| 1. |
- Elustondo, Diego, et al.
(författare)
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Localized wood surface modification, Part I : Method characterization
- 2017
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 12:1, s. 283-295
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses the potential of an open process for treatment of European Scots pine (Pinus sylvestris) with chemicals that could potentially make the surfaces stronger, more dimensionally stable, or more durable, depending on the treatment solution. The method provides an intermediate solution between full volume impregnation by pressure treatment and superficial surface treatment by dipping. Figuratively speaking, the process creates the equivalent of a layer of coating applied below the wood surfaces rather than above. Two different techniques were compared, namely, heating-and-cooling (H & C) and compression-and-expansion (C & E). Taking into account that commercial suppliers recommend 0.15 to 0.25 L/m2 of coating in sawn wood and 0.1 to 0.15 L/m2 in planed wood surfaces, then this study demonstrates that the H & C method can impregnate an equivalent amount of solution under the surfaces in less than 15 min using treatment temperatures below 150 °C. © 2017 North Carolina State University.
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| 2. |
- Neyses, Benedikt, 1986-, et al.
(författare)
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Continuous Wood Surface Densification : Chemical Treatments to Reduce the Set-Recovery
- 2016
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Ingår i: BIOCOMP 2016. - Concepción : University of Concepción. ; , s. 66-77
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Konferensbidrag (refereegranskat)abstract
- The hardness of the outer surface of solid wood can be improved by densification, and this opens up new fields of application for low-density species. So far, surface densification is carried out in time- and energy-consuming batch processes, and this means that potential advantages over more expensive hardwood species or non- renewable materials are lost. One of the crucial problems in all densification processes is to reduce the moisture-induced set-recovery of the densified wood cells. In a previous study, a new high-speed continuous surface densification process was introduced, where the surface of solid Scots pine boards could be densified at speeds of up to 80 m/min by a roller pressing technique. The aim of the present study was to integrate the roller pressing technique with different pre- and post-treatment methods to reduce the set- recovery. An aqueous solution of sodium hydroxide was used as a pre-treatment agent to activate the wood surface prior to densification, and a methacrylate ester monomer solution was used as an impregnation agent, both before and after densification. After densification and impregnation, the methacrylate monomers are polymerized by curing in an oven at 100°C in order to stabilize the compressed wood cells. The results show that the different treatments had no significant effect on the set-recovery, probably due to insufficient penetration into the wood material. Future work will focus on improving the treatment process and integrating all process steps into a fully continuous and automatic process.
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| 3. |
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| 4. |
- Sandberg, Karin, et al.
(författare)
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IPOS - Innovations in wood-based building materials and products
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- IPOS Swedish wood- Innovation POtential for the biobased Society, is a coordination project within Bioinnovation Construction & Design. The coordination project IPOS has been led by Karin Sandberg RISE Research Institutes of Sweden. This report consists of results from four subprojects (SP) within IPOS compiled by the project leaders. Innovations and development of new wood-based products to increase the value of the raw material have been in focus in the four subprojects. Common for the subprojects are the effort for developing new materials, processes, products and manufacturing methods as well as market and product development DeProtion -Design, Product development & Communication (SP1) The purpose has been to collaboratively develop a general innovative product development model that supports the wood industry's development of products with value-adding design and/or with the support of design automation. Compiled by Fredrik Henriksson, Linköping University in chapter 2. Demand driven finishing of Swedish wood (SP2) The purpose has been to ensure efficient processes that can deliver the right wood material for continued processing within the value chains for industrial wood construction, as well as exterior and interior carpentry products. Compiled by Bror Sundqvist Luleå University of Technology in chapter 3. The Facade of the city Swift, Stylish, Smart (SP3) The purpose has been to increase the market for wooden facades and therefore develop a concept for an attractive functional facade system of pine adapted for urban environment with regards to design, fire, competitive cost and environmental profile. Compiled by Karin Sandberg Research Institutes of Sweden in chapter 4. Outdoor load-bearing timber structures (SP4) The purpose has been to extend the scope of chemically modified wood (acetylation) for load-bearing outdoor structures and Scandinavian wood species, pine and birch. Compiled by Erik Serrano, Lund University in chapter 5. In all sub-projects work has aimed at developing new materials, processes and products and at the same time taking into account market- and communication aspects. The sub-projects have in various ways developed and improved products made from Swedish wood species, primarily Scots pine and spruce, but also birch. Through collaboration, via IPOS, the sharing of knowledge between the projects has contributed to strengthening the wood value chain more than the individual projects could have done. The main conclusions are below summarized under the three headings “Renewal for the pine market”, Development of innovative products” and “New businesses and markets”.
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| 5. |
- Sundqvist, Bror, et al.
(författare)
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Cellulose degradation during hydrothermal treatment of birch wood (Betula pubescens Ehrh.)
- 2006
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Ingår i: Cellulose Chemistry and Technology. - 0576-9787. ; 40:3-4, s. 217-221
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Tidskriftsartikel (refereegranskat)abstract
- Study of cellulose degradation during wood's heat treatment showed a considerable degradation in both commercially and laboratory heat-treated wood samples, probably due to the low pH induced by the heat treatment. Experimental series were performed for investigating cellulose degradation in birch wood, at different pH levels and times, during heat treatments performed at pH values of 4, 7 and 10, for 3 and 6 hours at 180°C. The results show that the selected span of pH and time of treatment clearly affects the size of the cellulose molecules. Study of cellulose degradation involved intrinsic viscosity measurements on α-cellulose from the samples. As a result of heat treatment, viscosity drops from 1430 mL/g (untreated wood) to less than or equal 700 mL/g and less than or equal 350 mL/g, for durations of 3 and 6 hours, respectively. The wood buffered in an aqueous solution at pH 4 showed a drop in intrinsic viscosity around 880 mL/g, while a sample of commercial "thermowood" yielded an intrinsic viscosity of 732 mL/g. For neutral and alkaline pH values, the drop in viscosity is considerably lower. At pH values of 7 and 10, a 3 hr treatment had almost no effect on the degree of polymerisation, while a 6 hr treatment gave intrinsic viscosities around 1000 mL/g and 1216 mL/g, respectively. There is a distinct relation between cellulose's molecular size and wood's strength properties. The decrease in cellulose length in unbuffered systems may affect the strength properties of the treated wood. The experiments show that pH is an important factor to consider.
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| 6. |
- Sundqvist, Bror
(författare)
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Color response of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens) subjected to heat treatment in capillary phase
- 2002
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 60:2, s. 106-114
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Tidskriftsartikel (refereegranskat)abstract
- Clearwood of Scots pine, Norway spruce, and birch was subjected to heat treatment while capillary water was kept in the wood. The treatments were performed on initially green wood from 65 °C to 95 °C from 0 to 6 days, followed by drying at 35 °C for 2 days. Color measurements, CIEL*C*h color space, were made on dry planed samples using a photoelectric colorimeter. Treatment time was more important than temperature for birch sapwood regarding the color responses, while time and temperature were of similar importance for pine and spruce. Birch sapwood became much redder and darker compared with pine and spruce. The darkening accelerated generally when treatment temperature exceeded approximately 80 °C. Pine and spruce showed generally similar color responses, untreated and treated, except for pine heartwood untreated, which showed a more saturated color. Pine treated at 65 °C and 80 °C showed red-yellow shift and yellow-red shift for sap- and heartwood respectively, as time elapsed. The color homogeneity was less for birch sapwood than for pine and spruce, and the homogeneity was generally indicated to decrease with increasing treatment temperature.
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| 7. |
- Sundqvist, Bror
(författare)
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Colour changes and acid formation in wood during heating
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heating wood has since ancient times been a method to dry and modify its properties. Nowadays heat is used in industrial processes for the same reasons. Treatment at temperatures above 150ºC can change the colour, improve resistance to biodegradation and enhance dimensional stability. However, losses in the mechanical strength of wood may also occur, and this drawback is a limitation for the use of heat-treated wood in a broad range of products. This thesis suggests that cellulose degradation can contribute to the loss of mechanical strength in wood under high-temperature treatment. The formation of formic and acetic acid during heat treatment of birch wood has been studied. Substantial amounts of acetic acid (at most 7.2% by weight) and formic acid (at most 1.1% by weight) were found in autoclave experiments at temperatures between 160ºC and 200ºC. It was also found that the average molecular size of both commercially heat-treated birch wood and birch wood treated in laboratory experiments under acidic pH conditions was considerably reduced (42%–53%) in comparison to untreated birch wood. It is reasonable to think that the formation of acid and the accompanying decrease in average cellulose molecular size have a crucial influence on the observed decrease of mechanical strength in heat-treated wood. The thesis suggests that wood can be heat-treated while maintaining mechanical strength through a process design that keeps the wood in neutral to alkaline conditions. This thesis also describes studies of colour development in birch, Norway spruce and Scots pine wood during hydrothermal treatment, with special reference to treatment at temperatures between 65ºC and 95ºC with high moisture content. The colour responses of wood that had been heat treated or kiln dried have been investigated, and the colour coordinates Lightness (L*), Chroma (Cab*), hue (h) and colour difference DEab* are presented. It is shown that colour changes associated with heat treatment at high temperatures can be obtained by treatment for long periods at temperatures around 100ºC. Such treatments will lead to changes in colour, but presumably no change in dimensional stability or resistance to biodegradation. The origin of colour formation in wood as a result of heating is briefly investigated and discussed. Colour stability during accelerated UV/Visible light exposure of heat-treated samples has been tested and the results are presented in this thesis. The colour responses of birch, Norway spruce and Scots pine wood were measured after drying in laboratory kiln experiments in the interval of 40º– 111ºC, and it was concluded that the average wood colour of a batch can be controlled by regulating time and temperature. There are some results that show an increase (around 20%) in the mechanical strength of birch wood for heat treatment around 180º–200ºC for approximately 1 hour and that colour measurements may be used as a way to monitor and control the phenomenon. However, further experiments will have to be made to confirm these indications.
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| 8. |
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| 9. |
- Sundqvist, Bror, et al.
(författare)
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Cross-laminated wood panels in a patient room and studies of interior environment
- 2023
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Ingår i: World conference on timber engineering 2023 (WCTE 2023). - : World Conference on Timber Engineering (WCTE). - 9781713873273 - 9781713873297 ; , s. 1062-1066
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Konferensbidrag (refereegranskat)abstract
- Studies on the effect from biobased materials and products on humans have indicated positive effects. This has earlier been shown in studies for e.g. hospitals, where indications of lower stress and pain in patients with wood as part ofinterior solutions. This paper describes the first step of a larger study that investigates the interior environment and the response of patients. The study presented here measured RH, temperature, emissions of volatile organic compounds (VOC) and microbial activities in two rooms at a hospital in Skellefteá, Orthopaedic ward. One room had a cross-laminated wood panel covering 42% ofwalls, window reveal and doors, and the other a control room with standard coverings. Results indicated only a small difference between the rooms in terms of temperature and RH. VOC emissions varied in both rooms but all concentrations were lower or much lower than threshold values for interior air quality standard limits. Biological contamination ofthe surfaces and from air sampling was also performed. Conclusions of this experimental study shows that from a regulatory perspective it is possible and safe to use wood as interior product.
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| 10. |
- Sundqvist, Bror, et al.
(författare)
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Determination of formic-acid and acetic acid concentrations formed during hydrothermal treatment of birch wood and its relation to colour, strength and hardness
- 2006
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Ingår i: Wood Science and Technology. - : Springer Science and Business Media LLC. - 0043-7719 .- 1432-5225. ; 40:7, s. 549-561
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Tidskriftsartikel (refereegranskat)abstract
- Formation of benzyl esters from acetic and formic acids during heat treatment of birch at 160-200°C has been studied by gas chromatography. High concentrations of formic and acetic acids formed by the wood itself during hydrothermal treatment were found. The concentrations of acids increased with both treatment time and temperature. The maximum formic- and acetic acid concentrations found at 180°C and after 4 h of treatment performed in this work were 1.1 and 7.2%, based on dry-weight wood, respectively. The treated wood material was characterised by mechanical testing [bending tests perpendicular to the grain, modulus of rupture, modulus of elasticity, Brinell hardness, impact bending and colour measurements (CIE colour space)]. The experiments, where high concentration of acids was formed, showed severe losses in mass and mechanical strength. Indications of possible enhanced mechanical properties for the treated, compared with untreated birch wood were found around 180-200°C at short treatment times. This paper discusses possible degradation reactions coupled with the colour and mechanical properties in relation to acid formation, and suggestions for process optimisations.
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| 11. |
- Sundqvist, Bror, et al.
(författare)
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The influence of wood polymers and extractives on wood colour induced by hydrothermal treatment
- 2002
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 60:5, s. 375-376
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Tidskriftsartikel (refereegranskat)abstract
- A method to evaluate the influence of wood polymers and extractives on the color of wood subjected to hydrothermal treatment was proposed. As such, the technique used was extraction and color measurements. It was found that both degradation products from wood polymers and extractive compounds were indicated to be participating in the color formation of wood subjected to hydrothermal treatment.
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| 12. |
- Sundqvist, Bror
(författare)
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Värmebehandling av trä : från ett historiskt perspektiv till kommersiell produktion av idag
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Värmebehandling av trä har uråldriga traditioner. Träet får bättre beständighet mot biologisk nedbrytning, får en i vissa fall estetiskt tilltalande mörk genomfärgning och blir mindre hygroskopiskt och mer formstabilt. Ideér om industriell värmebehandling började på 1910-talet i USA och patent på metoder finns från 1940-talet. På 1950- 1960-talet bedrevs forskning och utveckling främst i USA och Tyskland och detta fortsatte fram till 1980- talet i Tyskland. Från 1990-talet har intresset för värmebehandling ökat starkt i Finland, Tyskland, Holland och Frankrike. Detta har lett till kommersiell produktion i framförallt Finland och Holland. Olika industriella processer för värmebehandling finns. Gemensamt för dessa är att inverkan av syrgas reduceras i processen genom deplacering av inert gas eller mättad vattenånga eller genom nedsänkning i oljebad. Värmebehandlingen sker i temperaturer 150ºC till 250ºC upp till flera timmar, i ett eller flera steg. De egenskapsförbättringar som presenteras för värmebehandlat trä är främst ökad rötbeständighet och förbättrad dimensionsstabilitet. De mekaniska styrkegenskaperna minskar generellt tydligt. Sverige saknar både industriell tillverkning och FoU på värmebehandling av trä. Kännedomen om de fysikaliska och kemiska förändringarna under värmebhandling av trä är idag inte fullt kända. Noggrannare kontroll av tid, temperatur, fukt/vatten, tryck, pH, syrgas kan ge bättre egenskaperna för värmebehandlat trä.
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| 13. |
- Sundqvist, Bror
(författare)
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Wood color control during kiln-drying
- 2002
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Ingår i: Forest Products Journal. - 0015-7473. ; 52:2, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- Presents information on a study that investigated the coloration of wood during drying in a laboratory kiln. Research methods; Results and discussion on the study; Conclusions
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| 14. |
- Sundqvist, Bror
(författare)
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Wood colour related to kiln drying
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Raised temperature in artificial drying has led to some changes of wood products such as colour and strength etc. For special treatment of wood-products with clearly modified properties, among them colour, is often high temperature and steam used industrially. Knowledge about the colour rendering from wood that is subjected to heat under humid conditions and/or artificial drying, especially kiln drying, is thus of interest. It is also of interest to understand the chemical background, for the colouring process, for future development of treatment and drying. The stability of the colour of wood exposed to UV/visible-light is also of concern when considering qualitative wood products. The colour response of Scots pine (Pinus sylvestris), Norway spruce (Picea Abies) and birch (Betula pubescens) was studied when exposed to heat and humid air, either as a hydrothermal treatment, where the wood contained capillary (free) water for certain times and temperatures, or a laboratory kiln drying. The wood subjected to hydrothermal treatment was also exposed to UV/visible-light to study the colour stability. The chemical background for the colour change during hydrothermal treatment was briefly investigated by using extraction, thin-layer chromatography (TLC) and UV/Visible-spectroscopy. The results show that multivariate modelling (PLS) of industrial wood-colour is possible as average values for the whole batch, "batch-colour". Quite strong colour changes (DE*ab > 10) were formed using hydrothermal treatment at 80-95ºC for 3-6 days. Furthermore, this quite strong colour formed is similarly stable when exposed to UV/Visible-light for 100 hours as untreated wood. Structure components (cellulose, hemicellulose and lignin) as well as extractive compounds, phenolic types, were both indicated to participate in the colour formation during hydrothermal treatment and the same is expected for kiln drying.
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| 15. |
- Wang, Xiaodong (Alice), et al.
(författare)
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Impact of cold temperatures on the shear strength of Norway spruce joints glued with different adhesives
- 2015
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 73:2, s. 225-233
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Tidskriftsartikel (refereegranskat)abstract
- As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, Norway spruce (Picea abies) joints (150 mm × 20 mm × 10 mm) were bonded with seven commercially available adhesives: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). Each adhesive was tested at six temperatures: 20, −20, −30, −40, −50 and −60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF and PRF adhesives responded to temperature changes in a similar manner to that of the PUR adhesive. The shear strengths of wood joints with PVAc and EPI adhesives were more sensitive to temperature change. At low temperatures, the variability of shear strengths increased with all adhesives. Percent wood failures of joints bonded with different adhesives in most cases were not sensitive to temperature changes.
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| 16. |
- Wang, Xiaodong (Alice), et al.
(författare)
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Shear Strength of Scots Pine Wood and Glued Joints in a Cold Climate
- 2016
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Ingår i: BioResources. - Raleigh, NC : North Carolina State University. - 1930-2126. ; 11:1, s. 944-956
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Tidskriftsartikel (refereegranskat)abstract
- The impact of cold temperatures on the shear strength of Scots pine (Pinus sylvestris) joints glued with seven commercially available adhesives was studied in this work. The cold temperatures investigated were: 20, -20, -30, -40, and -50 degrees C. Generally, within the temperature test range, the shear strength of Scots pine solid wood and wood joints were more resistant to the effect of temperature than those of Norway spruce. As the temperature decreased, only some of the joints' shear strength significantly decreased. In most cases, PUR adhesive yielded the strongest shear strength and MUF adhesive yielded the weakest shear strength. MF adhesive responded to temperature changes in a similar manner to that of PUR and PVAc adhesives. The shear strengths of wood joints with PRF and EPI adhesives were more sensitive to temperature change. For dynamic tests of shear strength, the values for 12-h and 6-day tests under temperature cycles (-20 and 0 degrees C) were compared. The values for 6-day tests were lower than those for 12-h tests. Therefore, the duration of the samples subjected to the same temperature had a significant impact on shear strength. Our results indicate that PUR adhesive is the most stable; whereas the stability of MUF and PRF adhesives decreased significantly.
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| 17. |
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| 18. |
- Wang, Xiaodong (Alice), et al.
(författare)
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Wood construction under cold climate : Part one: Impact of cold temperatures on the shear strength of different adhesives glued wood joints of Norway spruce and Scots pine
- 2014
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Ingår i: WCTE 2014 - World Conference on Timber Engineering, Proceedings. - : World Conference on Timber Engineering (WCTE).
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Konferensbidrag (refereegranskat)abstract
- As wood constructions increasingly use engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives system. The glueline stability is a crucial issue for engineered wood application, especially under cold climate. In this study, Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) joints (150mm x 20mm x 10mm) were bonded with seven commercially available resins (PUR, PVAc, EPI, MF, MUF1, PRF and MUF2) and tested at six temperatures (20, -20, -30, -40, -50 and -60 °C), respectively. Generally, for both species, temperature changes significantly affected shear strength of wood joints. As temperature decreased, the shear strength decreased. PUR resin resulted in the strongest shear strength at all temperatures tested. MF resin responded to temperature changes in a similar ways as the PUR resin. The shear strength of wood joints with EPI resins was sensitive to temperature change. MUF, PRF and PVAc resins demonstrated different characters with Norway spruce and Scot pine. At room temperature, all types of adhesive showed relative stability, in terms of shear strength variation. While at low temperature, the shear strength varied considerably. More specimens need to be tested in further work to more completely present the issue. The EN 301 and EN 302 may need to be specified based on wood species.
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| 19. |
- Westermark, Ulla, et al.
(författare)
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Basic factors influencing the strength loss in heat treatment processes for production of durable wood
- 2005
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Heat treatment of wood leads to improvement of properties such as durability and dimensional stability but also to loss in strength which can be an obstacle for use in wood products. The underlying explanation is often attributed to the degradation of hemicelluloses and lignin. In this work degradation by acid hydrolysis of cellulose is proposed to be a major cause for strength loss in heat treated wood. Hydrothermal treatment was performed at 180°C in a sealed autoclave where the wood samples were soaked in non-buffered and in buffered solutions at pH 4, 7 and 10. Also industrially produced samples of heat treated wood were analysed. The molecular chain length of cellulose was characterized by viscosimetric measurements of dissolved α-cellulose after mild delignification of the samples. The results clearly show that non-buffered systems similar to industrially heat treatment lead to a considerable degradation of cellulose. In the non-buffered systems the pH drops to approximately 3 (room temperature) as a result of heat treatment. Samples from industrially heat treated wood also show cellulose degradation to similar extent as the non-buffered samples. In buffered conditions at pH 7 and pH 10 the degradation of cellulose is clearly diminished. The results indicate that the cellulose degradation can be avoided by modifications that controls or minimizes the effect of acid hydrolysis during the heat treatment process
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| 20. |
- Westermark, Ulla, et al.
(författare)
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Impregnation with PEG and solvolysis of wood : reflections from analysis of the ancient warship Vasa
- 2005
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The paper raises the question if PEG impregnation of wood is a durable method for preservation of waterlogged items or if unexpected chemical reactions under unfavourable conditions can destroy the impregnated wood. In recent years it has been found that polyethylene glykol is an excellent reagent for solvolysis of wood. This means that polyethylene glycol and low concentration of acid completely and rapidly can degrade wood to low molecular weight products (wood liquefacation).
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