| 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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