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1.	Alfthan, Johan, et al. (author) A micromechanical model for mechanosorptive creep in paper 2002 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 28:3, s. 98-104 Journal article (peer-reviewed)abstract The creep of paper is accelerated by moisture cycling, a phenomenon known as mechanosorptive creep or accelerated creep. In this paper stress created at bonds due to anisotropic swelling during absorption and desorption of moisture, in combination with nonlinear creep, are proposed to be the cause for mechanosorptive creep. Two simplifled models are first discussed in order to demonstrate the suggested mechanism. A three-dimensional fibre network model composed of elastic fibres and inelastic bonds is then studied by finite element calculations. The relative sliding in the bonds is described by a nonlinear creep model which, in combination with anisotropic hygroexpansion of the fibres results in accelerated creep of the network.
2.	Alfthan, Johan (author) A simplified network model for mechano-sorptive creep in paper 2003 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 29:7, s. 228-234 Journal article (peer-reviewed)abstract A simplified network model for mechanosorptive creep is presented. The model resembles Cox's model for fibrous materials, but creep and the influence of bonds are included in addition to the elastic behaviour of the fibres. Three different creep laws describing the creep of individual fibres are applied in the simulations of creep of the network. Results from simulations using the model are presented. The influence of the amplitude of moisture content changes is discussed. It is shown that the model may produce macroscopic strains that are linear in stress, even though the creep of the fibres is nonlinear This may explain why both regular creep and mechanosorptive creep at small loads appear to be linear in stress.
3.	Asplund, G, et al. (author) Fibre orientation anisotropy profile over the thickness of a headbox jet 2004 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 30:8, s. 217-221 Journal article (peer-reviewed)abstract The fibre orientation anisotropy at various levels of the jet from a model headbox has been investigated. Stiff nylon fibres, 3 mm long, were added at extremely low concentrations to make it possible to observe also the centre of the jet. This meant that fibre interactions, such as floc forming, could not take place. Transparent, parallel walls enclosed the jet where fibre orientation was measured. A thin laser sheet illuminated the jet from the side and a video camera captured the light reflected perpendicularly from the fibres. Using image analysis, the orientation of the fibres was evaluated. A central vane was mounted in the headbox nozzle so the effects of the vane wake could be studied. The results show that the effect a the boundary layers, at the walls of a headbox and at the surface of a vane, was to locally reduce fibre orientation anisotropy. Depending on the vane tip shape, fibre orientation anisotropy could be additionally decreased. Overall, the fibre orientation anisotropy was weakly affected by changes inflow rate and strongly dependent on the contraction ratio in the nozzle; low speed and large contractions produced more anisotropic orientations.
4.	Axelsson, Patrik, et al. (author) Condensation reactions of lignin during birch Kraft pulping as studied by thioacidolysis 2004 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 30:12, s. 317-322 Journal article (peer-reviewed)abstract The influences of kappa number and ionic strength during birch kraft cooking on the extent of lignin condensation have been studied using thioacidolysis and size exclusion chromatography. Thioacidolysis degrades alkyl-aryl ether bonds in lignin while leaving carbon-carbon and diaryl-ether bonds relatively intact. Therefore, the lignin structures not cleaved during thioacidolysis can be considered as relatively stable and may account,, for example,for the slow residual phase delignification in the kraft cook and for differences in bleachability. It was shown that condensed lignin structures are formed in the residual lignin during birch kraft cooking. The relative amount of such structures increased with decreasing kappa number or with increasing sodium ion concentration in the cook. These structures were also found in a xylan-lignin complex isolated from a birch kraft pulp. The condensed structures were only partly reactive during oxygen delignification.
5.	Axelsson, P., et al. (author) Molecular mass distributions of lignin and lignin-carbohyd rate complexes in birch Kraft pulps : Changes caused by the conditions in the cook and their relation to unbleached pulp brightness and bleachability 2005 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31:1, s. 19-27 Journal article (peer-reviewed)abstract Lignin-carbohydrate complexes and their relationship to pulp bleachability and unbleached pulp brightness were studied in four birch kraft pulps produced at high and low hydroxide ion and sodium ion concentrations, using size-exclusion chromatography (SEC). About 75-80%of the lignin was found to be associated with carbohydrates, a larger part with hemicelluloses and a smaller part with cellulose. Easily bleached pulps, produced under high [OH-] or low [Na+] conditions, had more lignin associated with cellulose than their counterparts. Furthermore, a high [OH-] gave a residual lignin that was significantly more accessible in the residual lignin isolation, and where the inaccessible lignin was bonded to carbohydrates. Colour differences of pulps caused by variations in the cooking conditions, as studied in the SEC system, were associated with all the lignin, irrespective of whether it was associated with hemicelluloses or cellulose.
6.	Barros, Gustavo Gil, et al. (author) Mottle and Ink Distribution in Full-Tone Flexography Prints on Coated Linerboard 2007 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 33:4, s. 217-226 Journal article (peer-reviewed)
7.	Béland, M. -C, et al. (author) Optical measurement and perception of gloss quality of printed matte-coated paper 2000 In: Journal of Pulp and Paper Science (JPPS). - : Canadian Pulp & Paper Assoc, Montreal, Canada. - 0826-6220. ; 26:3, s. 120-123 Journal article (peer-reviewed)abstract A set of 32 commercially produced and printed matte-coated papers were rated for gloss quality by a panel of 13 expert judges and light-scattering distributions, gloss and gloss variation of the prints were measured. Fitting the light-scattering distributions to Von Mises distributions, we obtain a factor, kappa, related to the width of the distribution and sensitive to small changes in surface roughness. This factor relates very well with the subjective rating. Gloss variation in the 3.3 to 6.6 mm wavelength band also correlates well with the gloss quality rating. The topography of the samples was also measured using confocal microscopy and a good correlation was found between the median facet angle and the kappa values.
8.	Berg, Jan-Erik, et al. (author) A Micromechanical Model of the Deterioration of a Wood Fibre 1999 In: Journal of Pulp and Paper Science. - 0826-6220. ; 25:2, s. 66-71 Journal article (peer-reviewed)abstract A simple analytical model is presented in this paper for the prediction of the stiffness degradation and the damage state in a wood fibre, loaded in uniaxial tension or shear. The model is based on an assumed displacement field together with the minimum total potential energy theorem. For the damage development, an energy criterion is employed. The model is applied to a specific example and the relevant stiffness coefficients are calculated as a function of the damage state. The damage development as a function of the applied loads is also given. The results from a specific example considered indicate that a tensile load affects the stiffness degradation to a larger extent than does a shear load.
9.	Berg, Jan-Erik, et al. (author) Effect of Temperature on Fracture of Spruce in Compression, Investigated by Use of Acoustic Emission Monitoring 2000 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 26:8, s. 294-299 Journal article (peer-reviewed)abstract Acoustic Emission (AE) monitoring during compression of wood has been used to investigate the fracture history with specific emphasis on its dependence on temperature, moisture content, strain and loading direction. The wood was compressed in both the lateral and longitudinal directions in order to select preferred modes of deformation to achieve desired irreversible changes in the wood structure. The elastic modulus, the compressive strength and the cumulated number of AE events decreased with increasing temperature. It was concluded that the most efficient loading direction is longitudinal in order to introduce flaws in wood under compression and that a longitudinal compression of 24%, corresponding to a specific energy input of 3 kWh/ton, is needed in order to achieve substantial changes in the wood structure. The compression should be carried out at temperatures well below 120°C in order to introduce many failure sites.
10.	Bernada, P, et al. (author) Experimental study of the moisture distribution inside a pulp sheet using MRI. Part I: Principles of the MRI technique 1998 In: Journal of Pulp and Paper Science. - 0826-6220. ; 24:12, s. 373-379 Journal article (peer-reviewed)abstract Due to its real advantages in terms of spatial resolution, the MRI technique has been chosen in order to study the internal moisture in 2.5 mm thick industrial pulp samples. A spin-echo sequence with very short echo-time (TE= 2 ms) has been designed to measure moisture content inside highly hygroscopic materials and was able to detect moisture even at very low moisture content (6%). In order to enhance the spin-lattice relaxation process, and thus reduce the total scanning time of an image, the pulp samples were wetted with solutions containing contrasting agents such as copper sulphate. The optimized value of the copper sulphate concentration was finally found to be around 0.5 gL(-1). A calibration curve was utilized to transform the signal intensity into moisture content values. A slight curvature probably due to shrinkage effects appears in the calibration curve.
11.	Bernada, P, et al. (author) Experimental study of the moisture distribution inside a pulp sheet using MRI. Part II: Drying experiments 1998 In: Journal of Pulp and Paper Science. - 0826-6220. ; 24:12, s. 380-387 Journal article (peer-reviewed)abstract A spin-echo MRI sequence has been employed to measure moisture profiles during the drying of industrial never-dried pulp samples and was able to detect moisture even at very low:moisture content (6%). For the first time, moisture profiles have been measured for pulp samples approximately 2.5 mm thick with a spatial resolution of 0.15 mm under quite severe drying temperatures (up to 87 degrees C). The results highlight strong moisture gradients near the sample surfaces and no classical constant mass flux period, which leads to the conclusion that the evaporation at the surface is never fully compensated by the internal capillary flow during our drying experiments.
12.	Chinga-Carrasco, Gary, et al. (author) Structural characteristics of pore networks affecting print-through 2008 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 34:1, s. 13-22 Journal article (peer-reviewed)abstract The pore structure of handsheets and of commercial newsprints is described in detail. The advantages and limitations of scanning electron microscopy and synchrotron radiation X-ray microtomography for pore-structure assessment are discussed. This gives insight into the two-dimensional and three-dimensional characteristics of the pore structure. A major achievement is the effective quantification of the submicron pores by scanning electron microscopy. It is demonstrated that submicron pores contribute positively to light scattering per unit thickness. The relationship between the pore structure, the light scattering and print-through is explored.
13.	Dahlvik, P, et al. (author) Interactions in coating colours induced by a thermally active cellulosic polymer 1999 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 25, s. 229-234 Journal article (peer-reviewed)abstract A thermally active polymer, ethyl hydroxyethyl cellulose (EHEC), was evaluated with respect to its ability to generate temperature-induced interactions between components in coating colors. At low temperatures the polymer is water soluble, providing a good flow behavior to the color. As the temperature is raised a phase separation of the polymer takes place, inducing an interaction between the components in the color. Rheological measurements showed that using EHEC as thickener resulted in a significant temperature-induced viscosity increase of the coating color. The increase in viscosity was found to be a result of interactions taking place between the three-component system consisting of EHEC, latex and pigment. The increase in viscosity with increasing temperature was further shown to correlate with the styrene/butadiene ratio in the latex. It was also found that a higher amount of EHEC was adsorbed on English clay than on ground calcium carbonate. This affected the degree of interaction within the three-component system EHEC-latex-pigment, in that the increase in viscosity with temperature was lower when English clay was used. However, when delaminated US clay was used, a strong temperature effect was detected.
14.	Danielsson, Lars-Göran, et al. (author) UV characterization of sulphide-polysulphide solutions and its application for process monitoring in the electrochemical production of polysulphides 1996 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 22:6, s. J187-J191 Journal article (peer-reviewed)abstract The UV spectral characteristics of some sulphur species of relevance for the electrochemical production of polysulphides have been studies. It was found that an isosbestic point exists in the hydrogen sulphide ion-polysulphide solution. The absorption at this point (249 nm) is proportional to the total sulphur concentration in the solution. The investigation also shows that the spectrum of a polysulphide solution can be regarded simply as the sum of contributions from charges hydrogen sulphide ion and zero-valent sulphur in polysulphides although a complicated equilibrium distribution of different species exists in the polysulphide solution. The spectrum provides enough information for the measurement of these forms of sulphur. Based on spectrophotometric measurements, a simple monitoring for changed hydrogen sulphide ion and polysulphide excess sulphur in the process liquor can be realized.
15.	Endres, I., et al. (author) Microscale compression uniformity measurements on coated paper surfaces 2005 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31:2, s. 84-89 Journal article (peer-reviewed)abstract This paper introduces a new static sensor technique that characterizes local pressure distributions on paper surfaces tinder compression. Contact areas and local pressure variations are determined using a high-resolution pressure-sensitive film, which has been developed recently at STFI-Packforsk. Compared to other commercially available pressure-sensitive films, this new film brings the advantages of a higher spatial resolution (3 pm) and a wider pressure range (1-100 MPa), which are necessary for analyzing a microporous material such as paper. The technique provides clear images of fine details such as fibre walls, collapsed lumens and fibre crossings. In initial experiments, a measure for the load coverage ability of a coating was obtained. It gives insight into how well a coating layer covers the nonuniformity of the base paper under compression. In future, the applicability of the technique will be tested in the fields of coating, calendering and printing.
16.	Fock, Helena, 1979, et al. (author) Ultrasound Velocity profile (UVP) measurements of pulp suspension flow near the wall 2009 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 35:1, s. 26-33 Journal article (peer-reviewed)abstract An Ultrasound Velocity profiling (UVP) technique is used in this study to investigate the pipe flow of pulp suspensions in the near wall region. Four flow rates and two consistencies were investigated: 1.9 and 4.8% (w/w) consistency. The mean velocity profiles showed a distinct plug at the centre of the pipe, surrounded by a sharp velocity gradient. The plug size increased with increasing consistency or decreasing bulk velocity. The demodulated echo amplitude (DMEA) profile slowly rises from low values near the wall to a distinct maximum at the plug front before slowly decaying towards the pipe centre. Since only the fibres and fines contribute to the attenuation of ultrasound, the demodulated echo amplitude profiles thus indicate and support the hypothesis of the existence of a consistency profile in the near wall area, with a decreasing amount of fines and fibres close to the pipe wall.
17.	Forsberg, S, et al. (author) The effect of contact time between cationic polymers and furnish on retention and drainage 1994 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 20, s. J71-J76 Journal article (peer-reviewed)abstract The effect of the contact time between cationic polymers (polyacrylamides and cationic starches) and stock on retention and dewatering has been studied using a new type of equipment. Dewatering is carried out under low pressure and the addition of chemicals and other operations are controlled by a microprocessor. The retention often shows a maximum after a polymer contact time of 10-20 s. It is found that long contact times drastically reduce the effect of the added polymer. This is explained as being due to floc rupture, degradation of the polymer and poor reflocculation. The dewatering time is extremely sensitive to the polymer contact time and increases steadily with increasing contact time.
18.	Gartner, A., et al. (author) Oxidation of residual lignin with alkaline hydrogen peroxide. Part 1 : Changes in hydrophilic groups 2000 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 26:12, s. 448-454 Journal article (peer-reviewed)abstract Residual lignin was isolated from an oxygen-bleached softwood kraft pulp and subjected to oxidation with alkaline hydrogen peroxide in order to study how the degradation of the lignin is influenced by parameters such as time, temperature, addition of stabilizing agents and metal ions. The oxidized lignin samples were analyzed with respect to carboxyl and phenolic hydroxyl content. It was found that the peroxide treatment resulted in a rapid increase in the amount of carboxyl groups, presumably due to the elimination of chromophoric groups. Phenolic hydroxyl groups in the lignin required a higher temperature to be oxidized and this led to the formation of more carboxyl groups. The presence of DTPA and/or Mg (II) stabilized the hydrogen peroxide against decomposition and suppressed the degradation of phenolic groups, while the carboxyl groups remained the same. The addition of transition metal ions to the reaction system resulted in a rapid decomposition of hydrogen peroxide but also in a rapid formation of carboxyl groups and a degradation of the lignin.
19.	Gartner, A., et al. (author) Oxidation of residual lignin with alkaline hydrogen peroxide. Part II : Elimination of chromophoric groups 2001 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:7, s. 244-248 Journal article (peer-reviewed)abstract Isolated residual lignin from art oxygen-bleached kraft pulp was subjected to oxidation with alkaline hydrogen peroxide under different time and temperature conditions in both the absence and presence of stabilizing agents and transition metal ions. The resulting lignin samples were analyzed by UV/VIS and FTIR spectroscopy. The analyses demonstrate the occurrence at a temperature as low as 50 degreesC: of a rapid but limited elimination of chromophoric groups, resulting in the formation of carboxyl groups. The presence of DTPA and magnesium ions stabilizes the hydrogen peroxide towards decomposition and the chromophore elimination is improved. At a higher oxidation temperature, 80 degreesC, the effect of added stabilizer(s) is particularly pronounced. Addition of transition metal ions resulted in a rapid decomposition of hydrogen peroxide and the introduction of new chromophoric groups.
20.	Girlanda, Orlando, et al. (author) Defect Sensitivity and Strength of paperboard in Out-of-plane Tension and Shear 2005 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31:2, s. 100-104 Journal article (peer-reviewed)
21.	Girlanda, O., et al. (author) Defect sensitivity and strength of paperboard in out-of-plane tension and shear 2005 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31:2, s. 100-104 Journal article (peer-reviewed)abstract This paper considers the effects of defects in the form of cracks on the failure properties in the thickness direction of multilayered board. The objective was to study how the peak stress value changes with various crack lengths under various load conditions. Specimens with manufactured cracks cut parallel to the machine-direction-cross-machine-direction plane were glued in the Arcan device and tested under pure tensile stress and mixed shear-tensile stress. The lower peak out-of-plane tensile stress measured in damaged samples indicates a defect sensitivity in multilayered board. The results for one type of board show that the loss in tensile strength is independent of the crack length. On the other hand, mixed shear and tensile stress behaviour does not appear to be influenced by the presence of cracks.
22.	Gourdon, Mathias, 1980, et al. (author) Sodium Salt Scaling in Black Liquor Evaporators - Pilot Plant Results and Industrial Significance 2011 In: Journal of Pulp and Paper Science. - 0826-6220. ; 36:3-4, s. 98-106 Journal article (peer-reviewed)abstract In industrial black liquor evaporation plants, large amounts of sodium crystals are produced every day which all have the potential to scale the evaporator surfaces. In this project, research on the crystallization during evaporation of softwood black liquor has been performed. The results are based on measurements in a research black liquor evaporator The distribution of scale vertically along the heat transfer surface has been investigated, as well as the influence of different operating conditions, such as the circulating flow rate of black liquor (between 0.2 and 3.7 kg/m.s), the residence time for the black liquor in the evaporator (between 76 and 226 s), and the temperature difference between the liquor and the heating steam (between 11 and 26 degrees C). The sodium scale formed during evaporation is mainly in the form of double salts of sodium carbonate and sodium sulfate. The ratio between the two salts is one important parameter affecting the crystallization and scaling. The effect of the carbonate-to-sulfate ratio has been investigated for aqueous sodium carbonate - sodium sulfate solutions. In this paper, the results of these investigations are presented and a number of industrial significances are illustrated.
23.	Gradin, Per A., et al. (author) Measurement of the Power Distribution in a Single Disc Refiner 1999 In: Journal of Pulp and Paper Science. - 0826-6220. ; 25:11, s. 384-387 Journal article (peer-reviewed)abstract A vital parameter in the production of mechanical pulp through refining is the energy consumption. Until recently, the pulping industry has focused on the total energy consumed, without a full understanding of how this energy is distributed in the refiners. In this paper two methods are suggested by which it is possible to estimate the energy supplied at an arbitrary point along the disc radius on refiner segments. The methods are based on instrumented bar with strain gauges. In the first method, a bar is slotted so that the sensor can be viewed as consisting of a number of cantilever beams separated by slots. In the second method, the sensor consists of one continuous bar along the disc radius. The sensors are calibrated such that influence coefficients are obtained for the slotted case and an influence function is obtained for the continuous one. The tangential forces are obtained directly in the first method, while in the second they are given by an integral equation which can be solved numerically. From the knowledge of the tangential force the power distribution can be calculated. Experimental results from the use of the slotted sensor are also given.
24.	Gradin, PA, et al. (author) Measurement of the power distribution in a single-disc refiner 1999 In: JOURNAL OF PULP AND PAPER SCIENCE. - 0826-6220. ; 25:11, s. 384-387 Journal article (other academic/artistic)
25.	Granberg, H., et al. (author) Influence of surface-induced nonuniform reflectance on the diffuse reflectance factor. Part I : Model predictions 2003 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 29:8, s. 247-253 Journal article (peer-reviewed)abstract The Kubelka Munk (KM) model is used frequently as a tool to design paper to reach a desired opacity and whiteness. The input data in this modelling, the scattering and absorption coefficients, are commonly derived from diffuse reflectance factor measurements. The quality of the coefficient values is dependent on the structure of the samples and the backings from which they were obtained. In this paper we focus on modelling the influence of nonflectance factors obtained using the d/0degrees standardized uniform reflectance induced by the surface structure, and how it affects the diffuse reflectants factors obtained using the d/0degrees standardized measurement geometry. From the analysis, we conclude that the structure of the surface facing the detector may have a significant effect on the instrument readings depending on whether the sample is glossy or reflects diffusely from the surface. Based on this surface reflectance, we analyze various situations of relevance for the papermaker and show that common-practice application of the KM model to reflectance factor measurements may lead to serious misinterpretations.
26.	Granberg, H., et al. (author) Influence of surface-inducled nonuniform reflectance on the diffuse reflectance factor. Part II : Experimental verification on coated substrates 2003 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 29:8, s. 254-259 Journal article (peer-reviewed)abstract Many authors have found that the Kubelka-Munk (KM) scattering coefficient, s(c), of a coating applied to a substrate decreases with increasing coat weight. This decrease is usually explained by a structural/porosity change with coating thickness or a penetration of the coating into the paper In this paper we propose an alternative explanation to the observed decrease in sc, namely the misinterpreted diffuse reflectance factors for non-Lambertian reflecting substrates and coatings. This explanation was recently proposed by the authors; the second part presented here provides experimental support for the presence of a nonuniform reflectance distribution and its influence on KM fitted data. Three different coated systems are considered, using a transparent film, abase paper and a synteape film as substrate. The effect of the surface reflectance of the substrate and of the coated substrate can explain the apparent decrease in sc as an artifact when measuring a sample with an instrument having a d/0degrees geometry.
27.	Granberg, H, et al. (author) Quantification of the intrinsic error of the kubelka–munk model caused by strong light absorption 2003 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 29:11, s. 386-390 Journal article (peer-reviewed)abstract The Kubelka-Munk (KM) model is widely used within the paper industry to interpret diffuse reflectance factor measurements of paper and its components. It has been found in the literature that the addition of a dye colorant to a paper sheet not only increases its KM light absorption coefficient, but for strong absorption also decreases its KM light scattering coefficient. This effect has previously been attributed to the intrinsic error of the KM model induced by light absorption that tends to orient of the light fluxes perpendicular to the sheet. In the present work we have mapped the intrinsic error of the KM model by comparing light scattering calculations from the KM model with the more accurate Discrete Ordinate Radiative Transfer model DORT2002. We found that the models agree within 2.3% in reflectance, and that the intrinsic error in the KM model explains about 1/5 of the previously observed interdependence of the KM coefficients for heavily dyed sheets.
28.	Grön, J, et al. (author) Effect of coating chemistry and temperature on runnability and coated paper properties 1997 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 23, s. J422-J427 Journal article (peer-reviewed)abstract The ionic nature of the components in coating colors is of great importance for the presence or absence of interparticle interactions, which in turn largely govern coating rheology, machine runnability and final paper properties. In the present study two types of starch have been evaluated with repect to their effect on these properties. The aim was to generate different association conditions in coating colors by using anionic or cationized starch, which show clear differences what comes to interaction with anionic clay pigment. Another objective with the study was to evaluate the influence of temperature on the pigment suspensions. Rheological and dewatering measurements were performed and correlated to results from pilot scale coating. It was found that the anionic starch caused a stabilization effect originating from the repulsive forces created between the starch and the equally anionic clay pigment. This colloidally stable system caused no problems in the levelling of coating on the paper, but resulted in a relatively dense coating layer. Starch with substituted cationic groups showed a strong electrostatic interaction with the clay pigment resulting in an aggregated coating system and deteriorated runnability. This was reflected in the final coating as blade streaks due to build-up of coating deposits on the blade during levelling. However, the aggregated coating system resulted in a structured coating layer with a high porosity, which may be desired when printing the coated paper. An increased temperature had a marked effect on the aggregated coating color in terms of a significant decrease in viscosity, while the temperature had a more limited effect on the stable system containing anionic starch. This behavior was also seen in the properties of the dry coated layers, where the open structure of the aggregated color was more affected by a higher temperature than the stable color.
29.	Gurnagul, Norayr, et al. (author) THE MECHANICAL PERMANENCE OF PAPER - A LITERATURE-REVIEW 1993 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 19:4, s. J160-J166 Journal article (peer-reviewed)
30.	Gustafsson, Roland, et al. (author) Polysulphide pretreatment of softwood for increased delignification and higher pulp viscosity 2004 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 30:5, s. 129-135 Journal article (peer-reviewed)abstract The effect of polysulphide pretreatment under various conditions prior to a kraft cook was investigated for spruce (Picea abies) chips using a technique with a liquor:wood ratio of 67:1 to keep the liquor composition as constant as possible during the pretreatment and cooking phases. If the polysulphidepretreatment is carried out at a very high hydroxide concentration, 1.5 mol OH-/L, three independent positive effects (compared with a corresponding sulphide pretreatment without polysulphide) can be observed: more extensive delignification; higher pulp, viscosity; and higher carbohydrate yield. When the alkali change was changed in the subsequent kraft cook (in the range 0.15-0.60 mol/L), the increase in delignification extent as a result of polysulphide pretreatment was not affected but the relative carbohydrate yield increase was favoured by a higher alkali charge during cooking. On the other hand, the absolute carbohydrate yield is favoured by a intermediate alkali charge.
31.	Heyden, Susanne, et al. (author) Simulation of Fracture in a Cellulose Fibre Network 1998 In: Journal of Pulp and Paper Science. - 0826-6220. ; 24:5, s. 160-165 Journal article (peer-reviewed)abstract A network model has been formulated and used for computer simulations of the geometry an mechanical behaviour of cellulose fibre networks. The focus is on the properties needed to proceed with a continuum analysis of fracture, that is stiffness, strength and fracture energy. It is found that the ductility of inter-fibre bonds has a strong effect on the fracture properties. Localization of the fracture zone is also studied. The dependence of elastic stiffness on various micro-level parameters is simulated, and examples are given of Young's modulus dependence on fibre curl and fibre orientation distribution.
32.	Johansson, B, et al. (author) The mechanism of offset ink particles agglomeration in a calcium - fatty acid collector system 1996 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 22, s. J381-J385 Journal article (peer-reviewed)abstract Model studies on a dried ink particle suspension without fibres show that the kinetics of the ink agglomeration are totally dependant on the soap particle precipitation and formation. The calcium soap has to precipitate before the ink and soap particles can agglomerate. Calcium ions have two important effects on ink agglomeration: the precipitation of soap and the reduction of the surface potential on the ink particle surface. The importance of free fatty acid anions adsorbed onto the ink particle surface is negligible, since the fatty acid is almost completely precipitated as calcium soap.
33.	Johansson, Erik, et al. (author) Aspects on the chemistry of cellulose degradation and the effect of ethylene glucol duringozone delignification of kraft pulps 2000 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. Journal article (other academic/artistic)
34.	Johansson, E. E., et al. (author) Aspects of the chemistry of cellulose degradation and the effect of ethylene glycol during ozone delignification of kraft pulps 2000 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 26:7, s. 239-244 Journal article (peer-reviewed)abstract The viscosities of oxygen-predelignified kraft pulps were measured as they were ozonated at high consistency. The degree of degradation of thc cellulose was calculated from the viscosities as direct (ds) and indirect, alkali-induced, scissions (als) in the polymer: Als was derived using the decrease in the observed degradation when a borohydride reduction preceded the alkaline extraction of the ozonated pulps. The mechanism of these Scissions is discussed in terms of free-radical reactions and their relative significance. A given charge of ozone to a lignin-containing or lignin-free pulp produced similar degrees of carbohydrate degradation, indicating that the degradation does not depend greatly on the presence of the lignin in the pulp. Ethylene glycol (EG) increases the selectivity during ozone delignification much more than methanol. This effect is optimal at pH3 and 25 wt% EG in the reaction system. The increased selectivity may have several possible reasons. one is the limited extent of free-radical reactions (e.g. hydroxyl radicals) occurring in the carbohydrate chain.
35.	Karlsson, Olov, et al. (author) Evidence for chemical bonds between lignin and cellulose in kraft pulps 1996 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 22:10, s. J397-401 Journal article (peer-reviewed)abstract The cellulose solvent system LiCl-dimethylacetamide has been used to dissolve kraft pulps prepared from pine and birch. The dissolved polymers were analyzed using size-exclusion chromatography combined with both RI- and UV-detection systems in order to monitor simultaneously the major wood polymers (cellulose, hemicellulose and lignin). Kraft pulps from birch were completely soluble in the solvent system and the pine kraft pulp about 80% soluble. Analyses of the kraft pulps strongly suggest that a considerable amount of the residual lignin is chemically linked to the high molecular weight cellulose in pine but not in birch. The presence of stable lignin-cellulose bonds will reduce the possibility of achieving a low kappa number by cooking. For comparison, sulphite and bisulphite pulps were also examined. Both pulps were soluble in the solvent system and analyses indicated that lignin-cellulose bonds also exist in these pulps although to a significantly lesser extent than in the pine kraft pulp
36.	Karlsson, Olov, et al. (author) Linkages between residual lignin and carbohydrates in bisulphite (magnefite) pulps 2001 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:9, s. 310-316 Journal article (peer-reviewed)abstract The presence of bonds between residual lignin and carbohydrates in bisulphite pulps from hardwoods and softwoods was studied. Results showed that a fraction of the residual lignin was bonded to cellulose in bisulphite pulps of softwood. The treatment with xylanase indicated the existence of alkali-stable lignin-xylan bonds in softwood bisulphite pulps.
37.	Karlsson, Olov, et al. (author) The use of cellulases and hemicellulases to study lignin-cellulose as well as lignin-hemicellulose bonds in kraft pulps 2001 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:6, s. 196-201 Journal article (peer-reviewed)abstract The combination of carbohydrate-degrading enzymes and size-exclusion chromatography (SEC) has been used to analyze the existence of covalent bonds between lignin and cellulose and/or hemicelluloses in pulps. Cellulases and xylanase were used for degradation of cellulose and xylan, respectively. Analysis of the molecular weight profiles of lignin and carbohydrates before and after enzymic hydrolysis were performed by dissolution of the pulps in LiCl/dimethylacetamide (DMAC). The results indicate that a considerable part of the residual lignin in unbleached pine kraft pulp is bond to cellulose. Bonding of lignin to xylan in the pine kraft pulp could also be detected. Analysis of birch kraft pulp shows that most of the residu lignin in birch kraft pulps is covalently linked to xylan. The combination of carbohydrate-degrading enzymes and SEC in LiCl/DMAC seems to be an excellent way of characterizing bonds between lignin and carbohydrates in chemical pulps.
38.	Klinga, Niklas, et al. (author) Energy efficient high quality CTMP for paperboard 2008 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 34:2, s. 98-106 Journal article (peer-reviewed)abstract This paper discusses the relationship between bulk and internal bond strength in paper sheets and their dependency on fibre length, fibre flexibility and fibre surface properties. It also discusses an interesting process concept for manufacturing of energy efficient high quality CTMP for paperboard. Post-refining pilot trials of spruce HTCTMP with an initial freeness of 740 ml were carried out at Metso Paper R&D in Sundsvall, Sweden. Both gentle high consistency and severe low consistency post-refining were performed. High consistency post-refining, at high energy input, gave freeness levels below 70 ml and still preserved the fibre length. These fibres were characterised by a very high flexibility giving sheets with a tensile index as high as 64 kNm/kg. Long fibres can however cause formation problems on a board machine which in turn can lead to poor surface properties, hence shorter fibres are from that perspective desirable. The low consistency post-refining resulted in a rapid drop in freeness due to fibre cutting. This was achieved at an extremely low specific energy input, which probably preserved most of the original fibre stiffness. In spite of this low energy input it was possible to reach the same Z-strength at a given bulk, as for the high consistency post-refined pulp. This implied that high bulk at certain internal bond strength could be achieved with stiff fibres even though the content of long fibres was low. Energy efficient low consistency post-refining of spruce HTCTMP yields high quality pulp at a total energy input of ~800 kWh/admt and is an interesting process concept for production of pulps intended for paperboard.
39.	Ko, Jordan, et al. (author) Simulating single-phase swirling flows in hydrocyclones 2007 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 33:3, s. 133-137 Journal article (peer-reviewed)abstract This study aims to develop a numerical methodology for modelling single-phase hydrocyclone flows without employing empirical model modifications. Its final application to the design of novel hydrocyclones requires it to be accurate for diverse geometries and operating conditions. Different solution methods offering increasing degrees of solution accuracy and requiring different lengths of simulation time were developed. When used together appropriately, these methods provide timely and valuable information suitable for various stages qf the hydrocyclone design cycle.
40.	Koivu, Viivi, et al. (author) Combining X-ray micro-tomography and image analysis to study imbibition and void space in liquid packaging board 2010 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 36:3-4, s. 170-177 Journal article (peer-reviewed)abstract Methods combining micro scale resolution x-ray shadow graphs, computerised x-ray micro-tomography and advanced image analysis were developed to study connections between the structure of void space and raw edge imbibition in liquid packaging board. Imbibition roughening was analyzed from 2D shadow graphs by a dynamic interface recognition algorithm. An idea of investigating flow paths in cardboard samples using potassium iodine in water solution as contrast enhancement substance was introduced. For demonstrating the potential of the tomographic methods, numerical lattice Boltzmann permeability simulations were performed. Experimental measurements were conducted to compare and support the results extracted from tomographic data. A 3D void space segmentation algorithm was utilized to analyze structure of void space in tomographic reconstructions. Tentative results indicate that the new methods can be used to find correlation between pore size heterogeneity and imbibition roughening. Finally, water absorption coefficients of the test samples were calculated utilizing results extracted from the void space segmentation analysis.
41.	Kugge, C (author) An AFM study of local film formation of latex in paper coatings 2004 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 30, s. 105-111 Journal article (peer-reviewed)abstract The local film formation of latex in model paper coating suspensions of low latex to CaCO3 volume fraction ratio, 0.27, has been studied using both topographic and phase images of atomic force microscopy. Local film formation is believed to work concurrently with latex migration. Both the dosage and molecular weight of carboxymethylcellulose (CMC) have a visible effect on latex film formation. A greater dosage of CMC retards latex migration and a higher molecular weight of CMC prolongs the film-formation process. Another thickener, ethyl(hydmxyethyl)cellulose (EHEC), was compared to CMC, and EHEC creates a composite where deformed latex particles are encapsulated in EHEC. A higher Tg latex increases the amount of latex in the upper region of the coating. It is suggested that a lower Tg latex halts migration, which leads to film formation at an earlier stage, further down in an evaporating pore
42.	Kugge, C, et al. (author) Pressure filtration of cellulose fibres 2005 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31, s. 95-100 Journal article (peer-reviewed)abstract The compressional rheology of cellulose fibre suspensions has been studied using a pressure filtration technique. The dewatering of these systems is thus described in terms of various key properties of the suspension, including the compressive yield stress, permeability and solids diffusivity, permitting a quantitative characterisation of the consolidation process. We investigate as a particular example the effect of a commercial debonding agent additive on the compressional properties of a fibre suspension. Such agents are commonly used in the production of hygiene products where they are added to decrease the strength of fibre-fibre bonds. Here we investigate their effect on the compressive response of fibre suspensions as an example of how measurements of this type can be used to characterise the effect of additives on bulk properties. The results indicate that addition of debonder causes a somewhat higher dewatering tendency as the solids level is increased.
43.	Land, Cecilia, 1979-, et al. (author) Moisture streaks and their relation to baggy paper webs 2008 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 34:4, s. 234-239 Journal article (peer-reviewed)abstract Significant and controlled wet streaks were imparted to laboratory-made kraft paper sheets having an initial moisture content of 50 %. The sheets were then dried under a specified strain according to different drying strategies. Both the wet streaks and the drying strain were applied in the CD in order to amplify the observed effects. The bagginess of the paper sheet, or the length profile, was measured after drying and relaxation. Moisture streaks remaining after unloading resulted in short streaks in the paper. Drying of the paper beyond moisture equilibrium also led to an uneven paper length, particularly when the paper was allowed to shrink during drying. No correlation was found between the tensile stiffness profile and the permanent length profile.
44.	Li, Jiebing, et al. (author) Rapid and direct pulp kappa number determination using spectrophotometry - Comments 2001 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:4, s. 111-111 Journal article (peer-reviewed)
45.	Li, Jiebing, et al. (author) The relationship between kappa number and oxidizable structures in bleached kraft pulps 2002 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 28:8, s. 262-266 Journal article (peer-reviewed)abstract The relationship between residual oxidized lignin structures in spruce and birch kraft pulps and their kappa number contribution after each stage in an ODEQP (spruce) and an OQ(OP)Q(PO) (birch) sequence, respectively, has been investigated. Analysis by a modified kappa number method (OxDem kappa number) as well as by determination of permanganate oxidation equivalents on various isolated residual lignin samples revealed that the relationship between the lignin content and kappa number gradually changes as the bleaching sequence proceeds, giving values that differ substantially from that found in unbleached kraft pulp. These effects can be attributed to the successive oxidative fragmentation of aromatic rings and the formation of carboxyl and non-aromatic unsaturated structures in the residual lignin structure. Therefore, a kappa number determination on pulp which has been subjected to an oxidative stage will result in an underestimation of the lignin content.
46.	Lif, J.O., et al. (author) Characterizing the in-plane hygroexpansivity of paper by electronic speckle photography 1995 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 21:9, s. J302-J308 Journal article (peer-reviewed)abstract A newly developed electronic speckle photographic system is used to investigate the hygroexpansion of paper. By using a spray-paint technique for the creation of the speckle pattern, two applications of the system are demonstrated on different machine-made papers. The first one is the determination of the displacement field after the exposure of a sheet to a moisture change. The second is the determination of hygroexpansion orientation. Lastly, an investigation of the correspondence between hygroexpansion and tensile stiffness orientations determined by an ultrasonic technique is presented.
47.	Lindgren, C. T., et al. (author) The kinetics of residual delignification and factors affecting the amount of residual lignin during kraft pulping 1996 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 22:8, s. J290-J295 Journal article (peer-reviewed)abstract Kraft pulping of softwood can be divided into three phases: the initial, the bulk and the residual delignification phases. The rate of delignification in the residual phase and the amount of lignin to be removed in this slow phase have been studied as a function of the conditions in the kraft cooking of Norwegian spruce chips, Picea abies. The variables studied were concentration of OH-, concentration of HS-, ionic strength and temperature. The amount of lignin remaining undissolved in the wood residue at the transition from bulk to residual delignification is decreased by increasing the concentration of OH- and by increasing the concentration of HS- in the bulk phase. The amount of residual lignin is also decreased by a lower ionic strength in the bulk phase. The temperature in the range of 150 to 180 degrees C affected the lignin content at the transition from bulk to residual delignification but not the amount of residual lignin extrapolated to the beginning of the cook. Only the hydroxide ion concentration and the temperature seem to have an influence on the rate of delignification in the residual phase. The rate of delignification in the residual phase is well described by the following equation: dL(r)/dt = (0.0032 + 0.0020 . [OH-]) (. e) -146 000/8.314 . (1/T - 1/443.15)(Lr).
48.	Mattsson, Rosa, et al. (author) Influence of abietic acid, betulinol, sodium oleate and tripalmitine on the migration of akd in paper 2003 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 29:8, s. 281- Journal article (peer-reviewed)abstract The migration of alkylketene dimer (AKD) wax through untreated paper and through paper sheets impregnated with extractives was investigated at temperatures above themelting point of the wax. The migration was studied at 80and 105°C by using various combinations of untreated paper sheets, paper sheets impregnated with AKD and sheets impregnated with extractives. The migration was observed by measuring contact angles with distilled water. There is no indication that extractives such as betulinol, oleate or tripalmitine interfere with the migration of AKD. The diffusion coefficient for AKD in paper was estimated to be of the order of 10–11 m2/s at the temperatures investigated.
49.	Nilsson, L, et al. (author) Measuring moisture gradients in cellulose fibre networks: An application of the magnetic resonance imaging method 1996 In: Journal of Pulp and Paper Science. - 0826-6220. ; 22:2, s. 48-52 Journal article (peer-reviewed)abstract A magnetic resonance imaging method was employed to measure moisture distributions in pulp samples. A calibration experiment shows that, in the range of moisture contents up to 1.4 g water/g dry substance, the MRI signal is linearly proportional to the mass of moisture of the pulp sample. The in-situ drying of a pulp sheet approximately 4 mm thick was them studied. The resolution in the thickness direction was 0.39 mm. It was found that, even at the very low drying rates employed in the present study (the average drying rate was 0.3 kg/m(2)/h), a gradient in moisture developed across the sheet as drying progressed.
50.	Nohlgren, Ingrid, et al. (author) Black liquor gasification with direct causticization using titanates in a pressurized entrained-flow reactor : Part II: carbon and carbon species transitions 2003 In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 29:10, s. 348-355 Journal article (peer-reviewed)abstract Experiments on black liquor conversion in the presence of sodium titanates were carried out in a pressurized entrained-flow reactor, at temperatures of 900, 950 and 1000°C, at pressures of 0.5 and 1 MPa and in atmospheres of pure nitrogen (N2) or N2 with 2% carbon dioxide (CO2). Up to 80-90% conversion of the carbon in black liquor to gases was obtained within 5 s at these conditions. This is a very promising result for industrial scale gasifiers. Char carbon was gasified two to four times faster in N2 with 2% CO2 than in N2 alone. Overall, carbon conversion increased with increasing temperature, but the gasification rate decreased with increasing temperature. CO was found to be the main carbon-containing gas formed.

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