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  • 1. Al-Dajani, W. W.
    et al.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    On the isolation and structure of softwood residual lignins2002Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, nr 2, s. 193-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Different softwood residual lignins were isolated by acid hydrolysis of kraft and soda Pulps. Complete isolation of lignin Could not be achieved in one hydrolysis step. The yield of lignin varied between 35 and 55%. A more acidic, second hydrolysis step was therefore necessary to isolate almost all the lignin remaining in the Pulp residue, giving a total lipin yield of 91%. Alkaline extraction of the pulp was almost as efficient as acid hydrolysis in isolating residual lignins. However, alkaline extraction gave less pure lignin fractions and there was a clear indication of the existence of lignin-carbohydrate bonds. Pine wood meal was acid-hydrolyzed in the same way as the pulps. After two-stage acid hydrolysis, the combined lignin yield was only 45% of the Klason lignin content, which means that native lignin is more difficult to isolate front wood than residual lignin front a chemical pulp. It is Concluded that the difficulty encountered in isolating residual lignin by acid hydrolysis is a problem of limited accessibility due to a complex carbohydrate network surrounding the lignin.

  • 2.
    Ali, Silvia
    et al.
    STFI-Packforsk, Stockholm, Sweden .
    Salmén, Lennart
    From wood shavings to mechanical pulp - a new raw material?2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, ISSN 0283-2631, Vol. 20, nr 4, s. 418-422Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood chips used in the thermomechanical pulping (TMP) process were originally designed to suit the chemical pulping process. The production of small wood pieces more suitable for the TMP process could lead to an energy saving in this energy-intensive process. This paper discusses the potential benefits of using wood shavings instead of chips as the raw material for TMP production. In some exploratory trials, wood shavings with a thickness of about 2 mm and wood chips were refined in two steps under normal TMP process conditions in a pilot refiner. The first-stage refining was performed under pressurized conditions at 130°C. The second-stage refining was performed at atmospheric pressure at approximately 100°C at four different energy levels. The quality of the pulp produced from wood shavings was found to be better than that of the pulp produced from wood chips, with respect to both strength properties (except tear index) and optical properties at comparable energy levels. The potential for energy savings at a given tensile index using wood shavings instead of the traditional chips is estimated to be about 25%.

  • 3. Alm, Hajer Kamal
    et al.
    Ström, Göran
    Karlström, Katarina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Effect of excess dispersant on surface properties and liquid interactions on calcium carbonate containing coatings2010Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, nr 1, s. 82-92Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to identify what effects excess amount of sodium polyacrylate, a commonly used dispersant, has on the coating properties and the interaction between ink and the paper coating in offset printing. Since polyacrylate strongly interacts with calcium ions, soluble calcium salt was added to some coating colours to illustrate the impact of charge neutralization by calcium ions. It was found that the coating structure was only slightly affected by the extra addition of polyacrylate, showing some weak flocculation, whereas the surface chemistry was strongly influenced. The coatings became more polar and interacted more strongly with water. This resulted in slower ink setting and reduced ink-paper coating adhesion, especially in the presence of applied water/dampening solution, which are identified as contributory factors in ink piling and print mottle.

  • 4. Andersson, Kerstin I.
    et al.
    Pranovich, Andrey V.
    Norgren, Magnus
    Eriksson, Marie
    Holmbom, Bjarne
    Effects of biological treatment on the chemical structure of dissolved lignin-related substances in effluent from thermomechanical pulping2008Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 2, s. 164-171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effluent from a TMP-based pulp and paper mill was collected at the inlet and outlet of the mill's biological treatment plant and fractionated by sorption on XAD-8 resin and MTBE precipitation. Fractionation indicated that the refractory dissolved organic material in biologically treated effluent was mainly composed of lignin-related substances. Characterisation of the lignin-related substances by chromatographic and spectrometric methods confirmed the similarities of the isolated material and milled wood lignin. Fractionation and characterisation of alkali-extracted material from solids (biosludge) in biologically treated effluent found evidence of lignin-related material. Results indicated that biological treatment had altered the chemical structure and molar-mass distribution of dissolved lignin-related substances.

  • 5.
    Ankerfors, Caroline
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lingström, Rikard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ödberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    A comparison of polyelectrolyte complexes and multilayers: Their adsorption behaviour and use for enhancing tensile strength of paper2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 1, s. 77-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper compares the adsorption behaviour and paper-strength-enhancing properties of polyelectrolyte complexes (PECs) and polyelectrolyte multilayers (PEMs) of polyallylamine hydrochloride and polyacrylic acid. Model adsorption experiments using SPAR (stagnation point adsorption reflectometry) and QCM-D (quartz crystal microbalance with dissipation) showed that the amount of complexes adsorbed was lower than the amount adsorbed when forming a multilayer using the same polymer system. From these experiments, in combination with AFM and ESEM imaging, it was concluded that the PEC adsorption stopped before full surface coverage was reached. Tensile testing of handsheets treated with PECs and PEM showed a significant increase in both tensile index and strain-at-break using both systems. The largest strength improvement was achieved with the fibres treated with the largest number of PEMs, but the largest effect per adsorbed amount of polymer was achieved by PEC treatment.

  • 6.
    Ankerfors, Mikael
    et al.
    Innventia AB, Sweden.
    Llindström, Tom
    Innventia AB, Sweden.
    Söderberg, Daniel
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Innventia AB, Sweden.
    The use of microfibrillated cellulose in fine paper manufacturing: Results from a pilot scale papermaking trial2014Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 29, nr 3, s. 476-483Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work the strength enhancing capabilities of microfibrillated cellulose (MFC) in highly filled papers was studied. Both the MFC production and the paper making were done in pilot scale under realistic industrial conditions. The results clearly show that MFC (2.5 - 5.0wt-%) could improve the mechanical properties of highly filled papers (20 - 35 wt-% filler contents). All studied dry mechanical properties were improved and the improvements were most pronounced for Z-strength and fracture toughness. By combining the MFC with a C-starch dosage further improvements in mechanical properties could be achieved. The improvements in mechanical properties enabled increased filler content with retained properties. The filler increase could be achieved at the same time as the sheet formation and the dry content after pressing were improved.

  • 7. Antonsson, S.
    et al.
    Lindström, Mikael
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Hogskolan, K. T.
    Ragnar, M.
    A comparative study of the impact of the cooking process on oxygen delignification2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 4, s. 388-394Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of oxygen delignification on chemical pulps of a given kappa number manufactured in different ways (using kraft, prehydrolysis kraft and magnesium sulphite cooking) has been investigated. The prehistory of the pulps proves to be a very important factor in determining the response to oxygen delignification, i.e. the degree of delignification. It is shown that this is not due to different amounts of hexenuronic acid (HexA) in the different pulps, although this is an important factor behind the high residual kappa number after oxygen delignification of birch kraft pulp. Oxygen delignification of sulphite pulps proves to be efficient even at kappa numbers significantly lower than 10. These pulps show the greatest yield loss over the oxygen delignification. It is likely that Lignin Carbohydrate Complexes (LCC) complexes play a very important role in limiting the speed of reaction of oxygen delignification. Due to the very different prehistories of the pulps investigated, it is probable that the LCC:s are native and not formed during cooking.

  • 8.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    The influence of lignin and xylan on some kraftliner pulp properties2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 4, s. 403-408Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Karlström, Katarina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Applying a novel cooking technique to produce high kappa number pulps: the effects on physical properties2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 4, s. 415-420Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mäkelä, Petri
    Innventia AB.
    Fellers, Christer
    Innventia AB.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Comparison of the physical properties between hardwood and softwood pulps2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 4, s. 409-414Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Fenton's reaction: a simple and versatile method to structurally modify commercial lignosulphonates2011Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, nr 1, s. 90-98Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 12. Athley, Karin
    et al.
    Granlöf, Lars
    Söderberg, Daniel
    Innventia AB, Box 5604,, Stockholm, Sweden.
    Ankerfors, Mikael
    Ström, Göran
    Mechanical retention – Influence of filler floc size and grammage of the fibre web2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 2Artikkel i tidsskrift (Fagfellevurdert)
  • 13. Axelsson, P.
    et al.
    Ek, Monica
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Teder, A.
    Influence of alkali profiling in birch kraft pulping on QPQP bleachability2004Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 1, s. 37-43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of different aspects of alkali profiling in the kraft cook on QPQP bleachability of oxygen-delignified birch pulp was investigated. The use of a levelled-out alkali profile was compared to a conventional, and different modifications to the levelled-out alkali profile, like alkali charge, degree of delignification and amount of dissolved organic substance and ionic strength in the cooking liquor were studied. The alkali profile itself was found to have a significant effect where a levelled-out alkali profile showed a superior bleachability compared to a conventional one. The bleachability improved with an increased alkali charge towards the end of the cook, a high kappa number after cooking or by a cooking liquor exchange in order to decrease the amount of dissolved organic substance and the ionic strength towards the end of the cook. When a levelled-out alkali profile was used, the bleachability correlated well with the light-absorption of the lignin in the unbleached pulp, where a pulp with a brighter lignin consumed less peroxide in the QPQP sequence, for the pulp to reach 89% brightness.

  • 14. Axelsson, P.
    et al.
    Ek, Monica
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Teder, A.
    The influence of alkali charge and temperature in the kraft cook on the QPQP bleachability and the kappa number composition of birch pulp2002Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, nr 3, s. 206-212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main objective of this investigation was to study how the alkali charge and the temperature in the kraft cook influence the QPQP bleachability of oxygen-delignified birch pulp. The bleachability was evaluated as the normalised consumption of bleaching chemicals required to reach a certain light absorption coefficient of the pulp. All the pulps had a kappa number of about 17 after the cook and a kappa number of about 10 after oxygen delignification. The alkali charge significantly affected the bleachability and the best bleachability was obtained for an intermediate level alkali charge ([HO-](initial)=1,35 mol/L, corresponding to an effective alkali charge of 21.6% on wood). An increase in cooking temperature gave only a slight increase in bleachability. The contributions to the kappa number of lignin, hexenuronic acids (HexA) and other non-lignin structures were also investigated. Lignin contributed to about 60% of the kappa number in pulps after the cook, to about 40% in pulps after the oxygen delignification, and to about 30% after QPQP bleaching. Hexenuronic acids contributed between 3.7 to 4.7 kappa number units in all pulps, which makes them the largest contributors to the kappa number in oxygen-delignified and QPQP bleached pulps. Other non-lignin structures, were contributing about 3 kappa number units in pulps after the cook, but decreased to less than I kappa number unit after QPQP bleaching. No great differences in the composition of the kappa number could be seen between pulps produced under different pulping conditions, except that there was a somewhat lower hexenuronic acid content in the pulps produced with the highest alkali charge or at the highest cooking temperature.

  • 15.
    Axelsson, Patrik
    et al.
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Influence of the conditions during birch kraft cooking on unbleached brightness, and on ECF- and TCF-bleachability2004Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 3, s. 309-317Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influences on ECF and TCF bleachability of the hydroxide ion, hydrogen sulphide ion and sodium ion concentrations as well as of the amount of dissolved wood components (DWC) in a birch kraft cook were investigated. The pulping was carried out using a so-called constant composition cooking technique, where a high liquor-to-wood ratio enables an almost constant concentration of the cooking chemicals during the entire cook. This cooking method also renders possible to vary each cooking variable separately. The pulps were oxygen-delignified and bleached in a D(EOP)DD and a Q(OP)Q(PO) sequence. The presence of DWC caused a significant rate increasing effect on the delignification. An increase in hydroxide ion concentration, an increase in hydrogen sulphide ion concentration or a decrease in sodium ion concentration improved both the ECF and the TCF bleachability, but the DWC had no significant effect on the bleachability. Further a correlation was found between the bleachability and the brightness of the oxygen-delignified pulp.

  • 16. Backa, Stefan
    et al.
    Ragnar, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pulp bleaching with peracetic acid generated from acetylated polymeric carbohydrates and hydrogen peroxide - Proof of principle2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 4, s. 409-414Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The generation of peracetic acid in the pulp mill may open up new opportunities to use this bleaching chemical. The generation of peracetic acid from acetylated carbohydrates and hydrogen peroxide followed by bleaching of pulp in a T stage was therefore studied with special emphasis on the COD content in the bleaching effluent from this stage. This preliminary work demonstrates that peracetic acid can be generated from acetylated polymeric carbohydrates and hydrogen peroxide, and that this peracetic acid will bleach pulp fibres as effectively as distilled peracetic acid. It is also shown that most of the deacetylated polymeric carbohydrate (in this case cationic starch) adsorbs to the fibre and does not affect the COD content of the filtrate after the T stage. The peracetic acid has been generated with and without pulp present. The peracetic acid yield from polymeric activators and hydrogen peroxide was lower than that from acetylated glucose. The peracetic acid yield can be further be optimised with respect to the acetylated polymer structure, process parameters and added peracetic acid stabilisers. No effect on the tensile strength was observed when cationic starch was used as an acetyl carrier in a TCF sequence with a final (PO) stage. Most of the cationic starch was probably removed in the washing after the (PO) stage pulp. To avoid this, the (PO) stage should be exchanged for a neutral or acidic bleaching stage or the cationic starch should be exchanged to a carbohydrate that better adsorbs to the fibre under alkaline conditions.

  • 17.
    Barbier, Christophe
    et al.
    KTH, Tidigare Institutioner (före 2005), Hållfasthetslära.
    Larsson, Per-Lennart
    KTH, Tidigare Institutioner (före 2005), Hållfasthetslära.
    Östlund, Sören
    KTH, Tidigare Institutioner (före 2005), Hållfasthetslära.
    Experimental investigation of damage at folding of coated papers2002Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 17, nr 1, s. 34-38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experimental investigation of damage occuring at folding of coated paper has been performed. For this purpose an experimental device was constructed in such a way that close resemblance with an industrial situation was achieved. During the experiments the influence on the damage levels in the coating from such features as delamination, humidity and paper thickness have been studied using an optical microscope. The behaviour of two different paper materials has been investigated. A stress (or strain) based fracture criterion is relevant for the present problem but biaxiality of stresses as well as in-plane anisotropy must be taken into account. It was observed that cracking of the coating would not lead to subsequent cracking of the paper substrate and that delamination occurred during folding, in the base stock and not at the paper/coating interface, but its quantitative influence as regards cracking could not be determined. The influence from sheet grammage was investigated and it was found that the only case when (visible) cracks did not appear was at low values. High humidity did not affect the cracking.

  • 18.
    Bergström, Roger
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Åkesson, Krister
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Norman, Bo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    A twin-wire model gap former: design and evaluation methods2006Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, nr 1, s. 54-58Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A one-sided model twin wire gap former, the KTH-former has been developed. The former consists of headbox with transparent gables, forming unit, including a forming roll with a transparent surface and outer forming wire and a reservoir system for water/fibre suspension handling. To allow the study of blade forming, a blade can be introduced against the outer wire to generate a pressure pulse.

    Two measurement techniques have been utilized to study the flow mechanisms of fibre suspension flow in the forming zone;

    A pressure sensor has been used to study the dewatering pressure along the forming zone.

    A high speed video system was used to visually study the suspension flow.

    The study was made with pulp fibres. Fibre floes were introduced in the center of the headbox at the beginning of the linear nozzle contraction, by an introduction tube with an inner diameter of 10 mm. The acceleration in the nozzle contraction was used to separate the fibre floes in the Suspension making them move individually, thus making the visualisations easier. To avoid the problem of floc break-down at nozzle exit when using a conventional linear nozzle with parrot's beak outlet, two Curved contraction blocs were inserted, giving a more constant acceleration profile, letting the floes keep their integrity in the emerging jet.

    The high speed video system had two main arrangements, for the Study of floc behaviour in the forming zone. A mirror installed on the machine structure visualised a certain area of the forming zone. Alternatively, a mirror fastened to the back plate of the forming roll followed a specific area of the wire (and roll), making it possible to follow the floes through the entire forming zone. It is then possible to detect any relative motion between floes and wire.

  • 19.
    Björkman, Ulf
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Break-up of suspended fibre networks2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 1, s. 32-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Suspended fibre networks form when flowing fibre suspensions come to rest. When stresses on such a network increases, the network is broken down and the fibre suspension eventually returns to a flowing condition. Here a series of experiments are described showing that the initiation of this break-down process leads to network-free voids opening up in the direction parallel to the largest compression.

  • 20.
    Björkman, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Pappersteknologi.
    Floc dynamics in flowing fibre suspensions2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 2, s. 247-252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fibre suspensions are ubiquitous in nature and technology. They occur in flowing form and as extended networks. Flow of fibre suspensions takes place in smaller network portions, fibre floes. Fibre networks normally form when fibre flows stop and vice versa. Traditionally, fibre suspensions are treated as systems of fibres. Here they will be treated as crowded systems of compressible floes. With a large Couette device it is shown that these floes split and fuse, shrink and swell and behave much like a particulate system composed of compressible floes suspended in a liquid, which can move in and out of the floes. The investigated average shear rate range is from zero to about 600 s(-1).

  • 21.
    Björkman, Ulf
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Stress generation and transmission in suspended fibre networks2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 1, s. 38-43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Suspended fibre networks are viewed as particulate systems of closely packed non-adherent compressible flocs suspended in an incompressible penetrating matrix. Experiments show that stress chains form upon compression because the flocs stand in the way of each other. If tensile stresses are applied, the. flocs separate without significant resistance. Network voids open up between and parallel to the stress chains. The reason is that the fibres create compressible flocs with a Poisson ratio less than 0.5.

  • 22.
    Borodulina, Svetlana
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Extracting fiber and network connectivity data using microtomography images of paper2016Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 3, s. 469-478, artikkel-id 07315Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We apply image analysis methods based on micro-computed tomography (μCT) to extract the parameters that characterize the structure and bonding parameters in the fiber network of paper. The scaling and variational properties of μCT images are examined by analyzing paper structural properties of two 1 × 1 mm2 test pieces, which have been cut out from a low-grammage handsheet. We demonstrate the applicability of the methods for extracting the free fiber length, fiber cross-sectional data, the distances between the fibers, and the number of fiber-to-fiber bonds, which are the key properties required for the adequate representation of the network in numerical models. We compare the extracted connectivity data with the early reported analytical estimations and conclude that the number of contacts in three-dimensional networks is controlled by the fiber aspect ratio. In addition, we compare the cross-sectional data with those measured by the fiber morphology characterization tools and estimate the fiber shrinkage from completely wet to dry state to be nearly 20%.

    Fulltekst (pdf)
    fulltext
  • 23.
    Borodulina, Svetlana
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.). KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Kulachenko, Artem
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.). KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Galland, Sylvain
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Nygårds, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Hållfasthetslära (Avd.). KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Stress-strain curve of paper revisited2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 2, s. 318-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated a relation between micromechanical processes and the stress-strain curve of a dry fiber network during tensile loading. By using a detailed particle-level simulation tool we investigate, among other things, the impact of "non-traditional" bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds. This is probably the first three-dimensional model which is capable of simulating the fracture process of paper accounting for nonlinearities at the fiber level and bond failures. The failure behavior of the network considered in the study could be changed significantly by relatively small changes in bond strength, as compared to the scatter in bonding data found in the literature. We have identified that compliance of the bonding regions has a significant impact on network strength. By comparing networks with weak and strong bonds, we concluded that large local strains are the precursors of bond failures and not the other way around.

  • 24.
    Brännvall, Elisabet
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Eriksson, Malin
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Fibre surface modifications of market pulp by consecutive treatments with cationic and anionic starch2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 2, s. 244-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bleached softwood kraft pulps were coated with one to three layers of starch, which lead to tensile strength improvement. The strength increase was larger when a never-dried pulp was treated compared to treatment of a once-dried pulp, although equal amounts of starch were adsorbed in both cases. When the never-dried, starch-treated pulp was dried and subsequently reslushed, its tensile strength was higher than that of the never-dried reference pulp. It also required less PFI beating to reach a certain tensile index. Starch-treatment can thereby be a way of improving the tensile strength and beatability of market pulp.

  • 25.
    Brännvall, Elisabet
    et al.
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Gustafsson, R.
    Teder, A.
    Properties of hyperalkaline polysulphide pulps2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 4, s. 436-440Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The term hyperalkaline polysulphide pulping is used to denote a process utilising a polysulphide pretreatment step at high alkalinity. The stabilising effect of polysulphide on carbohydrates is enhanced by higher alkali concentrations. The high alkali concentration in the stabilisation stage also increases the delignification rate in the subsequent cooking stage. In order to keep the alkali at a high level, hyperalkaline polysulphide pulping employs two pretreatment stages. In the first stage, the alkali charge is aimed to neutralise the acids formed of the wood components. The succeeding stage is the actual hyperalkaline polysulphide stage. It has a noticeably higher alkali concentration, thus promoting an efficient carbohydrate stabilisation by the polysulphide. The hyperalkaline polysulphide pretreatment makes it possible to obtain a pulp with high viscosity and yields good bleachability and good strength properties. The pulps however, need more beating energy to reach a high tensile strength than kraft and normal polysulphide pulps.

  • 26.
    Brännvall, Elisabet
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Jansson, Zheng
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Characterisation of dissolved spruce xylan in kraft cooking2011Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, nr 4, s. 380-385Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 27.
    Brännvall, Elisabet
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    A study on the difference industrially and in tensile strength between laboratory-cooked pulp2006Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, nr 2, s. 222-226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The tensile strength levels of industrially produced pulp and corresponding laboratory-cooked pulps were investigated. The industrial pulp had a lower tensile strength, which could not be explained by fibre form or fibre strength. It was concluded that bonding strength was the limiting factor for the tensile strength of the industrial pulp. The industrial pulp, despite of its higher hemicellulose content, had a lower surface charge. The xylan precipitated onto the fibres during the industrial cook was probably more degraded and consequently with lower degree of polymerisation and fewer charged groups.

  • 28. Bäckström, M
    et al.
    Brännvall, Elisabet
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Effect of primary fines on cooking and TCF-bleaching1999Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 14, nr 3, s. 209-213Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When pulp is separated into fibre fractions on the basis of size, the smallest fraction obtained is called fines. Primary fines are found in cooked pulp not subjected to beating and secondary fines are created in the cause of beating. Fines have higher lignin and metal ion contents than the fibre fractions of the pulp. In this study, the effect of the primary fines on cooking and bleaching has been investigated. The results showed that removal of the primary fines during cooking had no positive effect on the delignification. The pulp viscosity at a certain kappa number and the H-factor to reach this kappa number were the same, regardless of whether or not the primary fines were present. However, the primary fines had a profound effect on bleaching when a QP sequence was used. An increase of approximately 2 ISO-brightness units was obtained by removing the primary fines prior to bleaching. Pulps with and without primary fines showed no significant difference in metal ion content or light scattering coefficient. The light absorption coefficient was, however, higher in the pulp with fines. The improved bleachability of the pulps without fines was therefore probably caused by differences in lignin content and in the lignin structure rather than by differences in metal ion content.

  • 29.
    Bäckström, Marie
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. 640204-6962.
    Hammar, Lars-Åke
    Htun, Myat
    Beatability and runnability studies of ion-exchanged unbleached kraft pulps on a pilot scale2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 1, s. 94-100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has earlier been shown that the counter-ion to the charged groups in the fibre has a significant effect on the beatability of fibres, but large-scale investigations of this effect are scarce in the literature. The objectives of the present study were therefore to develop a technique to ion-exchange large quantities of industrial pulp into the Na(+)-form using complexing agents and to study the effect of industrial-scale refining on pulp fibres in the Na(+)-form and how the fibres respond to industrial-like papermaking.The results show that ion-exchange can indeed be conducted on a pilot-scale using complexing agents such as DTPA. The study further indicates that an energy reduction of 50% at a given WRV or tensile index may be achieved if the fibres are converted to Na(+)-form prior to pilot-scale refining. By applying these techniques in full-scale production, it should thus be possible to save significant amount of energy, especially in the case of papers made from unbleached pulp that usually demands a higher degree of beating to achieve sufficient strength.

  • 30.
    Bäckström, Marie
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH). STFI, Swedish Pulp & Paper Res Inst, Box 5604, S-11486 Stockholm, Swede.
    Hammar, Lars-Åke
    Htun, Myat
    Effect of the counterion on the beatability of unbleached kraft pulps2000Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 15, nr 3, s. 189-193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this investigation was to demonstrate the effect of the counterion on the energy consumption during a beating process and on the resulting strength properties of handsheets. The effect of the counterion on beating was separated from the effect of sheet moulding by converting all the fibre samples into the Ca2+-form prior to sheetmaking. An unbleached kraft pulp was used because of its relatively high carboxylic acid content.The beatability of the pulp fibres was affected by the type of counterion to the dissociable groups in the fibres. Converting the pulp into the Na+-form before beating improves the beatability, defined as the increase in WRV per unit energy input, compared to the two other investigated ionic forms, the H+ form and the Ca2+-form. The energy required to reach a given tensile index was substantially lower for pulps beaten in Na -form. The better beatability of the pulps in the Na+-form showed that the energy efficiency of beating is improved if the fibres are highly swollen initially. Beating in the Na -form can reduce the energy demand by 50%.Commercially, pulp is normally beaten in the Ca2+-form. In this ionic form, the negatively charged ions are shielded and the swelling is less favoured. A better knowledge of the charged groups of the pulp fibres and their physical and chemical behaviour may mean that less energy or fewer beating steps may be required in future papermaking.

  • 31. Bäckström, Marie
    et al.
    Melander, Erik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Brännvall, Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Study of the influence of charges on refinability of bleached softwood kraft pulp2013Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, nr 4, s. 588-595Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To investigate how the number of charged groups affects the refinability of pulp, different levels of fibre charge were introduced to fully bleached softwood kraft pulp by bulk carboxymethylation. The chemical compositions of the fibres thus remained similar and the effect of the charge could be evaluated. The pulps were refined in a PFI-mill. The introduction of additional charges clearly resulted in a higher refinability in terms of a higher WRV for a given energy input. However, the increase in swellability was not accompanied by a corresponding increase in tensile index. The highly charged pulps suffered severe damage to the fibre wall during refining, showing that the combination of high charge levels and mechanical forces cause destruction of the fibre wall, which inhibits paper strength development.

  • 32. Bäckström, Marie
    et al.
    Tubek-Lindblom, Anna
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Studies of the influence of deflocculants and flocculants on the refining efficiency on a pilot scale2009Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 3, s. 319-326Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of the present investigation was to study the influence of flocculants and deflocculants on refining efficiency. The refining was performed with the aid of a conical refiner at EuroFEX, and the refining response was evaluated as the change in fibre properties and in the mechanical properties of handsheets. Using the same furnish, an unbleached never-dried softwood pulp, the effect of fibre dimensions on floe strength was excluded as much as possible. The degree of flocculation was changed by addition of APAM, CPAM, guar gum and CMC. The floe strength was characterized using a parallel plate rheometer. The added chemicals, except for APAM, affected the relation between power input and gap clearance. To reach a certain power the fibres treated with guar gum, CMC or CPAM required a narrower gap clearance than the reference pulp or when APAM was added to the fibres. Refining at a narrower gap clearance increased the refining efficiency in terms of WRV and paper property development, as long as fibre length reduction could be avoided.

  • 33.
    Carlsson, Allan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Söderberg, Daniel
    Innventia AB, Box 5604, SE–114 86 Stockholm.
    Lundell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Fibre orientation measurements near a headbox wall2010Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, nr 2, s. 204-212Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental results on the fibre orientation in a laboratory scale headbox are reported. Images containing fibres in approximately 1 mm thick slices parallel to the wall were captured at different wall distances. A steerable filter was used to determine the orientation of bleached and unbeaten birch fibres, suspended in water, at different distances from one of the inclined walls of the headbox contraction. Due to optical limitations only dilute suspensions were studied. It is shown that the fibre orientation distribution varies with the distance from the wall. Sufficiently far upstream in the headbox a more anisotropic distribution is found closer to the wall.

  • 34.
    Chen, Chao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Antibacterial evaluation of CNF/PVAm multilayer modified cellulose fiber and cellulose model surface2018Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 3, s. 385-396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Earlier studies have shown that 3-layer-modified cellulose fibers with poly(acrylic acid) (PAA) as the middle layer between two cationic polyelectrolyte polyvinylamine (PVAm) layers have strong antibacterial efficacy in terms of both bacteria adsorption and bacterial growth inhibition. In the present work, the fossil-based PAA middle layer was replaced by sustainable wood-based cellulose nano-fibrils (CNF), i. e., the fibers were modified by a 3-layer PVAm/CNF/PVAm system. Interestingly, the antibacterial efficacy of this system was greater than that of the previous PVAm/PAA/PVAm system. A higher salt concentration and lower assembly pH in the multilayer build-up resulted in better bacterial reduction. As the surface of a cellulose fiber is heterogeneous, making it difficult to characterize and visualize at high resolution, more homogeneous cellulose model surfaces were prepared by spin coating the dissolved cellulose fiber onto a silica surface to model the fiber surface. With increasing ionic strength, more aggregated and heterogeneous structures can be observed on the PVAm/CNF/PVAm modified model surfaces. The adsorbed bacteria distributed on the structured surfaces were clearly seen under fluorescence microscopy. Adsorbed amounts of bacteria on either aggregate or flat regions were quantified by scanning electron microscopy (SEM). More adsorbed bacteria were clearly seen on aggregates than on the flat regions at the surfaces. Degrees of bacteria deformation and cell damage were also seen under SEM. The surface roughness of the modified model surfaces was examined by atomic force microscopy (AFM), and a positive correlation was found between the surface roughness and the bacterial adhesion. Thus, an additional factor that controls adhesion, in addition to the surface charge, which is probably the most dominant factor affecting the bacteria adhesion, is the surface structures, such as roughness. 

  • 35. Christiernin, M.
    et al.
    Henriksson, Gunnar
    KTH, Tidigare Institutioner (före 2005), Pappers- och massateknik.
    Lindström, Mikael
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Brumer, Harry
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Teeri, Tuula T.
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Lindström, T.
    Laine, J.
    The effects of xyloglucan on the properties of paper made from bleached kraft pulp2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 2, s. 182-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Xyloglucan was adsorbed onto bleached soft-wood kraft pulp followed by preparation and analysis of handsheets with respect to sheet formation as well as sheet mechanical and optical properties. Adsorption of xyloglucan was found to be slow. After more than 20 hrs adsorption, equilibrium had not been reached. The amount of xyloglucan adsorbed increased with beating, but neither the rate of adsorption nor the quantity adsorbed was significantly affected by temperature. Xyloglucan was found to be practically irreversibly adsorbed onto the fibres and the effects of xyloglucan on paper sheet properties were investigated after thorough washing of the pulp. The adsorption characteristics of xyloglucan confirm observations by other authors on other cellulose substrates. Tensile index values for handsheets formed with the xyloglucan-containing pulps were higher than those measured for control pulps with a comparable beating degree. The light scattering coefficient was, however, not affected by xyloglucan adsorption. Hence, the increase in tensile strength is attributed to an increased relative bond strength between the fibres. Tensile strength versus tear strength relationship was similar for pulps with and without xyloglucan, but water retention value and dewatering resistance were lower for the xyloglucan treated pulps than for the reference pulps at the same tensile strength. In addition, formation was improved for pulps with adsorbed xyloglucan. The conclusion is that xyloglucan is a promising wet end additive that decreases the necessity for beating of the pulp and improves the formation of paper.

  • 36.
    Danielsson, Sverker
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Influence of birch xylan adsorption during kraft cooking on softwood pulp strength2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 4, s. 436-441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dissolution, degradation and redeposition of xylan in the kraft cooking of birch pulp were investigated. The molecular weight of the dissolved xylan was determined through gel permeation chromatography, and the loss in molecular weight could be correlated with the amount of degraded xylan in the initial stages of the kraft cook. This indicates that peeling is the only significant xylan degradation reaction taking place early in the cook. Two different birch black liquors containing xylan with molecular weights of 12.20 g/mol and 5.95 g/mol, respectively, were added to softwood kraft cooks in order to determine the effect of birch xylan on pulp strength properties. The results show an increase in both tensile strength and tensile stiffness. The magnitude of the strength increase was greatly affected by the molecular weight of the xylan added. Adding high-molecular-weight xylan increased the tensile strength by more than 10%, as measured at a beating degree of 1000 PFI revolutions. Tensile stiffness was also increased by xylan addition, though more so when the xylan was of high rather than low molecular weight.

  • 37.
    De Magistris, Federica
    et al.
    Karstad University.
    Salmén, Lennart
    STFI-Packforsk AB.
    Finite Element Modelling of wood cell deformation transverse to the fibre axis2008Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 2, s. 240-246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modelling of wet wood under compression and combined shear and compression load was performed to simulate the mechanical pulping of wood chips in refiners. Experiments have shown that the wet fibre network exhibit two different deformation modes; an S-shape mode associated with compression and a brick-shape mode associated with combined shear and compression. To study the factors governing the mechanical behaviour of the fibre network a material model with the characteristics originating from the properties of the wood polymers was developed and was used in a three-dimensional finite element analysis. The effects of material properties were investigated by comparing models with anisotropic one-layer cell walls and orthotropic multi-layer cell walls. The deformation achieved both under compression and under combined shear and compression was found to be similar independent of the material constants used or the number of layers of the cells walls. This implies that the most important factor governing the deformation pattern of the fibre network is the cell structure itself.

  • 38.
    De Magistris, Federica
    et al.
    STFI-Packforsk AB.
    Salmén, Lennart
    STFI-Packforsk AB.
    Mechanical behaviour of wet wood in sequences of compression and combined compression and shear2006Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, nr 2, s. 231-236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During the refining of mechanical pulp, a process occurring at high speed at temperatures of 140-160°C, the flexibility and bonding ability of the wood fibres increase. To understand the mechanical behaviour of the fibres in this operation, the deformation at low speed of wet wood specimens at 50°C and 90°C were studied under different combinations of shear and compression loading using a modification of the Arcan device. The deformation in earlywood was studied using an image analysis procedure together with measurements of the work done under different loading conditions. The deformation under combined shear and compression load was different from that in pure compression. In the first cycle under compression, the fibre cell walls were bent in a characteristic "S" shape, whereas under the combined load the cells deformed according to a "brick" shape. After a first cycle under combined load, the cells deformed according to the "brick" shape even when subjected to a second load under pure compression. The first deformation cycle required the largest amount of work. Since less energy was needed for the first cycle under a combined load than under a compression load, the application of a combined load as a first cycle may be a way to permanently deform fibres using less work.

  • 39.
    de Souza, Gustavo B.
    et al.
    Univ Fed Vicosa, UFV, Dept Forestry Engn, BR-36570900 Vicosa, MG, Brazil..
    Colodette, Jorge Luiz
    Univ Fed Vicosa, UFV, Dept Forestry Engn, BR-36570900 Vicosa, MG, Brazil..
    Borges Gomes, Fernando Jose
    Univ Fed Vicosa, UFV, Dept Forestry Engn, BR-36570900 Vicosa, MG, Brazil..
    de Carvalho, Danila Morais
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Enhancement of eucalypt pulp yield through extended impregnation cooking2018Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, nr 2, s. 175-185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The improvement caused by eucalypt chip impregnation on kraft pulping performance was assessed for terminating the cook at kappa in the range of 15-27 and at controlled residual effective alkali (REA) of 6-8 g/L NaOH. Extended impregnation cooking of eucalypt chips (EIC) increased about 10/0 lignin- and HexA-free screen yield gains in relation to conventional cooking (CC), regardless of kappa number in the range of 15-27. The EIC technology allows for cooking eucalypt wood to kappa number up to 27, without rejects production, but without significant improvement in lignin- and HexA-free screen yield and with larger chlorine dioxide (ClO2) consume during bleaching. The optimum kappa number for both CC and EIC cooking was about 19 with similar refinability and strength properties for both technologies, CC and EIC. It was concluded that extended impregnation cooking is an attractive technique for enhancing bleached eucalypt Kraft pulp yield.

  • 40.
    Duker, Elisabeth
    et al.
    STFI-Packforsk AB.
    Ankerfors, Mikael
    STFI-Packforsk AB.
    Lindström, Tom
    STFI-Packforsk AB.
    Glad Nordmark, Gunborg
    STFI-Packforsk AB.
    The use of CMC as a dry strength agent - the interplay between CMC attachment and drying.2008Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 1, s. 65-71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper deals with the ability to use high molecular weight CMC as a dry strength agent in paper and how the drying of the pulp, either before or after the CMC attachment, affects the mechanical properties of the paper. The effect of the counter-ion form used during drying and reslushing was also investigated. In the case of the calcium and hydrogen counter-ion forms, drying after CMC attachment had no impact on the attached amount. The sodium form did, however, result in some detachment of CMC. When the pulp was dried prior to CMC treatment, the counter-ion form had no effect on the attached amount. It was also shown that drying of a CMC-treated pulp reduced the positive effect of CMC on the mechanical properties. Nevertheless, the mechanical properties were still better than those of paper made from the never-dried reference pulp. The relative effect of CMC on the mechanical properties was independent of the drying strategy used and the counter-ion form did not affect the mechanical properties. However, surface carboxymethylation prior to drying resulted in sheets with better final mechanical properties than sheets made from pulp that had first been dried and then surface carboxymethylated.

  • 41.
    Duker, Elisabeth
    et al.
    STFI-Packforsk AB.
    Brännvall, Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lindström, Tom
    STFI-Packforsk AB.
    The effects of CMC attachment onto industrial and laboratory-cooked pulps2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 3, s. 356-363Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of surface carboxymethylation of industrial and laboratory-cooked pulp was studied regarding attached amount, fibre properties and paper sheet strength. The strength development was compared with the effects of PFI beating. Attachment of CMC was shown to be equally effective with industrial pulp as with laboratory-produced pulp. The attachment level was 100% for both pulp types and no difference in paper strength enhancement could be detected. CMC attachment had a small impact on sheet density, especially compared to PFI beating. Moreover, surface carboxymethylation was shown to increase the shape factor, reduce the number of kinks per fibre and to increase the rewetted zero-span index. This straightening effect of CMC was interpreted in terms of an increase in carboxyl group repulsion on the fibre surface and is probably a factor contributing to the increase in paper strength. Differences in fibre curl between industrial and laboratory-cooked pulp decreased when CMC was attached to the fibre surface. This may explain why no differences in CMC efficiency could be detected.

  • 42.
    Duker, Elisabeth
    et al.
    STFI-Packforsk AB.
    Lindström, Tom
    STFI-Packforsk AB.
    On the mechanisms behind the ability of CMC to enhance paper strength.2008Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, nr 1, s. 57-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The attachment of CMC to pulp is known to have a strong impact on the tensile strength properties. The mechanisms behind the strength-enhancing ability of the CMC have been investigated by studying the effect of surface carboxymethylation on some basic fibre and sheet properties. Standard methods were used for the strength evaluation, and the relative bonded area was determined from both light-scattering measurements and BET-analysis. The effect of CMC on the shear bond strength was calculated using Page's equation. The attachment of CMC was shown to increase the shape factor and reduce the number of kinks per fibre, which is beneficial for the tensile strength. Surface carboxymethylation also increased the relative bonded area, but on a small-scale structural level detectable only using BET-analysis and not by the scattering coefficient. The sheet density was not affected by the treatment. CMC attachment also increased the shear bond strength. In order to use Page's equation for this evaluation, the relative bonded area had to be determined by BET-analysis. The positive effect of CMC on sheet formation also contributed to an increase in tensile strength.

  • 43.
    Durruty, Julie
    et al.
    Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden..
    Sewring, Tor
    Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden. ; Wallenberg Wood Science Centre, Royal Institute of Technology, Chalmers University of Technology, SE-100 44 Stockholm, Sweden .
    Schneider, Helen
    Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden..
    Schneider, Lynn
    Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden..
    Mattsson, Tuve
    Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden. ; Wallenberg Wood Science Centre, Royal Institute of Technology, Chalmers University of Technology, SE-100 44 Stockholm, Sweden.
    Theliander, Hans
    Forest Products and Chemical Engineering, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden. ; Wallenberg Wood Science Centre, Royal Institute of Technology, Chalmers University of Technology, SE-100 44 Stockholm, Sweden.
    Filtration properties of kraft lignin: The influence of xylan and precipitation conditions2017Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, nr 4, s. 508-526Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    LignoBoost lignin powder was dissolved together with xylan and re-precipitated. The influence of the (i) precipitation temperature, (ii) rate of acidification and (iii) final pH of the slurries on the resulting material and its filtration properties was investigated. In the case of slow acidification, larger agglomerates were obtained for slurries with higher precipitation temperatures as well as with higher ionic strengths. Fast acidification led to a more heterogeneous formation of particles, having a broader particle size distribution, compared to slow acidification. Chemical analysis of different layers of the filter cakes formed revealed that xylan was distributed evenly on the solid lignin, reinforcing the hypothesis that xylan is sorbed onto the lignin agglomerates when precipitated together with lignin. Furthermore, the resulting lignin-xylan mixtures were found to be more difficult to filter in the case of a higher final pH of the slurry (pH 4), close to the pKa values of the carboxylic acid groups of xylan, compared to lower pH values (pH 1-3). This is likely the result of an increase in electrostatic repulsive interactions between the particles/agglomerates at higher pH: a locally more porous solid structure is formed, leading to a larger solid/liquid surface area during filtration.

  • 44. Edstrom, Per
    et al.
    Neuman, Magnus
    Avramidis, Stefanos
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk analys, NA.
    Andersson, Mattias
    Geometry Related Inter-Instrument Differences in Spectrophotometric Measurements2010Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 25, nr 2, s. 221-232Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The L&W Elrepho d/0 and the Spectrolino 45/0 instruments are examined using paper samples with different properties. External factors that influence the measurements such as the sample background, the instrument calibration and the sample inhomogeneity are studied, and a methodology for their minimization is presented. Experimental measurements show that such external factors, if not minimized by proper routines, affect the inter-instrument differences far more (up to 4-5 Delta E-ab(star)) than the instrument geometry (the effect of which is small and of order 0.1 Delta E-ab(star)). The DORT2002 radiative transfer model is used to simulate differences caused by instrument geometry. The simulated and measured differences are found to agree in magnitude, and the differences are mapped against sample properties. It is observed that the 45/0 instrument detects higher reflectance from paper samples with negligible absorption and transmittance. When there is considerable absorption (dyed samples) or transmittance (thin samples), the d/0 instrument detects higher reflectance. The physical mechanism behind this behavior is studied and explained using DORT2002, and the instrument differences are shown to depend on the anisotropy of the reflected light. The model/measurement agreement is satisfactory as the characteristic behavior is captured in almost all cases studied. This new understanding is important for facilitating accurate data exchange between the paper and graphic arts industries, but also for interpretation of reflectance measurements in general.

  • 45.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Lennholm, Helena
    Iversen, Tommy
    A comment on the effect of carbonyl groups on the light-induced reversion of groundwood pulp1990Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 5, nr 4, s. 159-160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sodium borohydride redn. of stone groundwood pulp from spruce (Picea abies) had no dramatic effect on the light-induced brightness reversion.  This indicates that the direct scission of phenacyl aryl ether linkages is not an important step in the initial chromophore formation.

  • 46.
    Ekevåg, Per
    et al.
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Lindström, Tom
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Addition of carboxymethylcellulose to the kraft cook2004Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 2, s. 200-207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The physical attachment of carboxymethylcellulose (CMC) onto kraft pulps during cooking and the effects of subsequent bleaching in an OD(EOP)DD sequence were investigated. Two CMC grades with different molecular weights and different degrees of substitution (D.S.) were used, CMC Finnfix WRH and CMC Cekol DVG. The effect of the CMC was studied by measuring the increase in the total charge density as well as in the surface charge density. In this way, both the total amount of attached CMC and the amount of the CMC attached onto the surface of the fibres Could be determined. Hand-sheets were made to study the effects of CMC addition on the physical properties of the paper. Different amounts of CMC were added to find the optimum, which was determined to be 1% CMC on wood. The proportion of CMC attached at a level addition of 1% (on wood) was about 40%. It was, however, found that a large part of the CMC was degraded during the cook. Whereas high molecular weight CMC is attached onto the surface of fibres, the degraded CMC is attached to the interior of the cell wall, decreasing the efficiency of the CIVIC to enhance the joint strength between fibres. The tensile index increased significantly, approximately 10% after beating to 2000 PFI revolutions, when 1% CMC Finnfix WRH on wood was added. The CMC Cekol DVG grade showed the greatest increase in tensile index, approximately 12% at 2000 PFI revolutions. The results of the bleaching of a sample treated with CMC Finnfix WRH showed that a part of the effect of CMC remains after bleaching. Most of the reduction in the positive effect was due to a loss of CMC molecules from the fibre surface.

  • 47.
    Enarsson, Lars-Erik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kinetics of sequential adsorption of polyelectrolyte multilayers on pulp fibres and their effect on paper strength2007Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 2, s. 258-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conditions for sequential adsorption of polyelectrolyte multilayers (PEM) onto pulp fibres were investigated in terms of appropriate addition levels and adsorption times. The objective was a technical application for improved tensile strength of paper. Two common polyelectrolytes (PE) in papermaking, polyamideamine epichlorolrydrin (PAE) and carboxymethyl cellulose (CMC), were consecutively adsorbed onto long fibres from a bleached softwood kraft pulp, adding up to four PE layers on the fibre surfaces. Adsorption isotherms and adsorption kinetics were studied layer by layer, giving recommended addition levels and adsorption times for each layer. PAE adsorbed in larger amounts than CMC, 4 and 1 mg/g, respectively on fractionated pulp free of fines. For the kinetics, longer times were required to reach saturation adsorption for PAE compared to CMC, corresponding to three and two minutes, respectively. Tensile testing of handsheets based on both fractionated and beaten pulp showed that four PE layers increased the tensile index by about 50%, reaching levels of 34 (unbeaten) and 88 Nm/g (beaten), respectively. The effect of PEM on strain at break depended on the beating level as the fractionated pulp showed an improvement from 2.5 to 4.1% while beaten pulp showed a reduction from 6.1 to 4.5%.

  • 48.
    Eriksson, Malin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Pettersson, Gunilla
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Application of polymeric multilayers of starch onto wood fibres to enhance strength properties of paper2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 3, s. 270-276Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyelectrolyte multilayers of cationic and anionic starch have been used to enhance the strength properties of paper. All starches used in this investigation had a degree of substitution around 0.065. Optical reflectometry showed that a combination of cationic and anionic starch could form polyelectrolyte multilayers onto silicon oxide surfaces. The same combination of starches was then applied to unbeaten, bleached softwood kraft fibres to form three layers, i.e. a cationic/anionic/cationic starch combination. The results showed a significant increase in the paper strength properties in terms of tensile index, strain at break, and Scott Bond. The adsorbed amount of starch in the sheets, determined using an enzymatic method, was found to increase with each successive starch treatment. The increased paper strength was not only due to the increase in adsorbed amount of starch; rather, the chemical composition of the starch was also important. Cationic starch with high amylose content had a more positive effect on the paper strength properties. Furthermore, it was observed that anionic starch, despite being adsorbed in large amounts, did not contribute to the increase in tensile strength or strain at break to the same extent as did cationic starch. However, the out-of-plane properties, measured as Scott Bond properties, increased with the adsorbed amount, regardless of the chemical composition of the starch used in the outermost layer.

  • 49.
    Esteves, Claudia
    et al.
    388792 RISE Research Institutes of Sweden , Bioeconomy and Health, Pulp, Paper and Packaging , Drottning Kristinas väg 61 , Stockholm , Sweden.
    Brännvall, Elisabet
    388792 RISE Research Institutes of Sweden , Bioeconomy and Health, Pulp, Paper and Packaging , Drottning Kristinas väg 61 , Stockholm , Sweden.
    Östlund, Sören
    KTH, Skolan för teknikvetenskap (SCI), Teknisk mekanik, Farkostteknik och Solidmekanik, Hållfasthetslära.
    Sevastyanova, Olena
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    The effects of high alkali impregnation and oxygen delignification of softwood kraft pulps on the yield and mechanical properties2022Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 37, nr 2, s. 223-231Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated whether the yield improvement after high alkali impregnation (HAI) is maintained after oxygen delignification and whether the potential of oxygen delignification to increase the mechanical properties is affected by high alkali impregnation. The yield improvement achieved by high alkali impregnation (1 %) was preserved after oxygen delignification, particularly of glucomannan. The total fiber charge and swelling increased after oxygen delignification regardless of the type of impregnation in the cooking step. The tensile index improvement obtained by oxygen delignification was retained if this was preceded by high alkali impregnation. The stiffness index was higher and elongation slightly lower after HAI impregnation than after a standard (REF) impregnation. Fibers obtained through high alkali impregnation seem to be slightly less deformed and slightly wider than fibers obtained after a standard impregnation.

    Fulltekst (pdf)
    fulltext
  • 50.
    Esteves, Cláudia V. G.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. RISE Research Institutes of Sweden, Bioeconomy and Health, Pulp, Paper and Packaging , Drottning Kristinas väg 61 , Stockholm , Sweden.
    Sevastyanova, Olena
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Östlund, Sören
    KTH, Skolan för teknikvetenskap (SCI), Teknisk mekanik, Farkostteknik och Solidmekanik, Hållfasthetslära.
    Brännvall, Elisabet
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Ingenjörspedagogik. RISE Research Institutes of Sweden , Bioeconomy and Health, Pulp, Paper and Packaging , Drottning Kristinas väg 61 , Stockholm , Sweden.
    The impact of bleaching on the yield of softwood kraft pulps obtained by high alkali impregnation2022Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 0, nr 0Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High alkali impregnation (HAI) increases the total yield of softwood pulps following kraft cooking. This yield improvement is also maintained after oxygen delignification. This study evaluates how bleaching with either chlorine dioxide or hydrogen peroxide affects the final yield of samples obtained with standard and HAI. The chemical composition, viscosity, brightness, mechanical and morphological properties were studied. Compared to cooking after standard impregnation the yield improvement achieved by HAI was preserved in both types of bleaching sequences (2% units for chlorine dioxide and 4% units for hydrogen peroxide). The introduction of charged groups into the cellulose fibers was higher with hydrogen peroxide bleaching than with chlorine dioxide however, no significant impact was seen on the swelling or mechanical properties. The brightness was higher for the pulps bleached with chlorine dioxide compared with hydrogen peroxide. Hydrogen peroxide bleaching resulted in similar brightness development for both standard and HAI. Fibers bleached with chlorine dioxide had the highest curl index (16-17%) compared to the fibers bleached with hydrogen peroxide (15%). 

    Fulltekst (pdf)
    fulltext
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