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The production of a larger variety of wood products depends on development adhesives that can be fabricated from petroleum components or from renewable sources. The use of renewable phenolic adhesives is an alternative the urea adhesives, and others derived petroleum, adhesives commonly used in the composition board making, but that present some toxicity and high cost. On the other hand, the use of adhesives originating from of natural sources, as for instance the tannins, depends on development of adhesives with better properties. This work had as main objective to modify the tannins of the eucalyptus bark chemically for the production of adhesives that could be use in the fabrication of flakeboards. The tannins were extracted with hot water, with addition of 4,5% of sulfite of sodium, for three hours, at the temperature of 70 and 100C, respectively for E. grandis and E. pellita, these conditions resulted in larger amount of extracts. For the adhesives production the tannins were reacted with acetic acid and sulfite of sodium, for a period of ninety minutes, this reaction was necessary to reduce of the viscosity of the adhesive. It was observed that the acid sulfitation of the tannins probably reduced the molecular weight and consequently their viscosity. Techniques of DSC (Calorimetric exploratory differential) were used to determine the kinetic parameters of the adhesives. It was observed that the tannics adhesives of E. pellita showed smaller enthalpy values than the adhesives tannics of E. grandis. Laboratory flakeboards of E. grandis W. Hill Ex. Maiden and Pinus elliottii, were produced using 8% of sulfited E. grandis and E. pellita bark tannins with five substitution levels (0, 25, 50, 75 and 100%) as relate a to the adhesive of commercial urea. For comparison it was also manufactured, boards with 10% of adhesives tannic. Boards properties were determined according to the norm ASTM D-1037 1993. It was observed that boards properties fabricate with tannins adhesives were lisher the minimum than extablishe by commercial normal ANSI/A 208.1-93, except for the humidity properties. Results demonstrated the potential Eucalyptus tannins for production of adhesives for interior composition boards, where the resistance to the humidity is not critical. Based these results, measures and/or treatments are recommended to seek the reduction of absorption of water, Is is also suggested the substitution of the tannin adhesive in the phenol base, since these adhesives are resistant to the humidity.

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Autor(es)

Angélica de Cássia Oliveira Carneiro - 

Id.: 28451553

Idioma: portugués  - 

Versión: 1.0

Estado: Final

Tipo:  PDF - 

Palabras claveAdhesives for wood - 

Tipo de Interactividad: Expositivo

Nivel de Interactividad: muy bajo

Audiencia: Estudiante  -  Profesor  -  Autor  - 

Estructura: Atomic

Coste: no

Copyright: sí

Formatos:  PDF - 

Requerimientos técnicos:  Browser: Any - 

Fecha de contribución: 25-jun-2010

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