Description succincte
(Anglais)
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The principles and mechanisms that determine the durability of THM densified wood against micro-organisms will be determined in a multi-disciplinary approach. Particular attention will be paid to the interactions that exist between the alterations of the wood constituents, the micro-morphology of the wood structure during processing of THM densification and the colonization and degradation by wood decay fungi. The dynamic structure of the project and the synthesis of the proposed studies, provides a sound basis for the development of an environmental friendly product that may have the potential to substitute the utilization of traditional wood preservatives
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Partenaires et organisations internationales
(Anglais)
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Dr. P. Navi, EPFL AT, BE, CH, CY, DE, DK, ES, FI, FR, GR, HR, HU, IE, IT, LT, LV, NL, NO, PL, PT, RO, SE, SI, SK, UK
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Résumé des résultats (Abstract)
(Anglais)
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A range of non-biocidal wood modification processes such as thermo-hygro-mechanical (THM) densified wood have been developed in recent years. High temperature, steam and compression are used to manufacture wood with superior strength and durability properties. Wood compressed using a THM process has a reduced set recovery, increased surface hardness and strength parallel to the grain, however the modification of hemicelluloses affects modulus of elasticity, (MOE) increasing embrittlement of wood. Since one potential field of THM-treated wood is utility class 4 (wood exposed to the soil), colonisation and degradation by soft-rot fungi was investigated in Norway spruce (Picea abies) and beech wood (Fagus sylvatica). In comparison to controls, significantly lower weight losses by soft-rot fungi were recorded in THM-treated spruce wood, but no such differences were found in beech which can be partly explained by the higher syringyl lignin content of the wood, which is more susceptible to soft-rot than that of wood species with higher guaiacyl content. On the basis of these results it must be concluded that TH-treated Norway spruce and THM-treated beech wood are susceptible to soft-rot and therefore inappropriate for application in contructions exposed to the soil. In THM and TH-treated wood of spruce and beech the impact of thermal treatment resulted in distinct chemical and micro-morphology alterations of the cell walls in close proximity to the specimen surface. The modification of cellulose and hemicelluloses resulted in a conspicuous reddish appearance of the outer cell rows due to staining of lignin with safranin.
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