Relaxation of loose agglomerates of magnesium hydroxide in a polymer melt

International audienceThe study of agglomerates of magnesiumhydroxide badly dispersed in an olefinic polymer by means of oscillatory shear flow in the melt indicates that the agglomerates behave as a distinct phase. Optical and rheo-optical measurements carried out on these agglomerates also show that they are wetted by the melt and that they can be easily deformed under shear. However, the relaxation of shape in oscillatory shear is also the trace of the existence of an effective interfacial tension between the agglomerates containing high amounts of filler and the polymer matrix. The analogy with the behavior of polymer blends and the modeling by the Palierne model enables the calculation of such an interfacial tension. The surface free energy of magnesiumhydroxide that can be calculated from this result by a simple mixing law is 95 mN m−1. This value is compared with data from the literature on brucite and similar minerals

Rhéocinétique lors de la polymérisation avec séparation de phase dans un système thermoplastique/thermodurcissable.

4 p.Pour les matériaux polymères, la combinaison de l'écoulement et de la réaction chimique dans un outillage de transformation permet de générer in situ des structures ou des morphologies particulières à l'origine de nouvelles propriétés. Le contrôle du procédé requiert alors la connaissance de l'évolution de la rhéologie du système pendant la réaction chimique (rhéocinétique). Le travail exposé s'attache à décrire l'évolution des modules dynamiques d'un système complexe thermoplastique/thermodurcissable (polystyrène/époxy-amine) lors de la polymérisation du thermodurcissable. Les précurseurs du réseau sont initialement miscibles à haute température mais une séparation de phase sous forme de nodules sphériques intervient en cours de polymérisation. Des mesures microcalorimétriques de l'évolution de la transition vitreuse du thermoplastique et des observations en microscopie de la séparation de phase ont été réalisées. L'évolution des modules du système complexe au cours du temps a été suivie en rhéométrie dynamique. Sur cette base expérimentale, un modèle rhéocinétique prédictif des modules de perte et de conservation a été développé. Il intègre les phénomènes de séparation de phase, de variation de la température de transition vitreuse, de dilution des enchevêtrements de la phase TP dans le cadre d'un modèle d'émulsion généralisé à partir des modules dynamiques du TP et du TD en cours de polymérisation. La généralisation du modèle d'émulsion est réalisée en prenant en compte les interactions entre les particules de phase dispersée au delà du seuil de percolation mécanique sous la forme d'une loi de mélange

Synthesis of branched poly(butylene succinate): Structure properties relationship

International audience; A series of branched poly(butylene succinate) (PBS) were synthesized with several branching agents namely trimethylol propane (TMP), malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and H-1-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased

Polymer foaming with chemical blowing agents: Experiment and modeling

International audienceAn experimental and theoretical analysis of the polypropylene foaming process using three different chemical blowing agents (CBA) was performed. A simple experiment was designed to analyze the foaming process of polypropylene (PP)/CO2 system under two different pressure conditions. The expansion ratio and final foam structure was measured both by direct observation and from optical measurements and image analysis, showing a good agreement. A single bubble simulation based on relevant differential scanning calorimetry and thermo-gravimetrical analysis experiments, assuming each CBA particles as a nucleation site and accounting for gas diffusion in the surrounding polymer matrix has been built. The sensitivity of the model to physical and processing parameters has been tested. The calculation results are compared to the experiments and open the route to a simplified method for evaluating the efficiency of CBA

Mediating gel formation from structurally controlled poly(electrolytes) through multiple "head-to-body" electrostatic interactions

Tuning the chain-end functionality of a short-chain cationic homopolymer, owing to the nature of the initiator used in the ATRP polymerisation step, can be used to mediate the formation of a gel of this poly(electrolyte) in water. While a neutral end group gives a solution of low viscosity, a highly homogeneous gel is obtained with a phosphonate anionic moiety, as characterized by rheometry and diffusion NMR. This novel type of supramolecular control over poly(electrolytic) gel formation could find potential use in a variety of applications in the field of electroactive materials

Polymères et emballage alimentaire

Conférence en universitéInternational audienc

Utilisation de charge lamellaire dans les élastomères: exemple du phosphate de zirconium

International audienc

Elaboration et proprietes d'alliages polyamide-ABS. Influence d'un compatibilisant obtenu par greffage a l'etat fondu d'anhydride maleique sur l'ABS

SIGLEINIST T 74655 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Effets viscoélastiques liés à la présence d'agglomérats dans les polymères chargés

National audienc

Effets viscoélastiques liés à la présence d'agglomérats dans les polymères chargés

National audienc