Thermal modification of soft [deciduous] wood
2008
Biziks, V., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Andersons, B., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Irbe, I., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Chirkova, J., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Grininsh, J., Latvian State Inst. of Wood Chemistry, Riga (Latvia)
Studies of the physical and chemical properties of soft deciduous wood, namely, grey alder (Alnus incana) in thermal modification (temperature 140-180 deg C, water vapour medium) are carried out. Changes in the wood mass, density, dimensions, chemical composition, cell wall pore structure, water vapour sorption properties and durability in dependence on treatment temperature are characterised. The maximum mass losses are at 180 deg C (up to 15%). With an increase in temperature, the relative amounts of cellulose and especially lignin grow. The changes in the wood components by FTIR spectroscopy were analysed. With increasing treatment temperature, as a result of the less ordered carbohydrates (hemicelluloses) degradation. With increasing hydro-thermal modification treatment temperature the effect of wood degrading rots fungi (C.puteana and C.versicolor) to gray alder specimens' decreases. The condensates formed in the treatment process and the compounds leached with water from modified wood were analysed. The condensates contain mainly acids and tannins. With increasing modification temperature, the amount of acetic acid and furfural in the condensate are grows. Acids, esters, sugars and tannins are leached with water from modified wood. The maximum amounts of esters and sugars are leached from the wood modified at 160 deg C. After treatment at 180 deg C, they decrease, obviously, thermally degrade and transfer in the condensate.
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