Propiedades químicas, color y humectabilidad de partículas de Laureliopsis philippiana (tepa) con y sin tratamiento térmico

Abstract

El propósito de este trabajo fue determinar el efecto de un tratamiento térmico, en una atmósfera saturada de vapor de agua, en partículas de madera de la especie Laureliopsis philippiana. Las partículas fueron tratadas en autoclave a 150 ºC por 90 minutos y a una presión de 430 kPa, la cual se generó durante el proceso por la evaporación del agua en el autoclave herméticamente cerrado. Se determinaron la cantidad de extraíbles en soda, etanol tolueno, agua caliente y fría, así también, los porcentaje de celulosa, holocelulosa y lignina, el valor pH, los porcentajes de ácidos volátiles y solubles en agua, y la capacidad tampón, tanto para partículas sin tratamiento como con tratamiento. Para las partículas con tratamiento térmico, se encontró un aumento en el porcentaje de extraíbles, de celulosa, y de ácidos volátiles y lavables, así como también, un aumento de la acidez y de una mayor capacidad tampón, en comparación con las partículas sin tratamiento. El tratamiento térmico produjo un cambio de color en las partículas y una reducción de la humectabilidad. Debido a los cambios químicos encontrados en las partículas tratadas, estas presentarían ventajas en la fabricación de tableros de partículas, favoreciendo el fraguado de la ureaformaldehído. Palabras claves:Composición química, acidez, Laureliopsis philippiana, tratamiento térmico, tableros de partículas. ABSTRACTThe purpose of this work was to determine the effect of a thermal treatment in a vapor water saturated atmosphere, on wood particles of Laureliopsis philippiana. The particles in autoclave at 150 ºC for 90 minutes and with a pressure of 430 kPa were thermally treated, the pressure generated by the evaporation of water in the sealed autoclave. The amount of extractives in soda, ethanol-toluene, cold and hot water, as well as, the percentages of cellulose, holocellulose and lignin, the pH value, the percentages of volatiles and washables acids, and buffer capacity, for both particles without and with treatment, were determined. In thermally treated particles an increase in the percentage of extractives, cellulose and volatiles and water soluble acids was found, as well as, in thermally treated particles an increment of acidity and a higher buffer capacity was found, in comparison with the particles without treatment. The thermal treatment produced a color change in the particles and a reduction in their wettability. Due to the chemical changes found in the treated particles they could present advantages in the particleboard production, allowing a better ureaformaldehyde polymerization.

Physical Properties of Boards Manufactured with Hygrothermally Treated Tepa (Laureliopsis Philippiana Looser) Particles

“…This trend is in agreement with results reported by Tomek (1966), Boonstra et al (2006) and Poblete and Peredo (1990). The increase in the amount of extractable hydrophobic compounds and the reduction in wettability in treated L. philippiana particles determined by Crespo et al (2013), could explain the changes in the physical properties. Crespo et al (2013) also reported a signifi cant reduction in the pH value (6.7 to 4.8) and an increase in acidity, which favors the adhesive setting process (UF), contributing to the improvement in physical properties.…”

“…Hsu et al (1988) reported that thickness swelling was reduced from 12.1 % to 3.6 % and linear expansion from 0.48 % to 0.24 %. In the case of boards manufactured with hygrothermally treated particles and UF, the improvement of the dimensional stability could be related to the increase in extractable hydrophobic compounds by hemicelluloses degradation, reported in hygrothermally treated L. philippiana particles by Crespo et al (2013). As reported, the increase in acidity in hygrothermally treated L. philippiana particles also contributed to an improvement in board dimensional stability, since this chemical change allows for better setting of the UF, improving the particle-adhesive-particle association.…”

“…The increase in the amount of extractable hydrophobic compounds and the reduction in wettability in treated L. philippiana particles determined by Crespo et al (2013), could explain the changes in the physical properties. Crespo et al (2013) also reported a signifi cant reduction in the pH value (6.7 to 4.8) and an increase in acidity, which favors the adhesive setting process (UF), contributing to the improvement in physical properties. The linear regression analysis showed no correlation between density, moisture content and swelling after 2 and 24 hours.…”

“…These researchers registered a reduction in both properties, indicating that the changes in the chemical composition would be the cause for the reduction. Crespo et al (2013) stated that the hygrothermal treatment increases the amount of hydrophobic compounds in hygrothermally treated L. philippiana particles and also reported an acidifi cation of treated particles, which has a positive effect on the UF setting, since L. philippiana is a species with pH values close to neutral. Both changes in the chemical composition of the particles are refl ected in a decrease of equilibrium moisture of boards.…”

Contenidos De Celulosa Y Lignina En Restos Lignino- Celulósicos De Gran Tamaño (Necromasa) En Un Bosque Templado De Antiguo Crecimiento Del Centro-Sur de Chile

“…Similar al caso anterior, tres muestras de necromasa lignino-celulósica (tres repeticiones), de N. betuloides y S. conspicua, correspondientes a cada categoría de descomposición se secaron en una estufa a 70 o C durante 8 días, hasta peso constante. La determinación de celulosa se realizó mediante el método de Kurschner & Hoffer, usado por Crespo et al (2013). Dicho método consistió en depositar 1 g de aserrín de madera seca (molido a 40 -60 mesh), libre de extraíbles (TAPPI 204 cm-97) en un Erlenmeyer y mezclar con 20 mL de etanol y 5 mL de ácido nítrico concentrado.…”