Polymérisation radicalaire contrôlée de l'[alpha]-fluoroacrylate de n-butyle

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Hyperelastic behavior of modified sepiolite/SEBS thermoplastic elastomers

International audienceThin elastomer films of styrene-ethylene-butylene-styrene block copolymer (SEBS) filled with sepiolite nanofibers nanocomposites were prepared by a dip-coating process. To increase the SEBS/Sepiolite elastomer performances, a new strategy of surface modification of sepiolite by SEBS polymer chains has been developed. In a first part the surface modification of sepiolite was characterized by FTIR and TGA. In a second part the mechanical properties of the filled SEBS films were assessed. Measurements of tensile properties and tear strength were carried to evaluate the impact of the sepiolite modification. These results are discussed in taking account the filler dispersion and the quality of the SEBS/sepiolite interface. The surface modification of the sepiolite nanofibers shows an interesting improvement of the tear strength without major modifications of SEBS matrix intrinsic hyperelastic behavior

Kinetic and thermodynamic parameters guiding the localization of regioselectively modified kaolin platelets into a PS/PA6 co-continuous blend

International audienceThis article highlights the role of kinetic and thermodynamic parameters on the localization of modified kaolin platelets into a high interfacial tension co-continuous PS/PA6 blend after extrusion, injection molding and annealing. Three kinds of copolymers were synthesized and grafted on kaolin: poly(styrene-co-(methacryloyloxy)methyl phosphonic acid) copolymer (P(S-co-MAPC1(OH)2)), polystyrene terminated 3-(mercaptopropyl)triethoxysilane, (ETS-PS) and poly(styrene-co-3-methacryloxypropyltrimethoxysilane) copolymer, (P(S-co-MPS)). Those copolymers were distinguished by (1) the nature of their functional groups (phosphonic acid that reacts only with aluminol groups or alkoxysilane that reacts with both silanol and aluminol groups), (2) the amount of functional groups and (3) their molecular weights. After functionalization the kaolin samples (K1, K2 and K3, respectively) were analyzed by FTIR, TGA and Py-GC/MS to evaluate the grafting. It was shown that P(S-co-MAPC1(OH)2) and P(S-co-MPS) copolymers grafted on kaolin led to highly anisotropic K1 and K3 kaolin platelets, respectively. Then, 50/50/5 PS/PA6/Ki samples (i = 0 to 3) were processed as follows: (1) kaolin platelets were dispersed (via solvent cast) into the PS phase. Then, (2) PS + kaolin were melt mixed by microcompounder with PA6, then (3) the PS/PA6/Ki were injection molded into disks and finally (4) they were annealed (via dynamic or quiescent annealing). Thanks to the high shear rate and longtime of mixing during extrusion (microcompounder), all the kaolin platelets (unmodified K, K1, K2 and K3) crossed the interface and were localized in the PA6 phase. All Ki kaolin stayed in the PA6 phase during injection. However, after annealing (quiescent or dynamic), the localization of the nanoplatelets was guided by thermodynamic parameters, and SEM analysis revealed the segregation of K1 and K3 kaolin platelets at the polymers interface, with a high tendency to impede polymer phases coalescence. Hence, modified K1 and K3 kaolin are promising compatibilizing agents for a co-continuous PS/PA6 blend

Modification de fibres naturelles par radiogreffage

National audienceLes fibres naturelles d’origine végétale suscitent un vif intérêt dans de nombreux domaines (textile, construction, automobile, maritime). Certaines de leurs caractéristiques comme leur inflammabilité ainsi que leur hydrophilie représentent cependant des inconvénients majeurs pour de nombreuses applications. Des recherches sont aujourd’hui menées dans les milieux académique et industriel pour développer des méthodes efficaces de fonctionnalisation ou de modification de surface de ces fibres pour améliorer leurs performances. A cet égard, le radio greffage, reposant sur l’usage de rayonnements ionisants (gamma ou e-beam) représente une méthode pertinente par rapport aux méthodes chimiques ou enzymatiques classiques. Elle permet de générer sur les fibres des radicaux ou des groupes fonctionnels permettant le greffage de molécules d’intérêt offrant alors un large spectre de possibilités pour la modification des fibres [1][2]. Néanmoins, les modifications induites par ce traitement sont dépendantes d’un grand nombre de facteurs, dont notamment la structure du substrat qui influence la nature et la quantité des espèces actives formées. Pour évaluer son importance et mieux comprendre l’impact de ce paramètre, la Résonnance Paramagnétique Electronique (RPE) semble être un outil de choix. Cette présentation vise alors à exposer les conclusions tirées de l’application de cette technique à l’étude de fibres naturelles irradiées

A One-Step Approach for a Durable and Highly Hydrophobic Coating for Flax Fabrics for Self-Cleaning Application

Highly hydrophobic flax fabrics with durable properties were prepared using the “dip-coating” method for self-cleaning application. Flax fabrics were coated with a polysiloxane coating via a hydrosilylation reaction with a Karstedt catalyst at room temperature. The coated fabrics displayed highly and durable hydrophobic properties (contact angle and sliding angle of about 145° and 23°, respectively) with good self-cleaning ability for certain pollutants and excellent durability. Moreover, the influence of the coating process on the mechanical properties of fabrics was investigated. A decrease in E modulus and an increase in tensile stress at maximum force and elongation at maximum force has been observed. Furthermore, this influence of the coating process can be easily controlled by adjusting the proportion of curing agent in the treatment solution

h-BN Modification Using Several Hydroxylation and Grafting Methods and Their Incorporation into a PMMA/PA6 Polymer Blend

International audienceHexagonal boron nitride (h-BN) has recently gained much attention due to its high thermal conductivity and low electrical conductivity. In this study, we proposed to evaluate the impact of the modification of h-BN for use in a polymethylmethacrylate/polyamide 6 (PMMA/PA6) polymer blend. Different methods to modify h-BN particles and improve their affinity with polymers were proposed. The modification was performed in two steps: (1) a hydroxylation step for which three different routes were used: calcination, acidic treatment, and ball milling using gallic acid; (2) a grafting step for which four different silane agents were used, carrying different molecular or macromolecular groups: the octadecyl group (Si-C18), propyl amine group (Si-NH2), polystyrene chain (Si-PS), and PMMA chain (Si-PMMA). The modified h-BN samples after hydroxylation and functionalization were characterized by FTIR and TGA. Py-GC/MS was also used to prove the successful graft with Si-C18 groups. Sedimentation tests and multiple light scattering were performed to assess the surface modification of h-BN. Granulometry and SEM observations were performed to evaluate the particle size distribution after hydroxylation. After the addition of Si-PMMA modified h-BN into a PMMA/PA6 co-continuous blend, the morphology of the polymer blend nanocomposites was characterized using SEM. The calculation of the wetting parameter based on the surface tension measurement using the liquid drop model showed that h-BN dispersed in the PA6 phase. Grafting PMMA chains onto hydroxylated h-BN particles combined with an adequate sequence mixing led to a successful localization of the grafted h-BN particles at the interface of the PMMA/PA6 blend

Nanotubes d’Halloysite (HNTs) comme retardateurs de flamme dans des mélanges PE/EVA pour des applications en câblerie

International audienceDe nouvelles réglementations pour la protection de la santé et de l’environnement comme les Euroclasses poussent les industriels de la câblerie à se renouveler. Ils se doivent d’intégrer ces normes tout en continuant à améliorer les propriétés mécaniques et électriques, ainsi que le comportement au feu et le vieillissement des câbles. A l’heure actuelle, les matériaux utilisés pour les gaines des câbles sont des mélanges de polymères chargés en hydroxyde d’aluminium (ATH) ou en polyphosphate d’ammonium (APP). Des taux de charges élevés sont nécessaires pour améliorer le comportement au feu, cependant ils impactent défavorablement la flexibilité de la gaine ou sa sensibilité à l’eau. L’approche menée dans le cadre du projet HAREDY vise à améliorer les performances au feu des matériaux et également à retarder leur vieillissement hygro- et hydrothermique

Synthesis of telechelic oligomers by atom transfer radical polymerization: A study of acrylate monomers

International audienceDifferent acrylate oligomers were synthesized by atom transfer radical polymerization in the presence of a transfer agent and CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine. The functionality in bromine was determined by 1H NMR. These oligomers were coupled in the presence of Cu(0) and the ligand 2,2-bipyridine. The coupling yield was determined by size exclusion chromatography and NMR analysis and depended on the nature of the monomer and not on the molecular weight. In other words, the preliminary functionalization of the brominated chain end with styrene increased the coupling yield

Improvement of Nafion®-sepiolite composite membranes for PEMFC with sulfo-fluorinated sepiolite.

International audienceA new composite membrane based on Nafion® loaded with sulfo-fluorinated sepiolite was prepared, characterized and tested in a membrane electrode assembly in fuel cell operating conditions. Pristine sepiolite, a natural microfibrous and highly hygroscopic clay, was first modified so as to make it proton conductive on one hand and to increase compatibility with Nafion® on the other hand. The proton conductivity was ensured through sulfonic acid groups while compatibility with Nafion® through fluorination of the grafted group. The functionalization was characterized with titration, thermal analysis, pyrolysis-GCMS, FTIR and NMR. A mean graft concentration equivalent to 0.08 mmol/g was calculated which in this case also equals the ion exchange capacity of the modified sepiolite. The composite membrane showed improved mechanical resistance (elastic modulus doubled for 10 wt% added sepiolite), unchanged IEC and larger water uptake compared to pure Nafion® membrane. The mechanical resistance was even better than that of our composite membrane previously prepared with sulfonated only sepiolite, most probably due to fluorination. MEA performances were also significantly improved, especially at 100 °C and low RH (+50% more output power at 0.6 V at 50%RH)

Assessment of olive pomace wastes as flame retardants

International audienceOlive pomace (OP) is a lignocellulosic waste from olive oil industry. In order to valorize these wastes as flame retardant (FR) fillers into polymers, OP residues are milled and screened into three different fractions. Two strategies are then investigated. The first one is to modify OP particles by phosphorus molecules using radiation grafting as already done successfully with flax. Nevertheless, pyrolysis combustion flow calorimetry analyses show that the introduction of phosphorus does not promote charring of OP and flame retardancy is not significantly improved whichever the considered fraction. The second strategy is to replace pentaerythritol by OP as char source into well‐known FR systems based on ammonium polyphosphate. The incorporation of such system into ethylene‐vinyl acetate copolymer leads to satisfying FR performances according to cone calorimeter tests. Moreover, the presence of high amount of extractives into OP such as oleic acid does not appear detrimental