December 12, 2011 - Fluid Mechanics, Energetics, Processes[Thesis online] Ph.D. title Use of cellulose for the elaboration of photoluminescent or conductive materials. Supervision Didier CHAUSSY, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Davide BENEVENTI, CNRS Researcher, LGP2 Abstract The context of this project is the cellulosic material functionalization in the printed electronic domain. The first part of the thesis work highlighted the printability of aqueous dispersion of semiconducting photoluminescent polymer nanoparticles. The influence of the size and the composition of the particles on the emission colour was studied. Security paper is one of the main potential application of these particles. The second part dealed with the use of cellulose microfibrills and copper microparticles for the elaboration of conductive composite films. The films were self-supporting thanks to the high mechanical properties of the microfibrills. A study on the effect of calendaring pressure and temperature on electric conductivity was carried out, demonstrating that the composite film conductivity can be increased from the 10 S/m of the pristine film up to 70000 S/m. Other members of the jury Stéphanie BRIANCON, Professor, Université Claude Bernard Lyon 1 ♦♦ Roberta BONGIOVANNI, Associate Professor, Politecnico di Torino (Italy) ♦♦ Nathalie DESTOUCHES, Professor, Université Jean Monnet (Saint-Étienne) ♦♦ Paul PIETTE, Manager UST9, Centre Technique du Papier
Déborah LE CORRE
October 27, 2011 - Materials, Mechanical, Civil Engineering, Electrochemistry[Thesis online] Ph.D. title Starch nanocrystals: preparation and application for bio-based flexible packaging. Supervision Alain DUFRESNE, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Julien BRAS, Associate Professor, Grenoble INP-Pagora / LGP2 Abstract The present work investigates the potential of starch nanocrystals (SNCs) for industrial scaled-up preparation and use. An extensive characterization (morphology, viscosity, thermal stability and properties in nanocomposite) of 5 different SNCs shows, contrary to nanocrystalline cellulose, the limited influence of the botanic source. The analysis of the current preparation process led to three optimization strategies, and to the definition of a new generation of SNCs with smaller dimensions and more homogeneity. A new application of SNCs is presented (multilayer packaging); and showed that SNCs can effectively reduce water vapor permeability of some biopolymers coatings. The life cycle assessment (LCA) of SNCs in this application is also proposed. This study contributes greatly to the advancements of the field and offers perspectives for the industrialization of SNCs. Other members of the jury Eliane ESPUCHE, Professor, Université Claude Bernard Lyon 1 ♦♦ Denis LOURDIN, Research Director, INRA - Patrice DOLE, Regional Director, CTCPA ♦♦ Hélène ANGELLIER-COUSSY, Associate Professor, Université de Montpellier 2 ♦♦ David GUERIN, Research Unit Manager, Centre Technique du Papier ♦♦ Timo MAKARAINEN, Manager of R&D Projects, Cargill
September 23, 2011 - Materials, Mechanical, Civil Engineering, Electrochemistry Ph.D. title Rheology of concentrated fibre suspensions : Application to polymer composite forming. Supervision Denis FAVIER, Professor, Université Joseph Fourier (Grenoble) ♦♦ Laurent ORGEAS, Researcher CNRS, Laboratoire 3S-R ♦♦ Pierre DUMONT, Associate Professor, Grenoble INP-Pagora / LGP2 Abstract This study focuses on the processing of composite materials reinforced with short fibres or fibres bundles such as SMC or BMC. Firstly, an experimental work was carried-out at the macroscopic scale. This work led to the development of a lubricated compression rheometer and associated analysis methods to better characterize the rheology of SMC and BMC compounds, by accounting for the compressibility of compounds and the possible friction between the rheometer wall and the flowing composite. Numerical simulation was then achieved in order to simulate the forming of a BMC. For that purpose, the constitutive parameters of a simple tensorial rheological model were determined from experimental data obtained with the rheometer. Finally, an experimental work at the microscopic level allowed (i) the microstuctures of SMC models from X-ray microtomography micrographs and (ii) fibre pull-out experiment to be characterized, and the interaction mechanisms between the fiber bundles forming the fiber reinforcement of these materials to be modelled. Other members of the jury Véronique MICHAUD, Professor, École Polytechnique Fédérale de Lausanne (Swiss) ♦♦ Gilles AUSIAS, Associate Professor, Université de Bretagne-Sud ♦♦ Steven LE CORRE, Professor, Université de Nantes
Aymen BEN MABROUK
July 25, 2011 - Fluid Mechanics, Energetics, Processes[Thesis online] Ph.D. title Chemical modification of cellulose nanofibers by grafting polymer chains in order to prepare high performance nanomaterials. Supervision Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Sami BOUFI, Professor, University of Sfax, Tunisia Abstract A stable aqueous nanocomposite dispersion containing cellulose whiskers and a polymer matrix was prepared via miniemulsion polymerization. We were able to prepare a stable dispersion with a 250 wt % solid content and a cellulose whiskers content ranging from 1 up to 5 wt % based on polymer content. Cellulose nanocrytals suspension was mixed with monomers phase in presence of anionic or cationic surfactant and a stabilizing additive acting as a hydrophobe. After sonication for a short time to obtain a stable emulsion of small droplet polymerisation reaction was trigged by the addition of the initiator. The nanocomposite dispersion was characterized using dynamic light scattering, ζ-potential measurement, transmission electron microscopy (TEM), atomic force microscopy (AFM) and FE-SEM. It was found that the particle size of the prepared suspensions is in the range of 90-600 nm, and the final nanocrystals composite is stable for months.Films obtained by casting followed by water evaporation and particle coalescence were analyzed by differential scanning calorimetry, dynamic mechanical analysis, and tensile testing. The nanocomposite maintained high transparency, and their storage elastic modulus increased tediously with the increasing nanowhiskers content. Other members of the jury Ali KALLEL, Professor, University of Sfax, Tunisia ♦♦ Mustapha MAJDOUB, Professor, University of Monastir, Tunisia ♦♦ Alessandro GANDINI, Professor, University of Aveiro, Portugal ♦♦ Albert MAGNIN, CNRS Research Director, Grenoble
June 23, 2011 - Fluid Mechanics, Energetics, Processes[Thesis online] Ph.D. title Experimental study and CFD simulation of the flow of model fluids and coating colours in a slide die curtain coater. Supervision Véronique MORIN, Research Director, & David GUERIN, Research Unit Manager, Centre Technique du Papier ♦♦ Martine RUEFF, Ingénieur de Recherche, Grenoble INP-Pagora / LGP2 Abstract Curtain coating is a contactless coating process which permits a contour coating of the paper and the key parameter of this process is a perfect stable curtain. This technology is expected to spread widely for graphic paper grades and boards in the next few years. Nevertheless, the observations sometimes show defects of regularity of coating which could be connected to instabilities of flow. In this work, we performed CFD simulations both for Newtonian and Non-Newtonian fluids on the internal flow in a pilot curtain coater and on the flow down the inclined plane. The CFD study of the internal flow revealed the cause of vortex creation into the coater. To maintain vortex-free operation, the Reynolds number at the inlet must remain below a critical value whatever the fluid, which is equal to 20 with the studied geometry whatever the studied fluid. Moreover, a second cavity is useful since instabilities coming from the first cavity could be filtered for low shear-thinning fluids, which is the case of the WFC coating colours. These simulation results were validated thanks to flow visualization experiments with tracers and PIV using a transparent replica of the coater. Finally CFD simulations on the inclined plane were carried out and permitted to conclude that for the range of operating conditions used on the pilot curtain coater, some issues presented in literature should not exist industrially. Other members of the jury Didier CHAUSSY, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Raj CHHABRA, Professor, Indian Institute of Technology Kanpur (India) ♦♦ Samuel SCHABEL, Professor, Technische Universität Darmstadt (Germany) ♦♦ Yann COUILLAUD, Account Manager, Allimand
January 20, 2011 - Fluid Mechanics, Energetics, Processes Ph.D. title Understanding and modelling of the mechanisms of flotation applied to the de-inking of recovered papers. Supervision Patrice NORTIER, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Davide BENEVENTI, CNRS Researcher, LGP2 Abstract Flotation is the main step of de-inking to remove the ink from the pulp. Whereas the target is toremove 2% of ink from the pulp, there is a loss of 20% of total matters (fibers, fillers and ashes). Theflotation process is the only process allowing to more or less selectively separate the particles frominks during recycling of recovered papers. This process is applied by all the European deinking millsand, although being recognized as being the most selective, it generates solid losses which remainstill too important (15 to 20% of losses) compared to the 2% of ink in weight applied to printed papers.Thus, the selectivity of flotation requires to be improved. Such improvement would at the same timeallow to increase the deinking process yield but also to reduce in parallel the volumes of sludgegenerated during de-inking and thus to simplify all the problems connected with the valorisation ofthese sludges. On the one hand, the objectives of this study are to improve fundamental knowledge ofthe phenomena occurring during flotation, in particular to obtain a better knowledge i) on mechanismsof transport of the various particles (ink, fibres and fines cellulose, mineral loads) during flotation in thepresence of various surface-active components from de-inking, ii) of the role of surface-activesubstances and their elimination during flotation. On the other hand, modelling of the mechanisms oftransport in the pulp and in the froth, taking into account mechanical parameters (air ratio, turbulence,design of the cells) and physico - chemical parameters has been highlighted to finally develop asimulation of the flotation process allowing to evaluate the incidence of the design of the cells,simulation which should then make it possible to improve the effectiveness of the existing cells. Other members of the jury Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Maria ANGELS PELACH, Professor, Universitat de Girona (Spain) ♦♦ Edouard PLASARI, Professor, ENSIC (Nancy) ♦♦ Marc SANQUER ♦♦ Bart VAN TIGGELEN - Régis DE GAUDEMARIS ♦♦ Pierre EYMARD BIRON ♦♦ Françoise MASSINES.