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Rozměrová stabilizace lisovaných dřevěných dílců
Karásek, Lukáš
This diploma thesis deals with wood plasticization using microwave (MW) radiation for wood densification purposes. In this work, the literary sources of the investigated issue were summarized. The experiment was carried out on test samples of white poplar (Populus alba) with dimensions of 190 x 40 x 30 mm. Microwave plasticization was carried out by passing through a microwave laboratory line at a power of 1.5 kW and a conveyor speed of 0.1 m/min. After plasticization, the test samples were compacted in compression molds by a press by 50%. The compacted test samples were stabilized in compression molds at a temperature of 103°C for 7 days. Using heat modification at 180°C and 200°C improved moisture resistance and reduced swelling. The samples were subjected to density profile analysis to evaluate the plasticization quality.
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Stanovení koeficientů tepelné vodivosti modifikovaného dřeva buku
Stárek, Šimon
The bachelor thesis is dedicated to the influence of selected wood modifications on its thermal properties. For the experimental part of the work, European beech wood (Fagus sylvatica L.) was used, which was modified by acetylation (using acetic anhydride) and thermal modification at temperatures of 200 and 220 ˚C. Values of thermal conductivity coefficient, specific heat capacity, and thermal diffusivity were measured using the Thermophysical Tester RTB device. The obtained data were statistically evaluated and compared with available literature. Compared to control samples, a decrease in thermal conductivity of approximately 3 % was observed in samples thermally modified at 200 ˚C. Samples thermally modified at 220 ˚C showed much significant decrease in thermal conductivity, that being over 15 %, due to a more pronounced decrease in the density of the modified wood. Despite the fact that the density of acetylated samples increased, very similar results were achieved. This decrease in thermal conductivity was mainly caused by the different thermal properties of the chemical used for impregnation process. Modified wood with these thermal properties can find applications in the construction industry, where the priority is to achieve the best possible energy efficiency of components made of wood.
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Vliv tepelné a chemické modifikace na sorpční, difuzní a hygroexpazní vlastnosti dřeva
Imramovský, Pavel
This thesis dealed with the influence of heat and chemical modification on sorption, diffusion and hygroexpansion properties of wood. To this aim, a thermal modification of European beechwood was carried out at temperatures (180 °C, 200 °C, 220 °C) in the special modified chamber of Katres. Furthermore, chemical modification was required on individual samples using acetic acid anhydride. The individual samples had to be sliced in radial and tangential directions using microtoma. A dynamic vapour sorption (DVS) device was used to determine the sorption and diffuse properties of all these beech slices as well as the reference unmodified sample. In addition, dynamic swelling was determined for all groups studied in radial and tangential directions. In order to determine the rate of swelling, sample sizes were measured using a scaler in specified directions before and after the 24-hour period in the water. The results indicated that both heat- and chemically-treated beechwood scored better against moisture than reference untreated samples. The diffusion coefficient in the radial direction was also higher than in the tangential direction, which corresponds to the professional literature. The results indicate that heat- and chemically-treated beechwood resisted better moisture than the reference untreated samples. Within swelling, direction plays a large role, as measurements in the tangential direction are nearly twice as high as the radial. The possibilities of using modified wood in construction as well as from the perspective of the researched characteristic were considered. The statistics were performed in the ANOVA program.
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Vliv tepelné modifikace na vybrané vlastnosti dřeva plantážově pěstovaného topolu
Horníček, Stanislav
The thesis deals with analyses of thermal modification process and assessment of the possibilities of using plantation grown polar wood clone MAX-4 (Populus Nigra and Populus maximowitzii) with modified properties in wooden products. Part of present thesis is to provide general state of art about recently developed thermal modification processes, research dealing with plantation grown wood species cultivation and its material properties, i. e. fast growing poplar hybrids mainly. Furthermore, assessment of possible use of thermally modified material for wooden products based on experimental results of physical and mechanical properties. The aim of present thesis is to evaluate material properties of thermally modified fast growing poplar clone. Improvemetns within material properties of plantation grown poplar wood has a huge potential for future use of this low-cost, low durable and fast-grown wood and therefore increase its utilization within products made of wood.
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Vliv modifikace na pevnost lepení buku
Šmíd, Pavel
This diploma thesis is focused on the influence of thermal modification on the strength of bonded joint in tension according to ČSN EN 205. For the purpose of this work was used beech wood. The thermal modification of the test samples was performed at temperatures of 160 °C, 180 °C and 200 °C. The selected bond strength adhesives were melamine-urea formaldehyde adhesives (MUF), phenol-resorcinol formaldehyde adhesives (PRF) and one-component polyurethane adhesives (PUR). In addition to the thermal modification the effect of plasma modification on bond strength is also determined. The test lamellas were plasma treated (DCSBD) prior to gluing and pressing. The result is the determination of the tensile strength of the bonded joint in all the above-mentioned modifications and comparation of the results.
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Vliv doby a teploty paření na pružnostní a pevnostní charakteristiky dřeva buku
Jakeš, Ondřej
This diploma thesis primarily focuses on thermal modification of wood with superheated steam and its effect on elasticity and strength. The sample tested was 200 pcs of bending samples and 200 pcs compressive samples of European beech. These samples were divided into ten groups. One group was referential and the remaining nine groups were modified using different temperatures and during different time intervals. The main goal was to determine density, modulus of elasticity and rupture and to discover their dependence on the chosen mode of modification. The next part contains the analysis of the effect of thermal modification with superheated steam on the acoustic properties and the colour of wood. In the last part, the mass loss and the change in equilibrium moisture content was analysed in relation to the modification mode.
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Vliv tepelné modifikace na vybrané vlastnosti dřeva plantážově pěstovaného topolu
Horníček, Stanislav
The thesis deals with analyses of thermal modification process and assessment of the possibilities of using plantation grown polar wood clone MAX-4 (Populus Nigra and Populus maximowitzii) with modified properties in wooden products. Part of present thesis is to provide general state of art about recently developed thermal modification processes, research dealing with plantation grown wood species cultivation and its material properties, i. e. fast growing poplar hybrids mainly. Furthermore, assessment of possible use of thermally modified material for wooden products based on experimental results of physical and mechanical properties. The aim of present thesis is to evaluate material properties of thermally modified fast growing poplar clone. Improvemetns within material properties of plantation grown poplar wood has a huge potential for future use of this low-cost, low durable and fast-grown wood and therefore increase its utilization within products made of wood.
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Vliv tepelné modifikace na vybrané vlastnosti bukového dřeva tlakově impregnovaného přírodními oleji
Daněk, Václav
Present study aims to analyze thermal modification of beech wood (Fagus sylvatica L.) press-impregnated by natural oil and its influence on physical and mechanical properties of wood. Beech wood was press-impregnated by hemp oil (O 1000) and thermally modified at 200°C for 3 hours. Influence of certain treatment (i.e. oil impregnation, thermal modification, combination) was experimentally investigated using physical and mechanical tests. Color changes (CIELab system), dimensional stability and bending strength were experimentally measured and results compared with reference group. Results of given work was further discussed and compared with literature. Results shows increase of dimensional stability about 18% after thermal modification (TM) and 22% for oil impregnated and thermally modified wood (OL+TM). Mechanical performance (bending strength) decreased about 5,2% after thermal modification as a results of degradation of wood cell wall. On the other hand, strength increase about 9% for wood impregnated by oils. Combined processed provide results within similar range as reference. Results should be further discussed and parameters of process (temperature levels) as well as influence of various oils parameters (drying, semi-drying, nondrying) tested in future.
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Evaluation of Impact Strength and Bending Strength of Thermally Modified Beech Wood with the False Heartwood
Vykoukal, Jakub ; Zeidler, Aleš (advisor) ; Procházka, Jiří (referee)
This bachelor thesis examines the influence of thermal modification on beech wood, with taking into account the difference of properties of healthy samples and samples with false heartwood. Thermal modification took place in two stages (165 ° C and 210 ° C), which are together with the untreated set tried on impact strength, bending strength (static modulus of elasticity) and the dynamic modulus of elasticity. The additional measured properties were density, equilibrium moisture and change of color spectrum. The first level of treatment slightly increased the bending strength and the static modulus of elasticity, residue tests, however, showed a negative effect on the other measured properties of the heat treated samples. It has been shown also that false heartwood has a clearly negative effect on the measured mechanical properties.
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