Abstract
Color change associated with significative positive improve in physical properties is a challenge in wood research. This study investigated the changes in the color of the Gmelina arborea wood which underwent a thermomechanical densification process. The process was performed by applying three different temperatures (140 °C, 160 °C and 180 °C) with thickness reduction of 20% and 40% using 2.5 MPa equivalent pressure. The color change of the pieces was analyzed through the CIEL * a * b * system. The relationship between the color and the equilibrium moisture content of the densified material was also analyzed. The process reduced the lightness and yellow hue of the wood, with increased red pigment resulting in darker coloration of the treated pieces. The higher temperature used resulted in more significant changes in wood tone and lower equilibrium moisture. The process proved to be effective to change the color and significantly reduce the equilibrium moisture content in wood samples where the density was increase by 20% and 50% compared to natural wood.
Highlights
Aesthetics factor have the important function of allowing conscious and appropriate use of lignocellulosic products, reflecting the surface characteristics of the raw material
To determine the color and its changes, can be used the system CIEL*a*b*, which uses colorimetric parameters such as: luminosity (L*), chromatic coordinates of green - red (a*) and yellow - blue (b*) axes, color saturation (C*) and hue angle (h) for evaluation and description of color shades on surfaces
The present study aimed to evaluate the superficial color changes and their relationship with the equilibrium moisture content of Gmelina arborea Roxb, submitted to thermomechanical densification process
Summary
Aesthetics factor have the important function of allowing conscious and appropriate use of lignocellulosic products, reflecting the surface characteristics of the raw material. The color, factor related to the aesthetics and decoration potencial of wood-based products, can the value added to the final product. Different color shades of wood of a specific species can be controlled using variations in processes that use temperature as a modifying agent, as occurs in thermomechanical densification. This process which causes changes in the chemical composition and structure of the wood cell wall, and in the properties of wood. In the case of woods, this technology makes it possible to classify to group clones with similar color chacacteristics (Moya-Roque & Marín 2011), influence of heat treatments (Cademartori et al 2014) and evaluations of the effectiveness of surface wood protections against the action of photodegradation (Yuan et al 2019)
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