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  • 1. Eriksson, Malin
    et al.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Application of polymeric multilayers of starch onto wood fibres to enhance strength properties of paper2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 3, p. 270-275Article in journal (Refereed)
    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.

  • 2.
    Henshaw Osong, Sinke
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    The use of cationic starch and microfibrillated cellulose to improve strength properties of CTMP-based paperboardManuscript (preprint) (Other academic)
  • 3.
    Höglund, Hans
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    A paper or paperboard product comprising at least one ply containing high yield pulp and its production method2018Patent (Other (popular science, discussion, etc.))
  • 4.
    Marais, Andrew
    et al.
    KTH Royal Institute of Technology, Fibre and Polymer Technology, Teknikringen 56, Stockholm.
    Enarsson, Lars-Erik
    SCA R and D Center AB, Box 716, Sundsvall.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Lindström, Tom
    Innventia AB, Drottning Kristinas väg 55, Stockholm .
    Wågberg, Lars
    KTH Royal Institute of Technology, Fibre and Polymer Technology, Teknikringen 56, Stockholm.
    Pilot-scale papermaking using Layer-by-Layer treated fibres; Comparison between the effects of beating and of sequential addition of polymeric additives2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 2, p. 308-314Article in journal (Refereed)
    Abstract [en]

    The Layer-by-Layer (LbL) deposition technique was used to treat fibres before papermaking on a pilot scale. Following a laboratory pre-study performed earlier to determine the adsorption isotherms and the kinetics of formation of multilayers of polyamideamine epichlorydrine (PAE) and carboxymethylated cellulose (CMC) on unbeaten, bleached softwood fibres, online LbL treatment of the furnish was carried out on the EuroFEX pilot paper machine. Papers from fibres coated with up to four layers of polyelectrolytes were produced. Two different LbL systems were investigated, with anionic CMC in combination with either PAE or cationic starch (CS). The results showed that the mechanical strength of the paper significantly increased when the fibres were LbL-treated online. A comparison with conventional beating of the fibres revealed that the LbL treatment was a potential substitute to beating treatment, as the density of the LbL-treated papers remained constant while the mechanical properties were significantly improved. At the same time, the press solids content was significantly higher (2%) when using LbL-treated fibres than with beaten fibres.

  • 5.
    Nordin, Tommy
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. MoRe Research Örnsköldsvik AB.
    Svedberg, Anna
    MoRe Research Örnsköldsvik AB.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Industrially Relevant In-situ Production Of High Yield Pulp Based Nanocellulose Materials Optimized To Improve Strength In Packaging And Printing Papers: A Comparison Between CMC And MFC As The Anionic Component In Layer-by-Layer Technology2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    A key issue in papermaking is to understand how to improve strength without losing other important quality measures, like paper bulk. This must of course also be done in a cost efficient way. The trials described in this paper show some different aspects related to the replacement of the expensive anionic component CMC (carboxymethylcellulose) often used in Layer-by-Layer technology together with cationic starch in order to improve strength properties as z-strength and tensile strength of typical chemi-thermomechanical pulp (CTMP) often used as dominating component in industrial scale paper board production. The replacement for CMC investigated here is a MFC (micro-fibrillated cellulose) as the anionic component and paper sheets has been produced on an experimental paper machine at MoRe Research AB. This MFC is a commercially available product and it has not been treated in ways of increasing charge density. The trials were performed at a small pilot scale experimental paper machine (XPM) at MoRe Research in Örnsköldsvik, Sweden. This XPM is equipped with a unique setup to perform Layer-by-Layer-tests under very well controlled conditions. The general conclusion is that it could, with further developments, be feasible to replace CMC with MFC to improve bonding in typical CTMP based paper sheets.

  • 6.
    Norgren, Sven
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    High strength papers from high yield pulps2014In: International Mechanical Pulping Conference, IMPC 2014, 2014Conference paper (Refereed)
    Abstract [en]

    The positive effects changing the present standard conditions regarding temperature and moisture content during pressing and drying in papermaking of high yield pulp furnishes, such as those from TMP and CTMP, has previously been reported in a series of studies at Mid Sweden University. In the current study, the effects of fibre surface modification by starch/CMC at press-drying conditions have been investigated. It is shown how the strength properties of sheets from HTCTMP, manufactured at very low electric energy consumption (approximately 600 kWh/ton), can be radically improved by several hundred percent at optimum papermaking conditions.

  • 7.
    Norgren, Sven
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Strong paper from spruce CTMP - Part II: Effect of pressing at nip press temperatures above the lignin softening temperature2018In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 1, p. 142-149Article in journal (Refereed)
    Abstract [en]

    The main objective of the current study was to demonstrate that it is possible to enhance strength properties of sheets from spruce HT-CTMP and CTMP furnishes up to the same level as is common on sheets from softwood kraft pulps by changing conditions in papermaking. To achieve that, sheets of spruce HT-CTMP and CTMP were consolidated at densities close to that of the reference bleach kraft pulp by pressing at press nip temperatures well above the tack and softening temperatures of lignin. On sheets from spruce CTMP (CSF 420 ml), where the fibers were surface treated with cationic starch, it was possible to reach tensile index at the same level as on sheets from the untreated reference kraft pulp. The compression strength (SCT) of CTMP and HT-CTMP sheets, which were achieved at the highest press nip temperature (200 °C) in the study, was equal to or higher than that of the reference kraft pulp sheets. The results show that there is a great yet unexploited potential in papermaking from spruce HT-CTMP and CTMP furnishes, which could be utilized in manufacturing of products where very high requirements upon strength is demanded. 

  • 8.
    Osong, Sinke H.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Còrdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Alimohammadzadeh, Rana
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Processing of nanocellulose and applications relating to CTMP-based paperboard and foams2016In: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, p. 87-93Conference paper (Refereed)
    Abstract [en]

    Although remarkable success has been made in the production of nanocellulose through several processing methods, it still remain a challenge to reduce the overall energy consumption, to use green chemistry and sustainable approach in order to make it feasible for industrial production of this novel nanomaterial. Herein, we have developed a new eco-friendly and sustainable approach to produce nanocellulose using organic acid combined with high-shear homogenisation, made hydrophobisation of nanocellulose and cross-linked the modified nanocellulosic material. Also, TEMPO-mediated oxidised nanocellulose was produced in order to compare the processing route with that of mild organic acid hydrolysis. Freeze-dried 3D structure of TEMPO-derived nanocellulose foam materials made fi-om bleached sulphite pulp and CTMP, respectively. Further, there is growing interest in using nanocellulose or microfibrillated cellulose (MFC) as an alternative paper sfrength additive in papermaking, and in using chemi-thermomechanical pulp (CTMP) with high freeness in producing CTMP-based paperboard with high bulk properties. To achieve greater strength improvement results, particularly for packaging paperboards, different proportions of cationic starch (CS) or MFC can be used to significantly improve the z-strength, with only a slight increase in sheet density. Research in this area is exploring CS or MFC as potential strength additives in CTMP-based paperboard, which is interesting from an industrial perspective. The mean grammage of the CTMP handsheets produced was approximately 150 g m~, and it was found that blending CTMP with CS or MFC yielded handsheets with significantly improved z-strength, tensile index, burst index and other strength properties at similar sheet densities.

  • 9.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Influence of Polymeric Multilayer Treatment on Out-of Plane Properties of CTMP-Based Paperboard2007Doctoral thesis, comprehensive summary (Other academic)
  • 10.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Peng, F.
    Stora Enso, Karlstad.
    Granfeldt, T.
    Valmet, Sundsbruk.
    Bergström, J.
    SCA Östrand, Timrå.
    Joelsson, T.
    MoRe Research, Domsjö.
    Upgrading the strength properties of sheets from hardwood high yield pulps2018In: Pan Pacific Fibre Value Chain Conference 2018, Proceedings, Appita Inc. , 2018, p. 142-147Conference paper (Refereed)
  • 11.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sjöberg, Jessica
    SCA Östrand Mill, SE-86181 Timra, Sweden.
    Peng, Frank
    Stora Enso Res Ctr, SE-65637 Karlstad, Sweden.
    Hallgren, Hans
    Stora Enso Res Ctr, SE-65637 Karlstad, Sweden.
    Moberg, Anders
    Stora Enso Res Ctr, SE-65637 Karlstad, Sweden.
    Ljungqvist, Carl-Henrik
    Stora Enso Res Ctr, SE-65637 Karlstad, Sweden.
    Bergström, Jörgen
    SCA Östrand Mill, SE-86181 Timra, Sweden.
    Solberg, Daniel
    SCA Östrand Mill, SE-86181 Timra, Sweden.
    Strong and bulky paperboard sheets from surface modified CTMP, manufactured at low energy2015In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 30, no 2, p. 318-324Article in journal (Refereed)
    Abstract [en]

    A description is given regarding methods used to manufacture strong and bulky sheets from furnishes based on a broad range of surface modified CTMP qualities. Starch and CMC are adsorbed on the fibre surfaces using a multilayer or a MIX concept. It is shown that both the in-plane and out-of-plane strength for the CTMP based sheets after such surface treatment can be more than doubled at a maintained density. This can be utilized to improve bending stiffness or to reduce the basis weight in multi-ply paperboards.

  • 12.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sjöberg, J. C.
    SCA Östrand Pulp Mill, SE-861 81 Timrå, Sweden .
    Peng, F.
    Stora Enso Research Centre, SE-656 37 Karlstad, Sweden.
    Bergström, J.
    SCA Östrand Pulp Mill, SE-861 81 Timrå, Sweden .
    Solberg, D.
    SCA Östrand Pulp Mill, SE-861 81 Timrå, Sweden .
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Hallgren, H.
    Stora Enso Research Centre, SE-656 37 Karlstad, Sweden.
    Moberg, A.
    Stora Enso Research Centre, SE-656 37 Karlstad, Sweden.
    Ljungqvist, C. -H
    Stora Enso Research Centre, SE-656 37 Karlstad, Sweden.
    Strong and bulky paperboard plies from low energy CTMP2014In: International Mechanical Pulping Conference, IMPC 2014, 2014Conference paper (Refereed)
    Abstract [en]

    A description is given regarding methods used to manufacture strong and bulky sheets from furnishes based on a broad range of surface modified CTMP qualities. Starch and CMC are adsorbed on the fibre surfaces using a multilayer or a MIX concept. It is shown that both the in-plane and out-of-plane strength for the CTMP based sheets after such surface treatment can be more than doubled at a maintained density. This can be utilized to improve bending stiffness or to reduce the basis weight in multi-ply paperboards.

  • 13.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Wågberg, Lars
    Formation of polyelectrolyte multilayers of polyvinylamine/CMC and cationic starch/CMC on birch CTMP and their influence on paper strengthManuscript (preprint) (Other academic)
  • 14.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    KTH, Stockholm.
    The use of polyelectrolyte multilayers of cationic starch and CMC to enhance strength properties of papers formed from mixtures of unbleached chemical pulp and CTMP: Part I2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 1, p. 115-121Article in journal (Refereed)
    Abstract [en]

    The construction of alternating multilayers of cationic potato starch and anionic carboxymethylcellulose(CMC) was investigated in two parts. In the first part, stagnation point adsorption reflectometry (SPAR) showed that the chosen chemicals formed polyelectrolyte multilayers (PEM)upon adsorption to the silicon oxide surface. This was in accordance with earlier work. The chosen polyelectrolytes adsorbed to similar extents on the silicon oxide surface and recharged the surface enough to allow for adsorption of a consecutive layer. In the second part, the multilayer concept was tested on 80/20,20/80% of total in mixture of mixed spruce CTMP and bleached chemical pulp in order to enhance the sheet strength properties of a typical packaging board furnish.. The multilayers yielded a significant improvement in Scott Bond values and tensile index and a marginal improvement in tensile stiffness index. The Scott Bond values were improved more than 150% for papers prepared from a furnish consisting of 80% spruce CTMP and 20% chemical pulp. Polyelectrolyte multilayers treatment also led to a slight densification of the sheets, but the polyelectrolyte multilayers treatment resulted in a more favourable density/strength relationship than that achieved with a change in the amount of chemical pulp.

  • 15.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    KTH.
    The use of polyelectrolyte multilayers of cationic starch and CMC to enhance strength properties of papers formed from mixtures of unbleached chemical pulp and CTMP-II: Part II: Influnence of addition strategy, fibre treatment and fibre type2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 1, p. 122-128Article in journal (Refereed)
    Abstract [en]

    Polyelectrolyte multilayers (PEM) consisting of cationic starch and anionic carboxymethylcellulose (CMC) have been applied to different pulp fibres in order to enhance the out-of-plane sheet strength properties of a typical packaging board furnish. An unbleached softwood chemical pulp was treated with multilayers consisting of two layers of cationic starch and one layer of CMC, and then mixed with different mechanical and chemimechanical pulps. Hand sheets were prepared with the aid of the Rapid Köthen sheet former from stocks consisting of 20% treated chemical pulp and 80% mechanical or chemimechanical pulp, which was either PGW from spruce, HT-CTMP from spruce or birch, or a standard spruce CTMP. Multilayer treatment significantly improved Scott Bond values and in some cases improved the tensile index, with the achieved effects being significantly larger than the effects of applying starch alone. Positive effects were obtained by treating only 20% of the furnish, showing a very high efficiency of the adsorbed multilayers. Compared to earlier work, one important finding was that the PEM treatment should preferably be applied only to the chemical pulp and not on the entire stock. It was possible to increase the out-of-plane strength properties, measured as Scott Bond values, with just a very small increase in density of the sheets. Multilayer treatment of the chemical pulp improved the joint strength between the fibres while maintaining the high bulk of the sheets prepared from the stiff mechanical and chemimechanical fibres.

  • 16.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Strong paper from spruce CTMP2016In: International Mechanical Pulping Conference 2016, IMPC 2016, TAPPI Press, 2016, p. 229-233Conference paper (Refereed)
    Abstract [en]

    This study was carried out on sheets from spruce CTMP fibers, which are surface treated with a mix of cationic starch and CMC and blended with 20% bleach softwood chemical pulp fibers before handsheets were prepared in a Rapid Kothen sheet former, where the sheets were dried to 40-55% d.c. The sheets were pressed in a hot press nip in a pilot machine with adjustable pressure and heat. Both low and high nip pressure were used in combination with two different nip temperatures, 80 °C and 100 °C, to achieve sheets in a broad range of densities. The results show that remarkable improvements are possible, both in terms of tensile index (up to 85 kNm/kg) and compression strength, SCT, (up to 38kNm/kg) on the CTMP-based sheets under optimal conditions at papermaking, i.e. consolidate the sheet structure in a press nip at evaluated temperatures. It is evident from the current study that there is an as of yet unexploited potential in modifying the conditions of papermaking from spruce CTMP furnishes, which can be utilized for the manufacturing of papers with high requirements on strength and stiffness, e.g. packaging papers.

  • 17.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Strong paper from spruce CTMP - Part I2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 1, p. 54-58Article in journal (Refereed)
    Abstract [en]

    This study was carried out on sheets from spruce CTMP fibers, which are surface treated with a mix of cationic starch and CMC and blended with 20% bleach softwood chemical pulp fibers before handsheets were prepared in a Rapid Köthen sheet former, where the sheets were dried to 40-55% d.c. The sheets were pressed in a hot press nip in a pilot machine with adjustable pressure and heat. Both low and high nip pressure were used in combination with two different nip temperatures, 80°C and 100°C, to achieve sheets in a broad range of densities. The results show that remarkable improvements are possible, both in terms of tensile index (up to 85 kNm/kg) and compression strength, SCT, (up to 38 kNm/kg) on the CTMP-based sheets under optimal conditions at papermaking, i.e. consolidate the sheet structure in a press nip at evaluated temperatures. It is evident from the current study that there is an as of yet unexploited potential in modifying the conditions of papermaking from spruce CTMP furnishes, which can be utilized for the manufacturing of papers with high requirements on strength and stiffness, e.g. packaging papers.

  • 18.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Low energy CTMP in strong and bulky paperboard plies2016In: Paper Conference and Trade Show, PaperCon 2016, TAPPI Press, 2016, Vol. 1, p. 556-564Conference paper (Refereed)
  • 19.
    Pettersson, Gunilla
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sjöberg, Jessica
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Wågberg, Lars
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Averheim, Andreas
    Luleå University of Technology.
    Increased joint-forming ability of ductile kraft pulp fibres by polyelectrolyte multilayer treatment-Influence of refining and drying strategies2007In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, no 2, p. 228-235Article in journal (Refereed)
    Abstract [en]

    In this study a sack paper furnish was used. It consisted of a high-consistency kraft pulp refined in either an atmospheric pressure or a pressurized system. The pulps were subsequently low-consistency refined in an Escher-Wyss laboratory refiner to 17.5-20.5 SR. Ordinary ISO sheets and freely dried sheets were manufactured from these pulp samples to serve as reference sheets. The laboratory sheets made of pulp from the pressurized system had a higher strain at break and tensile energy adsorption index but a lower tensile index than sheets made of pulp from a conventional atmospheric highconsistency refiner. These sheets were subject to a polyelectrolyte multilayer treatment to increase the interaction between the fibres, thus enhancing the paper strength properties. The polyelectrolyte multilayers (PEM) were applied by sequentially treating fibres from an unbleached kraft pulp for sack paper production with cationic starch and anionic carboxymethyl cellulose. The multilayer treatment was only applied to 50% of the stock and both ordinary ISO sheets and freely dried sheets were prepared with one and three layers of polyelectrolyte. Evaluation of the strength properties of the sheets showed that the addition of only one layer of starch increased strain at break, tensile index, tensile energy adsorption index, and out-of-plane properties measured as Scott-bond values. Using the multilayer technique created large increases in Scott-bond, a measure of the internal bonding of the sheets. The achieved effects were significantly larger than those usually achieved by applying starch alone to enhance the out-of plane strength properties. Also, the density increased considerably when the third layer was applied, for both ISO and freely dried sheets, though the tensile strength was enhanced significantly only in the freely dried sheets.

  • 20.
    Samuelsson, Tove
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. MoRe Research Örnsköldsvik AB.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Norgren, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Svedberg, Anna
    MoRe Research Örnsköldsvik AB.
    Höglund, Hans
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Development of strong and water resistant packaging materials from high yield pulps – fundamental aspects2018In: IMPC 2018, Trondheim, Norway, 2018Conference paper (Refereed)
    Abstract [en]

    This work is focused on fundamental aspects of the densification of paper sheets during hot-pressing under conditions where the lignin in the fibre walls is softened. In this study light microscope and scanning electron microscope (SEM) techniques were used to reveal the mechanisms in the fibre network structure within the paper sheets that arises due to densification and the impact of lignin. UV and staining methods and spectrometric observations of the ultrastructure of cross section of paper sheets and fibre surfaces will highlight the changes that occur in the fibre structures. This study improves the understanding of how fibres collapse and how internal fibre-fibre bonds in lignin-rich mechanical pulp affect the physical properties of the final paper sheet. To demonstrate this, paper sheets from five different pulps containing different concentration of natural lignin were produced. Handsheets of 150 g/m2 were prepared in a Rapid Köthen (RK) laboratory sheet former, where the sheets were press-dried at 100 kPa and ca 90oC to a dry content of 45-50% d.c. After 24 hours in room temperature the hand sheets were hot-pressed in a temperature interval from 20 – 200oC at a constant pressure in a cylinder-press at a speed of 1 m/min. The results show that remarkable improvements on paper sheets, based lignin-rich pulps, can be achieved in terms of increased tensile index (up to 85 kNm/kg), compression strength, SCT, (up to 38 kNm/kg) and wet strength (up to 10 kNm/kg), which depends on the densification of the fibre structure at high temperature and pressure in the load nip. It is concluded that this to a major extent is related to that the lignin rich fibres are compressed at high enough temperature to both softened and develop tacky surfaces so that the fibres are locked into their positions within the highly densified sheets. The SEM evaluation shows how the surface structure get dense at pressing at 200oC for the CTMP based paper sheets. The light microscopy studies of the sheet cross sections reveal how the fibres collapse in the case of CTMP based sheets while fibres from bleached kraft pulp based sheets are quite well collapsed already at room temperature.

  • 21. Wågberg, Lars
    et al.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Notley, Shannon
    Adsorption of bilayers and multilayers of cationic and anionic copolymers of acrylamide on silcon oxide2004In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 274, no 2, p. 480-488Article in journal (Refereed)
    Abstract [en]

    Silica surfaces were consecutively treated with copolymers of cationic and anionic polyacrylamides (C-PAM and A-PAM, respectively) and the layer-by-layer build-up was continuously monitored with the aid of stagnation point adsorption reflectometry (SPAR). Four different charge densities of the cationic polymer and one charge density of the anionic polymer were studied. The solid substrate used in the investigation was an oxidized Si wafer, the charge of which was varied by performing the measurements at different pH. Adsorption measurements were performed both in deionized water and with a background electrolyte concentration of 0.01 M NaCl The results show that the adsorption of C-PAM at pH 6 was dominated by electrostatic interactions. However, a significant nonionic contribution to the adsorption of C-PAM on SiO2 was detected-when the results of adsorption measurements conducted in deionized water and in 0.01 M NaCl were compared. At pH 9, the adsorption of C-PAM onto SiO2 was found to be geometrically restricted since the adsorption stoichiometry between the polymer charges and the charges on the surface was less than I irrespective of the charge of the C-PAM. Adsorption of the A-PAM onto the C-PAM covered surface increases as a function of the adsorbed charges in the first layer. Experiments showed that it was possible to form multilayers of polyelectrolytes on the SiO2 surface provided the charge of the C-PAM was high enough. The critical charge of the polyelectrolyte for the formation of multilayers was also dependent on the charge of the substrate; that is, the lower the surface charge the higher the critical charge of the C-PAM. The substrate affected the amount of polyelectrolyte adsorbed up to the fifth layer. For further layers there was almost a stoichiometric relationship between the charges of the polyelectrolytes in consecutive layers. Results from studies of the formed multilayers with a quartz crystal microbalance (QCM-D) indicated that there was a close correlation between energy dissipation into the multilayers and a decrease in the adsorption as detected with SPAR. This in turn indicates that a decrease in the reflectometer signal does not necessarily indicate a decrease in adsorption.

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