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This work was aimed at investigating the potential use of ozone flotation for recovered papers deinking. The mixing characteristics and the bubble size of a Venturi aerated laboratory flotation column were studied in the presence of simplified model systems and of an industrial pulp slurry. Experimental results showed that surfactants dissolved in the pulp slurry stabilized air bubbles while cellulose fibers promoted coalescence. Moreover, bubble buoyancy was sufficient to fluidize the fiber suspension generating perfect mixing. The gas–liquid transfer coefficient of ozone (kLa) estimated from gas hold-up, air bubble size and kLa measured in water was high enough (0.84 1/s) for the complete transfer of ozone in the pulp slurry and the generation of ozone-free gas effluent. With O3 dosage of 0.8 mg O3/mg COD, ozone flotation allowed increasing chemical oxygen demand removal from 41 to 63% with no effect on the ink flotation efficiency, which remained close to that obtained with air flotation, i.e. ∼92%.

Biofilms based on waxy maize and cassava starches (cereal and tuber starch, respectively), plasticized with glycerol were characterized through their crystallinity, dynamic-mechanical behavior (DMA), thermal degradation (TGA), moisture content and water vapor permeability (WVP). X-ray diffraction experiments show that both materials were mainly amorphous, with the waxy starch presenting a discreetly A-type X-ray pattern. Microscopic investigation of the cryo-fractured surfaces supported this observation. The glass transition of the glycerol-rich phase (measured by DMA) occurs at higher temperatures for cassava than for waxy maize starch, suggesting that the dispersion level of glycerol is higher in the former. TGA showed that maize starch has a slightly higher thermal stability than cassava starch, while glycerol interacts more strongly with the last one. The WVP was 18% higher in the case of the cassava starch film.

Steady-state fluorescence emission spectra of various celluloses were measured at an excitation wavelength of 320 nm. Various spectra recorded in the solid state were compared: (1) ECF bleached papers made of hardwood, the anhydroglucose units of which were chemically modified at C1 and C6 or C2 and C3 positions with carboxylic groups; (2) microcrystalline cellulose; (3) cotton linters; and (4) delignified sisal fibers (mercerized or not). Fluorescence emission was quite independent of the carboxylic acid content and average molecular weight (determined by viscosimetry) of the cellulose polymers. Microcrystalline cellulose (Avicel), cotton linters, and mercerized delignified sisal cellulose were acetylated in homogeneous medium (DMAc/LiCl as solvent system) to obtain soluble polymers in dichloromethane for comparison of spectra recorded in the solid and liquid states. Fluorescence of cellulose acetates in solution (CH2Cl2) and in the solid state was compared under similar experimental conditions to non-esterified celluloses in the solid state. The importance of the solid state for fluorescence emission could be demonstrated. Fluorophores are present in minute amounts in the polymer and their favorable energy transfer for excitation in the solid state likely enhances fluorescence emission. Among numerous fluorophores, dityrosine appeared to be a good candidate for fluorescence because it displayed emission in the fluorescence range of cellulose. Dityrosine is an amino acid involved in the lignification of non-woody plants. Mercerized sisal impregnated with tyrosine in the presence of peroxidase and hydrogen peroxide did not show enhanced emission, in contrast to para-hydroxycinnamic acid (coumaric acid), which is also involved in the lignification process at least for non-woody plants. The origin of cellulose fluorescence remains uncertain and appears to have several origins. This study clearly underlines the importance of the solid state for enhancing fluorophore emission.

Model equations and transport coefficients recently used to describe particle and water transport phenomena in a laboratory flotation deinking column were applied to industrial flotation cells and used to simulate multistage flotation systems. The deinking selectivity obtained for a two-stage pre-flotation system was in agreement with data collected in a deinking mill running in similar conditions and process yield, floated pulp composition and ink load in the floated pulp were predicted with good accuracy. Multistage flotation systems with different configurations were simulated, however, only a not conventional three-stage flotation system gave a relevant increase in the ink removal selectivity. Indeed, the addition of a third stage to a conventional two-stage flotation system gave ∼50% decrease in the pulp stock loss and only 10% decrease in ink removal which was recovered by the addition of a flotation cell in the first stage without affecting yield. In general, it was observed that the addition of second and third stages favours the selective removal of particles with the highest flotation rate constant (inks). Indeed, floatable particles, i.e. ink, fillers and fines are mainly removed in the first stage, ink and fillers in the second and ink in the third stage.

In libraries and archives some of the time-acidified items are so brittle that they cannot be handled without risking loss of material. Currently used deacidification processes do not impart improved mechanical properties to the paper. The use of alcoholic solutions of three different types of aminoalkylalkoxysilanes was studied for the deacidification of paper-based items. It was shown that in addition to deacidifying and improving the stability of papers by providing an alkaline buffer the treatment also significantly improved their mechanical resistance, as measured by the folding endurance and tensile breaking resistance. Essential for the appraisal of the deacidification process, the behaviour upon ageing of the materials treated was investigated. Accelerated ageing methods involving heat/humidity and nitrogen dioxide atmosphere were used separately. It was shown that the reinforcement effect of the three aminosilane compounds tested persisted throughout the ageing, and in one case the mechanical properties even improved after ageing. Two of the aminosilanes tested were studied for their impact at the macromolecular level, on the molar masses of cellulose, using size-exclusion chromatography with multiangle light scattering detection. Their effectiveness in protecting paper from acid hydrolysis occurring during ageing was found significant.

Aqueous dispersions of nanometric clay platelets (Laponite) have been dewatered through different techniques: centrifugation, mechanical compression, and osmotic stress (dialysis against a polymer solution). The positional and orientational correlations of the particles have been determined through small-angle neutron scattering. Uniaxial compression experiments produce concentrated dispersions (volume fraction > 0.03) in which the platelets have strong orientational and positional correlations. The orientational correlations cause the platelets to align with their normal along a common axis, which is the axis of compression. The positional correlations cause the platelets to be regularly spaced along this direction, with a spacing that matches the average volume per particle in the dispersion. The swelling law (volume fraction versus separation distance) is one-dimensional, as in a layered system. Changes in the applied osmotic pressure cause the water content of the dispersion to either rise or decrease, with time scales that are controlled by interparticle friction forces and by hydrodynamic drag. At long times, the dispersions approach osmotic equilibrium, which can be defined as the common limit of swelling and deswelling processes. The variation of the equilibrium water content with the applied osmotic pressure has been determined over 1 decade in volume fractions (0.03 < < 0.3) and 3 decades in pressures. This equation of state matches the predictions made from the knowledge of the forces and thermal agitation for all components in the dispersion (particles, ions, and water).

Linters cellulose was subjected to different treatments (mercerization and ionized air) before acetylation with acetic anhydride, in homogeneous medium, using DMAc/LiCl as solvent system. Before derivatization, the treated fibres were characterized by Scanning Electron Microscopy, X-ray diffraction, alpha-cellulose content, Inverse Gas Chromatography and viscosimetry. It was shown that except a decrease in the dispersive surface energy, the treatments induced small changes in the cellulose. The degree of acetylation of these fibers was found to follow a linear behavior with the stoichiometry between acetic anhydride and glucose unit, but this linearity obeyed high rate up to a DS of 2.0. The order of reactivity observed for all samples, C6>>C2>C3, confirms the higher reactivity of OH in C6 position, because this group is the least sterically hindered of the anhydroglucose unity.

Acrylated soybean oil was irradiated in the near UV in the presence of free radical photoinitiators. Given the high substitution density of acrylic moieties, these oils responded very rapidly to the photopolymerization giving high yields of crosslinked materials within a few seconds. The activity of three photoinitiators was compared and the ensuing networks were characterized in terms of crosslink density through swelling measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3218–3221, 2006

The chlorine dioxide reaction with residual lignin of chemical pulp during delignification stage was simulated using phenolic and non-phenolic lignin model compounds applying various amounts of chlorine dioxide. Based on the reaction of model compounds and measurement of inorganic chlorinated species, three reaction phases were established for degradation of lignin model compounds. It was found that after the degradation of free phenolic units, the reaction of primary oxidized products by ClO2 competed with the oxidation of non-phenolic aromatic structure. The results obtained by lignin model compounds were compared with the pulp delignification results. This comparison indicated two special phases for the reduction of the kappa number. The initial phase corresponded to the oxidation of phenolic units without secondary reactions. The second phase corresponded to the oxidation of the non-phenolic units in competing with secondary reactions. The results of this confirmed the over consumption of chlorine dio...

Nanocomposites of cassava starch reinforced with waxy starch nanocrystals were prepared. They showed a 380% increase of the rubbery storage modulus (at 50 °C) and a 40% decrease in the water vapor permeability. X-ray spectra show that the composite was more amorphous than the neat matrix, which was attributed to higher equilibrium water content in the composites. TGA confirmed this result and its thermal derivative suggested the formation of hydrogen bonding between glycerol and the nanocrystals. The reinforcing effect of starch nanocrystals was attributed to strong filler/matrix interactions due to the hydrogen bonding. The decrease of the permeability suggests that the nanocrystals were well dispersed, with few filler/filler interactions. Fil: Garcia, Nancy Lis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Polímeros y Materiales Compuestos; Argentina Fil: Ribba, Laura Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Polímeros y Materiales Compuestos; Argentina Fil: Dufresne, Alain. Grenoble Institute of Technology; Francia Fil: Aranguren, Mirta Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Goyanes, Silvia Nair. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física. Laboratorio de Polímeros y Materiales Compuestos; Argentina

The present investigation focuses on the adsorption of cationic photoluminescent polymer nanoparticles on negatively charged bleached softwood cellulose fibres. The synthesis of the copolyfluorene–fluorenone and its miniemulsification with tetradecyltrimethylammonium bromide (TTAB) as surfactant has been optimized to obtain highly charged cationic nanoparticles. Cellulose pulp beating was performed as mechanical treatment to increase fibres hydration and specific surface area. Although beating promoted nanoparticles adsorption, photoluminescence of handsheets prepared with beaten fibres was less intense comparing to those obtained with untreated fibres. The photoluminescence drop was attributed to the loss of a large fraction of cellulosic fine elements present in the beaten pulp during handsheets preparation. Cationic nanoparticles adsorption kinetics on cellulose fibres and the resulting photoluminescence efficiency was monitored in two cases: with or without the stabilization of nanoparticles in the pulp slurry by TTAB. Pulps preconditioning with TTAB avoided nanoparticles flocculation and led to a homogeneous coverage of the fibres surface giving more efficient photoluminescent papers. However, the formation of a continuous layer on the fibre surface induced a drop in the mechanical resistance of the paper which was ascribed to a decrease of interfibre hydrogen bonding.

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.

Two cellulosic substrates (microcrystalline cellulose, MCC, and bleached kraft softwood pulps, BSK) were grafted by polycaprolactone (PCL) chains with different molecular weights, following a three-step procedure using non-swelling conditions in order to limit the reaction to their surface. First, one of the two OH PCL ends was blocked by phenyl isocyanate and the reaction product (adduct 1) was subsequently reacted with 2,4-toluene diisocyanate (adduct 2) to provide it with an NCO function, capable of reacting with cellulose. The ensuing PCL-grafted cellulosic materials were characterized by weight gain, elemental analysis, contact angle measurements, attenuated total reflexion–Fourier transform infrared (ATR–FTIR), X-ray photoelectron spectroscopy (XPS) and biodegradation tests. The modification was proven to occur by the presence of nitrogen atoms in the elemental analysis tests and XPS spectra of modified and soxhlet-extracted cellulose. The contact angle measurements have also shown that the surface became as hydrophobic as PCL itself. The polar component of the surface energy of cellulosic substrates before treatment was found to be about 32 and 10 mJ m −2 , for MCC and BSK, respectively. This value vanished to practically zero after grafting with different PCLs. The strategy proposed in the present work is original since, to the best of our knowledge, this paper reports for the first time the chemical “grafting onto” of the cellulose surface by PCL macromolecular structures, with the aim of obtaining fibre–matrix co-continuous fully sustainable and biodegradable composite materials.

A general procedure to increase the amount of photoreactive chromophore groups per oligoether chain is presented. In this work, a photoreactive macromonomer with four functionalities was synthesized by a four-step synthetic pathway with high yield. The photochemical behavior of this compound was studied with a view to obtaining polymeric networks. The significant advantage in this strategy is that the preparation of this material has as last operation, the obtaining and processing of polymer as thin film. In this way, the synthetic strategy based on assembling: (i) the polyether chains, (ii) a film forming backbone, and (iii) a photoactive moiety to be used for cross-linking, seems a viable solution to the problem of the continuous processing of materials. Fil: Froimowicz, Pablo. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología En Polimeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología En Polimeros y Nanotecnología; Argentina Fil: Belgacem, Naceur. Grenoble Institute Of Technology; Francia Fil: Gandini, Alessandro. Grenoble Institute Of Technology; Francia Fil: Strumia, Miriam Cristina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina

Several approaches to the modification of cellulose fibres are described, namely: (i) physical treatments such as corona or plasma treatments under different atmospheres; (ii) grafting with hydrophobic molecules using well-known sizing compounds; (iii) grafting with bi-functional molecules, leaving one of the functions available for further exploitation; and (iv) grafting with organometallic compounds. The modified surfaces were characterized by elemental analysis, contact angle measurements, inverse gas chromatography, X-ray photoelectron and infrared spectroscopy, wettability, etc. These different tools provided clear-cut evidence of the occurrence of chemical reactions between the grafting agent used and the hydroxy functions of the cellulose surface, as well as of the existence of covalent bonding in the ensuing composite materials between the matrix and the fibres through the use of doubly reactive coupling agents.

This study presents new and improved semi-empirical mathematical models for all the chlorine dioxide stages and extraction stages (including oxygen and/or peroxide reinforced) incorporated in a full Elemental Chlorine Free (ECF) bleaching sequence simulator developed in EFPG. The simulator predicts variations of Kappa number, pH, brightness, bleaching chemical consumption and COD at each step of multistage ECF bleaching sequences. The first purpose of this work was to improve kinetic and stoichiometric equations, involved in the chlorine dioxide stages (Do, D1, D2), for their predictability for different kinds of softwood and hardwood pulps. The second purpose was to model the extraction stages with or without oxygen and/or hydrogen peroxide reinforcement (E, EO, EOP, EP). The results predicted fit very closely to a wide range of laboratory and mill bleaching data and the predictability was extended to a greater variety of pulps (softwoods and hardwood pulps, kraft or other alkaline pulps).

Publisher Summary The main emphasis of this chapter has to do with the shift from the traditional ways of treating woods in order to improve their resistance to atmospheric and biological degradation, to chemical modifications which eliminate the problem of leaching of toxic materials into the environment. Hence, recent contributions on the chemical modification of wood by different physico-chemical treatments, such as corona and plasma discharges, or its chemical grafting through esterification, etherification, as well as urethane and siloxane formation and the reaction of wood with furfuryl alcohol, are reviewed and discussed. The chapter also covers the topic of the preparation and characterization of composite materials made of wood fiber and polymeric matrices. These surface or bulk treatments point to the relevance of a novel green approach and show that very promising results can be obtained.

Publisher Summary Environmental issues have recently generated considerable interest in the development of composite materials based on renewable resources such as natural fibers as low cost alternatives for glass fibers. A large number of interesting applications are emerging for these materials. In Europe, the emphasis is on the automotive industry which is looking into the use of plant fiber-based composites as a way to serve the environment and at the same time save weight (and therefore fuel). In North America, wood fiber-based composite building materials have been developing for some time. In India and South America, jute and sugar cane fibers are used in low cost housing. Wherever the industry, there will be a locally grown lignocellulosic fiber to suit the application. In addition, natural fiber present a multi-level organization and consist of several cells formed out of semi-crystalline oriented cellulose microfibrils that open opportunities in the field of nanoscience and nanotechnology.

Publisher Summary This chapter summarizes the most recent advances in the realm of the modification of vegetable oils aimed at their use in the preparation of polymeric materials. After a brief description of the most important industrial oils, their major sources, their worldwide production, some of their properties and isolation procedures are reviewed. This chapter also discussed the crosslinking of oils by vinyl monomers and by metal-catalyzed reactions, the formation of interpenetrating networks, the modification of epoxidized and castor oils, and the polymerization of the resulting products. Subsequently, different oil-based polyurethanes, polyamides, polyester-amides, alkyd resins and, polyesters and poly(hydroxyalkanoates) are reviewed. With each family of oil-based polymers, the most promising materials and their relevant properties are singled out stressing their suitability to replace, at least partially, petroleum-based counterparts.

Publisher Summary This chapter describes the partial and total oxypropylation of various natural polymers and more complex biomass substrates and the use of the ensuing materials as composites or polyol macromonomers, respectively. The total oxypropylation of different lignins, sugar beet pulp, cork, chitin and chitosan, and olive pits is then reviewed in terms of its success in converting all these substrates into viscous polyol mixtures, which can be used to prepare polyurethane foams with thermal insulating properties similar to those of conventional industrial counterparts. Finally, this chapter deals with the superficial oxypropylation of cellulose fibers and starch granules (i.e. reactions limited to a certain thickness of the substrates) so that the ensuing materials keep their original morphology and properties, but now possess a thermoplastic shell which enables their conversion to single-component composites by simple thermal processing.

The delignification of pulp in a conventional batch reactor provides convenient conditions for inutile secondary reactions in which ClO2 reacts with oxidized aromatic units of lignin. In this study the flow-through reactor was applied to minimize secondary reactions. The obtained results showed that the removal of oxidized lignin from the reaction zone significantly enhanced the ClO2 reaction toward non-oxidized units of lignin. Application of an organic solvent-water solution, bleaching liquor, significantly increased the removal of oxidized lignin and decreased considerably the secondary reactions. Although this technique considerably improved ClO2 effective efficiency, large amounts of chlorate formation decreased the overall effect of improved ClO2 global efficiency.

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 batch kraft cooking non-isothermal digester was modelled based on chemical kinetics and mass transfer equations for softwood. Kraft pulping modelling had been designed for non-isothermal batch cooks of chip mixtures: either mixed-size chips, according to a thickness distribution law, or mixtures of different wood species. The case of existing linear or non-linear radial temperature gradients in a digester was examined. Several chip populations with different thickness distribution were used: normal (major abundance of 3-5 mm chips); uniform (equal abundance of chips in the range 3-12 mm); Gaussian-type (centred on 7 mm chips); Poisson-type (major abundance of 3 mm chips). The effect on cooking results due to temperature gradients in digester was predicted along with the existing non-uniformity arising from the effect of chip size distribution, density, and wood mixtures of different composition and chemical properties (rate constants, activation energies). Results are presented as a kappa number, yield and rejects distributions and mean values. The rather sharp kappa number distributions obtained for isothermal cooks were found to be severely spread in the linear temperature gradient case. The above effects were attenuated when a central core in the digester was kept isothermal. The stratification of chips resulted in significantly reduced width in kappa number distributions. Highest density chips cooked lower; however, since diffusion effects were more prominent in them, their apparent activation energy was also less. So they were slightly less affected by temperature gradients in the digester. Cooking different wood species together also affected the spread of the kappa number distribution. This cumulated more or less to temperature gradients effects, depending on chemical activation energy data and possible differences between species.

Publisher Summary This chapter provides the information on usage of lignin, as such or after modification, as an additive to other polymers, a blend component, and a macromonomer. After a brief description of the use of lignin as a filler in different polymeric vehicles, such as inks and paints, the use of this renewable macromolecule as a co-reactant in phenol–formaldehyde, and urea–formaldehyde resins, is described. Then, different systems aiming at preparing poly(urethane)s, polyesters, epoxy resins, and resins based on lignins and furans are reviewed, and those giving the most interesting materials discussed in some depth. The modification of lignin with alkenyl groups and the polymerization of the ensuing macromonomers are also critically assessed. The following topic is the preparation of lignin-based carbon fibers and activated carbons and their use as reinforcing elements in composites and selective adsorbents, respectively. Finally, the preparation of aromatic monomers from lignin and the interest of their polymers is discussed.

This paper proposes new mathematical models for the prediction of chemical oxygen demand (COD) from different stages in full ECF bleaching sequences and discusses several important issues related to model development and interpretation. The effects of different process conditions, like pH, chemical charge, initial Kappa number, carryover, temperature etc., on the formation of COD from the different chlorine dioxide stages (Do, D1, D2) and extraction stages (E, EO, EP, EOP) were studied and corresponding models were developed for softwood and hardwood pulps. The models, based on results obtained from the extensive studies of the kinetics, stoichiometry, and effluent properties of the chlorine dioxide stages and extraction stages in the ECF bleaching of pulp, were tested for accuracy on a vast range of data both from literature and laboratory experiments. The kinetics, stoichiometry and effluent properties have not previously been considered together for optimization and would be of considerable use in bleach plant optimization as well as in process control of different stages. This study will also help in understanding the need for modifications of the conventional conditions in both the chlorine dioxide and the extraction stages to obtain the best mix between a low formation of COD and high bleaching efficiency.

Nanocomposites films have been processed from a filler and a matrix having the same nature, i.e. waxy maize starch. The filler consists of nanoplatelet-like starch particles obtained as an aqueous suspension by acid hydrolysis of starch granules and the matrix was prepared by plasticization and disruption of starch granules with water and sorbitol. Nanocomposite films were obtained by casting and evaporating the mixture of the aqueous suspension of starch nanocrystals with the gelatinized starch. The resulting films were conditioned before testing and the effect of accelerated ageing in moist atmosphere was investigated. The thermal properties of the nanocomposite films were determined from DSC measurements and the mechanical characterization was performed in both the linear and nonlinear range.

Aqueous suspensions of polysaccharide nanocrystals can be prepared by acid hydrolysis of natural resources, such as cellulose, chitin and starch. The object of this treatment is to dissolve away regions of low lateral order so that the water–insoluble, highly crystalline residue may be converted into a stable suspensoid by subsequent vigorous mechanical shearing action. When using cellulose or chitin, the resulting nanocrystals occur as rod–like particles or whiskers, which dimensions depend on the nature of the substrate, while in the case of starch the nanocrystals appear as platelet–like nanoparticles. During the last decade we have attempted to mimic biocomposite by blending polysaccharide nanocrystals from different sources with polymer matrices, including synthetic and natural ones. Casting mixtures of polysaccharide nanocrystals and lattices led to composites with drastically enhanced mechanical properties, especially at T ? Tg of the matrix, by virtue of the formation of a whiskers network, even when the whisker volume fraction was only a few percent. The formation of this rigid network, resulting from strong interactions between whiskers was assumed to be governed by a percolation mechanism. This hydrogen–bonded network induced a thermal stabilisation of the composite up to 500 K, the temperature at which polysaccharides start to decompose. A new and promising way of nanocomposite processing consists in transforming polysaccharide nanocrystals into a co–continuous material through long chain surface chemical modification. It consists in submitting polysaccharide nanocrystals to surface chemical modification based on the use of grafting agents bearing a reactive end group and a long compatibilising tail.

A fast and semi-quantitative wet chemical method was developed for the titration of free phenolic groups in residual lignins of pulps. The method is based on selective chlorine dioxide reaction with phenolic units of lignin at 0°C. A known amount of ClO2 is reacted for up to 30 min with various substrates and ClO2 consumption is measured. Experiments with monomeric lignin-like model compounds, a dioxane/HCl lignin (isolated from kraft pulp), kraft pulp, and one thermomechanical pulp (TMP) were performed. The ideal stoichiometric consumption of 1 mol of ClO2 per Ar-OH was approximated in a few cases. More model compound experiments are necessary to establish the possibilities and limitations of the method, but the results of these preliminary experiments are promising. First studies on pulps and comparison of the data with those obtained by 13C NMR analysis on dioxane/HCl lignins showed some deviations in the first instance, which were attributed to reaction of the intermediates HClO and Cl2 involved in the overall mechanism. However, using DMSO as HClO trapping agent improved the ClO2/Ar-OH stoichiometric ratio close to the theoretical value of 2, which essentially yielded better results. This improved stoichiometry was verified for three model compounds, one kraft pulp and one TMP, yielding results were similar to those obtained by 13C NMR analysis.

Monocrystalline starch nanoparticles were successfully grafted with poly(tetrahydrofuran), poly(caprolactone), and poly(ethylene glycol) monobutyl ether chains using toluene 2,4-diisocyanate as a linking agent. Surface grafting was confirmed using Fourier transform infrared and X-ray photoelectron spectroscopies, differential scanning calorimetry, elemental analysis, and contact angle measurements. Transmission electron microscopy observations of modified starch nanocrystals showed either the individualization of nanoparticles or the formation of a film, depending on the polymer used. It was shown that grafting efficiency decreased with the length of the polymeric chains, as expected. The resulting modified nanoparticles can find applications in the field of co-continuous nanocomposite materials.

Sisal nanowhiskers were used as novel reinforcement to obtain nanocomposites with polyvinyl acetate (PVAc) as matrix phase. They are seen as attractive materials due to the widespread availability and low cost of the sisal source material. Statistical analysis of the sisal whisker length and diameter resulted in average values of 250 nm and 4 nm, respectively, resulting in an average aspect ratio in the upper range of reported cellulose nanowhisker values. The high aspect ratio ensures percolation, with resulting mechanical improvements and thermal stability, at lower fiber loads. Water uptake and thermal behaviour of the sisal whisker–PAVc composites were studied. Whisker addition was found to stabilize the nanocomposites with no benefit seen when increasing the whisker content beyond the percolation threshold: For all whisker contents studied above percolation, the water uptake stays constant, and the Tg does not vary with whisker content at a given relative humidity. The water diffusion rate however increases due to water accumulation at the whisker–PVAc interface. Below whisker percolation, stabilization is only noticed at low relative humidity, whereas high humidity results in disruption of whisker–PVAc interactions. This work shows the potential of cellulose nanowhiskers to stabilize polar polymers even at high humidity conditions with minimal reinforcement addition.

Le thuya de Berbérie « Tetraclinis articulata Vahl », espèce résineuse endémique d’Afrique du Nord se trouve généralement sous forme de taillis. La valorisation de la biomasse de thuya, et en particulier de son bois peut être envisagée par la filière papetière par le biais d’une cuisson soude en présence d’anthraquinone (AQ). Le bois jeune de thuya (20 ans) se délignifie bien à l’aide d’une cuisson soude-anthraquinone dans les conditions habituellement appliquées aux résineux avec un temps total de cuisson de 145 min et une température de palier de 165 ◦C. Le rendement brut obtenu est égal à 43,3 % avec un indice Kappa de 33,6. Dans les mêmes conditions de cuisson, le bois âgé (60 ans) peut être lessivé mais se délignifie moins facilement., The coniferous trees of the thuya de Berbérie (Tetraclinis articulata Vahl), from the North Africa (Algeria) is commonly grown as a coppice stand. The biomass of thuya, and especially its wood, can be transformed in pulp by the paper and pulp industry throughout the soda cooking process with the help of the anthraquinone (AQ). The young wood (20 years-old) is well delignified in the soda–anthraquinone process, in the usual conditions applied to the resinous species, in the cooking time schedule of 145 min with the level of 165 ◦C of temperature. The pulp yield of raw material obtained is 43.3% (oven dried wood), with a kappa number of: 33.6. In the same cooking conditions, the mature wood (60 years-old) can be also treated, but with some lower delignification level.

There are numerous examples where animals or plants synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by fibrous biopolymers. Cellulose and chitin are classical examples of these reinforcing elements, which occur as whisker-like microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, with the consequence of axial physical properties approaching those of perfect crystals. Starch is another example of natural semicrystalline polymer that is produced by many plants and occurs as microscopic granules. It acts as a storage polymer in cereals and tubers. These abundant and natural polymers can be used to create high performance nanocomposites presenting outstanding properties. Aqueous suspensions of crystallites can be prepared by acid hydrolysis of the purified substrates. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspension by subsequent vigorous mechanical shearing action. For cellulose and chitin, these monocrystals appear as rod-like nanoparticles which dimensions depend on the biological source of the substrate. In the case of starch they consist of platelet-like nanoparticles. High reinforcing capability was reported resulting from the intrinsic chemical nature of these polymers and from their hierarchical structure. During the last decade, many works have been devoted to mimic biocomposites by blending cellulose whiskers from different sources with polymer matrices.

International audience; Waxy maize starch nanocrystals obtained by hydrolysis of native granules were used as a reinforcing agent in a thermoplastic waxy maize starch matrix plasticized with glycerol. Compared to our previous studies on starch nanocrystals reinforced natural rubber (NR) [Macromolecules 2005, 38, 3783; 2005, 38, 9161], the present system presents two particularities: (i) thermoplastic starch is a polar matrix, contrarily to NR, and (ii) the chemical structures of the matrix and the filler are similar. The influence of the glycerol content, filler content, and aging on the reinforcing properties of waxy maize starch nanocrystals (tensile tests, DMA) and crystalline structure (X-ray diffraction) of materials were studied. It was shown that the reinforcing effect of starch nanocrystals can be attributed to strong filler/filler and filler/matrix interactions due to the establishment of hydrogen bonding. The presence of starch nanocrystals leads to a slowing down of the recrystallization of the matrix during aging in humid atmosphere.

Starch nanocrystals obtained from acid hydrolysis of waxy maize starch granules consist in crystalline nanoplatelets about 6-8 nm thick with a length of 20-40 nm and a width of 15-30 nm. New nanocomposite materials, i.e. natural rubber (NR) filled with waxy maize starch nanocrystals were processed by casting. Dynamic mechanical analysis has shown that starch nanocrystals were a good reinforcing agent for NR at temperatures higher than the glass transition temperature of NR. Tensile tests have shown that until a weight fraction of 20 wt%, this new filler presented the advantage to reinforce natural rubber without decreasing significantly the strain at break of the material. These properties may be due to both the morphological nature of starch nanocrystals, and the formation of a percolating starch nanocrystals network within the NR matrix, resulting from hydrogen bonding forces between starch aggregates.

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.

The reaction of chlorine dioxide with different types of lignin model compounds was investigated in order to compare the kinetics and to evaluate the amount of oxidant consumed by the different substrates. Complete reaction of lignin model compounds was observed at ClO2‐to‐substrate molar ratios of 0.9–1.2, which corresponds to an electron transfer varying between 5–6 equivalents per mole of substrate. Muconic acid derivatives also fully reacted, at a ClO2‐to‐substrate molar ratio of 1.2, with the oxidant consumption being about 4 equivalents per mole of substrate. The reaction of mixtures of phenolic, non‐phenolic, and muconic acid type substrates showed that the reaction rates of non‐phenolic and muconic acid type substrates were rather similar. This study suggests that further reaction between ClO2 and the primary lignin oxidation products, such as muconic acid type structures could be the cause of overconsumption of oxidant in a D stage.

Fluorinated copolymers are well known for their large range of applications. These applications can be improved by grafting or crosslinking of several agents. The mechanism of crosslinking of hexamethylene diamine and 2,4,4-trimethyl-1,6-hexanediamine is well known and occurs in four different steps. To elaborate a film of commercially available poly(VDF-co-HFP) copolymer crosslinked by 2,4,4-trimethyl-1,6-hexanediamine, a step of press cure under air is necessary. Temperature, time and pressure were optimised by regarding the solubility of the press cured films, the mechanical properties, the swelling rate in methyl ethyl ketone, and the degradation of the films. The best temperature, time and pressure for press cure were 150 °C, from 15 to 30 min, and 20 bars, respectively. Other properties of crosslinked poly(VDF-co-HFP) copolymers containing 10 mol.% and 20 mol.% of HFP were characterized. First, all films were insoluble in concentrated HCl. Secondly, swelling rates of different amounts of diamine crosslinked copolymers were measured in ethylene carbonate/dimethyl carbonate and in methyl ethyl ketone; it was proved that the higher the molar percentage of diamine, the higher the crosslinking density, so the lower the swelling rate. Concerning thermal properties, glass transition temperature mainly increased when the amount of diamine increased. Thermal stability measurements showed a higher decomposition temperature when the percentage of diamine was very low (5 mol.%). Finally, mechanical properties were measured by dynamic mechanical analysis; the storage tensile modulus ( E ′) of a diamine crosslinked Kynar ® copolymer versus temperature exhibited a high drop because Kynar ® was a highly amorphous copolymer. Moreover, the higher the amount of diamine, the higher the rubbery modulus.

This paper describes the impact of low frequency (20 kHz) ultrasound (US) on Cd(II)/Zn cementation implemented on a RDE geometry. With and without US the reaction is mass-transfer controlled with two-step first-order kinetics mainly connected to deposit evolution. US improves the kinetics but to a lower extent than expected from electrochemical Cd(II) reduction. The favourable turbulence enhancement due to the deposit without US is not present when applying US because the deposit is continually removed from the surface. The influence of parameters such as temperature, initial concentration of reactants and US power is also analysed.

Several data relative to the viscosity of water-soluble polysaccharide solutions were collected from the literature and processed by different rheological models. Some relationships between the viscosity of these polymer solutions, their molecular weight and their solution concentrations, were established and their validity checked. Thus, an accurate equation correlating the viscosity and both the shear rate and the solution concentration of different water soluble polysaccharides (xanthan, hyaluronan, carboxymethylcellulose) was deduced on the basis of Cross' model which suggests two domains in which the viscosity is constant, i.e. very low and very high shear rate ranges. Then, an expression relating the zero-shear viscosity ( A ) and the concentration of their solutions was proposed. Finally, an alternative equation to that of Mark–Houwink correlating the molecular weight and the intrinsic viscosity of the water-soluble polysaccharides studied in this paper was found.

Lignins from kraft and mechanical pulps were isolated before and after oxygen treatment with conventional methods (acidolysis and enzymatic isolation) and with a novel two-step method combining an enzymatic treatment and acidolysis. Results showed that the combined enzymatic hydrolysis-acidolysis made it possible to extract lignin from pulp with a better yield than acidolysis alone and with a higher degree of purity than after enzymatic hydrolysis alone. The lignin samples isolated with the two-step method were analysed by 13C NMR, 19F NMR and by gel permeation chromatography. It was shown that the behaviour of mechanical pulp lignin during oxygen treatment was different from that of kraft pulp lignin. Most of these differences could be explained by the lower phenolic content and larger molecular size of the mechanical pulp lignin. As a consequence, oxygen had a poor delignifying effect. Finally, 19F NMR spectroscopy showed that oxygen could destroy some quinones induced by the alkaline conditions of the O stage.

The surface of waxy maize starch nanocrystals obtained from sulfuric acid hydrolysis of native waxy maize starch granules was chemically modified using two different reagents, namely, alkenyl succinic anhydride and phenyl isocyanate. The occurrence of chemical modification was evaluated by FTIR and X-ray photoelectron spectroscopies. Contact angle measurements from which the surface energy of the materials under investigation was deduced showed that chemical modification led to more hydrophobic particles. Chemical modification altered the morphology of particles, as shown by observation by transmission electron microscopy, but not their crystallinity (X-ray diffraction analysis).