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Today, glued timber products occupy a significant place in the volume of finished products of modern construction and woodworking enterprises. Plywood is one such product. The durability and structural characteristics of plywood depend on the quality of binder, the type of wood and the quality of veneer. The paper explores the technology of ultraviolet treatment of thermally modified birch veneer with subsequent production of waterproof plywood. The results of a study on the influence of the operating parameters of veneer modification on the complex of sorption and strength characteristics of plywood materials are presented. It is established that the combination of thermal modification of wood throughout the entire volume with surface treatment with ultraviolet radiation allows creating glued wood material with increased water resistance and high-quality adhesive interaction.

To enhance the quality of wood and extend its industrial applications, various methods of wood modification are being developed. It is well known that the thermal treatment of wood may considerably enhance its moisture resistance, reduce its hygroscopicity, and increase its rot proofing. However, reducing the absorptive capacity of wood adversely affects the process of obtaining wood-based composites. Pressure and pressing time increase, which finally increases the cost of the end product. Thus, this study represents the research in how ultraviolet exposure affects the physical properties of wood that has been pre-treated thermally, followed by obtaining a composite. An experimental wood-modifying facility has been developed. We have considered the process of the moisture absorption of the material that has been exposed to thermal modification and UV-radiation. From the experiments conducted, we have found that the UV exposure of wood samples causes an increase in the surface wettability of the thermally modified material. It is found that the most active process of surficial inactivation runs within 60-90 minutes of the UV-exposure of wood. Post-treatment does not result in any considerable changes in the surface wettability. This treatment promotes the increasing adhesion of water-borne binders to the material surface in developing high-strength composites based on modified wood.

Wood is a vital and widespread natural material [...]

Every year a huge amount of plant refuse from production of grain, oil-bearing and other crops-remains, the bulk of which has a negative impact on land and water resources. Research in the field of rational use of plant refuse showed that one of the most promising areas of use of plant refuse is obtaining organic fertilizers. At the same time, advanced research in this area concerns the production of bio-char, used as soil modifiers. In this case, the most important characteristics of the product are porosity, surface area and pH, which can be set by adjusting operating parameters of the pyrolysis process. The purpose of the research is to study the effect of pressure on the process of pyrolysis of pellets, made from the husks of sunflower, and the analysis of the main properties of the coal produced. It is established that a decrease in the pressure of the medium, leading to the forced removal of volatile substances, causes a decrease in temperature in the reaction zone, thereby increasing the duration of the pyrolysis process. However, at the same time, an increase in porosity and surface area of the obtained bio-char is observed. Thus, the feasibility of further research in this area, in order to obtain optimal temperature and pressure parameters in the process of pyrolysis of sunflower husk, was determined.

This paper considers the effect of RF plasma on wood in improving the adhesion of binders to wood by increasing its surface wettability. Our study reveals that radiofrequency (RF) plasma treatment causes a greater than threefold decrease in the marginal wetting angle of wood. The greatest effect is achieved in RF plasma treatment in argon, which is on average 5% greater than that of RF plasma treatment in air or in propane/nitrogen mixture. In addition, the power of the RF plasma torch has the greatest influence, and the main influence comes from the voltage applied to the RF plasma torch, current does not have such a significant effect. To achieve a significant effect, the duration of exposure should be at least 5 min, with a total power of 4.05 kW.Studies have been conducted to determine the adhesive strength of wood. An increase in the strength of laminated beams made from RF-treated bars in relation to control samples was found. The greatest impact on the adhesion strength was revealed when using PVA-based glue, compared with the use of polyurethane-based adhesives and urea-formaldehyde resin.

This work is devoted to the study of the effect of ultraviolet rays for the surface activation of pine wood thermally modified at temperatures of 180−240 °C in order to increase the surface roughness, enhance the wettability of thermal wood and the adhesive strength of the glue in the production of wood block furniture panels. Studies were carried out to measure the contact angle of wettability of thermally modified wood samples of pine, as a result of which it was determined that the ultraviolet treatment process contributes to an increase in the adhesion properties of the surface layer of thermally modified wood by more than 13% due to the reactivity of ultraviolet rays to oxidize and degrade ligno-containing wood products. At the same time, the most active process of surface activation takes place during 60 min of ultraviolet irradiation of wood with a total irradiation of at least 125 W/cm2. It was revealed that the combined effect of two-stage wood processing, including preliminary volumetric thermal modification followed by surface ultraviolet treatment, causes an increase in the moisture resistance of glued wood products by 24%. So, if the strength of the glue seam when gluing natural wood samples after boiling decreased by 46%, then the samples that underwent two-stage processing showed a decrease only by 22%. In connection with the results obtained, an improved technology for the production of furniture boards for the manufacture of moisture-resistant wood products is proposed.

The developed mathematical description of heat treatment of the crushed wood in rotary drum dryers, and also the results of the mathematical description of the studied process is presented in the article. The results of mathematical modeling have shown that with increase in the diameter of a drum by 3 times its length can be reduced almost by 7 times due to the increase in the relative stay time of particles in flight. It provides the best interaction of particles with the heat carrier. Increase in speed of rotation of the drum twice also allows reducing its length almost by 3 times, but at the same time energy consumption increases and crushing of raw wood materials is observed. It was established that the practical speed of the heat carrier is 0.75-2.6 m/s, which limits the drum length to no more than 8-10 meters.

The greatest interest of researchers is focused on the processes of heat treatment of wood, taking place in an airless environment at temperatures of 180-250 °C, since heat treatment of wood allows increasing its moisture resistance, reduce hygroscopicity, and increase resistance to decay. However, a decrease in the hygroscopicity of wood adversely affects the process of obtaining glued materials due to a decrease in the wettability of thermowood surface and, as a consequence, a decrease in adhesion characteristics. This work is devoted to the study of the effect of ozone on the surface of thermally modified wood to increase the adhesive properties during gluing. It has been determined that the ozonation contributes to an increase in the wettability of the surface layer of thermal wood by more than 15% due to the reactivity of ozone to oxidize and degrade ligno-containing products of wood. It was revealed that the modification of wood, including preliminary volumetric heat treatment followed by surface treatment with ozone, causes an increase in the strength of the glue line when operated in high humidity conditions. In connection with the results obtained, an improved technology for the production of glued load-bearing structures for wooden housing construction is proposed.