Browsing by Subject "wood modification"

Wood as construction material has many great properties, although some challenges exist too, such as durability towards certain biological factors, and other factors like moisture. Wood modification allows us to fight against these problems and increases the number of uses of wood. Thermal modification is already widely used, and it is known that thermally modified wood absorbs less water than unmodified wood. European beech (Fagus sylvatica L.) belongs among the most common tree species in Central Europe, and it has a lot of potential what comes to possible uses. In the future the role of beech in wood industry may become more important, as there is higher need for new materials and products. Because of this, it is important to find ways to make it more applicable for use. The aim of this study was to find out how dimensional stability of European beech can be increased by thermal modification once it is modified in different temperatures. European beech (Fagus sylvatica L.) wood was from trees harvested in Brno, Czech Republic (49.29534, 16.75125). Timber was kiln dried and specimens were prepared (20 × 60 × 300-400 mm). Specimens were thermally modified in three different temperatures (180°C, 200°C, 220°C) for three hours by using a small-scale (0.75m3) laboratory chamber with superheated steam environment and atmospheric pressure. After thermal modification samples with dimension of 20 × 20 × 20 mm were cut (5-10 of each group plus reference). First, samples from each temperature group and reference group were oven-dried, sized and weighted at dry state. Next, ten samples from each group were soaked in water at room temperature (20°C) for 16 days and their weights were measured. Afterwards equilibrium moisture content (EMC) was determined for each temperature treatment, and values were compared to reference. Furthermore, these samples were conditioned at relative humidity (RH) of 30%, 65% and 90%. EMC was calculated in each RH and the radial (R), and tangential (T) swelling (SW) and anti-swelling efficiency (ASE) was also calculated. Later, other five samples from each group were soaked for 24 hours in the water at room temperature (20°C) and its radial and tangential dimensions were continuously recorded. Afterwards, the radial and tangential swelling and anti-swelling efficiency (ASE) were calculated for them. Moisture related stability characteristic of thermally modified European beech were studied. Results showed that when beech is modified at higher temperatures, its dimensional stability increases. Once beech was thermally modified, its swelling and equilibrium moisture content (EMC) decreased. Changes in the EMC took place fastest right after the exposure of wood to moisture. Swelling of the wood was higher in tangential than in radial direction. Changes in longitudinal direction were not studied. In the future more studies could be done, as it is important to gain more knowledge about the topic. For example, more studies about the sorption behaviour of beech wood could be studied by using dynamic vapour sorption equipment (DSV). Comparison between other softwood and hardwood species could be done, so as comparison with beech from same origin of seeds growing in different areas in Europe. Also, knowledge about the issues the higher modification temperature might cause for the wood when used in constructions or in products should be studied, so as the techno-economic factors related to chosen modification temperature.