Effect of heat treatment on colour changes of black alder and beech veneers

Salca, Emilia-Adela; Kobori, Hikaru; Inagaki, Toru; Kojima, Yoshiyuki; Suzuki, Shuichi

doi:10.1007/s10086-016-1558-3

Cited by 37 publications

(21 citation statements)

References 32 publications

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“…The absolute values of corresponding ΔL* and ΔE* were similar in each batch, indicating that the greatest part of the colour variation was caused by lightness loss. Similar results were reported by Gonzáles-Peña and Hale (2009), Salca et al (2016), and Bekhta and Niemz (2003). The relationship between ΔL* and ML is plotted in Fig.…”

Section: Coloursupporting

confidence: 88%

Thermo-Vacuum Modification of Poplar Veneers and its Quality Control

Sandak¹,

Allegretti²,

Cuccui³

et al. 2016

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Poplar wood is commonly used for many purposes due to its easy machinability, low density, uniform light colour, and relatively low cost. Here, vacuum thermal treatment is proposed for upgrading veneers in the manufacturing of plywood panels with resulting reduced hygroscopicity, improved durability, and dimensional stability. Thirty-eight batch processes with different treatment conditions (temperature ranging from 150 to 240 °C, time from 0.5 to 22.5 h and pressure from 100 to 1000 mbar) were performed to characterize the influence of process parameters on the product properties. Samples were characterized considering their appearance (colour) and their physical (mass loss and equilibrium moisture content), mechanical (bending strength), and chemical (investigated with near infrared spectroscopy (NIR)) properties. The darkening of poplar veneers and the reduction of mechanical strength were observed with increased treatment time and intensity. Mass loss closely correlated with colour change, resulting from chemical changes in wood components. Principal component analysis (PCA) and partial least squares (PLS) were used for evaluation of near infrared spectral data. Both were correlated with several technical properties, and thus NIR allowed the simultaneous prediction of several of these properties. Both colour change and NIR could be used to optimize the thermal treatment of poplar veneers at the industrial scale and for realtime statistical process control.

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Section: Coloursupporting

confidence: 88%

Thermo-Vacuum Modification of Poplar Veneers and its Quality Control

Sandak¹,

Allegretti²,

Cuccui³

et al. 2016

BioResources

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“…Salca et al (2016) studied the effects of heat treatment on black alder and beech at 190 °C for different durations and revealed similar results. Additionally, they reported that the changes in color appeared mostly due to a reduction in lightness, which was related to the degradation of hemicelluloses during heat treatment.…”

Section: Color Changesmentioning

confidence: 73%

Effect of Treatment Duration and Clamping on the Properties of Heat-Treated Okan Wood

Hidayat¹,

Qi²,

Jang³

et al. 2016

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Effects of treatment duration and clamping during heat treatment were evaluated relative to the color and physical and mechanical properties of okan wood. Sapwood and heartwood boards from okan wood were treated with and without clamping for 1 to 4 h at 180 °C. Changes in color were mostly due to a reduction in lightness (L*) and yellow/blue chromaticity (b*). These values decreased more for longer treatment durations. Red/green chromaticity (a*) was not affected by the treatment duration. Weight loss and volume shrinkage increased with increased treatment duration. Density only slightly decreased because of a balanced reduction in weight and volume. Clamping during treatment prevented surfaces from having direct contact with the heated air, which resulted in lower weight loss and volume shrinkage than in the samples treated without clamping. Heat-treated wood absorbed less water than the control group, as suggested by the lower equilibrium moisture content and water absorption. Furthermore, the heartwood absorbed less water than the sapwood. An evaluation of the mechanical properties showed a reduction in both the modulus of rupture and modulus of elasticity after heat treatment. Clamping minimized strength reduction in both sapwood and heartwood, particularly for 1 and 2 h heat treatments.

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“…The yellowing of bleached chemical pulp proceeded during heat treatment by decay of mainly hemicellulose, which is thermally less stable than cellulose [24]. Thermal decomposition of hemicellulose and cellulose occur with high intensity at 180 and 340 • C, respectively [25]. reddened after heat treatment, probably because of formation of condensation products and degradation and/or oxidation products, such as quinone-like substances [10].…”

Section: Preparation and Color Evaluation Of Light-colored Ligninmentioning

confidence: 99%

Preparation and Application of Light-Colored Lignin Nanoparticles for Broad-Spectrum Sunscreens

et al. 2020

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Recently, natural sun blockers have been drawing considerable attention because synthetic UV filters could have adverse effects not only on humans but also on the environment. Even though lignin, the second most abundant renewable resource on earth, is a natural UV-absorbing polymer, its unfavorable dark color hampers its applications in sunscreens. In this work, we obtained light-colored lignin (CEL) from rice husks through cellulolytic enzyme treatment and subsequent solvent extraction under mild conditions and compared CEL to technical lignin from rice husks using the International Commission on Illumination L*a*b* (CIELAB) color space. Spherical nanoparticles of CEL (CEL-NP) were also prepared using a solvent shifting method and evaluated for broad-spectrum sunscreens. A moisturizing cream blended with CEL-NP exhibited higher sun protection factor (SPF) and UVA PF (protection factor) values than that with CEL. In addition, CEL-NP had synergistic effects when blended with an organic UV-filter sunscreen: CEL-NP enhanced the SPF and UVA PF values of the sunscreen greatly. However, there was no synergistic effect between CEL-NP and inorganic sunscreens. We expect nanoparticles of light-colored lignin to find high-value-added applications as a natural UV-blocking additive in sunscreens and cosmetics.

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Effect of heat treatment on colour changes of black alder and beech veneers

Cited by 37 publications

References 32 publications

Thermo-Vacuum Modification of Poplar Veneers and its Quality Control

Thermo-Vacuum Modification of Poplar Veneers and its Quality Control

Effect of Treatment Duration and Clamping on the Properties of Heat-Treated Okan Wood

Preparation and Application of Light-Colored Lignin Nanoparticles for Broad-Spectrum Sunscreens

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