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The biocompatibility and very high specific area of cellulose nanofibrils (CNF) are properties of high interest for the development of active substrates for new medical device development. Enzyme pretreated CNF (CNF-e) can be self-organized into nanostructured membranes that are suitable for active principle ingredients (API) encapsulation through adsorption phenomena. In addition, tunable surface chemistry of CNF-e, allow for covalent immobilization of API. In this work, ciprofloxacin is integrated to CNF-e membranes according to two different strategies. The first one relies only on adsorption mechanisms; ciprofloxacin is encapsulated in the bulk before the membrane formation by solvent casting. The influence of the membrane properties and preparation parameters such as grammage, thickness and drying technique, are assessed with water uptake measurements and API release experiments. The second strategy deals with the covalent immobilization of ciprofloxacin directly onto CNF-e membrane. The two kinds of membranes are then compared in terms of antibacterial activity, in both static and dynamic conditions. Thick CNF-e membranes loaded with adsorbed ciprofloxacin that were overdried (2 h, 150 °C) prove to be more resistant in liquid medium and present a more prolonged drug release. However, these membranes rapidly lost their antibacterial activity, while CNF-e membranes with covalently immobilized ciprofloxacin remain contact active for several days. These 100% CNF active nanostructured membranes can be used as new wound dressing for topical application.

Cellulose nanofibrils (CNF) are renewable bio-based materials with high specific area, which makes them ideal candidates for multiple emerging applications including for instance on-demand drug release. However, in-depth chemical and structural characterization of the CNF surface chemistry is still an open challenge, especially for low weight percentage of functionalization. This currently prevents the development of efficient, cost-effective and reproducible green synthetic routes and thus the widespread development of targeted and responsive drug-delivery CNF carriers. We show in this work how we use dynamic nuclear polarization (DNP) to overcome the sensitivity limitation of conventional solid-state NMR and gain insight into the surface chemistry of drug-functionalized TEMPO-oxidized cellulose nanofibrils. The DNP enhanced-NMR data can report unambiguously on the presence of trace amounts of TEMPO moieties and depolymerized cellulosic units in the starting material, as well as coupling agents on the CNFs surface (used in the heterogeneous reaction). This enables a precise estimation of the drug loading while differentiating adsorption from covalent bonding (∼1 wt% in our case) as opposed to other analytical techniques such as elemental analysis and conductometric titration that can neither detect the presence of coupling agents, nor differentiate unambiguously between adsorption and grafting. The approach, which does not rely on the use of 13C/15N enriched compounds, will be key to further develop efficient surface chemistry routes and has direct implication for the development of drug delivery applications both in terms of safety and dosage., DNP-enhanced solid-state NMR unravels the surface chemistry of functionalized nanocellulose.

Nowadays, drug encapsulation and drug release from cellulose nanofibrils systems are intense research topics, and commercial grades of cellulose nanomaterials are currently available. In this work we present an ester-containing prodrug of metronidazole that is covalently bound to cellulose nanofibrils in aqueous suspension through a two-step immobilization procedure involving green chemistr y principles. The presence of the drug is confirmed by several characterization tools and methods such as Raman spectroscopy, elemental analysis, Dy-namic Nuclear Polarization enhanced NM R . This technique allow s enhancing the sensitivity of NM R by several orders of magnitude. It has been used to study cellulose nanofibrils substrates and it appears as the ultimate tool to confirm the covalent nature of the binding through thiol-yne click chemistry. Moreover, the ester function of the immobilized prodrug can be cleaved by specific enzyme activity thus allowing controlled drug release.

High and uncontrolled surface active substances (SAS) concentrations in deinking line process waters strongly disturb flotation deinking. Indeed, their adsorption at air/water and ink/water interfaces stabilizes air bubbles and ink particles, reducing ink collection during flotation. In addition, foam stabilization promoted by SAS reduces froth drainage and consequently enhances suspended solids losses. All in all, selectivity of flotation is negatively affected by excessive SAS concentrations. Floating process water with adapted technology, a patented solution, is an efficient way to decrease SAS concentration and thereby recover flotation deinking selectivity. This concept was tested at industrial scale with success. First loop clear filtrates of a deinked pulp line (for newsprint production) were floated. At steady state, this treatment allows a 20% reduction of the SAS concentration in first loop process water. Evaluation of ink removal selectivity at pre-flotation and post-flotation showed a significant improvement in comparison with reference values. During the trial, the mill could either produce pulp with lower ink content and consequently higher brightness (50 ppm effective residual ink concentration [ERIC] less, corresponding to a 1 brightness point increase) for similar losses, or similar pulp quality with 1% to 2% yield improvement, representing a huge cost reduction. In addition, beneficial side effects were reported, such as reduced deinking chemicals consumption (soda, silicate, and bleaching agents) and better paper machine runnability, especially in terms of stickies breaks.

This study presents a rapid method for nanopaper production by spray deposition of high concentration microfibrillated cellulose (MFC) slurries on a nylon fabric and their subsequent filtration dewatering. The filtration time for the consolidation of a wet MFC mat was of 15 and 90 s for sheets with basis weight of 13.7 and 124 g m−2, respectively. MFC films exhibited excellent Young's modulus of ca. 18 GPa and intrinsic air permeability of ca. 0.22 nm2. Nevertheless, the progressive decrease of the basis weight from 124 to 13.7 g m−2 induced the decay of the film tensile properties (stress and strain at break dropped from 150 MPa and 4.6% to 50 MPa and 0.4%) and the onset of a brittle behaviour. This trend was ascribed to the presence of residual fibre debris in the MFC slurry which acted as fracture nucleation spots in thin films.

Herein, we report on the preparation of novel cellulose-PEG biohybrid papers with wet strength properties. The biohybrid paper sheets are obtained using a two-step procedure where ω- or α, ω-azide functionalized PEG chains are anchored onto alkyne-functionalized wood fibers through CuAAC ligation in mild and aqueous conditions. The incorporation of the PEG grafts mostly occurs at the periphery of the cellulose fibers and degrees of substitution up to 0.028 are obtained. The presence of PEG grafts significantly increases the tensile, burst and tear strength properties in the wet state, the reinforcement being more pronounced for fibers grafted with α,ω-azide PEG. This reinforcement is consistent with a relatively sparse hetero-crosslink reaction creating inter-fiber covalent bonds and forming a cellulose network within the cell wall.

A novel UV-induced procedure, in the presence of glycidyl acrylate and proper radical/cationic photoinitiators, is here proposed to promote the in situ grafting of a methacrylic polymer network to the surface of natural cellulose fibers. As a result, composite polymer membranes reinforced by cellulose handsheets are obtained and demonstrate excellent mechanical features. The reactivity of the monomers is studied by FT-IR in real time measurements and the successful grafting is confirmed by surface spectroscopies. The polymer membranes prepared show high elastic modulus and tensile resistance and maintain high flexibility even after activation by swelling into a standard liquid electrolyte solution. The swelling procedure allowed us to obtain high ionic conductivity and remarkable electrochemical behavior when tested in laboratory scale lithium polymer cells. The system shows attractive features such as intrinsic safety, eco-compatibility, and low production cost and industrialization potentials, and is highly suitable for the rapidly expanding field of Li-based flexible batteries.

Methacrylic-based thermo-set gel–polymer electrolytes obtained by the easy and reliable photo-polymerisation process and mechanically reinforced by a cellulose handsheet (paper) for flexible lithium batteries application are here presented. Adhesion between cellulose and polymer is improved by “in situ” grafting supported by benzophenone; the ionic conductivity of the electrolyte is enhanced by the use of specifically designed handsheets containing alumina. Thermal and mechanical properties of the new membranes are characterised and the effect of the different composition of the reinforcement on the ionic conductivity of the membranes is discussed.

Fully-solid methacrylic-based thermo-set polymer electrolyte membranes reinforced with nanoscale micro-fibrillated cellulose (MFC) fibres are here presented. The preparation is carried out in water and the membrane is obtained by an easy and reliable UV-induced polymerisation via a free radical mechanism; thus, the overall process is highly energy efficient and environmentally friendly. The morphology of the composite electrolytes as well as the mapping of the elements present in the system is investigated by scanning electron microscopy, while the thermal behaviour is investigated by thermo-gravimetric analysis and differential scanning calorimetry. The composite polymer electrolytes prepared by MFC fibres reinforcement exhibit excellent mechanical properties with a Young’s modulus as high as 32 MPa. Acceptable ionic conductivity values (above 0.1 mS cm−1 at 50 °C) and good overall electrochemical performances are maintained, ensuring that such specific approach would make these hybrid organic, cellulose-based composite polymer electrolyte systems a strong contender in the field of thin and flexible fully-solid lithium based power sources, especially for moderately high temperature applications.

This work describes the surface modification of filter paper by a photoinduced grafting process involving a poly(oxetane) acrylic oligomer with short perfluoroalkyl chains. This modifier avoids the safety, environmental and health concerns of conventional long perfluoroalkyl-chain chemistries, without sacrificing their key performance features. Therefore the work provides an alternative to existing processes aiming to make the paper hydrophobic: the chemicals used are safe, the proposed functionalization process is rather simple and inexpensive, moreover can be adapted to paper making plants. The experiments show that the grafting induced by UV irradiation changes the surface composition of the samples as assessed by surface spectroscopies and other measurements. As a result of the surface modification, water contact angles on treated paper surfaces were as high as 143° approaching superhydrophobicity. Also oleophobicity was improved ( ϑ = 57°), guaranteeing grease and antistain resistance. Surface tension was strongly reduced and water resistance was improved. XPS, static and dynamic contact angles and capillary wetting studies indicate a substantial gradient in surface energy normal to the treated paper surface.

International audience; Alkyne-functionalized cellulose fibers have been generated through etherification under basic water or hydroalcoholic conditions (NaOH/H2O/isopropanol). For a given NaOH content, the medium of reaction and, more particularly, the water/IPA ratio, were shown to be of crucial importance to derivatize the fibers without altering their integrity and their crystalline nature. It was shown that the degree of substitution (DS) of the fibers increases concomitantly with isopropanol weight ratio and that, contrary to water or water-rich conditions, derivatization of fibers under isopropanol-rich conditions induces an alteration of the fibers. Optimization of etherification conditions in aqueous media afforded functionalized cellulose materials with DS up to 0.20. Raman confocal microscopy on derivatized fibers cross sections stressed that alkyne moieties are incorporated all over the fibers. The resulting fibers were postfunctionalized by molecular probes and macromolecules in aqueous or water-rich conditions. The effectiveness of the grafting was strongly impacted by the nature of the coupling agents.

The kinetics of the hydrolysis and self-condensation reactions of 3-(2-amino-ethylamino)propyl-trimethoxysilane (DAMS) were investigated by in situ 29Si NMR spectroscopy using pure water and an alcoholic (80:20 w/w ethanol/water) solvent mixture as reaction media. In both media, the reactivity of the silane was strongly influenced by the pH of the medium during the initial stage of the reaction. The silanols produced by hydrolysis in water were much more stable than those produced in the alcoholic solvent mixture, the latter of which were susceptible to self-condensation, yielding siloxane bridges. The active silanol reactivity (SR), which is a simple parameter that reflects the silanol content in the solution as a function of the reaction time, was proposed for evaluating the reactivity of a solution of DAMS. SR was maintained at a good level (high silanol group concentration) when pure water was used as the reaction medium. The pH of the reaction appears to be the predominant parameter for determining the SR during the first 2 h, regardless of the reaction solvent.

Methacrylic-based thermo-set gel-polymer electrolyte membranes obtained by a very easy, fast and reliable free radical photo-polymerisation process and reinforced with microfibrillated cellulose particles are here presented. The morphology of the composite electrolytes is investigated by scanning electron microscopy and their thermal behaviour (characteristic temperatures, degradation temperature) are investigated by thermo-gravimetric analysis and differential scanning calorimetry. The composite membranes prepared exhibit excellent mechanical properties, with a Young's modulus as high as about 80 MPa at ambient temperature. High ionic conductivity (approaching 10 −3 S cm −1 at 25 °C) and good overall electrochemical performances are maintained, enlightening that such specific approach would make these hybrid organic, cellulose-based composite polymer electrolyte systems a strong contender in the field of thin and flexible lithium based power sources.

Methacrylic-based thermo-set gel-polymer electrolytes obtained by an easy and reliable free radical photo-polymerisation process demonstrate good behaviour in terms of ionic conductivity, interfacial stability with the Li-metal electrode and cyclability in lithium cells. Though the obtained membranes are flexible, self standing and easy to handle, there is room for improving mechanical strength. In this respect, a novel approach is adopted in this work, in which a cellulose hand-sheet (paper), specifically designed for the specific application, is used as a composite reinforcing agent. To enhance its compatibility with the polymer matrix, cellulose is modified by UV-grafting of poly(ethylene glycol) methyl ether methacrylate on it. Excellent mechanical properties are obtained and good overall electrochemical performances are maintained; highlighting that such specific approach would make these hybrid organic, green, cellulose-based composite polymer electrolyte systems a strong contender in the field of thin and flexible Li-based power sources.

Polypyrrole was chemically synthesised by using, for the first time, Birchwood xylan as additive, and ammonium peroxydisulfate (APS) as oxidant. The impact of additive concentration, polymerisation time and reagents concentration on PPy conductivity was studied. It was shown that, once fixed the pyrrole (Py)/APS and Py/xylan optimal ratios, the best conductivities (26 S/cm) were obtained for short polymerisation times (30 min) and increased reactants concentration. Morphological analysis of PPy particles, Py depletion kinetics and oxido-reduction potential measurements of the solutions provided interpretation elements on the impact of the polymerisation time on PPy pellet conductivity. Furthermore, optimised PPy particles obtained with xylan (PPyx) were mixed with nanofibrillated cellulose (NFC) in order to obtain freestanding films. Their electrical and handling performances were evaluated at increasing PPy weight fraction in the samples. The conductivity mechanism of the most conductive sample (in comparison with a low performing sample) was investigated by measuring the conductivity as a function of temperature (4–350 K) and two transport regimes were identified. Selected formulations were finally used to produce conducting PPy/NFC coatings on non-absorbent (glass) and absorbent (copy paper) substrates. The impact of NFC in the percolation of PPy particles, then in the coating conductivity, was investigated.

Wood and cellulose derivatives, in both fibrous and water-soluble macromolecular form, are emerging as outstanding candidates for organic electronics applications due to their large-scale availability, low cost, and easy processability. Paper and wood fibre-based derivatives are considered to be materials of choice as supports for communication world-wide. The interest in producing inexpensive and universally available conducting polymer/cellulose fibres substrates resides in the possibility of creating new materials that can be used for a broad range of advanced applications. For instance, PPy/cellulose fibres composites can be used for the preparation of energy storage devices thanks to the conjugation of the high specific area of cellulose fibres and the electrochemical properties of PPy. Other possible applications of such composites are in the area of the antistatic materials, sensors, electromagnetic interference shielding materials, smart packaging, and tissues. Concerning the woody polymers, some of them (i.e. cellulose derivatives) also exhibit biocompatibility, as well as film-forming properties and transparency. In combination with the electrical properties of PPy, these features make PPy/macromolecular cellulose composites suitable for applications as displays, lighting, and photovoltaics. Due to their chemical structure, macromolecular wood derivatives have been proposed with success as enhancing conductivity additives in Py polymerisation. The aim of the present review is to provide an overview of PPy chemistry and of the most relevant advances attained in the production of PPy/wood derived materials conducting composites.

Residence time distribution (RTD) measurements performed in a small laboratory flotation column using an electrolyte tracer, showed that, without air injection, cellulose fibres induced a sizeable decrease in tracer average residence time, owing to the formation of stagnant zones. Bubble size, fibre flocculation level and gas hold-up were recorded during flotation experiments with different fibre and surfactant concentrations: a slight decrease in bubble size, fibre flocculation level and increased gas hold-up were measured after surfactant addition. The increase of cellulose fibres concentration promoted bubble coalescence, pulp flocculation and gas hold-up. Experimental data interpretation with the drift flux model demonstrated that fibre flocculation depressed gas hold-up by raising the bubble rise velocity. Moreover, correlations between fibre flocculation and their transport during the flotation process showed that pulp flocculation also promoted bubble entrapment in fibre flocs and their subsequent entrainment by air bubbles into the froth.

The use of carboxymethylcellulose (CMC) in polypyrrole (PPy) synthesis and in the production of PPy freestanding films was investigated. PPy was synthesised by chemical oxidative polymerisation in aqueous solutions using ammonium persulfate (APS) as oxidant and CMC as conductivity enhancer (CMC d ). CMCs with different molar weight, namely 90,000 and 250,000 g/mol, were tested. The influence of polymerisation temperature, time, and CMC concentration, on the conductivity of PPy was evaluated thus showing that higher conductivities were obtained at low temperature, short polymerisation time and in the presence of low molar weight CMC. A long time polymerisation study was carried out at 3 °C and 24 °C revealing the presence of a double regime polymerisation process, with second regime rates depending on the polymerisation temperature. CMC was also used to improve the limited film forming ability of PPy by dispersing preformed PPy particles in CMC aqueous solutions. When decreasing the weight fraction of film forming CMC, semiconducting, flexible and freestanding films with thickness of 50–100 μm were obtained and their conductivity increased proportionally to the CMC weight fraction.

There is a need to monitor flotation deinking operations, in order to better control their efficiency, reduce losses, and save fiber resources. The objective of this work is to understand the varia...

Hydrophobisation treatment or sizing is conducted to limit the penetration of water or other liquids into papers, mainly for printing and writing or converting purposes. Internal sizing can be obtained through the addition of alkyl ketene dimer (AKD) into the pulp suspension. It is well known that AKD sizing efficiency depends on process parameters such as pulp grade, dissolved and colloidal substances, and paper drying and storage conditions, but the mechanisms involved are not totally understood. This study focused on the effect of wood extractives on sizing efficiency. First, a thermomechanical pulp (TMP) was used before and after extraction with various solvents and its response to sizing was evaluated. Then, dehydroabietic acid (DH) and hemicelluloses were added to a bleached kraft pulp (BKP) and their effect on sizing, alone or with the coupled action of calcium ions, was studied. The results obtained confirmed that TMP is more difficult to size than BKP and that extraction performed on TMP allows retaining an acceptable sizing level. DH and hemicelluloses impair AKD sizing efficiency and they decrease both retention and reaction of AKD particles onto the fibres. Finally, calcium ions, when alone, may negatively impact AKD retention, but they prevent in certain conditions the detrimental action of DH and xylan.

Polypyrrole (PPy) was chemically synthesised at two pH levels (pH = 2 and unadjusted pH, i.e. 6.6) using pre-formed carboxymethylcellulose-iron (CMC-Fe) complexes. The CMC-Fe complexes were prepared at a fixed CMC concentration, i.e. 5.5x10-5 mol/L, and with an increasing FeCl3 amount (from 4x10-3 to 5x10-2 mol/L). The quantity of iron bound to CMC was determined by the inductively coupled plasma (ICP-MS) method. In order to understand the interactions between CMC and iron, speciation of the systems was simulated by Phreeqc software. SEM analysis showed that, in some conditions (particularly at pH = 2), Py polymerised within the CMC-Fe complexes, forming particles with size ranging between 300 and 600 nm. In order to evaluate polymer electric conductivity, films were prepared by direct casting of the PPy-CMC-Fe dispersions with and without addition of film-forming CMC, and bulky PPy-CMC-Fe pellets were obtained by compression. Despite the different arrangement PPy-CMC-Fe particles in dry films, the amount of iron bound to CMC during the formation of CMC-Fe complexes was found to be the dominant parameter affecting polymer conductivity.

The impact of natural polymeric dispersants, that is, carboxymethyl cellulose and guar gum, on the flotation selectivity was investigated on a flotation deinking pilot plant. Their effect on pulp flocculation, air bubble size, and gas hold-up was determined by implementing a fiber flocculation sensor, an automated bubble measurement device, and a gas hold-up sensor on the pilot cell. Dispersants reduced pulp flocculation and induced an increase in gas hold-up and a slight decrease in the air bubble size. Their addition promoted ink removal and, at the same time, depressed fiber entrainment and mineral fillers flotation, thus increasing exceptionally the flotation selectivity.

PPy was synthesised by oxidative chemical polymerisation using xylan, CMC and NFC as additives. Conducting nanocomposite films were cast from aqueous slurries using doped PPy particles, CMC and NFC as the conducting and reinforcing phase, respectively. NFC-based composites had higher conductivity and lower mechanical properties than CMC-based homologues. SEM analysis showed that in PPy/NFC composites, PPy and NFC were arranged in two entangled networks, whereas, in PPy/NFC composites, CMC formed a continuous matrix around PPy particles, thus limiting conductivity. Mechanical properties of nanocomposite films were interpreted as reflecting the presence of different structures when using NFC or CMC as reinforcing phase.

Surfactants are largely present in papermaking/recycling processes. They are added intentionally or come with raw materials or process/functional additives. Once they have reached the process, they build-up in the circuits and, depending on their surface activity and concentration, they can have adverse effects on deinking and on the whole papermaking process, such as excessive frothing, depression of ink floatability, and paper sizing/retention difficulties. In this paper, the removal of apparent surface active chemicals (ASAASAASAC) is first evaluated in different flotation deinking mills through mass balances using surface tension measurements and a specific methodology. Mill data show that, in two-stage deinking lines, ASAASAASAC are slightly concentrated in the second stage, contributing to an increase in pulp frothing behavior, in flotation loss, and in some cases to a low ink removal efficiency. Trends observed in deinking mills are then interpreted using experimental data obtained at the laboratory scale in the presence of a model surfactant, and by process simulation. The effect of ASAASAASAC concentration on the efficiency of the flotation deinking process is explained in terms of their effect on particle and water transport sub processes, namely, flotation, entrainment, frothing, and drainage.

Cellulose-Based Graft Copolymers: Structure and Chemistry discusses the synthesis, characterization, and properties of multifunctional cellulose-based graft copolymers. Presenting the contributions of accomplished experts in the field of natural cellulosic polymers, this authoritative text: Offers an overview of cutting-edge technical accomplishmen

A methacrylate based plasticised polymer electrolyte membrane is prepared via a rapid and facile UV curing process, the major concerns of mechanical integrity are overcome by simply using appropriately modified cellulose handsheet laden with nano-sized acidic alumina particles as a reinforcement. The use of the cellulose handsheets greatly enhances the flexibility and mechanical properties of the membrane while the addition of alumina particles helps to maintain satisfactory conductivity values. The reinforced composite electrolyte membrane is also tested in a real lithium cell, exhibiting excellent performance which account for its use in futuristic lithium batteries having low cost, environmentally friendly and easily scalable properties.

Semi-crystalline fluorinated polymers represent an interesting class of high-performing, melt-processible materials. Structure–properties relationships are discussed at a molecular level starting from the atomic properties of the fluorine atom. Their synthesis and microstructure are reported in detail. Further focus is given to their thermal resistance, crystalline structure, mechanical and thermodynamic behaviour, as well as to some other miscellaneous properties. Finally, some main applications are briefly dealt with. © 2001 Society of Chemical Industry

One of the main drawbacks that restricts the practical application of gel-polymer electrolytes is the inferior mechanical performance compared to other available systems. In this work, we have reinforced UV-cured methacrylic membranes with cellulose. To enhance its compatibility with the polymer matrix, cellulose is modified by UV-grafting poly(ethylene glycol) methyl ether methacrylate on it. Excellent mechanical properties are obtained and good ionic conductivity values are observed, enlightening that this kind of membrane is an interesting candidate for future applications as thin gel-polymer electrolyte in flexible lithium batteries. Keywords: Cellulose hand-sheet, UV-curing, Gel-polymer electrolyte, Mechanical property, Li-cells

The surface modification of cellulose opens the way towards almost infinite new applications, making it suitable for functional and sustainable materials. Additionally, it also represents a possibility for up-grading traditional products. In this work, we report about the photo-induced grafting onto cellulose substrates of a highly fluorinated acrylic monomer, characterized by a long perfluoropolyether chain. Grafting changed the surface composition, as assessed by XPS measurements: the values of F/C atomic ratio were close to that of the pure monomer at the most external surface (~13 A depth). Surface energy was therefore dramatically reduced. This led to interesting modifications of the paper characteristics. The wettability by different liquids was decreased and the stain resistance improved. Moreover, anti-adhesion properties were imparted to the paper sheet. At the same time the bulk properties of the modified fibre network, such as its tensile strength and the burst resistance, were unchanged.

An original procedure is described which calls upon the heterogeneous grafting of bifunctional molecules onto a reactive polymeric surface, leaving one of the functions available for further exploitation. The principle of this strategy is to use reagents characterised by a rigid planar structure bearing the two active moieties at opposite sites of the molecule. The examples provided include the reactions of lignocellulosic fibres with 1,4-phenyl diisocyanate and 1,2,4,5-benzenetetracarboxylic anhydride, which give rise to their surface activation through the incorporation of covalently bound isocyanate or anhydride functions. © 2001 Society of Chemical Industry

In this work, the contribution of flotation deinking banks design on ink removal efficiency, selectivity, and specific energy consumption was simulated using a semiempirical approach. Single-stage with mixed tank/ column cells, two-stage, and three-stage configurations were evaluated, and the total number of flotation units in each stage and their interconnection were used as main variables. Explicit correlations between ink removal efficiency, selectivity, energy consumption, and line design were developed for each configuration. When considering a conventional two-stage configuration as reference, a decrease in the specific energy consumption for constant ink removal efficiency and selectivity was obtained with the single-stage bank with a stack of flotation columns at the front of the line, whereas an increase in ink removal selectivity for constant ink removal efficiency and specific energy consumption was obtained with the three-stage bank. The present results show that the performance of conventional flotation deinking banks can be improved by optimizing process design and implementing mixed tank/column technologies in the same deinking line.

Transport coefficients and correlations recently used to describe surfactant contribution to particle and water transport in a laboratory flotation column were used to simulate the impact of surfactant contamination on the flotation selectivity of industrial two-stage deinking lines. Simulation results showed that surfactants are slightly removed in the first flotation stage and are concentrated in the second one, where they induce a drop in ink flotation and in fibre entrainment. Subsequently, flotation units in the second stage displayed lower ink removal than in the first stage. In the presence of a constant water reject flow, the increase in surfactant contamination in the pulp stock gave a general decrease in the removal of suspended solids. Surfactant removal increased from 5 to 50%, however, this increase was not sufficient to prevent surfactant accumulation in the deinking line. Simulation results were compared with data collected in an industrial deinking line and particle/surfactant removal efficiencies obtained with low surfactant contamination were in line with experimental data.

A laboratory flotation column equipped with Venturi aerators and an adjustable froth removal system was used to study the effect of an alkyl phenol ethoxylate surfactant on water, particle and surfactant transfer during flotation de-inking of recycled papers. Wash water was not used in order to emphasize the influence of surfactant concentration on water/particle transport in the froth. Surface tension, bubble size and contact angle measurements showed that the increase in surfactant concentration boosted pulp frothing, lowered bubble coalescence and ink/pulp contact angle, thus increasing water hold-up in the froth, gas hold-up in the aerated pulp and depressing ink floatability, respectively. Cross-linked phenomena determining the yield of the flotation process where interpreted using model equations describing particle removal in terms of flotation, entrainment and drainage in the froth. An exponential decrease in the flotation rate constant and in the drainage coefficient of ink, fillers, fine elements and in the fibre entrainment coefficient was observed when increasing the surfactant concentration. Whereas, the surfactant removal rate constant rose, in agreement with the increase in the surface area flux due to a reduction in bubble coalescence.

A laboratory flotation column using Venturi aerators and a vacuum system to remove froth was used to investigate the contribution of gas flow, pulp flow, cell volume and froth retention time on the ink removal efficiency and on cellulose fibres and mineral fillers loss. The increase in the gas flow from 4 to 8 L/min gave a general rise of particle transport from the pulp slurry to the froth with an ensuing strong increase in ink removal, from 75% to 85%, and water and total loss, from 10% to 40% and 15% to 30%, respectively. Whereas, the increase of the cell volume from 14 to 24 L improved ink removal from 72% to 80% without considerably affecting flotation loss. The rise of the froth retention time in the flotation cell from 5 to 20 s before removal gave a general decrease in the flotation loss from 20% to 11% without a corresponding decrease in ink removal. This trend was interpreted as reflecting poor ink drainage through the froth. The increase of both pulp and froth retention time in the flotation cell appeared as the most favourable way to improve ink flotation selectivity. A mathematical model, describing particle removal during flotation in terms of true flotation, entrainment and drainage, was proposed and used to fit experimental data.

This work focuses onto the interactions between poly(ethylene oxide) (PEO) and fatty acids, in order to set their potential role of contaminants for PEO-based retention systems. Surface tension measurements were used to investigate PEO-fatty acid systems and they made it possible to clearly point out the interactions between the polymer and the sodium octadecylcarboxylates with different degrees of unsaturation. The observed interaction seems to be dependent on the fatty acids' solubility, the increase of which leads to less pronounced phenomena, which are, in contrast, emphasized by the increase in PEO chain length.

Microfibrillated cellulose nanoparticles were used as binders for the aqueous processing of flexible electrodes for Li-ion batteries. Microfibrillated cellulose formed a nanostructured web-like network around graphite platelets conferring to the graphite anode a highly porous structure, excellent flexibility and good cycling performances. This work demonstrates that microfibrillated cellulose can be effectively used as a binder element for the manufacturing of self-standing and flexible electrodes using a straightforward water evaporation process.

Biocide programs have become necessary in most fine paper manufacturing circuits, as drastic reduction of fresh water consumption in the industry enhances microbial development. Depending on their chemical nature, biocides may interfere with typical wet-end chemistry additives and furnish. A reference wet-end chemistry was set (including fixing aid, dry strength aid, sizing agent, and retention system), then biocides were added to the furnish (bleached virgin fibres + mineral filler) prior to handsheet making. Four of the tested biocides (organo-sulfur, dibromonitrilopropionamide, isothiazoline, and glutaraldehyde) were not found to interact with wet-end chemistry. On the other hand, the tested quaternary ammonium salt biocide showed very detrimental effects: it reduced filler retention in the sheet, decreased sheet strength, and destroyed sizing (sheet hydrophobicity).

This dissertation describes the chemical modification of cellulosic fibers by organosilanes. The reactions of silanes bearing various functional groups were carried out in pure aqueous solution and followed in-situ by nuclear magnetic resonance spectrometry. The effect of pH, concentration, and temperature on the reaction kinetics was studied. Aminosilanes could be processed in conditions similar to those commonly used in the papermaking. Furthermore, the adsorption of the most promising grafting agents on model cellulose surfaces was investigated by mean of a quartz crystal microbalance, and the effect of the same parameters was evaluated. This study showed that a good surface coverage is attained rapidly, i.e., within only a few minutes. Then, a slower but continuous adsorption was observed over time. The nature of the interactions between various silanes and cellulose was tested. It was shown that the grafting was successfully performed, thus giving rise to the formation of strong interactions between the adsorbate and the adsorbent. Finally, two types of fibers (softwood and hardwood) were used in order to evaluate the effect of organosilanes on mechanical properties and the softness of paper. The results obtained showed quite modest effects, even though the success of the grafting was assessed on both type of fibers.; Ce manuscrit de thèse traite de la modification de fibres de cellulose, en solutions purement aqueuses, par les organosilanes. Les réactions en phase aqueuse de silanes portants différents groupements chimiques réactifs ont été évaluées in-situ par spectrométrie par résonance magnétique nucléaire et l'influence de divers paramètres (pH, concentration, température) a été étudiée. Les aminosilanes se sont montrés particulièrement adaptés à l'utilisation en conditions correspondant à celles couramment utilisées dans le procédé papetier. En outre, l'adsorption des agents chimiques les plus prometteurs sur des surfaces modèles de cellulose a été testée par la technique microbalance à quartz, en fonction des mêmes paramètres. Cette étude a montré qu'une bonne couverture de la surface est atteinte avec des cinétiques de quelques minutes, et a été suivie d'une légère adsorption continue dans le temps. La nature des interactions entre divers silanes et la cellulose a été testée, et a révélé que le greffage, réalisé avec succès dans ce travail, relève d'interactions fortes. Enfin, deux types de fibres (résineux et feuillus) ont été utilisés afin de mesurer le potentiel d'utilisation des organosilanes pour répondre à une problématique industrielle impliquant les propriétés mécaniques du papier et sa douceur. Des résultats mitigés ont été obtenus, bien que le succès du procédé de greffage ait été avéré pour les différentes fibres.

This dissertation describes the chemical modification of cellulosic fibers by organosilanes. The reactions of silanes bearing various functional groups were carried out in pure aqueous solution and followed in-situ by nuclear magnetic resonance spectrometry. The effect of pH, concentration, and temperature on the reaction kinetics was studied. Aminosilanes could be processed in conditions similar to those commonly used in the papermaking. Furthermore, the adsorption of the most promising grafting agents on model cellulose surfaces was investigated by mean of a quartz crystal microbalance, and the effect of the same parameters was evaluated. This study showed that a good surface coverage is attained rapidly, i.e., within only a few minutes. Then, a slower but continuous adsorption was observed over time. The nature of the interactions between various silanes and cellulose was tested. It was shown that the grafting was successfully performed, thus giving rise to the formation of strong interactions between the adsorbate and the adsorbent. Finally, two types of fibers (softwood and hardwood) were used in order to evaluate the effect of organosilanes on mechanical properties and the softness of paper. The results obtained showed quite modest effects, even though the success of the grafting was assessed on both type of fibers., Ce manuscrit de thèse traite de la modification de fibres de cellulose, en solutions purement aqueuses, par les organosilanes. Les réactions en phase aqueuse de silanes portants différents groupements chimiques réactifs ont été évaluées in-situ par spectrométrie par résonance magnétique nucléaire et l'influence de divers paramètres (pH, concentration, température) a été étudiée. Les aminosilanes se sont montrés particulièrement adaptés à l'utilisation en conditions correspondant à celles couramment utilisées dans le procédé papetier. En outre, l'adsorption des agents chimiques les plus prometteurs sur des surfaces modèles de cellulose a été testée par la technique microbalance à quartz, en fonction des mêmes paramètres. Cette étude a montré qu'une bonne couverture de la surface est atteinte avec des cinétiques de quelques minutes, et a été suivie d'une légère adsorption continue dans le temps. La nature des interactions entre divers silanes et la cellulose a été testée, et a révélé que le greffage, réalisé avec succès dans ce travail, relève d'interactions fortes. Enfin, deux types de fibres (résineux et feuillus) ont été utilisés afin de mesurer le potentiel d'utilisation des organosilanes pour répondre à une problématique industrielle impliquant les propriétés mécaniques du papier et sa douceur. Des résultats mitigés ont été obtenus, bien que le succès du procédé de greffage ait été avéré pour les différentes fibres.