Establishing regularities in the propagation of phase transformation front during timber thermal modification

Abstract

The creation of environmentally friendly protective materials for building structures made of wood could make it possible to influence the processes of stability and the physical-chemical properties at the thermal modification of hornbeam wood over a certain time. That necessitates studying the conditions for investigating phase transformations when the timber is exposed to high temperature, as well as establishing the mechanism of hornbeam wood thermal modification. Given this, a mathematical model of the phase transformation process during the transfer of heat flux to a sample was built. Based on the derived dependences, it was established that when hornbeam wood is exposed to temperature treatment, it undergoes endothermic phase transformations characterized by the heat absorption and change in the color of hornbeam wood. In particular, at a temperature of 200 °C, the temperature in the wood decreases by 5 % due to the chemical changes in the structure of cell wall components (lignin, cellulose, and hemicellulose). It was found that the process of thermal modification is accompanied by the decomposition of hemicellulose and the amorphous part of cellulose, a decrease in moisture absorption, as well as a decrease in the volume of substances that are a medium for the development of fungi. In addition, lignin and the resulting pseudo lignin undergo a process of polymerization and redistribution throughout the cell volume. At the same time, they give the cell walls higher density, hardness, increase hydrophobicity (water repellency), thereby reducing the ability to absorb moisture and swell. It was established that the most effective parameter of phase transformations is the temperature and aging duration. The results of moisture absorption have been given; it has been found that over 6 hours of modified timber exposure, its moisture absorption decreases by more than 10 times, which allows its application at facilities with high humidity

Establishing regularities in the application of dry pine wood

“…Consequently, the formation of bacteria in the structure of wood is closely related to a decrease in its density, which is confirmed in [16]. At the same time, it is possible to carry out thermal modification of such wood in order to stop the development of a fungus of the Ceratostomaceae family or the use of antiseptics [17,18]. Such conclusions can be considered appropriate from a practical point of view because they allow a reasonable approach to determining the heat of combustion of dry wood.…”

Automated Microclimate Regulation in Agricultural Facilities Using the Air Curtain System

“…An important component for ensuring the temperature regime in agricultural buildings, including livestock buildings, is the building material. To prevent moisture permeability of the wooden elements of the room, they are subject to thermal renovation, as investigated in a number of publications by Mazurchuk, S., Marchenko, N., Tsapko, Y. et al [28][29][30], researchers from Ukraine and Slovenia. On the other hand, the research on the thermodynamic properties of a room and the construction of thermodynamic models was carried out by researchers from Ukraine and Slovakia, Pinchevska, O., Spirochkin, A. et al [31][32][33][34][35].…”

Determining patterns in reducing the level of bio-destruction of thermally modified timber after applying protective coatings

“…The thermal timber modification was performed at temperatures of 190 °C and 220 °C for 10 hours. Both the activation energy [13] and the end of phase transitions were taken into consider-ation [14]. The samples were then treated with oil-wax and azure by immersion method with re-treatment after drying of the first layer in 24 hours [15].…”

“…It is also necessary to consider that when thermally-treated timber is applied, its destruction under the effect of bacteria is possible. Taking into consideration the research reported in [13], it is proposed to use oil-wax and azure to protect materials against biological destruction.…”