Structure of zwitterionic surfactant micelles: micellar size and intermicellar interactions

International audienc

Effect of a Nitroxyle-Based Radical Scavenger on Nanotube Functionalisation with Pentadecane: A Model Compound Study for Polyethylene Grafting onto MWCNTs

International audienceThe radical grafting of pentadecane onto MWCNTs has been investigated. A model for the functionalisation of MWCNTs with molten polyethylene is established, in which a pentadecane radical grafting reaction has been studied in order to determine the reaction conditions necessary to enhance the degree of grafting while minimising side reactions such as radical combination reactions. The effect of a nitroxyle-based radical scavenger (such as TEMPO) on the competition between the recombination of pentadecane radicals and addition to nanotubes has been explored. It was observed that the use of TEMPO resulted in a relatively higher grafting density without excessive pentadecane branching/cross-linking

Blending PP with PA6 industrial wastes: Effect of the composition and the compatibilization

International audienceBlending polypropylene to recycled PA6 industrial wastes at different compositions, with and without compatibilizer PPgMA was produced in a corotating twin screw extruder where, polypropylene acts as the polymer matrix and polyamide as the dispersed phase. Several techniques were used to investigate the morphology, thermal, viscoelastic and tensile properties of these blend. Binary PP/PA6 blends showed the presence of PA6 particles dispersed in the PP continuous phase and exhibited a coarse morphology. Increasing PA6 contents in the blend increased their crystallinity and their size and improved the tensile properties at weak deformation. In addition to compatibilizer PPgMA, the morphology shows lower diameters and a decrease in size of the dispersed PA6 particles. The interfacial adhesion was also improved, as a result of the creation of an interphase that was formed by the interaction between the formed PPgPA6 copolymer in situ and both phases. This interphase induced an improvement in tensile properties. The PPgPA6 copolymer generated by the interphase was identified with DMA analysis thanks to an additional transition in loss modulus curves

In-line near infrared monitoring of esterification of a molten ethylene-vinyl alcohol copolymer in a twin screw extruder

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Effect of radical grafting of tetramethylpentadecane and polypropylene on carbon nanotubes' dispersibility in various solvents and polypropylene matrix

Multiwalled carbon nanotubes (MWCNTs) have been functionalized by tetramethylpentadecane (TMP), 1-dodecanethiol (DT) and polypropylene (PP) through radical addition onto MWCNTs' surface using dicumyl peroxide as hydrogen abstractor. Surface functionalized MWCNTs were characterized by Raman, IR spectroscopy, elementary analysis (EA) and thermogravimetric analysis (TGA). We studied the effect of temperature, peroxide concentration and solvent on TMP grafting densities and it was found that this surface treatment lead to a fair solubility in various solvents. TMP-functionalized MWCNTs were also imaged by transmission electronic microscopy showing single long functionalized MWCNTs distinct from the starting pristine bundles. For the first time, PP was then grafted onto MWCNTs through a radical grafting reaction. However, scanning electronic microscopy images of PP-functionalized MWCNTs/PP composites did not show a significant improvement in MWCNTs dispersion within the PP matrix. (C) 2009 Elsevier Ltd. All rights reserved

Efficient Carbonyl Hydrosilylation Reaction: Toward EVA Copolymer Crosslinking

International audienceIn this article, the hydrosilylation reaction of carbonyl groups of acetate derivatives and SiH groups of hydride-terminated polydimethylsiloxane at high temperature (100-130 degrees C) are described. Triruthenium dodecacarbonyl, Ru(3)(CO)(12), was used as effective catalyst for hydrosilylation reaction. The hydrosilylation reactions with octyl acetate and 4-heptyl acetate were investigated by multinuclear NMR spectroscopy ((1)H, (13)C, and (29)Si). This work provides evidence of the addition reaction of SiH groups onto carbonyl groups. The influence of the nature of the acetate structure on the reaction kinetics was shown and the slight contribution of side reactions at high temperature highlighted. Hydrosilylation reaction was extent to the crosslinking of ethylene-vinyl acetate (EVA) copolymer in the same range of temperature. The formation of EVA chemical network was demonstrated by HR-MAS NMR spectroscopy and by measuring the gel fraction of EVA chains in hot toluene. From Flory theory, the crosslinking density of elastic strand was calculated to be 80 mol m (3) in agreement with the measurements from swelling ratio (VA/SiH molar ratio: 11.8)

Morphology and mechanical properties of PA12/plasticized starch blends prepared by high-shear extrusion

International audiencePA12/plasticized starch blends (PA12/TPS) were prepared by high-shear twin screw extruder. The morphology development and the mechanical properties of the blends were investigated as a function of the apparent shear rate. High-shear processing has proved to be an efficient method to finely disperse thermoplastic starch in polyamide 12 matrix. Blends containing TPS domains with a size at the nano-scale (R-n similar to 150 nm) homogeneously dispersed in PA12 matrix were obtained. From a modeling point of view. the variation of the droplet radius is closer to the Wu's predictions compared to the Serpe's predictions. From the basic hypothesis of these models, it can be then assumed that compatibilization between both phases occurs during the blend processing. Furthermore, this morphology of the blends has been proved to be stable after a reprocessing step in an internal mixer most likely due to either strong hydrogen bonds between the hydroxyl groups of starch and amide groups of polyamide 12 or to potentially cross reactions between macroradicals accounting for in situ formation of graft copolymers with the potential function of compatibilizers. Mechanical properties of the blends were found to be strongly dependent on the shear rate parameter of blend processing as the mechanical properties increase with shear rate. In agreement to the blend morphology, the elongation at break of the blends was greatly improved attesting of a good adhesion between both phases

High shear processing of (PP/EPR)/Silica nanocomposites: Improvement of morphology and properties

International audienceThe aim of this article is to upgrade the performance of polypropylene/ethylene propylene rubber (PP/EPR) blends by addition of hydrophobic nanosilica (SiR805) and using "high shear processing technology". The morphological developments, mechanical and rheological properties of these composites were investigated as a function of processing conditions. High shear processing has proved to be an efficient process to decrease the size of the dispersed phase (EPR) up to 300 nm and to disperse finely nanosilica particles to less than 30 nm especially at 800 min−1. Moreover, the morphology stability of the nanocomposite is ascribed to the formation of a core shell structure (EPR nodules = core; nano-silica = shell) and selective location of nanosilica at the interface. More importantly, this core-shell structure is favoured to enhance the impact strength of the (PP/EPR)/3 wt% SiR805 nanocomposite. In agreement to the obtained morphology, the improvement (about 60 %) of elongation at break attests a good adhesion between phases due to high shear effect as highlighted by viscoelastic properties. Therefore, high shear processing technology has proved to be a relevant method to prepare nanocomposites with high performances without adding any additive and offers new perspectives for recycling and lightening structures