Abstract:

This paper focuses on the response of main wood mechanical properties of the Cunninghamia lanceolata plantation wood treated in hot air and hot vegetable oil respectively for different processing temperatures and times， so the MOR（modulus of rupture）， MOE（modulus of elasticity）， compression strength parallel to grain and hardness of wood were studied， also， the differences of main chemical components of heat treated samples were analyzed， and the cross section of treated samples were observed by scanning electron microscope to acquire information on changes of heat treated wood internal structure. The results showed that the MOR， MOE， compression strength parallel to grain and hardness of wood had different responses to different heat treatment process， the MOR， MOE， compression strength parallel to grain of samples which was treated in hot oil or hot air all had a decreasing trend compared to reference samples， and their difference vary much when processing temperature was increased and times was lengthened during the heat treatment， in comparison with processing times，the processing temperatures showed remarkable effects. When samples were heated for 1，3 and 5 h at a temperature of 180 ℃ in air or oil， the changes of MOR and MOE were both within the scope of 3% and compression strength parallel to grain of samples decreased by 3.29%～9.58% and 3.89%～7.18% respectively， there were obvious differences in the compression strength parallel to grain but no obvious ones in the MOR and MOE， while samples were treated at 200 ℃ or above for 1，3 and 5 h， they all were significantly lower than those of the control， however， the differences were significant. The results of hardness showed that both of the hardness in the tangential direction and in the radial direction of treated samples tended to increase when the heating treatment time from 1 to 5 h at the temperature of 180 ℃， when samples were treated at 200 ℃ for 3 h， the hardness were the highest， while samples were treated at 200 ℃ for 5 h or above 200 ℃， the hardness tended to decrease， the hardness of samples treated at 220 ℃ for 5 h were significantly lower than those of the control. In addition， the effect of heat medium on the main wood mechanical properties of treated samples were significant， the variations of the main wood mechanical properties of the samples when the treatment of hot oil appeared to be slightly lower than that of samples when the treatment of hot air under the same condition. The differences in main chemical components and the cross section of samples in responses to the different processing condition reflected the response difference of main wood mechanical properties in Chinese Fir plantation.

Key words: Chinese Fir plantation, heat treatment, mechanical properties, heat medium, response