这项工作研究了与参考(未处理)样品相比,热改性温度(180、200和220°C)对六种热带木材物种Sp的选定光学特性的影响。雪松(雪松),iroko(Chlorophoraexcelsa),merbau(Intsiaspp.),美兰蒂(Shoreaspp。),padouk(Pterocarpussoyauxii),和柚木(Tectonagrandis)。主要目标是通过了解与发色结构的形成相关的降解机制来扩展木材热改性领域的现有知识,最重要的是,重点关注提取物质含量的变化。对于实木,CIELAB颜色空间参数(L*,a*,b*,和ΔE*),黄色(Y),ISO亮度,获得了紫外-可见漫反射光谱。随后,这些木材样品被提取到三种单独的溶剂(丙酮,乙醇,和乙醇-甲苯)。提取的化合物的产率,它们的吸收光谱,L*,a*,b*,ΔE*,和Yi参数进行了测定。随着温度的升高,样品失去亮度和变暗,而它们的总色差增加(除了Merbau)。最高收率的提取物(主要是酚类化合物,糖苷,和染料)通常使用乙醇从热改性样品中获得。新型提取物(例如,2-糠醛,内酯,甲酸,一些酚的单体衍生物,等。)已经在180°C左右的温度下产生,并且可能在更高的温度下发生缩合反应。对Padouk来说,Merbau,柚木,并在200和220°C的温度下对部分Iroko进行了改性,在与酚醛相对应的波长区域,其UV-VisDR光谱的强度存在检测到的相似性,不饱和酮,醌,二苯乙烯,和其他共轭羰基结构。总的来说,使用PCA的统计评估将样本分为五个簇。集群3由几乎所有在200和220°C下改性的样品组成,在其他四个中,在180°C下分配参考样品和热改性样品。木材(Y)的黄度对其亮度(L*)和丙酮Yi(Ac)中提取物的黄度指数有很高的依赖性(r=0.972),其关系由方程Y=-0.0951×Y(Ac)+23.3485描述。
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.