Dissertations / Theses on the topic 'Paper fiber'

Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Yulin Deng; Committee Member: Jeffery S. Hsieh; Committee Member: Sujit Banerjee; Committee Member: Zhong Lin Wang.

L'optimisation de nombreux procédés technologiques requiert une compréhension approfondie des phénomènes de frottement des papiers. Nous avons donc cherché à mieux comprendre ces phénomènes pour tenter d'améliorer la séparation des enveloppes dans les machines à affranchir. Les méthodes normalisées de mesure du frottement papier-papier se sont tout d'abord avérées limitées en termes de répétabilité et de conditions expérimentales. Nous avons donc développé deux méthodes de mesure, l'une à faible et l'autre à haute vitesses. Nous avons aussi adapté la mesure du frottement aux différents contacts papier rencontrés dans les machines à affranchir. Dans un second temps, nous avons utilisé ces méthodes pour étudier les mécanismes responsables du frottement avec le matériau papier. Nous avons notamment étudié (i) la dépendance du frottement papier-papier à la direction et longueur du déplacement, (ii) l'influence de la température et de l'humidité sur le frottement papier-papier et (iii) les principales caractéristiques frictionnelles des contacts enveloppe-enveloppe, papier-rouleau et papier-patin. Dans un troisième temps, nous avons développé un modèle complet de la séparation des enveloppes dans une machine à affranchir. Cette séparation vise à déplacer, sans l'abimer, l'enveloppe inférieure d'une pile – et uniquement cette enveloppe. Le modèle a permis d'identifier, de caractériser et de proposer une optimisation des principaux paramètres de ce procédé
The improvement of numerous technological processes requires a deep understanding of the paper friction phenomena. Thus, we tried to obtain a better understanding of those phenomena to improve the envelopes separation in franking machines. The standad methods for measuring the paper-on-paper friction force appeared to be limited in terms of repeatability and experimental conditions. Thus, we developed two experimental methods, at low and high speeds, respectively. We also adapted the friction measurement methods to the different contacts found in franking machines. We then used those methods to study the mechanisms responsible for the friction with the paper materials. In particular, we studied (i) the dependency of the paper-on-paper friction to the direction and length of the displacement, (ii) the influence of temperature and humidity on the paper-on-paper friction, and (iii) the main frictional properties of the envelope-on-envelope, rollers-on-paper, and pads-on-paper contacts, respectively. To finish with, we developed a model of the envelopes separation inside a franking machine. This process aims at displacing - with no damage - the bottommost envelope of a stack - and only this envelope. The model allowed us to identify, to characterize, and to propose an optimization of the main process parameters

The structure of a material is of special significance to its properties, and material structure has been an active area of research. In order to analyze the structure based on digital microcopy images of the material, noise reduction and binarization of these images are necessary. Measurements on fiber networks, found in paper and wood fiber - reinforced composites, require a segmentation of the imaged material sample into individual fibers. The acquisition process for modern X-ray absorption mode micro-tomographic images is described. An improved method for the binarization of paper and fiber-reinforced composite volumes is suggested. State of the art techniques for individual fiber segmentation are examined and an improved method is suggested. Software tools for the mentioned image processing tasks have been created and made available to the public. The orientation distribution of selected paper and composite samples was measured using these tools.

The aim is to investigate models that predicts the potential of pulp and evaluate the relevance of the zero-span tensile index within these. Two chemical pulps made from softwood and eucalyptus were refined in a Voith-beater with different energy input in order to study the change of fiber morphology signals and other pulp and paper properties. Chemical, THP pulp from Södra Värö is also used as an initial analysis for morphological connections to Zero-span tensile index. The L&W Fiber Tester Plus is used in order to study the pulps fiber morphology and Pulmac 2000 for zero span. Handsheets are made for mechanical tests such as tensile properties, ZD-strength and optical properties. Many of the given signals change according to clear patterns with increasing refining energy. Using least square methods, formulas describing the development with high adaptation could be formulated. Many of the measured aspects changes over already known patterns. These are then applied in the models. Three possible models is tested: linear regression, Shear-Lag and Page. Of the three, only the two first ones where able to produce reliable models, whereas the third required data that was difficult to acquire at the same time as the adaptation was very low. The only model that use exclusively morphology data is linear regression.

Fiber networks are ubiquitous due to their low cost and high ratio of mechanical performance to weight. Fiber networks made of cellulose fibers from trees are used as information carriers (paper) and as packaging (board). Often the ideal product is both mechanically sturdy and possible to print on. This thesis investigates the underlying reasons for the mechanical performance of paper and board through the discretization and direct simulation of every fiber in the network. In Paper A the effect of fiber-fiber bond geometry on sheet stiffness is investigated. Many packaging products seek to maximize the bending stiffness by employing stiff outer layers and a bulkier layer in the middle. In bulky sheets, the fibers are frequently uncollapsed resulting in a more compliant bonded segment. Because all the loads in the network are transferred via the bonds, such compliance can cause unexpectedly large decreases in mechanical performance. Although many models have been presented which aim to predict the tensile stiffness of a sheet, these predictions tend to overestimate the resulting stiffness. One reason is that the bonds are generally considered rigid. By finite element simulations, we demonstrated the effect of the lumina configuration on the stiffness of the bonded segment on the scale of single fiber-to-fiber bonds, and that the average state of the fiber lumen has a marked effect on the macroscopic response of fiber networks when the network is bulky, has few bonds, or has a low grammage. Compression strength is central in many industrial applications. In paper B we recreated the short span compression test in a simulation setting. The networks considered are fully three-dimensional and have a grammage of 80 to 400 gsm, which is the industrially relevant range. By modeling compression strength at the level of individual fibers and bonds, we showed that fiber level buckling or bifurcation phenomena are unlikely to appear at the loads at which the macroscopic sheet fails. In paper C, we developed a micromechanical model to study the creation of curl in paper sheets subjected to a moisture gradient through the sheet. A moisture gradient is always created during the printing process, which may lead to out-of-plane dimensional instability. We showed that the swelling anisotropy of individual fibers bonded at non-parallel angles causes an additional contribution to the curl observed on the sheet level.

Examinator: Professor Mårten Olsson, KTH, Stockholm

QC 20190930

The failure properties of interfibre bonds are the key for the build-up of strength in fibrous materials such as paper and paperboard. In order to tailor the properties of such materials by chemical or mechanical treatments and to learn how such modifications influence the properties at a microscopic level, direct measurement of individual fibre--fibre crosses are typically performed. However, the state of loading in the interfibre joint, in testing of individual fibre--fibre crosses, is in general very complex and a greater understanding for how to evaluate the mechanical properties of interfibre joints is desirable. In Paper A, a method for manufacturing multiple fibre--fibre cross specimens and a procedure for testing interfibre joints at different modes of loading is presented. The method is applied to investigate the strength of fibre-fibre crosses with different geometry and at two principally different modes of loading. Also, an investigation on the influence of drying pressure, the drying method as well as a comparison of pulp fibres from two different degrees of refining is presented. The force at rupture is scaled in terms of different geometric parameters; nominal overlap area, length and width of the joint region. It is shown that neither of the methods of scaling unambiguously reduced the coefficient of variation of the mean strength and that the force at rupture in a peeling type of loading was about 20% of the ones tested in the conventional shearing type of loading. In Paper B, a procedure for evaluating interfibre joint strength measurements in terms of resultant forces and moments at rupture is presented. The method is applied to investigate the state of loading in fibre-fibre crosses tested in two principally different modes of loading. It is shown that for a typical interfibre joint test, the modes of loading other than pure shear, cannot in general be neglected and is strongly dependent on the structural geometry of the fibre-fibre crosses. Also, the stress state in the interface centroid was estimated in order to quantify how the mode of loading influence the amount of normal stresses that develop in relation to the amount of shear stresses in the interfibre joint.
De brottmekaniska egenskaperna hos fiberfogar är nyckeln för uppbyggnaden av styrka hos fibrösa material såsom papper och kartong. För att effektivt skräddarsy sådana materials egenskaper genom kemisk eller mekanisk behandling och för att förstå hur sådana modifieringar påverkar egenskaperna på en mikroskopisk nivå är provning av individuella fiber-fiber-kors en allmänt använd metod. Belastningen i en fiberfog vid provning av individuella fiber-fiber kors är dock generellt mycket komplicerad och ytterligare kunskap om hur fiberfogars mekaniska egenskaper skall utvärderas är önskvärd. I Artikel A, presenteras en metod för samtidig tillverkning av flera fiber-fiber kors samt en metod för mekanisk provning av dessa med olika typer av belastning. Metoden tillämpades för att studera styrkan av fiber-fiber-kors med olika geometri och vid två olika lastfall. En undersökning av hur torktrycket, torkmetoden samt graden av malning inverkar på fogstyrkan presenteras. De uppmätta brottlasterna skalades med olika karakteristiska längder för fogen; nominell överlapparea samt fogens längd och bredd. Resultaten visade att ingendera av normaliseringsmetoderna reducerade variationskoefficienten (av medelvärdet av styrkan) samt att brottlasten för en globalt fläkande belastning var omkring 20 % av brottlasten för prov utförda med den konventionella skjuvande belastningen. I Artikel B, presenteras en metod för utvärdering av mätningar av styrkan hos fiberfogar med hänseende på kraft- och moment- resultanterna i gränsytan mellan fibrerna. Metoden används för att studera belastningsmoden hos fiber-fiber--kors provade i två principiellt olika lastfall. Resultaten visar att för ett typiskt fiberfogsprov av isolerade fiber-fiber-kors med långa fria fibersegment, så kan inte belastningsmoderna vid sidan av skjuvning försummas och att de är starkt beroende av fiber-fiber-korsets geometri. För att kunna jämföra fiberfogar av olika storlek och kvantifiera förhållandet mellan normal- och skjuvbelastningen i fogen skalades de resulterande krafterna och momenten med tvärsnittsstorheter baserade på en approximation av fogareans utformning.

QC 20130125

BiMaC Innovation

Paper is used in a wide range of applications, each of which has specific requirements on mechanical and surface properties. The role of paper strength on paper performance is still not well understood. This work addresses the mechanical properties of paper by utilizing fiber network simulation and consists of two parts.In the first part, we use a three-dimensional model of a network of fibers to describe the fracture process of paper accounting for nonlinearities at the fiber level (material model and geometry) and bond failures. A stress-strain curve of paper in tensile loading is described with the help of the network of dry fibers; the parameters that dominate the shape of this curve are discussed. The evolution of network damage is simulated, the results of which are compared with digital speckle photography experiments on laboratory sheets. It is concluded that the original strain inhomogeneities due to the structure are transferred to the local bond failure dynamics. The effects of different conventional and unconventional bond parameters are analyzed. It has been shown that the number of bonds in paper is important and that the changes in bond strength influence paper mechanical properties significantly.In the second part, we proposed a constitutive model for a fiber suitable for cyclic loading applications. We based the development of the available literature data and on the detailed finite-element model of pulp fibers. The model provided insights into the effects of various parameters on the mechanical response of the pulp fibers. The study showed that the change in the microfibril orientation upon axial straining is mainly a geometrical effect and is independent of material properties of the fiber as long as the deformations are elastic. Plastic strains accelerate the change in microfibril orientation. The results also showed that the elastic modulus of the fiber has a non-linear dependency on a microfibril angle,with elastic modulus being more sensitive to the change of microfibril angle around small initial values of microfibril angles. These effects were incorporated into a non-linear isotropic hardening plasticity model for beams and tested in a fiber network in cycling loading application model, using the model we estimated the level of strains that fiber segments accumulate at the failure point in a fiber network.The main goal of this work is to create a tool that would act as a bridge between microscopic characterization of fiber and fiber bonds and the mechanical properties that are important in the papermaking industry. The results of this work provide a fundamental insight on mechanics of paper constituents in tensile as well as cyclic loading. This would eventually lead to a rational choice of raw materials in paper manufacturing and thus utilizing the environment in a balanced way.

QC 20130605

Office waste paper is one of the fastest growing segments of the recycled fiber industry. Toner particles are rigid, insoluble and difficult to disperse and detach from fibers. Therefore papers made from recycled office waste having high toner content will contain noticeable ink particles. This work will consider an alternative way of efficient de-inking using plasma polymers which will not affect the fibers chemically or mechanically. The focus is development and characterization of plasma-deposited films to serve as a barrier film for the adhesion of ink toner to the paper fibers and thereby enhance ink lift off from the fibers. The plasma treated paper is coated with fluorocarbon (PFE) and polyethylene glycol (PFE) films, with constant thickness of PFE and varying the thickness of PEG by 1500, from 1500 to 4500, for the three cases studied (PFE greater than PEG, PFE=PEG, PFE less than PEG). Handsheets were made using virgin fibers to eliminate effects of fillers. Once the sheets were coated and printing performed, they were re-pulped and both the slurry and the de-inking surfactant were placed in a flotation cell. Handsheets were made from the collected foam and stock and were scanned for particle count. The results indicated higher ink loss for the cases with increased thickness of polymer films. A handsheet with a 7500 film (PFE = 3000 and PEG = 4500) showed 61% ink removal compared to 38% for handsheets with no film deposited. There was also less material loss for the cases with higher polymer film thickness.

The current trends in papermaking involve, but are not limited to, maintaining the dry strength of paper material at a reduced cost. Since any small changes in the process affect several factors at once, it is difficult to relate the exact impact of these changes promptly. Hence, the detailed models of the network level of a dry sheet have to be studied extensively in order to attain the infinitesimal changes in the final product. In Paper A, we have investigated a relation between micromechanical processes and the stress–strain curve of a dry fiber network during tensile loading. The impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds, is discussed. In Paper B, we studied the impact of the chemical composition of the fiber cell wall, as well as its geometrical properties, on the fiber mechanical properties using the three-dimensional model of a fiber with helical orientation of microfibrils at a range of different microfibril angles (MFA). In order to accurately characterize the fiber and bond properties inside the network, via statistical distributions, microtomography studies on the handsheets have been carried out. This work is divided into two parts: Paper C, which describes the methods of data acquisition and Paper D, where we discuss the extracted data. Here, all measurements were performed at a fiber level, providing data on the fiber width distribution, width-to-height ratio of isotropically oriented fibers and contact density. In the last paper, we utilize data thus obtained in conjunction with fiber morphology data from Papers C and D to update the network generation algorithm in order to produce more realistic fiber networks. We also successfully verified the models with the help of experimental results from dry sheets tested under uniaxial tensile tests. We carry out numerical simulations on these networks to ascertain the influence of fiber and bond parameters on the network strength properties.

QC 20160613

Reducing losses of usable waste fiber from paper mills conserves valuable resources and has the capacity to produce considerable economic returns to the manufacturer. The purpose of this research effort was to evaluate the potential for the prevention of loss and/or recovery of usable waste fiber from paper machines within a fine paper mill. Further, a preliminary evaluation of fiber loss prevention strategies and fiber recovery technologies was conducted.

The paper mill in question experienced losses of usable waste fiber to the sewer in amounts approaching, and sometimes exceeding 40 tons/day. An existing database of usable fiber test results was analyzed to determine patterns of fiber loss. Further testing showed that the most significant fiber losses resulted from centrifugal cleaner cones. These cones, designed to remove foreign material from stock, are one step in a series of mechanical cleaning devices in the stock preparation area of the paper mill. Cleaner cone systems on two of the paper machines were found to contribute most significantly to total fiber loss.

Contrary to cleaner cone design, the dirt content of fiber rejects from cones experiencing excessive loss was very low. Cleaner cones on other machines operated normally. These rejects were extremely dirty and quantities of fiber were low. These results indicate poor operating efficiency of two of the cleaner cone systems in question. By adding cones where space is available, system capacity and efficiency will increase, fiber losses will decrease, and the dirt content of rejects will increase. This will result in substantial resource and financial savings to the paper mill.

Technologies have been developed to recover usable fiber from paper mill sludge. However, prior to further investigation of the use of such innovations at this paper mill, efforts should focus on the reduction of fiber loss from point sources.
Master of Science

The thesis investigates the modification of paper into an ion- and electron-conductive material, and as a renewable material for electronic device. The study stretches from investigating the interaction between the cellulosic materials and the conducting polymer to demonstrating the performance of the conductive paper by printing the electronic structure on the surface of the conductive paper. Conducting materials such as conducting polymer, ionic liquids, and multi-wall carbon nanotubes were deposited into the fiber networks. In order to investigate the interaction between the conducting polymer and cellulosic material, the adsorption of the conducting polymer poly(3,4-ethylenedioxythiophene): poly(4-styrene sulfonate) (PEDOT:PSS) onto microcrystalline cellulose (MCC) was performed. Electroconductive papers were produced via dip coating and rod coating, and characterized. The Scanning Electron Microscopy (SEM) / Energy Dispersive Spectroscopy (EDS) images showed that the conducting polymer was deposited in the fiber and in fiber-fiber contact areas. The X-ray Photoelectron Spectroscopy (XPS) analysis of dip-coated paper samples showed PEDOT enrichment on the surface. The effects of fiber beating and paper formation, addition of organic solvents and pigments (TiO2, MWCNT), and calendering were investigated. Ionic paper was produced by depositing an ionic liquid into the commercial base paper. The dependence to temperature and relative humidity of the ionic conductivity was also investigated. In order to reduce the roughness and improve its printability, the ionic paper was surface-sized using different coating rods.  The bulk resistance increased with increasing surface sizing. The electrochemical performance of the ionic paper was confirmed by printing PEDOT:PSS on the surface. There was change in color of the polymer when a voltage was applied. It was demonstrated that the ionic paper is a good ionic conductor that can be used as component for a more compact electronic device construction. Conductive paper has a great potential to be a flexible substrate on which an electronic structure can be constructed. The conduction process in the modified paper is due to the density of charge carriers (ions and electrons), and their short range mobility in the material. The charge carrying is believed to be heterogeneous, involving many charged species as the paper material is chemically heterogeneous.

Fel ordningsnummer (2010:28) är angivet på omslaget av fulltextfilen.

Printed Polymer Electronics on Paper

With the advent of X-ray computerised tomography (CT), the possibility of capturing precise volumetric 3D images has become an invaluable tool within the material sciences. With tomographs and synchrotrons becoming more readily available to researchers and scanning time decreasing with newer equipment, the amount of data to be analysed is steadily rising. This rapid increase in data acquisition motivates the development of automatic methods to transform CT images from qualitative to quantitative data. In this work, a method to automatically characterise paper fibres from CT images based on their centre-line and mapping their deformation is presented. Methods for fibre characterisation are presented and tested on computer-generated fibres and CT images of paper fibres.
Med tillkomsten av datorbaserd röntgentomografi (CT) har möjligheten att fånga exakta volymetriska 3D-bilder blivit ett ovärderligt verktyg inom materialvetenskapen. Den mängd data som ska analyseras växer hela tiden tack vare ökad tillgänglighet till tomografer och synkrotroner och minskad skanningstid i och med den tekniska utvecklingen av utrustningen som används. Denna snabba ökning av datainsamling motiverar utvecklingen av automatiska metoder för att omvandla CT-bilder från kvalitativa till kvantitativa data. I detta arbete presenteras en metod för att automatiskt karakterisera pappersfibrer från CT-bilder baserad på deras mittlinje och kartlägga deras deformation. Metoder för fiberkarakterisering presenteras och testas på datorgenererade fibrer och CT-bilder av pappersfibrer.

Abstract This thesis describes the application of Low Coherence Interferometry (LCI) and Optical Coherence Tomography (OCT) in paper measurements. The developed measurement system is a combination of a profilometer and a tomographic imaging device, which makes the construction versatile and applicable in several paper measurement applications. The developed system was first used to measure the surface structure of paper. Different grades of paper were selected to provide maximum variation in surface structure. The results show that the developed system is capable of measuring grades of paper from rough base paper to highly coated photo printing paper. To evaluate the developed system in surface characterization, the roughness parameters of five laboratory-made paper samples measured with the developed system and with a commercial optical profilometer were compared. A linear correlation was found with roughness parameters Ra and Rq. Next, the surface quality of paper was evaluated using LCI, a Diffractive Optical Element Based Glossmeter (DOG), and a commercial glossmeter. The results show linear correlation between Ra and gloss measured with the commercial glossmeter. The roughness Ra and averaged gloss measured with the DOG didn't give such a correlation, but a combination of these techniques provided local properties of gloss and surface structure, which can be used to evaluate the local surface properties of paper. In the next study, determination of the filler content of paper using OCT is discussed. The measurement results show clear correspondence of the slope of the averaged logarithmic fringe signal envelope and the filler content. The last studies focus on 2D and 3D imaging of paper using OCT and begin with imaging of a self-made wood fiber network. The visibility of the fibers was clear. Next, several refractive index matcing agents are studied by means of light transmittance and OCT measurements to find the best possible agent for enhancing the imaging depth of OCT in paper. Benzyl alcohol was found to have the best possible combination of optical, evaporation, and sorption characteristics, and it is applied in 2D and 3D visualizations of copy paper.

The area of the digital image processing is getting more attention in the hope that it will increase the accuracy of any scientific measurements, such as in determining an object velocity, temperature, and size. While human vision is excellent to recognize and differentiate objects, it has been proven to be a poor tool when it comes to measure the object performance. One of many digital image processing applications is texture analysis whose purpose is to evaluate image patterns. The purpose of this dissertation is to investigate the use of texture analysis as a tool to micro fiber dispersion measurement. Micro fiber dispersion can be found in many applications such as in paper and industry powder engineering. Three cases related to micro fiber dispersion were investigated in this study. The first case was the experimental study of the dispersion in open water channel. Sets of synthetic fibers were put into water channel to simulate a process that can be found in papermaking industry. The research investigated the effect of three operating parameters: fluid velocity, fiber consistency, and fiber aspect ratio to fiber dispersion. Using two-factorial experimental design technique, the main and interaction effects of these parameters were evaluated. The study found that increasing fluid velocity, fiber aspect ratio, and consistency decreased the dispersion level. The study also found that the effect of individual parameters is more pronounced than the role of the interactive terms on the fiber flocculation. The second case considered was applying the fiber dispersion analysis to computer-synthesized images consisting of different arrangements of fibers. Four sets of sub-cases were presented. These sub-cases were divided based on the fiber-concentrated location and fiber distribution. The use of computer-synthesized images was found to be very useful to simulate real situation during fiber dispersion. The third case investigated the fiber distribution on a dry paper. Images for different types of paper were taken and evaluated to see the dispersion level of each type of paper. It was found that the current texture analysis was applicable to determine the dispersion level for dry papers. While three cases indicated that the texture analysis can be used to investigate the fiber dispersion, the texture analysis used here is not a perfect and universal method and may not be suitable to analyze other types of dispersions. The human vision will always be essential to determine if the texture analysis is applicable to any other problem.

Trashures celebrates my debut in the sustainable world and is my public statement of change. It is essentially provocative, informative and educational and serves three major fronts. First, Trashures aims to raise awareness among visual artists. Second, it seeks to introduce and explore the use of agri-pulp papers in Graphic Design, as a viable commercial solution. Third, it culminates in an invitation to visual artists to search for sustainable solutions. Trashures is about transformations. It highlights the transformation of passive materials into active ones, or the transformation of waste into either papers or as subject matter, as a sustainable way to think over waste and consider it as a potential and genuine resource in Graphic Design.

Paper materials are renewable and recyclable and are often used for packaging applications, e.g., as in corrugated fiberboard boxes. From an engineering perspective, paper materials can be used to construct packaging with low weight but with high relative strength. However, compared to other packaging materials, it can be a challenge to design paper-based packaging for distribution chains with demanding conditions. Boxes made from paper can be sensitive to exposure of moisture, duration of load, and dynamic forces. Along the distribution chain, boxes can be exposed to forces that could potentially cause failure before the boxes intended service life is fulfilled. Therefore, it is important to know how to predict the failure distribution for a specific combination of packaging and distribution chain so that materials with the right properties can be chosen for a given purpose and the risk of failures can be minimized. In this project, we have investigated a statistical material model developed by Bernard D. Coleman. It is based on three material parameters that describe the cumulative distribution function (CDF) of a fiber-breaking behavior for an arbitrary load history. The model has been shown to work for fiber network systems subjected to constant load and constant load rate (CLR). Our purpose was to investigate if it is applicable for fiber network systems of higher structural hierarchy and for more complex load histories. To investigate this, we have performed compression tests with CLR on four different types of corrugated fiberboard and determined the material parameters. Afterward, we performed compression tests for a more complex load history. A periodic, triangular-shaped, load curve was chosen for cyclic testing. Finally, we used the material parameters from the CLR tests to determine the CDF for the periodic load cases. We compared the result with an empirical CDF. The CDFs showed to be in relatively good agreement, but there were some differences. We found that our measurements turned out to produce load history data that deviated from the intended load history. The material parameters were also shown to be less accurate than expected. Due to these deviations, we could not expect a perfect agreement between the CDFs. Therefore, we can not with certainty state that Coleman’s theory is applicable for varying load histories. However, despite the difficulties to experimentally achieve the intended load history, the results showed good agreement in several cases, and the deviations from the theory could possibly be explained by the load history deviations. To be certain, more accurate measurements with higher accuracy need to be done.

One of the primary objectives of this thesis was to design fiber/filler/polymer structures for newsprint and in the process develop a greater understanding of fiber/filler/ polymer structures. Five different designed structures were created for study. The designed structures were composed of virgin, hydrosulfite bleached, TMP southern pine, Georgian kaolin clay and various polymers. Five filler levels from 0% to 20% were employed with each of these different structures. Numerous physical tests were used to gather data which would help to develop an understanding for the macroscopic properties of the structures. Paper structures were created and data from bulk physical tests and particle based SEM image analyses were compared. Comparisons were made using a statistical method called Principal Component Analysis (PCA) where the data is grouped and reduced to find data correlations not readily apparent in the raw data.

Supercapacitors are important electrochemical energy storage devices for microelectronic and telecommunication systems, electric cars, and smart grids. However, the energy densities of existing supercapacitors are still inadequate for many applications. Vanadium oxides have been studied as viable supercapacitor alternatives, with varying results. Methods are often complicated or time-consuming, and electrode fabrication often includes carbon powder and binder. The objective of this work was to study the effect of processing conditions on specific capacitance of supercapacitors based on vanadium oxides coated on carbon fiber papers. This study was conducted to form easily-fabricated compounds of vanadium oxides which could offer promise as pseudocapacitor material, and to nucleate these compounds directly onto inexpensive carbon fiber without binder. The incipient wetness impregnation technique was used to fabricate the electrodes. Electrochemical performance of the resulting electrodes was tested in a Swagelok-type electrochemical two-electrode cell, and the electrodes were characterized by XRD and SEM. Interesting nanofeatures were formed and the vanadium oxides exhibited pseudocapacitance at a respectable level.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第15586号
農博第1836号
新制||農||984(附属図書館)
学位論文||H22||N4459(農学部図書室)
28107
京都大学大学院農学研究科森林科学専攻
(主査)教授 木村 恒久, 准教授 山内 龍男, 教授 髙野 俊幸
学位規則第4条第1項該当

The effect of pH on fiber and paper properties, during beating and sheet formation, was investigated for three different pulps. The pulps were pH adjusted to four different pH levels between 3 and 9. Isotropic laboratory sheet were made of both unbeaten and beaten pulps. The beaten neutral sulfite semi-chemical pulp and bleached softwood kraft pulp were affected by changes in pH; bleached softwood kraft pulp in a minor extent due to less fiber surface charges. Compared to the other pH levels, pH 3 showed a lower fiber surface charge, water retention value, tensile index, tensile stiffness index, compressive index and edge crush resistance index. SEM pictures showed a denser network at pH 9 than for pH 3. This was seen for both neutral sulphite semi-chemical and softwood kraft pulp. The unbeaten pulps and beaten bleached hardwood kraft pulp were not affected by changes in pH. SEM pictures showed no difference in the fiber network for bleached hardwood kraft pulp. A mill trial, with neutral sulphite semi-chemical pulp, at pH levels between pH 4.8 and pH 5.6 was completed. No significant difference was seen for any mechanical property.

Thesis (Ph. D.)--Institute of Paper Science and Technology, Georgia Institute of Technology, 2005.
Alan Rudie, Committee Member ; Derek Page, Committee Member ; Douglas Coffin, Committee Member ; Kari Ebeling, Committee Member ; Timothy Patterson, Committee Member. Includes bibliographical references (p. 222-231).

In manufacturing of paper and paperboard, optimized fiber usage has crucial importance for process efficiency and profitability. Dry strength of paper is one of the important quality criteria, which can be improved by adding dry strength additive that affect fiber to fiber bonding. This study is using the micromechanical simulations which assist interpretation of the experimental results concerning the effect of strength additives. A finite element model for 3D dry fiber network was constructed to study the effect of bond strength, bond area and the number of bonds numerically on the strength of paper products. In the network, fibers’ geometrical properties such as wall thickness, diameter, length and curl were assigned according to fiber characterization of the pulp and SEM analyses of dry paper cross-section. The numerical network was created by depositing the fibers onto a flat surface which should mimic the handsheet-making procedure. In the FE model, each fiber was represented with a number of quadratic Timoshenko beam elements where fiber to fiber bonds were modelled by beam-to-beam contact. The contact model is represented by cohesive zone model, which needs bond strength and bond stiffness in normal and shear directions. To get a reasonable estimate of the bond stiffness, a detailed finite element model of a fiber bond was used. Additionally, the effect of different fiber and bond geometries on bond stiffness were examined by this model since the previous work [13] indicated that the bond stiffness can have a considerable effect on dry strength of paper. The network simulation results show that the effect of the strength additive comes through improving the bond strength primarily. Furthermore, with the considered sheet structure, both the fiber bond compliance and the number of bonds affect the stiffness of paper. Finally, the results of the analyses indicated that the AFM measurements of the fiber adhesion could not be used directly to relate the corresponding changes in the bond strength. The fiber bond simulation concluded that fiber wall thickness has the most significant effect on the fiber bond compliance. It was also affected by micro-fibril orientation angle, bond orientation and the degree of pressing.

The interdependency between filler retention and paper formation is well-known, where a high retention is accompanied by impaired formation. A challenge for today’s papermakers is to increase the competitiveness for uncoated and coated fine paper, by improving the formation at the same level of retention.

Over the years, the use and the demands of retention aids have increased as a consequence of a higher system closure, increased machine speeds and increased filler content. The knowledge of whether some retention aid systems are more or less detrimental to paper formation than other systems, is very limited. The insuffiency of knowledge is, however, also true for other chemical, mechanical and interacting factors, which influence the retention/formation relationship in a complex manner.

In order to investigate the retention/formation relationship (features, retention aids, dosage points, etc.), a pilot-scale fourdrinier former (R/F-machine) has been developed. The R/F-machine provides a short circulation of the white water and controlled experimental conditions and is appropriate for cost-effective investigations. Moreover, the R/F-machine has been designed to have a short residence time to chemical equilibrium and the machine has also shown high reproducibility in the results.

This licentiate thesis presents the R/F-machine and examines, during constant experimental conditions, the retention/formation relationships for some different retention aid systems. Three single-component cationic polyacrylamides with varying molecular weights and two polyacrylamide-based microparticulate systems with varying microparticles were examined. The retention aid systems were investigated on the R/F-machine, for a fine paper stock (90 % bleached hardwood and 10 % bleached softwood) with addition of 25 % filler (based on total solids content).

The results showed that the retention/formation relationship was not dependent on the retention aid system used. All systems showed the same relationship between retention and formation. On the other hand, the various retention aid systems provided different effects considering their retention performance.

The presteaming of wood chips is an important step in the chemical pulping industry. It removes the air from within wood chips, allowing the cooking liquor to better impregnate wood chips, which leads to a more uniform cooking process, and lowers the amount of rejects. When steaming at atmospheric pressure, it is important that the temperature of the wood chips reach 100ᴼ C, as otherwise there will be an equilibrium leaving some air left inside. Having poorly steamed chips in a process could cause severe problems when it comes to reaching the targeted kappa number, or having the adequate retention time in the digester. There are a few different ways in which the wood chips are presteamed within the industry, however, there is little experimental data regarding the heating time of wood chips that can be used when designing these systems. Most studies have mainly focused on the air removal, or improvement of the impregnation step, and the few studies that have included the heating of the wood chips were limited to only one type of wood chip, or failed to specify the experimental details. Therefore, handmade wood chips pine and birch, two tree species commonly found in Sweden, were steamed in an ATEX designed digester with a steam jacket. The wood chips had thermocouples inside them and the temperature and time was recorded, and the effect of different parameters on the heating could thus be studied.The results revealed that there could be more than a minute in average time difference between wood chips of different thicknesses, both for birch and pine, although the difference in heating time was more linearly correlated to thickness for the birch chips. Pine chips of different thickness were also studied when the pressure inside the digester was allowed to build up, which showed that it is mainly thicker chips that have reduced heating time under such circumstances, as the thinner chips stop heating for a while when the steam condensates on colder surroundings. When comparing heartwood and sapwood chips, it was noted that the difference in heating time could be around 1 minute at most for pine, but only a few seconds for birch. This was most likely due to the pine heartwood and sapwood having distinct moisture contents, 25 % and 58 % respectively, while it was 41% and 42 % in birch heartwood and sapwood. Birch and pine chips wee also steamed together, however, the difference in heating time was only a few seconds on average. When comparing these experimental results with simulation data of the steaming of wood chips, it fit rather well when it came to the general heating time. However, the effect of increased moisture content had a much larger impact in the simulations, which predicted that more moist wood chips would need several minutes more steaming time, while the experiments only showed at difference of, at most, around 1 minute. When comparing with old experimental data, that has been the basis for the design of older steaming processes, it gave very distinct results, where the effect of thickness did not have as big of an impact as in the old data. No further comparison could be made, however, as the experimental conditions for the old experimental data were not known. Based on these results, it was noted that a steaming time of at least 5 minutes would be needed to ensure that even the largest and more moist chips could reach 100ᴼ C in this system. Finally, the condensate from the handmade birch and pine chips was analyzed. It revealed the presence of low molecular weight compounds like methanol, formic acid and acetic acid. Common metal ions were also present,although the amount of sodium ions clearly surpassed the rest. The pH of the pine condensate was measured and it was very high, which implies that the condensate was contaminated.
Basning av flis är ett viktigt steg inom kemisk massaindustri. Det avlägsnar luft från flisens insida vilket gör att impregneringen av luten blir bättre, vilket i sin tur leder till en jämnare kokning och färre rejekt. När basningen sker vid atmosfärstryck är det viktigt att flisen når en temperatur på 100ᴼ C, annars kommer det finna ett jämviktstillstånd där lite luft blir kvar på insidan. Att ha otillräckligt basad flis i en process skulle kunna orsaka stora problem när det gäller att nå önskade kappatal, eller att ha en önskad retentionstid i kokaren.Basningen görs på ett par olika sätt inom industrin, men det finns väldigt lite experimentell data tillgänglig angående flisens upvärmning, som skulle kunna användas när dessa system designas. De flesta vetenskapliga studier har fokuserat på luftborttagningen eller på förbättringar av impregneringssteget, medan de få studier som inkluderat mätningar av temperaturen ofta varit begränsade till ett slags trä, eller så har de inte inkluderat detaljer kring experimentet. Därför basades handgjorda flisbitar av björk och tall från Sverige i en ATEX-designad kokare med en ångjacka. Flisen hade termoelement inuti och temperaturen samt tiden kunde avläsas, vilket gjorde det möjligt att studera effekten av olika parametrar. Resultaten visade att det kunde skilja mer än en minut i uppvärmningstid mellan flisbitar av olika tjocklekar, både för tall och björk, även fast skillnaden i uppvärmningstid var mer linjärt relaterad till tjockleken för björkflisen. Tallflisen studerades också när trycket inuti kokar tilläts stiga vilket visade att det de tjockare flisbitarnas uppvärmningstid som kortas ned mest, eftersom de tunnare flisbitarna slutar värmas upp när ångan börjar kondensera på kallare ytor runt omkring. När flis av splintved och kärnved jämfördes visade det sig att skillnaden i uppvärmningstid kunde vara omkring 1 minut för tall, men endast ett par sekunder för björk. Detta beror troligtvis på att kärnveden och splintveden i tall hade stora skillnader i fukthalt, 25 % respektive 58 %, medan det för björk var 41 % och 42%. Björkflis och tallflis basades även tillsammans men det skillde bara ett fåtal sekunder i genomsnitt i uppvärmningstid. När den experimentella datan jämfördes med data från simuleringar visade det sig att de stämmer väl överens när det gäller uppvärmningstiden i allmänhet. Å andra sidan förutspådde simuleringsdatan att en ökad fukthalt skulle leda till flera minuters skillnad i uppvärmningstid, medan endast 1 minuts skillnad uppmättes. När jämförelser gjordes med gammal experimentell data som använts som grund för tidigare processers design, var resultaten ganska olika eftersom den gamla datan visade en större effekt av ökad tjocklek än den som uppmättes.Tyvärr kunde inte fler jämförelser göras eftersom detaljerna kring experimentet bakom den gamla datan inte var kända. Slutligen analyserades även kondensatet från de handgjorda flisbitarna av tall och björk. Det visade att det fanns små mängder av små polära organiska ämnen, såsom metanol, myrsyra och ättiksyra. Vanliga metalljoner detekterades också, där mängden natrium var klart större än övriga metalljoner. Tallkondensatets pH mättes och det visade sig vara väldigt högt, något som tyder på att det troligtvis var förorenat.

The characteristics of products made from pulp can be modified through different methods. If the pulp is refined either laboratory or industrially, the fibres in the pulp become more flexible and therefore creates stronger bonds to each other, which results in a final product with a higher strength. The refining process also causes the formation of small fibre pieces that are called fines, which also contribute to the increased strength. The major component in pulp is cellulose, which can be chemically modified to materials with changed properties. Periodate oxidation of cellulose results in dialdehyde cellulose that can be further reduced with sodium borohydride to obtain dialcohol cellulose, which is a material with a higher ductility compared to regular cellulose. In this thesis, different pulp compositions and their influence on the production of dialcohol cellulose (DALC) were investigated. The aim of the study was to find out how the ductility of paper sheets made from DALC were affected by the presence of fines in the pulp. Nine different pulp compositions were prepared for the modification: unrefined pulp, unrefined pulp with added fines, industrially refined pulp, dewatered industrially refined pulp, and pulp refined 1000, 3000, 5000, 10 000 and 15 000 revolutions with a PFI Mill. Paper sheets were made with a Rapid Köthen sheet former and the mechanical properties of the sheets were tested with a Zwick Roell tensile tester. The surface of the sheets were analyzed using a scanning electron microscope (SEM). The results obtained from the tensile tests showed that DALC made from unrefined pulp and DALC made from pulp highly refined with a PFI Mill, resulted in sheets with a high strain-at-break. For each increased degree of refining with the PFI Mill, the resulting DALC sheets showed an improved elongation and tensile strength. When DALC was produced from industrially refined pulp and from unrefined pulp with added fines, the resulting sheets had a lower strain-at-break. These findings indicate that the presence of fines in the pulp do have a negative effect on the ductility of the resulting DALC sheets.

Biodegradable polymers are emerging as a new solution to satisfy the increasing demand of greenenvironmentally friendly material. At the same time, the interest for lighter and stronger structures never stops growing. In this paper, we report the production steps to achieve cellulose nanofibrils (CNF) composite filaments via a new green synthesis route known as wet spinning. This new technique avoids the traditional harmful viscose process and produces biodegradable CNF filaments with interesting mechanical properties. This approach is then applied to produce never seen before composite CNF filaments using a three-layered head extruder. In order to obtain conductive filaments, PEDOT/PPS is successfully mixed with CNF to produce in-situ composite filaments. Scanning electron microscopy (SEM), atomic force measurements and tensile tests are employed to characterize the properties of the filaments.
Biologiskt nedbrytbara polymerer börjar framträda som en lösning för det ökade behovet avmiljövänliga material. Samtidigt så växer intresset för lättare och starkare strukturer. I denna rapport tar vi upp produktionsstegen för att uppnå nanofibril komposit cellulosa fibrer (CNF), med hjälp av en ny grön polymerisation mest känd som ”wet spinning”. Med denna nya teknik så behövs inte dem traditionella miljöfarliga viskosprocesserna och man producerar biologiskt nedbrytbara CNF filaments med intressanta mekaniska egenskaper. Denna metod appliceras sen för att producera en komposit som aldrig setts innan. CNF fibrer som består av tre lager ”head-extruder”. För att få fibrer med ledningsförmåga så mixas PEDOT/PPS med CNF för att producera ”in-situ komposit fibrer”. Svepelektronmikroskop (SEM), atomkraftsmikroskopi och töjningstester används för att karaktärisera egenskaperna av fibrerna.

Environmental issues are more and more present in our societies. Pollution engendered by plastic waste have drastically increased these past decades, causing several threats to the ecosystem. Therefore, the need of new biodegradable plastics to replace the actual petroleum-based ones is urgent. Cellulose could be a potential substitute since it is a biopolymer, abundant on Earth. However its properties have to be enhanced to be competitive towards actual plastics. The aim of the project is therefore to get a better understanding of cellulose-cellulose interactions. It focuses on the adhesion between cellulosic surfaces. Contact adhesion measurements have been performed on cellulose beads, with different treatments. All the beads had the same size and same concentration. Some of them were native whereas others were charged (600 µeq/g). Half of the native beads were surface modified with a starch coating or a Layer by Layer technique using cationic starch and an anionic polyelectrolyte (EXPN64 or FennoBond 85E). The project included preparation of the surface modified beads, pull-off tests, where load and position were recorded as a function of time, as well as measurements of the contact area. It was found that a higher energy was needed to separate charged and surface modified beads, especially the ones modified with EXPN 64, compared to native beads. The project have also shown that the types of beads influenced the contact area and the strength. However a trend was sometimes difficult to find. The data and results obtained in this project could be further re-used to enlarge the study field and investigate the influence of other parameters (size, concentration) on the adhesion of cellulose beads.
Miljöfrågor är mer och mer närvarande i våra samhällen. plastavfall har ökat drastiskt de senaste decennierna och orsakat flera hot mot ekosystemet. Därför är behovet av ny biologiskt nedbrytbar plast för att ersätta de petroleumbaserade brådskande. Cellulosa kan vara en potentiell ersättare eftersom det är en biopolymer. Emellertid måste dess egenskaper förbättras för att vara konkurrenskraftiga gentemot petroleumbaserad plast. Syftet med projektet är därför att bättre förstå cellulosa-cellulosa-interaktioner. Den fokuserar på vidhäftningen mellan cellulosaytor. Kontaktvidhäftningsmätningar har utförts på cellulosapärlor med olika behandlingar. Alla pärlor hade samma storlek och koncentration. Vissa av dem var naturliga medan andra laddades (600 µeq/g). Projektet inkluderade beredning av ytmodifierade pärlor, utdragningstester, där belastning och position registrerades som en funktion av tiden, samt mätningar av kontaktområdet. Det visade sig att högre energi behövdes för att separera laddade och ytmodifierade pärlor, särskilt de modifierade med EXPN 64, jämfört med tonativa pärlor. Projektet har också visat att typerna av pärlor påverkade kontaktområdet och styrkan. Men en trend var ibland svår att hitta. Uppgifterna och resultaten som erhållits i detta projekt kan vidare användas för att förstora studiefältet och undersöka påverkan av andra parametrar (storlek, koncentration) på vidhäftningen av cellulosapärlor.

For all kinds of paperboard packages, the bending stiffness of the paperboard is a crucial property. In multi-ply folding boxboard (FBB) grades, this is obtained by placing different stocks in the outer and centre plies of the board. In the outer plies, a stock with a high tensile stiffness is used, typically made from refined kraft pulp fibres. In the middle ply/plies a stock with more bulky properties is placed, typically comprising of a high proportion of CTMP (chemi-thermomechanical pulp). CTMP fibres are stiffer and more inflexible with poor bonding abilities resulting in low strength properties. To increase the bonding strength in the middle ply, broke, containing chemical pulp is added, and sometimes refined chemical kraft pulp as well. Both fibres and fines, i.e. smaller fibre fragments, in a pulp have a significant contribution to the properties of the product. Fines produced during refining of chemical pulp are especially beneficial for increasing the strength. To achieve pulp fraction with higher fines content the pulp can be fractionated with a micro-perforated screen basket; a fine fraction produced from a screen with very small holes will contain a large proportion of fines. By adding such a fine fraction to a middle ply stock, the bulk properties of the main pulp, for example a CTMP, can be conserved as less refining of this pulp is required to achieve the targeted strength properties. However, a drawback is that the fine fraction usually has a very low mass concentration after the screening process as a lot of water pass through the screen together with the fines and fibre fragments. The excess water must be removed to maintain the water balance of the papermaking process. Further, the larger volumes require extra pumping capacity. A resource-efficient production of a fine fraction must target a high fine fraction mass concentration and a high content of fines and short fibre fragments in order to be implemented industrially. The focus of the present work was on separation efficiency (i.e. the difference in fibre length distribution caused by screening) and process efficiency (i.e. the concentration of the fine fraction) for production of a fine fraction of chemical pulp by screening, and the utilisation of the fine fraction as strength agent. Pilot-scale fractionation trials with a pressure screen with different microperforated screen baskets were performed in order to evaluate how the separation efficiency and process efficiency were affected by parameters such as feed concentration, pulp type (hardwood or softwood kraft pulp), hole size of the screen, and refining treatment prior to screening. The trials were evaluated using fibre length distributions, flow rates and concentrations of viii the feed flow and the fractions. Here, two complementary quantitative measures, Proportion in fine fraction (for process efficiency) and Fine fraction enrichment (for separation efficiency), were developed. To evaluate the strength enhancing effect of the obtained fine fraction, a lab scale study was performed where the fine fraction of a highly refined pulp was compared with the highly refined pulp as strength agent for a CTMP. The results of this study were verified in a pilot paper machine trial. In a second pilot paper machine trial, sheets with different CTMP proportions in the middle ply were studied in order to find out if the bulk could be increased while maintaining strength, by using a fine fraction made from refined chemical pulp. Regarding process efficiency, it was found that the most important parameter to obtain a high fine fraction concentration was a high feed concentration. Further, a higher fine fraction concentration for a given screening process was also obtained when using hardwood pulp and refining the pulp prior to the screening process. A higher feed concentration also had a positive effect on the separation efficiency. Small holes and a smooth surface of the screen basket were also important to improve the separation efficiency. It was shown that, when used as a strength agent in a CTMP pulp, the fine fraction of highly refined kraft pulp was twice as efficient as the highly refined kraft pulp, when added at equal mass proportion. However, both in the lab and pilot trial the strength increase was accompanied by a decreased bulk. This was expected, and to avoid this the proportion of the bulky CTMP had to be increased. The pilot paper machine trial with an increased CTMP proportion in the middle ply and a fine fraction of refined kraft pulp as strength agent demonstrated that it was possible to produce sheets with an increased bulk and maintained z-strength.
Böjstyvheten är en viktig egenskap för alla sorters hårda förpackningar. I flerskiktskartong får man böjstyvhet genom att ha ytterskikt med hög dragstyvhet tillverkade av fibrer från kemisk massa och ett mittskikt med hög bulk från styva fibrer, ofta med en stor andel CTMP (kemitermomekanisk massa). CTMP-fibrer är styva men ger lägre styrka i arket. För att öka styrkan i mittskiktet tillsätter man utskott (kasserad kartong) som delvis innehåller kemisk massa, och ibland även ren högmald kemisk massa. Både fibrer och finmaterial (fines) har stor betydelse för slutproduktens egenskaper. Fines som skapas vid malning av kemisk massa är särskilt effektiva för att öka styrkan. Genom att fraktionera massa med en mikroperforerad sil kan man få en finfraktion med högt finesinnehåll. Mikroperforerade silar är effektiva för längdfraktionering av massa; fines anrikas i den fraktionen som passerar silen medan långa fibrer stannar i den andra fraktionen. Genom att använda en sådan finfraktion i mittskiktet kan man få tillräcklig styrka och samtidigt behålla mer av bulken från CTMP:n genom att man inte behöver mala den för att få styrka. En nackdel är att finfraktionen vanligtvis har väldigt låg masskoncentration eftersom mycket vatten passerar silen tillsammans med fines och fiberfragment. Detta extra vatten måste tas bort för att vattenbalansen i papperstillverkningsprocessen ska bibehållas. Dessutom kräver den större volymen ökad pumpkapacitet. För att kunna använda en finfraktion industriellt behövs en effektiv produktion med hög koncentration och högt finesinnehåll. Fokus i det här arbetet lades på separationseffektivitet (skillnaden i fiberlängdsfördelning som resultat av silningen) och processeffektivitet (koncentrationen i finfraktionen) för tillverkning av en finfraktion av kemisk massa genom silning samt dess utnyttjande som styrkehöjande tillsats i ett mittskikt av kartong. För att utvärdera hur separationseffektiviteten och processeffektiviteten påverkas av parametrar som koncentrationen i flödet in till silen, typ av kemisk massa (gjord av lövved eller barrved), hålstorlek i silen samt malningen av massan, gjordes fraktioneringsförsök i pilotskala med en trycksil med olika mikroperforerade silkorgar. Resultatet av fraktioneringen utvärderades med hjälp av fiberlängdsfördelningar, flöden och koncentrationer i flödet till silen och de två fraktionerna efter silen. För utvärderingen togs två olika utvärderingsmetoder fram: Proportion i finfraktionen (för processeffektivitet) och Finfraktionsanrikning (för x separationseffektivitet). För att utvärdera hur effektiv en finfraktion av kemisk massa var som styrkeadditiv i ett CTMP-ark gjordes labbförsök där tillsats av högmald kemisk massa jämfördes med tillsats av enbart en finfraktion av den högmalda kemiska massan. Resultaten verifierades med ett försök på en pilotpappersmaskin. I ett följande försök på pilotpappersmaskinen tillverkades ark med ökat CTMP-innehåll för att öka bulken, och med en tillsats av en finfraktion av kemisk massa som styrkeadditiv. När det gäller processeffektivitet var hög koncentration i flödet till silen den viktigaste parametern för att få hög koncentration på finfraktionen. Detta var också positivt för separationseffektiviteten, färre av de längre partiklarna hamnade i finfraktionen. Vidare blev finfraktionens koncentration högre för lövvedsmassa. En finfraktion som ska användas som styrkeadditiv ska vara tillverkad av mald massa, malning av massan var också fördelaktigt för finfraktionens koncentration. Små hål och en slät yta på silkorgen var också positivt för separationseffektiviteten. Som styrkeadditiv i CTMP var finfraktionen av högmald kemisk massa dubbelt så effektiv som den högmalda kemiska massan vid lika stor tillsats. Men i både labbförsök och pilotförsök minskade bulken när styrkan ökade. Det var väntat eftersom att ersätta en del av originalmassan som har hög bulk, med en finfraktion eller högmald massa, som båda har mycket lägre bulk, alltid minskar bulken på arket. För att undvika en bulkförlust måste massasammansättningen i arket ändras. Försöket på pilotpappersmaskinen med ökat CTMP innehåll och en finfraktion av mald kemisk massa som styrkeadditiv visade att det är möjligt att tillverka ett ark med högre bulk och bibehållen styrka.

Paper-based materials, such as paperboard, are commonly used as packaging materials. Inaddition to the advantage that wood as a raw material is renewable, there are also many otherbenefits of paperboard. From a mechanical point of view, paperboard has a high bendingstiffness compared to its relatively low weight and has a high foldability, which both areproperties of significance in the design of packages. However, a distinct drawback withpaperboard is its significant sensitivity to moisture. The moisture reduces the mechanicalproperties of the paperboard and consequently reduces the performance of the package. Thisthesis is starting with an investigation of the relation between moisture and differentmechanical properties on a continuum material level, and then these relations are applied onthe packaging design level through experimental testing and simulations. In Paper A, a material characterization was performed on a series of five paperboards withdifferent grammages from the same producer. Five types of mechanical tests to characterizethe paperboards’ material properties were performed: • In-plane tensile test, • Out-of-plane tensile test, • Short-span Compression Test (SCT), • Bending stiffness test, • Double-notch shear test. All tests were performed at several levels of relative humidity (RH). Linear relations betweenthe mechanical properties normalized with their respective value at 50 % RH and moistureratio were found. Paper B examined whether the linear relationships discovered in Paper A are true also forother paperboard series as well. Therefore, 15 paperboards from four producers wereinvestigated in this study, at the same levels of RH as before. Here, the in-plane stiffnessesand strengths and SCT-values were evaluated as a function of moisture. When also themoisture ratios in the investigated paperboards were normalized, it turned out that allpaperboards followed the same linear relationship between normalized mechanical propertyand normalized moisture ratio. Additionally, a bilinear elastic-plastic in-plane model wasdeveloped, that can predict the stress-strain relation of an arbitrary paperboard at an arbitrarymoisture level, and without requiring any mechanical testing except at standard condition(50% RH, 23 °C). In Paper C, this relation was used to estimate input material parameters for simulating a BoxCompression Test (BCT) at different moisture levels. The result showed that it was possibleto accurately predict the load-compression curve of a BCT when moisture was accountedfor.
Som förpackningsmaterial betraktat är pappersbaserade material, som exempelvis kartong,väldigt intressanta material. Utöver att råvaran trä är förnyelsebar finns även många andrafördelar med kartong. Ur ett mekaniskt perspektiv är kartong exempelvis väldigt styv iförhållande till sin vikt och har generellt väldigt hög vikbarhet, vilket båda är egenskaper somlämpar sig väl för en förpackning. En klar nackdel med kartong är dess känslighet för fukt.Fukten reducerar kartongens mekaniska egenskaper, vilket följaktligen leder till attförpackningens prestanda försämras. I den här licentiatavhandlingen undersöktes initialtsambanden mellan fukt och mekaniska egenskaper på materialnivå, för att sedan överförasambanden till förpackningsnivå genom experimentell provning och simuleringar. I Artikel A utfördes en materialkaraktärisering på en kartongserie innehållande femkartonger med varierande ytvikter från samma tillverkare. Fem typer av mekaniska provgenomfördes för att karaktärisera kartongernas respektive materialegenskaper: • Dragprov (i planet), • Dragprov (ut ur planet), • Korta kompressionsprov (SCT), • Böjstyvhetsprov, • Skjuvprofilsprov. Samtliga prov utfördes vid flera olika nivåer av relativ fuktighet (RH). Linjära relationermellan mekanisk egenskap normerad med motsvarande värde vid 50 % RH och fuktnoterades. I Artikel B undersöktes huruvida de linjära sambanden som upptäcktes i Artikel A stämmeräven för andra kartongserier. 15 kartonger från fyra producenter undersöktes därför i dennastudie vid samma fukthalter som tidigare. I den här studien undersöktes endast dragprov iplanet, samt SCT. När även fuktkvoterna i de undersökta kartongerna normerades visade detsig att alla kartonger följde samma linjära relation mellan normerad mekanisk egenskap ochnormerat fuktinnehåll. Utöver detta utvecklades en bilinjär elastisk-plastisk i-planet-modellsom kan prediktera en godtycklig kartongs spännings-töjningsförhållande för godtyckligfuktnivå, utan att någon mekanisk provning utöver standardklimat (50 % RH, 23 °C) behöver genomföras. I Artikel C utnyttjades det linjära sambandet mellan mekanisk egenskap och fuktkvot genomatt prediktera de ingående materialegenskaperna som användes vid simuleringar avboxkompressionsprovning vid olika fuktnivåer. Simuleringarna jämfördes med experimentellprovning och visade sig kunna prediktera experimentella resultat vid olika fukthalter bra.

AbstractWANG, YUN YENG. Constitutive Modeling of the Unloading Behavior of Paper Material Using the Asymptotic Fiber and Bond Model. (Under the direction of Dr. M. K. Ramasubramanian)Current constitutive models for paper and paperboard material are focused on the prediction of the sheet stress-strain behavior during loading. The unloading process has not been widely addressed. This work will focus on modeling the unloading behavior of paper material in one- and two-dimensional problems. For the one-dimensional problem, i.e. uniaxial tensile test, the asymptotic fiber and bond model by Sinha (1994) is extended to determine the plastic (permanent strain) of a sample upon unloading. In Sinha's micromechanics model, a representative load bearing, i.e. fiber at a fiber-to-fiber bond site, was used to derive the fiber stress and subsequently the sheet stress. In the asymptotic fiber and bond model, the fiber and bond condition (of elasticity or plasticity) was assumed to be the same throughout the fiber. In this work, the fiber and bond begins in elastic state. As the applied load or strains increase, the bond yields, while fiber remains elastic throughout the loading process. When unloading, both fiber and bond behave elastically. The model parameters for the asymptotic fiber and bond are obtained by fitting the model to experimental data from uniaxial stress-strain curves. The unloading model is then used to predict the plastic strain after unloading of uniaxially strained samples. The model prediction corresponds well with the experimental data. For a two-dimensional problem, a sample was deformed in a Mullen burst tester and then unloaded. A Mullen tester is used to conduct burst test by applying a uniform pressure to one surface of the sample that is clamped down on the pressure chamber. In a burst test, the sample deforms into hemispherical shape and eventually fails with a 'H' pattern in the center. For testing the unloading model, the sample is deformed to a given pressure and unloaded. The central displacement of the sample throughout the loading and unloading process is recorded together with the applied pressure, for comparison with model predictions. Since the asymptotic fiber and bond model has limited application in one-dimensional problems, a combination of continuum and micromechanics methods was used by Sinha and Perkins (1995) to reap the benefits the two types of approach have to offer. The hybrid model was applied in finite element analysis using the finite element analysis code ABAQUS and its user subroutine UMAT. A similar approach was utilized in this work to model the unloading process in two-dimensional problems.

Papper uppvisar betydande tidsberoende mekaniska egenskaper som krypning och spänningsrelaxation. Det är känt att krypningen hos pappret påverkar till exempel en wellpapplådas förmåga att bära last under lång tid. En möjlighet att tillverka papper som kryper långsammare är därför önskvärd. Polyelektrolyter används ofta för att öka styrkan hos papper, och skulle kanske också kunna användas till att minska papprets krypning. Inverkan av polymera additiv på pappers krypegenskaper är emellertid knapphändigt beskrivet i litteraturen. Existerande studier har visat att polymera additiv inte påverkar krypningen hos starka papper och att fiberväggarna och fiber/fiber fogarna har fundamentalt olika betydelse för krypegenskaperna.

Avsikten med denna avhandling var att undersöka hur adsorberade polyelektrolyter påverkar krypegenskaperna hos pappret. Ett av huvudsyftena var att studera om adsorptionen av en katjonisk polyelektrolyt – polyallylamin – endast till fiberytan eller tvärs hela fiberväggen ger olika effekt på krypningen hos papper tillverkade av dessa fibrer.

En ny teknik där polyelektrolyten märks med en fluorescerande markör gör det möjligt att visualisera var i fibern de adsorberade molekylerna befinner sig. Resultaten visar att adsorption vid låg jonstyrka under kort tid bara ger adsorption till de yttre delarna av fiberväggen. Hög jonstyrka och lång adsorptions tid resulterar å andra sidan i adsorption tvärs hela fiberväggen. Med hjälp av denna teknik blev det också möjligt att klarlägga vilken inverkan polyelektrolytens läge i fiberväggen har på de slutgiltiga arkens mekaniska egenskaper.

Krypprovning av de tillverkade arken visade tydligt att polyallylamin som endast adsorberat till fibrernas yttre delar minskade krypningen vid både 50 % och 90 % relativ luftfuktighet. Den uppnådda effekten visade sig dock bero på vilken typ av fibrer arken tillverkades av. Adsorption av katjoniserad stärkelse till fibrernas yta gav ingen nämnvärd effekt på arkens krypegenskaper, detta trots att stärkelse gav lika hög arkstyrka som polyallylamin.

När polyallylamin adsorberades tvärs igenom fibrerväggen ökade krypningen vid 90 % relativ luftfuktighet väsentligt. Detta föreslås bero på att den adsorberade polyelektrolyten avsväller fibrerna vilket ger färre fiber/fiber kontakter och därmed en sämre fördelning av mekanisk last i arken. Det var emellertid inte möjligt att dra några definitiva slutsatser angående mekanismerna bakom de observerade skillnaderna i krypegenskaper.

Paper materials exhibit a significant time-dependent mechanical behaviour, such as creep and stress-relaxation. It is known that the creep of the paper affects the performance of corrugated boxes. The production of a paper having a lower creep rate is therefore desirable. Polyelectrolytes commonly used to increase the strength of paper could be an alternative for improving the creep properties. The influence of polymeric additives on the creep properties of paper is, however, poorly described in the literature. Published studies have shown that polymeric additives do not affect the creep behaviour of fully efficiently loaded paper sheets and that the fibre cell walls and the fibre/fibre joints have fundamentally different effects on the creep behaviour.

The aim of the present thesis was to examine the influence of adsorbed polyelectrolytes on the creep behaviour of paper sheets made from the modified fibres. One of the main objectives was to establish whether there is a difference in effect on creep properties between adsorbing a cationic polyelectrolyte – polyallylamine – to the fibre surfaces or throughout the fibre cell walls.

A technique which includes the labelling of polyelectrolytes with a fluorescent dye and microscopy of single fibres provided a visual record of the localisation of the adsorbed polyelectrolyte. This method showed that a low ionic strength and a short adsorption time resulted in adsorption of the polyelectrolyte only to the external parts of the fibres. A high ionic strength and a long adsorption time on the other hand, resulted in adsorption throughout the fibre walls. This made it possible to study the relationship between the mechanical properties of the sheets and the localisation of the adsorbed polyelectrolyte.

Creep testing of the sheets showed that the adsorption of polyallylamine to the exterior parts of fibres decreased the creep at both 50% and 90% RH. The effect depended, however, on the type of fibre used. Adsorption of cationic starch to the fibres gave no significant reduction in creep rate, despite the fact that starch and polyallylamine had similar effect on the paper strength.

When polyallylamine was adsorbed into the fibre cell walls, the creep at 90% RH increased. It is suggested that this was due to a deswelling of the fibres by the adsorbed polyelectrolyte, which resulted in fewer fibre/fibre contact points and hence a less efficient distribution of stresses in the sheet. It was not, however, possible to draw any definitive conclusions about the mechanisms behind the observed differences in creep behaviour.

Today, a huge part of waste products from pulp and paper industries ends up in landfill which is both economically and environmentally adversely. This report examines the possibilities of using those products as a slag foamer and fuel in different furnaces in the metal industry. The waste products contain valuable elements, especially carbon. Therefore, there is an increased interest in finding possible use for the waste products in the metal industry. The reuse would contribute to preservation of energy as fossil fuel can be replaced. In the report, two waste materials called mixed biosludge and fiber reject are examined. The experiments are performed with the waste products pressed together with a base material and cement forming a briquette. The requirements examined are strength needed for both transportation and use in furnaces and ability to create a foaming slag. The results in strength were ambiguous, no waste material based briquettes met the set criteria. As of now, the briquettes are probably not strong enough to be transported. No foaming occurred during the experiment, but only one experiment was performed. Therefore, further experiments are needed before any conclusions can be drawn. The briquettes can possibly replace coke and coal in applications where strength is not as important. Nevertheless, it is uncertain if the briquettes affect the steel quality.
Idag läggs en stor del av restprodukter från pappers och massaindustrin på deponi, vilket innebär såväl ekonomiska som miljömässiga nackdelar. Den här rapporten undersöker möjligheterna att använda dessa restprodukter som slaggskummare och bränsle i de olika ugnarna inom metallindustrin. Restprodukterna innehåller värdefulla ämnen, framförallt kol. Därför finns det ett ökat intresse för att hitta möjliga användningsområden för restprodukterna inom metallindustrin. Denna återanvändning skulle bidra till energibevarande eftersom fossila bränslen kan ersättas. I den här rapporten undersöks två restmaterial, blandat biologiskt slam och fiberavfall. Experimenten utfördes med dessa restprodukter pressade samman med ett basmaterial och cement till en brikett. Kraven som undersöks är styrka för både transport och användning i ugnarna samt förmågan att skumma en slagg. Resultaten för briketternas styrka var tvetydiga, inga av briketterna innehållande restprodukter satisfierade det uppsatta kriteriet. Styrkan är troligtvis för låg för att transport ska vara möjlig. Ingen skumning skedde under experimentet, men endast ett experiment genomfördes. Därför behöver ytterligare experiment genomföras innan några slutsatser kan dras. Men briketterna tros kunna ersätta koks och kol där styrkan inte är viktig. Men det är osäkert om briketterna påverkar stålkvaliteten.

This thesis explores how to use the dry nanoporous structure of cellulosic fibres in new types of composite materials. A large effort was also given on how to correctly characterize the structure of fibres where the wet structure has been preserved also in the dry state. Delignified wood fibres have an open fibrillar structure in their water-swollen state. In the present work, this open fibrillar structure was preserved in the dry state by performing a liquid exchange procedure and the samples were thereafter carefully dried with Ar(g). The samples of never-dried TEMPO-oxidized dissolving pulp had a specific surface area of 130 m2/g in the dry state, as measured using the Brunauer, Emmet, and Teller (BET) Nitrogen gas adsorption method. This open structure was also revealed using field emission scanning electron microscopy (FE-SEM). The water-swollen and dry open structures were thoroughly characterized for various pulps. A new method for determining the pore size of water-swollen delignified cellulosic fibres is presented. By combining the results from solid state nuclear magnetic resonance NMR, measuring the specific surface area [m2/g] in the water-swollen state, with fibre saturation point (FSP), measuring the pore volume of fibres in water-swollen state [mass water/mass fibre], the average pore size can be determined without the need of assuming a certain pore geometry. The dry nanoporous structure was then used as a scaffold for in-situ polymerization, to demonstrate how the properties of the fibrils in the fibre wall can be exploited without the need to disintegrate the fibre wall. Both poly(methylmethacrylate) (PMMA) and poly(butylacrylate) (PBA) were successfully used as the polymeric matrix, and both nanocomposites (i.e., fibre/PMMA and fibre/PBA) had a fibre content of approximately 20 w%. The structure of the composites was characterized using SEM and Atomic Force Microscopy (AFM) operated in the phase imaging mode. The AFM results indicate that the cellulose aggregates and polymeric matrix were successfully mixed on a nanoscale, creating a nanocomposite of interpenetrating polymer molecules and cellulose fibrils, rather than a microcomposite, when using microscopic cellulose fibres. The water absorption capacity of the nanocomposites was reduced significantly, indicating that almost all nanopores in the fibre wall were successfully filled with matrix polymer. The mechanical properties were investigated, showing the importance of nanosized reinforcement compared to fibres of micrometer size.

QC 20121011

Turbulent mixing is present in many pulp and paper processes. It is a particularly important factor in the design and improvements of the paper machine headbox, influencing the final paper structure. During this project, experimental methods to quantify the effect of fibers on turbulent suspension flows have been developed, and then used for studying turbulent mixing in fiber suspensions. A technique that uses microprobes to measure passive scalar mixing of salt for the characterization of turbulent fluctuations in a fiber suspension flow has been developed: Conductivity micro-probes have been built and turbulence measurements have been performed in simple jet and wake flows, studying turbulent mixing between the two streams of pulp suspension, of which one has been doped with salt. A relatively new technique to measure fluid velocity non-intrusively in opaque fluids has also been tested. The technique makes use of ultrasonic pulses to obtain velocity information through the Doppler-shift of reflected pulses. The main efforts reported on in the thesis are focused on method design and development as well as method evaluation.

En réponse à une forte croissance démographique mondiale, et notamment africaine, il est nécessaire d’anticiper les besoins de la population en terme de bâtiment. Il s’agit alors de développer des matériaux alternatifs présentant des performances multi-physiques adéquates tout en ayant un faible impact sur l’environnement. Ce travail porte sur l’élaboration et la caractérisation de composites utilisables comme produits constructifs de partition (cloison, faux plafonds). La sélection des matières premières intègre des critères de développement durable, en considérant leur disponibilité locale mais également leur empreinte en terme d’épuisement des ressources (matériaux recyclés ou bio-sourcés). Les liants utilisés sont le plâtre, l’amidon de pomme de terre et l’amidon de manioc. Les charges sont la fibre de bois, la ouate de cellulose et les granules de papiers, pour une valorisation originale en matériau de construction. Les performances des composites développés sont évaluées d’un point de vue mécanique, hygrique, thermique et en terme de résistance au feu. Ces travaux ont montré la faisabilité et l’intérêt de tels composites. Ceux-ci peuvent notamment être utilisés pour leur qualité de régulateur hygrique et de correcteur thermique
Due to strong global population growth, and particularly African, the population’s needs in terms of building have to be anticipated. The aim is to develop alternative materials with adequate multiphysical performances and low impact on the environment. This work investigates the elaboration and characterization of composites to be used as constructive partition products (partitions, false ceilings). The selection of raw materials takes into account sustainable development criteria, considering both the local availability of materials and their footprint in terms of resource depletion (recycled or bio-sourced materials). The binders used are plaster, potato starch and cassava starch. The loads are wood fiber, cellulose wadding and paper granules, for an original valorisation in building material. The performances of the developed composites are evaluated from a mechanical, hygric, thermal and fire resistance point of view. This work has shown the feasibility and the interest of such composites. These can in particular be used for their quality of hygric regulator and thermal corrector

The influence of turbulence on the orientation state of a dilute suspension of stiff fibers at high Reynolds number in a planar contraction is investigated. High speed imaging and LDV techniques are used to quantify fiber orientation distribution and turbulent characteristics. A nearly homogenous, isotropic grid generated turbulent flow is introduced at the contraction inlet. Flow Reynolds number and inlet turbulent characteristics are varied in order to determine their effects on orientation distribution. The orientation anisotropy is shown to be accurately modelled by a Fokker-Planck type equation. Results show that rotational diffusion is highly influenced by inlet turbulent characteristics and decays exponentially with convergence ratio. Furthermore, the effect of turbulent energy production in the contraction is shown to be negligible. Also, the results show that the flow Reynolds number has negligible effect on the development of orientation anisotropy, and the influence of turbulence on fiber rotation is negligible for $mathrm{Pe_r}>$ 10. It was concluded that inertia induced fiber motion played a negligible role in the experiments.

There is an in-between space during the act of seeing. The in-between space lies on the spectrum of the reality in front of us and what our brain tells us. It is within this suspended moment an individual can experience an unaltered and unaffected vision. While this moment is fleeting, it defines the highest peak of personal experience. It is my belief no two people will ever experience the same vision during this suspended time. And after it passes, the sigh/vision can never be the same. We are constantly bearing witness to the inexpressive, and this fleeting moment is something in which we should all revel.

While there is a substantial amount of information regarding the electrochemical behavior of fuel cells and there components little to no information is available regarding the mechanical properties of fuel cell materials in stack setups. This set of experiments was set up to test mechanical properties of gas diffusion layer and bipolar plate materials in a one cell setup. Samples were clamped to specified pressures and deformation properties were observed and measured. Measurements were taken of impingements of the gas diffusion layers into the gas flow channels. A limit for compression of cell configurations was found to be approximately 300psi. Upon reaching the compression limit bipolar plates collapse and materials between plates show signs of breakage. Under compression diffusion media showed impingement into the gas flow channels as well as substantial compression of the three layer stack.