| The research on structures, properties and heat treatment modifications of Styrax tonkinensis (Pierre) Craib ex Hartw. wood (the main plantation species in Vietnam) is the mainly objective of thesis. The studies on using of water vapor as the protection gas during the wood heat treatment, the temperature from 170℃to 210℃and the time from 2hrs to 6hrs to deal with the heat treatment conditions, were also implemented in this thesis. The main results of the thesis are presented below:Styrax tonkinensis is diffuse porous to semi-diffuse porous wood, the uniform structure and fine. The mentioned Wood has the yellow-white color. Its equilibrium moisture content is 12.8%(at temprature (20±2)℃, relative humidity (65±3)%of standar condition), air-dry density (the moisture content of 12%) is 0.455/cm3, basic density is 0.388g/cm3, the oven-dried and air-dried shrinkage ratio of tangential to radial are respectively 2.4 and 2.047, the volumetric shrinkage coefficient is 0.367. The longitudinal compression strength, MOR, MOE and composite strength are respectively 40.55Mpa,77.033Mpa,76.938 (108MPa), 61.196 kJ/m3. According to the Vietnamese lumber grading, Styrax tonkinensis wood belongs to sixth grade, currently used only to do some handicrafts, pulp and paper, chopsticks, etc. and doesn't need a big strength of wood.The wood treatment makes the darker color for it. When the temperature and the time were increased, the heat-treated wood color will be changed from yellow-white to brown and puce color. This study also shows that the range of variance value ofΔC*,ΔE*,ΔH* are respectively 0.258～-14.207,17.807～52.28,3.120～6.059.The physical and the mechanical properties of heat treated wood are reduced, as reduction of equilibrium moisture content 7.61～4.96%; basic density, air-dry density reduces respectively 4.64%～11.16%,2.65%～10.54%; air dry volumetric shrinkage ratio, oven dry volumetric shrinkage ratio, volumetric shrinkage coefficients reduces respectively 5.74～2.19%,9.39～4.11%,6.81%～53.67%; air dry volumetric swelling ratio, water absorption volumetric swelling ratio reduces respectively 3.20～2.36%,12.61～6.09%; longitudinal compression strength, MOR, MOE, composite strength are respectively reduces respectively 6.03%～28.18%,0.93%～34.83%,2.88%～11.16%,20.55%～77.19%.During the heat treatment process, the water absorption ratio will decrease step by step when the temperature and the time increase. The water absorption ratio is 183.84% for controlled wood, and heat treatment conditions reduce respectively 179.06%,177.88%, 169.07% at 170℃in 2hrs,4hrs,6hrs; 164.63%,164.28%,160.82% at 190℃in 2hrs,4hrs, 6hrs; 159.97%,158.84%,149.33% at 210℃in 2hrs,4hrs,6hrs.The antiswelling efficiency of heat-treated wood is improved remarkably. At the heat treatment conditions respectively 170℃,190℃,210℃, the average values of them will be 16.87%,33.71%,55.56%.Heat treatment process changed the decay resistance of Styrax tonkinensis. The untreated wood and the heat-treated wood respectively belong weight loss ratio of 33.52% to weight loss ratio of 1.60% at 210℃,6hrs of heat treatment condition.The weight loss ratio of heat-treated soft rot wood is reduced 1.68%～31.92% percentage point. Soft rot changes pH of wood, the pH of soft rot wood was improved 0.10～22.43% percentage point with the increasing of soft rot wood weight loss. The soft rot changes wood structure, erosions channels and notches in the wall were formed directly beneath hyphae within the cell lumen. These channels were typically angular and the notches V-shape. |
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