No abstract

How well modified wood products perform may be influenced by their chemical compositions. Wood extractives are nonstructural constituents, many with specific biological properties, which affect the color, fragrance, hygroscopicity, durability, and acoustic properties and the drying and adhesion processes of wood. However, incomplete information is available on the extraction techniques and potential use of extractives as value-added chemical products. The main goal of this research was to explore the effects of thermo-vacuum treatment of Deodar cedar (Cedrus deodara Roxb.) and Italian alder (Alnus cordata Desf.) woods on the content and composition of extractives. Solvents with different polarities were used, including water, hexane, dichloromethane, methanol, and a benzene/ethanol mixture. Component groups in extracts were determined by gas chromatography in combination with mass spectrometry. Regardless of the treatment and solvent, the most representative extracts to be obtained from alder were acids/esters, whereas hydrocarbons were most frequently obtained from cedar. Our results revealed an interesting differential species-specific effect of solvents on the composition of extracts. Aside from benzene/ethanol, greater amounts of extracts were obtained from treated than from untreated alder, whereas the opposite was true for cedar, aside from methanol

The main purpose of this study was to investigate the hydrophobic effect and chemical changes induced by thermo-treatment and alkyl ketene dimer (AKD) on the surface properties of Alder (Alnus cordata (Loisel) Duby) wood before and after an artificial weathering test. Thermal treatment was conducted at a temperature of 200 °C for 4 h in a thermo-vacuum cylinder. Then, the paper sizing agent, AKD at different concentrations of a solution of 0.1%, 0.5% and 10% was used as a potential hydrophobizing reagent for untreated and thermally treated alder wood surfaces. The contact angle measurement, ATR-FTIR analysis and colour variation were carried out for the samples. The preliminary results revealed that the contact angle values of the wood materials increased with thermal modification. However, the influence of the thermal treatment on hydrophobicity was small when compared to the substantial effect of the AKD application in this respect, and also after the artificial weathering test. The FTIR analysis supported the hypothesis that AKD could make bonds chemically stable even when using a small concentration of AKD. The findings acquired in this work provide important information for future research and the utilization of the AKD on lesser-used wood species.

No abstract

The sweet chestnut (Castanea sativa Mill.) and European beech (Fagus sylvatica L.) are wood species largely present in the European forest area. The composition and relative variation of the secondary metabolites of chestnut and European beech wood under thermal effect is a little-explored area. The wood material was thermally modified at 170 °C for 3 h using a thermo-vacuum technology. Raw and modified wood extracts were obtained with aqueous extraction techniques in an autoclave, subsequently lyophilized, solubilized in ethyl acetate, and determined by Gas Chromatographic-Mass Spectrometric Analyses (GC-MS). In addition, the volatile compounds were determined by Solid-Phase Micro Extraction (SPME) analyses. As a general statement, the extraction in an autoclave produced a higher number of compounds in the modified chestnut and beech wood compared to unmodified wood material. Beech wood showed low degradation in the compounds after modification. Notably, squalene and ar-tumerone were the main bioactive compounds present in beech wood extractives. Chestnut, conversely, showed a greater degradation after thermo-modification. However, a reduction in chemical compounds in the modified samples was also observed. In this case, the main biologically active compounds detected only in the chestnut control samples were apocynin and ar-tumerone. The recovery of this residual wood material, before energy consumption, could provide a sustainable and environmentally friendly means of obtaining natural chemicals suitable for various industrial applications.

The aim of this research was to evaluate the multiple effects of both thermal modification and alkyl ketene dimer (AKD) on the deodar cedar (Cedrus deodara Roxb.) wood surface, before and after an irradiation test. The physical and chemical changes that occurred on the cedar wood samples due to the combined effect of these modifications were evaluated by measuring their wettability and colour and using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. The surface analysis by XPS showed the expected variability among the sampled layers for unmodified and thermally modified cedar wood samples and a uniform composition after the AKD coverage, regardless of their pre-treatments. The FTIR spectra before the irradiation test showed that the hydrophobicity of the samples was ensured by the formation of carbonyl groups originating from the reaction between the AKD and hydroxyl groups of cellulose, which is related to the presence of the absorption band between 1700 cm−1 and 1750 cm−1. Markedly, after the irradiation test, a degradation of the amorphous cellulose component occurred, showing that photoisomerisation to the enolic form took place. Overall, although uniform AKD coverage was derived from the surface analysis and wetting test, the combined ATR-FTIR results and colour measurements showed that it could not provide permanent protection to the underlying wood structure due to its own tendency to degrade mainly in colour over time, under the action of UV rays and atmospheric agents.

L'analisi XPS (X-ray Photoelectron Spectroscopy) unitamente ad altre tecniche di spettroscopia, come l'IR a trasformata di Fourier (FTIR), consente di verificare il cambiamento nella composizione chimica dei campioni in esame. In particolare, la spettroscopia fotoelettronica a raggi X permette di sondare la superficie dei materiali, comprendere le modifiche chimiche su di essa avvenute, individuare gli elementi chimici che la compongono e, inoltre, il loro stato di ossidazione. Il trattamento con raggi UV è uno dei metodi utilizzato per riprodurre in laboratorio gli effetti di lungo termine che si hanno sulla superficie del materiale legnoso a seguito dell'esposizione solare. Lo scopo di questo studio è stato quello di produrre artificialmente, con l'ausilio di una lampada UV-C, gli effetti che le radiazioni UV hanno sul legno di cerro (Quercus cerris L.) e di valutare gli eventuali cambiamenti a livello chimico con l'uso della tecnica XPS. L'analisi dei risultati indica che la radiazione UV-C causa cambiamenti irreversibili nella composizione chimica dei campioni legnosi attraverso fenomeni di foto-ossidazione e fotodegradazione.