Effects of Heat Treatment on the Color Change and Dimensional Stability of Gmelina arborea and Melia azedarach Woods

Abstract

This study aimed to improve the color properties and dimensional stability of gmelina (Gmelina arborea) and mindi (Melia azedarach) woods via heat treatment. Heat treatment was conducted using an electric furnace at 180°C and 210°C for 3 h, with a heating rate of 2°C/min. Wood samples were stacked with and without metal clamp. The effectsof temperature and clamping during heat treatment on the color change and dimensional stability were evaluated. The evaluation of color change was performed using the CIE-Lab color system and the evaluation of dimensional stability was conducted by measuring the equilibrium moisture content and water absorption. The results showed that the overall color changes(ΔE*) in gmelina and mindi woods were mainly affected by the reduction in lightness (L*) due to heat treatment. The ΔE*increased with increasing treatment temperature, with a higher degree obtained in gmelina wood. Application of metal clamp during treatment limited the exposure of wood surface to the heated air, resulting in lower value of ΔE* than the samples without metal clamp. Dimensional stability of gmelina and mindiwoods improved by heat treatment, showing lower equilibrium moisture content and water absorption than the untreated woods. Furthermore, heat treated mindi absorbed less water than gmelina. The results suggested that heat treatment could enhance the color properties and dimensional stability of gmelina and mindi woods for value added products.