| 1. |
- Adamopoulos, Stergios, et al.
(författare)
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Adhesive bonding of beech wood modified with a phenol formaldehyde compound
- 2012
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 70:6, s. 897-901
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Tidskriftsartikel (refereegranskat)abstract
- Untreated (controls) and phenol–formaldehyde (PF)-modified beech wood (10 and 25 % solid content) were glued with phenol resorcinol formaldehyde (PRF) and polyvinyl acetate (PVAc). Shear strength of PRF-bonded specimens was higher than that of PVAc-bonded ones under dry and wet conditions irrespective of the pre-treatment. Under dry conditions, only PVAc-bonded specimens exhibited reduction in shear strength due to PF-modification with 25 % PF concentration as compared to the controls. PF treated wood provided inferior bonding under wet conditions with the exception of 25 % PF concentration specimens glued with PRF adhesive. Modification with PF resulted in a decrease of adhesive penetration into the porous network of interconnected cells, especially at 25 % PF concentration.
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| 2. |
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| 3. |
- Altgen, Michel, et al.
(författare)
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Factors Influencing the Crack Formation in Thermally Modified Wood
- 2012
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Ingår i: The Sixth European Conference on Wood Modification. - : University of Ljubljana. - 9789616144353 ; , s. 149-158
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Konferensbidrag (refereegranskat)abstract
- Wood anatomical changes during a thermal modification process are likely to adverselyaffect the properties of the final product. Therefore, an anatomical investigation was performed on Scots pine and Norway spruce material coming from different steps of the regular production of ThermoWood. A macroscopic evaluation using an evaluation scale between 1 and 3 revealed typical drying defects in some of the kiln dried boards. Nevertheless, at least 50 % of the unmodified boards were defect free (CR = 1), while at least 90 % of the thermally modified boards were not defect free (CR = 2 and CR = 3), thus indicating that surface cracks become more frequent and severe after the modification process. However there was no evidence of an impact of the conditioning stage on the crack formation. Even though most of the surface cracks were removed by planing, microscopic analysis by means of light and scanning electron microscopy revealed that there might still be micro-defects within the ThermoWood. Such micro-defects were mainly associated with parenchyma or epithelial cells of the rays or the resin canals. Furthermore, longitudinal cracks within the tracheids were observed within the earlywood latewood interface or within the earlywood. During repeated drying and wetting cycles, the crack formation was higher for thermally modified wood than for unmodified, despite a lower water uptake and a better dimensional stability. After the third cycle, the average crack rating of thermally modified wood was at least twice as high as for the unmodified wood. It was concluded that this increase in the crack formation might be caused by the presence of micro-defects that potentially act as a starting point for more severe cracks during swelling and shrinkage.
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| 4. |
- Altgen, Michael, et al.
(författare)
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Wood defects during industrial-scale production of thermally modified Norway spruce and Scots pine
- 2017
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 12:1, s. 14-23
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Tidskriftsartikel (refereegranskat)abstract
- This research investigates wood defects, particularly the formation of surface cracks, during the production of thermally modified wood and its exposure to cyclic moisture changes. Boards of Norway spruce and Scots pine originating from different steps within the production of ThermoWood® were collected and wood defects were investigated at macroscopic and microscopic scale. Subsequently, the wood was exposed to capillary wetting cycles to record its sensitivity towards cracking. After the modification process, typical anatomical defects of conventional kiln-drying became more frequent and severe, with the magnitude being to some extent depending on the presence of defects in the raw material. At microscopic scale, damages to ray parenchyma and epithelial cells as well as longitudinal cracks within the cell walls of earlywood tracheids were evident in thermally modified wood. Despite a lower water uptake and higher dimensional stability, thermally modified wood was more sensitive to surface cracking during wetting cycles than unmodified wood, i.e. at the outside face of outer boards (near bark). For limiting surface cracking of thermally modified wood during service life, the use of high-quality raw material, the exposure of the inside face of the boards (near pith) and the application of a surface coating are considered beneficial.
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| 5. |
- Bastani, Alireza, et al.
(författare)
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Development of bonding strength of modified birch veneers during adhesive curing
- 2016
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Ingår i: Wood research. - 1336-4561. ; 61:2, s. 205-214
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the bonding strength development of furfurylated, N-methylolmelamine (NMM) modified and thermally treated birch veneers glued with hot curing phenolformaldehyde (PF) adhesive in different pressing (20, 160 s) and open assembly times (20 s, 10min). For testing, the automated bonding evaluation system ABES was used with 2 N.mm-2applied pressure at 130°C. The bonding strength of both modified and unmodified samplesincreased significantly by prolongation of the pressing time from 20 to 160 s in all cases andfor both open assembly times. A deviation was observed for the samples treated at 220°C andat 20 s open assembly time. With the exception of NMM modified veneers, bonding strengthdid not change significantly by increasing the assembly time in the case of 20 s pressing forboth modified and unmodified samples. At 160 s pressing time, extension of the assembly timedeveloped a better bonding for controls, NMM modified and thermally treated veneers at 180°C.The combination of 10 min assembly time and 160 s pressing time proved as the optimal bondingcondition for controls, NMM modified and thermally treated veneers at 180°C while the highestbonding strength was noted in 20 assembly time and 160 s pressing time for furfurylated veneers.In most of the cases modification affected negatively the bonding performance of the veneers, inparticular for furfurylated and NMM modified samples.
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| 6. |
- Bastani, Alireza, et al.
(författare)
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Effect of open assembly time and equilibrium moisture content on the penetration of polyurethane adhesive into thermally modified wood
- 2017
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Ingår i: The journal of adhesion. - : Taylor & Francis. - 0021-8464 .- 1563-518X .- 1545-5823. ; 93:7, s. 575-583
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Tidskriftsartikel (refereegranskat)abstract
- The effect of wood moisture content and open assembly time on penetration of polyurethane (PU) adhesive into thermally treated Scots pine (195 and 210°C) was investigated according to effective (EP) and maximum penetration (MP) measurements using fluorescence microscopy. For samples treated at 195°C, a higher EP was noted at 8.6% equilibrium moisture content (EMC) after both assembly times (15 and 30 min) while for samples treated at 210°C, increasing wood moisture content resulted in a significant decrease in EP at 12.5% EMC after 15 min assembly time. Extending open assembly time was found to increase the EP of PU adhesive only in the case of samples treated at 195°C and with 8.6% EMC. For samples treated at both treatment temperatures and after shorter open assembly time, the highest MP observed at moderate EMC levels of 8.6 and 8.2% and the lowest at the higher EMC levels of 13.2 and 12.5%.
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| 7. |
- Bastani, Alireza, et al.
(författare)
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Gross adhesive penetration in furfurylated, N-methylol melamine-modified and heat-treated wood examined by fluorescence microscopy
- 2015
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 73:5, s. 635-642
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the radial penetration of three conventional cold-set wood adhesives [emulsion polymer isocyanate (EPI), poly (vinyl acetate) (PVAc), one-component polyurethane (PU)] into various degrees of furfurylated and N-methylol melamine-modified (NMM) Scots pine, and heat-treated Scots pine and beech based on measurements of effective (EP) and maximum penetration (MP) from microscopic observations. EP of EPI adhesive decreased after modification with higher concentration of furfuryl alcohol while an improved penetration was recorded for PVAc into furfurylated wood. A deeper penetration was observed for all adhesives into wood treated with lower concentration of furfuryl alcohol. The EP of EPI and PU adhesives reduced after NMM treatment but it increased in the case of PVAc. In spite of reduction of EP of PU after NMM treatment, it represented a deeper penetration among all adhesives possibly due to its lower molecular weight. For Scots pine, increasing the treatment temperature improved EP of all adhesives while for beech, the EP of PU and PVAc increased largely in the case of samples treated at 195 °C. Visual analysis of fluorescence microscopy pictures provided more detailed information on modality of penetration. The results are useful for understanding the interaction among common adhesives and modified materials, and can be used in future research to explain the bonding behavior of modified wood.
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| 8. |
- Bastani, Alireza, et al.
(författare)
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Shear strength of furfurylated, N-methylol melamine and thermally modified wood bonded with three conventional adhesives
- 2017
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 12:4, s. 236-241
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Tidskriftsartikel (refereegranskat)abstract
- The shear strength of furfurylated, N-methylol melamine (NMM) and thermally modified wood bonded with emulsion polymer isocyanate, polyvinyl acetate (PVAc), and polyurethane (PU) adhesives was examined. Furfurylation and NMM modification of Scots pine had a significant negative effect on the bonding strength with all adhesives irrespective of the treatment intensity. The obtained low-shear strength values were related to the brittle nature of the wood after modifications rather to the failure of the bondline. PVAc showed a better bonding performance with both furfurylated and NMM modified wood while the combination of furfurylated wood and PU gave the highest reduction in bonding strength (47–51%). Shear strength also decreased significantly after thermal modification in both Scots pine (36–56%) and beech (34–48%) with all adhesives. With the exception of thermally modified beech samples bonded with PU, bondline was found to be the weakest link in thermally modified wood as it was revealed by the wood failure surfaces. Bondline thickness and effective penetration of adhesives did not relate to the shear strength of all modified wood materials. The lower shear strength of modified wood could be attributed to other factors, such as the reduced chemical bonding or mechanical interlocking of adhesives, and the reduced strength of brittle modified wood substrate.
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| 9. |
- Bastani, Alireza, et al.
(författare)
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Study of adhesive bondlines in modified wood with fluorescence microscopy and X-ray micro-computed tomography
- 2016
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Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier BV. - 0143-7496 .- 1879-0127. ; 68, s. 351-358
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Tidskriftsartikel (refereegranskat)abstract
- The quantitative penetration of three coldset wood adhesives [one-component polyurethane (PU), emulsion polymer isocyanate (EPI), poly (vinyl acetate) (PVAc)] under hydraulic pressure into different types of modified wood was studied using fluorescence microscopy and the results were compared to these of a previous study without pressure on adjacent wood samples. The effective penetration (EP) of PU was negatively affected by furfurlylation and NMM modification when pressure was applied. For PVAc, 30% NMM treatment and heat treatment of Scots pine and beech at 210 °C had a negative effect on its EP, but against this the EP of this adhesive increased after heat treatment of beech at 195 °C. In the case of furfurylation, the depth of penetration of all adhesives was less into wood treated with higher concentration of furfuryl alcohol. PU showed a much deeper penetration into NMM-modified and heat-treated wood than the other adhesives with the exception of heat-treated beech at 195 °C. Application of pressure led to rather different results as compared to the EP data when no pressure was applied. The three-dimensional (3D) visualisation of the penetration of PU adhesive into heat-treated Scots pine was also examined by X-ray micro-computed tomography (XµCT). The 3D flow pattern of PU adhesive into heat-treated Scots pine was clearly depicted by XµCT.
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| 10. |
- Bastani, Alireza, et al.
(författare)
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Water uptake and wetting behaviour of furfurylated, N-methylol melamine modified and heat-treated wood
- 2015
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 73:5, s. 627-634
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Tidskriftsartikel (refereegranskat)abstract
- This study reports on the water uptake (WU) and wetting properties of different modified wood materials; furfurylated and N-methylol melamine (NMM) modified Scots pine, and heat-treated (Vacu3 method) Scots pine and beech. All modifications caused a substantial reduction in WU in the longitudinal, tangential and radial directions both after short (24 h) and long contact times (168, 336 h) with a saturated sponge. The water uptake coefficient (w t ) was reduced by approximately 71–89 % in furfurylated wood, with the higher weight percent gain (WPG) providing a slightly greater reduction. The reduction in WU was not found to depend on the NMM solid content. The NMM treatment had the maximum effect on the reduction of tangential w t by 80–84 % and was much smaller in the longitudinal direction (31–68 %). The treatment temperature of 195 °C gave lower WU values than treatment at 210 °C, and the only exception was the radial direction of Scots pine. The longitudinal w t of heat-treated beech represented the highest reduction by 81–89 %, while radial w t was less affected in both species. Sessile drop apparent contact angles for water and diidomethane and corresponding surface energies on planed tangential and radial wood surfaces revealed an increased hydrophobicity and reduced polarity of modified wood. Furfurylated and NMM modified tangential surfaces had a higher increase of apparent contact angles than the radial surfaces but this was not observed in the case of heat treatment. Heat-treated wood showed reduced wetting of surfaces only with water. Apparent contact angles did neither differ with treatment temperature nor with the NMM resin load. The disperse component of surface energy was slightly increased by 20 % maximum in modified wood, while the polar components showed a dramatic decrease by −30 to −90 % with no major differences among treatments and intensities, and between surfaces. The results provide a better understanding of the hygroscopic behaviour of modified wood, which might be useful to predict its adhesion with various polymers such as glues, coatings and paints.
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| 11. |
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| 12. |
- Gellerich, Antje, et al.
(författare)
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Evaluation of fungal infestation and decay in a simulated use class 3 situation (block test) after some years of exposure
- 2012
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Ingår i: The 43rd Annual Meeting of IRG. - Stockholm.
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Konferensbidrag (refereegranskat)abstract
- The so named “block test” was designed as part of the assessment methodology for testing the behaviour of natural and modified wood used under use class 3 (EN 335-2) conditions. The test was developed to expose the wood close to the ground to an environment with high humidity and high biological activity, but not in soil contact. The present study describes the evaluation of fungal infestation and decay of untreated samples in different blocks depending on their exposure time, positioning within the block and wood species. After 4 years outside exposure samples showed visible signs of decay. The highest rate of decay was visible in the middle layers of the block. After 7 and 8 years outside exposure, samples of all layers were infested with a similar intensity of different types of decay. The results have shown that in the bottom layer close to ground the major type of decay is white rot as well as white rot in combination with soft rot. In contrast, samples from the middle layers and top layer were infested mainly by brown and white rot but also soft rot was observed. The test setup is according the definition of use classes a method for use class 3 applications because the samples are out of ground contact. But the infestation of samples in all layers by soft rot indicated that under use class 3 test conditions but with elevated moisture conditions soft rot attack can occur and should make part of a proper test design.
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| 13. |
- Ghavidel, Amir, et al.
(författare)
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Characterization of Archaeological European White Elm (Ulmus laevis P.) and Black Poplar(Populus nigra L.)
- 2020
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Ingår i: Forests. - : MDPI. - 1999-4907. ; 11:12, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- The present study aims at characterization of freshly-cut and archaeological European white elm and poplar. The archaeological elm sample was buried at a depth of 8–10 m inside of soil with age approximation of ~1800–2000 years old, and the archaeological poplar sample was apart of a boat in a freshwater lake or river with age estimation of ~1000–1200 years. Alteration in the chemical structure of the elm and poplar samples due to the ageing process were confirmed by X-ray photoelectron spectroscopy (XPS). Both archaeological wood (AW) samples illustrated considerably lower cellulose crystallinity than the fresh samples as determined by X-ray diffraction. The sorption behavior of AW and fresh wood (FW) samples were evaluated by means of dynamic vapor sorption (DVS) analysis. Results exhibited a higher equilibrium moisture content (EMC) and sorption hysteresis values in archaeological elm and poplar as compared with the fresh samples. Higher hydrophilicity of the AW samples than the FW ones is attributed to their higher amorphous structure. The extensive degradation of AW samples were also confirmed by scanning electron microscopy (SEM) micrographs.
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| 14. |
- Jiang, Wen, 1990-, et al.
(författare)
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Preparation of Polyurethane Adhesives from Crude and Purified Liquefied Wood Sawdust
- 2021
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Ingår i: Polymers. - Basel, Switzerland : MDPI. - 2073-4360. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Polyurethane (PU) adhesives were prepared with bio-polyols obtained via acid-catalyzedpolyhydric alcohol liquefaction of wood sawdust and polymeric diphenylmethane diisocyanate(pMDI). Two polyols, i.e., crude and purified liquefied wood (CLW and PLW), were obtained fromthe liquefaction process with a high yield of 99.7%. PU adhesives, namely CLWPU and PLWPU,were then prepared by reaction of CLW or PLW with pMDI at various isocyanate to hydroxyl group(NCO:OH) molar ratios of 0.5:1, 1:1, 1.5:1, and 2:1. The chemical structure and thermal behavior of thebio-polyols and the cured PU adhesives were analyzed by Fourier transform infrared spectroscopy(FTIR) and thermogravimetric analysis (TGA). Performance of the adhesives was evaluated by singlelap joint shear tests according to EN 302-1:2003, and by adhesive penetration. The highest shearstrength was found at the NCO:OH molar ratio of 1.5:1 as 4.82 ± 1.01 N/mm2 and 4.80 ± 0.49 N/mm2 for CLWPU and PLWPU, respectively. The chemical structure and thermal properties of the cured CLWPU and PLWPU adhesives were considerably influenced by the NCO:OH molar ratio.
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| 15. |
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| 16. |
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| 17. |
- Källbom, Susanna, et al.
(författare)
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Sorption and surface energy properties of thermally modified spruce wood components
- 2018
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Ingår i: Wood and Fiber Science. - : Society of Wood Science and Technology. - 0735-6161. ; 50:3, s. 346-357
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work is to study the water vapor sorption and surface energy properties of thermally modified wood (TMW) components, ie wood processing residuals in the form of sawdust. The thermal modification was performed on spruce wood components using a steam-pressurized laboratoryscale reactor at two different temperature (T) and relative humidity (RH) conditions, T = 150 degrees C and RH = 100% (TMW150), and T = 180 degrees C and RH = 46% (TMW180). A dynamic vapor sorption (DVS) technique was used to determine water vapor sorption isotherms of the samples for three adsorption-desorption cycles at varying RH between 0% and 95%. Inverse gas chromatography (IGC) was used to study the surface energy properties of the samples, including dispersive and polar characteristics. The DVS results showed that the EMC was reduced by 30-50% for the TMW samples compared with control samples of unmodified wood (UW) components. A lower reduction was, however, observed for the second and third adsorption cycles compared with that of the first cycle. Ratios between EMC of TMW and that of UW samples were lower for the TMW180 compared with the TMW150 samples, and an overall decrease in such EMC ratios was observed at higher RH for both TMW samples. The IGC results showed that the dispersive contribution to the surface energy was higher at lower surface coverages, ie representing the higher energy sites, for the TMW compared with the UW samples. In addition, an analysis of the acid-base properties indicated a higher KB than KA number, ie a higher basic than acidic contribution to the surface energy, for all the samples. A higher KB number was also observed for the TMW compared with the UW samples, suggested to relate to the presence of ether bonds from increased lignin and/or extractives content at the surface. The KB was lower for TMW180 compared with TMW150, as a result of higher modification temperature of the first, leading to cleavage of these ether bonds.
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| 18. |
- Mahnert, Karl-Christian, et al.
(författare)
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UV-microspectrophotometry : A method to prove wood-modification with MMF?
- 2014
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Ingår i: European Conference on Wood Modification 2014.
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Konferensbidrag (refereegranskat)abstract
- The modification of wood with methylolated melamine formaldehyde resin (MMF) belongs to the group of impregnation modifications. In the course of this study, Koto sapwood samples were impregnated with MMF-solutions in a full-cell vacuum-pressure process. The samples were cured at a maximum temperature of 120 ºC for 24 hours. To characterize the modification, the solution uptake (SU) and weight percent gain (WPG) of the samples were calculated. The fixation of the melamine as parameter for the degree of curing was examined by C/N analysis. Areal UV-microspectrophotometry (UMSP)-scans of ultra-thin transverse sections of an untreated control and MMFmodified samples at 240 nm were recorded. Additionally, photometric point measurements with a spot size of 1 μm2 in the range 230 nm and 350 nm were conducted. UMSP was proven as suitable technique for the quantitative analysis of MMF-modified wood.
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| 19. |
- Mahnert, K-C, et al.
(författare)
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UV-microspectrophotometry : A method to prove wood modification with MMF?
- 2015
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Ingår i: International Wood Products Journal. - : Maney Publishing. - 2042-6445 .- 2042-6453. ; 6:1, s. 27-30
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Tidskriftsartikel (refereegranskat)abstract
- The modification of wood with methylolated melamine formaldehyde resin belongs to the group of impregnation modifications. In the course of this study, Koto sapwood samples were impregnated with methylolated melamine formaldehyde resin solutions in a full cell vacuum pressure process. The samples were cured at a maximum temperature of 120°C for 24 h. To characterise the modification, the solution uptake and weight percent gain of the samples were calculated. The fixation of the melamine as parameter for the degree of curing was examined by C/N analysis. Areal UV-microspectrophotometry scans of ultra-thin transverse sections of an untreated control and samples impregnated with methylolated melamine formaldehyde resin at 240 nm were recorded. Additionally, photometric point measurements with a spot size of 1 μm−2 in the range 230 and 350 nm were conducted. UV-microspectrophotometry was proven as suitable technique for the quantitative analysis of wood modified with methylolated melamine formaldehyde resin.
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| 20. |
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| 21. |
- Puttmann, Sabrina, et al.
(författare)
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Furfurylated wood for wooden window constructions
- 2010
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Ingår i: proceedings of The Fourth European Conference on Wood Modification. - : SP Technical Research Institute of Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 22. |
- Scholz, Gunthard, et al.
(författare)
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Migration of blue stain hyphae within wax treated wood
- 2011
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Ingår i: IAWA Journal. - : Brill. - 0928-1541 .- 2294-1932. ; 32:1, s. 88-96
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Tidskriftsartikel (refereegranskat)abstract
- The colonization of wax impregnated pine sapwood (Pinus sylvestris L.) and beech (Fagus sylvatica L.) by blue stain fungi and their hyphal migration within the treated wood was investigated. Neither the hydrophobation effect nor the physical presence of the congealed wax deposits could impede fungal growth on the surface. However, in contrast to the untreated controls, there was a lower occurrence of hyphae in wax-treated wood. Blue stain fungi grew mainly near the cross cut as well as in empty spaces such as micro-capillaries, parenchyma tissue or other wax free zones of treated wood.
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| 23. |
- Van Niekerk, Philip B., et al.
(författare)
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Mapping the biotic degradation hazard of wood in Europe - Biophysical background, engineering applications, and climate change-induced prospects
- 2022
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 76:2, s. 188-210
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Tidskriftsartikel (refereegranskat)abstract
- Construction using timber has seen a resurgence in light of global climate mitigation policies. Wood is a renewable resource, and engineered wood products are proving to be competitive against concrete and steel while having several advantages. However, while the renewable nature of wood in construction is a beneficial property for climate mitigation policies, the process of biodegradation introduces a challenge for service life planning. A review of hazard mapping is presented while developing contemporary hazard maps, occurrence maps and projected hazard maps for 2050 using representative concentration pathways (RCP) 2.6 and 8.5. The risk of timber decay is expected to increase in most of Europe as the temperatures rise, with a decrease expected in dryer regions. Termites are likely to experience a range expansion as more areas become suitable, while human activity and an increase in extreme weather events like floods are expected to facilitate dispersion. Marine borer species already present a risk in most European coastal regions; however, the effect of changes in water temperatures are likely to shift the boundaries for individual borer species. Overall, warmer climates are expected to increase the metabolic activity of all of these organisms leading to a general reduction in service life.
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