Improving Performance of Thermal Modified Wood against Termites with Bicine and Tricine

The desire to incorporate wood in modern construction has led to a considerable increase in the use of wood modification techniques, and especially thermal modification. However, thermally modified wood has poor performance against termites. The concept of using a combined chemical and thermal modification has been undertaken through the impregnation with either bicine or tricine prior to modification. This paper considers the effects of these chemicals on the activity of termites and considers their mode of action in terms of termite survival and on their effects on the symbiotic protists present within the termite gut.

Establishment of the regularities of the polymer cover influence on the wood bio destruction

The process of wood biological destruction is analyzed. It was found that the neglect of environmentally friendly means of bioprotection, leads to the destruction of wooden structures under the action of microorganisms. It is established that the study of wood protection conditions leads to the creation of new types of protective materials that reduce water absorption, as well as reduce the amount of substances that are the environment for the development of wood-destroying fungi. In this regard, a computational and experimental method for determining the proportion of destroyed material under the action of microorganisms using an antiseptic has been developed. The analysis of the results shows that the maximum weight loss in the case of biodegradation of untreated wood samples ranged from 7,6 to 16 %, and the weight loss of thermally modified wood samples did not exceed 3 %, antiseptic-hydrophobicizer – was less than 2 %. It was found that the protection when treated with thermally modified wood with oil-wax and azure exceeds (compared to untreated) more than 4 times in terms of biodegradation, and treatment with antiseptic-water repellent for untreated oil-wax and azure – more than 8 times. It should be noted that the presence of oil-wax and azure leads to blockage of the wood surface from the penetration of moisture or microorganisms. Therefore, the intensity of wood-destroying fungus development on the surface of various samples are differed. Obviously, such a mechanism of the protective coating influence is the factor regulating the process, which preserves the integrity of the object. On the experimental data basis and by modeling the equations, the microorganisms population dynamics in the volume of material and the function of increasing the number of dead organisms are derived. Thus, a polymer shell was created on the surface of the sample, which significantly reduced the penetration of microorganisms into the wood, and the weight loss of wood during biodegradation did not exceed 2,5 %. Additional application of protective substances on the surface increases the protection level of untreated pine wood by 72 %, thermomodified at 190 °C – 25 %, at 220 °C – by 37 %. Similar results for hornbeam wood – 60; 37 and 28 %, for oak – 50; 37 and 37 % respectively.

Life Cycle Assessment of Coated and Thermally Modified Wood Façades

Façades—their design, aesthetics, performance, type of cladding material, and understructure—determine architectural expression and form unique appearances of individual buildings. In connection to the sustainable development idea, wood façades provide one of the alternatives of a contemporary building exterior look. Façade cladding made of coated and thermally modified wood can be successfully used for these buildings. In addition, thermally modified wood allows the use of local European wood species, while keeping cladding elements relatively thin. On the other hand, wood has certain structural limitations and disadvantages due to the properties of wood. The main weakness is caused by the surface durability of wood and its related need for maintenance over time. The scope of the study was a comprehensive assessment of coated non-heat-treated and thermally modified wood façades, performed in terms of life cycle assessment. The aim was to identify which type of wooden façade had the lowest environmental impact. According to the EN 15804 + A2 standard, the principle of evaluation of environmental parameters “cradle-to-gate-with options” was used to evaluate wooden façades and coatings and surface preservation methods. Simulations with the SimaPro program showed that the thermal modification of wood has a significant impact on the environment at the product stage. Nonetheless the thermally modified façade without any surface coating showed the lowest environmental impact in a 30 year time-horizon of the “use stage”. It was showed that surface maintenance methods applied, the coatings used, and the frequency of their application play an important role in the environmental impact of the investigated wooden façades.

Chemical Characterization of Waterlogged Charred Wood: The Case of a Medieval Shipwreck

In 2008, a medieval wooden shipwreck was discovered at the port of Rhodes, Greece. The shipwreck was party burned, presenting a challenge for conservators, as uncharred, semi-charred and charred waterlogged wood were often encountered on the same piece of timber. In seeking the most appropriate conservation method for this unusual material, its chemical characterization was considered necessary. This study examined the chemistry of the three dominant wood conditions found in the wreck. Fourier transform infrared spectroscopy and X-ray diffraction analysis were implemented in comparison to reference samples. Energy dispersive analysis was also used for assessing the inorganic composition of each condition. Moreover, for charred and semi-charred wood, proximate analysis was undertaken. Results obtained regarding the organic moieties of the waterlogged archaeological material, demonstrated that charred samples were chemically comparable to charcoals, semi-charred material showed similarity to thermally modified wood, whereas uncharred waterlogged wood was proven to have an analogous chemistry to biodeteriorated wood. Elemental analysis results also diversified among the three shipwreck’s conditions. Sulfur, iron, and oxygen decreased in charred areas, whereas carbon increased. Proximate analysis showed that ash and fixed carbon content increased with charring, whereas volatile mater decreased. This work proved major chemical differences among shipwreck timbers’ conditions owing to different degree of charring. These are anticipated to influence not only conservation methods’ efficacy, but also the post-treatment behavior of the material. Further investigation is needed for correlating the chemistry of the archaeological material to its physical properties in order to contribute to practical aspects of conservation.

Sorption and diffusion properties of untreated and thermally modified beech wood dust

Dynamic water vapor sorption experiments were carried out using beech wood dust (from untreated and thermally modified wood) of two-particle sizes, (< 25 and 80–250 µm), obtained from abrasive sanding. Sorption isotherms were parameterized with the GAB and GDW models. Dust from thermally modified wood had significantly lower equilibrium moisture content compared to dust from untreated material, due to the reduction in primary sorption sites in treated material. The observed changes were quantified by the coefficients of the GAB and GDW models. Thermal modification and size of wood dust particles had no influence on binding energy of water molecules being linked to the secondary sorption sites. Water diffusivity decreased significantly with increasing moisture content, but only for monolayer sorption. For higher moisture content values, water diffusivity was practically independent of moisture content. These results were found for untreated and thermally modified material as well as for both dust size fractions. The influence of thermal modification on water diffusivity was unclear, which is attributed to the diffusion model, which represents dust particles as spheres and assumes instant hygroscopic equilibrium. Overall, this study indicates that the effectiveness of filtration processes likely depends strongly on sorption and diffusion properties of wood dust only at low moisture contents within the hygroscopic range.

Particleboards from Recycled Thermally Modified Wood

In recent years, the production and consumption of thermally modified wood (TMW) has been increasing. Offcuts and other waste generated during TMWs processing into products, as well as already disposed products based on TMWs can be an input recycled raw material for production of particleboards (PBs). In a laboratory, 16 mm thick 3-layer PBs bonded with urea-formaldehyde (UF) resin were produced at 5.8 MPa, 240 °C and 8 s pressing factor. In PBs, the particles from fresh spruce wood and mixed particles from offcuts of pine, beech, and ash TMWs were combined in weight ratios of 100:0, 80:20, 50:50 and 0:100. Thickness swelling (TS) and water absorption (WA) of PBs decreased with increased portion of TMW particles, i.e., TS after 24 h maximally about 72.3% and WA after 24 h maximally about 64%. However, mechanical properties of PBs worsened proportionally with a higher content of recycled TMW—apparently, the modulus of rupture (MOR) up to 55.5% and internal bond (IB) up to 46.2%, while negative effect of TMW particles on the modulus of elasticity (MOE) was milder. Decay resistance of PBs to the brown-rot fungus Serpula lacrymans (Schumacher ex Fries) S.F.Gray increased if they contained TMW particles, maximally about 45%, while the mould resistance of PBs containing TMW particles improved only in the first days of test. In summary, the recycled TMW particles can improve the decay and water resistance of PBs exposed to higher humidity environment. However, worsening of their mechanical properties could appear, as well.

Interaction between Thermal Modification Temperature of Spruce Wood and the Cutting and Fracture Parameters

This work examines the effect of thermal modification temperatures in the production of thermally modified wood on the cutting and fracture parameters when cutting heat-treated spruce wood by a circular sawblade machine. The samples were thermally modified at 160, 180, 200, and 220 °C. One sample was unmodified and was used as a reference sample. On the basis of the performed experiments, the fracture parameters (fracture toughness and shear yield strength) were calculated for the axial–perpendicular direction of cutting. In comparison with the theoretical assumptions, the influence of temperature on the cutting and fracture parameters was confirmed. Thermally treated wood is characterized by increased fragility and susceptibility to crack formation, as well as reduced density, bending strength, and shear strength. These properties significantly affect the size of the cutting force and feed force, as well as the fracture parameters. As the temperature increases, the values of these parameters decrease. The mentioned material characteristics could be useful for the optimization of the cutting process, as well as for the issue of energy consumption during the machining of heat-treated wood.

Thermally Modified Wood Exposed to Different Weathering Conditions: A Review

Outdoor wood applications are exposed to several different biotic and abiotic factors, and for that reason, they require protection to increase their service life. Several technologies of wood protection are already commercialized. One of these technologies is thermal modification, which refers to the structural, mechanical, and chemical transformations occurring in the lignocellulosic material when gradually heated up to specific temperature ranges. In the past few years, several researchers have undertaken weathering resistance evaluations on different wood species. Some cases have considered natural exposure in different countries with different climatic conditions, while others focused on artificial exposure under UV and xenon radiation tests. Most works evaluated the weathering effects on the chemical, mechanical and physical, and anatomical shifts compared to the original characteristics of the material. This review has established a considerable lack of studies in the bibliography focusing on abiotic factors, such as the industrial and maritime environment, or even isolated climatic factors such as salt spray (simulating maritime environments) or pollutant gases (simulating industrial environments). This lack of information can be an opportunity for future work. It could help to understand if thermally modified wood is or is not sensitive to pollutant gases or salinity, or to a combination of both. By knowing the degradation mechanisms caused by these factors, it will be possible to study other forms of protection.

OPTIMIZATION OF PROTECTIVE COATING COMPONENTS OF THERMOMODIFIED WOOD TO THE EXPOSURE OF WATER

Paints and varnishes are used to a large extent to protect wood surfaces in outdoor conditions, as they are easy to maintain and reapply. Also, when developing a coating, manufacturers are guided by the need to obtain a number of properties that generally determine its ability to protect against moisture. To obtain a protective coating that meets the specified requirements, it is necessary that the components that make up the coating belong directly to the group of protective materials or form such compounds under operating conditions, be able to adhere to the surface of the product. It was found that thermal modification provides a decrease in water absorption of wood. Additional processing of the wood surface helps to reduce moisture absorption by 2 times, and for samples modified at a temperature of 220 °C – 3 times. Geometric dimensional stability is also improved by a factor of 2. The effect of heat treatment on the water absorption of wood is somewhat less – for samples modified at 190 and 220 °C for more than 10 hours. Protective substances for thermally modified wood provided similar protection of open thermally modified surfaces of wood from the effects of water. The positive effect of thermal modification on a decrease in the level of water absorption has been established. It has been proven that it is temperature that has a significant effect on such changes. Since the protective coating is also susceptible to photochemical degradation, it is very important to renew it in a timely manner in accordance with the manufacturer's instructions for the pleasant appearance of wood surfaces during external use. The optimal ratio of components in the surface layer of thermally modified wood has been determined, which ensures the fulfillment of the task, namely for a mixture of oil and wax: the density of a wood – 724 kg/m3; oils – 70.0%; wax – 17.5%. Therefore, such treatment is beneficial for the protection and aesthetic appeal of wood products.