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  • 1.
    Agnihotri, Swarnima
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Johnsen, Ingvild A.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Böe, Maren S.
    NTNU Norwegian University of Science and Technology, Norway.
    Öyaas, Karin
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Moe, Størker
    NTNU Norwegian University of Science and Technology, Norway.
    Ethanol organosolv pretreatment of softwood (Picea abies) and sugarcane bagasse for biofuel and biorefinery applications2015Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 49, nr 5, s. 881-896Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ethanol derived from biomass has the potential to be a renewable transportation fuel that can replace gasoline. This work was carried out to establish an optimized ethanol organosolv pretreatment of Norway spruce (Picea abies) for bioethanol production (63 wt% EtOH, pH ~3.5 in aqueous phase, 170–240 °C, 90 min) utilizing hydrolytic enzymes in the saccharification step. To test the generality of the method, a series of ethanol organosolv pretreatments were also performed on sugarcane bagasse (50 wt% EtOH, pH ~3.5 in aqueous phase, 155–210 °C, 90–120 min). The degree of delignification increased with increasing temperature during pretreatment, and the fastest increase was observed with sugarcane bagasse. The pretreatments were carried out in a batch mode. The maximum degree of delignification of ~65 % was reached at ~235 °C for Norway spruce, while sugarcane bagasse reached ~80 % at ~210 °C. Cellulose was subjected to degradation (5–10 % points) at these temperatures. Subsequent enzymatic hydrolysis (30 FPU/g cellulose, 32 pNPGU/g cellulose, 50 °C, 48 h) of ethanol organosolv-pretreated biomass achieved complete conversion for both raw materials at the highest degrees of delignification.

  • 2.
    Dong, F.
    et al.
    RISE., Innventia.
    Olsson, Anne-Mari
    RISE., Innventia.
    Salmen, Lennart
    RISE., Innventia.
    Fibre morphological effects on mechano-sorptive creep2010Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 44, nr 3, s. 475-483Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increased creep rate of paper under load during moisture cycling conditions as compared to that at high constant humidity is a problem in the use of packaging materials. In order to investigate the influence of morphological factors of the fibres on the occurrence and magnitude of this phenomenon, i.e. the occurrence of mechano-sorptive creep, studies on wood fibres isolated from different parts of spruce wood were performed. Thus, creep properties were studied on earlywood and latewood fibres from both juvenile wood and mature wood. In general, latewood fibres showed a higher degree of mechano-sorptive creep than earlywood fibres, and mature wood showed a higher degree of mechano-sorptive creep than juvenile fibres. The difference in mechano-sorptive creep rate between different fibres was shown to be correlated to the differences in fibril angle. The smaller the fibril angle the higher was the mechano-sorptive creep ratio. It was suggested that at fibril angles approaching 45° wood fibres do not exhibit mechano-sorptive creep.

  • 3.
    Eder, Michaela
    et al.
    Max-Planck-Institute of Colloids and Interfaces, Germany.
    Arnould, Olivier
    Université Montpellier, France.
    Dunlop, John W.C.
    Max-Planck-Institute of Colloids and Interfaces, Germany.
    Hornatowska, Joanna
    RISE., Innventia.
    Salmen, Lennart
    RISE., Innventia.
    Experimental micromechanical characterisation of wood cell walls2013Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, nr 1, s. 163-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of wood and wood-based materials are strongly dependent on the properties of the fibres, that is, the cell wall properties. It is thus highly important to be able to mechanically characterise cell walls in order to understand structure-property relationships. This article gives a brief overview of the state of the art in experimental techniques to characterise the mechanical properties of wood at both the level of the single cell and that of the cell wall. Challenges, opportunities, drawbacks and limitations of single fibre tensile tests and nanoindentation are discussed with respect to the wood material properties.

  • 4.
    Guo, Juan
    et al.
    Chinese Academy of Forestry, China.
    Zhou, Haibin
    Chinese Academy of Forestry, China.
    Stevanic Srndovic, Jasna
    RISE - Research Institutes of Sweden, Bioekonomi, Bioraffinaderi och energi.
    Dong, Mengyu
    Chinese Academy of Forestry, China.
    Yu, Min
    Chinese Academy of Forestry, China.
    Salmen, Lennart
    RISE - Research Institutes of Sweden, Bioekonomi, Bioraffinaderi och energi.
    Yin, Yafang
    Chinese Academy of Forestry, China.
    Effects of ageing on the cell wall and its hygroscopicity of wood in ancient timber construction2018Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, nr 1, s. 131-147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An important traditional load bearing member in oriental ancient timber structure buildings, i.e. Huagong (flower arm), was selected to explore the alterations in cell wall components and hygroscopic properties of wood during long time ageing. This archaeological poplar (Populus spp.) wood with cal. BP 690: BP 790 was studied from the wood surface and inwards by means of imaging FTIR spectroscopy, X-ray diffraction and dynamic vapour sorption. The deterioration of the archaeological wood mainly displayed a depolymerization of glucomannan and lignin as well as a hydrolysis of the glucuronic acid of xylan and of the aromatic C–O groups in the condensed lignins or lignin–carbohydrate complexes. Furthermore, the degradation promoted the rearrangement of the cellulose molecules in adjacent microfibrils. The cellulose crystallites in the archaeological wood were therefore packed more tightly and had larger diameter. The structural alterations of wood cell wall components and a decrease in crystallinity contributed to an increase in the number of moisture bonding sites and led to an increase in both the equilibrium moisture content of the archaeological wood in the entire RH range as well as an increase in hysteresis.

  • 5.
    Hegnar, Olav
    et al.
    Norwegian Institute for Bioeconomy Research, Norway.
    Goodell, Barry
    University of Massachusetts, US.
    Felby, Claus
    University of Copenhagen, Denmark.
    Johansson, Lars
    RISE - Research Institutes of Sweden, Bioekonomi, PFI.
    Labbé, Nicole
    University of Tennessee, US.
    Kim, Keonhee
    University of Tennessee, US.
    Eijsink, Vincent
    Norwegian University of Life Sciences, Norway.
    Alfredsen, Gry
    Norwegian Institute for Bioeconomy Research, Norway; Norwegian University of Life Sciences, Norway.
    Várnai, Aniko
    Norwegian University of Life Sciences, Norway.
    Challenges and opportunities in mimicking non-enzymatic brown-rot decay mechanisms for pretreatment of Norway spruce2019Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 53, nr 2, s. 291-311Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The recalcitrance bottleneck of lignocellulosic materials presents a major challenge for biorefineries, including second-generation biofuel production. Because of their abundance in the northern hemisphere, softwoods, such as Norway spruce, are of major interest as a potential feedstock for biorefineries. In nature, softwoods are primarily degraded by basidiomycetous fungi causing brown rot. These fungi employ a non-enzymatic oxidative system to depolymerize wood cell wall components prior to depolymerization by a limited set of hydrolytic and oxidative enzymes. Here, it is shown that Norway spruce pretreated with two species of brown-rot fungi yielded more than 250% increase in glucose release when treated with a commercial enzyme cocktail and that there is a good correlation between mass loss and the degree of digestibility. A series of experiments was performed aimed at mimicking the brown-rot pretreatment, using a modified version of the Fenton reaction. A small increase in digestibility after pretreatment was shown where the aim was to generate reactive oxygen species within the wood cell wall matrix. Further experiments were performed to assess the possibility of performing pretreatment and saccharification in a single system, and the results indicated the need for a complete separation of oxidative pretreatment and saccharification. A more severe pretreatment was also completed, which interestingly did not yield a more digestible material. It was concluded that a biomimicking approach to pretreatment of softwoods using brown-rot fungal mechanisms is possible, but that there are additional factors of the system that need to be known and optimized before serious advances can be made to compete with already existing pretreatment methods.

  • 6.
    Kvist, Patric
    et al.
    Chalmers University of Technology, Sweden.
    Schuster, Erich
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Rasmuson, Anders
    Chalmers University of Technology, Sweden.
    Using fluorescent probes and FRAP to investigate macromolecule diffusion in steam-exploded wood2018Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, nr 5, s. 1395-1410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diffusion of fluorescently labeled dextran of varying molecular weight in wood pretreated by steam explosion was studied with a confocal microscope. The steam explosion experiments were conducted at relatively mild conditions relevant for materials biorefinery at a pressure of 14 bars for 10 min. The method of fluorescence recovery after photobleaching (FRAP) was used to perform diffusion measurements locally in the wood microstructure. It was found that the FRAP methodology can be used to observe differences in the diffusion coefficient based on localization in the microstructure, i.e., earlywood, latewood, and cell wall. Microscopic changes due to steam explosion were seen to increase diffusion of the smaller 3-kDa dextran diffusion probe in the earlywood, while the latewood structure was not affected in any significant way. Macroscopic changes to the structure in the form of ruptures due to the steam explosion pretreatment were observed to increase the rate of diffusion for the larger 40-kDa dextran probe.

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  • 7.
    Källander, Björn
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, AB Trätek.
    Climate control in vacuum dryers for convective heat transfer. Partt 1: Demands on climate control2002Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 36, nr 6, s. 477-486Artikel i tidskrift (Övrigt vetenskapligt)
  • 8.
    Laine, Kristiina
    et al.
    KTH Royal Institute of Technology, Sweden.
    Segerholm, Kristoffer
    RISE., SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Wålinder, Magnus
    KTH Royal Institute of Technology, Sweden.
    Rautkari, Lauri
    Aalto University, Finland.
    Hughes, Mark
    Aalto University, Finland.
    Wood densification and thermal modification: hardness, set-recovery and micromorphology2016Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 5, s. 883-894Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Meyer-Veltrup, Linda
    et al.
    Leibniz University, Germany.
    Brischke, Christian
    Leibniz University, Germany.
    Alfredsen, Gry
    NIBIO The Norwegian Institute of Bioeconomy Research, Norway.
    Humar, Miha
    University of Ljubljana, Slovenia.
    Flæte, Per-Otto
    Norwegian Institute of Wood Technology, Norway.
    Isaksson, Tord
    Lund University, Sweden.
    Brelid, Pia L.
    RISE - Research Institutes of Sweden, Bioekonomi, Biobaserade material.
    Westin, Mats
    RISE - Research Institutes of Sweden, Bioekonomi, Biobaserade material.
    Jermer, Jöran
    RISE - Research Institutes of Sweden, Bioekonomi, Biobaserade material.
    The combined effect of wetting ability and durability on outdoor performance of wood: development and verification of a new prediction approach2017Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 51, nr 3, s. 615-637Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Comprehensive approaches to predict performance of wood products are requested by international standards, and the first attempts have been made in the frame of European research projects. However, there is still an imminent need for a methodology to implement the durability and moisture performance of wood in an engineering design method and performance classification system. The aim of this study was therefore to establish an approach to predict service life of wood above ground taking into account the combined effect of wetting ability and durability data. A comprehensive data set was obtained from laboratory durability tests and still ongoing field trials in Norway, Germany and Sweden. In addition, four different wetting ability tests were performed with the same material. Based on a dose–response concept, decay rates for specimens exposed above ground were predicted implementing various indicating factors. A model was developed and optimised taking into account the resistance of wood against soft, white and brown rot as well as relevant types of water uptake and release. Decay rates from above-ground field tests at different test sites in Norway were predicted with the model. In a second step, the model was validated using data from laboratory and field tests performed in Germany and Sweden. The model was found to be fairly reliable, and it has the advantage to get implemented into existing engineering design guidelines. The approach at hand might furthermore be used for implementing wetting ability data into performance classification as requested by European standardisation bodies.

  • 10.
    Nussbaum, Ralph
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    Oxidative activation of wood surfaces by flame treatment1993Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 27, s. 183-193Artikel i tidskrift (Refereegranskat)
  • 11. Olsson, Anders
    et al.
    Oscarsson, Jan
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Johansson, Marie
    Källsner, Bo
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Prediction of timber bending strength on basis of bending stiffness and material homogeneity assessed from dynamic excitation2012Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, nr 4, s. 667-683Artikel i tidskrift (Refereegranskat)
  • 12.
    Olsson, Anders
    et al.
    Linnaeus University, Sweden.
    Oscarsson, Jan
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Serrano, Erik
    Linnaeus University, Sweden.
    Källsner, Bo
    Linnaeus University, Sweden.
    Johansson, Marie
    Linnaeus University, Sweden.
    Enquist, Bertil
    Linnaeus University, Sweden.
    Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation2013Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 71, nr 3, s. 319-333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mmÂ3;, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.

  • 13.
    Olsson, Anne M.
    et al.
    RISE., Innventia.
    Salmen, Lennart
    RISE., Innventia.
    Mechano-sorptive creep in pulp fibres and paper2014Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 48, nr 3, s. 569-580Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The factors affecting mechano-sorptive creep of wood and paper have been investigated for a long time. It has also been argued that single wood fibres do not exhibit mechano-sorptive creep and that the reasons for the accelerated creep under moisture cycling conditions instead are related to the bonds between the fibres. In order to examine the relevance of this argument, measurements on single pulp fibres of different composition were performed in tension, and the mechano-sorptive creep was compared to that of papers made from the same source of pulp fibres. All fibres tested were found to exhibit an increased creep rate during moisture cycling as compared to constant humidity conditions. Thus, pulp fibres show mechano-sorptive creep and in this sense behave similar to solid wood or paper products made thereof. A linear relation between the creep strain rate during cyclic humidity and the creep strain rate at a constant humidity was also noted for both fibres and paper. This relation was not affected by changes in hemicelluloses content or composition, neither for fibres nor for papers made of these fibres. However, in all cases, papers showed a much higher mechano-sorptive creep than the corresponding fibres they were made of.

  • 14.
    Oscarsson, Jan
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Olsson, Anders
    Enquist, Bertil
    Strain fields around knots in Norway spruce specimens exposed to tensile forces2012Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, nr 4, s. 593-610Artikel i tidskrift (Refereegranskat)
  • 15.
    Pahlberg, Tobias
    et al.
    Luleå University of Technology, Sweden.
    Johansson, Erik
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Förädling och processer (TRf). Luleå University of Technology, Sweden.
    Hagman, Olle
    Luleå University of Technology, Sweden.
    Thurley, Matthew
    Luleå University of Technology, Sweden.
    Wood fingerprint recognition using knot neighborhood K-plet descriptors2015Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 49, nr 1, s. 7-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the wood industry, there is a wish to recognize and track wood products through production chains. Traceability would facilitate improved process control and extraction of quality measures of various production steps. In this paper, a novel wood surface recognition system that uses scale and rotationally invariant feature descriptors called K-plets is described and evaluated. The idea behind these descriptors is to use information of how knots are positioned in relation to each other. The performance and robustness of the proposed system were tested on 212 wood panel images with varying levels of normally distributed errors applied to the knot positions. The results showed that the proposed method is able to successfully identify 99–100 % of all panel images with knot positional error levels that can be expected in practical applications.

  • 16.
    Peng, Hui
    et al.
    Nanjing Forestry University, China; Hunan Collaborative Innovation Center for Effective Utilizing of Wood and Bamboo Resources, China.
    Salmen, Lennart
    RISE Research Institutes of Sweden, Bioekonomi och hälsa.
    Jiang, Jiali
    Hunan Collaborative Innovation Center for Effective Utilizing of Wood and Bamboo Resources, China.
    Lu, Jianxiong
    Nanjing Forestry University, China; Hunan Collaborative Innovation Center for Effective Utilizing of Wood and Bamboo Resources, China.
    Creep properties of compression wood fibers2020Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 54, s. 1497-1510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To achieve efficient utilization of compression wood (CW), a deeper insight into the creep behavior of CW is necessary. In particular, the involvement of lignin for the creep behavior of CW needs to be better understood. In the present paper, wood fibers and slices from CW and normal wood were studied at both high constant humidity and cyclic 30–80% RH conditions. The micromechanical deformation explored by FTIR confirmed that in CW, lignin participated in the stress transfer during creep measurements. For all types of materials, the creep strain rate at constant and cyclic humidity conditions was linearly related to the applied load level. For single CW fibers, the creep rates were higher at a given load for native CW fibers compared to holocellulose CW fibers, due to the lower relative cellulose content. The CW fibers, with a microfibril angle of around 45°, were found to exhibit a greater creep rate during moisture cycling as compared to the higher but constant humidity level, i.e., a mechano-sorptive behavior. However, the mechano-sorptive effect, i.e., the ratio between the creep rates at constant and cyclic humidity, was only slightly higher for the CW holocellulose fibers as compared to the native CW fibers, indicating that the lignin most probably does not contribute to the mechano-sorptive effect. 

  • 17.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad. Technical University of Munich, Germany.
    Kölle, Martina
    Technical University of Munich, Germany.
    Brischke, Christian
    Leibniz University Hannover, Germany.
    Richter, Klaus
    Technical University of Munich, Germany.
    Effects of thermal modification on Postia placenta wood degradation dynamics: measurements of mass loss, structural integrity and gene expression2016Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 2, s. 385-397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanism by which modified wood resists decay has long been discussed, but is still not fully understood. A better understanding of decay resistance mechanisms could improve wood protection processes and product properties. In this study, the dynamics of brown rot decay in thermally modified wood was examined through measurements of mass loss, strength loss and gene expression. Close monitoring of mass loss over 120 days in thermally modified wood exposed to Postia placenta showed a delay in the onset of degradation compared to untreated wood, and once the degradation had started, the rate was lower. Thermally modified wood did not inhibit expression of wood degradation-related genes before mass loss and was similar to that in untreated wood once mass loss could be detected. Comparing gene expression as well as strength loss at the same stage of decay rather than at the same time after exposure showed smaller differences in decay patterns between thermally modified and untreated wood than previous results indicate. It is concluded that the key to understanding degradation resistance in thermally modified wood is to compare the decay patterns in thermally modified wood and untreated wood before mass loss occurs.

  • 18.
    Salmen, Lennart
    et al.
    RISE., Innventia.
    Olsson, Anne-Mari
    RISE., Innventia.
    Physical properties of cellulosic materials related to moisture changes2016Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 1, s. 81-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Moisture affects the mechanical properties of paper to a high degree. Moreover, the creep properties of paper may be highly affected while the relative humidity is changing, exhibiting mechano-sorptive creep. The reasons for the great sensitivity to moisture changes of papers are not fully explained. In this study, thin papers were examined during sorption processes and the moisture content within the paper, paper length and dynamic elastic modulus during RH changes were measured. It is demonstrated that the dimensional changes of the paper exactly reflected the changes in moisture content within the sample. During both absorption and desorption, the elastic modulus changed so that it was lower than the equilibrium value corresponding to its moisture content. This was especially evident during absorption where the modulus dropped below the equilibrium value at the end RH, i.e. the value was approached from below. The modulus drop was highly related to RH changes made at higher RH and could possibly be related to the softening of carbohydrates.

  • 19.
    Sandberg, Karin
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Salin, Jarl-Gunnar
    Liquid water absorption in dried Norway spruce timber measured with CT scanning and viewed as a percolation process2012Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, nr 1-3, s. 207-219Artikel i tidskrift (Refereegranskat)
  • 20.
    Sedighi Moghaddam, Maziar
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Claesson, Per
    RISE., SP – Sveriges Tekniska Forskningsinstitut. KTH Royal Institute of Technology, Sweden.
    Wålinder, Magnus E.P.
    KTH Royal Institute of Technology, Sweden.
    Swerin, Agne
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor. KTH Royal Institute of Technology, Sweden.
    Wettability and liquid sorption of wood investigated by Wilhelmy plate method2014Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 48, nr 1, s. 161-176Artikel i tidskrift (Refereegranskat)
    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.

  • 21.
    Östman, Birgit
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek..
    Wood tensile strength at temperatures and moisture contents simulating fire conditions1985Ingår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 19, nr 2, s. 103-116Artikel i tidskrift (Refereegranskat)
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