Abstract
Abstract The wood-water interactions of modified beech wood (Fagus sylvatica L.) were studied. Specimens were thermally modified at 180 (TM1), 200 (TM2) and 220 °C (TM3), acetylated (Acet), and melamine formaldehyde (MF) resin (Mel) modified. Afterwards, the water vapour characteristics, i.e. water vapour sorption isotherms, equilibrium moisture content (EMC), dimensional stability of specimens conditioned at 30, 65 and 90% RH and liquid water characteristics, i.e. water absorption, maximum moisture content (MC), leachability and swelling kinetics, were determined and the results compared with reference (Ref) specimens. From the results, it is evident that the scale of wood-water interactions was highly dependent on the thermal modification temperature and type of chemical modification. The water vapour isotherms of thermally modified wood decreased, whereas more severe treatment exhibited more distinct reduction. The EMC values of the Mel and TM1 specimens decreased only at high RH, whereas the most significant decrease, within the whole range of observation, was found in the Acet group. The maximum MC reduction was achieved by acetylation. As a consequence of swelling reduction, dimensional stability expressed as anti-swelling efficiency (ASE) was considerably improved. A relatively high initial linear-phase swelling rate was found for the Ref specimens, whereas modified wood exhibited comparatively slow and gradual swelling.
Highlights
Wood is an important natural and renewable resource, which has many technical advantages, such as its mechanical strength and stiffness in relation to its weight, processing energy and aesthetic properties
After conditioning at 95% relative humidities (RHs), the equilibrium moisture content (EMC) of melamine formaldehyde (MF) resinmodified specimens decreased to 20.8%, which represents a 6.7% reduction
The water vapour and liquid water related characteristics of beech wood treated by thermal modification, acetylation and MF resin impregnation were significantly improved
Summary
Wood is an important natural and renewable resource, which has many technical advantages, such as its mechanical strength and stiffness in relation to its weight, processing energy and aesthetic properties. Despite these unquestionably positive benefits, wood exhibits some disadvantageous properties, such as dimensional instability and susceptibility to fungal decay, which are both strongly influenced by the absorption and desorption of water from and to the surroundings. Water absorption generally results in a decrease in strength and leads to dimensional changes until the wood reaches the fibre saturation point (FSP). The first two types of treatment will be studied and discussed, i.e. thermal modification and two chemical treatments: acetylation using acetic anhydride and modification using melamine formaldehyde (MF) resin
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