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  • 1. Ahmed, Sheikh Ali
    et al.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 251-258Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in uneven distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 2.
    Bjurhager, Ingela
    et al.
    Kungliga tekniska högskolan, KTH.
    Ljungdahl, Jonas
    Kungliga tekniska högskolan, KTH.
    Wallström, Lennart
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gamstedt, Kristofer
    Kungliga tekniska högskolan, KTH.
    Berglund, Lars A
    Kungliga tekniska högskolan, KTH.
    Towards improved understanding of PEG-impregnated waterlogged archaeological wood: a model study on recent oak2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 2, p. 243-250Article in journal (Refereed)
    Abstract [en]

    To prevent deformation and cracking of waterlogged archaeological wood, polyethylene glycol (PEG) as a bulk impregnation agent is commonly applied. PEG maintains the wood in a swollen state during drying. However, swelling of wood can reduce its mechanical properties. In this study, the cellular structure of oak and cell wall swelling was characterized by scanning electron microscopy (SEM) of transverse cross-sections, and the microfibril angle of oak fibers was determined by wide angle X-ray scattering (WAXS). Samples of recent European oak (Quercus robur L) impregnated with PEG (molecular weight of 600) were tested in axial tension and radial compression. Mechanical tests showed that axial tensile modulus and strength were only slightly affected by PEG, whereas radial compressive modulus and yield strength were reduced by up to 50%. This behavior can be explained by the microstructure and deformation mechanisms of the material. Microfibril angles in tensile test samples were close to zero. This implies tensile loading of cellulose microfibrils within the fiber cell walls without almost any shear in the adjacent amorphous matrix. These results are important because they can help separate the impact of PEG on mechanical properties from that of chemical degradation in archaeological artifacts, which display only small to moderate biological degradation.

  • 3.
    Blomberg, Jonas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Persson, Bengt
    Dalarna University, Borlänge.
    Bexell, Ulf
    Dalarna University, Borlänge.
    Effects of semi-isostatic densification on anatomy and cell-shape recovery on soaking2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 1, p. 322-331Article in journal (Refereed)
    Abstract [en]

    Images obtained by scanning electron microscopy (SEM) helped to clarify the question as to how anatomy influences the deformation on compression and the spring-back of densified wood on water soaking. Transverse sections of Norway spruce (Picea abies), Scots pine (Pinus sylvestris), black alder (Alnus glutinosa), Swedish aspen (Populus tremula), European birch (Betula pubescens), European beech (Fagus sylvatica) and pedunculate oak (Quercus robur) were studied. Wood is reinforced with rays in the radial direction and with dense latewood in the tangential direction. When strained radially, rays buckle or tilt tangentially. Softwoods were mainly compressed radially, owing to low number of rays and since latewood is much denser than earlywood. The diffuse-porous hardwoods with low density variation between latewood and earlywood were mainly deformed tangentially, except birch, which has high density at the annual ring border and is mainly compressed radially. The ringporous hardwoods were relatively equally deformed in the radial and tangential directions because of the high number of rays and high latewood density. Moisture-induced springback (shape recovery) was proportional to the degree of compression. Rays remained deformed, which also influenced the surrounding wood. Longitudinal wood cells almost resumed their original shape. Wood with low density and a low degree of compression showed the highest structural recovery. Shearing deformation was particularly pronounced and permanent in woods with high strength anisotropy. Thin-walled and sheared cells, such as earlywood in softwood, tended to crack on compression. Cracks usually stopped at the middle lamella and had a lesser influence on strength properties than for lumen-to-lumen cracks. Copyright

  • 4.
    Elustondo, Diego
    et al.
    Department of Wood Science, University of British Columbia, Vancouver.
    Avrimidis, Stavros H.
    Department of Wood Science, University of British Columbia, Vancouver.
    Oliveira, Luiz C De S
    Forintek Canada Corporation, Western Laboratory, Vancouver, BC.
    Estimation of green moisture content distribution in hemfir timber by stochastic simulation2004In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 58, no 4, p. 413-417Article in journal (Refereed)
    Abstract [en]

    This paper describes an improved stochastic model designed to simulate systems, such as green timbers, that cannot be analyzed as a unit but as a collection of a large number of similar components. The stochastic model provides a piecewise green moisture content frequency distribution curve by using nondestructive measurements such as of timber weight. A new, relatively simple two-parameter function was designed to describe the log-normal moisture concentration distribution above the fiber saturation point, and the parameters of this function were determined by fitting the experimental timber weights with the results of the stochastic model. The simulated green moisture content distributions showed good agreement with the experimental data for Pacific coast hemlock (hemfir) timbers, thus providing a piece of information that is indispensable for applying stochastic simulation to industrial drying of timbers.

  • 5.
    Elustondo, Diego
    et al.
    Department of Wood Science, University of British Columbia, Vancouver.
    Koumoutsakos, Anastasios D.
    Department of Wood Science, University of British Columbia, Vancouver.
    Avramidis, Stavros H.
    Department of Wood Science, University of British Columbia, Vancouver.
    Non-deterministic description of wood radio frequency vacuum drying2003In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 57, no 1, p. 88-94Article in journal (Refereed)
    Abstract [en]

    A numerical method is proposed to predict the stochastic dispersion of data that unavoidably occurs in a real drying process. The method is based on the use of discrete frequency distribution curves to predict a random variation on some parameters of the process and is applied to the case of radio frequency vacuum (RFV) drying of wood. Experimental data of RFV drying of western hemlock timbers were used to obtain the numeric values of the stochastic parameters and their standard deviation. A mathematical model was designed to simulate the final moisture content dispersion on hypothetical examples. Results were quantified using three indices: average, range and standard deviation.

  • 6. Elustondo, Diego
    et al.
    Oliveira, Luiz C De S
    FPInnovations, Canada, Pointe-Claire.
    Lister, Peter
    FPInnovations, Canada, Pointe-Claire.
    Temperature drop sensor for monitoring kiln drying of lumber2009In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 3, p. 334-339Article in journal (Refereed)
    Abstract [en]

    The main objective of this study was to test a new sensor based on the temperature drop across the load (TDAL). The TDAL sensor was designed to determine the transition point between wet and dry wood without any specific information about the drying process. When additional information is available, the TDAL sensor can also be used to monitor drying rate and estimate the drying end-point. In this study, three potential applications of TDAL sensor for lumber drying were explored, namely, to monitor drying rate, to detect the transition point between wet and dry wood, and for determination of drying end-point after calibration. For the first application, it was demonstrated that the transition point between wet and dry wood coincides with the time at which the TDAL decreases with time at a constant logarithmic slope. For the second application, the TDAL sensor was calibrated with nine experimental drying runs, and the end-points determined with the calibrated TDAL sensor did not show a significant difference with the end-points determined by the in-kiln MC meter. Finally, the TDAL sensor was used to monitor drying rate during drying

  • 7. Elustondo, Diego
    et al.
    Oliveira, Luiz C De S
    FPInnovations, Canada, Pointe-Claire.
    Lister, Peter
    Forintek Canada Corporation, Ottawa.
    Temperature-drop sensor for determination of drying curves in conventional lumber drying2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 2, p. 196-200Article in journal (Refereed)
    Abstract [en]

    Conventional lumber drying is carried out by forcing hot air to flow across a pile of lumber layers separated by wood strips. The airflow provides the heat required to warm up the lumber and produce the moisture evaporation and, in theory, the difference in temperature at each side of the load can be used to estimate the evaporation rate. The main problem with this approach is that typical temperature sensors that are installed in conventional kilns are not accurate enough to measure the temperature drop across the load during periods of low evaporation. In this paper, a new sensor to measure the temperature drop across the load is proposed and tested in three experimental drying runs of 2" X 6" spruce-pine lumber. The results demonstrate that after calibration, the temperature drop across the load can be used to determine drying curves in conventional lumber drying. In the particular case of this study, calibration was performed by multiplying the experimental temperature drop across the load by a constant factor, which was adjusted by identifying the correction factor that best simulated the experimental green moisture content of the three lumber charges.

  • 8.
    Hafrén, Jonas
    et al.
    Swedish Pulp and Paper Research Institute, Stockholm.
    Fujino, Takeshi
    Wood Research Institute, Kyoto University,.
    Itoh, Takao
    Wood Research Institute, Kyoto University,.
    Westermark, Ulla
    Terashima, Noritsugu
    Swedish Pulp and Paper Research Institute, Stockholm.
    Ultrastructural changes in the compound middle lamella of Pinus thunbergii during lignification and lignin removal2000In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, no 3, p. 234-240Article in journal (Refereed)
    Abstract [en]

    The structure of the middle lamella in Pinus thunbergii has been studied by the rapid-freeze deep-etching (RFDE) technique in combination with transmission electron microscopy (TEM). The ultrastructure of the compound middle lamella was studied in the early phases of the development of woody tissue in the cambial and differentiating xylem, before the heavy incrustation with lignin had occurred. Lignified middle lamella in the xylem was studied both directly and after delignification. It was found that the structure of the unlignified middle lamella in the cambium/developing xylem consists of a fine irregular network probably containing pectin and hemicellulose. As a result of lignin incrustation, the middle lamella becomes increasingly dense and the surface structure of the fully lignified middle lamella appeared to be compact and partly covered with globular structures. After delignification of the lignified middle lamella a thin network with a different structure was revealed. This network probably mainly consists of hemicellulose. No microfibrils of the type that occurs in the primary and secondary walls were found in the middle lamella.

  • 9.
    Hafrén, Jonas
    et al.
    STFI, Stockholm.
    Westermark, Ulla
    Lennholm, Helena
    Royal Institute of Technology.
    Terashima, Noritsugu
    STFI, Stockholm.
    Formation of 13C-enriched cell-wall DHP using isolated soft xylem from Picea abies2002In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 56, no 6, p. 585-591Article in journal (Refereed)
    Abstract [en]

    Cell-wall dehydrogenation polymers (CW-DHP) were prepared by incubating a mixture of soft xylem (differentiating xylem) from Picea abies, coniferin 13C-enriched at the side-chain β-carbon and unenriched coniferin, both with and without the addition of β-glucosidase and glucose oxidase, which causes an in situ polymerisation of the coniferyl alcohol in the cell wall. From difference solid state 13C-NMR spectra between 13C-enriched CW-DHP and unenriched CW-DHP, the bond frequencies involving specifically 13C-enriched carbon can be quantitatively determined. The sub-structures in CW-DHP prepared without the addition of β-glucosidase and glucose oxidase showed more similarity to protolignin than CW-DHP prepared with the addition of extraneous enzymes. The CW-DHP obtained without the addition of enzymes contained 36% β-O-4-derived sub-structures, 44% combined β-β, β-5 and β-1 sub-structures and 20% coniferyl alcohol/coniferaldehyd end groups. After acetone/water extraction of the CW-DHP, the content of β-β, β-5 and β-1 structures decreased by 4%, and the β-O-4 dominating peak increased by 4%. The 13C-enriched CW-DHP material can be used to study lignin reactions in a solid wood matrix, and is also a powerful system for detailed studies on in vivo lignification mechanisms and the effects on lignification conditions on lignin structure

  • 10.
    Jenrkvist, L.O.
    et al.
    Luleå tekniska universitet.
    Thuvander, Fredrik
    Luleå tekniska universitet.
    Experimental determination of stiffness variation across growth rings in Picea abies2001In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 55, no 3, p. 309-317Article in journal (Refereed)
    Abstract [en]

    The radial and tangential deformations in a single growth ring of Norway spruce, which was subjected to moderate tensile loading in its radial direction, were measured by use of digital speckle photography. From the measured displacement field, the transverse coefficients of elasticity ER, ET, GRT and vTR we determined with respect to radial position in the growth ring. As a result of the abrupt change in stiffness from latewood to earlywood in the growth ring, it was possible to establish all four coefficients solely from the radial tension test. The elastic modulus ET was found to be a factor 15 larger in latewood than in early wood, whereas the corresponding variation for ER was merely a factor 3. The measured variations were in reasonable agreement with predictions from simple two-dimensional honeycomb models of the growth ring cellular structure. The average elastic moduli of the growth ring were found to be twice as large as ER and ET measured in conventional tests on macroscale specimens, whereas the reverse was true for the shear modulus. An explanation to these differences is sought by analysing the loading conditions and deformation behaviour of macroscale specimens used in transverse stiffness testing of wood.

  • 11.
    Johansson, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Influences of drying on internal checking of spruce (Picea abies L.) heat-treated at 212°C2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 5, p. 558-560Article in journal (Refereed)
  • 12.
    Kutnar, Andreja
    et al.
    University of Primorska.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Haller, Peer
    TU Dresden.
    Compressed and moulded wood from processing to products: COST action FP0904 2010–2014: Thermo-hydro-mechanical wood behaviour and processing2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 9, p. 885-897Article in journal (Refereed)
    Abstract [en]

    This paper presents the state of the art of different wood densification processes as one emerging process technology. The main principles for the processes are discussed, such as bulk and surface densification, bending, moulding of shells and tubes, as well as methods for reducing the shape memory effect of densified wood. The main challenges are in the field of scaling up to industrial applications. To provide a better understanding with this regard, some relevant scientific results are presented. Furthermore, the discussion considers the contribution of thermo-hydro and thermo-hydro-mechanical processes to a sustainable and low-carbon economy

  • 13.
    Neyses, Benedikt
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The effect of ionic liquid and superbase pre-treatment on the spring-back, set-recovery and Brinell hardness of surface-densified Scots pineIn: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed)
    Abstract [en]

    Compressing the surface of sawn timber results in a substantial increase in hardness, and this opens up new market opportunities of using low-density timber species as the raw material for high-value wood products. Unfortunately, widespread commercialisation is hindered by the lack of an industrially viable surface densification process, the major obstacle being the set- recovery of the densified wood cells upon exposure to moisture. Our hypothesis is that partial dissolution of the crystalline cellulose during densification will largely prevent the set- recovery of densified wood. We therefore evaluated the effect of ionic liquid or organic superbase pre-treatment on the elastic spring-back, set-recovery and Brinell hardness of surface-densified wood. Specimens of Scots pine were treated with solutions of ionic liquids or superbases, and then densified in a hot press at temperatures between 200°C and 270°C. The set-recovery was reduced from 90% for the control group to only about 10% for the treated materials. The treated and densified specimens exhibited a higher Brinell hardness than their untreated and densified counterparts. The method presented in this study is a precursor to the development of a continuous densification process adapted for an open system. Further studies are needed to understand the underlying mechanisms of the pre- treatment.

  • 14.
    Nordstierna, Lars
    et al.
    Industrial NMR Centre and Division of Physical Chemistry, Department of Chemistry, Royal Institute of Technology, Stockholm.
    Lande, Stig
    Kebony ASA, Porsgrunn.
    Westin, Mats
    SP Technical Research Institute of Sweden, Borås.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Furó, István
    Industrial NMR Centre and Division of Physical Chemistry, Department of Chemistry, Royal Institute of Technology, Stockholm.
    Towards novel wood-based materials: chemical bonds between lignin-like model molecules and poly(furfuryl alcohol) studied by NMR2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 6, p. 709-713Article in journal (Refereed)
    Abstract [en]

    Wood modification with furfuryl alcohol is a non-toxic alternative to conventional preservation treatments. A process in which furfuryl alcohol polymerises in situ was previously proposed for chemical modification of wood. In the present work, liquid model systems were investigated using compounds that resemble repeating units of lignin to verify whether chemical bonds form between the furfuryl alcohol polymer and wood. Using different NMR spectroscopic techniques we confirmed that these model compounds do form covalent bonds with the polymerising polymer. The results indicate that the furan polymer grafts to lignin, supporting observations in similar studies performed with genuine wood materials.

  • 15.
    Nylander, Filip
    et al.
    Chalmers University of Technology, Department of Chemistry and Chemical Enginering.
    Sunner, Hampus
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Olsson, Lisbeth
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Westman, Gunnar
    Chalmers University of Technology, Department of Chemistry and Chemical Enginering.
    Synthesis and enzymatic hydrolysis of a diaryl benzyl ester model of a lignin-carbohydrate complex (LCC)2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 5, p. 385-391Article in journal (Refereed)
    Abstract [en]

    Specific degradation of the bonds between lignin and carbohydrates is an important step towards separating individual lignocellulosic biopolymers for sustainable production of materials and chemicals. One of the most established covalent lignin-carbohydrate (LC) interactions is the ester bond between the α- or γ-hydroxyl group of a lignin phenylpropane unit and a glucuronic acid side chain of xylan. In this work, a model of the LC benzyl ester bond was synthesized in a one-pot reaction from a β-O-4 lignin unit and d-glucuronic acid, both from commercial sources. The resulting lignin-carbohydrate complex (LCC) model was unstable in aqueous solution. However, at pH 4, the rate of spontaneous hydrolysis was sufficiently low to allow for enzymatic splitting experiments. The enzymatic hydrolysis of the LC benzyl ester bond of the LCC model was demonstrated by means of the glucuronoyl esterase StGE2 from Sporotrichum thermophile, which showed a preference for erythro forms of the LCC model

  • 16.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Interaction between wood and synthetic polymers1995In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 49, no 3, p. 249-254Article in journal (Refereed)
    Abstract [en]

    The properties of wood composites consisting of low density polyethylene (LDPE) and wood flour (WF) were studied. In an attempt to improve the interfacial adhesion between hydrophobic LDPE matrix and the hydrophilic WF filler, a styrene-butadiene-styrene (SBS) copolymer was added as a compatibilizer. The interaction between LDPE and wood was investigated for PE/WF- and PE/WF/SBS-composites. The experimental measurements were conducted by conventional mechanical testing and Scanning Electron Microscopy (SEM). The interaction between polystyrene and wood in PS/WF composites was also studied by SEM and by Dynamic Mechanical Thermal Analysis (DMTA). PE/WF/SBS composites showed higher maximum tensile stress and strain at failure than the composites without SBS. SEM fractography confirmed better adhesion between the PE matrix and wood particles when SBS was present. DMTA measurements confirmed molecular interaction between PS and wood, the glass transition (Tg) peak of PS moved towards the Tg peak of cellulose

  • 17.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindberg, Henrik
    Luleå tekniska universitet.
    The influence of a SBS compatibilizer in polyethylene-wood flour composites1998In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 52, no 6, p. 661-666Article in journal (Refereed)
    Abstract [en]

    A styrene-butadiene-styrene (SBS) block copolymer has been used as a compatibilizer in a low density polyethylene/wood flour (LDPE/WF) composite system. Dynamic mechanical thermal analysis (DMTA) and a transmission electron microscopy (TEM) were used to investigate the interfacial properties in the composites. A high resolution study of the composite microstructure, and especially of the interfaces between the wood particles and LDPE matrix, indicated that the SBS compatibilizer was located at the interface region between the wood particles and LDPE matrix and partially covered the wood particle surfaces. The SBS was also found in the LDPE matnx. The unsaturated part of the copolymer was stained with osmium(VIII)tetraoxide (OsO4) to enhance contrast and to allow it to be detectable in TEM. Dynamic mechanical measurements confirmed interaction between polystyrene (PS) and wood in the PE/PS/WF system. The tan d peak of PS was shifted about 10°C to a higher temperature and also broadened when wood flour was added in the LDPE/PS blend.

  • 18. Pantze, Anna
    et al.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    Esterification of carboxylic acids on cellulosic material: solid state reactions2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 2, p. 136-141Article in journal (Refereed)
    Abstract [en]

    In the present work, the formation of ester linkages in cellulosic materials during drying and heating was addressed. The results indicated that direct ester formation, without anhydride intermediate, occurs between carboxylic acids of suitable structure and cellulosic hydroxyls at 180 degrees C, even after reaction times as short as 5 min. The 2(R)-hydroxybutyric acid is most effective in ester formation, followed by 2-ketobutyric acid and 3-hydroxybutyric acid. Hexanoic acid is less effective and veratric acid produces no esters at all. At lower temperatures, 2-ketobutyric acid is the most reactive compound. One conclusion is that a hydroxyl or keto group in alpha position of the carboxylic acids favours ester formation. Another finding is that three pyrrolidine structures are produced after esterification and aminolysis of 2-ketobutyric acid. One of the structures indicates that 2-ketobutyric acid is reactive in two positions and could therefore be a potential cross-linker. A critical parameter for ester formation is pH, and the results indicate that pH < 2 strongly favours esterification, whereas almost no esters are produced at pH > 5-6. All experiments were performed in a solid-state model system (on cellulosic filter paper) with low moisture content. Esterification of five carboxylic acids was studied. Samples were heated constantly at 180 degrees C for 5 min or gradually from 22 degrees C to 180 degrees C over periods ranging from 5 to 45 min. Quantitative analysis of ester formation between the monocarboxylic acids and the hydroxyl groups of cellulose was performed by means of aminolysis and gas chromatography.

  • 19.
    Parkås, Jim
    et al.
    Chalmers University of Technology, Department of Forest Products and Chemical Engineering.
    Paulsson, Magnus
    Chalmers University of Technology, Department of Forest Products and Chemical Engineering.
    Westermark, Ulla
    Terashima, Noritsugu
    Swedish Pulp and Paper Research Institute, Stockholm.
    Solid state NMR analysis of β-13C-enriched lignocellulosic material during light-induced yellowing2001In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 55, no 3, p. 276-282Article in journal (Refereed)
    Abstract [en]

    Photoyellowing of lignocellulosic materials has been studied with a new technique based on solid state 13C-NMR analysis of 13C-enriched DHP in cell wall tissue. The selectively 13C-enriched cell wall-dehydrogenation polymer (CW-DHP) was prepared directly on differentiating xylem from spruce (Picea abies) at pH 6.0 by administering β-13C-enriched coniferin in an enzymatic system consisting of glucose oxidase, β-glucosidase, and the naturally occurring water-insoluble enzymes remaining in the cell wall. The bonding pattern of the formed CW-DHP was found to be: 42% β-β, β-5, and β-1 substructures; 36% β-O-4 derived substructures; and 22% coniferyl alcohol and coniferaldehyde end-groups. The 13C-NMR analysis of unirradiated and irradiated tissue revealed a decrease in the relative amount of coniferaldehyde and/or coniferyl alcohol end-groups during irradiation. Prolonged irradiation also introduced new signals centered at 37, 70, and 102 ppm. The results indicate that the present technique, with the formation of DHP in a naturally lignifying carbohydrate environment, has the potential of being a valuable tool for the study of structural changes of lignin during light-induced yellowing.

  • 20.
    Sandberg, Dick
    KTH, Royal Institute of Technology, Division of Wood Technology and Processing.
    Weathering of radial and tangential wood surfaces of pine and spruce.1999In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 53, no 4, p. 355-364Article in journal (Refereed)
  • 21.
    Terashima, Noritsugu
    et al.
    2-610 Uedayama, Tenpaku, Nagoya.
    Akiyama, Takuya
    USDA ARS, US Dairy Forage Res Ctr, Madison, WI.
    Ralph, Sally
    Forest Products Laboratory, Madison, WI.
    Evtuguin, Dmitry
    Universidade de Aveiro.
    Neto, Carlos Pascoal
    Universidade de Aveiro.
    Parkas, Jim
    Chalmers University of Technology, Department of Forest Products and Chemical Engineering.
    Paulsson, Magnus
    Chalmers University of Technology.
    Westermark, Ulla
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ralph, John
    University of Wisconsin.
    2D-NMR (HSQC) difference spectra between specifically C-13-enriched and unenriched protolignin of Ginkgo biloba obtained in the solution state of whole cell wall material2009In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 4, p. 379-384Article in journal (Refereed)
    Abstract [en]

    In the structural analysis of lignins by 13C-NMR, signal overlap limits definitive assignment and accurate intensity measurement. Selective labeling by 13C-enrichment of a specific carbon in lignin enhances its signal intensity in the spectrum. Further enhancement of the specifically labeled carbons can be realized via difference spectra created from the enriched and unenriched samples. Difference 2D 13C-1H correlation (HSQC) NMR spectra, derived from the spectra of specifically 13C-enriched lignin model polymers (so-called dehydrogenation polymers) and their unenriched counterparts, take advantage of the enhanced dispersion afforded by both 13C and 1H chemical shifts, diminishing the difficulties arising from the signal-overlap problem and aiding in definitive signal assignments. In this research, protolignin in xylem cell walls was specifically 13C-enriched at all of the individual phenylpropanoid side-chain carbons by feeding 13C-enriched coniferins to growing stems of Ginkgo biloba. The whole xylem fractions containing 13C-enriched and unenriched protolignins were dissolved in a mixture of N-methylimidazole and DMSO, and then acetylated. Solution state 2D-NMR (HSQC) spectra of the acetylated whole cell wall were acquired. Difference spectra between the walls containing 13C-enriched and unenriched lignins afforded simplified 2D spectra in which well-separated signals were assigned exclusively to the specifically enriched carbons. This novel NMR technique provides a useful tool for elucidation of entire protolignin in the cell wall of ginkgo xylem.

  • 22. Terashima, Noritsugu
    et al.
    Hafrén, Jonas
    Westermark, Ulla
    VanderHart, D.L.
    Nondestructive analysis of lignin structure by NMR spectroscopy of specifically 13C-enriched lignins: Part 1. Solid state study of ginkgo wood2002In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 56, no 1, p. 43-50Article in journal (Refereed)
    Abstract [en]

    Guaiacyl-type lignin is the major component of ginkgo lignin. Specific 13c-enrichment of α, β and γ-carbons of the guaiacylpropane side chains was achieved by administration of coniferin-[α13C], coniferin-[β-13C] and coniferin-[γ13C], respectively, to growing stems of ginkgo trees. Unenriched coniferin was administered as a control. The xylem tissues containing specifically 13C-enriched lignins or unenriched lignin were subjected to analysis by solid state NMR. Subtraction of the spectrum of tissue containing unenriched lignin from the spectra of tissues containing 13C-enriched lignins gave difference spectra exclusively assigned to the enriched side chain carbons of intact protolignin in the cell walls. From the signal intensities determined under quantitative conditions and an estimate of corresponding standard uncertainties, the percentage ranges of the major inter-unit lignin bonds originating from the β-carbon of the coniferin precursor were estimated to be: β-O-4/α-O-R (R = H, polysaccharides or lignols) including β-OH, 53% to 57%; combined β-5, β-β and β-1, 32% to 36%; coniferaldehyde end groups, 2% to 4%; and coniferyl alcohol end groups, 4% to 6%.

  • 23.
    Zhaolong, Zhu
    et al.
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Marklund, Birger
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guo, Xiaolei
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Cao, Pingxiang
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Zhu, Nanfeng
    College of Material Science and Engineering, Nanjing Forestry University, Nanjing.
    Cutting forces and chip formation revisited based on orthogonal cutting of Scots pine2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 73, no 2, p. 131-138Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to understandbetter the cutting forces and chip formation of Scots pine(Pinus sylvestris L.) with different moisture contents (MCs)and machined in different cutting directions. To thatend, an orthogonal cutting experiment was designed,in which Scots pine was intermittently machined usinga tungsten carbide tool to produce chips. The cuttingforces were measured and the chip shapes were quantitativelydescribed. Four conclusions can be drawn: (1)with increasing MC, the average cutting forces initiallydecreased and then stabilized, while the angle betweenthe direction of the main and the resultant force continuouslydecreased. (2) The average cutting forces in the 90°–0° cutting direction were lower than the same forces inthe 90°–90° cutting direction. (3) During machining, thedynamic cutting forces fluctuated less in the 90°–0° case.However, the dynamic feeding forces showed a decreasingtrend in both the 90°–0° and the 90°–90° cases. (4) Theprocess applied produced granule chips and flow chips,while less curly flow chips with a higher radius of curvaturewere more easily produced from samples with highMCs in the 90°–0° cutting direction.

1 - 23 of 23
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