Color Change of Birch Wood During Thermal Exposure

Heat treatment is widely used to improve the properties of wood. Such processes include drying and thermal modification. Thermal modification is heating wood without oxygen, accompanied by heat destruction. Thermally modified wood can be used as structural and finishing materials. This puts the task of determining its thermal and physical, physical and chemical, biological, and ornamental properties and their change during heat treatment. The article presents the results of experimental and computational studies of color characteristics of the wood of birch, their change in the process of thermal modification. Thermal decomposition is a complicated multi-stage physical and chemical process. Thermal decomposition of material causes changes in its composition, structure, accompanied by alterations of its properties. Wood can be considered as a multicomponent composite material, consisting of hemicellulose, cellulose, lignin and other components. Each component decomposes in the temperature range that causes the multistage process of thermal degradation. The degree of thermal degradation of the material is determined by the kinetics of occurrence of each stage and the degree of its perfection. Thermal decomposition kinetics of wood can be determined by the results of thermal and gravimetric experiments. In the article the model of determining the color characteristics of wood as a function of the degree of completion of individual stages of thermal degradation is suggested. Model of decomposition of color for RGB components is used for identifying. Color identification of the samples of original birch wood in RGB coordinates was performed. The parameters of thermal effects, allowing to obtain wood with given degree of thermal decomposition are defined. Heat treatment of samples and identification of their color is made. The dependence of RGB parameters from time and intensity of heat treatment is studied. Empirical relations to determine the identifying characteristics of color, as a function of the degree of completion of stages of thermal destruction, in RGB and LAB systems are obtained in explicit form.