Time-Course Changes of Chemical and Physical Properties in Sugi (<i>Cryptomeria Japonica</i> D. Don) Logs During Smoke Heating
Keywords:Sugi, smoke heating
AbstractKiln-drying of sugi (Japanese cedar, Cryptomeria japonica D. Don) wood is a very difficult process. This is because the moisture content (MC) of the green log is very high and varies considerably between heartwood and sapwood. To investigate the time-course changes of chemical and physical properties during smoke heating, sugi green logs were smoke-heated with different treatment times at a temperature inside the log of 80°C using a modified food smoker. After smoke heating, the amounts of chemical components and some physical properties, such as MC, relative degree of crystallinity (RDC), equilibrium moisture content (EMC), and bending strength, were examined. The distribution of MC within the log became uniform after smoke heating for 60 h. Almost no differences in the amounts of chemical components were recognized between the control and smoke-heated woods. The relative degree of crystallinity increased with smoke heating for 40 h, corresponding to the decrease in EMC. The modulus of elasticity (MOE) in static bending increased with smoke heating, whereas the modulus of rupture and the absorbed energy in impact bending did not change significantly. The increase in MOE was considered to be due to the increase in RDC. The results obtained here indicated that no significant thermal degradation of wood occurred by smoke heating for 60 h at a temperature inside the log of 80°C. However, smoke heating affected the physical properties, such as RDC, EMC, and MOE.
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