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  • 1.
    Bohlin, Erik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre.
    Johansson, Caisa
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre.
    Lestelius, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences, Paper Surface Centre.
    Evaluation of ink penetration in porous coatings2012Conference paper (Refereed)
  • 2.
    Deshpande, Raghu
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    The initial phase of the sodium bisulfite pulping of softwood dissolving pulp2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The sulfite pulping process is today practised in only a small number of pulp mills around the globe and the number of sulfite mills that use sodium as the base (cation) is less than five. However, due to the increasing interest in the wood based biorefinery concept, the benefits of sulfite pulping and especially the sodium based variety, has recently gained a lot of interest. It was therefore considered to be of high importance to further study the sodium based sulfite process to investigate if its benefits could be better utilized in the future in the production of dissolving pulps. Of specific interest was to investigate how the pulping conditions in the initial part of the cook (≥ 60 % pulp yield) should be performed in the best way.

    Thus, this thesis is focused on the initial phase of single stage sodium bisulfite cooking of either 100 % spruce or 100 % pine wood chips. The cooking experiments were carried out with either a lab prepared or a mill prepared cooking acid and the temperature and cooking time were varied. Activation energies for different wood components were investigated as well as side reactions concerning the formation of thiosulfate and sulfate.

  • 3.
    Hansson, Björn
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Evaluation of Compression Testing and Compression Failure Modes of Paperboard: Video analysis of paperboard during short-span compression and the suitability of short- and long-span compression testing of paperboard2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objectives of the thesis were to find the mechanisms that govern compression failures in paperboard and to find the link between manufacturing process and paperboard properties. The thesis also investigates two different test methods and evaluates how suitable they are for paperboard grades. The materials are several commercial board grades and a set of hand-formed dynamic sheets that are made to mimic the construction of commercial paperboard. The method consists of mounting a stereomicroscope on a short-span compression tester and recording the compression failure on video, long-span compression testing and standard properties testing. The observed failure modes of paperboard under compression were classified into four categories depending on the appearance of the failures. Initiation of failure takes place where the structure is weakest and fiber buckling happens after the initiation, which consists of breaking of fiber-fiber bonds or fiber wall delamination. The compression strength is correlated to density and operations and raw materials that increase the density also increases the compression strength. Short-span compression and Long-span compression are not suitable for testing all kinds of papers; the clamps in short-span give bulky specimens an initial geometrical shape that can affect the given value of compression strength. Long-span compression is only suitable for a limited range of papers, one problem with too thin papers are low wavelength buckling. 

  • 4.
    Johansson, Christoffer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Analys av Tjocklut med Akustisk Spektroskopi: Prediktering av Torrhalt2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Att driva av vatten ur använd kokvätska (lut) från massakokarna kallas indunstning och är den mest energikrävande processen inom den kemiska massaindustrin. Dock måste det göras för att dessa lutar ska kunna förbrännas i sodapannan och kemikalierna återvinnas. På Gruvöns bruk i Grums innebär samåtervinningen av svartlut och rödlut att beläggningar lättare uppstår på utrustningen och arbetet med att förbättra och effektivisera processen pågår ständigt. Som ett led i detta arbete har luten undersökts med en mätare som bygger på aktiv akustisk spektroskopi. I detta examensarbete har ljudspektrum undersökts i syfte att korrelera dessa till lutens egenskaper med den främsta målsättningen att skapa en modell som kan prediktera torrhalten. Med hjälp av multivariata analysmetoder samt en rad olika förbehandlingar kunde en prediktionsmodell med goda prediktiva egenskaper åstadkommas. Modellen samt ett antal andra intressanta observationer som kan vara av värde för processen redovisas och diskuteras. Även ett flertal vidare arbeten föreslås.

  • 5.
    Kihlman, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Medronho, Bruno F.
    Univ Algarve, Fac Sci & Technol, IBB, CGB, P-8005139 Faro, Portugal..
    Romano, Anabela L.
    Univ Algarve, Fac Sci & Technol, IBB, CGB, P-8005139 Faro, Portugal..
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Lindman, Bjorn
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal.;Lund Univ, Ctr Chem & Chem Engn, Div Phys Chem, S-22100 Lund, Sweden..
    Cellulose Dissolution in an Alkali Based Solvent: Influence of Additives and Pretreatments2013In: Journal of the Brazilian Chemical Society, ISSN 0103-5053, E-ISSN 1678-4790, Vol. 24, no 2, p. 295-303Article in journal (Refereed)
    Abstract [en]

    The distinction between thermodynamic and kinetics in cellulose dissolution is seldom considered in the literature. Therefore, herein an attempt to discuss this topic and illustrate our hypotheses on the basis of simple experiments was made. It is well-known that cellulose can be dissolved in a aqueous sodium hydroxide (NaOH/H2O) solvent at low temperature but it is here shown that such an alkaline solvent can be considerably improved regarding solubility, stability and rheological properties as a whole if different additives (salts and amphiphilic molecules) are used in the dissolution stage. This work probes new aqueous routes to dissolve cellulose, thereby improving the potential to commercially dissolve cellulose in an inexpensive and environmentally friendly manner.

  • 6.
    Ragnarsson, Micael
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Engström, Gunnar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Järnström, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Effects of the Partial Replacement of SB latex with Dextrin Starch on the Thickness Distribution of Coating Layers2008In: Tappi 2008 Advanced Coatings Fundementals Symposium Proceedings, Atlanta: Tappi press , 2008, p. 154-163Conference paper (Refereed)
    Abstract [en]

    A pilot coating trial has been carried out where the synthetic binder in the coating colour was partially replaced with dextrin starch. The coating thickness and the coating thickness distribution were investigated by means of burnout tests and mercury porosity measurements. The coating thickness distribution is governed by the surface profile of the base paper underneath the blade; this surface profile is controlled by the compressibility of the base paper and the blade pressure. Dewatering of the coating colours plasticises the paper and increases its compressibility; a linear relationship between dewatering and the standard deviation in the coating thickness was found for a given blade pressure. The characterization of the coating layers showed a small but measurable increase in the thickness variation for increasing starch content, which was caused by the higher water retention of the starch colours. The surface profile of the uncoated and coated paper was investigated with an optical profilometer. The data from those measurements and the coating thickness distribution investigation were used analytically to calculate the roughness change of the base paper during coating. The roughness change was found to be inversely proportional to the original base paper roughness, indicating that the rougher base paper was more compressible.

  • 7.
    Riedel, Andreas
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Predicting catastrophic failure in barrier coated packaging board and paper after creasing and folding: Proposing a methodology to predict barrier failure after creasing and folding2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Different methods to predict barrier failure in packaging board or paper after converting were investigated. The approach was to compare substrates before and after creasing/folding

    by applying different barrier tests and to propose a methodology to predict failure in the barrier layer. 

    Different coatings were used to develop and verify the methodology; a hemicellulose based dispersion barrier coating, a dispersion coated PVOH coating and an extrusion coated PE. Creasing was performed according to standard procedure using recommended creasing geometries. Folding of paper was performed by a gentle creasing with a board backing followed by folding the paper between two metal plates with a well defined distance.

    The first step in the evaluation was to visually inspect creased/folded substrates by light microscopy to search for coating failures in form of cracks. Both good and bad samples were then tested for grease resistance with a standard test, i.e. TAPPI 454. The TAPPI 454 test showed to be effective to expose barrier failure since oil would penetrate quite fast through the creasing line of cracked samples.

    Even some samples that appeared to have no cracks in the light microscope showed failure with the grease test. The results showed that only the PE coated samples could sustain a barrier after creasing and folding. This was probably due to a high ductility of the PE-coating combined with a high thickness.

    The water vapour transmission rate, WVTR, of the samples that passed the TAPPI 454 test was then measured on the samples that endured the grease resistance test. Since PE is a good water vapour barrier,

    WVTR-measurements were proper for detecting barrier defects. The VWTR of the creased/folded samples was slightly higher for the creased samples than the un-creased references despite the absence of cracks. This was probably due to that the barrier layer got thinner as a result of the strains applied on the coating during the creasing/folding operation. 

    A methodology to predict barrier failure in barrier coated packaging board and paper after creasing and folding was proposed. Well defined creasing and folding geometries were used in combination with screening for cracks in the barrier layer, first by visual inspection in light microscopy and then by a standard grease resistance test. The samples that passed then screening tests could then be analyzed using more exact but also more time consuming methods such as WVTR.

  • 8. Sanchuan, Guo
    et al.
    Heijnesson-Hulten, Anette
    Basta, Jiri
    Greschik, Thomas
    Huaiyu, Zhan
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    THE INFLUENCE OF STORAGE ON BAMBOO PULPS AND PAPER QUALITY2010In: RESEARCH PROGRESS IN PAPER INDUSTRY AND BIOREFINERY (4TH ISETPP), VOLS 1-3, SOUTH CHINA UNIV TECHNOLOGY PRESS , 2010, p. 734-738Conference paper (Refereed)
    Abstract [en]

    This study presents research dealing with the way in which storage affects bamboo pulp fibres and the quality of the resulting paper. Two bamboo pulps, cooked to different kappa numbers and then ECF-bleached to similar levels of ISO-brightness, were used to examine the relationship between refining, storage, pulp/fibre properties and the quality of the final paper sheet more closely. The results of this investigation showed that the effects of refining on pulp fibres are not stable: storing bamboo pulp fibres whilst under agitation had a considerably negative impact on properties such as tensile index, TEA, elongation and burst strength of the paper sheet. These effects were more pronounced at higher degrees of refining and for pulps with higher kappa numbers. The apparent density of the paper sheets decreased with agitated storage, whereas the relationship between density and tensile index strength was not affected. The decreases in strength properties after storage in this study are at least partly due to an increase in the number of kinks per mm fibre and a decrease in the effective fibre length and width. It should be observed that reversed latency in the paper industry introduces quality variations, and has an increased energy demand if a certain tensile index level is to be reached. It is easy for incorrect conclusions to be reached regarding the potential of substituting imported hardwood pulps with domestic bamboo pulps if they are not handled properly when used in a furnish for different final products.

  • 9. Syed, Hanif Uddin
    et al.
    Nebamoh, Ikechukwu Patrick
    BillerudKorsnäs AB.
    Germgård, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    A comparison of cold and hot caustic extraction of a spruce dissolving sulfite pulp prior to final bleaching2013In: Appita journal, ISSN 1038-6807, Vol. 66, no 3, p. 229-234Article in journal (Refereed)
    Abstract [en]

    A magnesium sulfite pulp producer modified its pulping process to dissolving pulping in 2011 and needed a purification stage after the digester to obtain a sufficiently low hemicellulose content. The dissolving pulp was intended for viscose production and an R-18 value of at least 95% and an intrinsic viscosity below 550 dm(3)/kg was requested. The results showed, as could be expected, a correlation between lower dissolving pulp yield and a higher degree Of purification with respect to cellulose. The R-18 values and the intrinsic viscosities of the dissolving pulps were found to increase with increasing sodium hydroxide concentration and/or higher temperature in the extraction Stage. The pulp yield was found to be higher with higher temperature for the cold caustic extraction stage (CCE); for hot caustic extraction (HQ E) the pulp yield became lower with higher temperature. The specified R-18 value was easiest to reach using hot caustic extraction.

  • 10.
    Vera, C. M.
    et al.
    Phenomenex Australia, Pty Ltd, Lane Cove, NSW 2067, Australia.
    Shock, D.
    Phenomenex Australia, Pty Ltd, Lane Cove, NSW 2067, Australia.
    Dennis, G. R.
    Australian Centre for Research on Separation Science, School of Science and Health, University of Western Sydney, Penrith, NSW 2751, Australia.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Shalliker, R. Andrew
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. Australian Centre for Research on Separation Science, School of Science and Health, University of Western Sydney, Penrith, NSW 2751, Australia.
    A preliminary study on the selectivity of linear polynuclear aromatic hydrocarbons in SFC using phenyl-type stationary phases2015In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 121, p. 136-140Article in journal (Refereed)
    Abstract [en]

    The retention behaviour of a homologous series of polyaromatic hydrocarbons was evaluated on two phenyl-type stationary phases in reversed phase supercritical fluid chromatography (SFC). These phases were the Synergi polar-RP phase and the Cosmosil 5PBB phase, both of which are polar end-capped and incorporate an ether in a propyl chain that tethers the phenyl ring to the silica surface. The Cosmosil 5PBB phase also has five bromine atoms on the phenyl ring. The retention capacity of the Cosmosil column was substantially greater than the Synergi column. However, selectivity on the Cosmosil column was effectively independent of the acetonitrile modifier composition in the CO2 mobile phase, whereas, selectivity on the Synergi column was greatly affected by the acetonitrile modifier in the CO2 mobile phase. The results from this study showed that selectivity and retention studies in HPLC cannot be used to predict selectivity and retention behaviour in SFC. (C) 2015 Elsevier B.V. All rights reserved.

  • 11.
    Zeb, Hassan
    Karlstad University, Faculty of Technology and Science.
    Bleaching of Old Newsprint Paper at Metsä Tissue2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
1 - 11 of 11
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