Download or read book Polyelectrolyte Adsorption on Cellulose Fibres written by and published by . This book was released on 2001 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effects of Cellulosic Fiber Charges on Polyelectrolyte Adsorption and Fiber fiber Interactions written by A. Elisabet Horvath and published by . This book was released on 2006 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: The surface charges of cellulosic fibers contribute to several papermaking operations that influence the manufacture and final properties of paper. This thesis investigates the effect of the surface charges on wet-end chemistry, e.g. through the interaction of cationic polyelectrolytes with the fiber surface charges, and on the network strength of pulp suspensions. The polyelectrolyte titration method was used to investigate the interaction of the fiber charges with cationic polyelectrolytes. Techniques were developed to fluorescent label the adsorbing cationic polyelectrolyte in order to visualize the adsorption behavior. Fluorescent confocal laser scanning microscopy (CLSM) was used to determine the extent to which the cationic polyelectrolyte adsorbs into the porous fiber wall. It was shown that the polyelectrolyte charge density limits the adsorption to the surface under electrolyte-free conditions. Adsorption into the fiber wall only occurs for two conditions: 1) if the molecular mass is sufficiently low or 2) the electrolyte concentration is high enough to screen the charges along the polyelectrolyte backbone but not the interactions between the polyelectrolyte and the fiber charges.Aside from the polyelectrolyte properties, the fiber charge density contributes to the adsorption behavior of cationic polyelectrolytes. The fiber charge profile was altered by bulk and surface carboxymethylation. The electrolyte concentration at which a deviation from 1:1 stoichiometry occurs was shown to be dependent on the amount of surface charges, such that the deviation in stoichiometry occurs at a higher electrolyte concentration for pulps having a higher surface charge. A hypothesis was developed to test the conditions at which the deviation in adsorption stoichiometry occurs, which was defined as the critical electrolyte concentration (CEC). It was found that the CEC corresponded to the electrolyte concentration at which the distance between the fiber charges was on the order of the Debye length. Electron spectroscopy for chemical analysis (ESCA) was used as an independent calibration procedure to validate for which a 1:1 stoichiometry occurs. The analysis with ESCA agreed well with the polyelectrolyte titration method for measurement of fiber surface charges. When measured under appropriate conditions, i.e. electrolyte concentration and molecular properties, the fiber surface charge can accurately be measured by the polyelectrolyte titration method.The charge profiles of various pulp types and treatments were also examined. Having been established as a valid technique, the polyelectrolyte titration method was again used to measure the surface charge while conductometric titration was used to measure the total charge content. The amount of bulk and surface charges vary depending on the pulping method and type of wood, although the ratio between the bulk and surface charge (i.e. the charge ratio) is similar for chemical pulps. The mechanical pulp has a higher charge ratio because it contains more fines material than chemical pulp. Bleaching of the chemical pulp decreases the amount of bulk and surface charges, although the charge ratio remains essentially constant. However, methods such as beating or carboxymethyl cellulose (CMC) grafting are available to increase the charge ratio.The effect of the charge profile on fiber-fiber interactions was studied on both a microscopic and macroscopic level. Colloidal probe microscopy (CPM) was used to investigate the microscopic interactions between two cellulose surfaces. Cellulose surfaces, prepared by spin-coating a dissolving pulp onto silica, were used to model the fiber surface, which is too rough for surface force measurements. The charge density of the model surface was increased by CMC grafting. Results showed that increasing the surface charge density created large electrosteric repulsions, due to CMC the chains protruding out from the surface. These interactions on the microscopic scale affect the fiber network strength, which was measured with a parallel plate rheometer. When the repulsion is increased between the fibers, caused by the increase in the surface charge, fiber flocs break apart more easily due to a reduced friction between the fiber surfaces.The forces acting on the fiber network can also be mechanical in origin. The fiber length and flexibility were altered in order to study the influence of mechanical surface linking and elastic fiber bending on the fiber network strength. Using the storage modulus (G'0) as a measure of fiber network strength, longer fibers were found to create a stronger network due to an increased amount of fiber contacts. Flexible fibers have a lower network strength than stiff fibers because the fibers come to rest in a less strained position such that the the influence of elastic fiber bending on the fiber network strength is predominant.

Download or read book Kinetics of Polyelectrolyte Adsorption on Cellulosic Fibres written by and published by . This book was released on 2000 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Paper Chemistry and Technology written by Monica Ek and published by Walter de Gruyter. This book was released on 2009-12-15 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: This four volume set covers the entire spectrum of pulp and paper chemistry and technology from starting material to processes and products including market demands. This work is essential for all students of wood science and a useful reference for those working in the pulp and paper industry or on the chemistry of renewable resources. Volume 3 provides an overview of paper production and the ways in which the chemistry of starting materials and processes influence its quality and properties. The work treats fundamental properties of the fibre wall and the consolidation of fibres during pressing and drying, surface chemistry of fibres and their influence on the interaction between fibres/paper and other materials, mechanisms behind the adsorption of polyelectrolytes to fibres and fillers, acid and alkaline sizing of paper, basic fluid mechanical behavior of fibre suspensions, web forming, web pressing and web drying in a modern paper machine, calandering and coating of paper.

Download or read book Adsorption of Polyelectrolytes Onto Cellulosic Fibres and Other Charged Surfaces written by Rein Aksberg and published by . This book was released on 1990 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Adsorption of Polyelectrolytes and Polymer induced Flocculation of Cellulosic Fibers written by Lars Wågberg and published by . This book was released on 1987 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Adhesion Between Substrates Covered with Polyelectrolyte Multilayers written by Rikard Lingström and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis examines the formation of Polyelectrolyte Multilayers (PEM) on cellulose fibres as a new way of influencing the fibre surface and the adhesion between wood fibres. The aim of the study was to enhance the fundamental understanding of the adsorption mechanisms behind the formation of Polyelectrolyte Multilayers on cellulose fibres; to study how the properties of the layers can be influenced and to show how the properties of the layers influence the adhesion between the fibres and the strength of paper sheets made from the PEM treated fibres. Different polyelectrolyte systems are known to form PEMs with different properties, and in this work two different polymer systems were extensively studied: poly(dimethyldiallylammonium chloride) (PDADMAC) / poly(styrene sulphonate) (PSS), which are both strong polylectrolytes (i.e. are highly charged over a wide range of pH) and poly allylaminehydrochloride (PAH) /poly acrylic acid (PAA), which are both weak polyelectorlytes (i.e. sensitive to pH changes). PEMs were also formed from PAH/ poly(3,4-ethylenedioxythiophene):PSS (PEDOT:PSS), in order to form electrically conducting PEMs on fibres and PEM-like structures were formed from polyethylene oxide (PEO) and polyacrylic acid (PAA). (...).

Download or read book Cellulose Interaction with Cationic Polyelectrolyte written by Jielong Su and published by . This book was released on 2015 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paper engineering of strength, structure and surface using interactions between cellulose and cationic polyelectrolytes are investigated with the aim of improving paper-based bio-analytical devices (PADs). Advances are described based on fundamental knowledge and engineering aspects in this field that have enable the development of lighter weight papers that have high wet strengths, controlled porosities and multi-functional properties that can be fine tuned.The influence of reactive cationic polyelectrolyte, polyamideamine-epichlorohydrin (PAE) on paper strength behaviour was studied using hardwood fibers, both with and without inorganic electrolyte. Ion type and concentration in the papermaking process water was found to influence the strength development in different ways. The relationship between repulpability of PAE- strengthened paper and wet strength is described. The effect of blending microfibrillated cellulose (MFC) with hardwood fibers is compared with the refining of hardwood fibers on paper composite properties, with and without PAE addition. Papers incorporating tethered MFC, produced by refining of hardwood fibres, are found to provide equivalent strength properties to papers incorporating untethered MFC with significant drainage benefits and formation uniformity. Air permeability of the composites decreases with untethered and tethered MFC addition.MFC achieved by ball milling and cellulose micro-particles (CMPs) developed by cryogenic milling softwood fiber are compared with commercial MFC produced by homogenization. The effect of blending two MFCs and CMPs with hardwood fibers on the paper composites properties is investigated in terms of nano/micro cellulose dimensions. CMPs act as mechanical debonding agents and decrease substrate density and strength whereas MFC have higher aspect ratios and smaller size distributions that significantly improve strength and density of composite sheets while decreasing porosities. The addition of MFC combined with PAE can increase both dry and wet strength. The different stress-strain curves under wet conditions are described and these suggest two different mechanisms of strength development: MFC-fiber entanglement and fiber-fiber contact reinforcement.The role of paper macroscale properties and structure are described in PADs used to type human red blood cells (RBCs). A series of commercial and laboratory-generated papers varying in fibre composition, basis weight, density and porosity are studied and their abilities to separate antibody agglutinated (specific) from non-agglutinated (non-specific) RBCs are reported. Image analysis is used to measure the intensities of blood spots produced by sequentially absorbing solutions of antibodies and blood samples on paper then eluting with a saline solution. The performance of these papers in blood typing is found to decrease linearly with paper density and thickness and it is inversely proportional to paper pore size. The type of fibres plays a minor role. Porous cellulose webs modified with cationic polyelectrolyte further optimize blood typing analysis.Cellulose model surfaces, in the form of quasi molecularly smooth thin cellulose films, are investigated to examine the interactions between cellulose, cationic polyelectrolytes and biomolecules. Thin smooth cellulose films are prepared by spin coating either a nanocellulose crystal suspension, or a cellulose acetate solution onto silicon surfaces with subsequent hydrolysis. Film smoothness is greatly improved by controlling the concentration of cellulose acetate and the hydrolysis time in methanolic sodium methoxide. High molecular weight polyacrylamides (CPAM) are used as model polyelectrolytes, and the nanoscale conformation of adsorbed CPAM at the cellulose/water interface is characterized in situ by specular neutron reflectometry. The effect of CPAM charge density and added NaCl (10-3 M) is described. At constant molecular weight, the thickness of the CPAM layer adsorbed on cellulose increases with polymer charge density. Addition of NaCl decreases the thickness of a CPAM layer already adsorbed on cellulose. However the thickness of the adsorption layer on cellulose of a CPAM solution pre-equilibrated in NaCl is much higher, because the re-shrunk polymer coils do not relax as much upon adsorption.Deuterated cellulose film having better contrast for neutron reflectometry is investigated. Incorporation of deuterium into bacterial cellulose is achieved by growing Gluconacetobacter xylinus - strain ATCC 53524 in a mixture of deuterated glucose and deuterated glycerol. Two strategies are compared for synthesizing deuterated cellulose derivatives that are soluble in volatile solvents (acetone and toluene) suitable for spin coating: one involves acetylation in acetic anhydride, the other trimethylsilylation in ionic liquid (1-butyl-3-methylimidazolium chloride). The trimethylsilylation of deuterated cellulose results in a much higher yield of product, and is used to prepare toluene solutions for spin-coating onto smooth flat silicon substrates. The resulting thin film is hydrolysed back to deuterated cellulose using hydrogen chloride vapour.The data generated is used to prepare improved substrate papers for use in PADs with high wet strength, controlled structure and fine-tuned surface properties.

Download or read book Polyelectrolyte Complexes in the Dispersed and Solid State II written by Martin Müller and published by Springer. This book was released on 2013-08-23 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyelectrolyte Complexes for Tailoring of Wood Fibre Surfaces. Polyelectrolyte Complexes in Flocculation Applications. Spontaneous Assembly and Induced Aggregation of Food Proteins. Polyelectrolyte Complexes of DNA and Polycations as Gene Delivery Vectors. Sizing, Shaping and Pharmaceutical Applications of Polyelectrolyte Complex Nanoparticles.

Download or read book Molecular Dynamics Simulation Study of Polyelectrolyte Adsorption on Cellulose Surfaces written by Oliver Biermann and published by . This book was released on 2002 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Polyelectrolyte Adsorption on Packed Beds of Pulp Fibers written by Laura Ciovica and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cationic starches on cellulose surfaces written by Henrica G. M. Steeg (van de) and published by . This book was released on 1992 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Polyelectrolyte Adsorption on Wood Fibers written by Joanna Lee Koethe and published by . This book was released on 1992 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Influence of Aluminum Salts on the Adsorption of Cationic Polyelectrolyte by Cellulosic Fibers written by Roger D. Crow and published by . This book was released on 1985 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Powders and Fibers written by Michel Nardin and published by CRC Press. This book was released on 2006-12-21 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: New analytical methods have provided further insight into the structure, surface characteristics, and chemistries of increasingly small particles. However, current literature offers information on only a limited number of powders being investigated. Written by renowned scientists in the field, Powders and Fibers: Interfacial Science and Application

Download or read book Sustainability of Biomass through Bio based Chemistry written by Valentin I Popa and published by CRC Press. This book was released on 2021-03-22 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: The process of photosynthesis is a potential source of energy and bioproducts. Renewable sources of polymeric materials offer an answer to maintaining sustainable development of economically and ecologically attractive technology. The innovations in the development of materials from biopolymers, preservation of fossil-based raw materials, complete biological degradability, reduction in the volume of garbage and compostability in the natural cycle, climate protection through reduction of carbon dioxide released, and the application possibilities of agricultural resources for the production of bio/green materials are some of the reasons why such materials are attracting public interest. FEATURES Discusses waste from urban areas, forestry and agricultural processes, specifically grown crops such as trees, starch crops, sugar crops hydrocarbon plants and oils, and finally aquatic plants such as water seaweeds and algae, which can be used as raw materials for sustainable development. Presents recent advances in the development of some specifically chemical components of biomasses for a sustainable future. Focuses on lignocellulose as a source of bio-based products. Draws upon expertise from various countries. Describes how upgraded and integrated biomass processing may reduce the risks associated with the COVID-19 pandemic. Valentin I. Popa is professor emeritus of Wood Chemistry and Biotechnology at Gheorghe Asachi Technical University of Iasi, Romania.

Download or read book Cellulose Chemistry and Properties Fibers Nanocelluloses and Advanced Materials written by Orlando J. Rojas and published by Springer. This book was released on 2016-02-25 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vincent Bulone et al.: Cellulose sources and new understanding of synthesis in plants Thomas Heinze et al.:Cellulose structure and properties Thomas Rosenau, Antje Potthast, Ute Henniges et al.: Recent developments in cellulose aging (degradation / yellowing / chromophore formation) Sunkyu Park et al.:Cellulose crystallinity Lina Zhang et al.:Gelation and dissolution behavior of cellulose Yoshiyuki Nishio et al.:Cellulose and derivatives in liquid crystals Alessandro Gandini, Naceur Belgacem et al.:The surface and in-depth modification of cellulose fibers Emily D. Cranston et al.:Interfacial properties of cellulose Herbert Sixta, Michael Hummel et al.Cellulose Fibers Regenerated from Cellulose Solutions in Ionic Liquids Qi Zhou et al.:Cellulose-based biocomposites Orlando Rojas et al.:Films of cellulose nanocrystals and nanofibrils Pedro Fardim et al.:Functional cellulose particles Wadood Hamad et al.:Cellulose Composites