Thermal modification is a method in which heating wood in the absence of oxygen improves its properties and extends its durability. Changes in the structure of the cell wall due to thermal degradation significantly affect the properties of the wood. For my diploma work, American red oak was chosen for the investigaton, which we exposed to different temperatures: 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, and 220 °C. Using thermogravimetric analysis, we analysed the thermally modified samples in the temperature range between 25 °C and 600 °C under a nitrogen flow. The results of the analysis enabled the creation of calibration curves for different temperature ranges, showing the mass loss during the thermogravimetric measurement in relation to the mass loss during thermal modification. These curves are useful to determe the degree of thermal modification of unknown samples. The highest correlation was obtianed in the temperature range between 130°C and 290°C. We also measured the contact angle of water droplet on all thermally modified American red oak samples. The water droplet contact angle increased with the temperature of thermal modification up to 190°C, where it reached its maximum value, and then started to decrease.
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