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  • 1.
    Fjellström, Helena
    et al.
    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.
    Htun, Myat
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    On the relationship between wood fibre wall swelling, charged groups, and delamination during refining2013In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 3, no 4, p. 30-34Article in journal (Refereed)
    Abstract [en]

    The influence of sulphonic and carboxylic acid groups in combination with the effect of counter-ion form on the swelling capacity of mechanical pulp fibres was studied by means of water retention value (WRV) measured in the temperature range from 25oC to 95oC. Mechanical pulp fibres (TMP) were treated with hydrogen peroxide, sodium sulphite, or both under conditions resembling those used in chemi-thermomechanical and bleaching processes commonly used in the industry. In conventional chemi-thermo-mechanical processes, sulphite treatment is used before refining, whereas peroxide treatment can be used both before and after refining. However, in this study, sulphite was also used after peroxide treatment. When sodium sulphite-treated pulps are subjected to a subsequent hydrogen peroxide step, all pulps show a decrease in sulphonic acid groups, which can be attributed to dissolution of highly charged lignin. Pulps treated with a high hydrogen peroxide charge (4%) show a loss in carboxylic acid groups during subsequent treatment with sodium sulphite. This loss is probably due to dissolution of highly charged fibre material such as demethylated pectins. Both the increased degree of sulphonation and carboxylation of lignin reduce the softening temperature reducing the degree of cross-linking in the lignin matrix. This softening probably improves the compressibility of the fibre pads in the sample holders of the WRV centrifuge, which would counteract the otherwise expected increase in WRV due to increased swelling potential. This phenomenon makes it difficult to see clear trends in WRV as a function of increasing degrees of sulphonation and carboxylation. When changing the counter-ion form from proton or calcium form to sodium form, there is, however, always a clear increase in WRV in the range from 20% to 30%.

  • 2.
    Hellström, Lisbeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Gregersen, Øyvind
    Department for Chemical Engineering, NTNU, Norway.
    Evaluation Of Collimated Chipping Technology For Reducing Energy Consumption In Mechanical Pulping2012In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 2, no 3, p. 6-9Article in journal (Refereed)
    Abstract [en]

    It has recently been shown that the energy efficiency during first-stage TMP (thermo-mechanical pulp) refining can be improved using amodified chipping method (collimated chipping), where the angle between the fibre direction of the wood specimen and the cutting plane is increased. This paper reports the differences in properties of TMP refined from wood chips produced at two different spout angles, 30° and 50°, with and without the addition of sodium bisulphite (NaHSO3) to the dilution water. It was found that the specific energy input for a certain CSF (Canadian Standard Freeness) value was lower for chips produced at spout 50°, but that the addition of chemicals to the dilution water had no influence on the specific energy value for a given CSF value. However, the tensile index and specific light-scattering coefficient were substantially higher for handsheets made from the pulp refined from chips produced at spout angle 50° and with NaHSO3 added compared to handsheets from pulp made from 30° and 50° chips without chemicals added.

  • 3.
    Uesaka, Tetsu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Page'S Theory Of Tensile Strength And The Stress-Strain Properties Of Paper2018In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 6, no 6, p. 13-17Article in journal (Refereed)
    Abstract [en]

    One of the most well-known theories in the area of paper is probably Page's theory of tensile strength. The article was published in Tappi Journal in 1969 [1], and written, in a very articulate way, to explain how tensile strength is determined by fibre properties and inter-fibre bond properties. Because this is the area of great interest to papermakers and pulp manufacturers, the theory has attracted great attention since then. In particular, many paper chemists were fascinated by this intuitive way of describing the relationships between bond and fibre parameters so that the theory became a theoretical foundation for many investigations of dry/wet strength agents. Interestingly, Derek himself was not completely happy with the popularity of the theory. As he noted in his paper, it is a semi-empirical theory, intended to provide a picture of the essential factors affecting tensile strength, but not as an analytical equation to predict some of the model parameters. (We will briefly touch upon Derek's concerns later.) In the late 70s, Derek and his colleague, Raj Seth, another legendary scientist from Pulp and Paper Research Institute of Canada (PAPRICAN, currently, FPlnnovations), launched investigations of the tensile stress-strain curves of paper [2,3,4]. The work depicted complex interplays among network structures, fibre properties and inter-fibre bond properties, again, in a very articulate way. This paper has also influenced a number of studies by younger researchers in the areas of paper mechanics and network mechanics. In this short article, I will try to describe how Derek tackled the problem of understanding the tensile properties of paper in the simplest and most articulate way. Based on this review, I will comment on how far we have gone from his ideas, and try to define some outstanding questions.

  • 4.
    Uesaka, Tetsu
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Gurnagul, Norayr
    FPInnovat, Pointe Claire, PQ, Canada.
    Keynote Speech By Derek Page At The 2010 Progress In Paper Physics Seminar In Montreal, Canada2018In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 6, no 6, p. 6-12Article in journal (Refereed)
    Abstract [en]

    This keynote speech was given at the "Progress in Paper Physics Seminar", which was held in Montreal, Canada in 2010. This was Derek's last speech at an international paper physics conference. The organising committee asked him to send a message to young researchers in the paper physics community. The topic of his talk was "the weakest link in chain" which gives advice that is still timely for researchers that want to make a real difference in the forest products industry. This paper is based on his speaker notes which we were fortunate to find.

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