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  • 1.
    Almgren, Karin M.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Wood-fibre composites: Stress transfer and hygroexpansion2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood fibres is a type of natural fibres suitable for composite applications. The abundance of wood in Swedish forests makes wood-fibre composites a new and interesting application for the Swedish pulp and paper industry. For large scale production of composites reinforced by wood fibres to be realized, the mechanical properties of the materials have to be optimized. Furthermore, the negative effects of moisture, such as softening, creep and degradation, have to be limited. A better understanding of how design parameters such as choice of fibres and matrix material, fibre modifications and fibre orientation distribution affect the properties of the resulting composite material would help the development of wood-fibre composites.

    In this thesis, focus has been on the fibre-matrix interface, wood-fibre hygroexpansion and resulting mechanical properties of the composite. The importance of an efficient fibre-matrix interface for composite properties is well known, but the determination of interface properties in wood-fibre composites is difficult due to the miniscule dimensions of the fibres. This is a problem also when hygroexpansion of wood fibres is investigated. Instead of tedious single-fibre tests, more straightforward, macroscopic approaches are suggested. Halpin-Tsai’s micromechanical models and laminate analogy were used to attain efficient interface characteristics of a wood-fibre composite. When Halpin-Tsai’s model was replaced by Hashin’s concentric cylinder assembly model, a value of an interface parameter could be derived from dynamic mechanical analysis. A micromechanical model developed by Hashin was used also to identify the coefficient of hygroexpansion of wood fibres. Measurements of thickness swelling of wood-fibre composites were performed. Back-calculation through laminate analogy and the micromechanical model made it possible to estimate the wood-fibre coefficient of hygroexpansion. Through these back-calculation procedures, information of fibre and interface properties can be gained for ranking of e.g. fibre types and modifications.

    Dynamic FT-IR (Fourier Transform Infrared) spectroscopy was investigated as a tool for interface characterization at the molecular level. The effects of relative humidity in the test chamber on the IR spectra were studied. The elastic response of the matrix material increased relative to the motion of the reinforcing cellulose backbone. This could be understood as a stress transfer from fibres to matrix when moisture was introduced to the system, e.g. as a consequence of reduced interface efficiency in the moist environment. The method is still qualitative and further development is potentially very useful to measure stress redistribution on the molecular level.

  • 2.
    Almgren, Karin M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Characterization of interfacial stress transfer ability by dynamic mechanical analysis of cellulose fiber based composite materials2010In: Composite interfaces (Print), ISSN 0927-6440, E-ISSN 1568-5543, Vol. 17, no 9, p. 845-861Article in journal (Refereed)
    Abstract [en]

    The stress transfer ability at the fiber-matrix interface of wood fiber composites is known to affect the mechanical properties of the composite. The evaluation of interface properties at the level of individual fibers is however difficult due to the small dimensions and variability of the fibers. The dynamical mechanical properties of composite and constituents, in this case wood fibers and polylactide matrix, was here used together with micromechanical modeling to quantify the stress transfer efficiency at the fiber-matrix interface. To illustrate the methodology, a parameter quantifying the degree of imperfection at the interface was identified by inverse modeling using a micromechanical viscoelastic general self-consistent model with an imperfect interface together with laminate analogy on the composite level. The effect of moisture was assessed by comparison with experimental data from dynamic mechanical analysis in dry and moist state. For the wood fiber reinforced polylactide, the model shows that moisture absorption led to softening and mechanical dissipation in the hydrophilic wood fibers and biothermoplastic matrix, rather than loss of interfacial stress transfer ability.

  • 3.
    Almgren, Karin M.
    et al.
    Innventia.
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Berthold, Fredrik
    Innventia.
    Lindström, Mikael
    Innventia.
    Moisture uptake and hygroexpansion of wood fiber composite materials with polylactide and polypropylene matrix materials2009In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 30, no 12, p. 1809-1816Article in journal (Refereed)
    Abstract [en]

    Effects of butantetracarboxylic acid (BTCA) modification, choice of matrix, and fiber volume fraction on hygroexpansion of wood fiber composites have been investigated. Untreated reference wood fibers and BTCA-modified fibers were used as reinforcement in composites with matrices composed of polylactic acid (PLA), polypropylene (PP), or a mixture thereof. The crosslinking BTCA modification reduced the out-of-plane hygroexpansion of PLA and PLA/PP composites, under water-immersed and humid conditions, whereas the swelling increased when PP was used as matrix material. This is explained by difficulties for the BTCA-modified fibers to adhere to the PP matrix. Fiber volume fraction was the most important parameter as regards out-of-plane hygroexpansion, with a high-fiber fraction leading to large hygroexpansion. Fiber-matrix wettability during processing and consolidation also showed to have a large impact on the dimensional stability and moisture uptake. POLYM. COMPOS., 30:1809-1816, 2009.

  • 4. Almgren, Karin M.
    et al.
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Varna, Janis
    Luleå tekniska universitet, LTU.
    Contribution of wood fiber hygroexpansion to moisture induced thickness swelling of composite plates2010In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 31, no 5, p. 762-771Article in journal (Refereed)
    Abstract [en]

    One of the main drawbacks of wood fiber-based composite materials is their propensity to swell due to moisture uptake. Because the wood fibers are usually the main contributor to hygroexpansion, it is of interest to quantify the hygroexpansion coefficient of wood fibers, to compare and rank different types of fibers. This investigation outlines an inverse method to estimate the transverse hygroexpansion coefficient of wood fibers based on measurements of moisture induced thickness swelling of composite plates. The model is based on composite micromechanics and laminate theory. Thickness swelling has been measured on polylactide matrix composites with either bleached reference fibers or crosslinked fibers. The crosslinking modification reduced the transverse hygroexpansion of the composites and the transverse coefficient of hygroexpansion of the fibers was reduced from 0.28 strain per relative humidity for reference fibers to 0.12 for cross-linked fibers

  • 5.
    Andersson, Rasmus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Benchmarking of a Novel Hydrocyclone Design for Pulp FractionationManuscript (preprint) (Other academic)
  • 6.
    Andersson, Rasmus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Evaluation of two hydrocyclone designs for pulp fractionation2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The process conditions and fractionation efficiency of two hydrocyclone designs, a novel and a conventional conical design, were evaluated. The novel design comprised a modified inlet section, where the pulp suspension had to pass a narrow ring-shaped opening, and a very compact fractionation zone. The influence of feed concentration and fine fraction mass ratio was studied. The trials were performed with never-dried, unrefined bleached chemical softwood pulp. Fractionation efficiency was evaluated in terms of change of surface roughness of handsheets made out of the fractions and the feed pulp respectively.

    The fractionation efficiency increased considerably with decreasing fine fraction mass ratio, especially at higher feed concentrations. This finding prompted a hypothesis on the existence of a radial gradient in the composition of the suspension inside the novel hydrocyclone. Using the novel hydrocyclone in a feed-forward fractionation system would therefore prove to be more favourable as a larger total fine fraction of better properties can be obtained. A three-stage feed-forward fractionation system was evaluated in laboratory scale. Here, it was indeed possible to extract fine fractions with improved surface properties in each of the three consecutive stages. All three fine fractions had about the same surface roughness.

    The fractionation performance of the novel design was benchmarked against that of a conventional, best available technology (BAT) design. In terms of fractionation efficiency, the BAT design performed better. However, the fractions produced with the novel hydrocyclone had a much smaller difference in concentration, implying a much less pronounced enrichment of fines in the fine fraction. It is unclear, to what extent the lower share of latewood fibres and the increased fines content, respectively, contributed to the improved surface roughness of the fine fractions. However, it is clear that the lower enrichment of fines in the novel hydrocyclone makes it easier to install it in industrial applications without a need for auxiliary equipment to redistribute large water flows.

     

  • 7.
    Andersson, Rasmus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Vomhoff, Hannes
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Evaluation of a Multiple Feed-Forward Fractionation Approach Using a Novel Hydrocyclone DesignManuscript (preprint) (Other academic)
  • 8.
    Andersson, Rasmus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Vomhoff, Hannes
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Evaluation of a novel hydrocyclone for pulp fractionationManuscript (preprint) (Other academic)
  • 9.
    Ansari, Farhan
    et al.
    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.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lars, Berglund
    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.
    Strong surface treatment effects on reinforcement efficiency in biocomposites based on cellulose nanocrystals in poly(vinyl acetate) matrix2015In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 12, p. 3916-3924Article in journal (Refereed)
    Abstract [en]

    In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

  • 10.
    Antonsson, Stefan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strategies for improving kraftliner pulp properties2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    A large part of the world paper manufacturing consists of production of corrugated board components, kraftliner and fluting, that are used in many different types of corrugated boxes. Because these boxes are stored and transported, they are often subjected to changes in relative humidity. These changes together with mechanical loads will increase the deformation of the boxes compared to the case where the same loads are applied in a static environment. This enlarged creep due to the changes in relative humidity is called mechano-sorptive or accelerated creep. Mechano-sorptive creep forces producers to use high safety factors when designing boxes, and therefore, this is one of the key properties of kraftliner boards.

     

    Different strategies to decrease mechano-sorptive creep, and to simultaneously gain more knowledge about the causes for this phenomenon in paper, are the aim of this work. Derivatised and underivatised black liquor lignins, a by-product produced in pulp mills in large quantities, have been used together with biomimetic methods, to modify the properties of kraftliner pulp. Furthermore, the properties of kraftliner pulp have been compared to other pulps in order to evaluate the influence of fibre morphological factors, such as fibre width and shape factor, on the mechano-sorptive creep. In addition the influence of the chemical composition of the kraftliner pulp has been evaluated both by means of treating a kraftliner pulp with chlorite and xylanase and by producing pulps with different chemical composition.

     

    By using lignin and biomimetic methods, to create radical coupling reactions, it has been shown that it is possible to increase the wet strength of kraftliner pulp sheets. This method of treating the pulp showed, however, no significant effects on the mechano-sorptive creep. The addition of an apolar suberin-like lignin derivative, which has been shown to be possible to produce from natural resources, did show a positive effect on mechano-sorptive creep properties, but at the expense of stiffness properties in constant climate. Different pulps were compared with a kraftliner pulp and it was observed that the ratio between tensile stiffness and hygroexpansion can be used to estimate the mechano-sorptive creep properties. The hardwood kraft pulps investigated had lower hygroexpansion, probably due to more slender and straighter fibres, and higher tensile stiffness, probably due to lower lignin content. As the lignin content was varied by different methods in kraft pulps, it was observed that increased lignin content gives an increased hygroexpansion and decreased tensile stiffness as well as an increased mechano-sorptive creep. There were also indications of increased mechano-sorptive creep due to higher xylan content.

     

     

  • 11.
    Antonsson, Stefan
    et al.
    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.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The influence of lignin and xylan on some kraftliner pulp properties2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, p. 403-408Article in journal (Refereed)
    Abstract [en]

    This study investigates the influence of lignin and hemicellulose content on the mechanical and physical properties of softwood kraft liner pulp. Tensile properties, hygroexpansion, and mechano-sorptive creep properties were measured. The lignin and hemicellulose contents were modified by chlorite delignification and xylanase treatment.

    After treatment, the chemical composition of the pulps was 3-14% Klason lignin, 69-77% cellulose, 16-21% hemicellulose, and 4-7% xylan. In the tested pulps, low lignin content tended to decrease hygroexpansion as well as increase tensile stiffness and mechano-sorptive creep stiffness. Xylan contributed less to the pulp sheet properties, but at equal lignin contents, higher xylan content tended to give increased hygroexpansion and worse mechano-sorptive creep properties.

  • 12.
    Antonsson, Stefan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlström, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Applying a novel cooking technique to produce high kappa number pulps: the effects on physical properties2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, p. 415-420Article in journal (Refereed)
    Abstract [en]

    A recently developed kraft cooking technique, with a longer impregnation time at lower temperatures to facilitate diffusion over consumption of active cooking chemicals, makes it possible to produce kraftliner pulp without inline refining. This technique was applied to prepare two pulps with different lignin contents, which were compared with two industrial pulps from conventional kraft cooks in order to evaluate the physical properties of the pulps.

    It was demonstrated that pulps with lower lignin content can increase tensile stiffness, decrease hygroexpansion, and decrease the mechano-sorptive creep of handsheets. However, no difference in SCT and tensile energy absorption values due to different lignin contents was observed. It was further demonstrated that pulps made with Extended Impregnation Cooking (EIC) results in straighter pulp fibres with higher cellulose content. These pulps tended to have lower mechano-sorptive creep than conventional pulps. A higher brightness of the pulp sheets can also be obtained by choosing a higher alkali profile.

  • 13.
    Antonsson, Stefan
    et al.
    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.
    Mäkelä, Petri
    Innventia AB.
    Fellers, Christer
    Innventia AB.
    Lindström, Mikael E.
    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.
    Comparison of the physical properties between hardwood and softwood pulps2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, p. 409-414Article in journal (Refereed)
    Abstract [en]

    High mechano-sorptive creep resistance, i.e., good creep resistance in environments with changing relative humidity, is one of the key requirements for linerboards. The aim of this study was to investigate the influence of pulp types and pulp properties on the mechano-sorptive creep of kraftliner. A high-yield softwood, kraftliner pulp, and four different hardwood pulps were investigated. The physical properties of laboratory sheets were evaluated, with emphasis on the mechano-sorptive creep properties.

    The results showed that the density increase due to increased beating significantly improved the tensile stiffness of all pulps, while its effect on the isocyclic creep stiffness was less pronounced. The hardwood pulps showed higher tensile stiffness, better mechano-sorptive creep properties, and lower hygroexpansion than the softwood pulp at a given density. However, the softwood pulp did exhibit better tensile strength and fracture toughness properties than the hardwood pulps.

    The results imply that hardwood pulps can be competitive with softwood pulps in kraftliners, provided that their tensile strength and fracture toughness properties can be improved by, for example, chemical means. Furthermore, the isocyclic creep stiffness correlates with the ratio of tensile stiffness to hygroexpansion, indicating that this ratio can be used for engineering estimates of the mechano-sorptive creep performance of paper materials.

  • 14.
    Antonsson, Stefan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Pulkkinen, Iiro
    Chemical Engineering, Department of Biotechnology and Chemical Technology, Helsinki University of Technology (TKK), Espoo, Finland.
    Fiskari, Juha
    Metsä-Botnia, Joutseno Mill, Lappeenranta, Finland.
    Karlström, Katarina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The relationship between hygroexpansion, tensile stiffness, and mechano–sorptive creep in bleached hardwood kraft pulps2010In: Appita journal, ISSN 1038-6807, Vol. 63, no 1, p. 231-Article in journal (Refereed)
    Abstract [en]

    Hygroexpansion coefficient and tensile stiffness are important parameters in many paper applications. This study compares several bleached industrial hardwood kraft pulps, comprising five eucalypt pulps from South America, Europe, and Africa as well as an acacia pulp from Asia and a birch pulp from Scandinavia. Refined and unrefined pulps are compared. The results indicate significant differences in hygroexpansion but smaller differences in tensile stiffness index at comparable densities. No single factor offering a reasonable explanation of these differences in hygroexpansion coefficient, such as carbohydrate composition, fibre dimensions, or fibre form, was found. However, correlation between hygroexpansion coefficient and the mechano-sorptive creep stiffness was observed. We suggest that the hygroexpansion coefficient at a given tensile stiffness level can be used to rank pulps in terms of their mechano-sorptive creep properties.

  • 15.
    Areskogh, Dimitri
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Structural Modifications of Lignosulphonates2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lignosulphonates are by‐products from the sulphite pulping process for the manufacture ofspecialty dissolving pulps and paper. During the liberation of the cellulose, the lignin isfractionated and solubilised through covalent addition of sulphonic acid groups at variouspositions in the structure. The formed sulphonated lignin, lignosulphonate is then furtherisolated and refined.

    The amphiphilic nature of lignosulphonates has enabled them to be used as additives to varioussuspensions to improve their dispersion and stability. The by far largest utilisation oflignosulphonates is as dispersants in concrete. Here, lignosulphonates act by dispersing cementparticles to prevent flocculation, un‐even particle distribution and reduced strengthdevelopment. The dispersion is achieved through steric and electrostatic repulsion of the cementparticles by the lignosulphonate polymer. This behaviour is intimately linked with the overallsize and amount of charged groups in the dispersing polymer. Traditional modifications oflignosulphonates have been limited to removal of sugars, filtration and fractionation. Thesemodifications are not sufficient for utilisation of lignosulphonates in high‐strength concrete. Heresynthetic dispersants and superplasticisers are used which are considerably more efficient evenat low dosages. To compete with these, additional modifications of lignosulphonates are likely tobe necessary. The molecular weight and functional group composition have been identified anddescribed as the most interesting parameters that can be modified.

    Currently, no suitable method exists to increase the molecular weight of lignosulphonates.Oxidation by the natural radical initiating enzyme laccase is an interesting tool to achieve suchmodifications. In this thesis several aspects of the mechanism through which this enzyme reactswith lignin and lignosulphonate structures have been elucidated through model compoundstudies. Further studies showed that laccase alone was a highly efficient tool for increasing themolecular weight of commercial lignosulphonates at low dosages and in short incubation times.Immobilisation of the laccase to a solid support to enable re‐utilisation was also investigated.

    Modification of functional group composition of lignosulphonates was achieved throughozonolysis and the Fenton’s reagent, a mixture of hydrogen peroxide and iron(II)acetate.Introduction of charged carboxylic groups was achieved through opening of the benzyl rings oflignosulphonates. It was found that a two‐stage process consisting of laccase oxidation followedby ozonolysis was an efficient technique to create a polymer enriched with carboxylic acidgroups with a sufficient molecular size.

    Oxidation by the Fenton’s reagent was shown to yield similar modifications as the combinedlaccase/ozonolysis treatment albeit with less pronounced results but with a large level of controlthrough variation of a number of reaction parameters. The Fenton’s reagent can therefore be aninteresting alternative to the aforementioned two‐stage treatment.

    These modifications are interesting for large‐scale applications not only because of theirsimplicity in terms of reaction parameters but also because of the ubiquity of the used enzymeand the chemicals in the pulp and paper industry.

  • 16.
    Areskogh, Dimitri
    et al.
    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.
    Fenton's reaction: a simple and versatile method to structurally modify commercial lignosulphonates2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, no 1, p. 90-98Article in journal (Refereed)
    Abstract [en]

    Treatment of lignosulphonates with hydrogen peroxide and Fe (II) acetate under mild conditions can be used to increase the molecular weight and content of carboxylic acids. Such Fenton's oxidation can produce, in some of the conditions of and lignosulphonate concentration, a two-fold increase in the molecular weight and a 6-7 fold increase in the carboxylic acid content. The structural modifications of lignosulphonate may increase the technical performance of the product in several applications. Possible reaction mechanisms of the Fenton system are proposed and discussed.

  • 17.
    Areskogh, Dimitri
    et al.
    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.
    Immobilisation of laccase for polymerisation of commercial lignosulphonates2011In: Process Biochemistry, ISSN 1359-5113, E-ISSN 1873-3298, Vol. 46, no 5, p. 1071-1075Article in journal (Refereed)
    Abstract [en]

    The oxidoreductive enzyme laccase has previously been shown to be able to increase the average molecular weight of lignosulphonatesthrough generation of phenoxy radicals on end groups and the subsequent radical-radical coupling reactions that cross-link individual lignosulphonate molecules. Utilisation of laccases for this purpose is a potential industrial process not only to improve the properties of technical lignosulphonates but also to expand their utilisation to new areas. Immobilisation of the laccase is an interesting technique to enable reusage of the enzyme and thus reduce costs involved with such process. In this work, we demonstrate the potential of immobilised laccase to polymerise technical lignosulphonates. A number of factors that limits re-utilisation of the immobilised catalyst such as lignosulphonate adsorption onto the carrier and laccase deactivation have been identified and are discussed. However, by using a low-porosity support and lower reaction temperatures these problems can be limited.

  • 18.
    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.
    Gellerstedt, Göran
    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.
    Investigation of the Molecular Weight Increase of Commercial Lignosulfonates by Laccase Catalysis2010In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 4, p. 904-910Article in journal (Refereed)
    Abstract [en]

    Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed.

  • 19.
    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.
    Gellerstedt, Göran
    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.
    Structural modification of commercial lignosulphonates through laccase catalysis and ozonolysis2010In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 32, no 3, p. 458-466Article in journal (Refereed)
    Abstract [en]

    Lignosulphonates are by-products from the sulphite pulping process, in which lignin is separated from cellulose by the addition of sulphonic acid groups to the alpha-position of lignin, thereby increasing the solubility of lignin in water. The predominant industrial utilisations of lignosulphonates are as dispersants, plasticisers and water-reducing agents in concrete preparation. The ability of lignosulphonates to function as a good plasticisers and water reducers is intimately linked with the purity of the lignosulphonate, its molecular weight and the number of charged groups present in the macromolecule. Currently, lignosulphonates are outrivaled by synthetic plasticisers termed superplasticisers due to their superior properties when used as additives to high-strength concrete. If lignosulphonates are to successfully compete with these superplasticisers, significant modifications are required. This paper describes a two-stage treatment of lignosulphonates in which the molecular weight is increased through laccase oxidation and carboxylic groups are introduced through ozonolysis. The technical significance of the results is also discussed.

  • 20.
    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.

  • 21.
    Areskogh, Dimitri
    et al.
    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.
    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.
    Sipilä, Jussi
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sulfonation of phenolic end groups in lignin directs laccase-initiated reactions towards cross-linking2010In: Industrial Biotechnology, ISSN 1550-9087, E-ISSN 1931-8421, Vol. 6, no 1, p. 50-59Article in journal (Refereed)
    Abstract [en]

    The effect of sulfonation of the a-carbon on model compounds representing phenolic end groups on lignin was studied with respect to the reactions initiated by oxidation of laccase, by mass spectrometry. Sulfonation seems to direct the reactions towards formation of 5-5´ and 4-O-5´ bonds, avoiding formation of 1-O-4´ bonds and oxidation of the a-carbon. This, in turn, will facilitate cross-linking reactions between lignin molecules. Sulfonation therefore has potential as an industrial pretreatment prior to laccase treatment for various wood-containing materials.

  • 22.
    Arnling Bååth, Jenny
    et al.
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Giummarella, Nicola
    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.
    Klaubauf, Sylvia
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Lawoko, Martin
    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.
    Olsson, Lisbeth
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    A glucuronoyl esterase from Acremonium alcalophilum cleaves native lignin-carbohydrate ester bonds2016In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 590, no 16, p. 2611-2618Article in journal (Refereed)
    Abstract [en]

    The Glucuronoyl esterases (GE) have been proposed to target lignin-carbohydrate (LC) ester bonds between lignin moieties and glucuronic acid side groups of xylan, but to date, no direct observations of enzymatic cleavage on native LC ester bonds have been demonstrated. In the present investigation, LCC fractions from spruce and birch were treated with a recombinantly produced GE originating from Acremonium alcalophilum (AaGE1). A combination of size exclusion chromatography and 31P NMR analyses of phosphitylated LCC samples, before and after AaGE1 treatment provided the first evidence for cleavage of the LC ester linkages existing in wood.

  • 23. Axegard, Peter
    et al.
    Bergnor, Elisabeth
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ekholm, Ulrika
    Bleaching of softwood kraft pulps with H2O2, O3, and ClO21996In: TAPPI Journal, ISSN 0734-1415, Vol. 79, no 1, p. 113-119Article in journal (Refereed)
    Abstract [en]

    Ozone or chlorine dioxide bleaching prior to hydrogen peroxide bleaching greatly improves the performance of the hydrogen peroxide stage. The efficiency is further improved by a chelating treatment immediately after the ozone or chlorine dioxide stage. With an optimal metal ion profile, laboratory bleached (OAZQP) softwood kraft pulps can reach brightness levels above 90% ISO, with 5-10% lower pulp strength properties and bleaching costs comparable to ECF bleaching. It also is possible to obtain full brightness with only hydrogen peroxide provided the metal ion profile is optimal, e.g., by using multiple QP treatments. The chemical consumptions, expressed as oxidation equivalents per decreased kappa number are the same as for sequences including ozone or chlorine dioxide. Ozone and chlorine dioxide are comparable as far as delignification and brightness efficiency go.

  • 24. Axegård, Peter
    et al.
    Bergnor, Elisabeth
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ekholm, Ulrika
    The role of metal ions in TCF-bleaching of softwood kraft pulps.: Vol.31994In: Proceedings Tappi Pulping conf., 1994, p. 1161-1167Conference paper (Refereed)
  • 25. Axelsson, P.
    et al.
    Berggren, R.
    Berthold, F.
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Molecular mass distributions of lignin and lignin-carbohyd rate complexes in birch Kraft pulps: Changes caused by the conditions in the cook and their relation to unbleached pulp brightness and bleachability2005In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 31, no 1, p. 19-27Article in journal (Refereed)
    Abstract [en]

    Lignin-carbohydrate complexes and their relationship to pulp bleachability and unbleached pulp brightness were studied in four birch kraft pulps produced at high and low hydroxide ion and sodium ion concentrations, using size-exclusion chromatography (SEC). About 75-80%of the lignin was found to be associated with carbohydrates, a larger part with hemicelluloses and a smaller part with cellulose. Easily bleached pulps, produced under high [OH-] or low [Na+] conditions, had more lignin associated with cellulose than their counterparts. Furthermore, a high [OH-] gave a residual lignin that was significantly more accessible in the residual lignin isolation, and where the inaccessible lignin was bonded to carbohydrates. Colour differences of pulps caused by variations in the cooking conditions, as studied in the SEC system, were associated with all the lignin, irrespective of whether it was associated with hemicelluloses or cellulose.

  • 26. Axelsson, Patrik
    et al.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Teder, Ants
    Bleachability of Alkaline Birch Pulps.2000In: Proceedings 6th European Workshop on Lignocellulosics and Pulp., 2000Conference paper (Refereed)
  • 27. Axelsson, Patrik
    et al.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Teder, Ants
    Influence of alkali profile in the kraft cook on the bleachability of birch.2001In: : Book:Vol I, 2001, p. 41-44Conference paper (Refereed)
  • 28.
    Azhar, Shoaib
    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.
    Extraction of Polymeric Hemicelluloses from Spruce Wood2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hemicelluloses are one of the three main components of spruce wood and constitute about 20% of the wood material. During mechanical pulping, 5–10% of the hemicelluloses are accumulated in waste waters, whereas during chemical pulping 70–80% of the hemicelluloses are lost in process liquors. The concept of integrated forest biorefinery involves the development of methods to extract these hemicelluloses prior to pulping in order to produce value-­added products besides pulp. This thesis describes some of the feasible possibilities of extracting hemicelluloses from wood at a high molecular weight prior to pulping in addition to presenting a deeper understanding of their degradation under mild treatment conditions.

    A major obstacle for the efficient extraction of hemicelluloses is the recalcitrance due to the network of lignin and polysaccharides. This network can be loosely opened by the use of enzymes and this improves the extraction of hemicelluloses. A chemical impregnation of the wood chips was performed to enhance the accessibility of the cell wall to enzymes. The ability of different additives to stabilize the hemicelluloses against peeling during the alkaline impregnation stage was also investigated in order to obtain a better yield in subsequent extraction.

    Increasing the surface area and decreasing the mass transport length could also improve the yield of hemicelluloses extracted from wood. This was achieved with a mild mechanical pre-­treatment of wood chips using an impressafiner and a fiberizer. Polymers mainly consisting of galactoglucomannan with an average molecular weight of 30 kDa were extracted from fiberized wood with water.

    Different pre-­treatment and extraction methods were combined to demonstrate the concept of material biorefinery based on wood.

    The kinetics of degradation of spruce galactoglucomannan were studied under alkaline conditions. It was degraded in two phases at two different rates. A kinetic model was developed to fit the experimental data and to estimate the activation energies. 

  • 29.
    Azhar, Shoaib
    et al.
    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.
    Henriksson, Gunnar
    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.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Lindström, Mikael
    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.
    Extraction of hemicelluloses from fiberized spruce wood2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 117, p. 19-24Article in journal (Refereed)
    Abstract [en]

    A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses. 

  • 30. Badia, J. D.
    et al.
    Kittikorn, Thorsak
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Santonja-Blasco, L.
    Martizez-Felipe, A.
    Ribes-Greus, A.
    Ek, Monica
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Water absorption and hydrothermal performance of PHBV/sisal biocomposites2014In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, p. 166-174Article in journal (Refereed)
    Abstract [en]

    The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment.

  • 31. 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.

  • 32.
    Berglund, Per
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Högfeldt, Anna-Karin
    KTH, School of Education and Communication in Engineering Science (ECE), Learning.
    Karlsson, Sara
    KTH.
    Klasén, Ida
    KTH, School of Education and Communication in Engineering Science (ECE).
    Sandberg, Teresia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Utvärdering för utveckling: KTH:s samtliga utbildningar under belysning2011Conference paper (Other academic)
  • 33. Bergnor, Elisabeth
    et al.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Johansson, E
    The role of metal ions in TCF-bleaching.1994In: Proceedings 3rd European Workshop on Lignocellulosics and Pulp, 1994, p. 284-289Conference paper (Refereed)
  • 34.
    Bi, Ran
    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.
    Lignocellulose Degradation by Soil Micro-organisms2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lignocellulosic biomass is a sustainable resource with abundant reserves. Compared to petroleum ‐ based products, the biomass ‐ derived polymers and chemicals give better environmental profiles. A lot of research interest is focused on understanding the lignocellulose structures.

    Lignin, among the three major wood components, represents most difficulty for microbial degradation because of its complex structure and because cross ‐ linking to hemicellulose makes wood such a compact structure. Nevertheless, wood is naturally degraded by wood ‐ degrading micro ‐ organisms and modified and partly degraded residual of lignin goes into soil. Therefore soil serves as a good environment in which to search for special lignin ‐ degraders. In this thesis, different types of lignin have been used as sole carbon sources to screen for lignin ‐ degrading soil micro ‐ organisms. Eleven aerobic and three anaerobic microbe strains have been isolated and identified as able to grow on lignin. The lignin degradation patterns of selected strains have been studied and these partly include an endwise cleavage of  β‐ O ‐ 4 bonds in lignin and is more complex than simple hydrolytic degradation.

    As lignin exists in wood covalently bonded to hemicellulose, one isolated microbe strain, Phoma herbarum, has also been studied with regards to its ability to degrade covalent lignin polysaccharide networks (LCC). The results show that its culture filtrate can attack lignin ‐ polysaccharide networks in a manner different from that of the commercial enzyme product, Gammanase, possibly by selective cleavage of phenyl glucoside bonds. The effects on LCC of Phoma herbarum also enhance polymer extractability. Hot ‐ water extraction of a culture filtrate of Phoma herbarum ‐ treated fiberized spruce wood material gave an amount of extracted galactoglucomannan more than that given by the Gammanase ‐ treated material and non ‐ enzyme ‐ treated material.

    Over millions of years of natural evolution, micro ‐ organisms on the one hand develop so that they can degrade all wood components to get energy for growth, while plants on the other hand also continuously develop to defend from microbial attack. Compared with lignin and cellulose, hemicelluloses as major components of plant cell walls, are much more easily degraded, but hemicelluloses differ from cellulose in that they are acetylated to different extents. The biological functions of acetylation are not completely understood, but it is suggested is that one function is to decrease the microbial degradability of cell walls. By cultivation of soil micro ‐ organisms using mannans acetylated to deffernent degrees as sole carbon source on agar plates, we were able to see significant trends where the resistance towards microbial degradation of glucomannan and galactomannan increased with increasing degree of acetylation. Possible mechanisms and the technological significance of this are discussed. Tailoring the degree of acetylation of polysaccharide materials might slow down the biodegradation, making it possible to design a material with a degradation rate suited to its application.

  • 35.
    Bi, Ran
    et al.
    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.
    Azhar, Shoaib
    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.
    Mckee, Lauren
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    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.
    Culture Filtrates from a Soil Organism Enhances Extractability of Polymers from Fiberised Spruce WoodManuscript (preprint) (Other academic)
  • 36.
    Bi, Ran
    et al.
    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.
    Berglund, Jennie
    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.
    Vilaplana, Francisco
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    McKee, Lauren
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    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.
    The Degree Of Acetylation Affects The Microbial Degradability Of HemicellulosesManuscript (preprint) (Other academic)
  • 37.
    Bi, Ran
    et al.
    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.
    Henriksson, Gunnar
    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.
    Isolation and identification of soil microorganisms under anaerobic condition which is able to live on lignin as carbon source2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Article in journal (Other academic)
  • 38.
    Bi, Ran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Huang, Shan
    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.
    ISOLATION OF EXCEEDINGLY LOW OXYGEN CONSUMING FUNGAL STRAINS ABLE TO UTILIZE LIGNIN AS CARBON SOURCE2016In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 50, no 7-8, p. 811-817Article in journal (Refereed)
    Abstract [en]

    Lignin biodegradation is normally related to aerobic microorganisms, and it is often claimed that microbes do not metabolize lignin as a carbon source. In this work, several fungal strains were isolated from the sediment of a small stream located in a forest and tested on agar plates with lignin as the only carbon source. All identified strains were Ascomycetes, Penicillium spinulosum, Pseudeurotium bakeri and Galactomyces geotrichum. When cultivated in shaking flasks with lignosulphonate as a carbon source, the lignin was consumed, and cell free culture filtrates appeared to depolymerize lignosulphonate to some extent. It is suggested that the strains detected are part of a symbiotic community and live in a microbiological niche in which they are able to utilize lignin residues left from brown rot and humus having extremely low oxygen content.

  • 39.
    Bi, Ran
    et al.
    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.
    Huang, Shan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. Linnaus University, Sweden.
    Henriksson, Gunnar
    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.
    Isolation of exceedingly low oxygen consuming fungal strains able to utilize lignin as carbon sourceIn: Cellulose Chemistry and Technology, ISSN 0576-9787Article in journal (Refereed)
  • 40.
    Bi, Ran
    et al.
    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.
    Lawoko, Martin
    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.
    Henriksson, Gunnar
    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.
    Phoma herbarum, a soil fungus able to grow on natural lignin and synthetic lignin (DHP) as sole carbon source and cause lignin degradationManuscript (preprint) (Other academic)
  • 41.
    Bi, Ran
    et al.
    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.
    Oinonen, Petri
    Ecohelix AB, Teknikringen 38, 10044 Stockholm, Sweden.
    Wang, Yan
    Henriksson, Gunnar
    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.
    A Method for Studying Effects on Lignin-Polysaccharide Networks during Biological Degradation and Technical Processes of Wood2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 1, p. 1307-1318Article in journal (Refereed)
    Abstract [en]

    Woody tissues consist primarily of a mixture of cellulose, hemicelluloses, and lignin. Covalent bonds between lignin and polysaccharides likely play a central role in determining the mechanical and physical properties of wood. Intact and defined lignin-polysaccharide networks have not been isolated in large quantities because of the recalcitrance of lignin, which demands harsh chemical treatments that alter its structure. This report presents a method for preparing large quantities of lignin-polysaccharide networks similar to those naturally present in wood based on the enzymatic oxidation of hemicellulose from Norway spruce. Fungal enzymes produced from various carbon sources were used to depolymerize these networks. The method was used for simulating "enzyme mining" - a concept in biorefineries, giving a possible explanation for its mechanisms.

  • 42.
    Bi, Ran
    et al.
    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.
    Oinonen, Petri
    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.
    Wang, Yan
    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.
    Henriksson, Gunnar
    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.
    A method for studying effects on lignin-polysaccharide networks during degradation and technical processing of woodManuscript (preprint) (Other academic)
  • 43.
    Bi, Ran
    et al.
    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.
    Spadiut, Oliver
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    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.
    Isolation and identification of microorganisms from soil able to live on lignin as acarbon source and to produce enzymes which cleave the β-o-4 bond in a lignin model compound2012In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 46, no 3-4, p. 227-242Article in journal (Refereed)
    Abstract [en]

    Several strains of fungi were isolated and identified from Scandinavian soil using agar plates with lignin as a carbon source. The strains grew significantly faster on this medium than on control plates without lignin. Different types of technical lignins were used, some of which contained trace amounts of sugars, even if the increased growth rate seemed not related to the sugar content. Some strains were cultivated in shaking flask cultures with lignin as a carbon source, with lignin apparently consumed by microbes - while accumulation of the microorganism biomass occurred. The cell-free filtrates of these cultures could reduce the apparent molecular weights of lignosulphonates, while the culture filtrate of one strain could cleave the beta-O-4 bond in a lignin model compound.

  • 44.
    Bi, Ran
    et al.
    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.
    Spadiut, Oliver
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brumer, Harry
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    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.
    Isolation and identification of microorganisms from soil able to live on lignin as a carbon source and to produce enzymes which cleave beta-O-4 bond in a lignin model compound2012In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 46, no 3-4, p. 227-242Article in journal (Refereed)
    Abstract [en]

    Several strains of fungi were isolated and identified from Scandinavian soil using agar plates with lignin as a carbon source. The strains grew significantly faster on this medium than on control plates without lignin. Different types of technical lignins were used, some of which contained trace amounts of sugars, even if the increased growth rate seemed not related to the sugar content. Some strains were cultivated in shaking flask cultures with lignin as a carbon source, with lignin apparently consumed by microbes - while accumulation of the microorganism biomass occurred. The cell-free filtrates of these cultures could reduce the apparent molecular weights of lignosulphonates, while the culture filtrate of one strain could cleave the beta-O-4 bond in a lignin model compound.

  • 45.
    Bohn Lima, Raquel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Establishment of ligning and other bio-renewable materials as fuels and material developments for better performance for fuel cell technology2014Doctoral thesis, comprehensive summary (Other academic)
  • 46.
    Bohn Lima, Raquel
    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.
    Brouwe, Jack
    Modeling and studies in direct carbon-biomass fuel cell for power generation2013In: Abstracts of Papers, 245th ACS National Meeting & Exposition, New Orleans, LA, United States, April 7-11, 2013, 2013, p. ENFL-526-Conference paper (Other academic)
    Abstract [en]

    Several factors such as the global energy supply security and the need for generating efficient and clean energy have increased the interest in the research related to alternative fuel and energy systems.  Among these alternative systems, the biomass-​fuelled integrated Direct Carbon Fuel Cell (DCFC) with solid oxide fuel cell (SOFC)​/molten carbonate fuel cell (MCFC) systems have been identified as one of key energy technologies for the future since it combines the merits of renewable energy sources and carbon​/hydrogen energy systems.The modeling of energy systems plays a crucial role in the estn. of the performance and selection of the configuration and the operation parameters of these systems.  In the case of integrated DCFC - SOFC​/MCFC systems, there are many aspects that should be considered for a complete and robust model.  The lack of such a model for integrated DCFC - SOFC​/MCFC and biomass systems in the literature have been the main motivation for this study.

  • 47.
    Bohn Lima, Raquel
    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.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ceria-carbonates nanocomposite electrolyte for lignin based fuel cell2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Article in journal (Other academic)
  • 48.
    Brodin, Ida
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ernstsson, Marie
    YKI.
    Sjöholm, Elisabeth
    Innventia.
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Oxidative stabilisation of kraft lignin for carbon fibre production2012In: Holzforschung, ISSN 0018-3830, Vol. 66, p. 141-147Article in journal (Refereed)
    Abstract [en]

    With the aim of investigating kraft lignin as a raw material for carbon fibre production, different lignins have been stabilised in air at conditions varied according to a full factorial experimental design. The lignins under examination were purified kraft lignin powders originating from birch, spruce/pine and Eucalyptus globules, as well as lignin fibres originating from birch with 5% poly(ethylene oxide) (PEO) added as a plasticiser. The influence of temperature, time and heating rate on yield and glass-transition temperature (Tg) was investigated. The highest yield was achieved after stabilisation at 280C during 2 h with a heating rate of 0.2C min-1. The Tg of all lignin powders was increased when stabilisation occurred under harsher conditions. X-ray photoelectron spectroscopy analysis (XPS) of both the outer surface and the cleaved cross-section of individual lignin/PEO fibres showed a clear gradient in the degree of chemical modification, with the major change occurring on the surface resulting in the appearance of a skin-core structure after stabilisation. The behaviour of the lignin fibres during stabilisation is similar to that of pitch-based fibres, indicating good possibilities for lignin as raw material for carbon fibre production.

  • 49.
    Brännvall, Elisabet
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Aspects on Strenght Delivery and Higher Utilisation of the Strength Potential of Kraft Pulp Fibres2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Studies on strength delivery and related fields have so far concentrated on finding the locations in the mill where fibres are damaged and what the damages consist of. However, fibres will invariably encounter mechanical stresses along the fibreline and in this thesis a new concept is introduced; the vulnerability of fibres to mechanical treatment. It is hypothesised that fibres with different properties have different abilities to withstand the mechanical forces they endure as they are discharged from the digester and transported through valves, pumps and various washing and bleaching equipment.

    In the thesis, results are presented from trials where pulps with significantly different hemicellulose compositions were high-intensity mixed at pH 13, 70°C and 10% pulp consistency and pulp strength evaluated. By varying alkalinity and temperature, pulps with different carbohydrate composition could be obtained. High alkali concentration and low temperature resulted in high glucomannan content and low xylan content, whereas cooking at low alkali concentration and high temperature rendered a pulp with low glucomannan and high xylan content. The high alkalinity pulp was stronger, determined as tear index at given tensile index. The pulp viscosity was also higher for this pulp. However, when the pulps were subjected to high-intensity mixing, the high alkalinity pulp lost in tear strength and the re-wetted zero-span tensile strength was substantially reduced. The pulp cooked at high alkalinity was thus interpreted as being more vulnerable to mechanical treatment than the pulp obtained by cooking at low alkalinity.

    Another pair of pulps was manufactured at high and low sodium ion concentrations, but otherwise with similar chemical charges. The pulp obtained by cooking at low sodium ion concentration became stronger, evaluated as tear index at a given tensile index and the curl index was substantially lower, 8% compared to 12% for the pulp cooked at a high sodium ion concentration. The viscosity was 170 ml/g higher for the pulp manufactured at low sodium ion concentration. When the pulps were subjected to high-intensity mixing, the tear strength of the pulp manufactured at high sodium ion concentration was reduced. The re-wetted zero-span tensile index decreased also after mixing. The pulp obtained by cooking at higher sodium ion concentration was thus interpreted as being more vulnerable to mechanical treatment than the pulp manufactured at lower sodium ion concentration.

    In the thesis, two reasons for the low strength delivery of industrially produced pulps compared to laboratory-cooked pulps are put forward. Since the ionic strength of mill cooking liquor systems is much higher than is normally used in laboratory cooking, this can partly explain the difference in strength between mill- and laboratory-cooked pulp. A higher sodium ion concentration was shown in this thesis work to give a pulp of lower strength. Secondly, it is suggested that the difference in retention time of the black liquor in laboratory cooking and continuous mill cooking systems can explain the difference in tensile strength between laboratory-cooked and mill-produced pulp. The black liquor in a continuous digester has a longer retention time in the digester than the chips. This gives a longer time for the dissolved xylan to degrade and, as a consequence, the xylan deposited on the mill pulp fibres will be more degraded than the xylan deposited on the laboratory-cooked pulp fibres.

    In the thesis, results are also presented from studies using different strength-enhancing chemicals. The fibre surfaces of bleached never-dried and once-dried pulp were modified by the polyelectrolyte multilayer technique using cationic and anionic starch. Although the pulps absorbed the same amount of starch, the never-dried pulp reached a higher tensile index than the once-dried pulp. When the starch-treated never-dried pulp was dried and reslushed it still had higher tensile index than the never-dried untreated pulp. The starch layers were thus able to counteract part of the hornification effect. The never-dried starch treated pulps were subsequently dried, reslushed and beaten. Pulp with starch layers had a better beatability evaluated as the tensile index obtained after given number of PFI revolutions than dried untreated pulp. Hence, there is a potential to increase the tensile index of market pulp by utilising the polyelectrolyte multilayer technique before drying. Addition of CMC to bleached mill pulp and laboratory-cooked pulp increased the tensile strength to the same degree for both pulps. CMC addition had a straightening effect on the fibres, the shape factor increased and this increased the zero-span tensile strength also.

  • 50.
    Brännvall, Elisabet
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Jansson, Zheng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Characterisation of dissolved spruce xylan in kraft cooking2011In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, no 4, p. 380-385Article in journal (Refereed)
    Abstract [en]

    Xylan dissolved during kraft cooking and later redeposited on fibre surfaces has been demonstrated to affect paper strength properties. Earlier studies have demonstrated that it is the xylan characteristics, rather than simply the amount of xylan, that influence the strength-enhancing effect of xylan. To use xylan optimally, it is useful to understand xylan’s beneficial characteristics and how cooking conditions affect them.

    In this study, spruce chips were kraft cooked under various cooking conditions and the xylan in the black liquor was characterized. We found that dissolved spruce xylan had a much higher amount of bound lignin than found in previous studies of xylan dissolved from hardwoods. The ionic strength of the cooking liquor affected the amount of dissolved xylan as well as the uronic acid content of the xylan.

1234567 1 - 50 of 349
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