Simultaneous Improvement of Surface Wettability and UV Resistance of Wood with Lignin-Based Treatments.

Recent advancements in wood modification aim to enhance the inherent qualities of this versatile biological material, which includes renewability, ease of processing, and thermal insulation. This study focuses on evaluating the effectiveness of lignin as a protective agent for less durable wood species, namely, Pinus nigra and Fagus sylvatica L. The impregnation of wood with three various forms of lignin, such as kraft lignin, acetylated kraft lignin, and lignin nanoparticles, was carried out using the vacuum technique at room conditions. The results showed that the treatments significantly improve the hydrophobicity of wood surfaces, particularly in pine wood, and provide protection against UV ageing. Additionally, the treatments contributed to the stabilisation of moisture content at different humidity levels. Although slight colour variations were observed, their impact on the visual appearance was minimal, and the thermal analysis confirmed enhanced thermal properties. Additionally, plasma treatment further enhanced hydrophobicity after treatments, offering potential benefits in terms of moisture resistance and durability. The findings of this study highlight the promising effects of lignin-based treatments on wood properties, providing sustainable solutions for wood protection in various sectors. However, further optimisation is needed to fully explore the potential of lignin and lignin nanoparticles.

Fungal colonisation on wood surfaces weathered at diverse climatic conditions.

Natural weathering test at two different European climatic zones were conducted to investigate simultaneously both, the fungal colonisation and weathering process of Scots pine wood (Pinus sylvestris L.). The hypothesis was that the wood performing differently in various climate conditions might affect fungal infestation. The colour changes, wettability, and glossiness were measured as indicators of weathering progress of wood together with an assessment of fungal diversity. Different intensities in weathering, occupancy, and colonisation of fungi on wooden surface were detected. A higher number of fungal species was found on wood exposed to the warm temperate climates compared to subarctic or boreal climates. The dominant fungal species in both locations were from the genera Cladosporium and Aureobasidium.

Potential of lignin multifunctionality for a sustainable skincare: Impact of emulsification process parameters and oil-phase on the characteristics of O/W Pickering emulsions.

Colloidal lignin particles (CLPs) from softwood kraft lignin were evaluated as a multifunctional ingredient to prepare bio-based oil-in-water (O/W) Pickering emulsions. After a preliminary screening, three Pickering emulsions systems were formulated using orange, coconut, and paraffin oils, at varying concentration of CLPs, oil/water ratio, and by applying two-step homogenisation processes (rotor-stator homogenisation followed by ultrasonication). Ultrasonication as a second homogenisation step considerably enhanced the emulsification efficiency, generating emulsions with smaller droplet size and less polydisperse distribution. Furthermore, the effect of ultrasonication on the characteristics of emulsions and the stability of the systems was evaluated over time. The oil content and type, the concentration of CLPs, and the homogenisation methods significantly influenced the characteristics of the emulsions and drop size. Higher concentrations of oil and CLPs favoured the formation of the emulsion and contributed to higher physical stability after 120 days of monitoring. The in vitro Sun Protection Factor (SPF) results demonstrated that the incorporation of natural oils containing phenolic compounds in Pickering formulations improves the SPF value of emulsions, showing an interesting synergic effect between lignin particles and vegetable oils, which was not observed in the case of paraffin oil. Furthermore, the broad-spectrum sun blocker of Pickering emulsions was confirmed by the values of UVA/UVB between 0.74 and 0.90 and Cλ > 380.

Surface chemistry and bioactivity of colloidal particles from industrial kraft lignins.

The morphology control of lignin through particle size reduction to nanoscale seems to be a suitable conversion technology to overcome the intrinsic limitations of its native form to develop a wide range of biomaterials with high performance. Colloidal lignin particles (CLPs) in the range of 150-200 nm were synthesised from hardwood and softwood kraft lignins by the solvent shifting method. The initial molecular features of kraft lignins were evaluated in terms of purity, molecular weight distribution, and chemical functionalities. The impact of the lignin source and structure on the morphology, size distribution, and surface chemistry of CLPs was evaluated by particle size analyser, SEM, TEM and 1H NMR. The results evidenced the influence of the botanical origin on the morphology and surface chemistry of particles. Furthermore, the antioxidant properties and cytotoxicity of lignins and corresponding CLPs, towards lung fibroblast cells were compared. CLPs from hardwood kraft lignins exhibited higher antioxidant power against DPPH free radical and a higher cytotoxic effect (IC30 = 67-70 µg/mL) against lung fibroblast when compared to CLPs from softwood kraft lignin (IC30 = ~91 µg/mL). However, the cytotoxicity of these biomaterials was dose-dependent, suggesting their potential application as active ingredients in cosmetic and pharmaceutic products at low concentrations.

One-Step Lignin Refining Process: The Influence of the Solvent Nature on the Properties and Quality of Fractions.

Heterogeneity of kraft lignin is one of the main limitations for the development of high-performance applications. Therefore, refining lignin using organic solvents is a promising strategy to obtain homogenous fractions with controlled quality in terms of structure and properties. In this work, one-step refining processes for hardwood kraft lignin using nine organic solvents of different chemical nature and polarity were carried out with the aim of investigating and understanding the effect of the type of organic solvent on the quality of resulting fractions. Structural features of both soluble and insoluble lignin fractions were assessed by GPC, Py-GC-MS, and FTIR linked to PCA analysis. Moreover, functional properties such as physical appearance, hygroscopicity, antioxidant capacity, and thermal properties were evaluated. The results evidenced the relationship between the nature and polarity of the solvents and the properties of the obtained soluble and insoluble fractions.

Characterization of the Compounds Released in the Gaseous Waste Stream during the Slow Pyrolysis of Hemp (Cannabis sativa L.).

This study aims to characterize and valorize hemp residual biomass by a slow pyrolysis process. The volatile by-products of hemp carbonization were characterized by several methods (TGA, UV-VIS, TLC, Flash Prep-LC, UHPLC, QTOF-MS) to understand the pyrolysis reaction mechanisms and to identify the chemical products produced during the process. The obtained carbon yield was 29%, generating a gaseous stream composed of phenols and furans which was collected in four temperature ranges (F1 at 20-150 °C, F2 at 150-250 °C, F3 at 250-400 °C and F4 at 400-1000 °C). The obtained liquid fractions were separated into subfractions by flash chromatography. The total phenolic content (TPC) varied depending on the fraction but did not correlate with an increase in temperature or with a decrease in pH value. Compounds present in fractions F1, F3 and F4, being mainly phenolic molecules such as guaiacyl or syringyl derivatives issued from the lignin degradation, exhibit antioxidant capacity. The temperature of the pyrolysis process was positively correlated with detectable phenolic content, which can be explained by the decomposition order of the hemp chemical constituents. A detailed understanding of the chemical composition of pyrolysis products of hemp residuals allows for an assessment of their potential valorization routes and the future economic potential of underutilized biomass.

Multi-sensor data fusion and parallel factor analysis reveals kinetics of wood weathering.

Understanding mechanisms of materials deterioration during service life is fundamental for their confident use in the building sector. This work presents analysis of time series of data related to wood weathering acquired at three scales (molecular, microscopic, macroscopic) with different sensors. By using several complementary techniques, the material description is precise and complete; however, the data provided by multiple equipment are often not directly comparable due to different resolution, sensitivity and/or data format. This paper presents an alternative approach for multi-sensor data fusion and modelling of the deterioration processes by means of PARAFAC model. Time series data generated within this research were arranged in a data cube of dimensions samples × sensors × measuring time. The original protocol for data fusion as well as novel meta parameters, such as cumulative nested biplot, was proposed and tested. It was possible to successfully differentiate weathering trends of diverse materials on the basis of the NIR spectra and selected surface appearance indicators. A unique advantage for such visualization of the PARAFAC model output is the possibility of straightforward comparison of the degradation kinetics and deterioration trends simultaneously for all tested materials.

Fractionation of lignin using organic solvents: A combined experimental and theoretical study.

Refining of industrial lignin to produce homogeneous fractions is essential for high-value applications. However, the understanding of key interactions between a variety of solvents with lignin polymer is still uncertain. In this work, single-step fractionation of industrial hardwood kraft lignin (HKL) using organic solvents of different polarities - ethanol, acetone, diethyl ether and hexane - was investigated by combining an experimental and theoretical approach. Experimental results revealed that higher polarity solvents (ethanol and acetone) exhibited higher solubility yield compared to moderate and low polarity solvents. The chemical differences between lignin fractions were proven by pyrolysis gas chromatography mass spectrometry and near infrared spectroscopy. Density functional theory (DFT) results indicated that ethanol presented higher interaction energy followed by acetone, diethyl ether and hexane, which was consistent with experimental findings. Hydrogen bond and non-covalent interaction results from DFT demonstrated that the predominant interaction was found for high polarity of ethanol over other solvents and γ-OH in the lignin model is the key site.

Multiscale modelling investigation of wood modification with acetic anhydride.

Density functional theory (DFT) and molecular dynamics (MD) simulations were employed to investigate the interaction of cellulose and lignin with acetic anhydride for explaining the wood modification process. Cellulose was modelled with a cellobiose unit and dibenzodioxocin was used to represent the lignin model. Results obtained from both methods revealed that acetic anhydride interacted substantially more with the cellobiose model than the lignin model. The interaction energy of cellobiose-acetic anhydride was higher (about 20 kJ mol-1) than that of lignin-acetic anhydride. DFT results on hydrogen bonding indicated that the hydroxyl group from cellobiose and the aromatic hydroxyl group from lignin models have similar energy values, which explain the equal strength of hydrogen bond interaction. The same trend was also obtained for the substitution of acetyl group in the hydroxyl group. MD results have also predicted that acetic anhydride forms a stronger interaction with cellobiose than with the lignin model, and these findings were in agreement with the DFT results.

Development of Low-Cost Portable Spectrometers for Detection of Wood Defects.

Portable spectroscopic instruments are an interesting alternative for in-field and on-line measurements. However, the practical implementation of visible-near infrared (VIS-NIR) portable sensors in the forest sector is challenging due to operation in harsh environmental conditions and natural variability of wood itself. The objective of this work was to use spectroscopic methods as an alternative to visual grading of wood quality. Three portable spectrometers covering visible and near infrared range were used for the detection of selected naturally occurring wood defects, such as knots, decay, resin pockets and reaction wood. Measurements were performed on wooden discs collected during the harvesting process, without any conditioning or sample preparation. Two prototype instruments were developed by integrating commercially available micro-electro-mechanical systems with for-purpose selected lenses and light source. The prototype modules of spectrometers were driven by an Arduino controller. Data were transferred to the PC by USB serial port. Performance of all tested instruments was confronted by two discriminant methods. The best performing was the microNIR instrument, even though the performance of custom prototypes was also satisfactory. This work was an essential part of practical implementation of VIS-NIR spectroscopy for automatic grading of logs directly in the forest. Prototype low-cost spectrometers described here formed the basis for development of a prototype hyperspectral imaging solution tested during harvesting of trees within the frame of a practical demonstration in mountain forests.

Machinability of Minor Wooden Species before and after Modification with Thermo-Vacuum Technology.

The influence of the thermal modification process on wood machinability was investigated with four minor species of low economic importance. A set of representative experimental samples was machined to the form of disks with sharp and dull tools. The resulting surface quality was visually evaluated by a team of experts according to the American standard procedure ASTM D-1666-87. The objective quantification of the surface quality was also done by means of a three dimensions (3D) surface scanner for the whole range of grain orientations. Visual assessment and 3D surface analysis showed a good agreement in terms of conclusions. The best quality of the wood surface was obtained when machining thermally modified samples. The positive effect of the material modification was apparent when cutting deodar cedar, black pine and black poplar in unfavorable conditions (i.e., against the grain). The difference was much smaller for an easy-machinability specie such as Italian alder. The use of dull tools resulted in the worst surface quality. Thermal modification has shown a very positive effect when machining with dull tools, leading to a relevant increment of the final surface smoothness.

Solid state NMR and IR characterization of wood polymer structure in relation to tree provenance.

(13)C nuclear magnetic resonance and mid-infrared spectroscopies were used for characterizing changes in the chemical structure of wood polymers (cellulose, hemicellulose and lignin) in relation to the tree growth location. Samples of three provenances in Europe (Finland, Poland and Italy) were selected for studies. The requirement was to use untreated solid wood samples to minimize any manipulation to the nanostructure of native wood. The results confirm that the chemical and physical properties of samples belonging to the same wood species (Picea abies Karst.) differ due to the origin. Both FT-IR and dynamic NMR spectroscopies were able to correctly discriminate samples originating from three different provenances in Europe. Such methods might be very useful for both, research and understanding of wood microstructure and its variability due to the growth conditions.