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  • 701.
    Voulgaridis, Elias
    et al.
    Aristotle University, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Foti, Dafni
    Aristotle University, Greece.
    Voulgaridou, Eleni
    Aristotle University, Greece.
    ΠΑΡΑΓΩΓΗ ΚΑΙ ΙΔΙΟΤΗΤΕΣ ΠΕΙΡΑΜΑΤΙΚΩΝ ΠΛΙΝΘΩΝ ΕΣΩΤΕΡΙΚΗΣ ΤΟΙΧΟΠΟΙΙΑΣ ΑΠΟ ΓΥΨΟ ΚΑΙ ΑΝΑΚΥΚΛΟΥΜΕΝΑ ΥΛΙΚΑ ΞΥΛΟΥ ΚΑΙ ΕΛΑΣΤΙΚΩΝ ΟΧΗΜΑΤΩΝ: [ Production and properties of experimental bricks for interior walls from gypsum and recycled materials of wood and rubber ]2017Inngår i: ΠΡΑȀΤǿȀΑ : 18ου Πανελλήνιου Δασολογικού Συνεδρίου : “Η Ελληνική Δασοπονία μπροστά σε σημαντικές προκλήσεις: αειφορική διαχείριση δασών, δασικοί χάρτες, περιβαλλοντικές τεχνολογίες – δικτύωση και προστασία φυσικού περιβάλλοντος”: & International Workshop : “Information Technology, Sustainable Development, Scientific Network & Nature Protection” : 8-11 Οκτωβρίου 2017, ΕΔΕΣΣΑ ΠΕȁȁΑΣ, Περιοχή Βαρόσι, Hellenic Forestry Society , 2017, s. 315-323Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Τhe manufacturing and testing of gypsum bonded solid bricks with wood chips from particleboard production residues and rubber and textile fibers from waste tires was investigated. The recovered rubber and wood materials were mixed in gypsum/water solutions for the fabrication of standard solid bricks with six holes by using appropriate molds. After drying, the compressive strength, the thermal conductivity, the air-flow resistance, the sound absorption coefficient and the emissions of volatile organic compounds (VOC) of the bricks were determined. The compressive strength of solid bricks was much greater than that required in interior walls. The bricks showed a better thermal insulation than both the extruded and pressed house bricks but lower than the insulating bricks. Emissions of volatile organic compounds of bricks were at acceptable levels according to regulations for construction products. The sound absorption coefficient of the solid bricks was 0,72 for the frequency of 1 kHz and decreased with increasing frequency. In addition, information on the raw materials and production cost are given.

  • 702. Voulgaridis, Elias
    et al.
    Passialis, Costas
    Adamopoulos, Stergios
    Triantafyllos, D
    Identification of wood and charcoal specimens from the ancient tomb of Mikri Doxipara-Zoni, Evros Prefecture2008Inngår i: National Archaeological Conference, March 13-15, Thessaloniki, Greece, 2008Konferansepaper (Annet vitenskapelig)
  • 703.
    Voulgaridis, Elias
    et al.
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Karastergiou, Sotirios
    Technological Educational Institute of Thessaly, Greece.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Kakaras, Ioannis
    Technological Educational Institute of Thessaly, Greece.
    Foti, Dafni
    Aristotle University of Thessaloniki, Greece.
    Koutsianitis, Dimitrios
    Aristotle University of Thessaloniki, Greece.
    Voulgaridou, Eleni
    Aristotle University of Thessaloniki, Greece.
    Effect of laser drilling on impregnability of fir (Abies borisii regis) and spruce (Picea excelsa) wood2014Inngår i: Wood Structure, Properties and Quality – 2014: 5th RCCWS International Symposium, Moscow State University Press, 2014, s. 51-56Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fir and spruce wood specimens, 2×2 cm in cross section and 34 cm long, were pre-pared with true radial and tangential surfaces. All lateral surfaces of the wood specimens were drilled by laser beams to a depth of 0,4 cm (1/5 of specimen thickness) with two drilling patterns (distance between holes 1×1 cm and 1×2 cm) in order to improve the wood permea-bility of these refractory to impregnation species. After drilling and assessing the drilling ef-fect on mechanical properties of wood, wood specimens, 10 cm long, were impregnated with oil and CCB preservatives by using vacuum (0,6 mmHg) and pressure (1,5 bar) for 15 minutes and 30 minutes, respectively. The effects of the two laser drilling patterns on impreg-nability of fir and spruce wood specimens were measured and assessed. The results showed that both drilling patterns created by laser beams on all lateral surfaces of fir and spruce wood specimens at 0,4 mm depth improved the retention and penetration of preservatives in fir and spruce wood specimens. This effect was more pronounced in fir than in spruce. Between the two drilling patterns, the pattern with distances between holes 1×1 cm was more effective than that with distances 1×2 cm, in both species tested.

  • 704.
    Voulgaridis, Elias
    et al.
    Aristotle Univ Thessaloniki, Greece.
    Passialis, Costas
    Aristotle Univ Thessaloniki, Greece.
    Negri, Martino
    Ivalsa Cnr, Trees & Timber Inst, Italy.
    Adamopoulos, Stergios
    Technol Educ Inst Larissa, Greece.
    Shear bond strength of black locust wood glued with three adhesive systems2012Inngår i: Wood research, ISSN 1336-4561, Vol. 57, nr 3, s. 489-496Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Black locust wood was bonded with three commercial adhesives (PVAc, PU, epoxy) and tested for its shear bond strength against process (treatments I and II) and surface parameters (radial, tangential, roughness). For treatment I (applied pressure 8 bar, press time 1.5 h, curing time 24 h), the mean shear bondstrength was found to be 6.95 N.mm(-2), 5.54 N.mm(-2) and 10.53 N.mm(-2) corresponding to the three adhesives tested, respectively. Increase in press and curing time in treatment II (press time 3 h, curing time 7 days) significantly improved the gluing performance of adhesives, 9.58 N.mm(-2) for PVAc, 13.32 N.mm(-2) for PU and 15.03 N.mm(-2) for epoxy. Surface of gluing (radial, tangential) did not affect the shear bond strength significantly. Failure within wood was found to be up to 40 % for treatment I (PVAc, epoxy) and up to 85 % for treatment II (epoxy). Positive linear regressions were calculated between shearbond strength and wood failure only for PU and epoxy adhesives. Shear bond strength was not related to surface roughness for any adhesive.

  • 705.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Almkvist, Gunnar
    Swedish University of Agricultural Sciences .
    Bader, Thomas K.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Vienna University of Technology, Austria.
    Bjurhager, Ingela
    Uppsala University.
    Rautkari, Lauri
    Aalto University, Finland.
    Gamstedt, E. Kristofer
    Uppsala University.
    The influence of chemical degradation and polyethylene glycol on moisture-dependent cell wall properties of archeological wooden objects: a case study of the Vasa shipwreck2016Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 6, s. 1103-1123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cell wall measures allow for direct assessment of wood modification without the adverse effect of varying density and microstructure. In this study, cell wall properties of recent and archeological oak wood from the Vasa shipwreck were investigated for cell wall stiffness, hardness and creep with respect to effects of chemical degradation, impregnation with a preservation agent, namely polyethylene glycol, and moisture. For this purpose, nanoindentation tests were performed at varying relative humidity, leading to different moisture contents in the wood samples. Concurrently, microstructural and chemical characterization of the mate- rial was conducted. Impregnated and untreated recent oak wood showed a softening effect of both moisture and preservation agent at the wood cell wall level. On the contrary, increased stiffness was found for non-impregnated Vasa oak, which can be explained by aging-related modifications in cell wall components. These effects were counteracted by the softening effect of polyethylene glycol in the impregnated Vasa material, where a lower overall stiffness was measured. The reverse effect of the preservation agent and moisture, namely increased indentation creep of the cell wall material, was revealed. The loss of acetyl groups in the hemicelluloses explained the decreased hygroscopicity of the Vasa oak. In the impregnated Vasa oak, this effect seemed to be partly counteracted by the presence of low-molecular polyethylene glycol contributing to higher hygroscopicity of the cell wall. Thus, the higher overall sorptive capacity of the impregnated Vasa material, with respect to the non-impregnated material, was detected, which has resulted in a sorptive behavior similar to that of recent oak wood. The proposed approach requires only small amounts of material, making it especially suitable for application to precious historical wooden artifacts. 

  • 706. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Cell Wall Properties of Archaelogical Oak Wood from the Vasa Shipwreck: A Nanoindentation Study2015Inngår i: 32nd Danubia-Adria-Symposium (DAS 32), Zilina, Slovakia, 2015, s. 162-163Konferansepaper (Annet vitenskapelig)
  • 707.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Auty, David
    Université Laval, Canada.
    de Borst, Karin
    University of Glasgow, UK.
    Control Parameters for Within-Tree Variability of Wood Stiffness at Different Length Scales: Multiscale Modeling and Experimental Investigations2012Inngår i: COST Action FP0802 - Experimental and Computational Micro-Characterization Techniques in Wood Mechanics, Edinburgh, UK, 2012, s. 72-73Konferansepaper (Annet vitenskapelig)
  • 708.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Auty, David
    University of Aberdeen, UK.
    de Borst, Karin
    University of Glasgow, UK.
    Key parameters controlling stiffness variability within trees: a multiscale experimental–numerical approach2012Inngår i: Trees, ISSN 0931-1890, E-ISSN 1432-2285, Vol. 27, nr 1, s. 321-336Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microstructural properties of wood vary considerably within a tree. Knowledge of these properties and a better understanding of their relationship to the macroscopic mechanical performance of wood are crucial to optimize the yield and economic value of forest stocks. This holds particularly for the end-use requirements in engineering applications. In this study the microstructure–stiffness relationships of Scots pine are examined with a focus on the effects of the microstructural variability on the elastic properties of wood at different length scales. For this purpose, we have augmented microstructural data acquired using SilviScan-3™ (namely wood density, cell dimensions, earlywood and latewood proportion, microfibril angle) with local measurements of these quantities and of the chemical composition derived from wide-angle X-ray scattering, light microscopy, and thermogravimetric analysis, respectively. The stiffness properties were determined by means of ultrasonic tests at the clear wood scale and by means of nanoindentation at the cell wall scale. In addition, micro-mechanical modeling was applied to assess the causal relations between structural and mechanical properties and to complement the experimental investigations. Typical variability profiles of microstructural and mechanical properties are shown from pith to bark, across a single growth ring and from earlywood to latewood. The clear increase of the longitudinal stiffness as well as the rather constant transverse stiffness from pith to bark could be explained by the variation in microfibril angle and wood density over the entire radial distance. The dependence of local cell wall stiffness on the local microfibril angle was also demonstrated. However, the local properties did not necessarily follow the trends observed at the macroscopic scale and exhibited only a weak relationship with the macroscopic mechanical properties. While the relationship between silvicultural practice and wood microstructure remains to be modeled using statistical techniques, the influence of microstructural properties on the macroscopic mechanical behavior of wood can now be described by a physical model. The knowledge gained by these investigations and the availability of a new micromechanical model, which allows transferring these findings to non-tested material, will be valuable for wood quality assessment and optimization in timber engineering.

  • 709. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Mechanical Properties of Scots Pine (Pinus sylvestris L.) Cell Walls After Fungal Degradation: Multiscale Micromechanical Modeling and Experimental Validation2012Konferansepaper (Annet vitenskapelig)
  • 710.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Micromechanical Modelling of Degration Processes in Wood2014Inngår i: 11th. World Congress on Computational Mechanics (WCCM XI), 5th. European Conference on Computational Mechanics (ECCM V), 6th. European Conference on Computational Fluid Dynamics (ECFD VI), July 20 - 25, 2014, Barcelona, Spain, Barcelona, Spain, 2014Konferansepaper (Annet vitenskapelig)
  • 711. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Nanoindentation of Wood Cell Walls: Effects of Different Sample Preparation Methods2013Konferansepaper (Annet vitenskapelig)
  • 712.
    Wagner, Leopold
    et al.
    University of Technology, Austira.
    Bader, Thomas K.
    University of Technology, Austira.
    de Borst, Karin
    University of Glasgow, UK.
    Nanoindentation of wood cell walls: effects of sample preparation and indentation protocol2014Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, nr 1, s. 94-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanoindentation has become a valuable tool in wood science. It enables to examine the mechanical properties of the wood cell walls, which are polymeric, multi-layered structures with typical thicknesses of a few micrometers. Despite the intensive use of the method for the characterization of wood cell walls, it is not entirely clear yet how the measurement results may be affected by the way the sample is prepared and the indentation is carried out. This manuscript contributes to clarify these issues, by presenting indentation data for a variety of sample preparation techniques and indentation protocols, and by critically evaluating the observed differences of the obtained indentation moduli and hardnesses. Investigations covered the effect of different embedding materials, including testing of non-embedded cell walls, and of repeated exposure to high temperatures during harsh drying before the indentation test. Moreover, potential edge effects were studied when the indentation size approaches the width of the individual cell wall layers. Using different embedding materials as well as testing non-embedded cell walls did not lead to significant changes in the measured properties. Due to damage during the sample preparation, non-embedded cell walls tend to show substantially higher experimental scatter. Repeated drying prior to embedding had no significant effect on the resulting moduli and hardnesses. Finally, it was found that reasonable mechanical properties can be extracted from the cell corner middle lamella (CCML), even when the size of the indent approaches the diameter of the CCML.

  • 713. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Eberhardsteiner, Josef
    Nanoindentation to Study Within-Tree Variability of Wood Cell Wall Stiffness2012Inngår i: 29th DANUBIA-ADRIA SYMPOSIUM on Advances in Experimental Mechanics, September 26-29, Belgrade, Serbia, Belgrade, Serbia, 2012, s. 8-9Konferansepaper (Annet vitenskapelig)
  • 714.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    Cell wall properties of softwood deteriorated by fungi: combined chemical analyses, FT-IR spectroscopy, nanoindentation and micromechanical modelling2013Inngår i: Proceedings IRG Annual Meeting, Stockholm: The International Research Group on Wood Protection , 2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Mechanical properties of wood are determined by its inherent hierarchical microstructure, starting at the nanometer scale, where the elementary components cellulose, hemicelluloses, and lignin build up the wood cell wall material. Fungi cause degradation and decomposition of these components and, thus, alter the mechanical properties of wood. The aim of this study is to gain new insight into these relationships at the cell wall level, particularly at early stages of degradation, characterized by a mass loss of less than 10 %. Early detection of deterioration is essential during monitoring of timber structures as it may help avoiding subsequent larger scale damages. This contribution presents results of an ambitious experimental programme covering the determination of earlywood/latewood specific compositional data with consistent microstructural and micromechanical properties. Scots pine (Pinus sylvestris L.) sapwood was studied in reference condition and after degradation by brown rot (Gloeophyllum trabeum) and white rot (Trametes versicolor), respectively. Ultrastructural and compositional data were acquired by means of FT-IR spectroscopy and wet chemical analyses. Micro-structural features, such as the microfibril angle, were determined by X-ray diffraction. Mechanical properties of sound and degraded wood cell walls were determined using nanoindentation, yielding the (anisotropic) indentation modulus of the S2 cell wall layer and the cell corner middle lamella of Scots pine tracheids. Aiming at the identification of relationships between ultrastructural and micromechanical characteristics, two different approaches were followed. On the one hand, multivariate data analysis was applied. On the other hand, a multiscale micromechanical model was used to derive causal relationships between structure and (mechanical) function for deteriorated wood. Anisotropic indentation theory allows calculating model predictions for the indentation modulus of the S2 cell wall layer based on measured chemical compositions resulting from the degradation process. Comparing these predictions with the experimental results enables to test hypotheses on possible scenarios of wood cell wall deterioration during fungal attack. Identified relationships between ultrastructural, microstructural, and micromechanical characteristics will be discussed as well as the potential of micromechanical modelling in the analysis of fungal degradation strategies and their effect on the mechanical behaviour. 

  • 715.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Consequences of Microbial Decay on Mechanical Properties of Wood Cell Walls2015Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    As a natural material, wood is susceptible to degradation processes, preserving equilibrium between buildup and breakdown of biomass. Microorganisms, such as fungi or bacteria, play a major role in the degradation processes in wood. Their activity depends on the environmental conditions: in ambient conditions fungal degradation is dominant while in waterlogged conditions mainly bacterial degradation occurs. Wood exhibits a hierarchical organization. Thus, mechanical properties of a piece of solid wood depend on its inherent heterogeneous microstructure. Starting from the annual rings, individual wood cells and their cell wall layers can be identified as hierarchical levels. The so-called S2 cell wall layer and the middle lamella between individual wood cells dominate the macroscopic behaviour of wood. Thus the properties of these two layers are of particular interest. Their mechanical properties can be assessed by means of nanoindentation. During nanoindentation, a probe is pushed into a flat sample surface and from the subsequent unloading behavior, material properties, such as the indentation modulus and the indentation hardness, can be determined. In contrast to findings at the macroscopic scale, no stiffness losses were detected in degraded cell wall layers. Even slightly increased stiffness of the S2 layer and the middle lamella were measured in material degraded either by fungi or bacteria. Concurrently, microstructural and chemical analyses of the degraded material were conducted. Both multivariate data analysis as well as micromechanical modeling enables establishing structure-function relationships also for degraded wood cell walls.

  • 716.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Fungal degradation of softwood cell walls: Enhanced insight through micromechanical modeling2014Inngår i: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 93, s. 223-234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Fungal degradation is among the greatest hazards for standing trees as well as timber constructions. Herein we aim at gaining more detailed insight into the degradation strategies of wood destroying fungi and the consequences on the mechanical performance of wood. At the macroscale, the occurring losses of mass and of mass density mask effects of altered chemical composition and microstructure. Thus, it is necessary to step down the hierarchical organization of wood to the cell wall scale in order to resolve these changes and their mechanical impact. We present a multiscale micromechanical model which is used to estimate the stiffnesses of the S2 cell wall layer and the compound middle lamella of fungal degraded wood. Data from a detailed chemical, microstructural and micromechanical characterization of white rot and brown rot degraded Scots pine sapwood is analyzed. Comparing predicted cell wall stiffnesses with measured ones confirms the suitability of the approach. The model enables to establish structure–stiffness relationships for fungal degraded wood cell walls and to test hypotheses on yet unknown effects of fungal decay. The latter include the evolution of porosity, modifications of the cell wall polymers resulting in changes of their stiffnesses, as well as increasing cell wall crystallinity. The model predictions in general showed good agreement with the predictions not considering pores in the cell wall. However, this finding does not rule out the formation of porosity. Other degradation related effects like modifications of the cell wall polymers as well as increased crystallinity have the potential to account for stiffness decreases upon the formation of pores.

  • 717.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Nanoindentation and Micromechanical Modeling to Explore the Mechanical Performance of Deteriorated Softwood2011Inngår i: COST Action FP0802 - Experimental and Computational Micro-Characterization Techniques in Wood Mechanics, Helsinki, Finland, 2011, s. 61-62Konferansepaper (Annet vitenskapelig)
  • 718.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    A combined view on composition, molecular structure, and micromechanics of fungal degraded softwood2015Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, nr 4, s. 471-482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fungal decay alters the composition, microstructure, and mechanical properties of wood cell walls. To understand better the structure-function relationships during fungal decay, selected annual rings of fungal deteriorated Scots pine sapwood were analyzed in terms of their composition, microstructure, and micromechanical properties. The datasets were acquired separately for earlywood and latewood concerning the S2 cell wall layer and the cell corner middle lamella (CCML) and analyzed by means of principal component analysis and partial least squares regression analysis. Links between cell wall stiffness and hardness and the composition and microstructure could be established. Increased mechanical properties in the CCML, as obtained by nanoindentation, were correlated to the degradation of pectins. In the S2 layer, the altered data were related to the degradation of hemicelluloses and lignin modification during fungal decay.

  • 719.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bos, Clemence
    Vienna University of Technology, Austria ; Institute for applied materials, Germany.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Effect of Water on the Mechanical Properties of Wood Cell Walls: Results of a Nanoindentation Study2015Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper presents a nanoindentation study on five different wood species in which the elastic and creep properties of the S2 cell wall layer and the middle lamella were determined. Measurements were carried out at relative humidities (RH) ranging from 10 to 80% as well as underwater. Indentation moduli were found to decrease by about a third in the S2 layer and by about half in the middle lamella between RH of 10 and 80%. Hardness dropped by 50 to 60% in this humidity range in both the S2 layer and the middle lamella. Creep parameters were almost constant up to a relative humidity of 40%, but they increased considerably at higher RH. The most pronounced change of reduced moduli and creep properties occurred between 60 and 80% RH, which is consistent with the expected softening of hemicellulose and amorphous parts of cellulose in this humidity region. Immersion into water resulted in a further decrease of the reduced moduli to about 20 to 30% of their values at 10% RH and to only about 10 to 20% for the hardness. This can be explained by additional softening of the less ordered regions of cellulose.

  • 720. Wagner, Leopold
    et al.
    Bos, Clemence
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Moisture-Dependent Mechanical Properties of Softwood and Hardwood Cell walls: A Nanoindentation Study2014Inngår i: 16th International Conference on Experimental Mechanics (ICEM16), July 7-11, 2014, Cambridge, Cambridge, UK, 2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Wood is a hygroscopic material. Increasing moisture decreases the macroscopic mechanical properties of wood. Investigations of the mechanical behaviour of the solid wood substance at the cell wall scale may contribute to an enhanced insight into moisture-mechanics relationships. Wood cells walls are composed of several different layers, of which the S2 layer and the middle lamella (ML) are mechanically most important. Their mechanical properties can be assessed by nanoindentation. Wood of two hardwood species and three softwood species is investigated. Mechanical properties of the S2 layer as well as of the ML are determined at different relative humidity (RH), i.e. at different wood moisture contents (MC).

  • 721. Wagner, Leopold
    et al.
    Bos, Clemence
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Moisture-Dependent Mechanical Properties of Softwood and Hardwood Cell Walls: A Nanoindentation Study2014Inngår i: 31st Danubia-Adria Symposium on Advances in Experimental Mechanics, September 24-27, 2014, Kempten, 2014, s. 151-152Konferansepaper (Annet vitenskapelig)
  • 722. Wagner, Leopold
    et al.
    Fackler, Karin
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Ters, Thomas
    de Borst, Karin
    Fungal Degradation of Scots Pine (Pinus sylvestris L.) Wood: Micromechanical and Microstructural Characterization at the Cell Wall Level2012Inngår i: 7th International Plant Biomechanics Conference, August 20-24, 2012, Clermont-Ferrand, France, Clermont-Ferrand, France, 2012Konferansepaper (Annet vitenskapelig)
  • 723.
    Walford, Brian
    et al.
    Wood Quality and Solid Wood Products Forest Research.
    Ormarsson, Sigurdur
    Prediction of Twist in Poles that Contain Spiral Grain2003Inngår i: IAWPS2003 International Conference on Forest Products, 2003Konferansepaper (Fagfellevurdert)
  • 724.
    Wang, X. A.
    et al.
    Luleå University of Technology.
    Hagman, O.
    Luleå University of Technology.
    Sundqvist, B.
    SP Technical Research Institute of Sweden ; SP Sustainable Built Environment.
    Ormarsson, Sigurdur
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Wan, H.
    Mississippi State University, USA.
    Niemz, P.
    ETH, Switzerland.
    Impact of cold temperatures on the shear strength of Norway spruce & scots pine joints with different glues2016Inngår i: WCTE 2016 - World Conference on Timber Engineering, Vienna University of Technology , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, the impact of cold temperatures on the shear strength of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) joints (150 mm x 20 mm x 10 mm) bonded with seven commercially available adhesives was studied. The cold temperatures investigated were: 20, -20, -30, -40, -50, and -60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints for both species. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. But different adhesives responded differently with Norway spruce and Scots pine.

  • 725.
    Wang, Xiaodong Alice
    et al.
    Luleå University of Technology.
    Björnberg, Jonathan
    Luleå University of Technology.
    Hagman, Olle
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Wan, Hui
    Mississippi State University, USA.
    Niemz, Peter
    Swiss Federal Institute of Technology in Zurich, Switzerland.
    Effect of Low Temperatures on the Block Shear Strength of Norway Spruce Glulam Joints2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 4, s. 9638-9648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The block shear strength of Norway spruce (Picea abies (L.) Karst.) glulam joints was tested under low temperature. Glulam samples were glued with the three of the most common outdoor structural adhesives. The cold temperatures tested were 20, −20, −30, −40, -50 and −60 °C. Within the temperature test range, the block shear strength of the glulam joints was resistant to the effect of temperature. As the temperature decreased, the joints’ block shear strength did not show any significant change. In most cases, phenol-resorcinol-formaldehyde (PRF) adhesive yielded the strongest block shear strength, while melamine-formaldehyde (MF) adhesive yielded the weakest block shear strength. Melamine-urea-formaldehyde (MUF) adhesive yielded similar results to those of MF adhesives for all temperatures tested. The block shear strengths of the glulam joints with PRF, MUF and MF adhesives were not sensitive to temperature change. The results indicated that PRF, MUF and MF adhesives are stable for outdoor structural engineered wood construction in cold climate. The results also suggest that the SS-EN 14080 (2013) standard for the block shear method may not be the proper standard for testing differences in shear strength at different temperatures. The EN 302-1 (2011) standard could be more suitable for this purpose.

  • 726.
    Wang, Xiaodong (Alice)
    et al.
    Luleå Universoty of Technology.
    Hagman, Olle
    Luleå Universoty of Technology.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden.
    Ormarsson, Sigurdur
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Wan, Hui
    Mississippi State University, USA.
    Niemz, Peter
    ETH Zurich, Switzerland.
    Shear Strength of Scots Pine Wood and Glued Joints in a Cold Climate2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 1, s. 944-956Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of cold temperatures on the shear strength of Scots pine (Pinus sylvestris) joints glued with seven commercially available adhesives was studied in this work. The cold temperatures investigated were: 20, -20, -30, -40, and -50 degrees C. Generally, within the temperature test range, the shear strength of Scots pine solid wood and wood joints were more resistant to the effect of temperature than those of Norway spruce. As the temperature decreased, only some of the joints' shear strength significantly decreased. In most cases, PUR adhesive yielded the strongest shear strength and MUF adhesive yielded the weakest shear strength. MF adhesive responded to temperature changes in a similar manner to that of PUR and PVAc adhesives. The shear strengths of wood joints with PRF and EPI adhesives were more sensitive to temperature change. For dynamic tests of shear strength, the values for 12-h and 6-day tests under temperature cycles (-20 and 0 degrees C) were compared. The values for 6-day tests were lower than those for 12-h tests. Therefore, the duration of the samples subjected to the same temperature had a significant impact on shear strength. Our results indicate that PUR adhesive is the most stable; whereas the stability of MUF and PRF adhesives decreased significantly.

  • 727.
    Wang, Xiaodong
    et al.
    Luleå University of Technology.
    Hagman, Olle
    Luleå University of Technology.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Wan, Hui
    Mississippi State University, USA.
    Niemz, Peter
    ETH Zurich.
    Impact of cold temperatures on the shear strength of Norway spruce joints glued with different adhesives2015Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, nr 2, s. 225-233Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, Norway spruce (Picea abies) joints (150 mm × 20 mm × 10 mm) were bonded with seven commercially available adhesives: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). Each adhesive was tested at six temperatures: 20, −20, −30, −40, −50 and −60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF and PRF adhesives responded to temperature changes in a similar manner to that of the PUR adhesive. The shear strengths of wood joints with PVAc and EPI adhesives were more sensitive to temperature change. At low temperatures, the variability of shear strengths increased with all adhesives. Percent wood failures of joints bonded with different adhesives in most cases were not sensitive to temperature changes.

  • 728.
    Wang, Zhao
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Recalcitrance of wood to biochemical conversion: feedstock properties, pretreatment, saccharification, and fermentability2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lignocellulose is an inexpensive and abundant renewable resource that can be used to produce advanced biofuels, green chemicals, and other bio-based products. Pretreatment and efficient enzymatic saccharification are essential features of bioconversion of lignocellulosic biomass. The aims of the research were to achieve a better understanding of the recalcitrance of woody biomass to bioconversion, to explore different pretreatment techniques that can be used to decrease the recalcitrance of the biomass and improve the digestibility of the cellulose, and to investigate by-products of acid pretreatment that cause enzymes and microorganisms to work less efficiently.

    The recalcitrance of wood from aspen, birch, and spruce was investigated before and after acid pretreatment. Before pretreatment, birch exhibited the highest recalcitrance, which was attributed to structural factors. After pretreatment, spruce showed the highest recalcitrance, which was attributed to chemical factors, such as high lignin content. Deacetylation of hybrid aspen in planta by a CE5 acetyl xylan esterase decreased the recalcitrance, and the glucose yield of enzymatic saccharification of non-pretreated wood increased with 27%.

    Pretreatment options based on ionic liquids and steam explosion were further explored. The effects of the anionic constituents of a series of imidazolium-based ionic liquids on pretreatment of aspen and spruce were investigated. [HSO4]− was efficient only for aspen, which was attributed to acid degradation of xylan. [MeCO2]− was efficient for both aspen and spruce, which was attributed to its capability to create a disordered cell wall structure rather than to removal of lignin and hemicellulose. A comparison was made between using sulfuric acid and sulfur dioxide for pretreatment of spruce. Although sulfur dioxide resulted in a pretreatment liquid that was more inhibitory to both enzymes and yeast, it was still superior to pretreatment with sulfuric acid, a phenomenon that was attributed to the particle size of the pretreated material.

    In a comparison of microbial inhibitors in pretreatment liquids from steam explosion of spruce, formaldehyde was found to be the most important inhibitor of yeast. Enzyme inhibition by catalytically non-productive adsorption to lignins and pseudo-lignin was investigated using quantitative proteomics. The results indicate that protein adsorption to pseudo-lignin can be as extensive as adsorption to real lignin. 

    Fulltekst tilgjengelig fra 2019-03-06 00:01
  • 729.
    Wernersson, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datoriserad bildanalys.
    Brun, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys.
    Luengo Hendriks, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datoriserad bildanalys.
    Segmentation of Wood Fibres in 3D CT Images Using Graph Cuts2009Inngår i: Image Analysis and Processing – ICIAP 2009, Berlin: Springer-Verlag , 2009, s. 92-102Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To completely segment all individual wood fibres in volume images of fibrous materials presents a challenging problem but is important in understanding the micro mechanical properties of composite materials. This paper presents a filter that identifies and closes pores in wood fibre walls, simplifying the shape of the fibres. After this filter, a novel segmentation method based on graph cuts identifies individual fibres. The methods are validated on a realistic synthetic fibre data set and then applied on μCT images of wood fibre composites.

  • 730.
    Wernersson, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datoriserad bildanalys.
    Luengo Hendriks, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys.
    Brun, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys.
    Generating synthetic μCT images of wood fibre materials2009Inngår i: Proc. 6th International Symposium on Image and Signal Processing and Analysis: ISPA 2009, Piscataway, NJ: IEEE , 2009, s. 365-370Konferansepaper (Fagfellevurdert)
    Abstract [en]

    X-ray Computerized Tomography at micrometer resolution (μCT) is an important tool for understanding the properties of wood fibre materials such as paper, carton and wood fibre composites. While many image analysis methods have been developed for μCT images in wood science, the evaluation of these methods if often not thorough enough because of the lack of a dataset with ground truth. This paper describes the generation of synthetic μCT volumes of wood fibre materials. Fibres with a high degree of morphological variations are modeled and densely packed into a volume of the material. Using a simulation of the μCT image acquisition process, realistic synthetic images are obtained. This simulation uses noise characterized from a set of μCT images. The synthetic images have a known ground truth, and can therefore be used when evaluating image analysis methods.

  • 731. Wessels, C.B
    et al.
    Crafford, P.L
    du Toit, B
    Grahn, Thomas
    RISE, Innventia.
    Johansson, M
    Lundqvist, Sven-Olof
    RISE, Innventia.
    Säll, H
    Seifert, T
    Variation in physical and mechanical properties from three drought tolerant Eucalyptus species grown on the dry west coast of Southern Africa2016Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, s. 1-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Southern Africa, and specifically its western parts is dominated by low rainfall areas, and it is expected that the rainfall in most of these parts will in future decrease further due to climate change. Woodlots of fast-growing, non-invasive tree species can provide the opportunity to produce wood and release the pressure on natural woodlands, while creating much needed income to inhabitants. Over the last two decades several trials of Eucalyptus species that could potentially withstand arid conditions were established on the South African west coast. The three most promising genotypes according to their volume growth were selected among 46 pure and hybrid species from two 20-year-old trials for further evaluation. These included 10 Eucalyptus grandis × Eucalyptus camaldulensis hybrid trees, 9 Eucalyptus gomphocephala trees, and 9 Eucalyptus cladocalyx trees for a total of 28 trees. The objective of the study reported here was to investigate the within-tree and between species variability of selected physical and processing properties determining the suitability of these three species for lumber production. The density, microfibril angle, spiral grain angle, MOE, MOR, radial and tangential shrinkage, twist, bow, splitting, and collapse were measured in a radial and longitudinal gradient. Valuable insights were gained which could provide decision support for planting, processing and further research on these species when grown in arid conditions. The E. grandis × camaldulensis hybrid was inferior in terms of most relevant properties to the other two species evaluated. The main shortcoming of both E. gomphocephala and E. cladocalyx was the high levels of twist in lumber.

  • 732. Wikete, Christoph
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Jäger, Andreas
    Hofstetter, Karin
    Eberhardsteiner, Josef
    Mechanical Properties and Microstructural Characteristics of Hardwood2010Inngår i: 27th Danubia-Adria Symposium on Advances in Experimental Mechanics : September 22nd - 25th, 2010, Wrocław University of Technology, Wrocław, Poland / [ed] Romuald Be̜dziński, Wroclaw, Poland: Wrocław University of Technology , 2010, s. 237-238Konferansepaper (Annet vitenskapelig)
  • 733.
    Wiklund, Martin
    et al.
    KTH.
    Sandberg, Dick
    KTH, .
    The Concept of Value Activation - Wood Properties at Different Annual Ring Orientation in Pine (Pinus Silvestris L).1998Inngår i: Timber and Wood Composites for the Next Century / [ed] Song-Yung Wang and Min-Chyuan Yeh, 1998Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An integrated R&D program called "Value Activation" has been carried out for the past eight years at the Royal Institute of Technology, Div. of Wood Technology and Processing (KTH-Trä). The concept of Value Activation is focused on the basic understanding of wood, and the fact that there are properties that are not fully exploited in conventional wood manufacturing systems to date. The strategy is to activate these inherent properties by a better understanding of the fundamental behaviour of wood, combined with new applied process technology and the development of the required manufacturing systems.

    The Value Activation program has so far shown that there are great possibilities of utilizing the properties of wood in a better way than our conventional wood production concept can achieve. New wood products with desirable properties can be developed. Most of these products are expected to give a greater added value to the wood. The R&D program will continue with the further development of improved products and also with the development of cost-efficient production systems for implementing the ideas from our R&D in profitable production units.

    Within the Value Activation program the following properties, which were judged to be the most important ones for future wood products were chosen:

    • Aesthetic and tactile factors
    • Controlled moisture movements
    • Accuracy in size and geometry
    • No checks and splits
    • Strength and hardness

    These properties are all strongly influenced by the annual ring orientation in the cross section of the sawn timber. This paper describes the influence of the annual ring orientation on these properties and how they can be improved by using a new sawing pattern.

  • 734.
    Wimmer, Rupert
    et al.
    Univ Bodenkultur Wien BOKU.
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Effects of Reaction Wood on the Performance of Wood and Wood-Based Products2014Inngår i: The Biology of Reaction Wood / [ed] Gardiner, B., Barnett, J., Saranpää, P., Gril, J., Springer, 2014, 1, s. 225-248Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Compression wood in softwoods and tension wood in hardwoods have properties, which adversely affect its usefulness for wood products. This chapter shows that reaction wood can be associated with many unsuitable wood properties. The results vary due to the fact that definitions about occurrence and severity of reaction wood are scarcely documented. A few properties seem to be even benefitting from the presence of reaction wood: the higher smoothness of compression wood surfaces, better shear strength of compression wood, higher toughness and impact resistance when tension wood is present, lower water uptake and swelling in fibreboards containing compression wood, and higher durability against fungi of compression wood. However, these are outweighed by disadvantages, which is the reason why reaction wood has a bad reputation in industry. The problem with reaction wood is that it is in most cases mixed with normal wood, which leads to non-uniform and more variable properties. This may lead to non-uniform swelling and shrinking, causing distortions, with additional problems of reduced strength and unfavourable surface properties. Wood-based materials such as particle boards or fibreboards are generally less prone to problems associated with reaction wood than solid wood products. With knowledge-based production methods the utilization of different wood types, including reaction wood, might be feasible.

  • 735.
    Winzell, Anders
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Rajangam, Alex
    KTH, Skolan för bioteknologi (BIO).
    Arvestad, Lars
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Filling, Charlotta
    KTH, Skolan för bioteknologi (BIO).
    Divine, Christina
    KTH, Skolan för bioteknologi (BIO).
    Aspeborg, Henrik
    KTH, Skolan för bioteknologi (BIO).
    Master, Emma R.
    KTH, Skolan för bioteknologi (BIO).
    Teeri, Tuula T.
    KTH, Skolan för bioteknologi (BIO).
    Sequence Analysis and Recombinant Expression of Family 43 GlycosyltransferasesManuskript (preprint) (Annet vitenskapelig)
  • 736. Wojtasz-Mucha, J.
    et al.
    Hasani, Merima
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hydrothermal pretreatment of wood by mild steam explosion and hot water extraction2017Inngår i: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 241, s. 120-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to compare the two most common hydrothermal pre-treatments for wood – mild steam explosion and hot water extraction – both with the prospect of enabling extraction of hemicelluloses and facilitating further processing. Although both involve autohydrolysis of the lignocellulosic tissue, they are performed under different conditions: the most prominent difference is the rapid, disintegrating, discharge employed in the steam explosion opening up the structure. In this comparative study, the emphasis was placed on local composition of the pre-treated wood chips (of industrially relevant size). The results show that short hot water extraction treatments lead to significant variations in the local composition within the wood chips, while steam explosion accomplishes a comparably more even removal of hemicelluloses due to the advective mass transport during the explosion step.

  • 737.
    Xiao, Zefang
    et al.
    Georg-August-University of Gottingen, Germany.
    Xie, Yanjun
    Northeast Forestry University, Kina.
    Adamopoulos, Stergios
    Georg-August-University of Gottingen, Germany.
    Mai, Carsten
    Georg-August-University of Gottingen, Germany.
    Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood2012Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, nr 4, s. 749-767Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168 h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18 months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks.

  • 738. Yin, Y.
    et al.
    Berglund, L.
    Salmen, L.
    RISE, Innventia.
    Effect of steam treatment on the properties of wood cell walls2011Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, nr 1, s. 194-202Artikkel i tidsskrift (Fagfellevurdert)
  • 739. Yin, Yafang
    et al.
    Berglund, Lars
    Salmen, Lennart
    RISE., Innventia.
    Effect of compressive treatment by steaming on the properties of wood cell walls2011Konferansepaper (Fagfellevurdert)
  • 740.
    Zajaczkowska, Ursula
    et al.
    Warsaw University of Life Sciences.
    Lundqvist, Sven-Olof
    RISE., Innventia.
    Bujalski, Mateusz
    Warsaw University of Life Sciences.
    Reaction wood formation during stem gravitropic response of young Picea Abies (L.) Karst. trees2016Bok (Fagfellevurdert)
  • 741. Zander, A
    et al.
    Hidemark, O
    Thörnqvist, Thomas
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Trä som byggnadsmaterial: -tekniska anvisningar2007Rapport (Annet vitenskapelig)
  • 742.
    Zheng, Chao
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Cellulose-fiber-based thermal insulation materials with fungal resistance, improved water resistance and reaction-to-fire properties2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Thermal insulation materials made from natural fibrous materials, such as cellulose fibers, have advantages over others from a sustainability point of view. However, cellulosic materials are generally prone to mold and absorb moisture, and these have negative effects on the insulation properties, the durability of insulation materials, and interior air quality. In this thesis, cellulose-fiber-based insulation foams were prepared from bleached chemithermomechanical softwood pulp, and these foams showed promising thermal insulation properties and fungal resistance. Hydrophobic extractives were isolated from birch (Betula verrucosa) outer bark and used to improve the water resistance of the foams, which were impregnated in solutions of extractives and then dried. The modified foams showed greater water resistance, and the modification had no negative effects on the thermal insulation, fungal resistance, and compressive strength of the foams.

    Another potential problem with low density cellulosic thermal insulation materials is their poor reaction-to-fire properties. Cellulose-fiber-based insulation foams were prepared from formulations containing bleached chemithermomechanical softwood pulp and commercial fire retardants to improve the reaction of the foams to fire. Single-flame source test results showed that the foams containing 20% expandable graphite (20% EG) or 25% synergetic (25% SY) fire retardant had significantly improved reaction-to-fire properties and passed class E, which reflected that they can resist a small flame attack without substantial flame spreading for a short period according to EN 13501-1. Compared with the reference without any fire retardant, the peak heat release rate (Peak-HRR) of the 20% EG and 25% SY decreased by 62% and 39% respectively when the samples were subjected to a radiance heat flow of 25 kW m-2 in a Cone Calorimeter.

    The thesis demonstrates that it is possible to produce cellulose-fiber-based insulation materials with improved properties in terms of fungal, improved water resistance and reaction-to-fire properties.

  • 743.
    Zheng, Chao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Cellulosic Thermal Insulation with Improved Water Resistance and Fire Retardancy2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Sweden is one of the largest countries by area in Europe, and almost 70% of it is covered by forest. These abundant forest resources benefit the Swedish bioeconomy, but the pulp and paper industry is facing the challenge of a decrease in the demand for printing paper due to a significant shift to electronic media; therefore, it is a priority to use pulp to produce alternative value-added products, such as thermal insulating materials in buildings. Cellulosic thermal insulation can reduce the heating energy consumption of buildings, and decrease the emission of CO2, thus contributing to a sustainable society.

    However, cellulosic thermal insulation needs to overcome its poor water resistance, to lower the risk of fungi and ensure a good interior air quality. In the work described in this thesis, cellulosic insulation materials have been produced from pulp fibers, water, and foaming agent by a foam-forming technique. Hydrophobic extractives isolated from birch outer bark were used to functionalize the insulating materials. These materials showed an improved water resistance due to the intrinsic non-polarity of the extractives, promising thermal insulation properties and fungal resistance.

    Fire retardancy is another challenge for cellulosic thermal insulation, and cellulosic insulation materials were here prepared from formulations containing pulp and commercial fire retardants. Fire test results showed that the materials containing 20% expandable graphite or 25% synergetic fire retardant had a significantly improved fire retardancy, being able to resist a small flame attack for a short period without substantial flame spreading. A study of the mechanism of fire retardancy confirmed that the fire retardants can catalyze the dehydration of pulp and promote the generation of a protective char layer that prevents the materials from further decomposition.

    Bio-based fire-retardant coatings such as sulfonated kraft lignin and nanoclay can provide a more efficient fire-retardant protection on the cellulosic insulation than a fire retardant incorporated in the materials. A nanoclay coating performed the best because of its very good thermal stability. The effective bio-based fire-retardant coating is promising for future use in cellulosic thermal insulation materials.

    Fulltekst tilgjengelig fra 2019-09-14 13:57
  • 744.
    Zheng, Chao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants2018Inngår i: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (Ea).The increased Ea indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased Ea after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the Ea of fire-retarded cellulose thermal insulation compared with the KAS and two methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

  • 745.
    Zheng, Chao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Cellulose-fiber-based insulation materials with improved reaction-to-fire properties2017Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, nr 3, s. 466-472Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The poor reaction-to-fire properties of cellulosic thermal insulation need to be improved to meet the safety regulations for building materials. In this study, cellulose-fiber-based insulation foams were prepared from formulations containing mechanical pulp and commercial fire retardants. Results of single-flame source tests showed that foams developed from the formulations with 20% expandable graphite (EG) or 25% synergetic (SY) fire retardants had substantially improved reaction-to-fire properties, and passed fire class E according to EN 13501-1. The results indicated that the foams could resist a small flame attack without serious flame spreading over a short period of time. Compared with the reference foam that contained no fire retardant, the peak heat release rate of the 20% EG and 25% SY foams decreased by 62% and 39% respectively when the samples were subjected to a radiance heat flux of 25 kW m-2 in a cone calorimeter, which suggested enhanced reaction-to-fire properties of these foams.

  • 746.
    Zheng, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardantsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m2. Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m2, as shown by cone calorimetry and single- flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications as sustainable thermal insulating materials for improved fire retardancy.

  • 747.
    Zheng, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ottenhall, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Cellulose fiber based fungal and water resistant insulation materials2017Inngår i: International Journal of the Biology, Chemistry, Physics, and Technology of Wood, E-ISSN 1437-434XArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of thermal insulation materials from sustainable, natural fibrous materials is desirable.In the present study, cellulose fiber based insulation foams made of bleached chemi thermo mechanical pulp(CTMP) have been investigated. To improve water resistance, the foams were impregnated with hydrophobic extractives from the outer bark of birch (Betula verrucosa)and dried. The surface morphology of the foams and the distribution of the deposited particles from the extractives were observed by scanning electron microscopy (SEM).The modified foams showed improved water resistance, as they did not disintegrate after immersion in water for7 days, whereas the unmodified foam did. Compared to the unmodified foam, the modified foams absorbed 50%less moisture within 24 h. The modification had no negative effects on the thermal insulation properties, fungal resistance or compressive strength of the foams. The proposed approach is simple and can be easily integrated into plants working based on the biorefinery concept.

  • 748. Ziaei Tabari, Hassan
    et al.
    Nourbakhsh, Amir
    Hosseinpourpia, Reza
    Danesh, Mohammad Amin
    Evaluation of mechanical and morphological behavior of polypropylene/wood fiber nanocomposite prepared by melts compounding2010Inngår i: International Conference on Nanotechnology and Biosensors, 28th to 30th December 2010, Hong Kong, Singapore, 2010, Vol. 2, s. 20-23Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Weak flexural properties of wood plastic composites(WPCs) limit their structural application. Recentlyinvestigation of nano particles looks promising to enhancebending properties of WPCs. In this study, the authors haveinvestigated the effect of different concentrations of nanoclay(modified montmorillonite) and coupling agent on themechanical and micro-structural properties of polypropylene/wood-fiber composites. We Bath internal mixer in certainprocessing conditions used for making the samples and then allsamples molded using injection molding for making samplesfor performing mechanical measurements. Samples preparedin four different concentration of nanoclay 0, 1, 3 and 5 wt%(total weight) and two different concentrations of maleicanhydride grafting (MAPP) 5 and 10 wt%. Mechanical resultsindicate that both flexural and impact strength of thecomposites increasing in sample containing 3% nano clay. Inother trend, Scanning Electron Microscope (SEM) imagesshow better interaction of wood fibers and polymer matrixwhen the authors added 5 wt% MAPP as coupling agent.

  • 749.
    Östman, Birgit
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Europeisk brandklassning av CLT och LVL2017Inngår i: Bygg & teknik, ISSN 0281-658X, Vol. 109, nr 6, s. 55-57Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [sv]

    Den europeiska brandklassningen av träbaserade produkter har nyligen utvidgats till att gälla även de två relativt nya träprodukterna CLT och LVL. Den täcker därmed praktiskt taget alla byggtillämpningar med träbaserade produkter. Brandklasserna har fastlagts genom ett system för förenklad europeisk brandklassificering för produkter som har ”känt och stabilt beteende vid brand”. Träprodukter är ett utmärkt exempel på sådana produkter. Brandklasserna avser både det europeiska systemet med så kallade Euroklasser A1-F och klasser för brandskyddande förmåga, så kallade K-klasser, se faktaruta.

  • 750.
    Östman, Birgit
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Fire safety in modern wooden houses: mapping of fire incidents in Sweden2017Inngår i: International fire protection, ISSN 1468-3873, nr 71, s. 46-48Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Multi-storey timber frame houses have been built in Sweden since 1994, when performance-based building regulations were introduced. The construction technology is now well established and steadily growing. Life safety protection is clearly defined in the building regulations. Now, property protection is being discussed from new perspectives.

    As a first step in better understanding, fire incidents have been mapped. The survey shows that modern apartment buildings with wooden frames have a lower rate of fire incidents than the entire stock of apartment buildings.

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