<p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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.</p> / <p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>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.</p>

<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>

Thesis (Ph. D.) in Chemical Engineering--University of Maine, 2000. / Includes vita. Includes bibliographical references (leaves 129-134).

Thesis (Ph. D.)--Institute of Paper Chemistry, 1956. / Includes bibliographical references (p. 110-113).

Thesis (Ph. D.) in Chemical Engineering--University of Maine, 2001. / Includes vita. Advisory Committee: William N. Unertl, Prof. of Physics, Co-Advisor; Douglas W. Bousfield, Prof. of Chemical Engineering, Co-Advisor; Vincent Caccese, Prof. of Mechanical Engineering; Albert Co, Prof. of Chemical Engineering; Nick Triantafillopoulos, Adjunct Prof. of Chemical Engineering, OMNOVA Solutions. Includes bibliographical references (leaves 149-157).

No description available.

This dissertation is a study based on the effects of electronic technology, the environment and globalisation on the global paper industry. The study aims to illustrate the effect that each of these aspects have towards the threat of diminishing paper consumption and to thereafter draw certain conclusions and propose recommendations to those within the paper industry. E-Commerce and related innovations such as the electronic supply chain are transforming the pulp and paper industry by reducing the need for paper, thereby cutting costs, reducing inventory and opening up new business developments. The effects of the changing world will have a major impact on the paper industry. The external drivers of change in the pulp and paper industry are increasing environmental concerns, global economic fluctuations, digitalisation and demographic changes and skills shortages. Pulp and paper production, consumption and wasting have numerous negative environmental and social impacts. The pulp and paper industry is amongst the world's major generators of air and water pollutants, waste products, and the gases that cause climate change. It is also one of the major users of raw materials, including fresh water, energy and forest fibres. The pulp and paper industry is entering a new era of business evolution driven largely by consolidation of industry, globalisation and competition. These market drivers are compelling the pulp and paper industry to place greater focus on cost efficiency. This focus is creating a new challenge for the organisation by way of information technology. The study entailed research by means of a questionnaire, each consisting of twenty eight questions, incorporating a combination of both closed and open-ended questions. Data was obtained from thirty respondents. Quantitative research was chosen over qualitative research as this methodology offers a high level of measurement precision and statistical advantage. Quantitative methods ensure a greater level of reliability of data. Research using quantitative methodology also eliminates or minimises the subjectivity of judgement. Further research was suggested and included conducting a qualitative study, exploring the aspect of diversification and understanding the recycling sector of the industry. / Thesis (MBA)-University of KwaZulu-Natal, 2006.