<p>The chemical interactions between the main wood components i.e., cellulose, hemicelluloses and lignin are of fundamental importance for understanding the chemical aspects of wood formation and its reactivity during fibre processing e.g during chemical pulping of wood. Future progress in the development of new high value products from wood will greatly depend on a detailed knowledge of how the fibre elements interact with each other in the biological material. The existence of covalent bonds between lignin and carbohydrates (LCC) has been one of the most controversial issues in the field of wood chemistry. Only until recently, the existence of such bonds has in its entirety been shown by way of indirect analyses, normally suffering from low yields obtained at rather drastic conditions. Furthermore, previous studies on LCC have been targeted on studying the specific lignin carbohydrate linkage and less emphasis has been put on the whole LCC networks. Detailed structural studies of entire LCC are therefore of importance in understanding the chemistry involved in wood formation and wood reactivity.</p><p>The aim of this study was to isolate intact LCC from wood and corresponding chemical pulps made from it in quantitative yield and to clarify their detailed chemical structure. For the first time, a method for the quantitative analysis of lignin-carbohydrate complexes (LCCs) in softwood is presented and it could be concluded that no carbohydrate-free lignin was present in these wood fibres. From mildly ball-milled wood, all lignin was isolated as LCCs in a sequence involving a partial enzymatic hydrolysis of cellulose, subsequent swelling and quantitative dissolution, into 4 major fractions; a galactoglucomannan-lignin-pectin LCC (GalGlcMan-L-P) containing ~8% of the wood lignin, a glucane LCC (Glc-L) containing ~4% of the wood lignin, a xylan-lignin-glucomannan network LCC (Xyl-L-GlcMan) (with a predominance of xylan over glucomannan) containing ~40% of the wood and a glucomannan-lignin-xylan network LCC (GlcMan-L-Xyl) (with a predominance of glucomannan over xylan) containing ~48% of the wood lignin.</p><p>From unbleached kraft pulps, 85 - 90% of residual lignin was found to be chemically bonded to carbohydrates. The effect of the degree of delignification on the LCC types during kraft pulping and during subsequent oxygen stage was studied in order to understand the role of LCC for the stability of residual lignin. For both processes, high delignification rates were observed for the xylan-rich LCC and cellulose-rich LCC fractions, whereas the glucomannan-rich LCC was relatively stable. After a severe oxygen stage, almost all the residual lignin was isolated in the latter complex.</p><p>Thioacidolysis in combination with gas chromatography was used to determine the content of β-O-4 structures in the lignin. Periodate oxidation and methanol determinations were used to quantify the phenolic hydroxyl groups, whereas size exclusion chromatography (SEC) of the thioacidolysis fractions was used to monitor any differences between the original molecular size distribution and that after the delignification processes. Major differences between the various LCC fractions were observed, clearly indicating that two different forms of lignin are present in the wood fibre wall. These forms are linked to glucomannan and xylan respectively. The xylan linked lignin was found to consist largely of β-O-4 structures indicating a rather linear coupling mode, whereas the glucomannan linked lignin was more heterogeneous with respect to the known lignin inter-unit linkage types. Based on these findings, a modified arrangement of the fibre wall polymers is suggested. From acid sulfite pulp (Kappa number 11) residual lignin was isolated at ~80% yield on LCC basis. About 60% was linked to xylan, 30% to glucomannan and 10% to glucans. These values differ greatly from those obtained for softwood pulped to a similar kappa number by the Kraft method. Model compound studies indicated that the benzyl ether type of LC linkage were likely to survive cleavage at the acidic sulfite pulping conditions</p>

<p>This thesis deals with the wetting by oil mixtures of two different model cellulose surfaces. The surfaces studied were a regenerated cellulose (RG) surface prepared by spin-coating, and a film consisting of polyelectrolyte multilayers (PEM) of Poly(ethyleneimine) (PEI) and a carboxymethylated Microfibrillated Cellulose (MFC). After coating or covalently modifying the cellulose surfaces with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of the different oil mixtures. The viscosity and surface tension of the oil, as well as the dispersive surface energy of the cellulose surface, are essential parameters governing the spreading kinetics. X-ray Photoelectron Spectroscopy (XPS) and dispersive surface energy measurements were made on the cellulose films treated with fluorosurfactants. A strong correlation between the surface coverage of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures was found. For example, a dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (θ_e > 90º) by castor oil.</p><p>Significant parts of this work were devoted to the development of cellulose surfaces for the wetting studies. The formation of a PEM consisting of PEI and MFC was studied and the total layer thickness and adsorbed amount were optimized by combining Dual Polarization Interferometry (DPI) with a Quartz Crystal Microbalance with Dissipation (QCM-D). The adsorption behaviour as well as the influence of the charge density, pH and electrolyte concentration of PEI, and electrolyte concentration of the MFC dispersion on the adsorbed amount of MFC were investigated. Results indicate that a combination of a high pH, a fairly high electrolyte concentration for PEI solution together with low or zero electrolyte concentration for the MFC resulted in the largest possible adsorbed amounts of the individual PEI and MFC layers.</p><p>The structures of the two cellulose surfaces were characterised with atomic force microscopy measurements and a difference in terms of surface structure and roughness were observed. Both surfaces were however very smooth with calculated RMS roughness values in the range of a few nanometers.</p><p>The adsorption behaviour of water-dispersible fluorosurfactants physically adsorbed at various concentrations onto the two model cellulose surfaces was investigated using DPI. The aggregate structure of an anionic fluorosurfactant, perfluorooctadecanoic acid, dispersed in water was studied by Cryo Transmission Electron Microscopy (Cryo-TEM). The fluorosurfactants had an adsorption and desorption behaviour in water which was dependent on the fluorinated chain length and the aggregation form of the fluorosurfactant. Perfluorooctanoic acid and a commercial cationic fluorosurfactant with a formal composition of CF₃(CF₂)_nSO₂NH(CH₂)₃-4N(CH₃)₃⁺I^-was found to desorb from the MFC and RG surfaces upon rinsing with water, whereas perfluorooctadecanoic acid was strongly adsorbed to the surfaces. It is essential for a fluorosurfacatant to be strongly adsorbed to the cellulose surface even after rinsing to yield hydrophobic and lipophobic (oleophobic) properties with a large contact angle for oils and water.</p>

<p>Papper är ett mycket mångsidigt material. Trots detta finns det ett flertal egenskaper som begränsar papperets användbarhet. Ett av de större problemen med cellulosa- och lignocellulosafibrer är att de sänker sin fria energi genom att sorbera vatten, och denna sorption förändrar papperets dimensioner. Detta fenomen kallas vanligtvis för bristfällig dimensionsstabilitet och uppträder i form av registerfel vid flerfärgstryck eller som krullning, buckling och vågiga papperskanter vid utskrift, kopiering och lagring, eller med en vidare definition som förkortad livslängd hos lådor på grund av mekanosorptivt kryp.</p><p>Avsikten med denna avhandling har varit att studera och kvantifiera vilka egenskaper som styr, och hur de påverkar, den vatteninducerade dimensionsförändringen som sker hos ett fibernätverk, samt hur dess dimensionsstabilitet kan förbättras. Detta har studerats både genom att ändra fiberns fuktsorptionsegenskaper och genom att förändra adhesionen och kontaktgraden mellan fibrerna i fiber-fiberfogarna. Fogegenskaperna har också varierats genom att tillverka laboratorieark torkade under inspänning samt ark torkade fritt för att minimera mängden inbyggda spänningar i arket.</p><p>Blekt kraftmassa har behandlats med polyelektrolytmultilager (PEM) för att förbättra adhesionen mellan fibrerna och för att öka kontaktgraden mellan fibrerna i fogen. Kontaktgraden har även minskats genom förhorning av fibrerna före arkformning. För de ark som fick torka fritt gav PEM-behandlingen en ökad hygroexpansionskoefficient, det vill säga dimensionsförändringen normaliserad mot förändringen i fuktinnehåll, vid samma förändring i relativ luftfuktighet medan förhorningen minskade hygroexpansionskoefficienten något. Om arken emellertid torkades under inspänning observerades ingen skillnad i hygroexpansionskoefficient mellan de olika fibermodifieringarna. Detta tolkades som ett resultat av en ökad kontaktzon och en större utbredning ut ur fogens plan, när arken torkades utan inspänning. En utbredning som medför att en större del av fiberns transversella expansion överförs som expansion i pappersplanet.</p><p>Fibrernas fuktsorptionsegenskaper förändrades genom natriumperjodatoxidering av 1,4-glukanernas C2-C3-bindning. Detta skapade sannolikt tvärbindningar i fiberväggen som förbättrade fiberväggens tålighet både genom att låsa fibrillerna närmare varandra och genom att ta bort potentiella adsorptionssäten som annars är tillgängliga för vattenadsorption. Perjodatoxidationen minskar också fibrernas kristallinitet och således frigjorde oxidationen hydroxylgrupper där vattenmolekyler kan adsorbera. Detta innebar att oxidationen både minskade och ökade interaktionen mellan vatten och fibervägg, men dock på olika strukturell nivå. Tvärbindningarna visade sig också märkbart reducera sorptionshastigheten när arken utsattes för en förändrad luftfuktighet så länge de inte tidigare utsatts för relativa luftfuktigheter nära mättnad. Som ett resultat av den lägre förändringen i fuktinnehåll vid en förändring i luftfuktighet från 20 till 85 % RF minskade dimensionsförändringens amplitud för de tvärbundna arken upp till 30 %. Emellertid uppvisade de tvärbundna arken en högre hygroexpansionskoefficeint, vilket innebär att de blev mer känsliga för absoluta förändringar i fuktinnehåll.</p> / <p>Paper is a very versatile material. Nevertheless, there are several factors limiting its usefulness, and one of the major issues is that cellulosic and ligno-cellulosic fibres lower their free energy by sorbing water and this water changes the dimensions of the paper. This phenomenon is usually referred to as a lack of dimensional stability and is often evident as misregister during multicolour printing or curl, cockle and wavy edges during printing, copying and storage or, with a wider definition, also as a shortened life-time of boxes during storage due to mechano-sorptive creep.</p><p>The work described in this thesis aims to study and quantify the importance of the different mechanisms causing water-induced dimensional changes in a fibre network and to investigate how to improve the dimensional stability of ligno-cellulosic materials. This has been done both by altering the fiber properties such as the moisture sorptivity and by changing the adhesion and degree of contact within the fibre-fibre joints. The properties of the fibre-fibre joints have been varied by drying laboratory sheets both under restraint and freely to minimise the generation of built-in stresses.</p><p>Bleached kraft fibres were treated using the polyelectrolyte multilayer (PEM) technique to improve the adhesion between the fibres and to increase the molecular contact within the joints. In contrast, the degree of contact was impaired by hornifying the fibres before sheet preparation. For sheets allowed to dry freely, the PEM-treatment increased the hygroexpansion coefficient, i.e. the dimensional movement normalised with respect to the change in moisture content, when subjected to changes in relative humidity whereas the hornification process resulted in a slightly lowered hygroexpansion coefficient. However, when the sheets were dried under restraint, the different joint and fibre modifications led to no difference in hygroexpansion coefficient. This was interpreted as being a result of an increase in the total contact zone between the fibres when the sheets were dried under restraint, with a greater extension in the outof- plain direction of the joint resulting in a transfer of a larger part of the transverse swelling to the in-plane expansion.</p><p>The sorptivity of the fibres was changed by oxidising the C2-C3 bond of the 1,4- glucans with periodate. This most likely created covalent cross-links in the fibre wall both improved the integrity of the fibre wall by locking adjacent fibril lamellae to each other and also removed possible sites for water sorption onto the cellulose surfaces. Periodate oxidation also led to a decrease in the crystallinity of the cellulose within the fibres, making more cellulose hydroxyl groups available for the adsorption of water molecules. This means that the oxidation both decreased and increased the interaction between the fibre wall and moisture but, on two different structural levels. The crosslinks significantly reduced the sorption rate when the papers was subjected to changes in relative humidity, as long as the fibres were not subjected to humidities close to saturation. The smaller change in moisture content when the relative humidity was changed between 20 and 85 % RH meant that the dimensional stability of the crosslinked sheets was increased. On the other hand, the hygroexpansion coefficient was increased in the case of papers made from fibres with the highest degree of oxidation, i.e. the sheets became more sensitive to absolute changes in moisture content.</p>

<p>In this work, the formation of polyelectrolyte complexes (PECs) has been studied using a jet mixing method not previously used for mixing polyelectrolytes. The PECs were formed from two weak polyelectrolytes, i.e., polyacrylic acid (PAA) and polyallylamine hydrochloride (PAH), with different mixing times, and the results were compared with those for PECs formed using the conventional polyelectrolyte titration method.</p><p> </p><p>The adsorption behaviour of the formed PECs on silicon oxide substrates and pulp fibres was analysed, and the results were compared with those for polyelectrolyte multilayers (PEMs) prepared from the same two polyelectrolytes.</p><p> </p><p>The results indicated that by using the jet mixer, the size of the formed PECs could be controlled, which was not the case with the polyelectrolyte titration method. The PECs produced by jet mixing were also found to be smaller than those produced by polyelectrolyte titration. From these results, a two-step mechanism for the formation of PECs was suggested: initial precomplex formation, which is a fast and diffusion-controlled process, followed by a reconformation process, during which the vigorous mixing in the jet mixer can partially limit secondary aggregation.</p><p> </p><p>When the complexes were adsorbed to silicon oxide or pulp fibre surfaces, adsorption studies indicated that it was impossible to reach the same adsorption levels for PECs as for PEMs. This was explained in terms of free energy, entropical, reasons rather than to any geometric limitation of the surface. Despite the smaller amount of polyelectrolyte adsorbed from the PEC treatment than from the PEM treatment of pulp fibres, the PEC treatment had the greatest effect on paper strength per adsorbed amount of polymer. This was thought to be because the three-dimensional structure of the PECs, versus the smoother structure of PEMs, allows for the formation of multiple contact points between the macroscopically rough fibres and increased molecular contact area.</p><p> </p><p>In the adsorption experiments, it was also found that net cationic complexes can adsorb to both anionic and cationic substrates. This phenomenon was explained by the occurrence of anionic patches on the surface of the net cationic PECs and the ability of the PECs, formed from weak polyelectrolytes, to partially change charge upon exposure to a surface of the same charge as the complex itself, due to a change of the degree of dissociation of the polyelectrolytes constituting the complex.</p><p> </p>

No description available.

No description available.

<p>In recent years, antibacterial surfaces have been a subject of increased interest. Especiallyinteresting are non-leaching, contact-active surfaces that physically disrupts the bacterialcell using immobilised cationic polymers. Thus the risks of bacterial resistance and discharge of hazardous biocides is minimised. The assembly of such surfaces is elaborate andusually involves organic solvents. Here, polyelectrolyte multilayers (PEM) are proposed as an effective surface modification method, with an overall goal of producing antibacterial cellulose fibres. The PEM process is based on physical adsorption of oppositely charged polymers in aqueous solutions. Multilayers were formed with the bactericidal polymer polyvinylamine (PVAm) and polyacrylic acid. PVAm compounds with hydrophobic modificationswere applied as well, as they possess increased antibacterial activity in solution.</p><p>In this work, the multilayer formation was studied on model surfaces of silicone oxide and glass in order to obtain fundamental knowledge of the polymer system. QCM-D and reflectometry, which detect total mass including bound water and polymer mass only, respectively, were used to analyse the layer formation. Salt-concentrations were varied at 1, 10 or 100 mM NaCl. A stepwise multilayer formation with exponential-like polymer adsorption but with decreasing water content for each layer was seen at all salt concentrations.A higher salt concentration resulted in an increased adsorbed mass. No significant differences in adsorption between the modified and unmodified PVAm could be detected. AFM imaging applied to multilayers having nine layers showed large surface aggregates under high salt conditions for the C6-modified PVAm. Dynamic light scattering showed that the polymer occurred as single molecules in solution; hence it was concluded that theaggregation is surface-associated.</p><p>The multilayers were then tested for bacterial growth inhibition. The relative bacterial inhibition was time-dependent, as the surface was saturated with bacteria over time. After two hours, a maximal inhibition of 99 % could be observed for the multilayers. After eight hours, a moderate inhibition of less than 40 % was detected. Using multilayers affected the results positively compared to single layers. After three layers, though, no further reductionwas seen. Viability staining of the surface-adhered bacteria revealed that the adhered bacteria had intact membranes. Therefore, the microbiological properties of the multilayers can at this point be described more as growth-inhibiting by bacterial adhesion effectsthan as biocidal. However, this work has shown the importance of combining surface characterisation and microbial testing to understand the bacteria-surface interaction.</p> / Biointeractive fibres

Paper is a network material composed of a great number of fibers that interact with each other through fiber joints. In order to make a clear statement regarding observed changes being made in paper, it is vital to determine the structural level of paper that is being affected by chemical modifications. Polyelectrolytes having a wide range in molecular properties have been synthesized to investigate the adsorption behavior of cationic polyelectrolytes to cellulosic fibers. The interaction with the porous cell wall of cellulosic fibers is governed by the molecular properties of the polyelectrolyte. More specifically, polyelectrolytes having a low charge density are able to penetrate into the fiber cell wall, while high charge density polyelectrolytes are restricted to the exterior fiber surface. The molecular mass also influences the extent to which adsorption occurs within the cell wall, although this is typically only pronounced for low charge density polyelectrolytes. High charge density polyelectrolytes are generally restricted to the fiber surface due to strong Coulombic interactions between charged groups along the molecular backbone, which create a stiff molecular conformation. These results were confirmed by fluorescent labeling techniques, which allow the polyelectrolytes to be tracked inside the cell wall by confocal laser scanning microscopy. This approach was also used to demonstrate the effect of an electrolyte, which screens the Coulombic interactions and facilitates penetration into the cell wall. However, a considerable difference in the adsorption behavior of polyelectrolytes having similar molecular mass is still observed at high electrolyte concentration, where the electrostatic contributions are negligible. These differences are a consequence of a diffusion process that occurs on a longer times scale. Although polyelectrolyte adsorption to cellulosic fibers reaches a pseudo-equilibrium at short times, a driving force into the cell wall exists due to the bulk charge of the fiber. The time scale of this diffusion process depends on the polyelectrolyte properties, and was observed to persist for over 3 months. As the extent to which these polyelectrolytes penetrate into the cell wall has been ascertained, and the fibers can be crosslinked to different degrees in the cell wall or at the surface. Cationic acetal dextran was prepared as a model crosslinking agent, as the molecular mass, charge density and degree of acetal substitution can readily be controlled during synthesis. A considerable effect on the tensile properties and fracture toughness was observed for crosslinked paper, which could be attributed to either the fibers or the fiber joints. Crosslinking acted to stiffen the fibers and the fiber joints, which influenced the transfer of applied stresses through the paper structure. Changes in the material behavior at high relative humidity could be improved by crosslinking the fibers at the correct the structural level. / QC 20100811

Pulp- and papermills expend vast amounts of water in order to produce pulp, paper and cardboard. Hence, they alsocreate vast amounts of waste water which has to be cleaned before it can be released into the receiving body of water. Insuch a wastewater treatment plant, tremendous amounts of energy are expended by the aeration in the biologicalcleaning process. This aeration is necessary to supply the microorganisms that shall decompose organic material withoxygen, which they need for their metabolism. The transfer of oxygen from the gas phase to the liquid phase isprimarily inhibited by surface-active substances in the waste water like resin acids or fatty acids. The purpose of thisthesis has been to determine if the surface-active substances can be removed by means of chemical pre-precipitationbefore the waste water enters the biological cleaning step. Thus, the efficiency of the aeration shall be improved.In the laboratory, aeration tests were performed for plain water, water with added surface-active substances and CTMPwastewaterfrom Stora Enso Skoghalls Bruk. The test for water with added surface-active substances showed clearlythat these substances have a big influence on the aeration efficiency, which was impaired considerably compared withplain water.In order to determine how chemical precipitation influences the content of surface-active substances, screening trialswere performed with the CTMP waste water. The concentration of surface-active substances was estimated bymeasuring the surface tension of the waste water. The surface tension sinks with increasing concentration of thesesubstances. 250 ml CTMP-wastewater was precipitated with three different chemicals: PAX-XL60, PGA and AVR. Inorder to determine the optimal dosing as well as the optimal pH-value for goal-oriented precipitation of the surfaceactivesubstances, the precipitation was performed with different pH-values between 4 and 8 as well as for differentdoses of the precipitation chemicals. It was discovered that the optimal pH-value for precipitation with PAX-XL60 is7,5 while the precipitation with PGA had the optimal pH-value of 6. The optimal dosage for PAX-XL60 was 10 g/cm3,while the optimal dosage for PGA could not be determined because of the small waste water volume used in thescreening trials. The screening trials showed that the surface tension increased after precipitation with both PAX-XL60and PGA which leads to the assessment that the concentration of surface-active substances has decreased.Precipiation- and aeration trials in big lab-scale were performed at pH 7,5 and the optimal dosage of PAX-XL60. ForPGA, the precipitation and aeration trials were performed at pH 6 and the lowest dosage of the screening trials. Theaeration trials showed that precipitated CTMP-wastewater could be aerated more energy efficient than the samewastewater without precipitation.Calculations showed that energy costs can be reduced by nearly 90% by using the tested precipitation chemical PAXXL60respectively nearly 65% by using the tested precipitation chemical PGA according to the lab-scale trials. Thecosts for the chemicals are not included.

This thesis will show the possibility for the development and use of an on-line model for application to continuous digesters for pulp production. The model is developed by using a program called Dymola (Dynamic Modeling Laboratory). What makes the Dymola software so well suited is that the program solves equations simultaneously. The model is a further development from the Purdue model [Bhartiya et al, 2003]. The main difference between this model and the Purdue model however, is the dynamics in the model. The dynamics are very important when you use the model for control purposes because the cooking process has long dead and retention times. The main purpose of this model is to use it for the advanced control of continuous digesters as well as giving the operators a better understanding of what happens in the cooking process when changes are made. The model will also be used for diagnostic purposes. Advanced control in this case is Model Predicted Control (MPC). The MPC will control the quality of the pulp “kappa” number and the chemical consumption during digestion. This thesis describes the model and results are shown for applications of on-line diagnosis in three pulp mills in South Africa. Real time process data from the pulp mills is fed into the model and a simulation is performed. Thereafter, the results from the simulation are compared to the actual measured data for a number of key variables. By comparing the simulation results to the real process data and following the trends of the deviations between the two, different types of faults and upsets can be detected in both the process and sensors. / KKS project:Use of physical models combined with statistical models for improved digester control