kth.sePublications
Change search
Refine search result
123 1 - 50 of 118
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Bryne, Lars Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lausamaa, J.
    Ernstsson, M.
    Englund, Finn
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Söderström, Ove
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    UV-laser irradiated wood: Some aspects on micromorphology, wettability, surface composition and liquid permeability2008In: Proceedings of the 4th meeting of the Nordic-Baltic network in wood material science and engineering (WSE), 2008, p. 75-82Conference paper (Refereed)
    Abstract [en]

    Many wood products used as building or construction materials involve a combination of the wood material with polymers, such as adhesives, coatings, preservatives and binders in composites. Combinations of wood and polymers in outdoor exposure, however, in general have poor long-term durability. A major cause of the unsatisfactory durability can be related to the high hygroscopicity of wood and the great difference in hygro-thermal properties between the components, resulting in wood-polymer de-bonding. In addition, mechanical processing (e.g. sawing, sanding and planning) of wood in general forms a weak boundary layer of loose and crushed wood cells in the surface which also may interfere with the wood-polymer bonding. The main objective of this work was to study ultra violet (EV), or excimer, laser irradiation on wood as a means to remove, by ablation, the outer deformed layer from a wood substrate. Effects of the UV-laser treatment on wetting and liquid permeability characteristics were studied by Wilhelmy plate experiments, and effects on the wood surface chemistry were studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The micromorphology of wood was studied by low vacuum-scanning electron microscopy (LV-SEM). The pre-treatment of wood substrates by UV-laser ablation resulted in a notable changes in surface micromorphology, liquid permeability, wettability and surface chemistry characteristics.

  • 2.
    Bryne, Lars-Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lausmaa, Jukka
    SP Technical Research Institute of Sweden, Chemistry and Materials Technology, Borås, Sweden.
    Ernstsson, Marie
    Institute for Surface Chemistry, Stockholm, Sweden.
    Englund, Finn
    SP Trätek, Technical Research Institute of Sweden, Wood Technology, Borås, Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ageing of modified wood: Part 2: Determination of surface composition of acetylated, furfurylated, and thermally modified wood by XPS and ToF-SIMS2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 305-313Article in journal (Refereed)
    Abstract [en]

    The main objective of this work was to study the chemical composition of surfaces and ageing effects on acetylated pine (Pinus sylvestris), heat treated spruce (Picea abies), and furfurylated radiata pine (Pinus radiata) in comparison to unmodified wood. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were the instruments of choice. Observation with a low-vacuum scanning electron microscope (LV-SEM) complemented the study. The spectroscopic information was also linked to a parallel wettability study on matched wood samples by the Wilhelmy method. The results show that XPS and ToF-SIMS are two powerful tools that in combination give complementary information, both quantitative and qualitative, and are well suited for observation of the ageing process of different wood surfaces. The hydrophobization process as a result of migration of extractives during ageing was well quantified by the XPS measurements and the results correlated well with wetting results. Several specific hydrophobic substances could be identified by ToF-SIMS measurements.

  • 3.
    Bryne, Lars-Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ageing of modified wood: Part 1: Wetting properties of acetylated, furfurylated, and thermally modified2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 295-304Article in journal (Refereed)
    Abstract [en]

    The main objective of this work was to apply contact angle analysis to predict work of adhesion (W-a) between some modified wood materials and certain thermoplastics and adhesives. Wetting properties, i.e., contact angles, were measured by the Wilhelmy method on both freshly prepared and aged veneer samples of unmodified and acetylated Scots pine, furfurylated radiata pine, and heat treated Norway spruce. The sessile drop method was used to measure contact angles on a phenol resorcinol formaldehyde, an emulsion polymer isocyanate, and a one-component polyurethane adhesive. Contact angle data were also collected from the literature on polyethylene, polyvinyl chloride, polymethyl methacrylate, polystyrene, and Nylon 6. Contact angle analysis based on the Chang-Qin-Chen model was then applied to determine so-called acid-base interaction parameters and W-a between the wood samples and the selected thermoplastics and adhesives. Results show that the ageing process led to an increased hydrophobic character of unmodified, heat treated, and furfurylated wood samples. The freshly prepared acetylated wood samples had a pronounced hydrophobic character which remained approximately constant after ageing. The predicted W-a between the wood and the adhesives was considerably higher than that between the wood and the thermoplastics. Furthermore, the predicted W-a between the acetylated wood and both the thermoplastics and water was approximately unchanged when comparing the fresh and aged samples. In contrast, the ageing of all other wood samples resulted in a dramatic decrease of the wood-water W-a and a moderate decrease of the wood-thermoplastics W-a. The wood-adhesives W-a, however, was unchanged for the unmodified and furfurylated wood when comparing the fresh and aged samples and even increased for heat treated and acetylated wood samples.

  • 4.
    Crocetti, Roberto
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lappalainen, Kaj
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Backman, Matthias
    KTH.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Norén, J.
    Multiple shear plane connections with timber based gusset plates2021In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an experimental study conducted on multiple-shear joints consisting of gusset plates made of either LVL or plywood connected to the timber members by means of full-threaded self-tapping screw. Both hardwood and softwood timber based gusset plates with different thickness and face grain orientations were investigated. The results show that this type of connection has an excellent structural performance, with not very dissimilar strength from that of comparable connections which makes use of slotted-in steel plates and dowels. It is believed, therefore, that the proposed solution can be a valid alternative to the more traditional timber connection with slotted-in steel plates and dowels.

  • 5.
    Debertolis, Mattia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Wang, Yue
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wang, Tianxiang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Investigation on mechanical connections with birch plywood gusset plates2023In: 19th Annual Meeting of the Northern European Network for Wood Science and Engineering / [ed] Erik Larnøy, Ås, Norway: The Nordic Forest Research Cooperation Commitee , 2023, p. 96-98Conference paper (Refereed)
    Abstract [en]

    The construction industry is increasingly driven by sustainability concerns, prompting a search for alternative materials with a low environmental footprint, such as engineered wood products. Nowadays, connections of timber elements are still performed by the use of steel plates. However, steel plates can be replaced by plywood made of birch since it has superior mechanical properties compared to plywood made from softwood (Wang et al. 2021, 2022; Crocetti et al. 2021; Werner Åström, 2019). Besides, the capacity calculation for this connection according to the standards is conservative, meaning that the efficiency is low and the actual capacity could be much higher than the design value (Rossi et al. 2016). This research aims to enhance the knowledge and the design process of timber-to-timber connections with birch plywood (BP) plates.

    Download full text (pdf)
    WSE2023_Proceedings_MattiaDebertolis
  • 6.
    Englund, F.
    et al.
    Technical Research Institute of Sweden.
    Bryne, Lars Elof
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ernstsson, M.
    Institute for Surface Chemistry, Stockholm, Sweden.
    Lausmaa, J.
    SP Technical Research Institute of Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Spectroscopic studies of surface chemical composition and wettability of modified wood2009In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 4, no 1-2, p. 80-85Article in journal (Refereed)
    Abstract [en]

    Recent advances in spectroscopic methods used in the surface science field may provide new valuable information about the surface chemical composition of engineering materials. Such methods, combined with wettability analyses, have been applied in the development of well-designed adhesives and coating systems for newly developed and commercially available modified wood materials. The main objective of this paper is to demonstrate and present some aspects on the application of two different state-of-the-art spectroscopic methods for surface chemical composition studies of a complex material such as modified wood. The methods are X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), the former generating more quantitative data and the latter more qualitative data. The spectroscopic data are also combined with wettability data obtained from contact angle measurements using the Wilhelmy method. Modified wood samples were prepared from pilot plant or commercially produced acetylated, furfurylated and thermally modified wood. Effects of wood surface ageing, i.e. the time after machining, on the surface chemical composition and wettability were also studied. Results clearly indicate a hydrophobization process due to ageing of the unmodified and certain modified wood, probably mainly related to a migration and reformation of extractives in the surface. The surface composition and wettability of acetylated wood was not appreciably affected by the ageing process. Such findings could be quantified by the XPS measurements, which is further discussed and related to the different wood modification routes. ToF- SIMS is a powerful tool and complementary to XPS for identification of, for example, specific hydrophobic substances in the wood surfaces. In addition, this method provides ion images, mapping the lateral distribution of selected secondary ions signals within an analysed wood surface area.

  • 7.
    Englund, F.
    et al.
    Technical Research Institute of Sweden.
    Bryne, Lars-Elof
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ernstsson, Marie
    Institute for Surface Chemistry, Stockholm, Sweden.
    Lausmaa, J
    SP Technical Research Institute of Sweden.
    Wålinder, M. E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Some Aspects on the Determination of Surface Chemical Composition and Wettability of Modified Wood2009In: Proceedings of the Fourth European Conference on Wood Modification / [ed] F. Englund, C.A.S. Hill, H. Militz and B.K. Segerholm, Stockholm: SP Technical Research Institute of Sweden , 2009, p. 553-560Conference paper (Refereed)
  • 8.
    Falk, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Function and design of innovative bio-based products for the building sector2016In: Structures and Architecture - Proceedings of the 3rd International Conference on Structures and Architecture, ICSA 2016, CRC Press/Balkema , 2016, p. 93-101Conference paper (Refereed)
    Abstract [en]

    This paper will present a study of preconditions for competitiveness in a resource saving society. Preconditions for material suppliers and industry versus requirements from legislation and consumers means a balance, which can be difficult to manage. The paper is aiming for an analysis of the preconditions for property modification, innovation and marketing of biobased materials and products, and the paper deals with strategies to release the architectural potential of bio-based construction. 

  • 9.
    Gardner, D. J.
    et al.
    University of Maine.
    Tascioglu, C
    Wålinder, M. E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wood composite protection2003In: Wood Deterioration and Preservation / [ed] B. Goodell, D. Nicholas, and T.P. Schultz,, American Chemical Society , 2003, p. 399-419Chapter in book (Refereed)
    Abstract [en]

    Wood composites should be protected against microbial and insect attack when used outdoors, especially in construction applications with prolonged exposure to moisture. Preservative systems and treatment processes affect composite properties, especially adhesive/wood bonding and mechanical properties. Several common systems for preservation of composites include, 1) the use of pretreated wood, applicable particularly to some solid lumber laminates; 2) in-process preservative treatments favored for composites made from flakes, particles, and fibers where the preservative treatment is incorporated during the manufacturing process; 3) post-process preservative treatments which are generally favored for wood composites made from lumber and veneer; and 4) the use of recycled treated wood elements in manufacturing or the use of wood species with a high natural resistance against biodegradation. This chapter discusses these four preservative methods and presents a general overview of current research concerning preservation practices and techniques in North America including the effect of preservatives on composite properties, durability issues, and degradation modes.

  • 10.
    Gardner, D. J.
    et al.
    University of Maine.
    Wålinder, Magnus
    Trätek Swedish Institute for Wood Technology Research.
    Editorial note2006In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 20, no 8, p. 723-723Article in journal (Other academic)
  • 11.
    Gardner, D. J.
    et al.
    University of Maine.
    Wålinder, MagnusTrätek Swedish Institute for Wood Technology Research.
    Special issue on wood adhesion and adhesives2006Collection (editor) (Refereed)
  • 12. Gardner, Douglas J.
    et al.
    Wålinder, Magnus
    Trätek Swedish Institute for Wood Technology Research.
    Special Issue on Wood Adhesion and Adhesives2006In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 20, no 8, p. 725-727Article in journal (Other academic)
  • 13.
    Inoue, Masafumi
    et al.
    University of Tokyo.
    Kawai, Shuichi
    Kyoto University.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rowell, Roger M.
    USDA, Forest Service, Forest Products Laboratory, Madison USA.
    Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame2008In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 3, no 3-4, p. 119-125Article in journal (Refereed)
    Abstract [en]

    Abstract The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160?200°C), pressures (0.5?3 MPa) and hot-pressing times (2?16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending.

  • 14.
    Källander, B
    et al.
    SP Technical research Institute of Sweden.
    Wålinder, M. E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    European Industry-Academic Cooperation2006In: Wood Adhesives 2005 / [ed] C. Frihart, Madison: Forest Products Society , 2006, p. 15-22Conference paper (Refereed)
  • 15.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Altgen, Michael
    Georg August Univ Gottingen, Wood Biol & Wood Prod, DE-37077 Gottingen, Germany.;Aalto Univ, Dept Bioprod & Biosyst, FI-00076 Aalto, Finland..
    Militz, Holger
    Georg August Univ Gottingen, Wood Biol & Wood Prod, DE-37077 Gottingen, Germany..
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Sorption and surface energy properties of thermally modified spruce wood components2018In: Wood and Fiber Science, ISSN 0735-6161, Vol. 50, no 3, p. 346-357Article in journal (Refereed)
    Abstract [en]

    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.

  • 16.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Laine, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Sedighi Moghaddam, Maziar
    SP Technical Research Institute of Sweden.
    Rohumaa, Anti
    Aalto University, Department of Forest Products Technology.
    Segerholm, Kristoffer
    SP Technical Research Institute of Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    The influence of log soaking temperature and thermal modification on the properties of birch veneers2016In: IRG Annual Meeting, IRG Documents , 2016Conference paper (Other academic)
    Abstract [en]

    In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.

  • 17.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lillqvist, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Spoljaric, Steven
    Univ Melbourne, Nanostruct Interfaces & Mat Sci NIMS Grp, Melbourne, Vic 3010, Australia..
    Seppala, Jukka
    Aalto Univ, Dept Chem & Met Engn, Espoo 00076, Finland..
    Segerholm, Kristoffer
    RISE Res Inst Sweden, Div Bioecon, Stockholm, Sweden..
    Rautkari, Lauri
    Aalto Univ, Dept Bioprod & Biosyst, Espoo 00076, Finland..
    Hughes, Mark
    Aalto Univ, Dept Bioprod & Biosyst, Espoo 00076, Finland..
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Effects of water soaking-drying cycles on thermally modified spruce wood-plastic composites2020In: Wood and Fiber Science, ISSN 0735-6161, Vol. 52, no 1, p. 2-12Article in journal (Refereed)
    Abstract [en]

    The overall aim of this work was to gain more insight on the potential of modified wood (TMW) components for use in wood-thermoplastic composites (WPCs). Laboratory-scale TMWPCs were produced, and the effects of severe water soaking-drying cycles on the samples were studied. Water sorption behavior and resulting dimensional and micromorphological changes were also studied, and the results were compared with those of unmodified wood-plastic composites (UWPCs) used as control. The TMW was prepared by cutting a spruce board into half and subjecting one-half to an atmosphere of superheated steam at atmospheric pressure with a peak temperature of 210 degrees C, with the other unmodified wood (UW) half as a control. The TMW and UW components were then prepared by a Wiley mill and thereafter sifted into smaller (mesh 0.20-0.40 mm) and larger (mesh 0.40-0.63 mm) size fractions. A portion of the wood components were also subjected to hydrothermal extraction (HE). Composite samples with these different wood components, polypropylene (PP) matrix, and maleated PP (MAPP) as coupling agent (50/48/2 wood/PP/MAPP ratio by weight) were then prepared by using a Brabender mixer followed by hot pressing. The matching micromorphology of the composites before and after the soaking-drying cycles was analyzed using a surface preparation technique based on ultraviolet-laser ablation combined with scanning electron microscopy. The results of the water absorption tests showed, as hypothesized, a significantly reduced water absorption and resulting thickness swelling at the end of a soaking cycle for the TMWPCs compared with the controls (UWPCs). The water absorption was reduced with about 50-70% for TMWPC and 60-75% for HE-TMWPC. The thickness swelling for TMWPCs was reduced with about 40-70% compared with the controls. Similarly, the WPCs with HE-UW components absorbed about 20-45% less moisture and showed a reduced thickness swelling of about 25-40% compared with the controls. These observations also were in agreement with the micromorphology analysis of the composites before and after the moisture cycling which showed a more pronounced wood-plastic interfacial cracking (de-bonding) as well as other microstructure changes in the controls compared with those prepared with TMW and HE-UW components. Based on these observations, it is suggested that these potential bio-based building materials show increased potential durability for applications in harsh outdoor environments, in particular TMWPCs with a well-defined and comparably small size fractions of TMW components.

  • 18.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Moghaddam, Maziar Sedighi
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Liquid sorption, swelling and surface energy properties of unmodified and thermally modified Scots pine heartwood after extraction2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 3, p. 251-258Article in journal (Refereed)
    Abstract [en]

    The effect of extractives removal on liquid sorption, swelling and surface energy properties of unmodified wood (UW) and thermally modified Scots pine heartwood (hW) (TMW) was studied. The extraction was performed by a Soxtec procedure with a series of solvents and the results were observed by the multicycle Wilhelmy plate method, inverse gas chromatography (IGC) and Fourier transform infrared (FTIR) spectroscopy. A significantly lower rate of water uptake was found for the extracted UW, compared with the unextracted one. This is due to a contamination effect in the latter case from water-soluble extractives increasing the capillary flow into the wood voids, proven by the decreased water surface tension. The swelling in water increased after extraction 1.7 and 3 times in the cases of UW and TMW, respectively. The dispersive part of the surface energy was lower for the extracted TMW compared to the other sample groups, indicating an almost complete removal of the extractives. The FTIR spectra of the extracts showed the presence of phenolic compounds but also resin acids and aliphatic compounds.

  • 19.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ormondroyd, Graham
    Biocomposites Centre, Bangor University, United Kingdom.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden, Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden, Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Surface energy characteristics of refined fibres at different pressures2014In: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014) / [ed] Wilson, Peter, 2014, p. 134-138Conference paper (Other academic)
    Abstract [en]

    Wood fibres were produced on the pilot scale refiner at the BioComposites Centre, Bangor University, from a commercially sourced mix of chipped wood. The fibres were produced at refiner pressure 4, 6, 8 and 10 bar and dried in the associated flash drier. Surface energy characterization of the refined fibres was performed using inverse gas chromatography (IGC). The dispersive part of the total surface energy was analysed for duplicates of fibre samples at the four different refiner pressures. Non-polar alkane probes were used for the dispersive surface energy analysis at different surface coverage. Results indicate that the processing pressure has an effect of the dispersive surface energy and IGC analysis could be developed as a tool both for process development and process control in refining fibres.

  • 20.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Aalto University, Department of Forest Products Technology.
    Johansson, Leena-Sisko
    Aalto University, Department of Forest Products Technology.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Laine, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Aalto University, Department of Forest Products Technology.
    Surface chemical analysis and water vapour sorpion of thermally modified wood exposed to increased relative humidity2015In: The Eighth European Conference on Wood Modification (ECWM8) 2015 / [ed] Mark Hughes, Lauri Rautkari, Tuuli Uimonen, Holger Militz and Brigitte Junge, 2015Conference paper (Other academic)
    Abstract [en]

    The increased interest in environmentally friendly building materials is accompanied with an increased need for research on thermally modified wood. Products made from recycling or reusing of thermally modified residuals will have advantages in terms of environmental aspects. Surface characteristics of thermally modified wood play an important role for the development of applications involving bonding processes, for example when using thermally modified wood residuals in biocomposites. Surface chemistry characteristics are important in developing such materials. A technique used for surface chemical analysis of the outermost surface is X‑ray photoelectron spectroscopy (XPS). Some surface chemical analyses of wood and modified wood can be found in Nzokou and Kamdem (2005), Inari et al. (2006), Bryne et al. (2010), Johansson et al. (2012), Rautkari et al. (2012). Furthermore, the influence of water and moisture has crucial effect on the properties of wood and wood products. Water vapour sorption properties of hygroscopic materials can be studied using a dynamic vapour sorption (DVS) instrument. Previous studies on thermally modified wood exposed to several sorption cycles using DVS have shown an increase in hysteresis during the first cycle, compared with unmodified wood (Hill et al., 2012). However, during the second and the third sorption cycle a reduction in sorption hysteresis was observed.

     

    The objective of this work was to study the surface chemical composition and water vapour sorption properties of thermally modified wood. In particular, an effort was made to study any influence on such properties due to a previous exposure to a high relative humidity (RH). Interpretations of the results indicate a decrease of extractable or volatile organic components and a relative increase of non-extractable components, for the high humidity-exposed samples. This could be due to remaining extractives migrating towards or redistribution at the wood surface layer as a result of moisture diffusion. The DVS results show that the thermally modified wood samples that had been exposed to the high relative humidity condition revealed a slight decrease of the hysteresis of the sorption isotherms. The opposite trend was furthermore seen for the unmodified wood.

  • 21.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Johansson, Leena-Sisko
    Aalto University, Finland.
    Campbell, JM
    Department of Forest Products Technology, Aalto University.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden, Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Laine, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Water vapour sorption characteristics and surface chemical composition of thermally modified spruce (Picea abies karst)2016In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 7, no 3, p. 116-123Article in journal (Refereed)
    Abstract [en]

    The objective of this work was to study the hygroscopicity and surface chemical composition of thermally modified (TM) spruce. An effort was also made to study if those features were influenced by a previous exposure to a significant increase in relative humidity (RH). TM and unmodified Norway spruce (Picea abies Karst) samples, both in solid and ground form, were prepared. Water vapour sorption characteristics of the ground samples were obtained by measuring sorption isotherms using a dynamic vapour sorption (DVS). The surface chemical composition of the solid samples, both acetone extracted and non-extracted, were analysed using X-ray photoelectron spectroscopy (XPS). The DVS analysis indicated that the TM wood exposed to the 75% RH revealed a decrease in isotherm hysteresis. The XPS analysis indicated a decrease of acetone extractable or volatile organic components and a relative increase of non-extractable components for the samples exposed to the increased RH condition.

  • 22.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Johansson, Leena-Sisko
    Department of Forest Products Technology, Aalto University.
    Campbell, Joseph
    Department of Forest Products Technology, Aalto University.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Water vapour sorption characteristics and surface chemical composition of thermally modified spruceManuscript (preprint) (Other academic)
  • 23.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Wood Material Science and Technology, Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden.
    Water vapour sorption properties and surface chemical analysis of thermally modified wood particles2014In: Recent Advances in the field of TH and THM Wood Treatment, 2014Conference paper (Other academic)
  • 24.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, Dennis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Surface energy characterization at different moisture levels of thermally modified wood using inverse gas chromatography2013In: Proceedings of the 9th meeting of the Northern European Network for Wood Science and Engineering (WSE) / [ed] Briscke, C. & Meyer, L., 2013, p. 130-135Conference paper (Other academic)
  • 25.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Surface energy characterization of thermally modified wood particles exposed to humidity cycling using inverse gas chromatography2014In: / [ed] Nunes, L., Jones, D., Hill, C. and Militz, H., 2014Conference paper (Other academic)
    Abstract [en]

    The objective of this work was to study surface energetics of thermally modified wood particles exposed to dry-humid cycling. This information can give insight in the adhesion properties between the modified wood and composite matrices, adhesives or coatings. The surface energy characterization as well as the dry-humid cycling was performed using inverse gas chromatography (IGC). Duplicates of thermally modified and unmodified spruce particles with size 0-0.125 mm were investigated and conditioned in dry-humid cycles at 0-75 % RH and 0‑25 % RH. The BET specific surface area as well as the dispersive surface energy heterogeneity (or distribution) at different surface coverage was determined. The results showed similar trends for the different cycles in the dry and humid states, respectively. The difference in dispersive surface energy distribution between the dry and humid state was more pronounced at the lower surface coverage.

  • 26.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, Dennis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Surface energy characterization of thermally modified wood using inverse gas chromatography2013Conference paper (Other academic)
    Abstract [en]

    The objective of this work is to characterize surface energetics of thermally modified wood. Such information may be useful for a better understanding and predictions of adhesion properties between the modified wood and other material systems, e.g. coatings, adhesives or matrices in composites. Inverse gas chromatography (IGC) was used to study the surface energy characteristics of thermally modified spruce in particle form. Two different wood component samples were prepared, one with a larger and one with a smaller particle size distribution. Measurements of BET specific surface area and dispersive surface energy distribution of the particle samples are presented. Results indicate that a ground wood component of a finer size distribution of thermally modified wood is less energetically heterogeneous compared with a component with a larger size distribution.

  • 27.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, Dennis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Physico-chemical characterization of THM modified wood using inverse gas chromatography (IGC)2013In: Evaluation, processing and prediction of THM treated wood behaviour by experimental and numerical methods, 2013, p. 35-36Conference paper (Other academic)
  • 28.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions2015In: Wood and Fiber Science, ISSN 0735-6161, Vol. 47, no 4, p. 410-420Article in journal (Refereed)
    Abstract [en]

    The surface energy of unmodified and thermally modified spruce wood components was researched at dry and moist conditions using inverse gas chromatography. The results indicate a more pronounced heterogeneous nature of the thermally modified wood surfaces in terms of the dispersive (nonpolar) component of the surface energy, compared with that of the unmodified wood surfaces. The dispersive component of the surface energy of the thermally modified wood ranged between 44 and 38 mJ/m(2) corresponding to an increase in surface coverage from a low level and up to about 10%. Suggested explanations for the more distinct heterogeneity of the thermally modified wood sample are related to chemical changes of the wood substance which seem to result in certain micromorphological features observed by scanning electron microscopy as alternated fracture surfaces created in the grinding process; and also possible changes or redistribution of the wood extractives. An increase of the MC, representing a change from a dry condition of approximately 0% RH to ca 75% RH, of both the unmodified and thermally modified samples seemed to have a marginal influence on the dispersive component of the surface energy. Possible implications of the results in this study can be found in the tailoring of new compatible and durable material combinations, for example, when using thermally modified wood residuals as a component in new types of biocomposites.

  • 29.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden, Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, L.
    Hughes, M.
    Lankveld, C.
    Surface densification of acetylated wood2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 6, p. 829-835Article in journal (Refereed)
    Abstract [en]

    The mechanical properties of wood can be improved by compressing its porous structure between heated metal plates. By adjusting the process parameters it is possible to target the densification only in the surface region of wood where the property improvements are mostly needed in applications, such as flooring. The compressed form is, however, sensitive to moisture and will recover to some extent in high humidity. In this study, therefore, acetylated radiata pine was utilised in the surface densification process in order to both reduce the set-recovery of densified wood and to improve the hardness of the acetylated wood. Pre-acetylation was found to significantly reduce the set-recovery of surface densified wood. However, after the second cycle the increase in set-recovery of acetylated wood was relatively higher than the un-acetylated wood. The acetylated samples were compressed by only 1 mm (instead of the target 2 mm), yet, the hardness and hardness recovery of the acetylated samples significantly increased as a result of densification. It was also discovered that rough (un-planed) surfaces may be surface densified, however, even if the surface became smooth to the touch, the appearance remained uneven.

  • 30.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Hughes, Mark
    Wood densification and thermal modification: hardness, set-recovery and micromorphology2016In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, no 5, p. 883-894Article in journal (Refereed)
    Abstract [en]

    The density of wood can be increased by compressing the porous structure under suitable moisture and temperature conditions. One aim of such densification is to improve surface hardness, and therefore, densified wood might be particularly suitable for flooring products. After compression, however, the deformed wood material is sensitive to moisture, and in this case, recovered up to 60 % of the deformation in water-soaking. This phenomenon, termed set-recovery, was reduced by thermally modifying the wood after densification. This study presents the influence of compression ratio (CR = 40, 50, 60 %) and thermal modification time (TM = 2, 4, 6 h) on the hardness and set-recovery of densified wood. Previously, set-recovery has mainly been studied separately from other properties of densified wood, while in this work, set-recovery was also studied in relation to hardness. The results show that set-recovery was almost eliminated with TM 6 h in the case of CR 40 and 50 %. Hardness significantly increased due to densification and even doubled compared to non-densified samples with a CR of 50 %. Set-recovery reduced the hardness of densified (non-TM) wood back to the original level. TM maintained the hardness of densified wood at an increased level after set-recovery. However, some reduction in hardness was recorded even if set-recovery was almost eliminated.

  • 31.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Hughes, Mark
    Department of Forest Products Technology, Aalto University.
    Källbom, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, Dennis
    SP Tech Res Inst Sweden.
    Hardness, set-recovery and micromorphology studies of densified and thermally modified wood2015Conference paper (Other academic)
    Abstract [en]

    The purpose of the work reported in this paper was to increase the density of Scots pine wood in order to improve its hardness. Density was increased by compressing the porous structure of wood between heated metal plates in the radial direction by 40, 50 or 60% of the thickness. The compressed state was stabilised by thermally modifying (TM) the samples at 200 °C under steam conditions for 2, 4 or 6h. Set-recovery was almost eliminated (<1%) with TM of 6h for samples compressed 40 and 50%. It was discovered that hardness of densified wood was in some cases even three times higher compared to untreated wood. However, the hardness of the densified, non-TM wood was reduced after soaking and drying back to the original untreated level, while TM of 4 and 6h maintained an increased level of hardness.

  • 32.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Hughes, Mark
    Department of Forest Products Technology, Aalto University.
    Rowell, Roger
    Department of Biological Systems Engineering, University of Wisconsin, Madison, WI USA.
    Acetylation and densification of wood2015Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to explore the possibility to surface densify acetylated solid wood. The aim of surface densification is to improve mechanical properties, such as hardness, at the very surface of wood where the property improvements are mostly needed (e.g. in flooring and decking). However, when subjected to moisture, surface densified wood may swell back almost to the original dimensions. Therefore, acetylated and non-acetylated wood was surface densified in order to investigate whether the dimensional stability of densified wood may be improved by pre-acetylation. Surface densification was performed by compressing the acetylated radiate pine samples between metal plates with only one side heated (150°C) in order to target the deformation to one surface only. The original thickness of the samples was 20 mm and the target thickness 18 mm which was controlled by metal stops. The recovery of the deformation (set-recovery) was measured by soaking the samples in water and measuring the oven-dry thickness before and after soaking in repeated cycles. It was found that acetylated wood may be surface densified and indeed the set-recovery of the pre-acetylated wood was significantly lower (17.4 %) compared to non-acetylated wood (72.8 %). Further studies in adjusting the process parameters might lead to even higher reduction in set-recovery.

  • 33. Laine, Kristiina
    et al.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Ormondroyd, Graham
    Hughes, Mark
    Jones, Dennis
    Micromorphological studies of surface densified wood2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 5, p. 2027-2034Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) wood was surface densified in its radial direction in an open press with one heated plate to obtain a higher density on the wood surface whilst retaining the overall thickness of the sample. This study investigated the effect of temperature (100, 150 and 200 A degrees C) and press closing speed (5, 10 and 30 mm/min, giving closing times of 60, 30 and 10 s, respectively) on the micromorphology of the cell-wall, as well as changes occurring during set-recovery of the densified wood. The micromorphology was analysed using scanning electron microscopy (SEM) combined with a sample preparation technique based on ultraviolet-excimer laser ablation. Furthermore, the density profiles of the samples were measured. Low press temperature (100 A degrees C) and short closing time (10 s) resulted in more deformation through the whole thickness, whilst increasing the temperature (150 and 200 A degrees C) and prolonging the closing time (30 and 60 s) enabled more targeted deformation closer to the heated plate. The deformation occurred in the earlywood regions as curling and twisting of the radial cell-walls, however, no apparent cell-wall disruption or internal fracture was observed, even at low temperatures and fast press closing speed, nor after soaking and drying of the samples. In the SEM-analysis after soaking and drying, it was noticed that the cells did not completely recover their original form. Thus, part of the deformation was considered permanent perhaps due to viscoelastic flow and plastic deformation of the cell-wall components.

  • 34. Larsson Brelid, Pia
    et al.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Alfredsen, Gry
    Westin, Mats
    Wålinder, Magnus
    Trätek - Swedish Institute for Wood Technology Research, Stockholm, Sweden.
    Wood Plastic Composites with Improved Dimensional Stability and Biological Resistance2006In: 2nd International Conference on Environmentally-Compatible Forest Products, 2006Conference paper (Other academic)
  • 35. Larsson Brelid, Pia
    et al.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Westin, Mats
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wood Plastic Composites from Modified Wood: Part 1 - Conceptual idea, mechanical and physical properties2006In: The 37th Annual Meeting of the International Research Group on Wood Preservation, 2006Conference paper (Other academic)
  • 36.
    Larsson, Magnus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Optimisation of timber structures based on weighted objectives2017In: Proceedings of the 13th annual meeting of the Northern European Network for Wood Science and Engineering , September 28-29 / [ed] Engelund Thybring, E., 2017, p. 79-84Conference paper (Other academic)
    Abstract [en]

    Contextual optimisation workspace (COW) is a digital design tool under developmentthat seeks to promote novel processes for the parametric design of architectural andengineering structures using multiple-objective optimisation (MOO) strategies based onevolutionary algorithms. Assembled within the Grasshopper (GH) graphical algorithmeditor, the tool allows for constructive analytical comparisons between often conflictingaspects of a design that have historically been assumed incomparable, with the resultingcompromises between objectives presented as iterations of a three-dimensionalgeometry with associated data. This increases the capability to make informeddecisions throughout the design process and to control the implementation of apotentially wide range of differing design objectives. This is useful in situations wherean extended design team (more than one stakeholder) is collaborating on anarchitectural project, which would include most real-life applications. In such a team, allagents have different preferred outcomes. The effort to manage their expectations andfulfil their respective agendas becomes the aim of the resulting architectural scheme.This paper explores how the COW tool could benefit from the addition of componentsthat simplify such decision-making processes, and showcases how such additions couldbe applied to the design of timber structures. Two new GH user objects were designedthat simplify an extended and weighted control of MOO-based design actions usingCOW, while providing a mechanism that guarantees designs are not considered if theydo not meet the minimal requirements set by the constraining frame conditions. Suchstakeholder-based MOO designs are shown to be a beneficial addition to the COWsystem. It is argued that a more comprehensive version of this first attempt to allowdiffering desires to be used as a weighted part of the design process is a promisingstrategy for the design of future timber structures.

    Download full text (pdf)
    fulltext
  • 37.
    Larsson, Magnus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Falk, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Teleodynamic timber façades2018In: Frontiers in Built Environment, E-ISSN 2297-3362, Vol. 4, article id 37Article in journal (Refereed)
    Abstract [en]

    This paper investigates ways in which weathering-related site conditions can be allowed to inform the design process in order to improve a building's geometry and performance. Providing a building design with the capacity to remember past experiences and anticipate future events can provide substantial gains to the architectural configuration and engineering of a timber façade. A new theory of architecture is outlined based on recent “teleodynamic” theories—a hypothesis about the way far-from-equilibrium systems interact and combine to produce emergent patterns. The proposed explanation considers nested levels of thermodynamic systems applied to an architectural context: “homeodynamic” operations that involve equilibration and dissipation of constraint combine to produce self-organising “morphodynamic” procedures that amplify and regularise site-specific constraining data streams. A teleodynamic design reconstitutes itself by combining morphodynamic processes so as to optimise its relationship to the past, present, and future. A novel teleodynamic design tool called Contextual Optimisation Workspace (COW) is assembled within the Grasshopper visual programming environment. The tool is used to carry out four experiments that combine to produce the teleodynamic design of an urban wooden façade, exemplifying an alternative framework for the design of wood-based structures. The first experiment investigates a variegated grid combining two distinct subdivision methods (an orthogonal grid and a Voronoi tessellation), transmuting one system into another. The second and third experiments focus on durability aspects of a wooden façade and devise strategies for how the effects of photochemical degradation and wetting due to driving rain might be minimised using the COW tool. The fourth experiment optimises the building for daylight based on an illuminance simulation. Using simulation and anticipation to add the advantages of site- and time-specific data streams as a design strategy can effectively suspend an algorithm-driven design iteration in time and space in order to allow it to be parametrically influenced by past or future events such as unique site and project conditions. The COW tool can be used to produce such teleodynamic designs.

  • 38.
    Larsson, Magnus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Falk, Andreas
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Erlandsson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Novel Processes for Architectural Optimisation of Building Materials Performance: Introducing Material Phase Transitions and Generative Life Cycle AssessmentsIn: Article in journal (Refereed)
    Abstract [en]

    Conventional phase diagrams plot differences in properties (e.g. volume) of a medium generated by changes in external conditions (e.g. temperature and/or pressure). This paper discusses how the logic of such diagrams can be applied to produce a new type of surface plot, material phase transition (MPT) diagrams, that chart not the conditions for chemical equilibrium but the relative benefits of a particular material system given a set of predefined objectives and a virtual search space of design solutions. Such diagrams can form an integral part of parametric design processes that use ‘auxiliary loads’ (e.g. LCA values) as variables to generate design iterations. A Grasshopper user object is created and used to design a box beam that yields a set of auxiliary loads charts and MPT diagrams. The anatomy of MPT diagrams is described, and areas for future studies discussed.

  • 39.
    Larsson, Magnus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Falk, Andreas
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Erlandsson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Sliding Sidewinders: Early-Stage Design of an Anticipatory Adaptive AssemblageIn: Article in journal (Refereed)
    Abstract [en]

    This quantitative/qualitative evaluation of meta-heuristic design processes being implemented in a real-life architecture project introduces the theoretical concept of anticipatory adaptive assemblages (AAA) and reports on tactics that were used to reduce the ‘curse of dimensionality’ associated with the mechanisms that produce such assemblages. It describes strategies to adopt ‘presilient’ methods to constrain a model’s design space before any evolutionary solving occurs, leverage the advantage in fenestration performance presumed to arise from explorations of non-periodic tessellations of the plane, and use benchmark models to optimise some material aspects of wall sections. These tactics all support a materiality-based approach to designing architecture using genetic algorithms. The experiments were designed in an attempt to begin to close the knowledge gap between on the one hand the existing praxis of LCA-based analyses, on the other simulations that use material properties to directly inform geometries associated with particular combinations of (for instance) site, weather, and material data. The hypothesis is that AAA’s can become an effective framework for design-based adaptation to site conditions and mitigation of climate change. The objectives of the study are a) to implicitly and qualitatively describe the trials and tribulations a commercial adaptation of alternative design processes may cause, while b) explicitly and quantitatively report on the results of the experiments, and how they relate to AAAs. After an introduction of the AAA concept, three design experiments are described and their outcomes analysed, followed by a concluding discussion including suggestions for future studies.

  • 40. Larsson-Brelid, P.
    et al.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Westin, M.
    Rowell, Roger
    Ecobuild a center for development of fully biobased material systems and furniture applications2008In: Molecular Crystals and Liquid Crystals, ISSN 1542-1406, Vol. 484, p. 623-630Article in journal (Refereed)
    Abstract [en]

    There is a great incentive and motivation in the building and wood research communities as well as in the industry to develop more eco-efficient and durable wood-based products with better performances. In this context, eco-efficient products refer to "green" sustainable products where both economical and ecological aspects have to be balanced. This presentation will give the general strategies within the newly formed Swedish Institute Excellence Center, EcoBuild. The conceptual idea for this competence centre is a conversion of biomass into innovative, eco-efficient and durable wood based products. The vision is that EcoBuild will, through the formation of a university-institute-industry cooperation, act as an international leading innovation, research and technology development platform within the wood science and technology field. The research projects within the centre are guided by a group of about 30 industry partners and also by end-user demands (Fig. 1). Types of materials in focus are: modified solid wood such as heat treated, furfurylated and acetylated wood, biobased binders and coatings, and biocomposites. A top priority is to develop fully biobased products, i.e., all raw materials should preferably be biobased, including chemicals for modification, adhesives, and surface treatment. Aspects and initial results regarding some of the EcoBuild activities will also be presented. Examples of research projects already started are: 1) Novel bio-based board resins; 2) UV-resistant clear coatings for exterior use; 3) Highly durable WPCs for outdoor use based on modified wood particles; 4) Modification of hardwood for exterior applications; 5) Fundamental understanding of the mechanisms involved in the durability of modified wood.

  • 41. Li, T.
    et al.
    Cai, J. -B
    Avramidis, S.
    Cheng, D. -L
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Zhou, D. -G
    Effect of conditioning history on the characterization of hardness of thermo-mechanical densified and heat treated poplar wood2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 6, p. 515-520Article in journal (Refereed)
    Abstract [en]

    Poplar wood was modified by a combination of thermo-mechanical densification (TMD) and heat treatment (HT) process at five temperatures ranging from 170 to 210°C. A new two-step conditioning method (CM) is suggested, in the course of which the modified wood is submitted to 50°C/99% RH→25°C/65% RH, where RH means relative humidity in the climate chamber. The traditional one-step CM (25°C/65% RH) served as reference. The effects of conditioning history on hardness were observed and analyzed along with the change of dimensional stability. The hardness of the modified wood was lower in the case of the proposed CM due to more set-recovery release, but the extent of that decreased with the HT temperature. For a good hardness, HT200°C should be selected with the proposed CM, which is different from the optimization output of 180°C obtained from the traditional CM. In conclusion, a specific assessment method for the performance characterization of this type of modified wood would be beneficial for the combined TMD and HT processes.

  • 42.
    Li, Tao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Nanjing Forestry University, China.
    Cheng, D. -L
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Zhou, D. -G
    Wettability of oil heat-treated bamboo and bonding strength of laminated bamboo board2015In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 69, p. 15-20Article in journal (Refereed)
    Abstract [en]

    In order to improve the interface properties of bamboo in laminated board applications for severe outdoor environment, bamboo sheets were heat treated in soybean oil and post oil extracted in this paper. Following oil heat treatment at 180 degrees C for 2 h, bamboo specimens were either removed from the oil immediately or left in the oil until they were cooled to room temperature. Contact angle measurements before and after oil heat treatment showed a significant increase in the hydrophobicity of bamboo, and these changes differed based on the process parameters. Results from scanning electron microscopy and Fourier transform infrared spectroscopy indicated that these phenomena may be due to the combination effect of the change of chemical composition and the surplus oil on the surface of modified bamboo. Then, the ethanol extraction process was subsequently applied to remove the surplus oil. Finally, the results of bonding strength tests on laminated bamboo boards prepared from oil heat-treated samples which thereafter had been subjected to ethanol extraction showed acceptable interface properties, although lower than the reference.

  • 43. Li, Tao
    et al.
    Cheng, Da-li
    Avramidis, Stavros
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Zhou, Ding-guo
    Response of hygroscopicity to heat treatment and its relation to durability of thermally modified wood2017In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 144, p. 671-676Article in journal (Refereed)
    Abstract [en]

    In an attempt to study the effect of heat treatment on hygroscopicity and durability of wood, Poplar (Populus spp.) wood was thermally modified using five different temperatures between 170 degrees C and 210 degrees C, for a fixed duration of 3 h. Moisture adsorption behavior and the resistance to soft rot fungi were investigated thereafter. Based on the Hailwood-Horrobin sorption model, the amount of available sorption sites within specimens for the different groups of Poplar wood were calculated from the model's m(0) parameter. Chemical analysis of the changes in wood components induced by heat treatment allows for a comparison between the easily obtained m(0) and the results of time-consuming wood decay tests. The proposed m(0)-based method for highly efficient evaluation and prediction of durability of thermally modified wood could optimize future research on the mechanisms of heat treatment processes.

  • 44.
    Lillqvist, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rohumaa, A
    LaBoMaP, Ecole Nationale Supérieure d'Arts et Métiers.
    Källbom, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Aalto University.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    THE INFLUENCE OF THERMAL MODIFICATION ON VENEER BOND STRENGTH2017In: Proceedings of the 13th annual meeting of the Northern European Network for Wood Science and Engineering, September 28-29 / [ed] Engelund Thybring, E., 2017, p. 56-Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to investigate the effect of thermal modification on birchveneer properties relevant in plywood manufacture. The wood material used in thisstudy was a birch (Betula pendula Roth) stem sectioned into small logs nominally 1.2 min length. The logs were completely immersed in a water tank heated to either 70 °C or20 °C. The soaked logs were rotary cut on an industrial scale lathe (Model 3HV66;Raute Oyj, Lahti, Finland) into veneer with a nominal thickness of 0.8 mm.Veneer specimens (150x150 mm2) were cut and thermally modified at 200°C in steamconditions for 2, 4 and 8 h. Mass loss and equilibrium moisture content (EMC) weremeasured after modification. The bond strength of the veneers was measured withautomated bonding evaluation system (ABES- Adhesive Evaluation Systems, Inc.,Corvallis, Oregon, USA) using phenol formaldehyde (PF) resin (Prefere 14J021, PrefereResins Finland Oy, Hamina, Finland). Specimens (20 x 117 mm2), were cut from theconditioned veneer sheets. A liquid PF resin was applied to an area of 5 x 20 mm2 atone end of the veneer specimens (approx. spread rate 100 g m-2). After adhesiveapplication, the veneer-resin assembly was placed into the ABES and after 180 s ofpressing (130 °C and 2.0 MPa) the shear strength of adhesive bond was measured.As expected from previous studies, the mass loss increased and EMC reduced withlonger thermal modification time. No significant difference in mass loss or EMCbetween log soaking temperatures was recorded in this study. The thermal modificationslightly reduced the bond strength; however, longer treatment time did not furtherreduce the bond strength. Therefore, based on this study, thermally modified veneerscould be successfully bonded and

    Download full text (pdf)
    fulltext
  • 45. Ormondroyd, G. A.
    et al.
    Källbom, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Curling, S. F.
    Stefanowski, B. K.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, D.
    Water sorption, surface structure and surface energy characteristics of wood composite fibres refined at different pressures2016In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, p. 1-8Article in journal (Refereed)
    Abstract [en]

    During fibre processing, wood fibres are subjected to a range of physical and chemical conditions sufficient to slightly alter their chemical composition and hence their ultimate performance when used in the manufacture of wood fibre-based composites. In order to better understand the effects of refiner conditions on material performance, wood fibres were subjected to processing at different refiner pressures (4, 6, 8 and 10 bar) and subsequently dried in a flash drier. The fibres were analysed for changes in surface area, surface energy, surface structure and water vapour sorption characteristics. The methods applied were nitrogen adsorption utilising the Brunauer–Emmett–Teller theory, inverse gas chromatography, scanning electron microscopy and dynamic vapour sorption. It was found that increasing refiner pressure resulted in fibres of lower surface area, accompanied by increasing dispersive surface energies up to operating refiner pressures of 8 bar. It was found with fibres refined at different pressures that as the refiner pressure increased the equilibrium moisture content of the fibre decreased at the set relative humidities. However, it was also noted that the hysteresis was not significantly different between each of the refiner pressures. The results suggest that different refiner pressures can be used to tune the surface characteristics which may be beneficial to product development and the improvement of the environmental profile of the wood fibre composites.

  • 46.
    Peñaloza, Diego
    et al.
    KTH. RISE Res Inst Sweden, Eklandagatan 86, S-41261 Gothenburg, Sweden.
    Erlandsson, Martin
    IVL Swedish Environm Res Inst, Valhallavagen 8, S-11427 Stockholm, Sweden..
    Berlin, Johanna
    RISE Res Inst Sweden, Eklandagatan 86, S-41261 Gothenburg, Sweden..
    Wålinder, Magnus
    KTH.
    Falk, Andreas
    KTH.
    Future scenarios for climate mitigation of new construction in Sweden: Effects of different technological pathways2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 187, p. 1025-1035Article in journal (Refereed)
    Abstract [en]

    A variety of climate mitigation strategies is available to mitigate climate impacts of buildings. Several studies evaluating the effectiveness of these strategies have been performed at the building stock level, but do not consider the technological change in building material manufacturing. The objective of this study is to evaluate the climate mitigation effects of increasing the use of biobased materials in the construction of new residential dwellings in Sweden under future scenarios related to technological change. A model to estimate the climate impact from Swedish new dwellings has been proposed combining official statistics and life cycle assessment data of seven different dwelling typologies. Eight future scenarios for increased use of harvested wood products are explored under different pathways for changes in the market share of typologies and in energy generation. The results show that an increased use of harvested wood products results in lower climate impacts in all scenarios evaluated, but reductions decrease if the use of low-impact concrete expands more rapidly or under optimistic energy scenarios. Results are highly sensitive to the choice of climate impact metric. The Swedish construction sector can only reach maximum climate change mitigation scenarios if the low-impact building typologies are implemented together and rapidly.

  • 47. Ruponen, J.
    et al.
    Kimpimäki, S.
    Rohumaa, A.
    Laine, Kristiina
    KTH.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, L.
    Hughes, M.
    Tensile-shear strength studies on self-bonded 2-ply birch veneer joint manufactured and tested by applying Automated Bonding Evaluation System (ABES) hot press2016In: WCTE 2016 - World Conference on Timber Engineering, Vienna University of Technology , 2016Conference paper (Refereed)
    Abstract [en]

    An Automatic Bond Evaluation System (ABES) hot press was employed to manufacture a self-bonded joint between two veneers of rotary-cut birch (Betula pendula Roth). The hot-pressing conditions were 220 °C and 5.0 MPa, with press times ranging from 180 s to 600 s with 60 s intervals. Additionally, the log-soaking temperature (20 °C and 70 °C) and the veneer initial MC (6% and 11%) were varied to study the effect on the tensile-shear strength of the joints. For one set, the surface properties were altered by acetone extraction. The samples were tested at 11% MC. However, one set was partly duplicated and tested at 6% MC, to study how the testing conditions influenced the bond strength. The maximum average tensile-shear strength was 3.3 MPa, observed after 600 s hot pressing. The studies also included bond-line micromorphology analysis by applying SEM combined with a micromachining surface preparation technique based on UV excimer laser ablation. It was also indicated that longer hot-pressing times, lower veneer initial MC and a lower testing MC resulted in increased tensile-shear strength. Acetone extraction decreased the bond strength with increased standard deviation. Finally, the highest single and average strengths were observed for veneers from higher soaking temperature.

  • 48. Sedighi Moghaddam, M.
    et al.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Multicycle wilhelmy plate method for wetting properties, swelling and liquid sorption of wood2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 39, p. 12145-12153Article in journal (Refereed)
    Abstract [en]

    A multicycle Wilhelmy plate method has been developed to investigate wetting properties, liquid sorption, and swelling of porous substrates such as wood. The use of the method is exemplified by studies of wood veneers of Scots pine sapwood and heartwood, which were subjected to repeated immersion and withdrawal in a swelling liquid (water) and in a nonswelling liquid (octane). The swelling liquid changes the sample dimensions during measurements, in particular its perimeter. This, in turn, influences the force registered. A model based on a linear combination of the measured force and final change in sample perimeter is suggested, and validated to elucidate the dynamic perimeter change of wood veneer samples. We show that pine heartwood and pine sapwood differ in several respects in their interaction with water. Pine heartwood showed (i) lower liquid uptake, (ii) lower swelling, (iii) higher contact angle, and (iv) lower level of dissolution of surface active components (extractives) than pine sapwood. We conclude that the method is also suitable for studying wetting properties of other porous and swellable materials. The wettability results were supported by surface chemical analysis using X-ray photoelectron spectroscopy, showing higher extractives and lignin content on heartwood than on sapwood surfaces.

  • 49.
    Sedighi Moghaddam, Maziar
    et al.
    SP Tech Res Inst Sweden, S-11486 Stockholm, Sweden.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wettability and liquid sorption of wood investigated by Wilhelmy plate method2014In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 48, no 1, p. 161-176Article in journal (Refereed)
    Abstract [en]

    The wettability of Scots pine veneers was investigated with different approaches using the Wilhelmy plate method. The probe liquids were water and octane, which differ; in that, water is able to swell the wood sample, whereas octane does not. Novel approaches based on the Wilhelmy plate method to study wettability, liquid penetration, and swelling behavior of wood veneers are introduced. First, immersion to constant depth was performed, and liquid uptake with time was evaluated. Different kinetic regimes, the fastest one associated with contact angle changes and the slowest regime associated with liquid sorption by capillary and diffusion, were observed. Two other approaches, imbibition at constant depth (with initial deeper immersion) and full immersion, were utilized in order to keep the contact angle constant during measurements. Dynamic wettability studies were done by a multi-cycle (10-20 cycles) Wilhelmy method. Based on this, the time-dependent swelling of wood and changes in sample perimeter could be obtained. Generally, water showed higher absorption than octane. In all wettability studies, and for both probe liquids, the penetration process starts with a fast initial sorption, which is followed by swelling in the case of water.

  • 50.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Heydarihamedani, Golrokh
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tuominen, Mikko
    SP Technical Research Institute of Sweden.
    Fielden, Matthew
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Haapanen, Janne
    TUT Tampere University of Technology, Aerosol Physics Laboratory, Department of Physics.
    Mäkelä, Jyrki M.
    TUT Tampere University of Technology, Aerosol Physics Laboratory, Department of Physics.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Hydrophobisation of wood surfaces by combining liquid flame spray (LFS)and plasma treatment: dynamic wetting properties2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 6, p. 527-537Article in journal (Refereed)
    Abstract [en]

    The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate method, resulting in advancing and receding contact angles as well as sorption behaviour of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and Xray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behaviour. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

123 1 - 50 of 118
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf