Study Of The Effect Of Steam Hydro-Thermal Treatment On The Properties Of Poplar

The thesis investigated the steam hydro-thermal treatment of fast-growing poplar. By orthogonal experiment we studied the effect of the three main parameters, the initial moisture content, treating duration and steam temperature, on the wood color, main physical and mechanical properties. The results are as below:1. The steam temperature is the main factor influencing wood color; the lightness index L* decreases with the increase of steam temperature and treating duration; the red-green index a*, the yellow-blue index b* and the total color difference△E* increase with the increase of steam temperature and treating duration; while b* decreases with the increase of the initial moisture content; the treated wood is darker, more yellow, more red and saturated.2. The air-dry density decreases with the increase of the initial moisture content, treating duration and steam temperature; EMC and volume shrinkage efficiency increase with the decrease of initial moisture content, while decrease with the increase of the treating duration and steam temperature; steam temperature and initial moisture content have significant effect on the equilibrium moisture content and volume shrinkage respectively;3. The compression strength parallel to the grain and MOR decrease with the increase of treating duration and steam temperature; the MOE decreases with the decrease of initial moisture content ,while slightly increase with the increase of the treating duration and steam temperature; the initial moisture , treating duration and steam temperature have no significant effect on the compression strength parallel to the grain, modulus of rupture(MOR) and modulus of elasticity(MOE);4. Initial moisture content 8%, treating duration 30min, and steam temperature 160℃is the optimism treating condition; the wood of the optimism experiment has a color difference of 27.69NBS with the untreated wood, and 6.86NBS with teak; the air-dry density, EMC and volume shrinkage all showed a decrease symbolizing an increase of the dimensional stability; while the antiswelling efficency is worse than untreated; the compression strength parallel to the grain, the MOR decrease while the MOE show a slight increase; the trachied, fiber, ray and pits all changed in some way .5. The lightfastness of the treated wood is much better than untreated; the lightness decreases slowly with exposure time; the red-green index increases in the former stage and decreases in the latter one, become stable after 60h; the yellow-green index decreases slowly in 24h, and become stable thereafter; the color difference gradually increases in 24h, and then slightly decreases; No apparent color difference is shown.6. The FTIR analysis shows the content of the chemical ingredient is changed, the content of the cellulose and the hemicelluloses is less, and the content of the lignin is more; the change in the structure and content of the wood ingredient is the inner reason for the changes of wood color, physical and mechanical properties.