Influence of Thermal Treatment on the Hygroscopicity and Dimensional Stability of Oak Wood
AbstractThe influence of thermal treatment on moisture exchange between wood and natural environment with variable air parameters as well as on dimensional stability of wood samples was investigated. The experiments were carried out with oak wood samples indoors and outside. The thickness of samples was 30 mm, width was 30 mm and length was 20 mm; conventional density varied from 500 kg/m3 to 580 kg/m3. Initially, the wood was air-dried down to 7 %–9 % of moisture content. In order to decrease possibility of the both moisture absorption and evaporation during wood application thermal treatment must be applied. Due to that the samples were heated at temperature of 60, 80, 100 and 120ºC for 24, 48, 72 and 96 hours. The moisture content of wood and its variations after thermal treatment depends on the both heating temperature and duration. The higher temperature and the longer heating duration, the lower wood hygroscopicity can be achieved. The effect of thermal treatment on the moisture content and its changes were observed for wood samples stored indoor and outside. In dependence of thermal treatment conditions moisture content in wood samples independently on storing conditions (indoor or outside) can decrease down to 30 % compare to the untreated ones. The change of moisture content during various seasons after 24 hours of storing indoor decreases down to 60 %, while outside that is only 39 %. Dimensional stability of wood samples also depends on the both thermal treatment temperature and duration. The higher treatment temperature and the longer duration, the higher dimensional stability can be obtained. The heat treatment of oak wood samples at selected regimes allows to decrease values of shrinkage and swelling coefficients down to 40 %.
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