scholarly journals Degradation of thermo-hygro-mechanically (THM)-densified wood by soft-rot fungi

Holzforschung ◽  
2008 ◽  
Vol 62 (3) ◽  
Author(s):  
Oleksandr Skyba ◽  
Peter Niemz ◽  
Francis W.M.R. Schwarze
Keyword(s):  
Lignin Content ◽  
Beech Wood ◽  
Treated Wood ◽  
Untreated Wood ◽  
Soft Rot ◽  
Saturated Steam ◽  
Densified Wood ◽  
Microscopical Examination ◽  
Weight Losses ◽  
Spruce Wood

Abstract Thermo-hygro-mechanical (THM)-densified wood is more resistant to colonisation and degradation by brown-rot fungi than untreated wood. Colonisation and degradation by soft-rot fungi was investigated in treated Norway spruce (Picea abies) and treated beech (Fagus sylvatica) to assess their suitability for utility class 4. Three different treatments were applied: thermal-hygro (TH) treatment, mechanical densification and THM-treatment including densification and post-treatment under saturated steam conditions at different temperatures. For comparison, additional wood specimens were treated with two concentrations of a chromium-copper (CC) wood preservative. After 32 weeks incubation, weight losses induced by soft-rot fungi were lowest in wood treated with CC. Highest weight losses were recorded from TH-treated wood, in which soft-rot erosion attack (type 2) was exclusively observed in spruce. In comparison to controls, significantly lower weight losses by soft-rot fungi were recorded in THM-treated spruce wood, but no such differences were found in beech wood. Microscopical examination showed that in THM-treated wood of spruce, soft-rot type 1 commenced from the outer wood surfaces and cavity formation was not found in deeper regions of the wood samples. THM-treated beech wood was more susceptible to degradation than that of spruce which can be partly explained by the higher syringyl lignin content in beech wood, which is more susceptible to all kinds of degradation. Hyphal colonisation and soft-rot was facilitated within deeper regions of beech wood mainly in the non-occluded lumina of parenchyma cells in multiseriate xylem rays. It can be concluded that TH-treated spruce wood and THM-treated beech wood is susceptible to soft-rot and therefore inappropriate for utility class 4.

scholarly journals Resistance of thermo-hygro-mechanically densified wood to colonisation and degradation by brown-rot fungi

Holzforschung ◽  
2005 ◽  
Vol 59 (3) ◽  
pp. 358-363 ◽  
Author(s):  
Francis W.M.R. Schwarze ◽  
Melanie Spycher
Keyword(s):  
Large Diameter ◽  
Treated Wood ◽  
Brown Rot ◽  
Hyphal Growth ◽  
Saturated Steam ◽  
Densified Wood ◽  
Brown Rot Fungi ◽  
Weight Losses ◽  
Poria Placenta ◽  
Different Temperatures

Abstract Colonisation and wood degradation by three brown-rot fungi, Coniophora puteana, Gloeophyllum trabeum and Poria placenta, were studied in wood of Norway spruce (Picea abies) subjected to three different treatments: hygro-thermal (TH) (160 and 180°C), mechanical densification and thermo-hygro-mechanical (THM) treatment including densification and post-treatment under saturated steam conditions at different temperatures (140, 160 and 180°C). The weight loss induced by all three fungi was lowest in THM-densified wood post-treated at 180°C. Highest weight losses were recorded for controls and TH-treated wood. Fungal colonisation varied in its intensity, depending on the treatment applied to the wood. Hyphal growth in controls and TH-treated wood was abundant, whereas in densified and THM-densified wood it was sparse and confined predominantly to the cell lumina of earlywood tracheids. Also, penetration of large-diameter hyphae and associated degradation in THM-densified wood was impeded by occlusion of the lumina, associated with irreversible compression (loss in shape memory). In contrast to C. puteana and P. placenta, which showed typical brown-rot behaviour, G. trabeum frequently showed hyphal tunnelling within the secondary walls of tracheids and xylem ray parenchyma of controls and thermally treated wood. Such growth was never observed in THM-densified wood post-treated at 180°C.

scholarly journals Resistance of thermo-hygro-mechanically (THM) densified wood to degradation by white rot fungi

Holzforschung ◽  
2009 ◽  
Vol 63 (5) ◽  
Author(s):  
Oleksandr Skyba ◽  
Peter Niemz ◽  
Francis W.M.R. Schwarze
Keyword(s):  
Norway Spruce ◽  
Cell Walls ◽  
Treated Wood ◽  
White Rot Fungi ◽  
Hyphal Growth ◽  
White Rot ◽  
Densified Wood ◽  
Weight Losses ◽  
Spruce Wood ◽  
Different Temperatures

AbstractColonisation and degradation by the white rot fungi,Trametes versicolorandT. pubescens, were studied in wood of Norway spruce and beech subjected to three different treatments: (1) hygro-thermal treatment (160°C and 180°C), (2) mechanical densification, and (3) thermo-hygro-mechanical (THM) treatment including densification and post-treatment at different temperatures (140°C, 160°C and 180°C). The weight losses induced by the fungi were lowest in THM-densified woods. However, volume related numerical indicators for decay susceptibility did not show any significant improvements of THM-densified woods against both fungi. Analysis of the chemical composition of treated wood species revealed slight alterations in the content of polysaccharides and lignin. White rot fungi circumvented conditions restricting hyphal growth within the occluded tracheid lumina by hyphal tunnelling in the secondary walls of fibre tracheids in beech or by forming bore holes that transversally penetrated cell walls of earlywood tracheids in THM-densified spruce. The studies indicate that THM-densified beech and Norway spruce wood may have some potential in utility class 3 but are inappropriate for use in utility class 4.

scholarly journals Treatment of wood with atmospheric plasma discharge: study of the treatment process, dynamic wettability and interactions with a waterborne coating

Holzforschung ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jure Žigon ◽  
Matjaž Pavlič ◽  
Pierre Kibleur ◽  
Jan Van den Bulcke ◽  
Marko Petrič ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Treatment Process ◽  
Beech Wood ◽  
Treated Wood ◽  
Plasma Discharge ◽  
Contact Angles ◽  
Atmospheric Plasma ◽  
Waterborne Coating ◽  
Spruce Wood ◽  
The Impact

AbstractPlasma treatment is becoming a mature technique for modification of surfaces of various materials, including wood. A better insight in the treatment process and the impact of the plasma on properties of wood bulk are still needed. The study was performed on Norway spruce and common beech wood, as well as their thermally modified variations. The formations of the airborne discharge, as well as mass changes of the treated wood, were monitored. The impact of such treatment on wood-coating interaction was investigated by evaluating the dynamic wettability and penetration into wood. At the wood surface, plasma streamers were observed more intense on denser latewood regions. Wood mass loss was higher with increasing number of passes through the plasma discharge and was lower for thermally modified wood than for unmodified wood. Plasma treatment increased the surface free energy of all wood species and lowered the contact angles of a waterborne coating, these together indicating enhanced wettability after treatment. Finally, the distribution and penetration depth of the coating were studied with X-ray microtomography. It was found that the coating penetrated deeper into beech than into spruce wood. However, the treatment with plasma increased the penetration of the coating only into spruce wood.

scholarly journals Calorific Power Improvement of Wood by Heat Treatment and Its Relation to Chemical Composition

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5322
Author(s):  
Idalina Domingos ◽  
Umit Ayata ◽  
José Ferreira ◽  
Luisa Cruz-Lopes ◽  
Ali Sen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Chemical Composition ◽  
Lignin Content ◽  
Treated Wood ◽  
Untreated Wood ◽  
High Heating Value ◽  
Heat Treated ◽  
Positive Linear Correlation ◽  
Total Extractives ◽  
Calorific Power

Chemical composition influences the calorific power of wood, mainly due to the calorific power of structural compounds and extractives. Heat treatment changes the chemical composition of treated wood. This work studies the relationship between chemical composition and calorific power improvement by heat treatment. Samples were heat-treated by the ThermoWood process ® for 1 h and 2 h. High heating value (HHV) and chemical composition; lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol, and water were determined. The HHV of untreated wood ranged between 18.54–19.92 MJ/kg and increased with heat treatment for all the tested species. A positive linear correlation was found between HHV and Klason lignin (R2 = 0.60). A negative trend was observed for holocellulose, cellulose, and hemicelluloses content against HHV, but with low determination coefficients for linear regression. The best adjust for polysaccharides was found for hemicelluloses content. A positive correlation could be found for dichloromethane extractives (R2 = 0.04). The same was obtained in relation to ethanol extractives with R2 = 0.20. For water and total extractives, no clear positive or negative trends could be achieved. The results showed that the HHV of wood increased with heat treatment and that this increase was mainly due to the increase in lignin content.

Extractive composition and summative chemical analysis of thermally treated eucalypt wood

Holzforschung ◽  
2008 ◽  
Vol 62 (3) ◽  
Author(s):  
Bruno Esteves ◽  
José Graça ◽  
Helena Pereira
Keyword(s):  
Treated Wood ◽  
Untreated Wood ◽  
Syringic Acid ◽  
Saturated Steam ◽  
Extractive Content ◽  
Treatment Conditions ◽  
Mass Spectometry ◽  
Almost All ◽  
New Compounds ◽  
Thermally Treated

Abstract Eucalypt wood (Eucalyptus globulus) was heated in an oven for 2–24 h at 170–200°C and in an autoclave with superheated and saturated steam for 2–12 h at 190–210°C. The chemical composition of untreated wood and thermally treated wood with different mass losses in the range of 1.1–11.9% was studied by summative analysis, and the composition of dichloromethane, ethanol and water extracts was determined by gas chromatography mass spectometry (GC-MS). The hemicelluloses degraded first, mainly regarding the arabinose and xylose moieties. Lignin degraded at a slower rate and cellulose was only slightly affected under severe treatment conditions. The extractive content increased first with heat treatment and decreased later on. Almost all of the original extractives disappeared and new compounds were formed, such as anhydrosugars, mannosan, galactosan, levoglucosan and two C5 anhydrosugars. The most prominent lignin derived compounds were syringaldehyde, syringic acid and sinapaldehyde. The main difference between autoclave and oven treated samples was the appearance of more oxidized extractives for the oven treatment.

scholarly journals Coating Performance on Exterior Oil-Heat Treated Wood

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 225 ◽  
Author(s):  
Mojgan Nejad ◽  
Mahdi Dadbin ◽  
Paul Cooper
Keyword(s):  
Moisture Content ◽  
Wood Species ◽  
Color Change ◽  
Treated Wood ◽  
Untreated Wood ◽  
Average Moisture Content ◽  
Southern Pine ◽  
Coating Performance ◽  
Spruce Wood ◽  
Heat Treated

Thermal modification and the degree of improved properties from the treatment depend on wood species and treatment parameters. Southern yellow pine and spruce are two wood species commonly used for decking, fences, and siding in North America. This study evaluated coating performance when applied on oil-heat-treated Southern pine and spruce wood samples. Moisture content, color, and gloss changes of samples were analyzed before weathering and then after each month for the first three months and then every six months during 18 months of natural weathering exposure in Toronto, Canada. The results showed that coated heat-treated woods had lower moisture uptake, lower color change, and overall better appearance ranking than coated-untreated wood samples. Coated-spruce wood samples had lower checking and splitting, and in general, much better performance than coated-Southern pine treated samples. Notably, the average moisture content of treated spruce wood samples was significantly lower than that of Southern pine, which explains lower checking and improved coatings’ appearance.

Biomechanical pulping of spruce wood chips with Streptomyces cyaneus CECT 3335 and handsheet characterization

Holzforschung ◽  
2005 ◽  
Vol 59 (2) ◽  
pp. 173-177 ◽  
Author(s):  
Manuel Hernández ◽  
M. Jesus Hernández-Coronado ◽  
M. Isabel Pérez ◽  
Esteban Revilla ◽  
Juan C. Villar ◽  
...  
Keyword(s):  
Lignin Content ◽  
Middle Lamella ◽  
Treated Wood ◽  
Strength Properties ◽  
Wood Chips ◽  
Fiber Network ◽  
Spruce Wood ◽  
Gradual Loss ◽  
Acid Soluble Lignin ◽  
Streptomyces Cyaneus

AbstractThe actinobacteriumStreptomyces cyaneusCECT 3335 was evaluated for its ability to delignify spruce wood chips (Picea abies) after 2 weeks of incubation prior to refiner mechanical pulping. Weight loss of the chips during the treatment ranged from 2% to 3%. Chemicalanalysis of the treated wood showed an increase in acid-soluble lignin content concomitant with a notable increase in the acid/aldehyde+ketone [AC/(AL+KE)] ratio of the lignin compared with the control. Structural alterations in wood cell walls were observed by optical and scanning microscopy using astra blue-safranin staining and cryosections stained with gold/palladium, respectively. A gradual loss of lignin from the lumen towards the middle lamella and incipient defiberization could be observed. The estimation of specific energy for the defibration and refining stages of treated pulp showed a 24% reduction in the energy required, largely due to a 30% saving in the defibration of chips. The analysis of handsheets obtained from treated pulp showed a notable improvement in some strength properties, such as breaking length, tear index and stretch. In addition, the high Gurley air resistance value indicates more packing of the voids of the fiber network. These results demonstrate for the first time the suitability ofStreptomyces cyaneusfor biomechanical pulping purposes.

scholarly journals Effects of Fiber Angle on the Tensile Properties of Partially Delignified and Densified Wood

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5405
Author(s):  
Matthias Jakob ◽  
Jakob Gaugeler ◽  
Wolfgang Gindl-Altmutter
Keyword(s):  
Tensile Strength ◽  
Tensile Properties ◽  
Mechanical Performance ◽  
Treated Wood ◽  
Untreated Wood ◽  
Mechanical Anisotropy ◽  
Densified Wood ◽  
Wood Fibers ◽  
Transverse Tensile ◽  
Transverse Tensile Strength

Partial delignification and densification provide a pathway to significant improvement in the mechanical performance of wood. In order to elucidate potential effects of this treatment on the mechanical anisotropy of wood, partially delignified and densified spruce wood veneers were characterized at varying degrees of off-axis alignment. While the tensile strength and the modulus of elasticity (MOE) were clearly improved in parallel to the axis of wood fibers, this improvement quickly leveled off at misalignment angles ≥30°. For transverse tensile strength, the performance of alkaline-treated and densified wood was even inferior to that of untreated wood. Microscopic examination revealed the presence of microscopic cracks in treated wood, which are assumed to be responsible for this observation. It is concluded that impaired transverse tensile properties are a weakness of partially delignified and densified wood and should be considered when a potential usage in load-bearing applications is intended.

scholarly journals Air permeability and sound absorption coefficient changes from ultrasonic treatment in a cross section of Malas (Homalium foetidum)

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Chun-Won Kang ◽  
Eun-Suk Jang ◽  
Nam-Ho Lee ◽  
Sang-Sik Jang ◽  
Min Lee
Keyword(s):  
Absorption Coefficient ◽  
Ultrasonic Treatment ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Treated Wood ◽  
Untreated Wood ◽  
Sound Absorption Coefficient ◽  
Permeability Constant ◽  
Average Value ◽  
Permeability Increase

AbstractWe investigated the effect of ultrasonic treatment on Malas (Homalium foetidum) gas permeability and sound absorption coefficient using the transfer function method. Results showed a longitudinal average Darcy permeability constant of 2.02 (standard deviation SD 0.72) for untreated wood and 6.15 (SD 3.07) for ultrasound-treated wood, a permeability increase of 3.04 times. We also determined the average sound absorption coefficients in the range of 50 to 6.4 kHz and NRC (noise reduction coefficient: average value of sound absorption coefficient value at 250, 500, 1000, and 2000 Hz) of untreated Malas. Those values were 0.23 (SD 0.02) and 0.13 (SD 0.01), respectively, while those of ultrasonic-treated Malas were 0.28 (SD 0.02) and 0.14 (SD 0.02), a 19.74% increase in average sound absorption coefficient.

Growth behavior of wood-destroying fungi in chemically modified wood: wood degradation and translocation of nitrogen compounds

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lukas Emmerich ◽  
Maja Bleckmann ◽  
Sarah Strohbusch ◽  
Christian Brischke ◽  
Susanne Bollmus ◽  
...  
Keyword(s):  
Protective Action ◽  
Treated Wood ◽  
Untreated Wood ◽  
Brown Rot ◽  
Decay Resistance ◽  
White Rot ◽  
Decay Fungi ◽  
Chemically Modified ◽  
Decay Tests ◽  
Modified Wood

Abstract Chemical wood modification has been used to modify wood and improve its decay resistance. However, the mode of protective action is still not fully understood. Occasionally, outdoor products made from chemically modified timber (CMT) show internal decay while their outer shell remains intact. Hence, it was hypothesized that wood decay fungi may grow through CMT without losing their capability to degrade non-modified wood. This study aimed at developing a laboratory test set-up to investigate (1) whether decay fungi grow through CMT and (2) retain their ability to degrade non-modified wood. Acetylated and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) treated wood were used in decay tests with modified ‘mantle specimens’ and untreated ‘core dowels’. It became evident that white rot (Trametes versicolor), brown rot (Coniophora puteana) and soft rot fungi can grow through CMT without losing their ability to degrade untreated wood. Consequently, full volume impregnation of wood with the modifying agent is required to achieve complete protection of wooden products. In decay tests with DMDHEU treated specimens, significant amounts of apparently non-fixated DMDHEU were translocated from modified mantle specimens to untreated wood cores. A diffusion-driven transport of nitrogen and DMDHEU seemed to be responsible for mass translocation during decay testing.

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