Changes of Meranti, Padauk, and Merbau Wood Lignin during the ThermoWood Process

Kačíková, Danica; Kubovský, Ivan; Gaff, Milan; Kačík, František

doi:10.3390/polym13070993

Cited by 6 publications

(5 citation statements)

References 65 publications

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“…The application of a natural flame retardant at lower temperatures has a very similar effect to that of thermally modified wood, deteriorating significantly at 180 and 210 °C, i.e., the maximum burn rate values increase. While, in this case, the effect of the thermal modification proved to be statistically insignificant (as in published works [ 44 , 45 , 47 ]), the effect of thermal modification of oak wood on the maximum burn rate was found to be statistically significant.…”

Section: Resultssupporting

confidence: 61%

Flammability Characteristics of Thermally Modified Meranti Wood Treated with Natural and Synthetic Fire Retardants

et al. 2021

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This paper deals with the effect of synthetic and natural flame retardants on flammability characteristics and chemical changes in thermally treated meranti wood (Shorea spp.). The basic chemical composition (extractives, lignin, holocellulose, cellulose, and hemicelluloses) was evaluated to clarify the relationships of temperature modifications (160 °C, 180 °C, and 210 °C) and incineration for 600 s. Weight loss, burning speed, the maximum burning rate, and the time to reach the maximum burning rate were evaluated. Relationships between flammable properties and chemical changes in thermally modified wood were evaluated with the Spearman correlation. The thermal modification did not confirm a positive contribution to the flammability and combustion properties of meranti wood. The effect of the synthetic retardant on all combustion properties was significantly higher compared to that of the natural retardant.

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Section: Resultssupporting

confidence: 61%

Flammability Characteristics of Thermally Modified Meranti Wood Treated with Natural and Synthetic Fire Retardants

et al. 2021

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“…The absorption peak of the softened treated material was significantly enhanced at 3410 cm −1 , where the absorption peak was mainly caused by O-H stretching vibration, which was mainly due to the superposition or mutual reaction between the functional groups in the softening solution and those in teakwood, promoting the bonding between teakwood cellulose molecules [24]. There are two new absorption peaks at 1598, and 1072 cm −1 , which are due to N-H bending vibration and C-N stretching vibration, respectively, which is possibly due to the grafting and cross-linking reaction between nitrogen in the softening solution and the chemical constituents in teakwood [25]. Meanwhile, the absorption peaks were also strengthened around 2921 and 1460 cm −1 ; 2921 cm −1 was caused by the C-H stretching vibration in methyl and methylene, and 1460 cm −1 was caused by the methyl C-H deformation and -CH2 deformation vibration in lignin and polyxylose Figure 6b shows the 13 C NMR spectra of teakwood before and after softening treatment.…”

Section: Mechanism Analysismentioning

confidence: 96%

Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution

Yao,

Ji,

Sun

et al. 2023

Forests

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To study the softening bending properties and mechanism of teakwood, it was extractively pretreated by using superheated steam, the triethanolamine compound was used as a softening solution, which was infiltrated into the wood by vacuum impregnation and synergistically softened through saturated steam to improve the bending properties of teakwood. Analysis by Fourier transform infrared spectroscopy (FTIR), Carbon 13 nuclear magnetic resonance (13C NMR), and X-ray photoelectron spectroscopy (XPS) showed that the synergistic softening treatment elevated the content of O and N elements in the softening solution and together with the C elements in the wood, formed C-NH2 and C-N bonds, which increased the molecular activity and improved the softening properties of teakwood. Scanning electron microscope (SEM) observations revealed that the outer conduits, cell walls, and fibrous tissue structures of the teakwood were stretched after softening and bending, and even microcracks of different degrees were formed between the cell walls. According to the load–deformation relationship of teakwood softening bending, the stress–strain relationship was theoretically derived and the bifold constitutive model of teakwood bending was constructed after fitting the constitutive relationship data, the integrated correlation coefficient R2 was 96.25%, which proved that the present model can better simulate the constitutive relationship of teakwood in bending.

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“…There is still some input into research and development. For example, the thermal modification of tropical wood species is a relatively young topic, but it is the subject of interest for many researchers: Kačíková et al [19,20] dealt with chemical changes in lignin due to thermal modification in meranti, padouk, merbau, teak, and iroko wood. Gašparík et al [21] and Gaff et al [22] evaluated the impact of thermal modification on color, mechanical, and chemical changes in teak, meranti, padouk, merbau, iroko, and mahogany wood.…”

Section: Introductionmentioning

confidence: 99%

Chromophores’ Contribution to Color Changes of Thermally Modified Tropical Wood Species

Jurczyková,

Šárovec,

Kačík

et al. 2023

Polymers

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This work examines the effect of thermal modification temperature (180, 200, and 220 °C) in comparison with reference (untreated) samples on selected optical properties of six tropical wood species—Sp. cedar (Cedrala odorata), iroko (Chlorophora excelsa), merbau (Intsia spp.), meranti (Shorea spp.), padouk (Pterocarpus soyauxii), and teak (Tectona grandis). The main goal is to expand the existing knowledge in the field of wood thermal modification by understanding the related degradation mechanisms associated with the formation of chromophoric structures and, above all, to focus on the change in the content of extractive substances. For solid wood, the CIELAB color space parameters (L*, a*, b*, and ΔE*), yellowness (Y), ISO brightness, and UV-Vis diffuse reflectance spectra were obtained. Subsequently, these wood samples were extracted into three individual solvents (acetone, ethanol, and ethanol-toluene). The yields of the extracted compounds, their absorption spectra, and again L*, a*, b*, ΔE*, and Yi parameters were determined. With increasing temperatures, the samples lose brightness and darken, while their total color difference grows (except merbau). The highest yield of extractives (mainly phenolic compounds, glycosides, and dyes) from thermally modified samples was usually obtained using ethanol. New types of extractives (e.g., 2-furaldehyde, lactones, formic acid, some monomer derivatives of phenols, etc.) are already created around a temperature of 180 °C and may undergo condensation reactions at higher temperatures. For padouk, merbau, teak, and partially iroko modified at temperatures of 200 and 220 °C, there was a detected similarity in the intensities of their UV-Vis DR spectra at the wavelength regions corresponding to phenolic aldehydes, unsaturated ketones, quinones, stilbenes, and other conjugated carbonyl structures. Overall, a statistical assessment using PCA sorted the samples into five clusters. Cluster 3 consists of almost all samples modified at 200 and 220 °C, and in the other four, the reference and thermally modified samples at 180 °C were distributed. The yellowness of wood (Y) has a very high dependence (r = 0.972) on its brightness (L*) and the yellowness index of the extractives in acetone Yi(Ac), whose relationship was described by the equation Y = −0.0951 × Y(Ac) + 23.3485.

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Changes of Meranti, Padauk, and Merbau Wood Lignin during the ThermoWood Process

Cited by 6 publications

References 65 publications

Flammability Characteristics of Thermally Modified Meranti Wood Treated with Natural and Synthetic Fire Retardants

Flammability Characteristics of Thermally Modified Meranti Wood Treated with Natural and Synthetic Fire Retardants

Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution

Chromophores’ Contribution to Color Changes of Thermally Modified Tropical Wood Species

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