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ETUDE DE POLYMERE BIOSOURCE A BASSE DE POLY (ACIDE LACTIQUE) (PLA) PLASTIFIE AVEC DES PLASTIFIANTS VEGETAUX (ESTERS CITRIQUE)

M. Maiza, A. HAMAM, M. MESSAOUDI, M. T. Benaniba  (2017)
Article de conférence

Ces dernières années, le polyacide lactique (PLA) a attiré beaucoup d'attention comme un remplacement des plastiques issus du pétrole. Le PLA est fabriqué à partir de la fermentation du sucre ou de l'amidon. Il est de ressources renouvelables, biodégradables, alimentaires et non toxiques. Le PLA est utilisé dans les emballages alimentaires, la vaisselle jetable, mais aussi dans un certain nombre d'applications biomédicales, telles que les sutures, les stents et certains injecteurs de drogues [1,2]. Le polyacide lactique (PLA) est un polyester aliphatique présente une haute résistance, un haut module, cependant sa fragilité limite ses domaines d’application. Des efforts considérables ont été conduits pour modifier les propriétés de PLA [3,4]. L’objectif de ce travail est la plastification du PLA par l’utilisation des bio-plastifiants à base des esters citrique pour augmenter sa flexibilité. Lors de la préparation des différentes formulations nous utilisons le traitement thermique dans le plastographe Brabender. La plastification du PLA par Triéthyle citrique (TEC), Tributyle 2- acétyle citrique (TBAC), est réalisée par malaxage dans le plastographe Brabender à quatre compositions: 5, 10, 15, 20 et 30%. La spectroscopie infrarouge à transformée de Fourier (IRTF) indiquent qu'il y a des interactions moléculaires par liaison hydrogène intermoléculaire entre le PLA et les esters citriques (TEC et TBAC). Les résultats de diffraction des rayons X (DRX) confirment que le PLA n’avait pas de polymorphe de transition cristalline, les spectres UV-visible indiquent que les deux plastifiants (TEC et TBAC) n’ont pas d’effet sur la transparence et la coloration des films. Voir les détails

Mots clés : Polyacide lactique (PLA), Plastification, Triéthyle citrique (TEC), Tributyle 2- acétyle citrique (TBAC), biodégradable.

Computational study of droplet breakup in a trapped channel configurationusing volume of fluid method

T. CHEKIFI  (2018)
Publication

Computational Fluid Dynamics is performed to numerically investigate the droplet breakup of water in oil intrapped channel configuration. The volume-of-fluid (VOF) method based the commercial code FLUENT isadopted to track the interface. Two designs are suggested to study the effect of flow conditions parameters andouter channel size on the droplet breakup mode, droplet generation frequency and size. As a function of thevelocity ratio, droplets are formed in two modes, dripping mode: droplets were generated closed to the nozzle, itwas identified at low capillary number (Ca<0.005) and jetting mode: droplets were produced after a long jet,where the capillary number Ca varies from 0.01 to 0.025. The numerical results indicated the collection channeldiameter plays potential role in the determination of droplet size and droplet generation frequency, the shearforces excreted by the continuous phase on the dispersed thread are reduced in the wider model leading to havedroplets much bigger than the narrow model, the latter produced small droplets due the high shear stressgenerated in the confinement region. Furthermore, the droplet frequency and size are found to be stronglydependent on the capillary velocity ratio. However, increasing the flow velocity ratio in both models leadsdroplets to be generated in high frequency, while the droplet length was decreasing. This work also demonstratesthat the VOF method is an effective way to simulate the droplets breakup in trapped channel geometry. Voir les détails

Mots clés : T. Chekifi

Computational Investigation of Droplets Behaviour inside Passive Microfluidic Oscillator

T. CHEKIFI, B. dennai, R. Khelfaoui  (2017)
Publication

Recently, modeling immiscible fluids such as oil and water have been a classical research topic. Droplet-based microfluidics presents a unique platform for mixing, reaction, separation, dispersion of drops and many other functions. In this paper, we suggest a numerical CFD study of microfluidic oscillator with two different lengths of feedback loop. In order to produce simultaneous droplets of gasoil on water, a typical geometry that includes double T-junction is connected to the fluidic oscillator. Droplets production is computed by volume-of-fluid method (VOF). Flow oscillations of droplets were triggered by the Coanda effect of jet flow. The aim of work is to get a high oscillation frequency in the output of this passive device, the influence of hydrodynamics and physics parameters on the droplets frequency in the output of our microsystem is also investigated, the computational results show that, the length of feedback loop, operating pressure and interfacial tension have a significant effect on the droplets dynamic inside microfluidic oscillator. Across the range of low Reynold number, the droplets generation and its dynamics have been accurately controlled by adjusting applying pressure ratio of two phases. Voir les détails

Mots clés : Droplet, microfluidics, fluidic oscillator, CFD and VOF (volume of fluid method).

Formulation et caractérisation des matériaux biodégradables à base de l’acide polylactique-Plastifiants

MAIZA Mounira (2016)
Thèse de doctorat

In this study, the characterization of plasticized PLA with TEC and ATBC by melt blending method wasreported. The value of the melt flow index (MFI) observed for all samples are higher than those of neat PLA.The evaluation of the influence of the type and plasticizer content on the viscoelastic properties of PLA withDMA indicates a decrease in the storage modulus for plasticized PLA, indicating the flexibility and mobility ofthe amorphous phase of PLA caused by TEC and ATBC. UV-Visible spectroscopy shows that the twoplasticizers: TEC and ATBC have no effect on the color change of the films. The opacity values of the PLAfilms plasticized with TEC and ATBC were slightly lower than the value of the treated PLA film. X-raydiffraction shows the appearance of a strong diffraction at 16.7° assigned to the crystalline phase α, whichconfirms that the PLA has no crystalline polymorph transition. FTIR spectra indicate that there are somemolecular interactions by intermolecular hydrogen bonds between PLA and citrate ester. The thermal propertiesof plasticized PLA shows that TEC and ATBC are effective in lowering the glass transition temperature (Tg), themelting temperature (Tm) and the cold crystallization temperature (Tcc) of the PLA. In addition, its crystallinityincreases with increasing content of plasticizer. The TGA results indicated that the TEC and ATBC promote adecrease in thermal stability of the PLA. The weight loss plasticizer with heating time and at 100 °C is lesserthan at 135 °C. Leaching of TEC and ATBC results in cracks and changed color of material. The tensile testshowed that the formulations of the plasticized PLA with citrate ester (TEC and ATBC) give better mechanicalproperties by providing treated PLA. The observation by SEM confirmed there is miscibility between the PLAand plasticizer. Finally it can be said that the higher molecular weight of citrate exhibited a greater plasticizingeffect. Voir les détails

Mots clés : Polylactic acid (PLA), plasticizing, Triethyl Citrate (TEC), Acetyl Tributyl Citrate (ATBC)

MICROGOUTTES : ETUDE DE LA PRODUCTION ET LA MANIPULATION DESMICROGOUTTES DANS LES ECOULEMENTS FLUIDIQUES, DANSLES MICROCANAUX, AUX PROFITS DU GENIE DES PROCEDES

Chekifi Tawfiq (2016)
Thèse de doctorat

Ces travaux de recherche s’inscrivent d’une part dans une thématique demicrofluidique digitale : La microfluidique se propose d’imaginer de nouvelles techniquesadaptées aux microsystèmes et permettent d’attribuer aux microsystèmes des propriétésd’écoulements performantes malgré le caractère fortement laminaire de ces écoulements.Un aperçu général sur la microfluidique de microgoutte est présenté, incluant unaperçu bref des techniques de fabrication et des techniques de conception des microsystèmes.Une partie de notre travail porte sur les travaux antérieurs des écoulements dans les microscanaux. Nous exposons ensuite les détails des simulations numériques (en utilisant le codecommercial, Fluent) concernant l’analyse des micro-écoulements liquides.La génération de microgouttes s’effectue habituellement par agitation mécaniquevigoureuse. Les systèmes microfluidiques offrent une alternative aux systèmes classiques.Pour cela, il existe différentes techniques d’émulsifications microfluidiques.Les microstructures véhiculent localement des quantités beaucoup moins importantes deréactif que les procédés classiques, ils permettent aussi de travailler dans des conditions desécurité quasi maximales mais aussi d’augmenter la sélectivité chimique des réactions.La première technique développée pour générer des gouttes de façon contrôlée enmicrosystème est la jonction-T, Les microgouttes générées nécessitent des techniques demanipulation pour gérer et contrôler ces microgouttes. Dans cette étude, nous avons proposédes géométries à l’objectif de produire et manipuler par voie hydrodynamique lesmicrogouttes. Des résultats importants ont été obtenus dans les deux approches (numérique àl’aide de code commercial Fluent et expérimental à travers les moyens disponibles). Voir les détails

Mots clés : Microfluidique, microcanaux, microgoutte, écoulement dispersé, production des microgouttes, manipulation des microgouttes, simulation CFD (méthode de VOF)

Synthèse et caractérisations de nouvelles générations de céramiques piézoélectriques sans plomb

SEDDA kamal (En préparation)
Thèse de doctorat

Dans ce travail de thèse, nous proposons d’élaborer de nouvelles céramiques piézoélectriques sans plomb, d’étudier l’influence des procédés d’élaboration et des conditions de synthèse de ces céramiques sur les propriétés physiques, microstructurales, diélectriques, piézoélectriques et ferroélectriques. Diverses techniques disponibles nous permettront de mener à bien ces travaux de recherche, que ce soient des techniques d’élaboration (synthèse en voie solide, sol-gel, …) ou des techniques de caractérisation (DRX, MEB, MET, STEM-EDX, ATD-TG, caractérisations diélectriques, piézoélectriques et ferroélectriques).En plus de cette étude fondamentale de nouvelles céramiques sans plomb, une application pourrait être développée : la conception de transformateurs piézoélectriques. Cette partie de l’étude passe d'abord par le choix d’une structure, le dimensionnement géométrique, suivis de la fabrication des prototypes (plusieurs architectures seront proposées) pour finir enfin par la détermination de leurs performances (gain, rendement, puissance). Voir les détails

Mots clés : synthèse, Céramique piézoélectriques, Système BCTZ, Caractérisation, microstructure

Characterization of toughened Poly (lactic acid) PLA/ Polycaprolactone (PCL) with bio-plasticizers (TEC and PEG3)

M. Maiza, A. HAMAM  (2019)
Article de conférence

Triethyl citrate (TEC) and poly (ethylene glycol) (PEG3) were used as plasticizer for Polylactic acid (PLA)/ polycaprolactone (80PLA/20PCL) blends. The treated and plasticized 80PLA/20PCL blends at various concentrations of plasticizers were analyzed were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), Differential scanning calorimetry was used to evaluate the crystallinity and thermal property of all the samples. It was found that the glass transition temperature (Tg) and the melting temperature (Tm) decreased as the amount of plasticizers increased. Additionally, the presence of TEC or PEG3 tended to increase the crystallinity of PLA. DMA of plasticized PLA indicates that a decrease in Tg is obtained with increasing plasticizer content, Plasticizing effect was also shown by decrease in the dynamic storage modulus and viscosity of plasticized mixtures compared to the treated 80PLA/20PCL blends. The TGA results indicated that PEG3 and TEC promoted a decrease in thermal stability of the 80PLA/20PCL. Voir les détails

Mots clés : Poly lactic acid (PLA), Polycaprolactone (PCL), Plasticizers vegetable, Biodegradable

Enhancement of photoelectrochemical and optical characteristics using a TiO2 nanoparticles interlayer in MEH-PPV heterojunction devices

F Habelhames, M Girtan, A Manole, L LAMIRI, W Zerguine, B Nessark  (2012)
Publication

In this work, MEH-PPV+TiO 2 composite material was prepared by incorporation of titanium oxide nonoparticles (TiO 2) into poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) polymer matrix and deposited by spin coating on glass and indium thin oxide (ITO) substrates. The absorbance of various MEH-PPV composites incorporating different concentrations of TiO 2 nanoparticles shows that addition of TiO 2 improves absorption of the composites. TiO 2 and the conjugated polymer have absorption in the UV and visible regions, respectively. As a result, the composite has slightly broader absorption. In addition, absorption of the composite shows that the polymer induces a certain structuring, as evidenced by the presence of fine structures. The effect of inserting a TiO 2 nanoparticles interlayer in the MEH-PPV polymer heterojunction device on the photoelectrochemical and optical characteristics of the device has been studied. The modified device (MEH-PPV+TiO 2) shows improved photocurrent density characteristics, and increased with TiO 2 concentration. The study showed that the presence of inorganic semiconductor nonoparticles (TiO 2) in polymer film improves the optical and the photovoltaic properties of MEH-PPV, and was designed to explore new approaches to improve light-collection efficiency in polymer photovoltaic. Voir les détails

Mots clés : Hybrid composite materials, MEH-PPV, morphology, photocurrent

Growth and characterization of electrodeposited Cu2O thin films

S. Laidoudi, A.Y. Bioud, A. Azizi, G. Schmerber, J. Bartringer, S. Barre, A. Dinia  (2013)
Publication

This work demonstrates the electrodeposition of cuprous oxide (Cu2O) thin films onto a fluorine-doped tin oxide (FTO)-coated conducting glass substrates from Cu(II) sulfate solution with C6H8O7 chelating agent. During cyclic voltammetry experiences, the potential interval where the electrodeposition of Cu2O is carried out was established. The thin films were obtained potentiostatically and were characterized through different techniques. From the Mott–Schottky measurements, the flat-band potential and the acceptor density for the Cu2O thin films are determined. All the films showed a p-type semiconductor character with a carrier density varying between 2.41 × 1018 cm−3 and 5.38 × 1018 cm−3. This little difference is attributed to the increase of the stoichiometric defects in the films with the deposition potential. Atomic force microscopy analysis showed that the Cu2O thin films obtained at high potential are more homogenous in appearance and present lower crystallites size. X-ray Voir les détails

Mots clés : Cu2O, electrodeposition, Mott–Schottky, optical properties, Thin films, XRD

Electrochemical and spectroscopic characterization of poly (bithiophene + 2-methylfuran) copolymer.

Leila LAMIRI, Belkacem Nessark, Farid Habelhames, Lakhdar Sibous  (2017)
Publication

In this work, Poly(bithiophene + 2-methylfuran) copolymer is successfully achieved by an electrochemical polymerization of two monomers, bithiophene and 2-methylfuran in acetonitrile containing lithium perchlorate. The resultant copolymer was characterized via cyclic voltammetry, impedance spectroscopy, UV-visible, scanning electron microscope, conductivity and photocurrent measurements. The cyclic voltammetry study showed two redox couples characteristic of Poly (bithiophene + 2-methylfuran) copolymer. The impedance spectroscopy study revealed that the resistance of the copolymer ?lm increases with the addition of 2-methylfuran. The photocurrent measurement showed good photoelectrochemical properties, making this copolymer an ideal candidate for photovoltaic cell applications. Voir les détails

Mots clés : Electrochemical polymerization, copolymer, polybithiophene, poly2-methylfuran, morphology, photo-electrochemical properties.