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  • 1.
    Ahrenstedt, Lage
    et al.
    KTH, School of Biotechnology (BIO). KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Olksanen, Antti
    VTT Technical Research Centre of Finland.
    Salmien, Kristian
    VTT Technical Research Centre of Finland.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Paper dry strength improvement by xyloglucan addition: Wet-end application, spray coating and synergism with borate2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 1, p. 8-14Article in journal (Refereed)
    Abstract [en]

    The polysaccharide xyloglucan as a wet-end additive improves paper properties. In the present study, paper strength improvement was analysed for dry handsheets made from chemical, mechanical and recycled pulps coated with xyloglucan in a spray application. Results are compared with sheets made from the same pulps treated with xyloglucan in the wet-end. Kraft pulp handsheets of bleached hardwood and softwood showed significant improvements of tensile, tear and Z-strength by xyloglucan spray treatment versus wet-end application, whereas handsheets of de-inked and thermomechanical pulp were improved only slightly. In both wet-end and spray applications, the effect of xyloglucan addition was intimately related to the presence of non-cellulosic components on the fibre surface. Further strength improvements were obtained for chemical pulps by addition of borax to the spray solution, which were likely to be due to the formation of borate-mediated xyloglucan cross-links. Spray coating of xyloglucan, with or without borax, thus represents a potential new application of this polysaccharide to increase paper dry strength.

  • 2.
    Areskogh, Dimitri
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Nousiainen, Paula
    University of Helsinki, Department of Chemistry.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sipilä, Jussi
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Oxidative polymerisation of models for phenolic lignin end-groups by laccase2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 1, p. 21-34Article in journal (Refereed)
    Abstract [en]

    The redox enzyme laccase can lead to cross-linking of lignin molecules by oxidising phenolic end groups to resonance-stabilised radicals that can undergo radical coupling to form covalent bonds. This property has potential for many technical applications. However, laccase treatment can also lead to degradation. Experiments were performed with two laccases of different oxidation potential and pH and temperature optima. The predominant reaction following laccase oxidation is the formation of 5-5' and 4-O-5' bonds. If the 5-position is blocked, other reactions occur, including coupling of the 1-position and oxidation of the a-position, which aggravates cross-linking of different lignin molecules. The product profile generated by the two laccases is somewhat different, mainly because of the different pH rather than differences in enzyme activity. Reaction mechanisms and the technical and biological significance of the results are discussed.

  • 3. Backstrom, Marie
    et al.
    Jensen, Anna
    Brännvall, Elisabet
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Influence of chip presteaming conditions on kraft pulp composition and properties2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 5, p. 393-399Article in journal (Refereed)
    Abstract [en]

    Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.

  • 4. Baumberger, Stephanie
    et al.
    Abaecherli, Alfred
    Fasching, Mario
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gosselink, Richard
    Hortling, Bo
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Saake, Bodo
    de Jong, Ed
    Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method2007In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 61, no 4, p. 459-468Article in journal (Refereed)
    Abstract [en]

    The reactivity and physicochemical properties of lignins are partly governed by their molar mass distribution. The development of reliable standard methods for determination of the molar mass distribution is not only relevant for designing technical lignins for specific applications, but also for monitoring and elucidating delignification and pulping processes. Size-exclusion chromatography (SEC) offers many advantages, such as wide availability, short analysis time, low sample demand, and determination of molar mass distribution over a wide range. A collaborative study has been undertaken within the Eurolignin European thematic network to standardise SEC analysis of technical lignins. The high-molar-mass fraction of polydisperse lignins was shown to be the main source of intra- and interlaboratory variations, depending on the gel type, elution solvent, detection mode, and calculation strategy. The reliability of two widespread systems have been tested: one based on alkali and a hydrophilic gel (e.g., TSK Toyopearl gel) and the other based on THF as solvent and polystyrene-based gels (e.g., Styragel). A set of practical recommendations has been deduced.

  • 5.
    Bengtsson, Andreas
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Bengtsson, Jenny
    Swerea IVF, Box 104, SE-43122 Molndal, Sweden..
    Olsson, Carina
    Swerea IVF, Box 104, SE-43122 Molndal, Sweden..
    Sedin, Maria
    RISE Innventia, Box 5604, SE-11486 Stockholm, Sweden..
    Jedvert, Kerstin
    Swerea IVF, Box 104, SE-43122 Molndal, Sweden..
    Theliander, Hans
    Chalmers Univ Technol, SE-41296 Gothenburg, Sweden..
    Sjoholm, Elisabeth
    RISE Innventia, Box 5604, SE-11486 Stockholm, Sweden..
    Improved yield of carbon fibres from cellulose and kraft lignin2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 12, p. 1007-1016Article in journal (Refereed)
    Abstract [en]

    To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70: 30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48-51%). No difference in the mechanical properties of the produced CF was observed.

  • 6.
    Bjurhager, Ingela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gamstedt, E. Kristofer
    Keunecke, Daniel
    Niemz, Peter
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mechanical performance of yew (Taxus baccata L.) from a longbow perspective2013In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 7, p. 763-770Article in journal (Refereed)
    Abstract [en]

    Yew (Taxus baccata L.) longbow was the preferred weapon in the Middle Ages until the emergence of guns. In this study, the tensile, compression, and bending properties of yew were investigated. The advantage of yew over the other species in the study was also confirmed by a simple beam model. The superior toughness of yew has the effect that a yew longbow has a higher range compared with bows made from other species. Unexpectedly, the mechanical performance of a bow made from yew is influenced by the juvenile-to-mature wood ratio rather than by the heartwood-to-sapwood ratio. A yew bow is predicted to have maximized performance at a juvenile wood content of 30-50%, and located at the concave side (the compressive side facing the bowyer). Here, the stiffness and yield stress in compression should be as high as possible.

  • 7.
    Bjurhager, Ingela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ljungdahl, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wallstrom, Lennart
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    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.

  • 8.
    Brodin, Ida
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Sjöholm, Elisabeth
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kraft lignin as feedstock for chemical products: The effects of membrane filtration2009In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 3, p. 290-297Article in journal (Refereed)
    Abstract [en]

    The use of technical lignins as feedstock for chemical products will require improvements in purity, molecular mass distribution, and thermal behavior. Therefore, industrial black liquors from kraft pulping of softwood (spruce/ pine) and hardwood (birch and Eucalyptus globulus) have been subjected to fractionation according to molecular mass by ceramic membranes. After acidification and isolation of the lignin fractions, a variety of analytical methods have been applied to help understand their structure - property relationships. From all types of lignin, the chemical and polymeric properties of fractions isolated from the membrane permeates were more homogeneous. This demonstrates that technical kraft lignins, irrespective of origin, may constitute an interesting feedstock for products, such as carbon fibers, adhesives, and phenol-based polymers.

  • 9.
    Bryne, Lars-Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lausmaa, Jukka
    SP Technical Research Institute of Sweden, Chemistry and Materials Technology, Borås, Sweden.
    Ernstsson, Marie
    Institute for Surface Chemistry, Stockholm, Sweden.
    Englund, Finn
    SP Trätek, Technical Research Institute of Sweden, Wood Technology, Borås, Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ageing of modified wood: Part 2: Determination of surface composition of acetylated, furfurylated, and thermally modified wood by XPS and ToF-SIMS2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 305-313Article in journal (Refereed)
    Abstract [en]

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

  • 10.
    Bryne, Lars-Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ageing of modified wood: Part 1: Wetting properties of acetylated, furfurylated, and thermally modified2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 295-304Article in journal (Refereed)
    Abstract [en]

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

  • 11.
    Brännvall, Elisabet
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Innventia AB.
    Backström, Marie
    Innventia AB.
    Improved impregnation efficiency and pulp yield of softwood kraft pulp by high effective alkali charge in the impregnation stage2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 11, p. 1031-1037Article in journal (Refereed)
    Abstract [en]

    A pulp yield increase up to 2% can be achieved by impregnation with a liquor containing 2 M effective alkali ( EA) concentration instead of 1 M. The yield increase is due to higher cellulose and glucomannan contents in the pulp, which can be rationalized by less yield loss by peeling, as impregnation is more effective at an elevated EA level. A rapid loading of chips with alkali can be realized due to a high diffusion rate. When the temperature becomes higher in the cooking stage, enough alkali is available for delignification reactions without the risk of alkali depletion in the chip core, so that the delignification is more homogeneous.

  • 12.
    Carlsson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Lind, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Merényi, Gabor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    A selectivity study of reaction of the carbonate radical anion with methyl beta- D-cellobioside and methyl beta-D-glucoside in oxygenated aqueous solutions2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 2, p. 130-136Article in journal (Refereed)
    Abstract [en]

    In the presence of oxygen, radiolytically generated carbonate radical anions, CO3.-, were reacted with methyl beta-D-cellobioside and methyl beta-D-glucoside. From the ensuing product pattern, it was concluded that CO3 center dot- abstracts hydrogen atoms predominantly from glucosidic C1 - H bonds. This high intramolecular selectivity was rationalised mainly in terms of a polar effect on the transition state of the hydrogen abstraction reaction. The present findings are in sharp contrast to the relative inertness of CO3(center dot-) towards glucosidic C1 - H bonds previously observed in cotton linters. The reasons for this discrepancy are discussed in light of a possible future role of CO3 center dot- as a bleaching agent for pulp.

  • 13.
    Carlsson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Stenman, David
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Merényi, Gabor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    A comparative study on the degradation of cotton linters induced by carbonate and hydroxyl radicals generated from peroxynitrite2005In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 2, p. 132-142Article in journal (Refereed)
    Abstract [en]

    Carbonate (CO3.(-)) and hydroxyl (HO.) radicals were chemically produced in cotton linter suspensions using peroxynitrite as a radical precursor. Both radicals could degrade cotton linters, as shown by viscosity and GPC-SEC measurements. As evidenced by the viscosity measurements, the presence of oxygen during the cotton linter treatments slightly increased cellulose degradation by both radicals. For the carbonate radical, more than 90% of the viscosity losses could be recovered by reductive NaBH4 treatment before measuring the viscosity, whereas only approximately 40% of the viscosity was recovered after hydroxyl radical degradation and subsequent NaBH4 treatment. This indicates that carbonate radicals mainly abstract H-atoms adjacent to hydroxyl groups, i.e., at C-2, C-3 and C-6. This intramolecular selectivity may reflect a polar effect, whereby hydrogen atom abstractions from these positions are favoured. In addition, abstraction at C-6 would be sterically and statistically favoured.

  • 14.
    Carlsson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Stenman, David
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Merényi, Gabor
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    The Carbonate Radical as One-Electron Oxidant of Carbohydrates in Alkaline media2005In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 2, p. 143-146Article in journal (Refereed)
    Abstract [en]

    The mechanism by which the carbonate radical anion reacts with D-glucose in alkaline aqueous solutions has been studied by means of gamma-radiolysis. From the product analysis it is concluded that the reaction sequence is initiated by a one-electron transfer between the carbonate radical anion and deprotonated D-glucose. In the presence of molecular oxygen, the major, if not only products of this reaction sequence are formic acid, arabinose and gluconic acid and reaction schemes are proposed to account for the observed formation of these products.

  • 15.
    Chen, Chao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Illergård, Josefin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Effect of cationic polyelectrolytes in contact-active antibacterial layer-by-layer functionalization2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 7-8, p. 649-658Article in journal (Refereed)
    Abstract [en]

    Contact-active surfaces have been created by means of the layer-by-layer (LbL) modification technique, which is based on previous observations that cellulose fibers treated with polyelectrolyte multilayers with polyvinylamine (PVAm) are perfectly protected against bacteria. Several different cationic polyelectrolytes were applied, including PVAm, two different poly(diallyl dimethyl ammonium chloride) polymers and two different poly(allylamine hydrochloride) polymers. The polyelectrolytes were self-organized in one or three layers on cellulosic fibers in combination with polyacrylic acid by the LbL method, and their antibacterial activities were evaluated. The modified cellulose fibers showed remarkable bacterial removal activities and inhibited bacterial growth. It was shown that the interaction between bacteria and modified fibers is not merely a charge interaction because a certain degree of bacterial cell deformation was observed on the modified fiber surfaces. Charge properties of the modified fibers were determined based on polyelectrolyte titration and zeta potential measurements, and a correlation between high charge density and antibacterial efficiency was observed for the PVAm and PDADMAC samples. It was demonstrated that it is possible to achieve antibacterial effects by the surface modification of cellulosic fibers via the LbL technique with different cationic polyelectrolytes.

  • 16.
    Dang, Binh T. T.
    et al.
    Chalmers Univ Technol, Dept Chem & Biol Engn, Forest Prod & Chem Engn, SE-41296 Gothenburg, Sweden..
    Brelid, Harald
    Sodra Innovat, SE-43286 Varobacka, Sweden..
    Theliander, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers Univ Technol, Dept Chem & Chem Engn, Forest Prod & Chem Engn, SE-41296 Gothenburg, Sweden.
    Carbohydrate content of black liquor and precipitated lignin at different ionic strengths in flow-through kraft cooking2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 7, p. 539-547Article in journal (Refereed)
    Abstract [en]

    The influence of sodium ion concentration [Na+] on the dissolution of carbohydrates in black liquor (BL) during flow-through kraft cooking of Scots pine wood meal (Pinus sylvestris) was studied. Fractions of BL were collected at different times and the carbohydrate content of the various fractions was analysed. Lignin was precipitated from the BL by lowering the pH, and the carbohydrate content of the precipitated lignins (L-prec) was also examined. The molecular weight distribution (MWD) of the L-prec samples was analysed. Xylose (Xyl) was found to be the most predominant sugar in BL aside from arabinose (Ara) and galactose (Gal), while the amounts of these sugars decreased with increasing levels of [Na+] in the cooking liquor. The minor amounts of mannose (Man) found in BL was not influenced by the [Na+]. The effects of NaCl and Na2CO3 on the carbohydrate dissolution were similar, but slightly lower concentrations of Ara and Xyl were found in the case of NaCl application. All of the L-prec samples contained some carbohydrate residues, the contents of which increased with increasing cooking time and decreased with higher [Na+]. It can be concluded that arabinoglucuronoxylan (AGX) along with arabinogalactans (AG) and arabinan, are covalently linked to lignin. The glucose (Glc) residue detected in L-prec may originate from 1,3-beta-glucan linked to lignin.

  • 17. Dang, Binh T. T.
    et al.
    Brelid, Harald
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 6, p. 495-501Article in journal (Refereed)
    Abstract [en]

    The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (M-w) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to M-w decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].

  • 18. Daniel, Geoffrey
    et al.
    Filonova, Lada
    Kallas, Asa M.
    Teeri, Tuula T.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Morphological and chemical characterisation of the G-layer in tension wood fibres of Populus tremula and Betula verrucosa: Labelling with cellulose-binding module CBM1(HjCel7A) and fluorescence and FE-SEM microscopy2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 6, p. 618-624Article in journal (Refereed)
    Abstract [en]

    The gelatinous layer (G-layer) formed on the lumen wall in early- and latewood fibres of poplar and birch tension wood was characterised using a novel molecular marker specific for crystalline cellulose in conjunction with fluorescence and FE-SEM microscopy. Crystalline cellulose was localised using a cloned Cel7A cellulose-binding module (CBM1(HjCel7A)) from the fungus Hypocrea jecorina conjugated directly to FITC/TRITC or indirectly via a secondary antibody conjugated to FITC for fluorescence microscopy or to gold/silver for FE-SEM. With the CBM1(HjCel7A) conjugate, the G-layer was clearly distinguished from other secondary cell-wall layers as a bright green layer visible in fibres of tension wood in fluorescence microscopy. FEM-SEM images revealed the supramolecular architecture of the G-layer of poplar wood, which consists of well-defined, often concentrically orientated, cellulose aggregates of the order of 30-40 nm. The cellulose aggregates typically have a microfibril angle of almost 0 degrees. Studies on cellulose marked with CBM1(HjCel7A) followed by Au labelling and Ag enhancement complemented the fluorescence observations. The studies demonstrate the usefulness of this novel molecular marker for crystalline cellulose in situ, which was previously difficult to localise. Further proof of distinct cellulose aggregates was observed.

  • 19.
    De Magistris, Federica
    et al.
    STFI-Packforsk AB.
    Salmén, Lennart
    STFI-Packforsk AB.
    Combined shear and compression analysis using a modified Iosipescu shear test device: Experimental studies on dry wood2005In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 5, p. 539-545Article in journal (Refereed)
    Abstract [en]

    The mechanical treatment of wood in a refiner involves a complex combination of shear and compression forces. To obtain more knowledge on this process, the possibility of using an apparatus based on the Iosipescu shear test device to measure the behaviour of wood under a combined shear and compression load was tested. In this new apparatus, different combinations of shear and compression load were achieved by different rotations of the shear test device itself. Numerical simulations of the combined shear and compression test were carried out and compared with experimental data to verify the reliability of the modified device as applied to wood. It was concluded that the new apparatus is suitable for applying different combinations of shear and compression load in testing wood samples. However, finite element analysis showed that with the use of homogeneous material in the model, the level of strain reached would be 10-fold smaller. This fact is probably due to the honeycomb structure of the wood cells, which allows for different local deformation that could not be represented by the continuous material used in the model.

  • 20.
    Dedic, Dina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sandberg, Teresia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Tomas
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Analysis of lignin and extractives in the oak wood of the 17th century warship Vasa2014In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 4, p. 419-425Article in journal (Refereed)
    Abstract [en]

    The wood in the 17th century Swedish warship Vasa is weak. A depolymerization of the wood's cellulose has been linked to the weakening, but the chemical mechanisms are yet unclear. The objective of this study was to analyze the lignin and tannin moieties of the wood to clarify whether the depolymerization of cellulose via ongoing oxidative mechanisms is indeed the main reason for weakening the wood in the Vasa. Lignin was analyzed by solid-state nuclear magnetic resonance [cross-polarization/magic-angle spinning (CP/MAS) C-13 NMR] and by means of wet chemical degradation (thioacidolysis) followed by gas chromatography-mass spectrometry (GC-MS) of the products. No differences could be observed between the Vasa samples and the reference samples that could have been ascribed to extensive lignin degradation. Wood extracts (tannins) were analyzed by matrix- assisted laser desorption ionization (MALDI) combined with time-of-flight (TOF) MS and C-13 NMR spectroscopy. The wood of the Vasa contained no discernible amounts of tannins, whereas still-waterlogged Vasa wood contained ellagic acid and traces of castalagin/vescalagin and grandinin. The results indicate that the condition of lignin in the Vasa wood is similar to fresh oak and that potentially harmful tannins are not present in high amounts. Thus, oxidative degradation mechanisms are not supported as a primary route to cellulose depolymerization.

  • 21. Doliška, A.
    et al.
    Willför, S.
    Strnad, S.
    Ribitsch, V.
    Kleinschek, K. S.
    Eklund, P.
    Xu, Chunlin
    KTH, School of Biotechnology (BIO), Glycoscience.
    Antithrombotic properties of sulfated wood-derived galactoglucomannans2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 149-154Article in journal (Refereed)
    Abstract [en]

    Galactoglucomannans (GGMs) are water-soluble polysaccharides released and accumulated in process waters in the production of thermomechanical pulp. The general trend in the forestry industry is moving towards bio-refineries, for example utilizing these hemicelluloses as bioactive substances. At present, there is no industrial use of wood-derived mannans. In this study, GGMs extracted from thermomechanical pulp, as well as further carboxymethyl-ated galactoglucomannans (CM-GGMs), were sulfated to increase their antithrombotic properties. The products were characterized with Fourier transform infrared spectroscopy, nuclear magnetic resonance and capillary electrophoresis. The carbohydrate composition and sulfur amounts were determined. The products' total charges were determined by polyelectrolyte titrations and their antithrombotic effect was measured based on the activated partial thromboplastin time. The results showed a significant increase in the antithrombotic effect of the sulfated galactoglucomannans from spruce wood and thus a potential new use for wood-derived mannans.

  • 22.
    Du, Xueyu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Eugenio Martin, Maria E.
    Instituto Nacional de Investigacion y Tecnologias Agrarias y Alimentarias.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Improvement of kraft pulp bleaching by treatments with laccase, urea, and refining2013In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 6, p. 651-658Article in journal (Refereed)
    Abstract [en]

    Unbleached Eucalyptus kraft pulps were treated by three methods and the bleaching effects have been evaluated. The treatments were performed by a laccase mediator system (LMS), refining (R), and urea (U) alone and in combination of these methods. The bleached pulps were characterized in terms of κ number, hexenuronic acid content, brightness, and viscosity. In addition, the lignin-carbohydrate complexes (LCCs) were fractionated and characterized with regard to the fractionation yield, lignin content, and carbohydrate composition. Moreover, the 1 H nuclear magnetic resonance spectra were recorded and the thioacidolysis-gas chromatography and thioacidolysis-size exclusion chromatography analyses were performed. The LMS treatment resulted mainly in a slightly better delignification as manifested by a κ number (K no.) reduction of 0.8 units. The effects of the U treatment included delignification (1.4 κ units), hexenuronic acid removal (3 μ mol g-1), and improved pulp brightness (3.4 ISO units). The R treatment darkened the pulp (3 ISO units), whereas the bleaching of the R-pulp by subsequent LMS or U treatment enhanced the brightness (0.5 unit more) or delignification (0.3 unit more). The residual lignin in the pulp samples was present mainly as xylan-lignin. The Klason lignin content from the xylan lignin fraction decreased as the degree of delignification increased. The pulp darkening followed by the R treatment was interpreted as the result of the formation of condensed lignin structures, but these condensed lignins were substantially removed by the subsequent LMS or U treatment.

  • 23.
    Duval, Antoine
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Vilaplana, Francisco
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Biotechnology (BIO), Glycoscience.
    Crestini, Claudia
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Solvent screening for the fractionation of industrial kraft lignin2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 1, p. 11-20Article in journal (Refereed)
    Abstract [en]

    The polydispersity of commercially available kraft lignins (KLs) is one of the factors limiting their applications in polymer-based materials. A prerequisite is thus to develop lignin fractionation strategies compatible with industrial requirements and restrictions. For this purpose, a solvent-based lignin fractionation technique has been addressed. The partial solubility of KL in common industrial solvents compliant with the requirements of sustainable chemistry was studied, and the results were discussed in relation to Hansen solubility parameters. Based on this screening, a solvent sequence is proposed, which is able to separate well-defined KL fractions with low polydispersity.

  • 24.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Henriksson, Marielle
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A multinuclear magnetic resonance imaging (MRI) study of wood with adsorbed water: Estimating bound water concentration and local wood density2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 1, p. 103-107Article in journal (Refereed)
    Abstract [en]

    The interaction between moisture and the macromolecular wood tissue is of critical importance to wood properties. In this context, magnetic resonance imaging (MRI) is very promising as this method could deliver molecular information on the submillimeter scale (i.e., along concentration gradients) about both free and adsorbed water and the cell wall polymers. In the present study, it is demonstrated for the first time that wood containing adsorbed heavy water ((H2O)-H-2) can be studied by MRI based on separated images due to water (H-2 MRI) and cell wall polymers (H-1 MRI). Data confirm that in specimens equilibrated at controlled humidity there is a direct correlation between bound water content and relative density of the polymers in wood tissue; there is a strong variation across annual rings.

  • 25.
    Ek, Monica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gierer, Josef
    Jansbo, Kerstin
    Study on the Selectivity of Bleaching with Oxygen-Containing Species1989In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 43, no 6, p. 391-396Article in journal (Refereed)
    Abstract [en]

    In the bleaching of pulp, the term Selectivity is widely used but poorly defined.This work is an attempt to quantify the selectivity of bleaching with Oxygen-containing species by generating hydroxil radicals and measuring their reaction rates with some lignin and carbohydrate models. Results of this investigation show that the selectivity factor defined as the ratio of the rate constants for a given pair of lignin and carbohydrate models, lies between 5 and 6.

  • 26.
    Fahlén, Jesper
    et al.
    STFI-Packforsk AB.
    Salmén, Lennart
    STFI-Packforsk AB.
    Ultrastructural changes in a holocellulose pulp revealed by enzymes, thermoporosimetry and atomic force microscopy2005In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 6, p. 589-597Article in journal (Refereed)
    Abstract [en]

    To increase our knowledge of the ultrastructure within softwood fibres, enzymatic treatment, thermoporosimetry, light microscopy, and atomic force microscopy with image analysis were used to investigate the structure of holocellulose softwood pulp fibres. The size of the average cellulose fibril aggregates and the width of pore and matrix lamellae were found to be uniform across the secondary cell-wall layer in the transverse direction of the wood fibre wall. In holocellulose, these dimensions were very similar to those in the native wood, whereas in kraft pulp the cellulose fibril aggregates were larger and the pore and matrix lamellae broader. These differences between holocellulose and kraft pulp fibres suggest that a high temperature is needed for cellulose fibril aggregation to occur. Neither refining nor drying of the holocellulose pulp changed the cellulose fibril aggregate size. Upon drying and enzymatic treatment, a small decrease in the pore and matrix lamella width was evident throughout the fibre wall. This indicated not only uniform distribution of pores throughout the fibre wall, but also enzymatic accessibility to the entire fibre wall. The holocellulose pulp had a somewhat larger pore volume than the kraft pulp. Refining of the holocellulose pulp led to pore closure, probably due to increased mobility of the fibre wall. The enzymatic treatment revealed that during hydrolysis of one hemicellulose, part of the other was also dissolved, indicating that the two hemicelluloses are to some extent linked to each other in the structure.

  • 27.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Professor Gosta Brunow (1936-2013) Obituary2014In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 2, p. 253-254Article in journal (Refereed)
  • 28.
    Gellerstedt, Göran
    et al.
    KTH, Superseded Departments, Pulp and Paper Technology.
    Al-Dajani, W. W.
    Bleachability of alkaline pulps - Part 1. The importance of beta-aryl ether linkages in lignin2000In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, no 6, p. 609-617Article in journal (Refereed)
    Abstract [en]

    Analytical and structural studies were done on different types of alkaline pulps and their isolated residual lignins. Although having the same degree of delignification after cooking, some pulps were easier to bleach than others. All isolated residual lignins were found to contain beta -aryl ether (beta -O-4) structures in reasonable amounts when analysed by thioacidolysis (greater than or equal to 10% of the native lignin value). At decreasing kappa numbers, there was also a corresponding decrease in the amount of beta -aryl ether structures in the residual lignin. Moreover, a high beta -aryl ether content in the unbleached residual lignin after cooking was found to contribute to a better bleachability of the pulp, especially when hydrogen peroxide stages were involved. At the same degree of delignification, the superior bleachability of alkaline sulfite pulps over kraft pulps was shown to be attributable to a higher content of beta -aryl ether linkages in the further type of pulps.

  • 29. Gosselink, Richard J. A.
    et al.
    van Dam, Jan E. G.
    de Jong, Ed
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Scott, Elinor L.
    Sanders, Johan P. M.
    Effect of periodate on lignin for wood adhesive application2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 2, p. 155-162Article in journal (Refereed)
    Abstract [en]

    Development of eco-friendly binders with no harmful emission during its complete life cycle is of high interest for the wood-based industry. In this paper, a fully renewable binder based on activated lignin and poly-furfuryl alcohol and a partly renewable lignin based phenol-formaldehyde (PF) binder were evaluated. Activation of kraft and soda lignins, isolated respectively from softwood and non-woods, by periodate oxidation was performed to improve lignin reactivity and application in wood adhesives. Periodate oxidation of lignin leads to higher lignin acidity, formation of quinonoid groups under more severe conditions, higher molar mass and higher reactivity towards the curing of furfuryl alcohol within a temperature range currently used in industry. Comparison of a 100% furan-based glue with a furan-based glue substituted by 10% lignin yields comparable product properties. However, periodate-activated lignin leads to lower wood failure, which might be caused by incompletely solubilised lignin particles in the acidic formulation disturbing crosslinking of the furan resin. Unmodified softwood kraft lignin performs well in a PF resin formulation at substitution levels up to 30% (w/w). Periodate oxidation of soda lignins enhances the glue performance because higher wood failure is attained. The higher molar mass after periodate treatment could be an important parameter for development of a stronger wood binder.

  • 30. Gosselink, Richard J. A.
    et al.
    van Dam, Jan E. G.
    de Jong, Ed
    Scott, Elinor L.
    Sanders, Johan P. M.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Fractionation, analysis, and PCA modeling of properties of four technical lignins for prediction of their application potential in binders2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 2, p. 193-200Article in journal (Refereed)
    Abstract [en]

    Functional properties of technical lignins need to be characterized in more detail to become a higher added value renewable raw material for the chemical industry. The suitability of a lignin from different plants or trees obtained by different technical processes can only be predicted for selected applications, such as binders, if reliable analytical data are available. In the present paper, structure dependent properties of four industrial lignins were analyzed before and after successive organic solvent extractions. The lignins have been fractionated according to their molar mass by these solvents extractions. Kraft and soda lignins were shown to have different molar mass distributions and chemical compositions. Lignin carbohydrate complexes are most recalcitrant for extraction with organic solvents. These poorly soluble complexes can consist of up to 34% of carbohydrates in soda lignins. Modeling by principle component analysis (PCA) was performed aiming at prediction of the application potential of different lignins for binder production. The lignins and their fractions could be classified in different clusters based on their properties, which are structure dependent. Kraft soft-wood lignins show the highest potential for plywood binder application followed by hardwood soda lignin and the fractions of Sarkanda grass soda lignin with medium molar mass. Expectedly, the softwood lignins contain the highest number of reactive sites in ortho positions to the phenolic OH group. Moreover, these lignins have a low level of impurities and medium molar mass.

  • 31.
    Henriksson, Gunnar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lawoko, Martin
    Martin, Maria Eugenia Eugenio
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lignin-carbohydrate network in wood and pulps: A determinant for reactivity2007In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 61, no 6, p. 668-674Article in journal (Refereed)
    Abstract [en]

    Pretreatment of wood or kraft pulp with endoglucanase followed by swelling in urea leaves a non-crystalline residue that can be dissolved in strong aqueous sodium hydroxide-sodium borate solution. A stepwise precipitation process employing acid and barium ions can separate lignin-carbohydrate complexes enriched in individual polysaccharides. This procedure has been applied to eucalypt and birch wood and to the corresponding kraft pulps. Thioacidolysis of the various lignin-carbohydrate complexes was used as the major analytical technique to obtain information about the structure and structural changes in lignin. A combination of thioacidolysis and size exclusion chromatography was used to obtain knowledge on the degree of depolymerisation and repolymerisation of lignin when going from wood to chemical pulp. In contrast to spruce wood and kraft pulp, complete recovery of the lignin-carbohydrate complexes could not be obtained from hardwood samples.

  • 32. Hofstetter, Karin
    et al.
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hierarchical modelling of microstructural effects on mechanical properties of wood. A review COST Action E35 2004-2008: Wood machining - micromechanics and fracture2009In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 2, p. 130-138Article, review/survey (Refereed)
    Abstract [en]

    Wood exhibits a hierarchical architecture. Its macroscopic properties are determined by microstructural features at different scales of observation. Recent developments of experimental micro-characterisation techniques have delivered further insight into the appearance and the behaviour of wood at smaller length scales. The improved knowledge and the availability of increasingly powerful micromechanical modelling techniques and homogenisation methods have stimulated rather comprehensive research on multiscale modelling of wood. Linking microstructural properties to macroscopic characteristics is expected to improve the knowledge of the mechanical behaviour of wood and to serve as the basis for the development of innovative wood-based products and for biomimetic material design. Moreover, understanding fundamental aspects of wood machining requires multiscale approaches which can take into account the heterogeneity, anisotropy and hierarchies of wood and wood composites. In this review, recent developments in the field of hierarchical modelling of the hygroelastic behaviour of wood are discussed, and a short outline of the theoretical background is given. Much focus is placed on composite micromechanical models for the wood cell wall and on multiscale models for wood resting upon hierarchical finite element models and on the application of continuum micromechanics, respectively. These models generally lead to the specification of equivalent homogeneous continua with effective material properties. Finally, current deficiencies and limitations of hierarchical models are sketched and possible future research directions are specified.

  • 33. Hogberg, N.
    et al.
    Land, Carl Johan
    KTH, Superseded Departments, Biotechnology.
    Identification of Serpula lacrymans and other decay fungi in construction timber by sequencing of ribosomal DNA - A practical approach2004In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 58, no 2, p. 199-204Article in journal (Refereed)
    Abstract [en]

    We have approached species identification of wood decay fungi in construction wood by means of sequencing ribosomal DNA. Sequencing of the Internal Transcribed Spacer (ITS), which includes the 5.8S rDNA, is straightforward and provides a basis for species identification. Identification was either by BLAST search on sequences in GenBank or phylogenetic analysis. A number of important wood decay fungi such as Serpula lacrymans, S. himantioides, Antrodia serialis, A. sinuosa, Gloeophyllum sepiarium, Fomitopsis pinicola, Resinicium bicolor and Junghuhnia collabens have been successfully identified from fruitbodies and directly from wood samples. Sequence variants were found within the species sampled including S. himantioides, the close relative of S. lacrymans. But, among 27 samples from fruitbodies and mycelium of S. lacrymans, unexpectedly, no sequence variation was detected.

  • 34.
    Holmgren, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Monolignol dehydrogenative polymerization in vitro in the presence of dioxane and a methylated beta-beta ' dimer model compound2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 5, p. 508-513Article in journal (Refereed)
    Abstract [en]

    Lignin formation is believed to occur by polymerization of resonance-stabilized monolignol radicals formed by enzymatic oxidation. Recently, different hypotheses suggested that lignin polymerization is influenced by surfaces in the cell wall which can be polysaccharides or proteins. The latter is called the proteinaceous dirigent sites/template polymerization hypothesis. According to another hypothesis, lignin itself is believed to act as a template and replicate its primary structure. In this work, dehydrogenative polymerization (DHP) of the lignin precursor coniferyl alcohol was performed in vitro in the presence and absence of pinoresinol dimethyl ether (a beta-beta ' dimer model). Another peculiarity of the experiments was the presence of dioxane which afforded a high solubility of the reactants. The question was whether the presence of beta-beta ' dimer model would change the structure of the DHP formed. The DHPs were analyzed by quantitative C-13 NMR, GC-FID, and GC-MS. The dimer model as a template in the homogeneous polymerization state (in solution) did not influence the DHP structure.

  • 35.
    Ibarra, David
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Exploring enzymatic treatments for the production of dissolving grade pulp from different wood and non-wood paper grade pulps2009In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 6, p. 721-730Article in journal (Refereed)
    Abstract [en]

    The feasibility of producing dissolving grade pulps for viscose production from different fiber raw materials, such as paper grade pulps from wood and non-woody plants, was investigated. Commercial dried bleached hardwood kraft pulps from eucalypt, and bleached non-wood soda/AQ pulps from flax, hemp, sisal, abaca, and jute, were subjected to enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of cellulose and to reduce their hemicellulose content. A commercial monocomponent endoglucanase and a commercial xylanase were employed for biochemical treatment. The chemical treatment consisted of cold alkaline extraction. The effects of these pre-treatments on pulps were studied by reactivity, according to Fock's method, and viscosity measurements, determination of hemicellulose content, and recording of molecular weight distributions. The results were compared to those of commercial bleached eucalypt dissolving pulp. Eucalypt and sisal pulps showed high improvement in reactivity, reaching levels near or even higher than that of the eucalypt dissolving pulp (65%-70%), and a low hemicellulose content (2%-4%), when both were submitted to a sequence of treatments consisting of an initial xylanase treatment followed by cold alkaline extraction, and a final endoglucanase treatment. However, the viscosity decreased considerably. A uniform and narrow molecular weight distribution was observed in both eucalypt and sisal pulps after this sequential pre-treatment.

  • 36.
    Illergård, Josefin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Römling, Ute
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tailoring the effect of antibacterial polyelectrolyte multilayers by choice of cellulosic fiber substrate2013In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 5, p. 573-578Article in journal (Refereed)
    Abstract [en]

    There is a need for new, antibacterial cellulose-based materials. Antibacterial cellulosic fibers with irreversibly attached polyvinylamine (PVAm) and polyacrylic acid (PAA) in multilayers were developed based on a water-based physical adsorption process. The antibacterial substance is thus prevented from leaching, in contrast to materials containing, for example, silver. It was shown on fibers from different sources that the antibacterial effect against both Escherichia coli and Bacillus subtilis can be tailored. The efficiency correlated with the initial fiber charge, which in turn correlated with the amount of adsorbed PVAm. In the case of highly charged fibers, the antibacterial efficacy was more than 99.9%. A sustainable antibacterial material can be obtained in a simple way based on a water-based process.

  • 37. Josefsson, T.
    et al.
    Lennholm, H.
    Gellerstedt, Göran
    KTH, Superseded Departments, Pulp and Paper Technology.
    Steam explosion of aspen wood. Characterisation of reaction products2002In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 56, no 3, p. 289-297Article in journal (Refereed)
    Abstract [en]

    The steam explosion process was used to separate the components of aspen wood. The main goal was to obtain a material with a molecular weight distribution similar to that of dissolving pulp. To achieve variations in fibre structure and molecular weight, two series of steam explosions were made in which the time and temperature were varied according to factorial designs. The resulting pulps were very dark and were therefore bleached with hydrogen peroxide. The bleaching was sufficient to increase the brightness of the exploded material significantly The resulting lignocellulosic materials as well as the washing water were characterised by carbohydrate analysis. lignin analysis and size-exclusion chromatography. A large variation in the pulp composition as well as in cellulose and hemicellulose molecular weight was obtained merely by varying the time and temperature of the explosions. The results showed that pulps with properties ranging from a high xylan content (7%) and high molecular weight cellulose (900 000) to a low xylose content (<1%) and low molecular weight cellulose (<40 000) were produced. The exploded material consisted mainly of cellulose, hemicellulose and degraded polysaccharides. The degraded polysaccharides showed up as lignin in the Klason lignin analysis and in measurements of kappa number.

  • 38. Krusa, M.
    et al.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Johansson, G.
    Reitberger, T.
    Lennholm, H.
    Oxidative cellulose degradation by cellobiose dehydrogenase from Phanerochaete chrysosporium: A model compound study2005In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 3, p. 263-268Article in journal (Refereed)
    Abstract [en]

    Cellobiose dehydrogenase (CDH) is an extracellular enzyme produced by various wood-degrading fungi. It oxidizes cellobiose to cellobionolactone under reduction of molecular oxygen to hydrogen peroxide, and Fe3+ to Fe2+. These activated agents can thereafter form highly reactive hydroxyl radicals, which depolymerize wood polymers. In this work, cellulose depolymerization by CDH was studied using a model compound, methyl beta-D-glucopyranoside. The formation of glucose, arabinose, gluconic acid, erythrulose and formaldehyde were detected and a mechanism for the reaction is proposed. The biological importance of this enzyme-initiated reaction is discussed.

  • 39.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Moghaddam, Maziar Sedighi
    Wålinder, Magnus E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Liquid sorption, swelling and surface energy properties of unmodified and thermally modified Scots pine heartwood after extraction2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 3, p. 251-258Article in journal (Refereed)
    Abstract [en]

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

  • 40. Lawoko, M.
    et al.
    Nutt, A.
    Henriksson, H.
    Gellerstedt, Göran
    KTH, Superseded Departments, Pulp and Paper Technology.
    Henriksson, Gunnar
    KTH, Superseded Departments, Pulp and Paper Technology.
    Hemicellulase activity of aerobic fungal cellulases2000In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 54, no 5, p. 497-500Article in journal (Refereed)
    Abstract [en]

    Cellulases isolated from Trichoderma reesei and Phanerochaete chrysosporium were screened for hemi-cellulolytic, pectinolytic and cellulolytic activity using locust bean mannan, birchwood xylan, citrus fruit pectin and carboxymethylated cellulose (CMC) as substrates. The purpose of this work was to choose appropriate enzymes to include in a miniature cellulase system with minimal hemicellulase activity for the preparation of lignin-carbohydrate complexes (LCCs). The endoglucanases showed CMC activity whereas activity towards the substrate was not detected for the CBHs. Xylanase activity was observed for EG I and EG 38 whereas mannanase activity was observed for EG 44. None of the enzymes degraded pectin. The results suggest that CBH I, CBH II, CBH 58, EG II and EG III are good candidates for the effective preparation of LCCs. The possible biological function for the hemicellulolytic activity of cellulases is discussed.

  • 41.
    Lawoko, Martin
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Berggren, Rickard
    Berthold, Fredrik
    Henriksson, Gunnar
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Changes in the lignincarbohydrate complex in softwood kraft pulp during kraft and oxygen delignification2004In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 58, no 6, p. 603-610Article in journal (Refereed)
    Abstract [en]

    Three kraft pulps in the kappa number range between 50 and 20 and the same pulps oxygendelignified to similar lignin contents (kappa approximately 6) were analyzed for lignincarbohydrate complexes (LCC) by a method based on selective enzymatic hydrolysis of the cellulose, and quantitative fractionation of the LCC. Between 85 and 90% of residual lignin in the unbleached kraft pulp and all residual lignin in the oxygendelignified pulps were isolated as LCC. Three types of complexes were found; viz., xylanlignin, glucomannanligninxylan and glucanlignin complexes. After pulping to a high kappa number, most of the residual lignin was linked to xylan. Different delignification rates were observed so that most of the residual lignin was linked to glucomannan when the pulping was extended to a low kappa number. With increasing degree of oxygen delignification, a similar trend in the delignification rates of LCC was observed so that the residual lignin was increasingly linked to glucomannan. Complex LCC network structures seemed to be degraded into simpler structures during delignification. The differences in delignification rates are discussed with reference to the solubility properties and structural differences of LCC, and to morphological aspects of the pulp.

  • 42.
    Lawoko, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Characterisation of lignin-carbohydrate complexes (LCCs) of spruce wood (Picea abies L.) isolated with two methods.2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 2, p. 151-161Article in journal (Refereed)
    Abstract [en]

    A method for the quantitative isolation of lignin-carbohydrate complexes (LCCs) in a softwood is presented. The isolation steps involve partial enzymatic hydrolysis of cellulose, subsequent swelling in urea, and quantitative dissolution into four major fractions: (1) a galacto-glucomannan LCC containing similar to 8% of the wood lignin; (2) a glucane LCC containing similar to 4% of the wood lignin; (3) a xylan-lignin-glucomannan network LCC (xylan > glucomannan) containing similar to 40% of the wood lignin; and (4) a glucomannan-lignin-xylan network LCC (glucomannan) xylan) containing similar to 48% of the wood lignin. Endo-glucanase Novozyme 476, with only cellulase activity, and Ecopulp XM, with only xylanase and mannanase activities, were used as an enzymatic tool. From mildly ball-milled wood, all the lignin was isolated as LCCs. As a control, LCC was prepared from partially chlorite-delignified wood meal without ball milling, also in a mild procedure. The results were very similar to those obtained after ball milling. Thus, it can be safely concluded that the formation of new chemical linkages between lignin and carbohydrates during ball milling is improbable. Studies on isolated milled wood lignin (MWL) supported this conclusion and clearly showed that covalent linkages between lignin and carbohydrates are present. The study provide conclusive evidence of covalent linkages between lignin and carbohydrates in the native lignin in wood. It is concluded that carbohydrate-free lignin, i.e., lignin without covalent bonds to carbohydrates, probably cannot be present in spruce wood.

  • 43.
    Lawoko, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Characterization of Lignin-Carbohydrate Complexes from Spruce Sulfite Pulp: Lignin-polysaccharide networks III2006In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 2, p. 162-165Article in journal (Refereed)
    Abstract [en]

    Lignin-carbohydrate complexes (LCCs) were isolated from unbleached acid sulfite pulp by selective enzymatic hydrolysis followed by fiber swelling and extraction. Approximately 80% of the lignin in the pulp was found to be chemically linked to carbohydrates in three major fractions, viz. as one glucan-lignin complex (with 8% lignin) and two hemicellulose-lignin complexes (with 72% lignin). The latter two were further separated into one glucomannan-lignin complex (with similar to 25% lignin) and one xylan-lignin-glucomannan complex (with 45 - 50% lignin). Based on model experiments, it can be concluded that the lignin and carbohydrate moieties are probably linked together through benzyl ether linkages. Xylan is more stable towards acidic hydrolysis than galactoglucomannan, and this finding may explain the greater amount of xylan-rich LCC in the pulp.

  • 44.
    Lawoko, Martin
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Gellerstedt, Göran
    KTH, Superseded Departments, Fibre and Polymer Technology.
    New method for the quantitative preparation of lignin-carbohydrate complex from unbleached softwood kraft pulp: Lignin-polysaccharide networks I2003In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 57, no 1, p. 69-74Article in journal (Refereed)
    Abstract [en]

    A new method for the quantitative preparation of pulp representative lignin-carbohydrate complexes (LCC) has been developed, in which LCC has been systematically prepared at quantitative yield, fractionated and qualitatively determined. At least 90% of residual lignin in softwood kraft pulp is proposed to be chemically bonded to carbohydrates. A major part of LCC (92%) in softwood kraft pulp was observed between lignin, xylan and glucomannan, whereas a minor part (8%) was linked to cellulose. Half of the hemicelullosic LCC is a lignin-glucomannan complex. The other half is lignin-xylan complex and xylan-lignin-glucomannan complex. Thus, part of the residual lignin in softwood kraft pulp crosslinks xylan and glucomannan. The proposed linkages are of covalent type. At most 10% of the residual lignin is not bonded covalently to carbohydrates.

  • 45. Leppänen, Kirsi
    et al.
    Bjurhager, Ingela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Peura, Marko
    Kallonen, Aki
    Suuronen, Jussi-Petteri
    Penttilä, Paavo
    Love, Jonathan
    Fagerstedt, Kurt
    Serimaa, Ritva
    X-ray scattering and microtomography study on the structural changes of never-dried silver birch, European aspen and hybrid aspen during drying2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 6, p. 865-873Article in journal (Refereed)
    Abstract [en]

    The impact of drying on the structure of the never-dried hardwood cell wall was studied at nanometer level by means of wide- and small-angle X-ray scattering (WAXS, SAXS), and at micrometer level by X-ray microtomography (mu CT). Never-dried silver birch, European aspen and hybrid aspen samples were measured by WAXS in situ during drying in air. The samples included juvenile and mature wood, as well as normal and tension wood to allow comparison of the effects of different matrix compositions and microfibril angles. The deformations of cellulose crystallites and amorphous components of the cell wall were detected as changes in the cellulose reflections 200 and 004 and amorphous halo in the WAXS patterns. Especially, the width of the reflection 004, corresponding to the cellulose chain direction, increased due to drying in all the samples, indicating an increase of strain and disorder of the chains. Also, the cellulose unit cell shrank 0.2-0.3% during drying in this direction in all the samples except in hybrid aspen tension wood. According to the SAXS results of silver birch, the distance between microfibrils decreased during drying. It was detected by mu CT that the mean cross-sectional maximum width of the parenchymatous rays decreased from that of never-dried to air-dried birch by roughly 16%.

  • 46.
    Li, Dongfang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Drottning Kristinas väg 61, SE-114 86 Stockholm, Sweden.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Hydrophobic materials based on cotton linter cellulose and an epoxy-activated polyester derived from a suberin monomer2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed)
    Abstract [en]

    Suberin is a natural hydrophobic material that could be used to improve the water repellency of cellulose surfaces. It is also abundant in the outer bark of birch (Betula verrucosa); birch bark is a side-stream product in Scandinavia from the forest industry, which is generally burned for energy production. A suberin monomer, cis-9,10-epoxy-18-hydroxyoctadecanoic acid, was isolated from birch outer bark and polymerized via lipase (immobilized Candida antarctica lipase B). The resulting epoxy-activated polyester was characterized by nuclear magnetic resonance (NMR) imaging, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, and size exclusion chromatography. Then the polyester was cured with tartaric or oxalic acid, and the crosslinked polyesters were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry. Hydrophobic materials were prepared by compression molding of polyester-impregnated cellulose sheets, and the final products were characterized by FTIR, cross-polarization magic angle spinning 13 C NMR, and field-emission scanning electron microscopy. The water contact angle was significantly increased from 0 ° for the original cellulose sheets to over 100 ° for the produced hydrophobic materials.

  • 47.
    Li, Dongfang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sevastyanova, Olena
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Pretreatment of softwood dissolving pulp with ionic liquids2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 8, p. 935-943Article in journal (Refereed)
    Abstract [en]

    Few Scandinavian pulp mills produce dissolving pulps; however, the demand on textile fibers is increasing. This study investigates the chemical interaction of dissolving pulp with ionic liquids (ILs), where softwood and hardwood industrial dissolving pulps were pretreated with ILs 1-butyl-3-methyl-imidazolium acetate ([C(4)mim(+)]CH3COO-) and 1-butyl-3-methyl-imdazolium chloride ([C(4)mim(+)]Cl-). Time and temperature dependence of the dissolution process as well as the impact of the pretreatment on the molecular weight properties, thermal stability, morphology, and crystallinity of the cellulose were evaluated by means of size exclusion chromatography (SEC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and solid state nuclear magnetic resonance (NMR). It was shown that the dissolution of cellulosic material in ILs is a temperature-dependent process; however, the viscosity of ILs affected the efficiency of dissolution at a given temperature. Molecular weight properties were affected negatively by increased dissolution temperature, while the type of antisolvent for the regeneration had no major impact on the degree of polymerization of cellulose. Water was more efficient than ethanol for the regeneration of cellulose when performed at an elevated temperature. The pretreatment decreased the crystallinity of cellulosic material. This might lead to the increased accessibility and reactivity of cellulose.

  • 48.
    Li, Jiebing
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Martin-Sampedro, Raquel
    Pedrazzi, Cristiane
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Fractionation and characterization of lignin-carbohydrate complexes (LCCs) from eucalyptus fibers2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 1, p. 43-50Article in journal (Refereed)
    Abstract [en]

    The effect of milling time on the structure of lignin was investigated by analyzing the quantity and molecular size distribution of thioacidolysis products obtained from wood and pulp of eucalypt (Eucalyptus globulus). After milling, the ability of three solvent systems was determined to completely dissolve the wood or pulp meal. It was found that a mixture of DMSO and 50% aqueous tetrabutylammonium hydroxide was superior to either dimethylacetamide-LiCl or DMSO-tetrabutylammonium fluoride as solvent. By applying the minimum milling time required for complete dissolution, structurally unaltered wood or pulp could be further separated into lignin-carbohydrate fractions. These were analyzed by thioacidolysis. From eucalypt pulp, two different lignin-carbohydrate fractions were obtained, one glucan-and one xylan-enriched fraction, with the latter having more syringyl units in its lignin moieties. The developed solvent system seems to be universal because spruce and flax fibers and pulps could also be dissolved in it after milling.

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

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

  • 50. Lindfors, Eva-Lisa
    et al.
    Lindström, Mikael
    Iversen, Tommy
    Polysaccharide degradation in waterlogged oak wood from the ancient warship Vasa2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 1, p. 57-63Article in journal (Refereed)
    Abstract [en]

    A rather extensive degradation of cellulose and hemicelluloses was found in waterlogged oak wood samples from the ancient warship Vasa by size exclusion chromatography with the solvent system lithium chloride/ N,N-dimethylacetamide (LiCl/DMAc). The degradation has mainly occurred after salvage of the wreck, probably as a consequence of keeping iron contaminated wood in contact with air. The most likely explanation is Fenton type of reactions degrading the wood polymers and oxidising reduced sulphur forms to sulphuric acid. An increased degradation rate of the Vasa wood can be anticipated in the future if the sulphuric acid cannot be neutralised and the oxidative reactions cannot be quenched.

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