The following hardwood species were used for heat treatment: birch (Betula pendula) and grey alder (Alnus incana). Modification was carried out in a multi-functional pilot device WTT in elevated water vapour pressure conditions at five different treatment regimes: 140/1; 160/1; 160/3; 170/1 and 180/1 (temperature,˚C/duration, h).
To estimate the properties of hydrothermally modified (HTM) wood, to optimize heat treatment process and to assure a constant product quality with lower treatment costs, optimized treatment parameters is necessary to develop. In the hydrothermal modification (HTM) process, not only the chemical properties and structure of wood are changed, but also mechanical strength, physical and water uptake properties. Dimensional instability is considered as one of disadvantages of wood, when it is used as building and construction material. Therefore, improving dimensional stability and water-repellency of wood is an important approach to obtain long-term service life of wood exposed at high humidity conditions indoor or outdoor.
The aim of this study was to optimize process of WTT thermal treatment of hardwood species to create a novel material for outdoor or high humidity weathered application in industrial scale. For this purpose, the influence of various process parameters of the pilot scale one stage heat treatment process on water related properties of HTM hardwoods were investigated.
Hardwoods were used to study the changes in the equilibrium moisture content (EMC) and anti-swelling efficiency (ASE) after one stage heat treatment process. Non-treated control specimens were used for comparison. The equilibrium moisture content and swelling in radial and tangential direction of treated wood was reduced compared to the untreated wood, indicating as reduction of the hygroscopicity of wood.
Keywords: hardwood, hydrothermal modification, water
Authors
Grinins J.
Latvian State Institute of Wood Chemistry, Riga, Latvia
Biziks V.
Latvian State Institute of Wood Chemistry, Riga, Latvia
Andersons B.
Latvian State Institute of Wood Chemistry, Riga, Latvia
Andersone I.
Latvian State Institute of Wood Chemistry, Riga, Latvia
Sansonetti E.
Latvian State Institute of Wood Chemistry, Riga, Latvia
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