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In this work, bright field microscopy and scanning electron microscopy tests were carried out to find the effect of acetylation on the microscopic structure of hornbeam wood, furthermore to analyze the differences between decayed samples at microscopic level. Several methods of sample preparation (water, acetone) and staining (safranin, astra blue, 1% solution of potassium permanganate) were also tested and compared. Native hornbeam wood was successfully acetylated, which was confirmed by the limited staining effect of safranin. Acetylation did not damage the wood microstructure and significantly increased the cell-wall thickness by 7.0%. The pits of acetylated hornbeam were much narrower, probably due to permanent cell-wall swelling. New brown deposits were found in parenchyma cells of acetylated hornbeam. Each cell contained a small amount of an insoluble substance, which led to the hypothesis that the natural content of living cells became insoluble during acetylation. Further investigation is needed to determine what substance was created during acetylation. In the case of samples which were tested for fungi resistance against Coniophora puteana, Rhodonia (Poria) placenta, and Trametes (Coriolus) versicolor, microscopic studies showed that fungi were able to colonize acetylated cell lumina without visible degradation or mass loss (∼1%). [ABSTRACT FROM AUTHOR]

Degradation by wood-rotting fungi has been studied in Lignamon and beech wood modified by the Lignamon process. Different treatments that are used during Lignamon process were applied: gaseous ammonia treatment, densification (20 and 40% compression ratio) and heat treatment (180°C). These specimens were exposed to Trametes versicolor and Coniophora puteana for 16 weeks and the mass loss was evaluated. Changes in chemical structure, nitrogen content and pH caused by individual treatments or by fungal activity were also determined. The wood nitrogen content increased after ammonia treatment (1.0%) and was the highest in Lignamon (1.4%), its release during water leaching was very slow. The chemical analysis of wood revealed slight changes in the polysaccharide and lignin content in wood treated with ammonia. Bonded nitrogen was in the form of amides, which were partially thermally degraded by heat treatment. Neither densification nor heat treatment led to better resistance of wood against fungi, while ammonia treatment significantly restricted mass losses (C. puteana 2.5%; T. versicolor 7.5%) compared to untreated wood (both about 30%). Lignamon showed the best fungi resistance (mass loss < 5%), which was probably caused by the combined effect of hemicellulose degradation, an increased nitrogen content, and wood densification. [ABSTRACT FROM AUTHOR]

This study was carried out in order to determine the efficacy of microwave (MW) plasticization for wood densification purposes. The plasticization process was carried out using a continuous feed laboratory MW at a frequency of 2.45 GHz. European beech ( Fagus sylvatica L.) specimens measuring 50 mm × 40 mm × 8 mm were MW treated (plasticized) with an output of 3.5 kW at a conveyor speed of 0.4 m/min. Afterwards, MW plasticized specimens were densified with a ratio of 50%. Microscopic structure changes of densified wood were detected using a scanning electron microscope (SEM) and density profiles were measured using the X-ray densitography. An average density of 677 kg m and 771 kg m increased significantly to 951 kg m for radially densified and to 1194 kg m for tangentially densified specimens. X-ray densitography results show uniformity of density profiles through specimen thickness, which confirmed the evenly plasticized volume of wood. Microscopic structure observation revealed that the MW plasticization was not accompanied by any fractures, and deformations present in the densified wood were due to viscoelastic buckling of cell walls without crack propagation. Therefore, MW treatment can be considered as an effective method for wood plasticization. [ABSTRACT FROM AUTHOR]

European beech wood (Fagus sylvatica) is common hardwood in the Czech Republic and an important material in industry. However, the demand for this renewable material is not sufficient. In order to improve its utilization as a high value material, wood properties can be modified and new material can be developed. This paper is focussing on ammonia modification, which has been known for decades mainly for the plasticization effect, but commonly used only for wood darkening. The first part of this paper presents selected properties of ammonified and densified beech wood, called lignamon (mechanical properties, swelling and durability). The second part compares the plasticization effect of ammonia gas with the common method using hot saturated steam. The last part shows the influence of ammonia gas treatment on glued joint strength. Very good properties of lignamon were proved. It is a strong material with permanent compression even after 2 cycles of swelling in water and subsequent drying. Durability is significantly improved. Ammonia plasticization effect at 0.2MPa alone is low compared to hot steam. The best results were achieved by the methods combined. It was found that ammonia treatment can improve strength of glued joint in the case of beech veneers. [ABSTRACT FROM AUTHOR]

Densification techniques, combined with other treatment processes, helping additionally to improve wood properties, play an important role in wood modification. An innovative example of this combination with other techniques is the viscoelastic thermal compression (VTC) process. In this study, material of poplar wood from fast growing short rotation plantation (SRP), modified by VTC process, was used for investigation and results were compared with non-modified native wood of plantation grown poplar. Selected physical and mechanical properties, i.e., density, equilibrium moisture content (EMC), and modulus of elasticity (MOE) were investigated. The material, used for this investigation, was obtained from plantation grown poplar clone Max-4 (Populus nigra x Populus maximowiczii) from the Czech Republic. Results show that compression and heat treatment of the viscoelastic thermal compression process lead to significant changes in physical and mechanical properties of the treated material. The density of material depends on the degree of densification and has a crucial effect on properties. The goal of this study was to examine the improvement of properties of SRP poplar clone after applying the VTC densification process. Property improvement of plantation grown poplar wood has a huge potential for future use of this low-cost and fast-growing material, which would save high value materials for special uses. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental research performed with native hornbeam and Robinia stem - and branch wood of forest origin as well as property - modified wood from poplar of forest and plantation origin. Results show higher density and strength properties of different branch assortments, enabling native wood material application in special higher utilization demands. In the case of lower stem wood properties of forest or fast-growing plantation poplar (low density, strength, moisture related behaviour, durability), quality improvement due to wood impregnation shows amazing modified new properties, making possible utilizations even under highe rmoisture conditions or strength as well as hardness demands. First applications in flooring material or moist-room equipment have been tested or are under development. Especially the application of thermal-treatment, combined with wood compression or the use of renewable impregnation agents from regrowing plant materials (liquids with higher content of phenolic compounds from pyrolysisthermal treatment or hydro-thermal carbonisation processes) enhancec the possibility of eco-friendly methods of wood modification or wood impregnation. [ABSTRACT FROM AUTHOR]

Gaseous ammonia treatment in combination with densification of wood has been known since several decades, but nowadays there is no industrial production of thus modified material; also little research is published in this area of wood science. Selected physical and mechanical properties, i.e., density profile, bending strength, hardness and equilibrium moisture content were investigated for Lignamon material, which was obtained from Czech industrial production. Densitometry showed a large variability of the density profile. It is due to the position of the sample in the original block and is affected by the loading of the sample in tests (direction orthogonal or parallel to compressing). Strength properties, hardness and moisture exclusion efficiency of Lignamon are enhanced. Further investigation will be carried out with self-produced samples. [ABSTRACT FROM AUTHOR]

The paper presents the results of a German - Czech - Hungarian - Slovenian wood research consortium, dealing with wood modification techniques by using renewable modification agents for the outdoor use of local, originally non-durable modified wood species like beech, poplar and pine sapwood. Higher value assortments of naturally durable and dimensional stable wood species, like oak and black locust from European forests, or others from tropical/sub-tropical forests are limited and partly criticized due to their non-sustainable production and harvesting conditions. Other reasons are the usage of non-local wood sources or the biocide treatment of non-durable species which have a higher impact on the environment because of long distance transport and the use of environmental critical chemicals. Due to simultaneously limited raw material volumes from fossil origin and their negative impact on climate and environment, the production and application of sustainable and renewable materials, like wood or further biomass assortments, become more and more important. Not only the sustainable production and use of the CO2-fixing material WOOD itself, but also the production and utilization of renewable liquid agents for the impregnation stage in the wood modification process-chain as well as the finishing or gluing process-steps are additionally helpful to improve the sustainability of the industrial production. The results show, that extracts from plant or tree residues with natural biocide or cross-linking behaviour as well as heat-treatment process residues of biomass materials, like collected liquids from thermal modification processes or hydro-thermal carbonised as well as pyrolysed or liquefied biomass or wood residues can result in a distinct improvement on the wood properties. These enhanced wood qualities enable the outdoor use of originally non-durable or non-dimensionally stable wood assortments. [ABSTRACT FROM AUTHOR]