CNRS Structural Engineering

Grenoble, France

CNRS Structural Engineering

Grenoble, France
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Santucci B.S.,CNRS Structural Engineering
TAPPI International Conference on Nanotechnology for Renewable Materials 2015 | Year: 2015

Project Context; Brazilian Context: Why Sugarcane Bagasse?; Evaluation of Physico-Mechanical Treatments on Sugarcane Bagasse Cellulose Hydrolysis; Nanofibrillated Cellulose from Mechanically- and Enzymatically Treated Sugarcane Bagasse Pulp; Conclusions.

Boufi S.,University of Sfax | Gandini A.,CNRS Structural Engineering
RSC Advances | Year: 2015

Nanofibrillated cellulose (NFC) from biomass has become a subject of intense research activity owing to its attributes of nanosized cellulose and sustainable character. However, efficient production of nanofibrillated cellulose is still challenging with respect to the energy required for the disintegration process. In this study, a triticale crop residue was used as a source for the production of nanofibrillated cellulose, with lateral size of 20-30 nm, using a high pressure homogenizer and a conventional high speed blender. The effects of the delignification mode, fiber pretreatment and disintegration mode on the yield of NFC, the morphology of the ensuing nanofibrils and the energy consumption were investigated. The evolution of the reinforcing potential of the NFC according to the production mode was also studied. By controlling the lignin extraction mode and the carboxyl content of the fibers through TEMPO-mediated oxidation, it was possible to convert triticale pulps into nanofibrillar cellulose with an energy demand as low as 11 kW h kg-1 using a conventional high speed blender. This approach is expected to open the way toward easier and energetically cost-effective production of nanofibrillar cellulose from crop residues. © 2014 The Royal Society of Chemistry.

Jabbour L.,CNRS Structural Engineering | Chaussy D.,CNRS Structural Engineering | Eyraud B.,CNRS Structural Engineering | Beneventi D.,CNRS Structural Engineering
Composites Science and Technology | Year: 2012

Papermaking techniques were used to produce graphite/carbon fiber/cellulose fiber composite papers with tunable electrical conductivity and good mechanical properties.The obtained conductive papers are easy to handle, flexible and have an extremely good conductivity, up to 964Sm -1. Furthermore the proposed production process is low cost and can be easily scaled up in the perspective of disposable and recyclable device production. © 2012 Elsevier Ltd.

Faddoul R.,CNRS Structural Engineering | Reverdy-Bruas N.,CNRS Structural Engineering | Blayo A.,CNRS Structural Engineering
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2012

Environmentally friendly, water-based silver pastes, adapted for screen printing, were formulated with different silver contents (67-75%). These pastes allowed screen printing onto low temperature co-fired ceramic (LTCC) of narrow conductive tracks with a 60 μm line width and a 3 × 10 -8 Ω m electrical resistivity. Inks were formulated with a mixture of spherical and flake shape silver particles with 2-4 μm mean diameter. Rheological behaviour of pastes was studied in order to determine its effect on printed lines properties. Prepared inks were then screen printed and sintered under normal atmosphere at 875 °C. As expected, electrical properties depended on silver content. Resistivity values varying from 1.6 × 10 -8 to 3.3 × 10 -8 Ω m were calculated over 36.3 cm line length. These values are very close to bulk silver resistivity (1.6 × 10 -8 Ω m). Compared to previous research and commercial pastes, the newly formulated pastes reached equivalent or even better conductivities with lower silver content (70% by weight). © 2012 Elsevier B.V.

Paquet O.,CNRS Structural Engineering | Krouit M.,CNRS Structural Engineering | Bras J.,CNRS Structural Engineering | Thielemans W.,University of Nottingham | Belgacem M.N.,CNRS Structural Engineering
Acta Materialia | Year: 2010

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. © 2009 Acta Materialia Inc.

Lavoine N.,CNRS Structural Engineering | Desloges I.,CNRS Structural Engineering | Bras J.,CNRS Structural Engineering
Carbohydrate Polymers | Year: 2014

In this work, a new use of microfibrillated cellulose (MFC) is highlighted for high-added-value applications. For the first time, a nanoporous network formed by MFC coated on paper is used for a controlled release of molecules. The release study was carried out in water with caffeine as a model molecule. The release process was studied by means of (i) continuous, and (ii) intermittent diffusion experiments (with renewal of the medium every 10 min). The effect of the MFC was first observed for the samples impregnated in the caffeine solution. These samples, coated with MFC (coat weight of about 7 g/m2), released the caffeine over a longer period (29 washings compared with 16), even if the continuous diffusions were similar for both samples (without and with MFC coating). The slowest release of caffeine was observed for samples coated with the mixture (MFC + caffeine). Moreover, the caffeine was only fully released 9 h after the release from the other samples was completed. This study compared two techniques for the introduction of model molecules in MFC-coated papers. The latter offers a more controlled and gradual release. This new approach creates many opportunities especially in the food-packaging field. A similar study could be carried out with an active species. © 2013 Elsevier Ltd.

Missoum K.,CNRS Structural Engineering | Belgacem M.N.,CNRS Structural Engineering | Bras J.,CNRS Structural Engineering
Materials | Year: 2013

Interest in nanofibrillated cellulose (NFC) has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bionanocomposites or in paper thanks to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. It is worth noting that chemical surface modification of this material can be a key factor to achieve a better compatibility with matrices. In order to increase the compatibility in different matrices or to add new functions, surface chemical modification of NFC appears to be the prior choice to conserve its intrinsic nanofibre properties. In this review, the authors have proposed for the first time an overview of all chemical grafting strategies used to date on nanofibrillated cellulose with focus on surface modification such as physical adsorption, molecular grafting or polymer grafting. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Isaksson P.,Uppsala University | Dumont P.J.J.,CNRS Structural Engineering
Engineering Fracture Mechanics | Year: 2014

Gradient theories are capable of describing deformation of heterogeneous elastic materials better than classical elasticity theory since they are able to capture internal length effects. Here, crack-tip displacement fields at the tip of a mode I crack in gradient enhanced elastic materials are derived in closed form and contrasted with experiments. Heterogeneous materials, represented by discrete fiber networks, are analyzed in finite element models to judge the theory. It is shown that using a classical continuum approach to describe macroscopic singular-dominated deformation fields in heterogeneous materials lead to erroneous results because a structural effect that alters the displacement field becomes pronounced and results in severe blunting of crack-tips. A key conclusion is that the average segment length in the material gives the internal length scale parameter, used in the gradient enhanced continuum theory, hence allows for bridging between scales. © 2014 Elsevier Ltd.

Viguie J.,CNRS Grenoble Laboratory for Soils, Solids, Structures, and Risks | Dumont P.J.J.,CNRS Structural Engineering
Composite Structures | Year: 2013

The optimisation of board packages often rely on their load bearing capacity. Then it seems attractive to measure how such thin-walled structures deform using for instance kinematic field measurement techniques, and to incorporate, at least partially, the gained kinematic information within mechanical models. Digital Image Correlation (DIC) can provide a vivid description of the buckling of box panels, e.g. during box compression tests. Therefore, we propose an analytical plate model to predict the elastic post-buckling behaviour of corrugated board box panels where the kinematic boundary conditions emanate from DIC measurements. Comparing experimental and calculated strain fields on the outer liner of board panels as well as box compression force lend some confidence to the model. Further results reveal the heterogeneity of in-plane forces, bending and twisting moments the box panels have to withstand as well as strain fields in usually inaccessible regions of the panels such as the inner liner. Thereby an improvement of the structure of box panels can be envisaged. © 2013 Elsevier Ltd.

Lavoine N.,CNRS Structural Engineering | Desloges I.,CNRS Structural Engineering | Dufresne A.,CNRS Structural Engineering | Bras J.,CNRS Structural Engineering
Carbohydrate Polymers | Year: 2012

Interest in microfibrillated cellulose (MFC) has been increasing exponentially. During the last decade, this bio-based nanomaterial was essentially used in nanocomposites for its reinforcement property. Its nano-scale dimensions and its ability to form a strong entangled nanoporous network, however, have encouraged the emergence of new high-value applications. In previous years, its mode of production has completely changed, as many forms of optimization have been developed. New sources, new mechanical processes, and new pre- and post-treatments are currently under development to reduce the high energy consumption and produce new types of MFC materials on an industrial scale. The nanoscale characterization possibilities of different MFC materials are thus increasing intensively. Therefore, it is critical to review such MFC materials and their properties. Moreover, very recent studies have proved the significant barrier properties of MFC. Hence, it is proposed to focus on the barrier properties of MFC used in films, in nanocomposites, or in paper coating. © 2012 Elsevier Ltd. All rights reserved.

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