Chia-Feng Lin

High-temperature drying can considerably improve drying efficiency. However, information on its impact on the mechanical properties of silver fir during industrial high-temperature drying remains limited. Elevated drying temperatures may induce changes in wood structure that can influence mechanical performance. This study evaluated the effect of high-temperature drying schedules based on industrially applied temperature levels (120 °C and 150 °C) on selected mechanical properties of silver fir (Abies alba Mill.). Wood samples were kiln-dried at 120 °C and 150 °C, conditioned to equilibrium moisture content, and tested for impact bending strength, tensile strength perpendicular to the grain, and Janka hardness. Because the experimental material originated from a single silver fir tree, the findings should be interpreted as describing responses within the investigated material rather than as population-level effects for silver fir. The results showed that drying at 150 °C was associated with a tendency toward reduced values of selected mechanical properties; however, the effect of drying temperature was not statistically significant for impact bending strength. ANOVA showed that specimen thickness significantly affected impact bending strength and Janka hardness, whereas drying temperature had a significant effect only on tensile strength perpendicular to the grain. The lowest mean values were observed in the β-150 group, with impact bending strength of 5.4 J·cm⁻² and tensile strength perpendicular to the grain of 2.3 MPa. The mean oven-dry density was 456.9 kg·m⁻³, while only weak relationships between density and mechanical properties were observed (r² = 0.023–0.178). This suggests that factors related to drying conditions may contribute to variability in mechanical performance beyond the effect of density alone. Thus, the effects of the investigated drying conditions were property-specific rather than consistently attributable to drying temperature. Within the investigated material, these results indicate that the optimization of high-temperature drying schedules should consider both drying parameters and variability in mechanical properties.

Poplar wood ( Populus alba L.) was modified using a fully bio-based flame-retardant system based on furfuryl alcohol (FA) and ammonium phytate (AMP), catalysed by phosphoric acid (H₃PO₄). The treatment enables in-situ polymerization of FA to form a cross-linked poly(furfuryl alcohol) (PFA) network that immobilizes the nitrogen-phosphorus flame retardant within the wood structure. The modified wood exhibited a weight% gain of ≈ 22% and a density increase from 0.39 to 0.50 g cm ^− 3 . FTIR and SEM–EDX confirmed incorporation of phosphorus- and nitrogen-containing species throughout the wood matrix. Fire testing showed a substantial improvement in flame retardancy, including an increase in limiting oxygen index from 18% to 28%, a strong reduction in heat release and smoke production, and a more than six-fold increase in residual char. Thermogravimetric analysis demonstrated earlier dehydration and enhanced char formation, consistent with a synergistic condensed-phase mechanism of the P–N system. Importantly, the treatment exhibited high leach resistance (> 90%), and the enhanced fire performance was largely retained after a 14-day leaching procedure, confirming durable fixation of the flame-retardant components. The combined FA + AMP+H₃PO₄ system also reduced water uptake and improved surface hardness, while maintaining acceptable mechanical performance. The results demonstrate that phosphoric acid can act as a dual-function catalyst and supplementary phosphorus source, enabling a low-concentration, renewable, and durable flame-retardant modification of fast-growing poplar wood. This approach provides a sustainable pathway for producing multifunctional, high-performance lignocellulosic materials.

Surface pretreatment significantly influences the hygroscopic behavior of wood, which in turn affects surface stability when exposed to variable climatic conditions. This study focuses on how different surface pretreatment methods impact the performance of protective coating applied on spruce wood (Picea abies (L.) Karst.) during one year of natural weathering. Samples were prepared using various surface treatments: milling and sanding with grit sizes P40, P80, and P120, respectively. Two types of coatings were applied: a solventborne coating (ADLER Pullex Plus-Lasur) and a waterborne coating (DColor FK 47 UV Protect). The samples were exposed for 12 months at an outdoor testing site in Suchdol, Czech. Surface properties were assessed through color changes in the CIE Lab* space, gloss measurements (ISO 2813), contact angle analysis, and visual inspection. The results showed that exposure to UV radiation and microbial activities led to the gradual degradation of the optical properties and aesthetic appearance of the wood. Surfaces with greater roughness preserved their aesthetic properties more effectively, indicating a higher absorption of the coating. Untreated wood exhibited low water repellency, while the coated surface demonstrated enhanced hydrophobicity. Notably, the waterborne coating showed a temporary increase in contact angle around the sixth month, indicating surface clogging by dust particles. In contrast, the solventborne coating had a rapid decrease in wettability during the first nine months. These findings suggested the importance of surface pretreatment and coating type in maintaining the long-term performance and aesthetic appearance for wood used in exterior conditions.

Waste biomass presents both environmental challenges and opportunities for sustainable innovation. Converting biomass into biochar provides an environmentally sustainable method for waste valorization, with biochar demonstrating considerable potential for enhancing fire safety in various material applications. This study examines the fire performance of various biomass feedstocks (reed pellets, olive pits, wood chips, rubber waste) and their corresponding biochars, produced at 700 °C, using cone calorimeter tests. The biomass samples exhibited peak heat release rates (PHRR) ranging from 200 to 600 kW/m², whereas the PHRR of their biochars was significantly lower, ranging from 20 to 35 kW/m². Biochar derived from lignocellulosic biomass demonstrated more prolonged combustion behavior, with higher PHRR values, whereas rubber waste biochar exhibited the lowest PHRR (21.3 kW/m²) and total heat release (THR) (4.1 MJ/m²), highlighting its enhanced fire safety compared to its biomass counterpart. The composition of the parent biomass plays a crucial role in determining the biochar’s fire performance. These findings offer valuable insights into the selection of biochar for various applications, particularly as a filler in flame-retardant composites.

Cutting beech plywood using abrasive water jet (AWJ) technology represents a significant area of research due to increasing demands for precision, quality, and environmental sustainability in manufacturing processes within the woodworking industry. AWJ technology enables non-contact cutting of materials without causing thermal deformation or mechanical damage, which is crucial for preserving the structural integrity and mechanical properties of the plywood. This article investigates cutting beech plywood using technical methods using an abrasive water jet (AWJ) at 400 MPa pressure, with Australian garnet (80 MESH) as the abrasive material. It examines how abrasive mass flow rate, traverse speed, and material thickness affect AWJ lag, which in turn influences both cutting quality and accuracy. Measurements were conducted with power abrasive mass flow rates of 250, 350, and 450 g/min and traverse speeds of 0.2, 0.4, and 0.6 m/min. Results show that increasing the abrasive mass flow rate from 250 g/min to 350 g/min slightly decreased the AWJ cut width by 0.05 mm, while further increasing to 450 g/min caused a slight increase of 0.1 mm. Changes in traverse speed significantly influenced cut width; increasing the traverse speed from 0.2 m/min to 0.4 m/min widened the AWJ by 0.21 mm, while increasing it to 0.6 m/min caused a slight increase of 0.18 mm. For practical applications, it is recommended to use an abrasive mass flow rate of around 350 g/min combined with a traverse speed between 0.2 and 0.4 m/min when cutting beech plywood with AWJ. This balance minimizes jet lag and maintains high surface quality comparable to conventional milling. For thicker plywood, reducing the traverse speed closer to 0.2 m/min and slightly increasing the abrasive flow should ensure clean cuts without compromising surface integrity.

Electron microscopy (EM) is a key tool for studying the microstructure of wood; however, observing uncoated samples poses a challenge due to surface charging. This study aims to identify the critical voltage that allows for the effective observation of uncoated wood samples without significant loading. As part of the experiment, samples of different wood species were tested, including Acacia (Robinia pseudoacacia L.), Oak (Quercus robur L.), Maple (Acer pseudoplatanus spp.), Ash (Fraxinus excelsior L.), Spruce (Picea abies (L.) Karst.), Thermowood (Thermal modifed Spruce), Garapa (Apuleia leiocarpa), Ipé (Handroanthus spp.), Merbau (Intsia bijuga), and Massaranduba (Manilkara spp.). Several methods were tested for surface preparation for SEM analysis, including the use of a circular saw, a hand milling machine, and a microtome. The results show that the optimal voltage for observing uncoated wood samples varied depending on the wood species. Regarding the selection of wood species and the results obtained, it was found that uncoated samples could be effectively observed. This finding suggests that practical observations can be accelerated and more cost-effective, as all wood species exhibited the required voltage range of 1 kV to 1.6 kV. Additionally, it was determined that using a secondary electron detector was optimal for such observations, as it provided a sufficiently strong signal even at relatively low voltages. Conversely, when using a backscattered electron detector, it was more beneficial to use coated samples to achieve a sufficient signal at higher voltages. This study brings new knowledge that will facilitate further research and applications of electron microscopy in the study of other wood species or wood-based materials.