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  • 51.
    Stenberg, Christina
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Cross-linkers, rheology modifiers and lubricants: impact on water retention and rheology of coating colours at various shear rates2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 52.
    Strömberg, Frida
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Humidity’s effect on strength and stiffness of containerboard materials: A study in how the relative humidity in the ambient air affects the tensile and compression properties in linerboard and fluting mediums2016Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this thesis was to investigate the difference between containerboard materials strength and stiffness properties in tension and compression, how the mechanisms behind compressive and tensile properties are affected by the relative humidity of the ambient air and how the relative humidity affects the compressive response of the fibre network. These properties are used to predict the lifetime performance of corrugated boxes and to prevent early collapses of the boxes and thereby waste or harm of the transported goods inside. The work also discusses the methods used to evaluate the different properties and how reliable the results are. The experimental part includes testing of linerboard and fluting materials from both virgin and recycled fibres, which have been conditioned at 50% and 90% relative humidity. The compression tests were filmed to evaluate if different compression failure modes can be related to the strength and stiffness of the material. The results indicated that the compressive strength and stiffness differ from the strength and stiffness values in tension at 90% relative humidity. Compressive strength is lower in both 50% and 90% relative humidity compared with the tensile strength. However, the compression stiffness shows a higher value than the tensile stiffness at 90% relative humidity. The study of the method for evaluating the compressive behaviour of the paper does not present a complete picture on what type of failure the paper actually experience.

  • 53.
    Thorman, Sofia
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Where did the ink go?: The effect of liquid absorption on ink distribution in flexography2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The appearance of a print is affected by the individual ink layers. If the ink is unevenly distributed on the substrate it lowers the quality. This thesis puts focus on how the liquid absorbency of a coated substrate impacts on the ink distribution in flexographic printing. It is well known that a smooth surface increases the chances of a uniform print, whereas the influence from an uneven absorption is not established and has even been difficult to measure. If the ink is applied directly onto the substrate, or as an overprint onto already present ink layers, the outcome is even more complex. Ink trapping behaviour affects the uniformity of overprint layers. As of yet, this been largely overlooked in flexography.

    The work includes several trials, from monochrome laboratory printing at 0.5 ms-1 to multicolour printing at 10 ms-1 in production-scale. These studies showed that ink absorption interacted directly with monochrome ink layers and that pore-structures with larger pores and greater liquid uptake generated more uniform prints. The tolerance of uneven pore-structure, and thereby absorption, varied between samples.

    In multicolour printing, the overprint layer interacted directly with the preceding ink and indirectly with the absorbency (rate and uniformity) of the substrate. Overprint layers became thicker when the first ink layer was thinner and, consequently, turned uneven when the first layer was uneven. Moreover, the time between the applications of the two inks was important. When immobilisation of the first ink was too slow or uneven, it disturbed the ink trapping so that the overprint layer became uneven.

    Output from this project offers a palette of tools to use when studying liquid absorption and its impact on print quality: a) experimental approach to separate the influence of uneven absorption from surface roughness, b) aqueous staining technique to characterise absorption non-uniformity, and c) technique to characterise ink trapping non-uniformity.

  • 54.
    Tran, Tony
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Soap separation efficiency at Gruvön mill: An evaluation of the process before and after a modification2011Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Wood consists not only of cellulose, lignin and hemicellulose but also of so called extractives which includes fats and acids and these components are separated in the mill from the black liquor. These extractives are in the mill denoted as tall oil soap. Tall oil has a large field of applications like chemicals and fuel and as it is produced to the atmosphere if it can replace oil and thus reduce the oil consumption. Tall oil soap is separated from the black liquor in a skimmer and the focus of this thesis was to examine the effect of air injection and the soap layer thickness on the soap separation efficiency in a skimmer. The work was focused on in analyzing the soap content of the inlet and outlet black liquor flow of the skimmer and to detect if an enhancement has been achieved with the two mentioned methods. The reason for the pulp mill to improve the soap separation efficiency was to decrease the risk of foaming and fouling in the evaporator but also to be able to increase the production of tall oil.

    The air injection gave a 41% improvement of the soap separation efficiency and further improvements are probably possible to achieve. The air injection flow was about 7 l air /m3 liquor in the black liquor feed. The airflow lowers the density of soap, creating a greater difference in density between soap and black liquor and this improves the separation efficiency.

    A thicker soap layer could increase the likelihood for soap drops to raise and reach the soap-liquor interface, because the soap drops have the tendency to bind with each other and will be separated from the liquor instead of following with the skimmed liquor outlet (fig. i.2). However, this study shows no indication of improvement with thicknesses that exceeds 0,75- 3,5 m which also endanger the skimmer due to overflow from the skimmer or create a short circuit between the in- and the outlet black liquor flow.

  • 55.
    Tysén, Aron
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013). RISE Bioecon, Drottning Kristinas Vag 61, S-11486 Stockholm, Sweden.;Karlstad Univ, Karlstad, Sweden..
    Thermographic method for quantifying in-plane non-uniform paper drying2018Inngår i: 14TH QUANTITATIVE INFRARED THERMOGRAPHY CONFERENCE, QIRT COUNCIL , 2018, s. 650-657Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A thermographic method has been developed, in order to study in-plane non-uniformity during through air drying of paper tissue products. Non-uniformity in drying of paper is unavoidable, due to the heterogeneous nature of the product. It can be detrimental to the quality of the product, and significantly lower production capacity. The method utilises the endothermic nature of the drying process to quantify non-uniformities. The temperature varies with amount of remaining water. The method is here applied to through air drying of tissue paper, but could also be used for conventional contact drying of other paper grades.

  • 56.
    Ulfstad, Louise
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Rheological study of cellulose dissolved in aqueous ZnCl2: Regenerated cellulosic fibres for textile applications2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The most known regenerated cellulosic fiber is viscose, produced in a wet spinning process, but due to cost and environmental issues other processes have been developed. Lyocell fibers, produced in air-gap spinning, have superior dry and wet strenght and a lower environmental impact compared to viscose. Research in different cellulose solvent has increased significantly tha last decadess, due to an increased cotton price and a decreased paper production, providing more wood pulp to production of regenerated cellulosic fibers.

     

    Inorganic molten salt hydrates have the ability of dissolving cellulose for production of textile fibers. Aqueous zinc chloride was investigated at Swerea IVF from dissolution of cellulose to fiber spinning.

     

    Aqueous zinc chloride has a dissolving capacity of up to at least 13.5 % cellulose, possibly much higher. Dissolving concentration ZnCl2/water range from 65-76 % amd lowest possible ZnCl2 concentration increases as the cellulose concentration increases. Above around 68 % ZnCl2 results in a significantly increased viscosity due to a polymeric structure formed by zinc chloride, creating a network of cellulose-zinc complexes and causing a gel behaviour of the dope difficult to use in spinning processes. The dissolving capacity of 68 % ZnCl2 is only about 8 % cellulose, which is very low compared to other solvents used today e.g. Lyocell and ILs.

     

    Additions of 0.3 % CaCl2 or 0.05-0.1 % NaOH is used to decrease degradation of cellulose. The addition causes ans increased viscosity, which is either a result of less degradation of the interaction of the added molecules to zinc-cellulose complexes. Addition of NaOH results in a temperature dependent geleation at increased temperatures (75˚C and 80˚C), which also might be an effect of the interaction.

     

    Highest tensile strenght was reached for wet spun fibers coagulated in ethanol of 9.5 % cellulose with 0.1 % NaOH addition, with a tenacity of 13-15 cN/tex, elongation of 10-12 % and wet strenght 30 % of dry strenght. Beacuse of many disadvantages of zinc chloride as a solvent, e.g. degradation of cellulose, corrosivity and the viscosity and gel behaviour at cellulose concentrations of 9.5 % and 13.5 % cellulose, a future possibility of a conventional production of textile fibers appears to be quite limited. 

  • 57.
    Wickholm, Kristina
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi.
    Williams, Helén
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lindström, Annika
    Innventia.
    Lorentzon, Ann
    Innventia.
    Wikström, Fredrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Innovative packaging for reduction of food waste from producer to consumer2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Increasing population and environmental changes poses a significant pressure on the global food supply chain. With the large quantities of food waste that’s been reported over the past couple of years packaging can play a more significant role in reducing the food wastage. Together with actors along the entire value chain we are developing new innovative packaging solutions to reduce food waste throughout the value chain, from food producers to consumers. The purpose of the study is to design and optimize new packaging system solutions so that no part of the chain is optimized at the expense of any other part. In the fall of 2015 the food wastage was examined in three supply chains, salsa in glass jar (A), rice pudding in plastic packaging (B) and lettuce in plastic packaging (C), by using waste audits in the businesses, collecting, comparing and analyzing data. For consumer insights ethnographic studies was used in ten Swedish households. Interviews have also been conducted with consumers in retail stores. The supply chain study indicates little wastage for A and B and higher for C. Consumer report some handling difficulties with the food packaging and reasons why food is wasted. The main reasons being that the food gets bad, difficulties to empty the packaging and that the amount of food is higher than their needs. A majority of the consumer state that they often view packaging as something unnecessary. Consumers do not give packaging functions many thoughts in general and many have difficulties in judging the packaging functions.

  • 58.
    Wilke, Caroline
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Fördröja åldrandet av elektrotekniskt papper genom kemikalietillsats: En studie av dicyandiamids påverkan2011Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Nordic Paper Åmotfors tillverkar elektrotekniskt papper som används till att isolera lindningarna i transformatorer. Det är viktigt att bibehålla papprets egenskaper under en mycket lång tid då en transformators livlängd är lång. Syftet med detta examensarbete var att undersöka huruvida tillsats av en kemikalie bestående av dicyandiamid kan fördröja åldrandet av de papper som Nordic Paper tillverkar. Förhoppningen var att deras papper därefter skulle klara de krav-parametrar som finns för papper som åldrats i olja. Kemikalien som användes var Cartafix® WE liquid.

    Försök utfördes där olika kemikaliedoseringar tillsattes i mälden. Pappersark tillverkades och kvävehalten mättes därefter för att verifiera att kemikalien fastnat i de färdiga papprena. Pappers-arken åldrades sedan endera i olja eller i luft, och den kvarvarande polymerisationsgraden (DP) mättes. Sprängstyrke- och konduktivitetstester utfördes också. Papper som Nordic Paper tillverkat beströks med olika kemikaliedoseringar och samma tester utfördes även på dessa.

    Resultaten visade att retentionen av kemikalien var låg. Kvävehalten blev inte högre än 1 % och detta skedde vid 10-20 % kemikalietillsats.

    Efter åldring i olja minskade DP relativt mycket, vilket medförde att papprena inte uppnådde de uppsatta kraven (maximalt 50 % minskning). Tillsats av kemikalien förbättrade dock papprets åldringsegenskaper med nästan 45 % om icke-modifierat papper jämförs med det modifierade pappret som hade högst DP (10 % kemikalietillsats, vilket motsvarade 1 % kvävehalt).

    Papper som modifierats med kemikalietillsats i mälden gav lägre DP då åldringen skett i luft jämfört med icke-modifierat papper. DP minskade avsevärt efter åldring för papper som bestrukits med kemikalien.

    Kemikalietillsats försämrade både sprängstyrkan och konduktivteten.

  • 59.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Some aspects on the activation of dissolving pulps and the influence on the reactivity in a following viscose stage2013Inngår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 47, nr 3-4, s. 165-169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It was found that, for a dissolving pulp, an enzymatic pre-treatment with an endoglucanase prior to viscose preparation did not change the correlation between the gamma number of the viscose dope and the carbon disulphide charge. Thus, the pulp stoichiometry, or reactivity, was not changed by an endoglucanase pre-treatment. It has nevertheless previously been found that the pulp reactivity, measured either by Fock's test or as the filter clogging value (Kw), increased for the same type of enzyme pre-treatment. Thus, the pulp reactivity seems to be influenced by the analysis method employed.

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