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Production scientifique
Jamming, plasticité et défaillance des matériaux
(19) Production(s) de l'année 2022
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Polymer degradation in the ocean: a model for fragmentation
Auteur(s): George M., Nallet Frédéric, Fabre P.
Conference: 50e Colloque National du GFP, GFP22 (Montpellier, FR, 2022-11-21)
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Approche théorique de la fragmentation et comparaison aux données océaniques
Auteur(s): Fabre P., Nallet Frédéric, George M.
Conference: GDRPO2022 : Troisième rencontre du GDR Polymères et Océans 2022 (Brest, FR, 2022-06-27)
Ref HAL: hal-04187071_v1
Exporter : BibTex | endNote
Résumé: Depuis des années, les déchets collectés lors d’expéditions menées en mer sont triés, comptés etcaractérisés pour quantifier l’ampleur de la pollution plastique. Si la prise de conscience de la pollutionplastique était initialement liée à l'omniprésence des macro-déchets, il est désormais clair que lapollution la plus problématique est "invisible", c'est-à-dire due à des débris de plus petite taille (microet nano-plastiques) provenant de la dégradation des macro-déchets. Néanmoins , la quantité totale, ladistribution en taille des déchets plastiques dans les différents compartiments environnementaux,ainsi que leur évolution temporelle sont toujours source de questionnement. Dans l’état actuel desconnaissances, les données de terrain sur la distribution en taille des particules de plastique collectéesà la surface des océans présentent les caractéristiques suivantes. En parcourant les tailles de la plusgrande à la plus petite, un premier pic d'abondance est observé autour de 1 mm. Entre 1 mm etenviron 150 μm, on trouve très peu de particules. L'abondance augmente à nouveau de 150 μm à 10μm, avec une quantité de particules de plusieurs ordres de grandeur supérieure à celle trouvée autourde 1 mm.Dans cette présentation, nous proposerons une nouvelle approche théorique de la fragmentation d’undéchet, permettant de simuler l’évolution temporelle de l'abondance et la distribution desmicroplastiques. Nous examinerons l’influence du mode de collecte et discuterons de la pertinencedes résultats obtenus en regard des données expérimentales
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Kitchen flows: Making science more accessible,affordable, and curiosity driven
Auteur(s): Fuller Gerald G., Lisicki Maciej, Mathijssen Arnold J. T. M., Mossige Endre J. L., Pasquino Rossana, Prakash Vivek N., Ramos L.
(Article) Publié:
Physics Of Fluids, vol. 34 p.110401 (2022)
Texte intégral en Openaccess :
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Exploiting the lower disorder-to-order temperature in polystyrene-b-poly(n-butyl acrylate)-b-polystyrene triblock copolymers to increase their flow resistance at high temperature
Auteur(s): Coutouly Clement, Van ruymbeke Evelyne, Ramos L., Dieudonne-George P., Fustin Charles-andre
(Article) Publié:
Journal Of Rheology / Transactions Of The Society Of Rheology; Society Of Rheology -- Transactions, vol. 66 p.1305-1318 (2022)
Texte intégral en Openaccess :
DOI: 10.1122/8.0000506
WoS: WOS:000886063900025
Résumé: This work focuses on the temperature-dependent structural and rheological characterization of polystyrene-b-poly(n-butyl acrylate)-b-polystyrene
triblock copolymers (PS-b-PnBA-b-PS) in the melt and, in particular, on their ability to show a lower disorder-to-order temperature
(LDOT). To this aim, copolymers of varying block lengths, but keeping the PnBA block as a major component, were synthesized. Smallangle
x-ray scattering revealed that the copolymers with short PS blocks (∼10 kg/mol) approach an LDOT but do not cross it. At room temperature,
these copolymers exhibit higher moduli compared to a PnBA homopolymer due to the reinforcing effect of the PS but are flowing
at temperatures above the glass transition of the PS. Increasing the PS and PnBA block length, to keep the same PS fraction, induces more
profound changes in the structural and viscoelastic behaviors. Such a copolymer crosses the LDOT, leading to a microphase-separated and
ordered state at high temperature. Contrary to the copolymers with short PS blocks, the flow regime was not reached, even at temperatures
well above the glass transition of the PS. Instead, a low-frequency plateau was observed in rheology, showing the increased lifetime of the
microphase-separated PS domains. ABA triblock copolymers exhibiting an LDOT behavior could, thus, be of interest for the design of thermoplastic
elastomers or pressure-sensitive adhesives that can resist the flow at high temperatures
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A close look to the rim bounding a free expanding viscous liquid sheet using a time and space resolved transmittance technique
Auteur(s): Charles C.-A., Ramos L., Ligoure C.
Conference: JMC2022 (Lyon, FR, 2022-08-22)
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Colloidal physics in a drop
Auteur(s): Ramos L.
(Séminaires)
Georgetown Physics Colloquium, Georgetown University (Washington DC, US), 2022-10-25 |
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Model Gluten as Near-Critical Gels
Auteur(s): Ramos L.
Conference: 93rd Annual Meeting of The Society of Rheology (chicago, US, 2022-10-17)
Résumé: The origin of the unique rheological properties of gluten, the water-insoluble protein fraction of wheat, is crucial in bread-making processes and questions scientists since decades. Gluten is a complex mixture of monomeric and polymeric proteins. To better understand the supramolecular structure of gluten and its link to the material properties, we develop and characterize model gluten using a combination of rheology, biochemistry and scattering techniques. In this framework, we investigate the linear and non-linear viscoelastic properties of samples produced by the dispersion of gluten proteins in a solvent. We vary the quality of the solvent (various water/ethanol mixtures), the protein concentration, and the protein composition, which we finely control thanks to a novel protocol based on a liquid-liquid phase separation. We show that the complex viscoelasticity of the gels exhibits concentration/aging time/solvent composition superposition principles, demonstrating the self-similarity of the gels produced in different conditions. All gels can be regarded as near critical gels with characteristic rheological parameters, elastic plateau, and characteristic relaxation time, which are related to one another, as a consequence of self-similarity, and span several orders of magnitude when changing the parameters. Structural features probed by X-ray, neutron and light scattering experiments provide a quantitatively consistent physical picture and of near-criticality and provide crucial molecular clues of the role of intramolecular H-bonds in the gelation process. Non-linear rheology, as probed by shear start-up experiments, is also intimately related to the sample structural features.
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