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  • 1.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Extended Mercerization Prior to Carboxymethyl Cellulose Preparation2011Conference paper (Other (popular science, discussion, etc.))
  • 2.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Enzyme treatment of dissolving pulps as a way to improve the following dissolution of the fibres2012Conference paper (Other academic)
  • 3.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jardeby, Kristina
    Borregaard Chemcell, Sarpsborg, Norge.
    Kreutz, Björn
    Borregaard Chemcell, Sarpsborg, Norge.
    The influence of mercerization on the degree of substitution in carboxymethyl cellulose2009Conference paper (Other (popular science, discussion, etc.))
  • 4.
    Almlöf Ambjörnsson, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Schenzel, Karla
    Marthin-Luther University Halle-Wittenberg.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Characterization of CMC by NIR FT Raman spectroscopy2012Conference paper (Other (popular science, discussion, etc.))
  • 5.
    Almlöf, Heléne
    Karlstad University, Faculty of Technology and Science, Avdelningen för kemiteknik.
    Extended Mercerization Prior to Carboxymethyl Cellulose Preparation2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carboxymethyl cellulose (CMC) is produced commercially in a two-stage process consisting of a mercerization stage, where the pulp is treated with alkali in a water alcohol solution, followed by an etherification stage in which monochloroacetic acid is added to the pulp slurry. In this thesis an extended mercerization stage of a spruce ether pulp was investigated where the parameters studied were the ratio of cellulose I and II, concentration of alkali, temperature and retention time. The influence of the mercerization stage conditions on the etherification stage, were evaluated as the degree of substitution (DS) of the resulting CMC and the filterability of CMC dissolved in water at a concentration of 1%. The DS results suggested that the NaOH concentration in the mercerization stage was the most important of the parameters studied. When the NaOH concentration in the mercerization step was low (9%), a high cellulose II content in the pulp used was found to have no negative impact on the DS of the resulting CMC compared with pulps with only cellulose I. However, when the NaOH concentration was high (27.5%), pulps with high content of cellulose II showed a lower reactivity than those with only cellulose I with respect to the DS of the CMC obtained after a given charge of NaMCA.

    The results obtained from the filtration ability study of CMC water solutions suggested that both the amount of cellulose II in the original pulp and the temperature had a negative influence on the filtration ability whereas the NaOH concentration in the mercerization stage had a positive influence. The filtration ability was assumed to be influenced highly by the presence of poorly reacted cellulose segments. A retention time between 1-48 h in the mercerization stage had no effect on either the DS or the filtration ability of the CMC.

    Using NIR FT Raman spectroscopy molecular structures of CMC and its gel fraction were analyzed with respect to the conditions used in the extended mercerization stage. Here it was found that the alkaline concentration had a very strong influence on the following etherification reaction. FT Raman spectra of CMC samples and their gel fractions prepared with low NaOH concentrations (9%) in the mercerization stage indicated an incomplete transformation of cellulose to Na-cellulose before carboxymethylation to CMC. Low average DS values of the CMC, i.e. between 0.42 and 0.50, were yielded. Such CMC dissolved in water caused very thick and semi solid gum-like gels, probably due to an uneven distribution of substituting groups along the cellulose backbone. FT Raman spectra of CMC mercerized with alkaline concentrations at 18.25 and 27.5% in the mercerization stage indicated, however, that all of the cellulose molecules were totally transferred to CMC of high DS, i.e. between 0.88 and 1.05. When dissolved in water such CMC caused gels when they were prepared from ether pulp with a high fraction of cellulose II.

  • 6.
    Almlöf, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Guo, Sanchuan
    Heijnesson-Hulten, Anette
    The Effect of Stock Storage on The Quality of Bamboo Kraft Pulp2010In: O PAPEL, ISSN 0031-1057, Vol. 72, no 6, 43-53 p.Article in journal (Refereed)
  • 7.
    Almlöf, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Kreutz, Bjørn
    Borregaard Chemcell, Norway.
    Jardeby, Kristina
    Borregaard Chemcell, Norway.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    The influence of extended mercerization on some properties of carboxymethyl cellulose (CMC)2012In: Holzforschung, ISSN 0018-3830, Vol. 66, 21-27 p.Article in journal (Refereed)
    Abstract [en]

    Carboxymethyl cellulose (CMC) is produced commercially in a two stage process consisting of a mercerization stage in which the pulp is treated with alkali in a water alcohol solution and a second etherification stage whereby monochloro-acetic acid is added to the pulp slurry. In this study, the influence of the conditions of an extended mercerization stage was evaluated on the etherification stage concerning the degree of substitution (DS) and the filterability of the resulting CMC. The parameters studied were: (1) the ratio of cellulose I and cellulose II in the original pulp, (2) the concentration of alkali, (3) the temperature and (4) the retention time in the mercerization stage. The DS results indicate that the NaOH concentration in the mercerization stage is the most important among the parameters studied. When the NaOH concentration in the mercerization stage was high (27.5%), cellulose II showed a lower reactivity than cellulose I with respect to the DS obtained in the resulting CMC. The results from the filtration ability of CMC water solutions are interpreted that the amount of cellulose II in the original pulp and the temperature has a negative influence, while the NaOH concentration in the mercerization stage has a positive influence on the filtration ability. Retention time between 1 h–48 h in the mercerization stage had no effect on the DS or the filtration value. The filtration ability was assumed to be highly influenced by the presence of poorly reacted cellulose segments. The CMC samples with the lowest filtration ability at a given DS can be assumed to have the highest degree of unevenly substituted segments.

  • 8.
    Almlöf, Heléne
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Schenzel, Karla
    Department of Natural Science III, Institute of Agriculture and Nutritional Science, Martin Luther University, Germany.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Carboxymethyl cellulose produced at different mercerization conditions and characterized by NIR FT Raman spectroscopy and chemometric methods2013In: BioResources, ISSN 1930-2126, Vol. 8, no 2, 1918-1932 p.Article in journal (Refereed)
  • 9.
    Anderson, Fredrik
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Rheological changes at the air-liquid interface and examining different kind of magnetic needles2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main objective in this work was to learn how the instrument, the Interfacial Shear

    Rheometer (ISR400), worked and to investigate how the rheological properties, storage

    modulus (elasticity), G' and loss modulus (viscous), G'', changes when the surface

    pressure at the air-liquid interphase changes. The second objective were to examine the

    different kind of magnetic needles used in the experiments and to conclude which type of

    needle is best for its specific field of analysis.

    It was concluded that the relative heavy needle with mass 70.6 mg and length 50 mm

    was best for systems where the viscous and elastic components are significantly large,

    where the inertia of the needle is not dominant. It also worked of using the heavier needle

    for a system of phospholipids.

    For the hydroxystearic acid (HSA) experiment that were tested on NaCl sub-phase there

    was a clear improvement after switching from the heavy needle (mass 41.5 mg; length 51

    mm) to the relative lighter needle (mass 6.94 mg; length 34.7 mm). The values for the

    dynamic modulus therefore had a better agreement with reference literature.

    A spread layer of class II hydrophobins (HFBII) could be compressed to a surface

    pressure of 46 mNm-1. The G' and G'' values from the frequency sweep were discarded

    because the monolayer turned into a very viscous-like liquid, and the oscillating needle,

    after compression, was kind of stuck in the sub-phase and moved very staggering during

    a frequency sweep.

    The needle comparison experiment with silica particles 10 wt% Bindzil CC30 (BCC30),

    at pH 3.5 was done to see if there was any difference in the sensitivity for the needles at

    the interface which consisted of a pure 10 mM NaCl solution or a 10 mM NaCl solution

    with BCC30 added to it. The differences were negligible in terms of surface tension but

    there was a clear difference between the heavy needle and the light needle, when

    oscillating at higher frequencies (>≈6 rad/s).

    With this study, the understanding of ISR400 has increased largely. Several issues have

    been addressed and the results provide a good basis for further studies within the many

    areas the instrument can be used for. Despite the project's time limit, and the fact that the

    instrument was new and untested where the project was carried out, focus areas were

    prioritized so good results could be achieved within reasonable goals.

  • 10. Andersson, Caisa
    et al.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Water-vapour permeability of barrier dispersion coating2001Conference paper (Other (popular science, discussion, etc.))
  • 11. Andersson, Niclas
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Johansson, Kristina
    Ljungqvist, Carl-Henrik
    Thuvander, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Determining the strain to failure for constrained pulp fibres by means of single-fibre fragmentation2002In: Appita Journal 55(2002)3, 224-229Article in journal (Refereed)
  • 12. Andersson, Niclas
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Johansson, Kristina
    Ljungqvist, Carl-Henrik
    Thuvander, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Determining the strain to failure for constrained pulp fibres by means of single-fibre2002In: Appita Journal, Vol. vol 55 no 3Article in journal (Refereed)
  • 13.
    Andersson, Niclas
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Wilke, Caroline
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Biazzo, Tom
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    van Fleet, Rick
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A new sensor and a novel control consept for optimized fiberline operationManuscript (preprint) (Other academic)
  • 14. Andersson, Niclas
    et al.
    Wilson, David
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Model based kraft cooking optimisation2003In: Nordic Pulp and Paper Research Journal, Vol. vol 18 no 4Article in journal (Refereed)
  • 15. Andersson, Niclas
    et al.
    Wilson, David
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Using validated continuous kraft digester models for profile optimisation2002Conference paper (Refereed)
  • 16. Andersson, Niclas
    et al.
    Wilson, David
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Validating continuous kraft digester kinetic models with online NIR measurements2002Conference paper (Refereed)
  • 17. Andersson, Niclas
    et al.
    Wilson, David
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    An improved kinetic model structure for softwood kraft cooking2003In: Nordic Pulp and Paper Research Journal, Vol. vol 18 no 2Article in journal (Refereed)
  • 18. Andersson, Niclas
    et al.
    Wilson, David
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Lindström, Tomas
    Organic matter content in black liquor inside and outside chips during kraft cooking2001In: Paperi ja Puu, Vol. vol 83 no 7Article in journal (Refereed)
  • 19. Backfolk, K.
    et al.
    Johansson, Caisa
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre.
    Peltonen, J.
    Association between a sodium salt of a linear dodecylbenzene sulphonate and a non-ionic fatty alcohol ethoxylate surfactant during film formation of styrene/butadiene latex2006In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006, 291 (1-3), 38-44Article in journal (Refereed)
  • 20.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Beghello, L
    Magnetic printing for packaging industry: methods and feasibility2006Conference paper (Refereed)
  • 21.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, Per-Lennart
    Östlund, Sören
    Hallbäck, Nils
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Karathanasis, Michael
    On material characterization of paper coating materials by microindentation testing2005In: JCT: Journal of Coatings Technology, ISSN 0361-8773, Vol. 2, no 6, 463-471 p.Article in journal (Refereed)
    Abstract [en]

    Microindentation as a method for determining important material properties of paper coating materials is studied experimentally and numerically. The bulk of the investigation is concentrated upon the short-lived elastic part of a spherical indentation test, but determination of the failure stress of the coating is also discussed. The results indicate that microindentation can be a powerful tool for material characterization of these materials, but only if careful efforts are made to account for the influence from plasticity as well as from boundary effects

  • 22.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, PL
    Östlund, S
    Numerical investigation of folding of coated papers2005In: Composite StructuresArticle in journal (Refereed)
    Abstract [en]

    Folding of coated paper is examined numerically using the finite element method. Particular emphasis is put on the behaviour of field variables relevant for cracking of the coating layers. In the numerical analysis, the basepaper is modelled as an anisotropic elasticplastic material (both elastic and plastic anisotropy is accounted for) while the constitutive behaviour of the coating layers are approximated by classical (Mises) elastoplasticity. The numerical results suggest, among other things, that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. It is also shown that delamination buckling, in the present circumstances, will have a very small influence on the strain levels in the coating layer subjected to high tensile loading

  • 23.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, PL
    Östlund, S
    On dynamic effects at folding of coated papers2005In: Composite StructuresArticle in journal (Refereed)
  • 24.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, PL
    KTH Stockholm.
    Östlund, S
    On the effect of high anisotropy at folding of coated papers2007In: Composite structures, ISSN 0263-8223, Vol. 72, no 3, 330-338 p.Article in journal (Refereed)
    Abstract [en]

    A finite element procedure, developed in order to account for the effect of high anisotropy at folding of coated papers, is presented. The anisotropic behaviour (with very low stiffness in the thickness direction) is modelled using stiff structural elements (trusses and beams). The numerical results indicate that high elastic anisotropy leads to lower strain levels at folding than reported in previous analyses where this effect was not accounted for. High plastic anisotropy, on the other hand, will contradict this result

  • 25.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, PL
    KTH Stockholm.
    Östlund, S
    Experimental investigation of damage at folding of coated papers2002In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 17, no 1, 34- p.Article in journal (Refereed)
    Abstract [en]

    To achieve a better understanding of the folding properties of coated papers pertinent to the mechanical behaviour, a microscopic investigation was performed. The influence on the damage levels in the coating from such features as delamination, humidity and paper thickness have been studied

  • 26.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Larsson, PL
    Östlund, S
    Eklund, J
    Folding of printed papers: experiments and numerical analysis2003Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Folding of digital prints has been investigated experimentally in order to determine the influence from different features on the residual strength of the folded paper. In particular, the effect of toner-layer, paper-fibre orientation and pre-creasing is investigated and the experimental results are supplemented with numerical ones based on the finite element method. The results indicate that creasing, and to a less extend also fibre orientation, is the most important factor influencing the residual tensile strength after folding

  • 27.
    Barbier, Christophe
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Rättö, Peter
    Hornatowska, Joanna
    Coating models for an analysis of cracking behavior between folded paper and creased board2012Conference paper (Refereed)
    Abstract [en]

    Creasing coated carton board or folding coated magazine paper, result in large strains in the surface layer of the paper product and might result in surface cracks, which decrease the quality of the products. A better understanding of the mechanical properties of coated layers increases the knowledge needed to reduce crack formation in coated fiberbased materials.The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and a Ground Calcium Carbonate (GCC) pigment were used. The binder was either an S/B latex or an S/B latex combined with starch.

  • 28.
    Barros, Gustavo Gil
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Johansson, Per-Åke
    STFI-Packforsk AB, Stockholm, Sweden .
    Prediction of UnCovered Area occurrence in flexography based on topography: A feasibility study2006In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 21, no 2, 172-179 p.Article in journal (Refereed)
    Abstract [en]

    This investigation concerns the development and prediction of uncovered areas (UCA) in flexographic full-tone prints based purely on substrate topographic information. Four different predictive models based on topography thresholding were proposed and tested using two independent quality judgement criteria. 

  • 29.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre.
    A New Generation of Durable Banknote Paper1999Conference paper (Other (popular science, discussion, etc.))
  • 30. Bergström, L.
    et al.
    Sjöberg, M.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Concentrated Kaolinite Suspensions - Polymer Adsorption and Rheological Properties1996In: in "Science of Whitewares", ed. by V.E. Henkes, G.Y. Onoda and W.M. Carty, American Ceramic Society, Westerville, OH, 1996, pp. 65-77 / [ed] V.E. Henkes, G.Y. Onoda and W.M. Carty, 1996Chapter in book (Refereed)
  • 31. Bjorklund, R.B.
    et al.
    Arwin, H.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Adsorption of Anionic and Cationic Polymers on Porous and Non-Porous Calcium Carbonate Surfaces1994In: Appl.Surf.Sci.,75,197(1994)Article in journal (Refereed)
  • 32. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    The influence of softwood kraft cooking conditions on the brightness development in ECF- bleaching2003Conference paper (Refereed)
  • 33. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    The influence of softwood kraft cooking conditions on the brightness development in ECF- bleaching2004In: Appita Journal, Vol. vol 57 no 3Article in journal (Refereed)
  • 34. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Effect of cooking conditions on ECF bleaching and brightness reversion of birch kraft pulp2005In: Tappi JournalArticle in journal (Refereed)
  • 35. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Formation of AOX and OCI in ECF-bleaching of birch pulp2004In: Tappi Journal 3(2004)8, 7-11Article in journal (Refereed)
  • 36. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Formation of AOX and OCl in ECF-bleaching of birch pulp2004In: Tappi Journal, Vol. vol 3 no 8Article in journal (Refereed)
  • 37. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, AnnBritt
    TCF and ECF bleaching effluent COD at varying kappa numbers after cooking2003In: Appita Journal, Vol. vol 56 no 3Article in journal (Refereed)
  • 38. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, AnnBritt
    TCF and ECF bleaching effluent COD at varying kappa numbers after cooking2003In: Appita Journal 56(2003)3, 200-205Article in journal (Refereed)
  • 39. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, Ann-Britt
    AOX formation in ECF bleaching at different kappa numbers: Influence of oxygen delignification and hexenuronic acid content2002In: Tappi Journal, 1(2002)7, 20-24, Vol. vol 1 no 7Article in journal (Refereed)
    Abstract [en]

    he aim of this study was to determine how oxygen delignification before bleaching and the hexenuronic acid (HexA) content of the pulps influenced the acisorbable organic halogen (AOX) formation in the elemental chlorine free (ECP) bleaching effluent. Softwood industrial chips cooked to different kappa numbers were oxygen defignified, treated in a hot acid stage (A*), or not pretreated at all before ECF bleaching. We compared the AOX levels in the ECF effluents from bleaching of these pulps. There was a higher formation of AOX for oxygen delignified pulps than for non-oxygen delignified pulps compared at the same kappa number before ECF bleaching. The hexenuronic acid (HexA) content of the pulps had a major impact on the AOX levels in the D[0] effluent. The oxygen delignified pulps had a higher HexA content than the non-oxygen delignified pulps compared at the same kappa number. This explains the higher AOX formation from oxygen delignified pulps. The AOX originating from HexA was not stable upon storage. Application, This study gives additional insight on the AOX formation in ECF bleaching. The information may be used to take appropriate measures when addressing environmental issues

  • 40. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, Ann-Britt
    AOX formation in ECF bleaching at different kappa numbers ' influence of oxygen delignification and hexenuronic acid content2001Conference paper (Refereed)
  • 41.
    Bohlin, Erik
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Optics of coated paperboard: Aspects of surface treatment on porous structures2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Calendering of coated and uncoated paper is widely used to enhance optical properties such as gloss and print quality. The aim of this thesis is to characterize coatings and prints, and to validate models using experimental results from optical measurements of physical samples.

    Calendering of coated paper often leads to a brightness decrease. The mechanism for this is not altogether clear. One common explanation is that the porosity of the coating layer decreases and hence the scattering decreases. By comparing simulated and measured results it was shown that modifications of the surface properties account for the brightness decrease of ground calcium carbonate coated substrates with calendering. Monte Carlo light scattering simulations, taking into account the measured decrease of surface microroughness and increased effective refractive index, showed that surface modifications accounted for most of the observed brightness decrease of the ground calcium carbonate coated substrate, whereas the bulk scattering and absorption coefficients were not affected by calendering. It was also shown that the scattering coefficient is significantly dependent on the coat weight whereas the physical absorption coefficient is not.

    The penetration of ink in the z-direction of a substrate influences the quality of the print. The ink penetration affects print density, mottling and dot gain, common print effects that influence the preference of consumers. The pressure in the printing nip and the porosity of the substrate both affect the amount of ink that is pressed into the porous structure of a coating layer during printing. By printing pilot coated paperboard with different coating porosity and measuring the resulting optical properties of the prints, a basis for simulations of the different layers, that is to say the coating, the print and the mixed layer in between, was created. Results show that ink distribution is strongly affected by the roughness of the substrate. Fibres and fibre flocks underneath the two coating layers created an unevenly distributed coating thickness that affected the print quality. Differences in pore size and pore size distribution also affected the behaviour of the ink. A coating layer of broad pigment particle size distribution resulted in a relatively low print density, in comparison to coatings of narrowly distributed particle sizes. Comparison of dot gain showed that the coating layer of a narrow particle size distribution had a relatively low dot gain compared to others. In this work, these results are explained by the differences in ink distributions on and in the coating layers.

  • 42.
    Bohlin, Erik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Coppel, Ludovic
    Innventia AB, Stockholm, Sweden.
    Andersson, Caisa
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Edström, Per
    Mid Sweden University.
    Characterization and modelling of the effect of calendering on coated polyester film2009In: Advances in Printing and Media Technology: Vol XXXVI, 2009, 301-308 p.Conference paper (Refereed)
    Abstract [en]

    Polyester films were coated with a coating colour based on a ground calcium carbonate with narrow particle size distribution. Four different coat weights were produced. The coated sheets were calendered and the samples were exposed to up to twenty nips in the calender at a line load of 300 kN/m at 50°C. The brightness and the thickness were measured after each calendering nip. Reflectometry was used to measure the refractive index and the microroughness of the samples. Calendering lead to a decrease of the Kubelka-Munk scattering coefficient and an increase of the absorption coefficient of the coated transparent films. Taking into account non-uniform surface reflection at the boundaries between media of different refractive indices, a large part of the reflectance decrease due to calendering could be attributed to an increase of the effective refractive index at the coating surface and a decrease of the surface microroughness.

  • 43.
    Bohlin, Erik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Coppel, Ludovic
    Innventia AB, Stockholm, Sweden.
    Johansson, Caisa
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Edström, Per
    Mid Sweden University.
    Modelling of Brightness Decrease of Coated Cartonboard as an Effect on Calendering: Microroughness and Effective Refractive Index Aspects2010In: TAPPI 11th Advanced Coating Fundamentals Symposium, Munich, Germany, 2010: Symposium Proceedings, Norcross, GA, USA: TAPPI Press, 2010, 51-65 p.Conference paper (Refereed)
    Abstract [en]

    Calendering of coated paper leads to a brightness decrease. The mechanism for this is not clear, although it has been discussed in the past. One common explanation is that the porosity of the coating layer decreases and hence scattering. By comparing simulated and measured results this paper shows that modifications of the surface properties account for the brightness decrease of GCC coated substrates with calendering. The effect of a deformable cartonboard substrate is investigated here and compared to a less deformable plastic film substrate. From simulations based on a two-layer Kubelka-Munk model, it is shown that the brightness decrease of the cartonboard due to calendering has a negligible contribution to the brightness decrease of the coated cartonboard. The brightness decrease was similar for coated plastic film and coated cartonboard. The thickness of GCC coated plastic films was not affected by calendering irrespectively of the pigment and latex size distribution. Monte Carlo light scattering simulations, taking into account the measured decrease of surface microroughness and increased effective refractive index, showed that surface modifications accounted for most of the observed brightness decrease of the GCC coated substrate, whereas the bulk scattering and absorption coefficients were not affected by calendering. It is also shown that the scattering coefficient is significantly dependent on the coat weight whereas the physical absorption coefficient is not.

  • 44.
    Bohlin, Erik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Johansson, Caisa
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Lestelius, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Flexographic Ink-Coating Interactions, Effects of Porous Structure Variation of Coated Paperboard2012Conference paper (Refereed)
  • 45.
    Boudreau, Jonna
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A close-up on Yankee coating - for better control2007Conference paper (Other (popular science, discussion, etc.))
  • 46.
    Boudreau, Jonna
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Improvement of the tissue manufacturing process2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The creping process and the conditions on the Yankee cylinder are the key factors in the production process. They need to be kept under good control in order to maintain a high and uniform quality. A natural coating always develops on the surface of the Yankee cylinder due to evaporation from dissolved and dispersed substances and to fiber fragments that remain on the surface after creping. Nevertheless, coating chemicals are sprayed onto the Yankee surface in order to modify the adhesion between the paper and the dryer cylinder. To be able to control the process, on-line measurements of coating thickness as well as of the crepe structure of the tissue paper produced would be very valuable. In the work described in this thesis, the coating layer was analyzed chemically and morphologically to provide information about the coating layer before starting any on-line measurements. The chemicals added and the constituents of the pulps are known to the paper producers, but what is left on the cylinder and whether there are different layers of coating still remain to be investigated. The chemical analysis indicated that the adhesive content was higher in an inner layer of the coating than in the outer layer. The relative amount of polyamide-amine resin calculated on the basis of the nominal nitrogen content in the resin was low indicating that the coating consisted of a significant amount of carbohydrates or other substances. The coating layer could not be considered transparent. It was observed that the coating was thick and appeared patch-wise and that it contained fiber fragments. Measurements on a laboratory scale, to further be applied on-line on the tissue machine, have been investigated and evaluated in this study. The thickness of the coating layer on a laboratory dryer has been measured. The method was based on fluorescence with an optical brightener added to the coating chemicals sprayed on the Yankee dryer. With a UV-LED (Ultra Violet - Light Emitting Diode) the coating layer was exposed to UV-light and the intensity of the light emitted by the optical brightener in the layer was measured. The intensity in the trials with different thickness of the coating and no coating was scattered and no trend could be seen between the different trial points. Attempts were made to measure the wavelength of the tissue paper produced with an optical fiber perpendicular to and at an angle to the paper surface. The paper was travelling in a slow speed while the measurements were made. The collected signal to noise ratio was low and it was not possible to detect any representative characteristic wavelength of the tissue.

  • 47.
    Boudreau, Jonna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    A Method of Measuring the Thickness of the Coating on a Dryer Cylinder2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 24, no 3, 309-312 p.Article in journal (Refereed)
  • 48.
    Boudreau, Jonna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Experiments to Find Online Measurements of the Structure of the Tissue Paper SurfaceManuscript (Other (popular science, discussion, etc.))
  • 49.
    Boudreau, Jonna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Hollmark, Holger
    Beghello, Luciano
    Method for analyzing cylinder coating on tissue machines2008Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Samples of coating have been taken at different positions on a running Yankee cylinder

    to analyze the content. The scrapings of the coating were obtained by collecting material

    from the cleaning doctor and by scraping coating with a hand scraper in between the

    cleaning doctor and the spray boom. The conditions on the Yankee dryer surface were

    varied by varying specific creping additives. Chemical and morphological analyses were

    made on the samples. The chemical analysis comprised carbohydrate analysis and

    nitrogen analysis. Analyses of the scrapings were compared with analyses of the creped

    paper. Replicas of the coating layer were made with a silicon rubber to show the

    microstructure. The coating was thick and appeared patch-wise and it contained fiber

    fragments. The chemical analysis indicates that the nitrogen content was higher for the

    coating close to the cylinder. The sampling method seems to work well, since the

    nitrogen content increases with an increased amount of applied adhesive

  • 50.
    Boudreau, Jonna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Hollmark, Holger
    Hollmark Imptec AB.
    Beghello, Luciano
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Chemical and Morphological Analyses of the Tissue Yankee Coating2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 24, no 1, 52-59 p.Article in journal (Refereed)
1234567 1 - 50 of 514
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