Kinetic Analysis of the Color of Larch Sapwood and Heartwood during Heat Treatment

Abstract

Abstract:The kinetics of color changes in larch sapwood and heartwood during heat treatment were investigated in this study in order to determine if the process of color change that occurs in the surface of wood can be regulated. Wood samples were heated at 90, 110, 130, and 150 • C in an oven, vacuum, and in an oven subjected to saturated steam for 3, 6, 9, and 12 h each. The results of the color measurement showed that the values of L* (lightness) and ∆E* (total color difference) decreased and increased in both the sapwood and heartwood, respectively, with increasing temperature and treatment time. The three kinetic model approach, consisting of (i) the time-temperature superposition principle (TTSP); (ii) zero-order reaction model; and, (iii) first-order reaction model, was used to model the kinetics of color changes. The results indicated that the L* value of the sample (including heartwood and sapwood) was well fitted to the first-order reaction model (R 2 = 0.9999). The Arrhenius activation energy was 14.2369 and 11.0984 kJ/mol for the sapwood and heartwood, respectively. The first-order reaction model also showed a better fit for the ∆E* values between sapwood and heartwood with higher R 2 values than the other two methods. Therefore, the color changes of larch wood could successfully be analyzed using the first-order reaction model.

Functionalized Surface Layer on Poplar Wood Fabricated by Fire Retardant and Thermal Densification. Part 1: Compression Recovery and Flammability

“…Figure 1b indicates that the VDP of untreated poplar was relatively uniform throughout the thickness with an average density of 352.38 kg/m 3 . The average density of W HT decreased by 7.94% because of the thermal degradation of wood, which is consistent with some previous studies [17,22,38]. All the treated samples were divided into three regions according to the density changes; namely two surface layers (R1 and R3) and one core layer (R2).…”

Nondestructive Characterization of Dry Heat-Treated Fir (Abies Alba Mill.) Timber in View of Possible Structural Use

“…Color changes in wood during the heat treatment were found to be related to the process intensity. The excellent but non-linear negative relationship was observed between the lightness of wood (L*) and the used temperature of heat treatment, which was confirmed also in some previous studies [25,[35][36][37]. Researchers even proposed more reliable means of measuring the intensity of a thermal modification process by combining parameter L*+b* and by milling of wood, to prevent scattering of color parameters on real wood surfaces [35].…”

Effects of Thermal Aging on the Adhesion Forces of Biopolymers of Wood Cell Walls

“…7 , 8 Heat treatments at 100–150 °C were used to accelerate the oxidation process and to avoid dissimilar chemical reactions under natural aging. 8 − 16 However, the detailed mechanism of thermal oxidation is rarely addressed. 8 …”

“…The temperature influences almost every aging process in manufacturing and application of wood ranging from wood composite manufacturing to the use of wood in construction. Heat is often used as a vehicle to accelerate the aging processes of polymers, such as the application of time–temperature superposition. − For the wood material, aging under dry conditions at ambient temperature is mainly a mild oxidation process. , Heat treatments at 100–150 °C were used to accelerate the oxidation process and to avoid dissimilar chemical reactions under natural aging. − However, the detailed mechanism of thermal oxidation is rarely addressed …”