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Saint-Christol-lès-Alès, France

Chivas-Joly C.,French National Laboratory of Metrology and Testing | Gaie-Levrel F.,French National Laboratory of Metrology and Testing | Motzkus C.,French National Laboratory of Metrology and Testing | Ducourtieux S.,French National Laboratory of Metrology and Testing | And 5 more authors.
Journal of Hazardous Materials | Year: 2016

This work investigates the aerosols emitted during combustion of aircraft and naval structural composite materials (epoxy resin/carbon fibers and vinyl ester/glass fibers and carbon nanotubes). Combustion tests were performed at lab-scale using a modified cone calorimeter. The aerosols emitted have been characterized using various metrological devices devoted to the analysis of aerosols. The influence of the nature of polymer matrices, the incorporation of fibers and carbon nanotubes as well as glass reinforcements on the number concentration and the size distribution of airborne particles produced, was studied in the 5. nm-10. μm range. Incorporation of carbon fibers into epoxy resin significantly reduced the total particle number concentration. In addition, the interlaced orientation of carbon fibers limited the particles production compared to the composites with unidirectional one. The carbon nanotubes loading in vinyl ester resin composites influenced the total particles production during the flaming combustion with changes during kinetics emission. Predominant populations of airborne particles generated during combustion of all tested composites were characterized by a PN50 following by PN100-500. © 2015 Elsevier B.V. Source

Djellali S.,Ferhat Abbas University Setif | Djellali S.,University of Bordj Bou Arreridj | Sadoun T.,University of Abderrahmane Mira de Bejaia | Haddaoui N.,Ferhat Abbas University Setif | Bergeret A.,Center des Materiaux des Mines dAles
Polymer Bulletin | Year: 2015

The rheological properties and the viscoelastic behaviour of blends of polyethylene with different percentages of poly(lactic acid), ranging from 0 to 100 wt%, were studied. In a first part, all blends were examined under steady conditions using a capillary rheometer (at 180, 190 and 200 °C) and dynamic conditions using a parallel plate rheometer. The results showed that all blends behaved like pseudoplastic fluids, with the power–law index values varying between those of polyethylene and polylactide (0.45–0.75 at 180 °C, 0.49–0.77 at 190 °C and 0.54–0.81 at 200 °C). It was also observed that at low shear rate, pure poly(lactic acid) and polyethylene possessed, respectively, the highest and the lowest flow activation energy (66.9 and 48.3 kJ/mol); however, at high shear rate, the greater the content of poly(lactic acid), the lower the activation energy. In addition, poly(lactic acid) exhibited lower viscosity and lower melt elasticity than either polyethylene or the blends. The dynamic rheological study demonstrated that all formulations displayed shear thinning behaviour and only virgin poly(lactic acid) exhibited a clear Newtonian plateau. Also, mainly at low frequencies, polyethylene had the higher values of storage modulus (325 Pa), loss modulus (937 Pa) and complex viscosity (9,740 Pa.s). However, blends had values lying between those of the two homopolymers without any improvement in the storage modulus, loss modulus or complex viscosity. In a second part, the viscoelastic characteristics were investigated using dynamic mechanical thermal analysis (DMTA). DMTA spectra showed an increase in the storage modulus with the increase of poly(lactic acid) content but the opposite was observed for the loss modulus. A cold crystallization of poly(lactic acid) is observed around 87–100 °C and the temperature of glass transition of poly(lactic acid) did not depend on the composition of the blend. These results indicate that LDPE and PLA are immiscible in all proportions either in the melt state or in the solid state. © 2015, Springer-Verlag Berlin Heidelberg. Source

Apolinario G.,Center des Materiaux des Mines dAles | Ienny P.,Center des Materiaux des Mines dAles | Corn S.,Center des Materiaux des Mines dAles | Leger R.,Center des Materiaux des Mines dAles | And 2 more authors.
RILEM Bookseries | Year: 2016

Mechanical properties of flax-fibre reinforced composites (FFRC) are strongly affected by water ageing compared to glass-fibre reinforced composites (GFRC). This study highlights the influence of water absorption during immersion at 30°C on mechanical properties of unsaturated polyester reinforced composites. Flax-fibre composites showed a Fickian absorption behaviour and a water uptake 15 times higher than that of glass-fibre composites. GFRC’s tensile modulus and maximum stress were slightly affected by water uptake while FFRC’s tensile modulus decreased by 37%, and ultimate stress increased by 34%. A silane-based chemical treatment (1% compared to flax fibres) was applied onto flax fibres. Water uptake was slightly reduced by 9% while tensile modulus at saturation was enhanced by 22% on treated FFRC compared to untreated ones. Moreover, the complete recovery of the tensile modulus after desiccation suggests that ageing was mainly reversible: fibre and matrix plasticizing phenomena occurred during immersion at 30°C. No damage was noticed but composites’ initial properties changed with the action of water: further crosslinking of matrix and release of fibre’s small cell-walls components into water were observed. Finally, the drying conditions influenced the return to the initial state before ageing insofar the flax fibres partially lost their initial humidity. © RILEM 2016. Source

Galhoum A.A.,Center des Materiaux des Mines dAles | Atia A.A.,Menoufia University | Mahfouz M.G.,Nuclear Materials Authority | Abdel-Rehem S.T.,Ain Shams University | And 3 more authors.
Journal of Materials Science | Year: 2015

Magnetic-chitosan nano-based particles were successfully prepared by a simple one-pot co-precipitation method before being functionalized with three different amino acid groups (i.e., alanine, serine, and cysteine) using epichlorohydrin as the linking agent. The structural and functional characteristics of the nanosorbents were investigated by elemental analysis, Fourier transform infrared spectrometer, X-ray diffraction, TEM, and vibrating sample magnetometry. The sorption properties of these materials were tested for Dy(III) recovery from aqueous solution: pH effect, uptake kinetics, and sorption isotherms were investigated. Sorbent particles are super-paramagnetic and their size is in the range of 15–40 nm. Kinetic profiles are successfully modeled with the pseudo second-order rate equation. The Langmuir and the Dubinin–Radushkevich equations fit well-sorption isotherms. The maximum sorption capacities at pH 5 (optimum pH, and at T: 27 ± 1 °C) are close to 14.8, 8.9, and 17.6 mg Dy g−1 for alanine, serine, and cysteine type, respectively. Cationic species RE(III) in aqueous solution appear to be sorbed by combined chelation and anion-exchange mechanisms. The sorption process begins at low-metal concentration by a physical monolayer sorption at low ion concentration before metal ions can be sorbed at higher metal concentration by coordination. The values of the thermodynamic parameters ΔG° and ΔH° indicate the spontaneous and endothermic nature of the mechanism, while the positive values of ΔS° show that during the sorption process the randomness increases. Finally, the sorbent can be efficiently regenerated using acidified thiourea: the amount of Dy(III) sorbed is hardly reduced, at least during the first four sorption/desorption cycles. © 2015, Springer Science+Business Media New York. Source

Tran T.P.T.,Center des Materiaux des Mines dAles | Tran T.P.T.,Hanoi University of Science and Technology | Benezet J.-C.,Center des Materiaux des Mines dAles | Bergeret A.,Center des Materiaux des Mines dAles
Industrial Crops and Products | Year: 2014

This paper investigated specific surface treatments, aimed to improve the adhesion between PLA and rice and Einkorn wheat husks. In the first part, husks were treated by alkaline solutions at three concentrations (2, 5 and 10%) at room temperature for different times between 6 and 48. h. Results revealed that the alkaline treatment dissolved a fraction of waxes, lignin and hemicellulose, so that the polarity of their surface was increased and therefore alkaline treated husks were more sensitive to moisture. Moreover the alkaline treatments have more influence on wheat than on rice husks, as shown by chemical composition determination, FTIR measurements and ESEM observations. In the second part, husks were treated by two kinds of organosilanes (γ-aminopropyltriethoxysilane (APS) and γ-glycidoxypropyltrimethoxysilane GPS)). These silane treatments were applied either alone or on previously alkaline treated husks (NaOH 5% for 24. h). The results showed that silane treatments reduced the moisture sensitivity and raise the energy surface of the husks. In the last part, treated husks were incorporated into polylactic acid (PLA) to produce biocomposites. Biocomposites reinforced by husks treated by alkaline solution and silane have higher bending moduli and stresses than those reinforced by untreated husks and husks treated by silane alone. It can be supposed that the PLA/husks adhesion was enhanced. No difference was observed according to the silane nature. © 2014 Elsevier B.V. Source

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