5,499 research outputs found
Giono dans sa culture, actes du colloque des 27-30 mars 2001, publiés sous la direction de Jean-François Durand et Jean-Yves Laurichesse, Presses Universitaires de Perpignan/ Publications de l’Université de Montpellier-III, 2003
No full textVergnes Bruno. Giono dans sa culture, actes du colloque des 27-30 mars 2001, publiés sous la direction de Jean-François Durand et Jean-Yves Laurichesse, Presses Universitaires de Perpignan/ Publications de l’Université de Montpellier-III, 2003. In: Littératures 51,2004. Mérimée. pp. 219-223
Rheology: A sensitive technique to probe the nanofiller organization in polymer nanocomposites
No full textInternational audienceRheology was shown to be an efficient technique to probe the nanocomposite microstructure. Above the percolation threshold, the dispersed (nano)fillers form a 3D-network in the polymer matrix. The rheology allows to characterize the mechanical response of the filler network in a molten/fluid polymer matrix. Under oscillatory solicitation, in the linear viscoelastic regime, the signature at low frequency of the filler network is a constant plateau, which translates in the presence of an apparent yield stress on the viscosity curve (Figure 1). Fitting the viscosity curve with a Carreau-Yasuda low with a yield stress allows to determine the apparent yield stress. This yield stress was shown to be correlated to the dispersion state of the nanofiller and used as a descriptor of the nanocomposite microstructure at the nanoscale [1-2].It is now clear that the nanocomposite microstructure needs to be characterized at different scales. At the macroscale, SEM observations, for example, can be used to quantify the fraction of remaining agglomerates. Rheology can used to characterize the dispersion at a nanoscale. It is always interesting to couple complementary techniques to characterize the dispersion state, for example X-rays to characterize the intercalation distance between platelets in clay, TEM for a very local characterization, or dielectric measurements to determine the electrical conductivity… depending on the aimed property.Descriptors of the microstructure are very useful to put numbers to characterize the dispersion state. They can be used to quantify the effect of processing parameters during a mixing step or in next processing steps (injection…) on the microstructure [3-5], to detect the matrix degradation during the process [6]. The relationship between the microstructure descriptors and process parameters can allow to determine optimal processing conditions [7], keeping in mind the microstructure or property to be reached.The filler network is however highly sensitive to any flow, pressure and easily destroyed. Due to nanofiller interactions, the network can build-up again. These systems present a thixotropic character. Following the evolution of the moduli with time can be a good way to determine the dynamics of the network reconstruction [8-9]. The effect of the temperature on the network dynamics raises the question on the applicability of the time-temperature superposition principle. We showed that this superposition is only possible if the probed microstructure is the same. [8]The present poster will give an overview different information on the nanocomposite microstructure which can be accessed from the rheological characterization.References[1]W. Lertwimolnum, B. Vergnes, Polymer 2005, vol 46(10), 3462-3472 DOI[2]B. Vergnes, International Polymer Processing, 2011, vol 26, 229-232[3]W. Lertwimolnum, B. Vergnes, Polymer Engineering and Science 2006, vol 46, 314-323DOI[4]W. Lertwimolnum, B. Vergnes, Polymer Engineering and Science 2007, vol 47, 2100-2109 DOI[5]T. Domenech,, E. Peuvrel-Disdier, B. Vergnes, Composites Science and Technology 2013, vol 75, 7-14, DOI[6] G. Normand, E. Peuvrel-Disdier, B. Vergnes, Int. Polymer Processing, 2016, vol XXXI, 4, 508-516[7]G. Normand, E. Peuvrel-Disdier, B. Vergnes, Int. Polymer Processing, 2017, vol XXXII, 1, 129-137[8]R. Zouari, T. Domenech, B. Vergnes, E. Peuvrel-Disdier, Journal of Rheology 2012, vol 56, 725-742 HAL, DOI[9]T. Domenech,, R. Zouari, B. Vergnes, E. Peuvrel-Disdier, Macromolecules 2014, vol 47 (10), 3417–3427, DO
Structuration de nanocomposites polyoléfine/argile lamellaire en extrusion bivis corotative : Effet des paramètres d’extrusion
No full textNational audienceRésumé :Si la dispersion d’une argile lamellaire dans une matrice polyamide a connu un large engouement avec les travaux de Toyota sur les matériaux argile lamellaire/polyamide [1], la dispersion d’une argile dans une matrice polaire tel qu’un polypropylène même en présence d’agent compatibilisant reste un challenge [2-3]. Dans ce cas, l’état de dispersion de la charge doit être caractérisé à différentes échelles : échelle mésoscopique pour voir les agglomérats mal dispersés (microscopie électronique à balayage) et nanométrique pour voir l’état d’exfoliation de la charge (microscopie électronique en transmission, mais surtout la rhéologie). Différents travaux ont montré la relation entre le comportement rhéologique du nanocomposite en dynamique (mesures dans le domaine de viscoélasticité linéaire) et l’état d’exfoliation de la charge [4].Une première étude menée sur l’étape de dilution d’un mélange maître par extrusion bi-vis a permis de montrer que l’augmentation de l’énergie mécanique spécifique fournie au matériau au cours de l’extrusion entraîne une amélioration de l’état de dispersion avec une saturation de l’état de dispersion de l’argile au-delà d’une certaine valeur d’énergie [5-6].Dans le présent travail, les nanocomposites ont été préparés par voie directe en extrusion bi-vis. Nous avons étudié l’effet de la vitesse de rotation des vis sur l’état de dispersion du nanocomposite en sortie de filière, mais aussi sur l’évolution de l’état de dispersion le long du profil de vis. Nous nous sommes plus particulièrement intéressés à l’effet de fortes vitesses de rotation. L’état de dispersion de la charge a été, dans tous les cas, caractérisé à différentes échelles. Les résultats montrent qu’une faible vitesse de rotation permet de disperser l’argile, que l’augmentation de la vitesse permet d’améliorer l’état de dispersion mais que cet effet est limité par la dégradation des chaînes polymères à forte vitesse.Références:[1] Y. Kojima, A. Usuki, M. Kawasumi, A. Okada, Y. Fukushima, T. Kurauch, O. Kamigaito J. Mater. Res. 1993, 8,1185-1189.[2] M. Kawasumi, N. Hasegawa, M. Kato, A. Usuki, A. Okada. Macromol. 1997, 30, 6333-38.[3] W. Lertwimolnun, B. Vergnes. Polymer 2005; 46, 3462-3471.[4] B. Vergnes. Int. Polym. Proc. 2011, 26, 229-232.[5] T. Domenech, E. Peuvrel-Disdier, B. Vergnes. Int. Polym. Proc. 2012, 5, 517-526.[6] T. Domenech, E. Peuvrel-Disdier, B. Vergnes. Compos. Sci. Technol. 2013, 75, 7-14.Remerciements:Les recherches menant aux présents résultats ont bénéficié d'un soutien financier du septième programme-cadre de l'Union européenne (7ePC/2007-2013) en vertu de la convention de subvention n° 314744
Introducing “La fabrique du droit”. A Conversation with Bruno Latour
No full textBruno Latour talks with Paolo Landri about his book on the Conseil d'Etat (La Fabrique du droit). The conversation was held in 2006 at the time of the Italian translation of the book and illustrates the research project and the difficulties the author had in the field. At the same time, it clarifies the trajectories of Bruno Latour's work and theoretical framework of his program of study with respect to sociology, anthropology, and philosophy of law. The conversation helps to understand the open-ended character of Bruno Latour's research and reflection including STS as well as sociological, anthropological and philosophical themes
Structuration of organoclay/polypropylene nanocomposites during twin screw extrusion process
No full textInternational audienceSummary :Reaching nanoscale dispersion of the layered silicate within polypropylene (PP) matrix is challenging and requires both the use of a compatibilizer and optimal processing method. We showed in a previous work that the specific mechanical energy received during extrusion was the key parameter controlling this microstructure with a saturation of the dispersion state above a certain level of energy [1-2].The present study aims at better understanding the effect of the specific mechanical energy on the dispersion process. Nanocomposites of polypropylene, maleated polypropylene and organomodified montmorillonite were prepared in a co-rotating twin-screw extruder by direct mixing. The effect of the specific mechanical energy was investigated by varying extrusion parameters such as the screw speed, the barrel temperature and changing the matrix viscosity level. A particular attention was paid to high screw speed conditions. Dead stop experiments were conducted and the nanocomposite structure was followed along the screw profile. The structure was systematically quantified via scanning and transmission electron microscopy, X-ray diffraction and dynamic rheometry in to order to analyse the structure at different scales.A clear relationship is once again shown between the specific mechanical energy given to the system and the organoclay dispersion state with a saturation above a certain screw speed. This saturation was shown to be related to the thermo-mechanical degradation of polymer chains. The effect of the polymer chain degradation on dispersion will be discussed.References:[1] T. Domenech, E. Peuvrel-Disdier, B. Vergnes. Int. Polym. Proc. 2012, 5, 517-526.[2] T. Domenech, E. Peuvrel-Disdier, B. Vergnes. Compos. Sci. Technol. 2013, 75, 7-14.Acknowledgements:The research leading to these results has received funding from the Seventh Framework Programme of the European Union (FP7 / 2007-2013) under grant agreement n ° 314744
Author Correction: Collection of the digital data from the neurological examination.
No full textIn this article, the corresponding author was inadvertently designated only to “Bruno Kusznir Vitturi” but it should have been “Bruno Kusznir Vitturi” and “Walter Maetzler”. The original article has been corrected
Préparation des composites à fibres lignocellulosiques en extrusion bivis
No full textInternational audienceDans ce chapitre, nous allons nous intéresser à la préparation de composites thermoplastiques à fibres lignocellulosiques par compoundage en extrudeuse bivis. Après avoir rappelé les problèmes spécifiques et les difficultés particulières liées à ce type de fibres, nous présenterons un certain nombre de résultats expérimentaux, mettant en évidence les paramètres procédé importants et leur influence sur la morphologie des fibres. Nous montrerons ensuite comment la modélisation des écoulements permet de mieux interpréter ces résultats et d'aller, à travers une approche prédictive de la casse des fibres, vers l'optimisation du procédé de compoundage et son extrapolation de l'échelle laboratoire à l'échelle industrielle
On Bruno Schulz’s Bookplates
No full textThe Polish version of the article was published in Roczniki Humanistyczne vol. 64, issue 1 (2016).
The article enters into a dialogue with the interpretation of Bruno Schulz’s bookplates made by Władysław Panas in his book Bruno od Mesjasza (Bruno of the Messiah) (Lublin 2001). An attempt to understand them in a different (less holistic) way leads the author of the article to the conclusion that in Schulz’s plates the first veiled variant of the mythical Book may be seen—of the fundamental motif of Bruno Schulz’s later literary work
Jordan "Bruno" Gegenhuber '16 Publishes First-Author Research
No full textJordan "Bruno" Gegenhuber '16 had first-author research, "Gene regulation by gonadal hormone receptors underlies brain sex differences," published in nature magazine on May 4, 2022.Jordan "Bruno" Gegenhuber '16 had first-author research, "Gene regulation by gonadal hormone receptors underlies brain sex differences," published in Nature magazine on May 4, 2022.
Sex hormones play a central role in shaping behavior throughout the animal kingdom, and this study maps where the receptor for estrogen binds to DNA in neurons that regulate rodent social interactions. The findings reveal that estrogen establishes lasting sex differences in gene expression and neuroanatomy during brain development, and identifies hundreds of genes that may mediate estrogen's effects on behavior and disease.
Gegenhuber earned a PhD from the Cold Springs Harbor Laboratory School of Biological Sciences in Long Island, N.Y.. in May 2022. His field of research is in neuroscience, and he has accepted a postdoctoral research position at Harvard Medical Center in Boston, Mass. He also holds the honor of being the Pacific Class of 2016 Valedictorian
Préparation des composites à fibres lignocellulosiques en extrusion bivis
No full textInternational audienceDans ce chapitre, nous allons nous intéresser à la préparation de composites thermoplastiques à fibres lignocellulosiques par compoundage en extrudeuse bivis. Après avoir rappelé les problèmes spécifiques et les difficultés particulières liées à ce type de fibres, nous présenterons un certain nombre de résultats expérimentaux, mettant en évidence les paramètres procédé importants et leur influence sur la morphologie des fibres. Nous montrerons ensuite comment la modélisation des écoulements permet de mieux interpréter ces résultats et d'aller, à travers une approche prédictive de la casse des fibres, vers l'optimisation du procédé de compoundage et son extrapolation de l'échelle laboratoire à l'échelle industrielle
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