CNRS Research Center for Thermal Systems and Energy

Creteil, France

CNRS Research Center for Thermal Systems and Energy

Creteil, France
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Chelghoum N.,Ferhat Abbas University Setif | Guessoum M.,Ferhat Abbas University Setif | Fois M.,CNRS Research Center for Thermal Systems and Energy | Haddaoui N.,Ferhat Abbas University Setif
Journal of Polymers and the Environment | Year: 2017

Samarium acetylacetonate (Sm-Acac) was added to catalyze interchange reactions between poly(lactic acid) (PLA) and polycarbonate (PC) in order to promote compatibilization and enhance the performances of the PLA/PC blend. The effects of the composition and catalyzed transesterification reactions were investigated using differential scanning calorimetry (DSC), thermogravimetry (TG), dynamic mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM). DMTA and DSC analysis revealed the immiscibility of the uncatalyzed PLA/PC blends for the studied compositions because the glass transition temperatures of PC and PLA were unchanged after blending. In the PLA glassy region, PLA/PC blends exhibited lower storage moduli which increased upon heating due to the cold crystallization process. During melt mixing with Sm-Acac catalyst, PLA/PC blends were submitted to two competing processes. In one hand, Sm-Acac acted as a plasticizer and contributed in decreasing significantly the glass transition, crystallization and melting temperatures of PLA phase. In the other hand, Sm-Acac proved its efficiency in catalyzing the transesterification reactions that were evidenced by the decrease of the PLA aptitude to crystallization due to the hindering effect of the PC units inserted into the PLA chains. PLA/PC blends melt mixed with 0.25% of Sm-Acac showed a significant strengthening effect, corresponding to an increase in the storage modulus in the temperature range comprised between 70 and 90 °C. This indicated the formation of a copolymer at the interface and the promotion of adhesion as it is confirmed from the decrease in the height of the PLA Tan δ peak. At 0.5% of Sm-Acac, (90/10) PLA/PC blend revealed a new peak assigned to the glass transition of the PLA-PC copolymer, whereas the (50/50) PLA/PC blend was converted into a new random copolymer. TG analysis proved the presence of a copolymer structure presenting an intermediate thermal stability in both the catalyzed and uncatalyzed blends. © 2017 Springer Science+Business Media New York

Bouzidi F.,Ferhat Abbas University Setif | Guessoum M.,Ferhat Abbas University Setif | Fois M.,CNRS Research Center for Thermal Systems and Energy | Haddaoui N.,CNRS Research Center for Thermal Systems and Energy
Journal of Adhesion Science and Technology | Year: 2017

Poly(lactic acid) (PLA)/polypropylene (PP) blends composites were prepared by incorporating 3 wt.% of copper modified montmorillonite (MMT-Cu2+), obtained using cation exchange in a CuSO4 solution, and 10 wt.% of polypropylene-graft-maleic anhydride (PP-g-MA) as a compatibilizer then varying the PLA content until 50 wt.%. These materials were subjected to several investigations such as X-rays diffraction, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile and environmental tests. The DMTA analysis showed that the glassy PLA high stiffness and the PP crystalline phase compensate the decrease in the storage modulus occurring during the PP and PLA glass transitions, respectively. The variations of tan δ revealed no changes on the PP and PLA phases glass transitions temperatures which indicate the immiscibility of the two polymers, as supported by DSC analysis. Blends composites SEM micrographs stated the immiscibility of the system resulting in the poor adhesion of the PLA droplets to the PP matrix. Also, the blends composites exhibited intermediate tensile properties between those of PP and PLA. The incorporation of MMT-Cu2+ to the (50/50) PP/PLA blend accentuated its aptitude to water absorption and ensured an efficient antimicrobial activity over a satisfactorily long period of around six months. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Ramdani N.,French Institute for Research in Computer Science and Automation | Ramdani N.,CNRS Montpellier Laboratory of Informatics, Robotics and Microelectronics | Meslem N.,French National Institute for Agricultural Research | Candau Y.,CNRS Research Center for Thermal Systems and Energy
Nonlinear Analysis: Hybrid Systems | Year: 2010

We address nonlinear reachability computation for uncertain monotone systems, those for which flows preserve a suitable partial orderings on initial conditions. In a previous work Ramdani (2008) [22], we introduced a nonlinear hybridization approach to nonlinear continuous reachability computation. By analysing the signs of off-diagonal elements of system's Jacobian matrix, a hybrid automaton can be obtained, which yields component-wise bounds for the reachable sets. One shortcoming of the method is induced by the need to use whole sets for addressing mode switching. In this paper, we improve this method and show that for the broad class of monotone dynamical systems, component-wise bounds can be obtained for the reachable set in a separate manner. As a consequence, mode switching no longer needs to use whole solution sets. We give examples which show the potentials of the new approach. © 2009 Elsevier Ltd. All rights reserved.

John M.J.,South African Council for Scientific and Industrial Research | John M.J.,Nelson Mandela Metropolitan University | Tlili R.,CNRS Research Center for Thermal Systems and Energy | Anandjiwala R.D.,South African Council for Scientific and Industrial Research | And 3 more authors.
Composites Part B: Engineering | Year: 2012

The study on heat transport in composites is of fundamental importance in engineering design and for tailoring thermal and mechanical behaviour of materials. In this study, the thermal conductivity and thermal diffusivity of flax reinforced polypropylene (PP) composites were determined at room temperature. Chemical modification in the form of a biodegradable zein coating was applied to the flax nonwovens. The effect of fibre loading and chemical modification on the thermo-physical properties was investigated. Dielectric permittivity studies were also evaluated and the dielectric constant of fibre reinforced composites was found to be higher than that of PP. The heat flow and crystallinity effects of the composites were also determined by differential scanning calorimetric (DSC) studies. Zein modification of the flax fibres resulted in a decrease of thermal conductivity and diffusivity which was attributed to a decrease in velocity and mean free path of phonons due to increase in interfacial adhesion. © 2011 Elsevier Ltd. All rights reserved.

PubMed | CNRS Research Center for Thermal Systems and Energy, Eau de Paris and University Paris Est Creteil
Type: Journal Article | Journal: Environmental science and pollution research international | Year: 2016

Climate change and increasing demography press local authorities to look after affordable water resources and replacement of drinking water for city necessities like street and pavement cleaning by more available raw water. Though, the substitution of drinking by non-drinking resources demands the evaluation of sanitary hazards. This article aims therefore to evaluate the contribution of cleaning water to the overall exposure of city dwellers in case of wet pavement cleaning using crossed physical, chemical and biological approaches. The result of tracer experiments with fluorescein show that liquid water content of the cleaning aerosol produced is about 0.24 g m(-3), rending possible a fast estimation of exposure levels. In situ analysis of the aerosol particles indicates a significant increase in particle number concentration and particle diameter, though without change in particle composition. The conventional bacterial analysis using total coliforms as tracer suggests that an important part of the contamination is issued from the pavement. The qPCR results show a more than 20-fold increase of background genome concentration for Escherichia coli and 10-fold increase for Enterococcus but a negligible contribution of the cleaning water. The fluorescence analysis of the cleaning aerosol confirms the above findings identifying pavement surface as the major contributor to aerosol organic load. The physical, chemical and microbiological approaches used make it possible to describe accurately the cleaning bioaerosol and to identify the existence of significantly higher levels of all parameters studied during the wet pavement cleaning. Though, the low level of contamination and the very short time of passage of pedestrian in the zone do not suggest a significant risk for the city dwellers. As the cleaning workers remain much longer in the impacted area, more attention should be paid to their chronic exposure.

Medjdoub N.,Ferhat Abbas University Setif | Guessoum M.,Ferhat Abbas University Setif | Fois M.,CNRS Research Center for Thermal Systems and Energy
Journal of Adhesion Science and Technology | Year: 2016

Poly(lactic acid) (PLA)/(linear low-density polyethylene (LLDPE)–low-density polyethylene (LDPE)) PLA/(LLDPE-LDPE) ternary blends were prepared and characterized as function of the PLA content. (50/50) PLA/(LLDPE–LDPE) blend was also compatibilized using maleic anhydride grafted low-density polyethylene (PE-g-MA) incorporated with a concentration of 5 wt.%. PLA/(LLDPE–LDPE) blend composites have been prepared by dispersing 5 wt.% of an organophilic montmorillonite (Org-MMT), added according to two different mixing methods. These materials were subjected to several investigations such as X-rays diffraction (XRD), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry, and environmental tests. In the PLA glassy region, DMTA results showed that the storage modulus of PLA/(LLDPE–LDPE) blends decreases upon decreasing the PLA content. When PE-g-MA and Org-MMT were added, PLA exhibited a noticeable increase in the storage modulus across the glass transition region due the interface reinforcement and the enhancement of the blends stiffness. The decrease in the magnitude of the PLA tan δ peak was attributed to the decrease in the molecular mobility that could result from the increase in the interfacial resistance. XRD analysis showed that the method of dispersion of the nanoclay controls the final structural properties of the composites. (50/50) PLA/(LLDPE-LDPE) blend and composites revealed a satisfactory aptitude to biodegradation. © 2016 Informa UK Limited, trading as Taylor & Francis Group

Sari-Bey S.,CNRS Research Center for Thermal Systems and Energy | Fois M.,CNRS Research Center for Thermal Systems and Energy | Krupa I.,Slovak Academy of Sciences | Krupa I.,Qatar University | And 3 more authors.
Energy Conversion and Management | Year: 2014

This work focuses on the study of heat transfer mechanisms in composites materials which may be used for Latent Heat Thermal Energy Storage applications. These composites contain phase change material (PCM) which can absorb and release energy during thermal cycling. PCM's used here are paraffins microencapsulated in poly(methylmethacrylate); microencapsulation avoids the flow of paraffin when it is in the liquid state. Samples with different paraffin weight fractions and particles shape and distribution were studied in this work. Scanning Electron Microscopy and Differential Scanning Calorimetry were used to determine morphology and perform measurements of phase changes temperatures, enthalpies and heat capacity respectively. Further, a periodic method (DICO) allowed measuring thermal conductivity (λ) and diffusivity (a) of the composites at temperatures below and above of the paraffin phase change from crystalline solid to isotropic liquid. © 2013 Elsevier Ltd. All rights reserved.

Dujardin N.,CNRS Research Center for Thermal Systems and Energy
Journal of Physical Chemistry B | Year: 2011

It has been recently shown that mechanical milling can amorphize d-glucose without any mutarotation, giving rise to an anomerically pure amorphous sample. We have taken advantage of this exceptional possibility to study the kinetic of mutarotation in the amorphous solid state. The investigations have been performed in situ by time-resolved Raman spectroscopy. The results reveal an unexpected coupling between the mutarotation process and the structural relaxations involved in the glassy state. © 2011 American Chemical Society.

Gaubert B.,Institute Pierre Simon Laplace | Coman A.,Institute Pierre Simon Laplace | Foret G.,Institute Pierre Simon Laplace | Meleux F.,INERIS | And 5 more authors.
Geoscientific Model Development | Year: 2014

An ensemble Kalman filter (EnKF) has been coupled to the CHIMERE chemical transport model in order to assimilate ozone ground-based measurements on a regional scale. The number of ensembles is reduced to 20, which allows for future operational use of the system for air quality analysis and forecast. Observation sites of the European ozone monitoring network have been classified using criteria on ozone temporal variability, based on previous work by Flemming et al. (2005). This leads to the choice of specific subsets of suburban, rural and remote sites for data assimilation and for evaluation of the reference run and the assimilation system. For a 10-day experiment during an ozone pollution event over Western Europe, data assimilation allows for a significant improvement in ozone fields: the RMSE is reduced by about a third with respect to the reference run, and the hourly correlation coefficient is increased from 0.75 to 0.87. Several sensitivity tests focus on an a posteriori diagnostic estimation of errors associated with the background estimate and with the spatial representativeness of observations. A strong diurnal cycle of both these errors with an amplitude up to a factor of 2 is made evident. Therefore, the hourly ozone background error and the observation error variances are corrected online in separate assimilation experiments. These adjusted background and observational error variances provide a better uncertainty estimate, as verified by using statistics based on the reduced centered random variable. Over the studied 10-day period the overall EnKF performance over evaluation stations is found relatively unaffected by different formulations of observation and simulation errors, probably due to the large density of observation sites. From these sensitivity tests, an optimal configuration was chosen for an assimilation experiment extended over a three-month summer period. It shows a similarly good performance as the 10-day experiment. © Author(s) 2014.

Tlili R.,CNRS Research Center for Thermal Systems and Energy | Boudenne A.,CNRS Research Center for Thermal Systems and Energy | Cecen V.,Dokuz Eylül University | Ibos L.,CNRS Research Center for Thermal Systems and Energy | And 2 more authors.
International Journal of Thermophysics | Year: 2010

Over the last few years, conducting polymer/graphite nanocomposites have attracted considerable interest because of their exceptional electrical, thermal, and mechanical properties. Polymeric nanocomposites prepared from high aspect ratio layered graphite nanofillers achieve significant improvements in thermophysical and electrical properties at low filler concentrations, compared to conventional composites, without a significant increase in density. In this work, various aspects of the electrical and thermophysical behavior of nanocomposites are presented based on the ethylene-vinylacetate matrix filled with nanostructured expanded graphite and standard, (nano)/micro-sized graphite. © Springer Science+Business Media, LLC 2010.

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