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Modification can significantly improve the service life of wood products, however, from the environmental perspective, the process has its drawbacks causing excessive influence in some specific impact categories. To reduce the impact that is characteristic of each individual modification process and to gain benefits due to synergy, the potential of using a combined treatment (copper azole impregnation + thermal modification) is evaluated. The results show that a combined treatment can provide enhanced environmental performance over each individual modification. [ABSTRACT FROM AUTHOR]

The aim of the present research was to obtain a wood material with improved service properties, by combining two industrially used processes – namely a thermo-hydro treatment (THT) and an impregnation (Imp) with a commercial biocide – through the application of both a lower preservative retention and lower modification temperature, respectively. In the study, specimens from Scots pine (Pinus sylvestris L.) sapwood were used. The properties of the wood obtained with the sequence Imp-THT were extensively studied. Impregnation was performed in a pilot scale autoclave by a vacuum-pressure-vacuum process using a copper-azole type wood preservative, whilst THT was carried out in a WTT laboratory pilot device in a water vapour medium under elevated pressure. To improve physical properties while maintaining strength properties, the THT regime 160°C/1 h was used. The properties (strength, swelling, water uptake, colour, biocide (Cu) fixation properties as well as bioresistance to rot fungus) of combined treated pine wood were compared with those of the wood obtained in the respective separate processes. [ABSTRACT FROM AUTHOR]

The objective of the present study was to investigate the interaction between Cu-containing preservatives and birch (Betula spp.) and pine (Pinus sylvestris L.) wood, modified at a relatively mild temperatures (150 - 180°C). The disposition of wood to absorb water was evaluated by capillary absorption (CA) tests through the specimens' tangential and radial surface. Changes in wood drying characteristics due to thermal modification (TM) were evaluated by monitoring wood moisture dynamics after impregnation. In order to assess the capacity of wood to absorb preservatives, a vacuum/pressure process was used to impregnate small specimens for which uniform saturation into the entire volume can easily be reached. Quantitative determination of copper Cu content in the specimens was performed by using atomic absorption spectroscopy (AAS). The fixation of the absorbed Cu was evaluated by subjecting the specimens to leaching procedures according to EN 84 and assessing the ratio of retained Cu in the specimens. The CA test showed deceleration of capillary absorption in TM birch wood through both surfaces, with similar absorption rates regardless of treatment temperatures. A significant increase in the absorption rate through the tangential surface was recorded for TM pine wood and the increase was greater for specimens treated at higher temperatures. The results of moisture content monitoring showed a similar reduction in the drying rate due to thermal modification regardless of species. Comparing wood of one species with similar densities, less preservative was absorbed by TM wood. However, the results of AAS showed that, in comparison with unmodified wood, 10% (birch) and 25% (pine) more Cu per one gram of wood was introduced during impregnation. Nevertheless, TM also resulted in higher Cu leaching rates for both species. [ABSTRACT FROM AUTHOR]

The chemical structure of wood changes significantly during thermal modification, significantly influencing the behaviour of wood during weathering. In this study, the effect of different wavelength ranges on thermally modified and unmodified aspen (Populus tremula L.) wood during solar irradiation was investigated. Irradiation was performed by exposing wood to natural solar irradiation under filters transmitting different wavelength ranges. For both woods, the magnitude of characteristic change (discolouration, changes in reflectance, and chemical composition) clearly depended on the solar wavelength bands, but the trends of the changes differed. For unmodified wood, the magnitude of the characteristic changes increased as the portion of shortwavelength radiation in the light increased. However, UV radiation was not found to be the dominant factor influencing changes in thermally modified wood during solar irradiation. The colour and chemical structure of thermally modified wood changed substantially for all studied irradiation conditions. [ABSTRACT FROM AUTHOR]

To replace traditional wood preservatives, containing heavy metals, different methods for modification of wood (thermal and chemical, use of organic preservatives, etc.) are proposed for enhancing the biological resistance of wood. Great energy consumption, high cost of modifiers and their unfavourable impact on the environment are assigned to drawbacks of these methods. In the present work, to enhance the durability of wood, it is proposed to introduce into wood channels (canals, lumens and intercellular spaces) lignin - a substance that is both wood- and environment-friendly. Pine wood samples were impregnated with alkali lignin aqueous solutions under vacuum. Despite the high hydrophility of modified wood, its exposure on cultures of brown and white rots during 6 weeks has shown the high efficiency of lignin for enhancing the durability of wood with regard to both rots. Sorption of water study and density measure demonstrate that, upon modification, the interstructural bonds become weaker, the volume of narrow (micro- and meso-) pores increases almost twice, and the volume of broad pores (macropores) of wood decreases by third. It is concluded that lignin fills partially (by 13%) the channels, blocking the entries to them and hampering the diffusion of fungal enzymes to the cell wall surface. [ABSTRACT FROM AUTHOR]

Pentru înlocuirea produselor clasice de protecție a lemnului cu conținut de metale grele, sunt propuse diferite metode de modificare a lemnului (termice şi chimice, utilizarea biocidelor organice etc.) în vederea îmbunătățirii rezistenței la biodegradare. Consumul mare de energie, costul ridicat al agenților de modificare şi impactul lor nefavorabil asupra mediului constituie elemente ce frânează dezvoltarea acestor tehnologii. În studiul de față se propune pentru îmbunătățirea durabilității lemnului introducerea ligninei -- o substanță prietenoasă atât față de lemn cât şi de mediu - în golurile lemnului (canale, lumen celular şi spații intercelulare). Probe de lemn de pin au fost impregnate sub vid cu soluții apoase de lignină alcalină. În ciuda caracterului pronunțat hidrofil al lemnului modificat expunerea sa la atacul ciupercilor de putregai brun şi alb pe medii de cultură timp de 6 săptămâni a arătat eficiența ridicată a ligninei în creşterea durabilității lemnului față de ambele tipuri de putregai. Studii privind absorbția de apă şi densitatea au demonstrat o slăbire a legăturilor interstructurale în urma modificării, volumul porilor înguşti (micro- şi mezo-) crescând aproape de două ori, în timp ce volumul porilor largi (macro-pori) a scăzut cu o treime. S-a ajuns la concluzia că lignina umple parțial (până la 13%) canalele, blocând intrările în acestea, împiedicând astfel difuzia enzimelor ciupercilor spre suprafața peretelui celular. [ABSTRACT FROM AUTHOR]