Rene Herrera Diaz

This study investigates the colour evolution of Norway spruce wood during one year of natural weathering across multiple European locations as part of a Round Robin experiment. Colour measurements ( CIE Lab ) were performed on samples with monthly-resolved exposure duration to quantify discolouration and determine total colour change ( ΔE ). The results show that weathering induces rapid colour modification, with the most pronounced changes occurring within the first month of exposure. A clear two‑stage behaviour was identified: an initial colour‑enrichment phase, characterised by increases in CIE a and CIE b , followed by progressive decolouration and greying, reflected primarily through decreases in CIE L . Although the fundamental mechanisms of photodegradation were consistent across all sites, the rate and extent of discolouration varied substantially with local climatic conditions. Samples exposed in Turkey exhibited the highest ΔE values, whereas those in the UK showed the lowest. This difference is consistent with expected climatic variations in solar radiation, moisture conditions, and temperature fluctuations between the two locations, which are known to influence weathering kinetics. The dataset provides a robust basis for linking colour change and its dynamics with site‑specific climate parameters enabling the development of a dedicated dose-response model.

High-performance nonisocyanate polyurethanes with circular end-of-life options remain difficult to obtain because polyhydroxyurethane networks often combine limited mechanical performance with poor reprocessability. Here, furan-functionalized polyhydroxyurethane oligomers were crosslinked with a trifunctional maleimide through thermoreversible furan–maleimide Diels–Alder chemistry to obtain stiff, thermally reprocessable networks. Two precursor architectures were compared: a fossil-based diepoxide-derived oligomer and a partially biobased epoxidized soybean oil-derived oligomer. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy confirmed cyclic carbonate formation, hydroxyurethane formation, and Diels–Alder crosslinking. Differential scanning calorimetry, in situ infrared spectroscopy, rheology, swelling experiments, and three-point bending tests were used to define the thermal reprocessing window and assess network recovery. The resulting networks reached flexural moduli of 3.9 and 1.7 GPa, respectively, and retained most of their mechanical performance after compression-molding recycling. Reprocessing was governed by a narrow temperature window where retro-Diels–Alder dissociation enables flow while irreversible maleimide side reactions remain limited. These results establish precursor architecture as a key parameter for balancing stiffness, reprocessability, and topology preservation in circular polyhydroxyurethane thermosets.

Wood science has long been shaped by a fundamental challenge: the properties that determine material performance are intrinsically heterogeneous, anisotropic, scale-dependent, and sensitive to environmental and processing conditions

This study presents a wood modification process using Fast Pyrolysis Bio-Oil (FPBO) as a fully biobased alternative to conventional, fossil-based and potentially toxic preservatives such as copper salts, organic biocides, and creosote. Standard FPBO was used in the development of 10 formulations, which were systematically characterized in terms of pot life, viscosity evolution, density, and pH. Radiata pine samples were subsequently impregnated using a bench-scale reactor, with specimens prepared in multiple geometries to assess treatment performance across different dimensions. The modified wood was comprehensively characterized with respect to moisture uptake, dimensional stability, density, mechanical strength, fixation efficiency, biological durability, and VOC emissions. Additional screening focused on properties relevant to outdoor applications, including aesthetic appearance and colour uniformity after UV exposure. The results enabled the identification of three top-performing formulations, treatments H, A, and E, which exhibited the most favourable balance between durability, environmental performance, and structural integrity. Overall, the findings demonstrate the strong potential of FPBO-based impregnation as a sustainable, multifunctional, and high-performance alternative for advanced wood protection systems.

Tannins are polyphenolic compounds found in a variety of plant tissues, including bark, roots, wood, leaves, fruits, and algae. They may also be synthesized within galls, abnormal plant growths res...

This study investigated the potential use of pyrolysis liquid from bark as an anti-fungal substance against food decaying fungi. Four different fractions of pyrolysis liquid were collected during variable temperature phases of the pyrolysis process: F1 (25–260 °C), F2 (260–512 °C), F3 (512–800 °C), and F4 (800–25 °C). The thermal degradation of bark material was assessed using TGA analysis. The concentration, pH, total phenolic content, and functional groups of the liquid samples were determined. Additionally, the molecular composition was examined using UHPLC and QToF mass spectrometry methods. Fungal species were isolated from bell pepper and animal fat and identified through microscopic observation and DNA sequencing. The anti-fungal activity of the liquid fractions was evaluated using the disk diffusion test. The obtained degradation thermograms had a typical shape characteristic of lignocellulosic materials, revealing different thermal degradation phases of the bark. These phases served as a basis for the collection of the pyrolysis liquid in fractions, which were expected to differ in properties and molecular composition. In the fractions collected above 260 ºC (F2, F3, F4), the pyrolysis liquid presented an acidic character, resulting from the complex thermochemical reactions that occur during the slow pyrolysis of bark. F2 had the highest concentration of total phenolic compounds (6.46 mg GAE/g extract) while F1 and F4 contained only negligible amounts. The FTIR spectra of F2 displayed additional peaks compared to other samples which provided information on the occurrence of various compounds. The reversed phase UHPLC-UV analysis revealed that furfural, 5-hydroxymethyl furfural, and 5-methyl furfural were the most abundant compounds, and F2 had the highest concentration of summed furans (570 µg/mL) among all samples. The morphological assessment and DNA sequence analysis of the fungal strains revealed that Penicillium crustosum and Cladosporium sp were isolated from fat and bell pepper, respectively. The antifungal activity of the liquid fractions was limited due to their low concentration (ranging from 0.24% to 0.01% (v/v)), with only minor inhibition observed for F2, indicated by a small inhibition zone of approximately 1 mm around the 10 mm filter paper. However, concentrating the fraction F2 up to 1% (v/v) demonstrated a stronger inhibitory zone against Cladosporium pseudocladosporioides and Penicillium sp., indicating its antifungal potential at higher concentrations. Overall, the pyrolysis liquid demonstrated promising antifungal activity, particularly after concentration, with F2 exhibiting the highest bioactivity and strongest inhibition effect. These findings highlight its potential for controlling food-decaying fungi while emphasizing the need for further purification, toxicity assessments, and application studies to ensure its feasibility for agro-industrial applications. Graphical Abstract

Finishing coatings in the wood-based composites industry not only influence the final appearance of the product but also serve to protect against fungi and molds and reduce the release of harmful substances, particularly formaldehyde and volatile organic compounds (VOCs). Carbon-rich materials, such as those derived from birch bark extraction, specifically suberin acids, can fulfill this role. Previous research has demonstrated that adding suberin acid residues (SAR) at 20% and 50% by weight significantly enhances the gas barrier properties of surface-finishing materials based on poly(lactide) (PLA) and polycaprolactone (PCL), particularly in terms of total VOC (TVOC) and formaldehyde emissions. This study aims to explore whether these properties can be further improved through the incorporation of nano-zinc oxide (nano-ZnO). Previous research has shown that these nanoparticles possess strong resistance to biological factors and can positively affect the characteristics of nanofilms applied as surface protection. The study employed PLA and PCL finishing layers blended with SAR powder at 10% w/w and included 2% and 4% nano-zinc oxide nanoparticles. The resulting blends were milled to create a powder, which was subsequently pressed into 1 mm-thick films. These films were then applied to raw particleboard surfaces. TVOC and formaldehyde emission tests were conducted. Additionally, the fungal resistance of the coated surfaces was assessed. The results showed that PLA/SAR and PCL/SAR composites with the addition of nano-zinc oxide nanoparticles exhibited significantly improved barrier properties, offering a promising avenue for developing biodegradable, formaldehyde-free coatings with enhanced features in the furniture industry. Furthermore, by utilizing SAR as a post-extraction residue, this project aligns perfectly with the concept of upcycling.

Finishing coatings in the wood-based composites industry not only influence the final appearance of the product but also serve to protect against fungi, and molds, and reduce the release of harmful substances, particularly formaldehyde and volatile organic compounds (VOCs). Carbon-rich materials, such as those derived from birch bark extraction, specifically suberin acids, can fulfil this role. Previous research has demonstrated that adding suberin acid residues (SAR) at 20% and 50% by weight significantly enhances the gas barrier properties of surface finishing materials based on poly(lactide) (PLA) and polycaprolactone (PCL), particularly in terms of Total VOC (TVOC) and formaldehyde emissions. This study aims to explore whether these properties can be further improved through the incorporation of nano-zinc oxide (nano-ZnO). Previous research has shown that these nanoparticles possess strong resistance to biological factors and can positively affect the characteristics of nanofilms applied as surface protection. The study employed PLA and PCL finishing layers blended with SAR powder at 10% w/w and included 2% and 4% nano-zinc oxide nanoparticles. The resulting blends were milled to create a powder, which was subsequently pressed into 1 mm thick films. These films were then applied to raw particleboard surfaces. TVOC and formaldehyde emission tests were conducted. Additionally, the fungal resistance of the coated surfaces was assessed. The results showed that PLA/SAR and PCL/SAR composites with the addition of nano-zinc oxide nanoparticles exhibited significantly improved barrier properties, offering a promising avenue for developing biodegradable, formaldehyde-free coatings in the furniture industry with enhanced features. Furthermore, by utilizing SAR as a post-extraction residue, this project aligns perfectly with the concept of upcycling.

The goal of this study is to comprehensively evaluate the natural weathering performance of three wood species representing hardwood and softwood modified with the acetylation process. Alder (Alnus glutinosa L.), beech (Fagus sylvatica L.), and radiata pine (Pinus radiata D. Don) were characterised by various techniques to determine the aesthetical, chemical, and physical changes. The overall aesthetic performance of the investigated species was similar, with all showing a change in appearance after 9 months of exposure. However, the multi-sensor approach used for characterisation revealed differences in weathering behaviour related to surface erosion, wettability, and changes in chemical composition between the investigated species. An increase in the surface roughness observed for both hardwoods was associated with the erosion of the wood surface and the leaching of photodegraded chemical components. On the contrary, values of Sa remained relatively constant for acetylated radiata pine. Acetylated pine wood exhibited lower susceptibility to bleaching at the initial stage of the weathering process (3 months) and represented a more constant CIE L* compared to the investigated hardwood species. The contact angle measured with water gradually decreased in the case of acetylated radiata pine for up to six months, then it plateaued with a slight oscillation around 15°. For both hardwood species, the big drop was observed already after three months, followed by rather similar values. The PCA of IR spectra highlighted different mechanisms in the weathering of acetylated softwood and hardwood. The acetylated hardwood samples showed higher thermal stability than acetylated radiata pine. Experimental findings provide a comprehensive understanding of the long-term performance of acetylated wood, which directly influences its practical applications by enhancing design strategies, maintenance planning, product development, market acceptance, and overall sustainability. Performed tests have demonstrated the potential of underutilised hardwood species, enhanced through the acetylation process, to serve as alternative cladding materials to commonly used acetylated radiata pine.