C."
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Acceso Abierto Extraction and characterisation of quebracho (Schinopsis sp.) tannins(1998) Tonello, M. L.; Giúdice, Carlos A.; Benítez, Juan C.Vegetables tarmins are organic substances; when considering the great number of different tarmins, it is possible to State certain properties which are common to all of them such as: a high molecular weight, causing colloidal Solutions in which the particles of tarmins are present in all forms of dispersions; a great number of free hydroxy phenolic groups, which are mainly responsable for the solubility of tannins in water; with few exceptions, all tarmins are amorphous and no crystalline; a different degree of acidity resultant from the polarity of the hydroxy phenolic groups which in some cases is enhanced by free carboxyl groups; tarmins formed by esterification of carboxyl groups usually exhibit a higher acidity than those made by condensation or polymerisation of components free from carboxyl groups; formation of intense precipitates in the presence of soluble iron (III) salís, etc. This last property of the tarmins, that is the capacity of forming chelates with the hexahydrated iron (III) ion, could be employed efficiently to modify the kinetic of oxidation of iron and Steel substraía. In this paper, the extraction, the purification, the concentration and the characterisation of tannins obtained from quebracho (Schinopsis sp.) were performed, particularly with the objective of knowing some inherent properties to the reaction between the tarmins and the iron. - Artículo
Acceso Abierto Manufacture and testing of water-based tannic pretreatments(1998) Giúdice, Carlos A.; Benítez, Juan C.; Tonello, M. L.The anticorrosive efficiency of the different coating systems depends to a great extent on the initial State of the metallic surface, since the best paints do not insure a lengthy protection when they are applied over a structure that is not adequately prepared In consequence, at present the treatment of the corroded surfaces continúes being a great challenge in spite of the modem existing methods, specially when the conditions do very expensive the total removal of oxides or is not practicable by diverse motives. In a previous work, the purification and the characterisation of tannins extracted from the heartwood of quebracho (Schinopsis sp.) were performed particularly with the objective ofknowing some inherent properties of the reaction between the tannins and the iron oxides. In the present work; severa1 water-based tarmic pretreatments acidified with orthophosphoric acid were formulated and manufactured at laboratory scale; results of tests carried out allowed to conclude that the application of the quoted tannic Solutions on a substratum with a mechanical preparation insufftcient to eliminóte the totality of the producís of corrosión, increased the useful Ufe of the applied coating system, delaying oxidation and in consequence the deterioration of the subsequent paint films. - Artículo
Acceso Abierto Phosphorus-based intumescent coatings(1998) Benítez, Juan C.; Giúdice, Carlos A.Fire is an energetic manifestation which carnes undesirable consequences due to the problems that it originates. The conflagration is a disagreeable fací produced by fire. The main objective of a fireproofing treatment is to make a material hardly flammáble or autoextinguishable. An ejficient fireproofing effect interrupts the combustión in one or more stadiums, leading the process to end in a reasonable period (preferably before ignition occurs). Intumescent coatings, as a means of passive protection against firet perform a fundamental role in this matter. Dry films of these paints, submitted to fíame action, softens in a first stage and then swells due to an intemal and partial loosing of non combustible gases, reaching up to 200 times of its original thickness. The charred coat, an incombustible spongy mass, protects the painted material’ delays the temperature increase and avoids the access of air, and so the combustión. By means of intumescent coatings, different materials such as paper, wood, pasteboard, plastics, metáis, etc. can be protected The objective of this paper was to study the influence of some formulation variables of phosphorus-based intumescent coatings, formulated and manufactured for this experiment. Chlorinated rubber coatings based on ammonium polyphosphate, pentaerythritol, melamine, 42 % chlorinatedparaffin and an endothermic filler showed very high performance after ageing. - Artículo
Acceso Abierto Tin tannates and iron tannates in corrosion-inhibiting coatings(1998) Giúdice, Carlos A.; Benítez, Juan C.; Tonello, M. L.The efficiency of the coating systems in the protection of metallic substraía depends fundamentally, in relation with formulation variables, on the type and contení of corrosion-inhibitive pigment, the characteristics of the film forming material and the pigment / binder ratio in volume. Conceming the pigment, there is not doubt that the use of some inhibitors in anticorrosive paints is actually an important source generating toxicity problems both for the worker andfor the environment. This problem is extended to the applicator and álso to the removal operation of oíd coatings. In this research tin tcamates and iron tannates were employed as inhibitive pigments in anticorrosive paints. The mentioned metallic tannates were prepared on laboratory scale under controlled operative conditions, carrying out the reaction between the metallic ions and the polyphenolic groups of condensed tannins extracted from “quebracho ” heartwood (Schinopsis sp.).