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Contents
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Volume 23, 2008, Issue No. 3
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Turbulence models for falling film hydrodynamics and heat transfer compared with
experimental values for black liquor
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Miriam Johansson and Lennart Vamling, Chalmers University of Technology, Gothenburg, Sweden, Lars Olausson, Metso Power AB, Gothenburg, Sweden
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Abstract:
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Increased knowledge about the hydrodynamics and the heat transfer in falling film evaporation of black liquor is an important support for design of energy and cost-effective evaporation plants. Turbulence models of falling film hydrodynamics
were compared with experimental results gained in this study.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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256-263
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p256-263
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Keywords:
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Black liquor, Eddy viscosity, Evaporation, Falling film, Heat transfer, Mass transfer
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Simulation of triaxial deformation of wet fiber networks
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Pasi P.J. Miettinen and Jukka A. Ketoja, KCL Science and Consulting, Espoo, Finland
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Abstract:
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Numerical studies of very wet and weak fiber networks showed that the lateral Poisson''''s ratio depends not only on the applied strain, but also on the length of the specimen. The thickness changes are sensitive to fiber stiffness.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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264-271
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p264-271
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Keywords:
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Network deformation, Poisson ratio, Simulation, Wet webs
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Oxygen permeability of polyethylene-extrusion-coated greaseproof paper
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Henrik Kjellgren, Nordic Paper Seffle AB, Säffle, Sweden, Lennart Stolpe and Gunnar Engström, Karlstad University, Karlstad, Sweden
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Abstract:
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Polyethylene-extrusion-coated greaseproof paper exhibited significantly lower oxygen permeability than predicted from the oxygen permeability of polyethylene and greaseproof paper itself. Two mechanisms proposed for the superior oxygen
permeability of polyethylene-extrusion-coated greaseproof paper were compared.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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272-276
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p272-276
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Keywords:
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Barrier properties, Extrusion coating, Greaseproof papers, Oxygen permeability, Paper properties, Polyethylene
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Influence of ink components on print rub
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Hanna Koivula, Åbo Akademi University, Åbo /Turku, Finland, Patrick Gane, Omya Development AG, Switzerland and Helsinki University of Technology, Espoo Finland, Martti Toivakka, Åbo Akademi University, Åbo /Turku, Finland
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Abstract:
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The influence of the ink formulation components on the degree of print rub was studied for a series of model inks. Ink-coating interactions and print rub were probed with the Ink Surface Interaction Tester and Prüfbau Quartant. Additionally, print quality, gloss and ink density were evaluated.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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277-284
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p277-284
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Keywords:
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Ink components, Matte coated papers, Print rub, Tack
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The influence of charge density and molecular weight of cationic poly(vinyl alcohol) on
paper properties
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Pedram Fatehi and Huining Xiao, University of New Brunswick, Canada
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Abstract:
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The influence of the charge density and molecular weight of cationically-modified poly(vinyl alcohol) on the properties of fibers and papers, including mechanical/optical properties of papers and the freeness of fibers, were systematically
investigated in this work.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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285-291
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p285-291
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Keywords:
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AFM, C-PVA, Fiber strength, Internal bonding, Light-scattering coefficient, Paper brightness, Tear strength, Tensile strength
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Carbohydrate degradation during softwood kraft cooking – influence on cellulose viscosity, carbohydrate composition and hexenuronic acid content
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Dan Johansson and Ulf Germgård, Karlstad University, Karlstad, Sweden
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Abstract:
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A kinetic model, including the variables temperature as well as hydroxide ion, sulphide ion and sodium ion concentrations, was fitted to laboratory data from kraft cooking of industrial Norway spruce chips. The model described well the data for carbohydrates, for hexenuronic acids and for the intrinsic viscosity.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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292-298
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p292-298
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Keywords:
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Carbohydrates, Cellulose, Glucomannans, Kraft cooking, Softwood, Xylans
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The use of microfibrillated cellulose produced from kraft pulp as strength enhancer in TMP paper
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Øyvind Eriksen, Norwegian University of Science and Technology, Trondheim, Norway, Kristin Syverud, Paper and Fibre Research Institute, Trondheim, Norway, Øyvind Gregersen, Norwegian University of Science and Technology, Trondheim, Norway
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Abstract:
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The effect of adding microfibrillated cellulose (MFC, hydrodynamic particle sizes in the range 30-150 μm) on the physical properties of TMP handsheets was investigated. Addition of 4% MFC increased the tensile index and air resistance and reduced the light scattering coefficient, opacity and brightness of the sheets. The use of MFC as strength enhancer in commercially produced paper is discussed.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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299-304
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p299-304
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Keywords:
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Grinding, Homogenization, Microfibrillated cellulose, Paper strength
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Economic perspectives on quality control in TMP refining processes
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David Sikter, Holmen Paper, Norrköping, Sweden, Anders Karlström, Chalmers University of Technology, Gothenburg, Sweden, Christer Sandberg, Holmen Paper, Norrköping, Sweden, Per Engstrand, Mid Sweden University, Sundsvall, Sweden
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Abstract:
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Possible methods and models for quantifying the economic value of improved quality control in the refining stage were explored. The effects considered were production increase, energy efficiency, reduction of web break frequency, and quality window optimization.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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305-314
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p305-314
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Keywords:
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Economy, Production increase, Quality optimization, Refiner control, Web breaks
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Theoretical outline of the cause for observed cavitation in a low-consistency refiner
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Oddbjørn Eriksen, Paper and Fibre Research Institute, Trondheim Norway, Claes Holmqvist and Ulla-Britt Mohlin, STFI-Packforsk AB, Stockholm, Sweden
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Abstract:
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High-frequency pressure measurements in the refining zone strongly indicated that cavitation occurs regularly in lowconsistency refiners. A mechanism of fibre trapping that can yield gap pressures several hundred kPa below that in the
grooves is suggested. Cavitation bubbles may then form, which subsequently collapse and cause shock waves when the pressure rises after the bar passage.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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315-320
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p315-320
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Keywords:
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Cavitation, Fibre-optic pressure sensor, Low-Consistency, Refining zone
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Fibre floc drainage – a possible cause for substantial pressure peaks in low-consistency refiners
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Oddbjørn Eriksen, Paper and Fibre Research Institute, Trondheim, Norway, Claes Holmqvist and Ulla-Britt Mohlin, STFI-Packforsk AB, Stockholm, Sweden
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Abstract:
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The pressure in the refiner gap during bar crossings was measured. Pressure peaks reaching magnitudes as high as several
MPa were detected. A hydrodynamic explanation is provided that is based on the assumption that a floc is trapped between
the bars and subsequently dewatered.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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321-326
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p321-326
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Keywords:
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Disc refiners, Drainage resistance, Fibre-optic pressure sensor, Low-Consistency, Refining zone
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The influence of fine kaolin and ground calcium carbonates on the efficiency and
distribution of fluorescence whitening agents (FWA) in paper coating
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Deqiang Ma and R. Douglas Carter, KaMin LLC, Macon, USA, David Haefner and Aristide Dogariu, University of Central Florida, Orlando, USA
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Abstract:
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The efficiency and distribution of FWA in top coats of double-coated paper from a high speed pilot coating, consisting of fine kaolin blends with broad and narrow particle size distribution (BRD and NRW) ground calcium carbonates (GCC) were studied. UV microscopy showed that increasing the fine kaolin level at the expense of NRW GCC made FWA concentrate more towards the surfaces. Fine kaolin improved FWA efficiency by attenuating forward scattering and exposing FWA to backscattered UV light near the surface.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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327-332
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p327-332
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Keywords:
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Brightness, CIE whiteness, Coating structure, FWA, Microscopy, Scattering
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Gibbs energy of imbibition of non-polar and polar solutions into calcium carbonate and kaolin coatings
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Deqiang Ma and R. Douglas Carter, KaMin LLC, Macon, USA, Janne Laine and Per Stenius, Helsinki University of Technology, Espoo, Finland
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Abstract:
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The Gibbs’ energy of imbibition of ink, DG can basically be treated as a product of coating structure variables (volume and diameter, SVi /Di) and surface energy parameters (g cosq ), i.e. DG highlights the interactive properties of the coating
pore surface and the probe liquid. This is illustrated by experimental data for top coats consisting of blends of kaolin and calcium carbonate on double-coated papers
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Volume 23, 2008, Issue No. 3
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Pages:
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333-338
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p333-338
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Keywords:
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Coating, Gibbs free energy, Pore structure, Surface energy
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A method for experimental investigation of the wood chipping process
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Lisbeth M. Hellström, Per A. Gradin and Torbjörn Carlberg, Mid Sweden University, Sundsvall, Sweden
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Abstract:
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An experimental setup was developed in which chipping can be performed under very well defined conditions, i.e. the rate of indentation of the chipping tool can be controlled, the force on the tool can be measured and the angle of the wood specimen with respect to the cutting plane can be varied in both a horizontal and a vertical plane.
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Issue:
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Volume 23, 2008, Issue No. 3
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Pages:
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339-342
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Online Date:
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September 29, 2008
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DOI:
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10.3183/NPPRJ-2008-23-03-p339-342
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Keywords:
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Digital Speckle Photography, Fracture processes, Friction, Wood chipping
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