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This work presents a rapid and facile way to access the cell wall of wood with magnetic nanoparticles (NPs), providing insights into a method of wood modification to prepare hybrid bio-based functional materials. Diffusion-driven infiltration into Scots pine (Pinus sylvestris L.) sapwood was achieved using colloidal Fe3O4 nanoparticles. Optical microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray powder diffraction analyses were used to detect and assess the accessibility of the cell wall to Fe3O4. The structural changes, filling of tracheids (cell lumina), and NP infiltration depth were further evaluated by performing X-ray microcomputed tomography analysis. Fourier transform infrared spectroscopy was used to assess the chemical changes in Scots pine induced by the interaction of the wood with the solvent. The thermal stability of Fe3O4-modified wood was studied by thermogravimetric analysis. Successful infiltration of the Fe3O4 NPs was confirmed by measuring the magnetic properties of cross-sectioned layers of the modified wood. The results indicate the feasibility of creating multiple functionalities that may lead to many future applications, including structural nanomaterials with desirable thermal properties, magnetic devices, and sensors.

The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not been studied yet. To resolve this, the reaction was studied with solid-state 13C cross-polarization magic-angle-spinning (CP-MAS) and 31P MAS nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to reveal the formation of bonds between wood components, MA and SHP during the treatments to explain the formation of cross-linking and the possible fixation of phosphorus in wood. XPS, solid state 13C and 31P MAS NMR revealed the maleation of wood in the absence of SHP, whilst its presence led to forming a succinic adduct observed through the C-P bond formation, as evidenced by the loss of the maleate C=C bonds at around 130 ppm and the upfield shift of the peak at 165–175 ppm, which was also significantly smoothed, as well as the increase in a peak at 26 ppm due to the reaction between the maleate group and SHP; however, the C-P-C bond could not be unambiguously rationalized from the obtained data. On the other hand, a resonance line at 16 ppm in 31P MAS NMR and the peaks in the XPS P 2p spectrum suggested the formation of a cross-linked structure at low concentrations of SHP, which was more likely to be phosphonate (C-P-O) than organophosphinic acid (C-P-C). The results herein provide a greater fundamental understanding of the mechanisms involved in the reaction of wood, MA and SHP, providing further scope for improved treatment systems in the future. [ABSTRACT FROM AUTHOR]

Citric acid can be used as a bio-based binding agent in composites made from lignocellulosic material due to its crosslinking ability with hydroxyl groups via ester formation. Even though plenty of research has investigated diverse manufacturing conditions, with a focus on citric acid content and pressing temperature, an apparent knowledge gap persists regarding their effect on the properties of particleboards made from softwood sawdust. Furthermore, the optimal temperature for particleboards crafted from mostly non-wood lignocellulosic materials was found to be 180–200°C which is lower than that observed for softwood material in a prior study. This study aimed to systematically examine the effects of citric acid content and pressing temperature on particleboards derived from softwood sawdust. Results highlighted a positive correlation of both citric acid content and pressing temperature with mechanical and hygroscopic properties of the particleboards, the best results being achieved at 20 wt% citric acid and 220°C, exhibiting a thickness swelling of 9%, internal bonding strength of 0.77 MPa and a modulus of rupture of 4.3 MPa. This study served as a foundational framework for future investigations into the addition of other chemicals, offering a comprehensive understanding of their interactions with citric acid in particleboard manufacturing. [ABSTRACT FROM AUTHOR]

Wood, a fundamental material in construction, confronts durability and weathering challenges, notably UV-induced degradation leading to colour changes. This study investigated a novel treatment using citric acid and urea to enhance the UV stability of wood. The reaction between these compounds generates water-soluble fluorescent species and insoluble particles upon thermal treatment which may provide wood with UV protection. Specimens were treated with two different treatment methods and then exposed to 2016 h of accelerated weathering, during which colour was measured regularly. Citric acid and urea were either pressure impregnated into the wood and thermally reacted in situ during heat treatment or pre-reacted in the absence of wood with subsequent implementation into melamine formaldehyde (MF) and water-based surface coatings. The results showed that water-soluble fluorophore compounds were formed with both treatment methods. Accelerated weathering tests revealed significant colour changes over time, where specimens coated with a mixture of MF and fluorescent particles from the reaction between citric acid and urea, exhibiting the least alteration. The lowest colour change ΔE of 5.9 was observed for specimens coated with a MF-based coating containing 1 wt% of citric acid and urea thermally pre-reacted at a temperature of 180 °C, showcasing potential wood protection applications. [ABSTRACT FROM AUTHOR]

Sawn-timber drying is the wood industry's most time- and energy-consuming process. This process can be more efficient than the conventional method by elevating the dry-bulb temperature to above 100 °C in a high-temperature drying (HTD) process, which for some species shortens the drying process by up to 50% without deteriorating the quality. Comprehending the complex correlation between the wood drying physics at high temperatures and the anatomical features of the specific species, along with its mechanical and physical properties, is crucial, as it limited its application from being broadly implemented in industry and the necessity of generalizing this method for wood species. The present study has been conducted to comprehensively review and tackle the challenges of applying this method on various species and the consequences, such as high moisture content gradients resulting in stress residual, unevenness, and color changes. Energy, environment, and economic (3E) assessments of HTD were evaluated. The accelerated drying process in HTD reduces heat losses and air leaks, resulting in higher energy efficiency than the conventional methods. Furthermore, it was proved to be 20% economically in the long term. Confliction in reported studies, such as HTD's effect on permeability and volatile organic compound (VOC) emissions, was raised, highlighting the importance of further studies for generalizing this method to adapt appropriate drying schedules, focusing on Scandinavian species by referring to previous industrial trials. [ABSTRACT FROM AUTHOR]

Thermo-hydro-mechanical (THM) densification is a well-known wood modification procedure for improving the mechanical properties of low-density wood species, but its performance at elevated temperatures is not well understood. The objective of this study was to determine the bending behaviour of densified Scots pine at elevated temperatures. A total of 48 specimens (200 mm (longitudinonal) × 20 mm (radial) × 20 mm (tangential)) were tested to investigate the bending performance under constant temperatures at 25, 50, 125 and 175°C, respectively. It was found that the modulus of rupture (MOR) and modulus of elasticity (MOE) of both un-densified and densified pine decreased with increasing temperature. However, the densified wood exhibited more brittle shear failure but retained higher MOR and MOE than the untreated specimens treated at the same temperature level. In general, the results demonstrate that densification can be a potentially effective method to retain the mechanical properties of wood at elevated temperatures, thereby having a potential maintain the load-bearing capacity during and after fire. [ABSTRACT FROM AUTHOR]

The rise in energy consumption and the increase in the use of bio-based materials in the building sector, has led to the need to investigate the possibilities to use wood as a porous support material for phase change materials (PCMs), and thereby creating a thermal regulative wood-based product. This study investigated the influence of Kraft lignin-glyoxal prepolymer on the thermal-energy storage properties of wood modified with paraffin-type of PCM. The implementation of the modified wood involves preparing PCM emulsions, synthesising lignin-glyoxal prepolymer, and modifying wood with the PCM-Kraft lignin-glyoxal emulsion through vacuum-pressure impregnation. The infrared imaging suggested the ability of PCM-modified wood to delay the temperature changes, even with the introduction of Kraft lignin-glyoxal prepolymer. In conclusion, it is feasible to introduce thermal-energy storage property into wood with the addition of Kraft lignin-glyoxal prepolymer. Further studies will focus on the long-term thermal storage performance properties when this PCM system is subjected to repeated heating/cooling cycles. [ABSTRACT FROM AUTHOR]

To improve the resistance of wood to biological decay the Maillard reaction between introduced amines and wood cell-wall polymers can be utilised. However, initial studies in wood modification showed almost complete leaching of bicine and tricine from treated wood and the loss of beneficial effects. The objective of this study was to assess whether possible reactions of bicine or tricine with wood could be further enhanced and reaction products stabilised through the addition of glucose and/or citric acid. Thus, Scots pine sapwood specimens were impregnated with tricine or bicine, with or without glucose and citric acid, and then heated to a temperature of 160°C. The dimensional stability, degree of chemical leaching and mechanical properties were assessed. Overall, it was concluded that neither the presence of glucose nor citric acid did appear to enhance the reactivity of tricine or bicine. Anti-swelling efficiency (ASE) of 50% was observed for combined treatments of bicine/tricine and citric acid but the leaching resistance originated mainly from citric acid and glucose, with no indication for the retention of bicine or tricine. The presence of citric acid led to a strongly reduced modulus of rupture. [ABSTRACT FROM AUTHOR]

The purpose of this research study was to investigate the properties of polyurethane coatings based on lignin nano-particles. For this purpose, the prepared coatings were applied to pine wood surfaces and weathered artifi- cially. Subsequently, color and gloss of the coatings were measured before and after the weathering test. Field emission scanning electron microscopy (FE-SEM) micrographs prepared from the coatings showed that the average size of nano-particles in the polyurethane substrate was approximately 500 nm. Nuclear magnetic resonance (13C-NMR) spectroscopy showed that strong urethane bonds were formed in the nano-lignin-based polyurethane. Differential calorimetric analysis (DSC) test revealed that the glass-transition temperature (Tg) of lignin nanoparticles modified with diethylenetriamine (DETA) was 112.8°C and Tg of lignin nano-particles modified with ethylenediamine (EDA) was 102.5°C, which is lower than the Tg of un-modified lignin (114.6°C) and lignin modified with DETA (126.8°C) and lignin modified with EDA (131.3°C). The coatings modified with lignin nano-particles had a greater change in gloss. The lignin nano-particles in the modified coating are trapping hydroxyl radicals which reduces photoactivity and yellowing of the polyurethane by about 3 times compared to unmodified polyurethane coatings. After weathering test, the nano-lignin-based coating had a rougher surface with a lower contact angle (0.78°) compared to the unmodified polyurethane coating (0.85°). [ABSTRACT FROM AUTHOR]