With increasing competition for wood resources, the importance of using small-diameter timber, which consists predominantly of juvenile wood (JW), is growing. The manufacturing of glued products is one way to make rational use of small-diameter wood assortments. However, the properties of JW differ considerably from those of mature wood (MW) and can affect product performance. Radial profile analyses of anatomical structural elements were performed, and based on the fibre length results, the cambial ages of 17 years for silver birch (B. pendula Roth.) and 23 years for Scots pine (P. sylvestris L.) were determined to distinguish between JW and MW. The results showed that the JW of both species had a lower density and higher transverse swelling anisotropy. Lamellae of JW and MW were glued into beams using two one-component polyurethane adhesives and different assembly regimes. The glued beams were then used to prepare samples for delamination tests, performed according to the EN 302-2 standard method for Type I adhesive. Higher resistance to delamination was observed for the JW of both wood species, implying an advantage of laminated products from JW regarding bond-line stability under varying moisture conditions. For pine JW, shorter open assembly times resulted in significantly less delamination.

Most microplastics (MPs) are generated as a result of photodegradation during the life of plastic products and after the end-of-life as mismanaged waste. At present, it is impossible to avoid plastic-based materials altogether because of their unique properties, versatility, and price. An option is to set limits on how much MPs these materials can release over their lifetime, which would not only reduce MPs pollution, but also improve product quality. However, there is a lack of reliable methodologies for assessing the generation of MPs from these products during use or when they are left as unmanaged waste. The objective of this study was to develop a novel method to assess (collect and quantify) MPs formation from plastic-based materials during weathering. The developed process design is based on a well-established accelerated weathering tester that has been modified by incorporation of a sieve system and water recirculation. The case study is carried out on a recycled polypropylene (rPP) and wood plastic composite (WPC) made from wood particles and the same rPP. Despite the lower plastic content, WPC released significantly more MPs (up to 9.4 g/m2) than the rPP (up to 0.3 g/m2) in the same weathering conditions and duration. Examination of the degraded surfaces revealed that the wood particles facilitated the release of MPs most likely due to moisture fluctuations causing wood swelling induced internal stresses. The collected MPs were mainly below 500 μm and their properties were different comparing to MPs made by cryogenic milling. PY-GC-MS did not detect MPs smaller than 20 μm that could pass through the smallest sieve and end up in the effluent. The reproducibility of the measured MPs release using the process design was very good during the tested weathering period, with variations of less than 7

Accumulation of microplastics (MPs) and the potential risks that they bring causes justified concerns. Plastic-based materials are widely used in various applications. The materials are presumed to be inert and safe. However, the formation of potential MPs has introduced some doubts. Wood-plastic composites (WPCs) are among the materials suggested to be environmentally friendly. However, they may release MPs due to weathering as WPCs are widely used in outdoor applications. The objective of the study was to collect, quantify, and compare MPs' release during artificial weathering from WPCs and evaluate the effect of composition. In the study, four experimental and four commercial WPCs were analysed. Recycled polypropylene (rPP) was used as a reference. The results showed that WPCs can be a source of MPs, and that their composition significantly affects their formation. Wood particles in WPCs facilitate erosion, causing MPs to be released at a rate of 5.6 g/m2, whereas the release from rPP was 0.1 g/m2 after one month of accelerated weathering. For commercial products, MPs formation depends on the product type, with no MPs released for WPC decking but a significant release of up to 58.9 g/m2 for the flowerpot after 2 months of accelerated weathering.

Microwave technology finds application in wood processing, particularly for improving drying and impregnation. A less explored application is the treatment of wood to reduce resin exudation. The aim of this research is to examine how microwave treatment of spruce wood specimens can change the physico-chemical properties of resin to retain it in the wood. The results demonstrated that microwave treatment can increase the glass transition temperature more rapidly than conventional heat treatment. Both the amount of volatile content and chemical composition of resin are affected. Further optimization of treatment parameters, such as duration and power density, could enhance the efficiency of this method.

Wood plastic composites (WPCs) have recently gained attention as alternatives to traditional wood materials for outdoor use, thanks to their enhanced moisture resistance and durability, which extends their service life. Discolouration as well as surface erosion has been observed during weathering for both WPCs with untreated and heat-treated wood. However, aspects such as changes in surface hydrophobicity, chemistry, and erosion in terms of microplastic formation have received less attention; this research aimed to evaluate these factors during natural weathering. Four types of WPC samples, consisting of 50% wood particles (untreated and heat-treated) and 50% polypropylene, were naturally weathered in Latvia for two years. The samples measured 240 mm × 240 mm × 5 mm. Results showed rapid colour changes, microcracks, and exposed wood particles, suggesting microplastic formation. ATR-FTIR analysis showed increased absorption at 1715 cm⁻¹ (carbonyl groups) and at 3410 cm−1 and 3460 cm−1, typical of wood, indicating chemical changes on the surface. These changes influenced surface hydrophobicity, roughness, and water penetration. In a relatively short exposure time, WPCs without proper additives undergo significant changes in their aesthetic and physical properties, leading to surface erosion and potential microplastic formation. This could challenge the perception of WPCs as environmentally friendly materials.

In order to explore the possibilities of increasing the hydrophilicity of carbon-based adsorbents, catalysts, or electrode materials in aqueous solutions, the oxidation of wood-based activated biochar using H2O2 was investigated. The properties of oxidized activated biochar obtained at different activation temperatures (600, 700, and 800 °C) and H2O2 oxidized for 15–180 min were investigated using the characteristics of surface functionality, elemental composition, porous structure, contact angle measurements, FTIR spectroscopy, and immersion calorimetry. It was observed that the optimal oxidation time was different for each sample depending on activation temperature, and the degree of oxidation can be tailored by changing the oxidation time. The course of oxidation depends on the degree of graphitization and functionalization, determined by the activation temperature. It was established that the highest degree of oxidation and increase in wettability is observed for samples with the lowest degree of activation obtained at a temperature of 600 °C.

A major function of resin in trees is to provide defense against external attacks by releasing the resin flow in the attacked or damaged area. Nonetheless, leakage of resin on the surface can have negative aesthetic and economic impacts on wood materials. The aim of this study was to investigate how heat treatment affects the physico-chemical properties of the resin of Pinus sylvestris L. to hinder exudation on wood surfaces during service. To reduce the fluidity of the resin, it is necessary to remove the volatile fraction of resin, and several studies have been carried out in this direction, providing useful information about this process. The results from thermal analyses (DSC, TGA) confirmed that heat treatment at mild temperatures, 80 °C, 90 °C and 100 °C had a positive effect on increasing the glass transition temperature Tg and that the Tg and the residual volatile content were strongly correlated. FTIR spectroscopy, before and after heat treatment, did not reveal major changes in chemical structure, while UHPLC-DAD-MS analysis revealed significant differences in the ratios of compounds, which are the result of possible chemical reactions, such as dehydrogenation, oxidation and isomerization.

Plastics when exposed to UV radiation start to degrade via photooxidative aging including free radical formation, oxidation, chain scission and/or crosslinking reactions. These chemical changes can cause loss in mechanical strength, surface embrittlement, and eventually surface erosion. The eroded particles are microplastics (MPs), which have been identified as a potentially serious threat to the environment and its inhabitants. In general, photodegradation of virgin plastics has been studied extensively, but there is not much literature on the degradation of recycled plastics. The goal of the study was to investigate the changes caused by photodegradation in recycled plastics and assess the potential risks of MPs formation. And eventually, knowing the chemical and physical transformations occurring on the surface understand the mechanism behind surface microcracking, which is the first step of MPs formation. Pellets of five industrially recycled plastics (low-density polyethylene (rLDPE), linear low-density polyethylene (rLLDPE), high-density polyethylene (rHDPE), and two polypropylenes (rPP)) from different waste sources were analysed. UV irradiation was performed in an accelerated weathering chamber for milled (< 400 m) plastic powder to ensure homogeneous changes throughout the sample. The properties were investigated by ATR-FTIR, HT-SEC, XPS and DSC. Formation of microcracks was studied on plastic pellets by SEM. The results showed that the degradation significantly differed between the recycled plastics, and the waste source was more important than the plastic type. rLDPE and one of the rPP samples showed a significant increase in carbonyl index as well as decrease in molar mass during the first 500 h of UV exposure. The other rPP and rHDPE samples showed first considerable signs of degradation only after 1000 h of UV exposure. Minor changes were observed for the rLLDPE sample during the whole test. The SEM revealed microcracking on the surface of all samples, which also had noticeable degradation identified by other methods. These recycled plastics can be considered the ones with the highest potential of MPs formation. From the chemical and physical transformations identified on the surface, the mechanism leading to microcracking, which is the first step in the formation of MPs, is proposed.

A major function of resin is to provide defense against external attacks by releasing the resin flow on the attacked or damaged area. Nonetheless, the leakage of the resin on the surface can have a negative aesthetic and economic impact on wood material. The aim of this study is to investigate which treatments affect the chemo-physical properties of the resin in order to hinder the exudation on wood surface during service. To achieve a thickening of the resin, it is necessary to remove the volatile turpentine, and several studies have been carried out in this direction, providing useful information about this process. The heat treatment at different temperatures, 60°C, 100°C and 150°C, respectively, gives different mass losses, thus confirming that the turpentine can remain for long time in the resin, and the changes in structural, morphological, and chemical properties are affected by the temperature. FTIR spectroscopy, before and after thermal treatment, does not show major changes in chemical structures. However, from the samples analyzed with UHPLC-DAD-MS significant differences of the ratios of 20 compounds were observed, which characterize possible chemical reactions, such as decomposition, dehydrogenation, oxidation and isomerization. After heat treatment, the glass transition temperature of resin increased. Color changes are evident: resin becomes darker with increasing the temperature of treatment, apart from the resin heated at 100°C. The chemical changes in the composition of the resin caused by heat treatment need further investigation.

The aim of this study was to characterize and evaluate the performance of two wood species, pine (Pinus sylvestris L.) and spruce (Picea abies Karst.) used for wooden furniture in outdoor coated with a water based ecological paint and subjected to artificial weathering. Another task of this research was to investigate the potential of the application of paint using dipping method in alternative to traditional brush or spraying coating application methods, since, if wood samples are grouped in stacks, the processing time can be reduced, compared to samples painted singularly. From the analysis of the dipping parameters, such as time and paint concentrations, more practical and specific knowledge was obtained regarding this painting method.From the characterization of the painted samples and from the measurements of color changes during artificial weathering it was observed that coated wood surfaces have similar optical properties also in case of different dipping times, although the type of wood could affect the performance of final product during artificial weathering test as in case of spruce wood samples, specifically those prepared with the shortest dipping time: for these samples a lower resistance to weathering and higher color changes were observed.

Mostly the effect of solar and UV radiation on wood photodegradation has been researched. This paper discusses the effect of artificial light sources, which differ in the spectral composition of the emitted light, on the photodegradation of wood. Ash, birch, aspen, pine sapwood and heartwood, and spruce wood were exposed to two LEDs of different colour temperature (3000 and 6500 K), incandescent and fluorescent lamps. Changes in colour (ΔE) and colour parameters L*, a*, b* (CIELAB colour space) as well as reflectance and FTIR spectra were analysed to evaluate the photodegradation of wood depending on the light source. According to the results of changes in the chromaticity system of woods, the tested light sources can be divided into two groups: one group with similar results includes the two tested LEDs while the other group includes incandescent and fluorescent lamps. Lower irradiation dose was needed for the LEDs to impart visually perceptible discolouration, whereas colour changes of greater magnitude were caused by the incandescent and fluorescent lamps at higher irradiation doses. It was detected that depending on the light source, there are differences in the changes in the chromophores between hardwoods and softwoods, with more total discolouration observed for softwoods. The transformations in the chemical structure, which was analysed by FTIR, considerably differed for all tested light sources with a general trend of the greatest effect of the fluorescent lamps followed by the incandescent lamps and LEDs.

When using binders in coatings, whose film formation process relays on the oxygen uptake to start the cross-linking reaction, the use of special metal salts, so called driers, can catalyze the process, accelerating the curing of the film and reducing the waiting time between the applications of the next layers of paint. In this work, three primary driers, based on cobalt, iron and manganese are compared, to determine which one is more efficient in drying of alkyd and boiled linseed oil based coating. The study has been done using FTIR spectroscopy to investigate the rate of drying for each drier. The obtained results confirm that using the cobalt drier, the film formation is faster than with the other two alternative driers.

Thermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood was assessed and, based on these results, the possibility to delay discoloration due to weathering by non-film forming coating containing transparent iron oxides in the formulation was studied. The effect of including organic light stabilizers (UVA and HALS) in coatings as well as pretreatment with lignin stabilizer (HALS) was evaluated. Artificial and outdoor weathering was used for testing the efficiency of different coating formulations on TM wood discoloration. For color measurements and discoloration assessment, the CIELAB color model was used. Significant differences between the spectral sensitivity of unmodified and TM wood was observed by implying that different strategies could be effective for their photostabilization. From the studied concepts, the inclusion of the transparent red iron oxide into the base formulation of the non-film forming coating was found to be the most effective approach for enhancing TM wood photostability against discoloration due to weathering.

In this research, three ecological paints, based on linseed oil as the main component, are characterized and investigated to optimize their properties and utilization in protection of wood surfaces. The aim is to find the suitable parameters for the application and drying of the paints, which can guarantee a better protection of wood surfaces during outdoor utilization. Initially the three paints were characterized determining some of their chemophysical parameters, such as density, viscosity, dry content and glass transition temperature. Afterwards panels of pine wood (Pinus sylvestris L.) were coated and exposed to outdoor weathering (OW). During OW color changes and hydrophobicity are repeatedly measured and monitored to evaluate the efficiency of the paints. To minimize the discoloration of wood substrate, paint formulations include also different type of pigments in their composition.

Plywood is a well-known material with versatile usage due to its strength to weight ratio. One of the drawbacks of this material is its susceptibility to wood colouring and degradation by the influence of fungi. Fungal growth is directly related to the wood service conditions, among which moisture is the most important. One of the ways of reducing the wood moisture content by the increase of the hydrophobicity of the material is a thermal modification (TM). Thermowood (R) is the most popular among many thermal treatment technologies. In this paper two less common TM methodologies - WTT and TERMOVUOTO (R) were used. The WTT technology is a closed process, where the thermal modification is conducted in water vapour environment with elevated pressure of about 7 bar, whereas the TERMOVUOTO (R) process is an open process with reduced pressure 0.25 bar. Three low-density wood species veneers were investigated - aspen (Populustremula L.), poplar (Populus x canadensisMoench) and birch (Betulapendula Roth). Aspen and birch veneers were treated according to WTT technology under previously determined optimal regime 160 degrees C/50 min and it was used as a reference. Poplar and birch veneers were treated according to the TERMOVUOTO (R) technology with four experimental regimes 204 degrees C/2 h, 214 degrees C/2 h, 217 degrees C/3 h, 218 degrees C/30 min The comparison of the contact angle values of un-treated, thermo-vacuum treated and hydro-thermal treated birch and poplar wood veneer surface was used to evaluate the thermal treatment method effect. The treatment process smoothed the hydrophobic properties of the treated veneer surfaces regardless of the process severity and hardwood species peculiarities. The obtained results make it easier to deal with the gluing process of thermally modified veneers, allowing not to consider the impact of the treatment regime.

The aim of this research is to investigate and to evaluate the changes that occur on the surface of wood specimens, coated with three different coatings and exposed to artificial weathering. The three used coatings contain linseed oil and different types of pigments. Specimens of pine wood (Pinussylvestris L.) were painted with one or two layers of coatings to evaluate the discoloration and changes in lightness. For all the tested coatings, discoloration and loss of lightness were observed for all specimens regardless of the applied coatings. Different rates of color changes were observed for the tested coatings. The presence of pigments in the coatings formulation delays the discoloration of wood; as also the composition of pigments plays a significant role in the process.

We evaluated the performance of covered and impregnated birch plywood (BP) in the outdoor environment. Fungal growth, crack formation, and surface hydrophobicity were regularly assessed over 36 months. After 2 months, uncovered BP was severely colonised by disfiguring fungi. During the test period, the surface of plywood with better coatings (solvent- or water-based) was not overgrown or was overgrown slightly with fungi, no cracks were formed, and the surface hydrophobicity was stable. Similar results were observed for laminates with phenol and melamine film. Plywood impregnated with copper and organic biocides, with retention conforming to Use Class 3 (EN 335:2013), did not protect the plywood from crack formation within several months and the severe growth of disfiguring fungi within a year. The blue stain fungus Aureobasidium pullulans was identified for all overgrown test variants. No rot fungi were detected after a 36-month exposure.

Biomaterials used in bone repair must satisfy certain criteria in order to perform without undesirable immunological response. They must be biocompatible and should inhibit bacteria adhesion on the surface, that could led to strong inflammatory process and implant failure. Our study reveals a synergistic effect on bioactivity and bacteriostasis effect of the TiO2 ceramics with different surface properties and provides insight into the design of better biomedical implant surfaces. The results show that UV light irradiation has great impact on hidrophilicity of TiO2 ceramics, but little effect on the sample bacteriostatic effect and bioactivity. TiO2 ceramic samples showed no or very low bacterial adhesion. Nevertheless, in vitro bioactivity showed TiO2 ceramic that was thermally treated at lower temperature. Thus for bone repair it’s suggested to use TiO2 ceramic sintered at lower temperature in order to provide bioactivity with bacterostatic effect and use UV-light irradiation to improve hidrophilicity.

The effect of thermo-hydro treatment (THT) on the properties of birch (Betula spp.) wood veneers has been studied. THT was carried out in a multi-functional pilot scale wood modification device of wood treatment technology (WTT, Latvia) under elevated water vapor pressure conditions at four combinations of temperature and treatment time (degrees C/min): 150/10; 150/50; 160/10 and 160/50. After THT, the following veneer properties were examined: mass loss (ML), chemical composition, bending strength (BS), tensile strength (TS), equilibrium moisture content (EMC), resistance to decay by mould and blue stain fungi, and surface contact angle (CA). The chemical components were changed by THT. Increased THT temperature and time resulted in hydrophobization of veneers as indicated by decreasing EMC and increasing CA data. All THT were effective against wood discoloring fungi, although insufficient decay resistance was observed. The mechanical strength properties of THT veneers were also deteriorated.

A newly developed thermo-hydro treatment (THT) for use in a one-stage heat treatment process was examined by focusing on the form stability-related properties of European aspen (Populus tremula), birch silver (Betula pendula), and gray alder (Alnus incana). In particular, wood specimens were subjected to THT in a saturated steam atmosphere in a pilot-scale autoclave heated between 140 and 180 degrees C for 1-3 h. Several parameters of untreated and treated samples after several soaking and drying cycles were compared, namely, the changes in the volumetric swelling, swelling in the radial and tangential directions, cell wall total water capacity, and anti-swelling efficiency (ASE). Due to repeated wetting in the cyclic water submersion-drying test, the original ASE of 73% decreased to 65% (180 degrees C for 1 h), and the original ASE of 33% decreased to 5% (140 degrees C for 1 h). Wood modified at 170 degrees C presented good results that were not significantly lower than wood treated at higher temperatures while consuming less energy to deliver ASE improvement and was selected as optimum. To increase the ASE by 1%, the amount of energy consumed was decreased by 41%, 39%, and 17% compared with the treatment regimes of 160 degrees C for 1 h, 160 degrees C for 3 h, and 180 degrees C for 1 h, respectively. The new THT regime led to improved long-term dimensional stability due to the cross-linking of cell wall polymers, which resulted in increased cell wall rigidity.