Heat-treatment with the vacuum-press dewatering method: chemical properties of the manufactured wood and the condensation water

Hofmann, Thilo; Wetzig, Melanie; Rétfalvi, Tamás; Sieverts, Tom; Bergemann, Holger; Niemz, Peter

doi:10.1007/s00107-012-0657-0

Cited by 26 publications

(10 citation statements)

References 13 publications

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“…The soak treatments in H 2 O cause a small dry mass loss (ML), which is further increased by soaking in DMSO and subsequent washing with H 2 O. The progressively swollen wood matrix promotes the release of trapped degradation products that cannot evaporate under dry-HT process conditions, consistent with other studies (Hofmann et al 2013;Wentzel et al 2018).…”

Section: Resultssupporting

confidence: 87%

A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification

Willems¹,

Altgen

Rautkari

2019

Holzforschung

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Heat treatment (HT) is a well-known means to reduce the equilibrium wood moisture content (EMC) at a specified relative humidity (RH). EMC is profoundly decreased by the loss of accessible hydroxyl groups (OH acc ) in the wood matrix by thermochemical reactions. However, the obtained EMC reduction after HT can be partly reversible, depending on the ability of the wood matrix polymers to fully mechanically relax during HT. We discuss the results of our earlier experimental study on the OH acc content and the associated EMC decrease at 93% RH by a relaxation inhibiting dry-HT vs. a relaxation enabling wet-HT. New experimental results, showing that OH acc does not significantly change during reversible EMC changes, are added to the discussion. This study quantitatively supports a molecular explanation of the reversible EMC, in which wood moisture is principally bound at sorption sites, composed of two functional groups, constituting a hydrogen-donor/acceptor pair, involving at least one OH acc group. The irreversible part of EMC reduction is assigned to the thermochemical removal of OH acc from the wood matrix. The reversible part is attributed to a process of wood polymer conformal rearrangements, bringing an isolated OH acc group in proximity of another free hydrogen-bonding functional group, creating a site for water sorption.

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Section: Resultssupporting

confidence: 87%

A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification

Willems¹,

Altgen

Rautkari

2019

Holzforschung

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“…e low-intensity treatment resulted in higher acidity than a treatment at higher temperatures (212°C and 3 hours) which might be due to further release of organic acids as volatile organic compounds out of the kiln at higher temperature or due to the possible reaction of organic acids with the cell wall components. Hofman et al [30] reported a diverse range of the pH, depending on the wood species and intensity of heat treatment. For oak wood (Quercus robur L.) pH increased with intensifying the treatment, while for beech wood (Fagus sylvatica L.) and ash wood (Fraxinus versicolor L.) pH decreased between untreated and medium levels.…”

Section: Heat-treated Wood As a Substrate For Coatingsmentioning

confidence: 99%

Heat-Treated Wood as a Substrate for Coatings, Weathering of Heat-Treated Wood, and Coating Performance on Heat-Treated Wood

Jirouš-Rajković

Miklečić

2019

Advances in Materials Science and Engineering

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Heat treatment is a method of wood modification with increasing market acceptance in Europe. The major patented European commercial heat treatment processes have trade names ThermoWood, Platowood, Retiwood, Le Bois Perdure, and Oil-Heat-Treated Wood (OHT). To what extent modification of wood affects the resistance of wood to weathering is also an important aspect for wood applications, especially where appearance is important. Unfortunately, heat-treated wood has poor resistance to weathering, and surface treatment with coatings is required for both protection and aesthetic reasons. As a substrate for coating, heat-treated wood has altered characteristics such as lower hygroscopicity and liquid water uptake and changed acidity, wettability, surface free energy, and anatomical microstructure. Various wood species, heat treatment method, treatment intensity, and treatment conditions exhibited a different extent of changes in wood properties. These altered properties could affect coating performance on heat-treated wood. The reported changes in acidity and in surface energy due to heat treatments are inconsistent with one another depending on wood species and temperature of the treatments. This paper gives an overview of the research results with regards to properties of heat-treated wood that can affect coating performance and weathering of uncoated and coated heat-treated wood.

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“…A lot of different wood thermal modification methods are known which vary with the treatment atmosphere, temperature, and duration (Hofmann et al, 2013;Militz & Altgen, 2014;Gerardin, 2016). They all include exposure of wood to elevated temperature (150 -260 °C) in absence of oxygen which result in complex reactions including certain destruction of low-molecular substances and hemicelluloses, reorganisation of lignin and cellulose and evaporation of volatile compounds (Sandberd, Haller, & Navi, 2013).…”

Section: Introductionmentioning

confidence: 99%

Effect of thermal treatment on physical and mechanical properties of birch and pine wood

Antons¹,

Cīrule²,

Verovkins³

et al. 2018

Research for Rural Development

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No simple method has yet been found for satisfactory wood bio-resistance improvement regarding material performance in its end-use. An attempt to obtain material with proper strength and bio-durability by combined wood thermal modification and impregnation with a biocide is being researched. To select the most appropriate treatment conditions for the combined process, changes in wood physical and mechanical properties depending on the treatment temperature were investigated in the present study. For the investigation, in Latvia the most widespread woodsoftwood pine (Pinus sylvestris L.) and hardwood birch (Betula spp.) was used. Changes of wood mechanical and physical properties due to thermal modification were investigated and effect of treatment temperature and relative humidity on wood characteristics evaluated. It was found that, due to different degree of changes, no identical treatment conditions suit for birch and pine wood. Birch wood is considerably more sensitive to temperature and acceptable strength was maintained only for birch wood treated at 150 °C and for pine wood treated at 160 °C. Nevertheless at higher environmental humidity equilibrium moisture content and consequently radial and tangential swelling increased for all studied wood types, substantially smaller changes due to elevated humidity were detected for modified wood.

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Heat-treatment with the vacuum-press dewatering method: chemical properties of the manufactured wood and the condensation water

Cited by 26 publications

References 13 publications

A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification

A molecular model for reversible and irreversible hygroscopicity changes by thermal wood modification

Heat-Treated Wood as a Substrate for Coatings, Weathering of Heat-Treated Wood, and Coating Performance on Heat-Treated Wood

Effect of thermal treatment on physical and mechanical properties of birch and pine wood

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