scholarly journals Quality Control of Thermally Modified Timber Using Dynamic Vapor Sorption (DVS) Analysis

Forests ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 666
Author(s):  
Miha Humar ◽  
Rožle Repič ◽  
Davor Kržišnik ◽  
Boštjan Lesar ◽  
Romana Cerc Korošec ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Quality Control ◽  
Moisture Content ◽  
Mass Loss ◽  
Thermal Modification ◽  
Wood Moisture Content ◽  
Vapor Sorption ◽  
Dynamic Vapor Sorption ◽  
Wood Moisture ◽  
Factor C

The importance of thermal modification is increasing worldwide. Increased use of thermally modified timber (TMT) has resulted in a need for reliable quality control, comprising control of variation of the production within defined limits, allowing third-party control in the case of certification and the regulation of customer complaints and claims. Techniques are thus needed to characterise the modification of quality in terms of improved target properties of TMT during industrial production, and of TMT products that have been in service for an arbitrary time. In this study, we aimed to utilise dynamic vapor sorption (DVS) for this purpose. Norway spruce (Picea abies) and European beech (Fagus sylvatica) samples were thermally modified at different temperatures according to different heat treatment techniques: (1) the Silvapro process based on an initial vacuum; (2) an air heat treatment, whereby samples were wrapped in aluminium foil; (3) thermal modification of wood samples in the ambient atmosphere in a laboratory oven. Wood samples from closed processes were analysed for validation. TMT was characterised with respect to mass loss, colour and density. Mass loss of wood due to modification (MLTM) was correlated with factors derived from DVS analysis. The present DVS measurements suggest that the equilibrium wood moisture content (EMC95% RH), the time to reach 10% wood moisture content (t10% MC), and the elongation factor, c, derived from a logarithmic function, can serve as alternative parameters to characterise the quality of several thermal modification processes. Further studies are recommended using other wood species, different modification processes and further parameters gained from DVS measurements to understand the robustness and the predictive power of the applied technique.

Observations on the biology of Lycts Brunneus (Steph.)

1953 ◽  
Vol 1 (1) ◽  
pp. 102 ◽  
Author(s):  
FJ Gay
Keyword(s):  
Heat Treatment ◽  
Life Cycle ◽  
Relative Humidity ◽  
Sex Ratio ◽  
Moisture Content ◽  
Incubation Period ◽  
Developmental Period ◽  
Wood Moisture Content ◽  
Optimal Conditions ◽  
Wood Moisture

An account is given of certain aspects of the biology of Lyctus brunneus (Steph.). Female beetles are able to oviposit within 24 hr. after emerging from infested timber and deposit an average of more than 70 eggs per female over a period of 1-2 weeks. Eggs are deposited at depths of 1.0-6.5 mm. in the wood vessels, preferentially from a transverse surface, but also through radial and tangential faces. The incubation period of the eggs ranges from about 1 week at 26�C, to 3 weeks at 15�C. The egg-adult developmental period ranges from 4 months at 26�C. to 16 months or more at 15�C. Under optimal conditions of temperature, relative humidity (and hence wood moisture content), and nutrition, the life cycle may be as short as 2 months. The sex ratio of L. brunneus is 1 : 1 and the adult beetles live from 2.5 to 7 weeks, depending upon the temperature, females being somewhat longer-lived than males. The larvae of L. brunneus are somewhat more resistant to heat treatment than are the eggs, but one 1/2hr. exposure to 50�C. is completely lethal to both stages.

scholarly journals Effects of Wood Moisture Content and the Level of Acetylation on Brown Rot Decay

Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 299 ◽  
Author(s):  
Samuel L. Zelinka ◽  
Grant T. Kirker ◽  
Amy B. Bishell ◽  
Samuel V. Glass
Keyword(s):  
Moisture Content ◽  
Mass Loss ◽  
Linear Trend ◽  
Fungal Growth ◽  
Weight Percent Gain ◽  
Brown Rot ◽  
Weight Percent ◽  
Wood Moisture Content ◽  
Wood Moisture ◽  
Brown Rot Decay

Acetylation is one of the most common types of wood modification and is commercially available throughout the world. Many studies have shown that acetylated wood is decay resistant at high levels of acetylation. Despite its widespread use, the mechanism by which acetylation prevents decay is still not fully understood. It is well known that at a given water activity, acetylation reduces the equilibrium moisture content of the wood cell wall. Furthermore, linear relationships have been found between the acetylation weight percent gain (WPG), wood moisture content, and the amount of mass loss in decay tests. This paper examines the relationships between wood moisture content and fungal growth in wood, with various levels of acetylation, by modifying the soil moisture content of standard soil block tests. The goal of the research is to determine if the reduction in fungal decay of acetylated wood is solely due to the reduction in moisture content or if there are additional antifungal effects of this chemical treatment. While a linear trend was observed between moisture content and mass loss caused by decay, it was not possible to separate out the effect of acetylation from fungal moisture generation. The data show significant deviations from previously proposed models for fungal moisture generation and suggest that these models cannot account for active moisture transport by the fungus. The study helps to advance our understanding of the role of moisture in the brown rot decay of modified wood.

A thermal modification technique combining bulk densification and heat treatment for poplar wood with low moisture content

2021 ◽  
Vol 291 ◽  
pp. 123395
Author(s):  
Xianju Wang ◽  
Dengyun Tu ◽  
Chuanfu Chen ◽  
Qiaofang Zhou ◽  
Huixian Huang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Moisture Content ◽  
Thermal Modification ◽  
Poplar Wood ◽  
Modification Technique

scholarly journals Moisture-Dependent Strength Properties of Thermally-Modified Fraxinus excelsior Wood in Compression

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1647 ◽  
Author(s):  
Edward Roszyk ◽  
Elżbieta Stachowska ◽  
Jerzy Majka ◽  
Przemysław Mania ◽  
Magdalena Broda
Keyword(s):  
Moisture Content ◽  
Strength Properties ◽  
Treatment Temperature ◽  
Thermal Modification ◽  
Fraxinus Excelsior ◽  
Mechanical Parameters ◽  
Saturation Point ◽  
Wood Moisture ◽  
Intrinsic Anisotropy ◽  
European Ash

European ash (Fraxinus excelsior L.) is one of the species commonly used for wood thermal modification that improves its performance. The presented research aimed to investigate a moisture-dependent strength anisotropy of thermally-modified European ash in compression. Wood samples were modified at 180 °C and 200 °C. Their mechanical parameters were determined in the principal anatomical directions under dry (moisture content of 3%) and wet (moisture content above fibre saturation point) conditions. Effect of heat treatment temperature and moisture content on the ash wood mechanical parameters concerning each anatomical direction were determined. The results show that thermal treatment kept the intrinsic anisotropy of wood mechanical properties. It decreased wood hygroscopicity, which resulted in improved strength and elasticity measured for wet wood when compared to untreated and treated samples. Higher treatment temperature (200 °C) increased wood elasticity in compression in all the anatomical directions despite wood moisture content during the measurements. Multivariate analysis revealed that the modification temperature significantly affected the modulus of elasticity perpendicular to the grain, while in the case of compression strength, the statistically significant effect was observed only parallel to the grain. The results obtained can be useful from an industrial perspective and can serve as part of a database for further modelling purposes.

scholarly journals Thermal conductivity and deformation of Taxodium hybrid ‘Zhongshanshan’ during heat transfer process

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2645-2655
Author(s):  
Yuehua Zhu ◽  
Yaoli Zhang ◽  
Biao Pan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Moisture Content ◽  
Transfer Process ◽  
Dimensional Change ◽  
Testing Temperature ◽  
Scientific Basis ◽  
Heat Transfer Process ◽  
Wood Moisture Content ◽  
Wood Moisture

The thermal conductivity and the deformation of wood from the Taxodium hybrid ‘Zhongshanshan’ were studied in the process of heat transfer. The results showed that the average thermal conductivity of this wood was 0.1257 W/(m·K) under the condition of 12% wood moisture content and 30 °C heat transfer temperature. When the testing temperature exceeded 0 °C, the thermal conductivity increased linearly with both temperature and wood moisture content and was affected by the moisture content of the wood. During the heat transfer process, the deformation of features caused repeated swelling and shrinkage in the longitudinal, radial, and tangential directions. The dimensional change was greatly affected by the wood’s moisture content and was less affected by the temperature. These results are of great meaning for the study of the heat transfer process of Taxodium hybrid ‘Zhongshanshan’ wood. Furthermore, it provides a scientific basis for the heat preservation effect, drying treatment, and pyrolysis treatment of Taxodium hybrid ‘Zhongshanshan’ wood for use as a building material.

scholarly journals Improving the accuracy of wood moisture content estimation in four European softwoods from Spain

2021 ◽  
Vol 30 (1) ◽  
pp. e002
Author(s):  
Juan I. Fernández-Golfín ◽  
Maria Conde Garcia ◽  
Marta Conde Garcia
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Electrical Resistance ◽  
Solid Wood ◽  
Wood Products ◽  
Wood Moisture Content ◽  
Accurate Estimation ◽  
Wood Moisture ◽  
Mathematical Functions ◽  
Measured Moisture Content

Aim of study: To obtain improved models to predict, with an error of less than ± 2.0%, the gravimetric moisture content in four different softwoods commonly present in the Spanish and European markets, based on electrical resistance measurements. This improved moisture content estimation is useful not only for assessing the quality of wood products, especially in the case of laminated products, during the transformation and delivery process, but also for accurately monitoring the evolution of moisture in wood present in bridges and buildings, which is of great importance for its maintenance and service life improvement.Area of study: The study was carried out on samples of Scots, laricio, radiata and  maritime pines of Spanish provenances.Material and methods: On 50x50x20 mm3 solid wood samples (36 per species, 9 per condition), conditioned at 20ºC (±05ºC) and 40±5%, 65±5%, 80±5% or 90±5% Relative Humidity (RH), electrical resistance and oven-dry moisture content was measured. The Samuelsson's model was fitted to data to explain the relationship between the two variables. The accuracy of the model was evaluated by the use of an external sample.Main results: With the proposed mathematical functions the wood moisture content can be estimated with an error of ±0.9% in the four species, confirming the effectiveness of this nondestructive methodology for accurate estimation and monitoring of moisture content.Research highlights: our results allow the improvement of the moisture content estimation technique by resistance-type methodologies.Keywords: Resistance-type moisture meter; species correction.Abbreviations used: MC: Moisture content; RH: relative Humidity; R: electrical resistance; RP: wood electrical resistance measured parallel to the grain; RT: electrical resistance measured perpendicular (transversally) to the grain; GM-MC: gravimetrically measured moisture content.

scholarly journals Monitoring of Beech Glued Laminated Timber and Delamination Resistance of Beech Finger-Joints in Varying Ambient Climates

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1672
Author(s):  
Hannes Stolze ◽  
Mathias Schuh ◽  
Sebastian Kegel ◽  
Connor Fürkötter-Ziegenbein ◽  
Christian Brischke ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Wood Moisture Content ◽  
Adhesive Systems ◽  
Wood Moisture ◽  
Near Surface ◽  
Finger Joints ◽  
Glued Laminated Timber ◽  
Delamination Resistance ◽  
Normative Requirements

In this study, varying ambient climates were simulated in a test building by changing temperature and relative humidity. Beech glued laminated timber (glulam, Fagus sylvatica, L.) was freshly installed in the test building and monitoring of the change in wood moisture content of the glulam resulting from the variations in climate was carried out. Subsequently, finger-jointed beech specimens were exposed to the variations in relative humidity measured in the course of the monitoring experiment on a laboratory scale, and thus an alternating climate regime was derived from the conditions in the test building. Its influence on the delamination of the finger-joints was evaluated. In addition, it was examined whether beech finger-joints using commercial adhesive systems fulfil the normative requirements for delamination resistance according to EN 301 (2018) and whether different bonding-wood moisture levels have an effect on the delamination of the finger-joints. In the context of the monitoring experiment, there was a clear moisture gradient in the beech glulam between the inner and near-surface wood. The applied adhesive systems showed almost the same delamination resistance after variation of relative humidity. The normative requirements were met by all PRF-bonded and by most PUR-bonded beech finger-joints with higher bonding wood moisture content.

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