Changes in the wood-water interactions of mahogany wood due to heat treatment

Mahogany wood (Swietenia macrophylla King) was thermally modified by heating at various temperatures. The wood-water-related parameters of the heat-treated wood, including fiber saturation point, equilibrium moisture content, moisture excluding efficiency, hygroscopic hysteresis, swelling, anti-swelling efficiency, water adsorption, and surface wettability were determined to clarify the mechanism of heat treatment to reduce wood hygroscopicity. The wood treated at a higher temperature demonstrated a more significant decrease in hygroscopicity. The reduction in hygroscopicity of the heat-treated wood was partially diminished as the moisture excluding efficiency decreased in the absorption and desorption processes caused by the changes in environmental temperature and relative humidity. The fiber saturation point (determined by nuclear magnetic resonance spectroscopy), surface free energy, and the surface wettability of wood were reduced by heat treatment, resulting in the decreased hygroscopicity of the heat-treated wood. Mahogany wood became more insensitive to the influence of moisture due to the heat treatment, and this effect was more distinct for wood treated at a high temperature.

Investigation of the fiber saturation point of tropical Brazilian wood species

The fiber saturation point (FSP) is an important parameter of wood material, related to dimensional stability and variations of mechanical performance. This paper investigated the FSP values of 15 tropical Brazilian wood species covering all strength classes of the Brazilian standard code. An additional goal was to estimate FSP value based on the wood’s apparent density. The FSP values were determined by measuring the wood specimen dimensions during moisture content reduction from the saturated state. Wood densities at 0% and 12% moisture contents and basic density were determined according to the Brazilian standard code. The average FSP for all wood species was 21.6% moisture content. Among density values, good correlations were observed, and a multivariate regression model for FSP estimation based on wood densities presented a coefficient of determination equal to 13.07%. There was no correlation between FSP and wood densities, suggesting that this parameter is almost constant regardless of the wood species.

INFLUENCE OF VAPORIZATION AND IMPREGNATION OF SILVER NANOPARTICLES ON THE DRYING RATE OF Eucalyptus pellita F. MUELL.

The aim of this study was to evaluate the effect of vaporization and impregnation of silver nanoparticles on the Eucalyptus pellita wood properties. For that, samples of three radial regions of the wood from three trees were vaporized for 12 and 24 hours and later on, they were immersed in solution of silver nanoparticles with and without application of vacuum (750 mm.Hg). Anatomical, physical and chemical analyzes of the wood were carried out in order to evaluate the effect of the treatments. The drying rate of the wood was determined in moisture bands before and after the fiber saturation point. Generally, the treatments did not modify the anatomical characteristics, permeability, and wood density in the three radial regions; however, the vaporization for 24h reduced the total extractive content in the wood. These results contributed in obtaining gains in the drying rate before and after the fiber saturation point. The effect of impregnation of nanoparticles with vacuum preceded by two periods of vaporization resulted in higher drying rates and the time of 24h stood out, resulting in the best averages among all treatments. The impregnation of nanoparticles had positive effects on the drying rate.