Improvement of durability of alder wood by hydrothermal modification | Alkšņa koksnes ilgizturības uzlabošanas iespējas hidrotermiskās modifikācijas ceļā
2009
Andersone, I., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Andersons, B., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Cirkova, J., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Biziks, V., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Irbe, I., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Kurnosova, N., Latvian State Inst. of Wood Chemistry, Riga (Latvia) | Grinins, J., Latvian State Inst. of Wood Chemistry, Riga (Latvia)
The aim of the work was to develop a modification method for improving the durability properties of hardwood, especially alder wood, so that to expand its applicability, partially replacing the most valuable softwood. A study of the information on the advantages and drawbacks of modification methods from the environment and technological aspects as well as the product quality and expenditures points of view, hydrothermal modification has been chosen as the most suitable one in Latvia's conditions. The task of the study was to optimise the modification treatment conditions, reaching a compromise between the improvement of the biodurability properties and mechanical strength losses. The results of laboratory biodurability tests performed on white (Coriolus versicolor) and brown (Coniophora puteana, Poria placenta) rot fungi testify that, after the treatment at 160 deg C/1 h, the wood becomes medium-durable against rot fungi (durability class 3), but that modified at 189 deg C/1 h become very durable (class 1). In this case, these properties are retained also after washing with water; respectively, their long-term durability under the action of atmospheric precipitation can be forecasted. Thermal action changes the wood strength properties. The obtained results make it possible to conclude that, in the hydrothermal modification of alder at the temperature 160-180 deg C, a decorative material with an improved biodurability against rot and stain fungi as well as lower moisture absorption is obtained. The treatment in such conditions decreases the bending strength by ~ 30%.
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