Oxidation induced changes in viscoelastic properties of a thermostable epoxy matrix

The thermal ageing of a neat epoxy matrix has been studied at 200°C in air by three complementary analytical techniques: optical microscopy, mechanical spectrometry and nano-indentation. Thermal oxidation is restricted in a superficial layer of about 195 µm of maximal thickness. It consists in a predominant chain scission process involving, in particular, chemical groups whose β motions have the highest degree of cooperativity and thus, are responsible for the high temperature side of β dissipation band. As a result, chain scissions decrease catastrophically the glass transition temperature, but also increase significantly the storage modulus at glassy plateau between Tβ and Tα. This phenomenon is called “internal antiplasticization”. Starting from these observations, the Di Marzio and Gilbert’s theories have been used in order to establish relationships between the glass transition temperature and number of chain scissions, and between the storage modulus and β transition activity respectively. The challenge is now to establish a relationship between the transition activity and the concentration of the corresponding chemical group

POLYMERIZATION OF COMPOSITE MATERIALS IN FREE SPACE ENVIRONMENT

ABSTRACT Light-initiated curing of composite in free space environment appears as one of the most promising processes to turn a foldable, inflatable prepreg into a rigid, load-bearing structure [1]. This paper presents activities aiming at the development of composite materials that complies with the strong requirements associated with in orbit curing, such as stability, flexibility and low outgassing in the uncured state, together with reactivity for rigidization and sufficient mechanical performances in the cured state. The cationic polymerization of epoxy monomer was selected as polymerization process, and dedicated copolymers had to be synthesized to obtain a satisfying material. The obtained results allowed for the successful manufacturing, rigidization and testing of several breadboards

Thermo-oxidation behaviour of organic matrix composite materials at high temperatures

The present paper is a review of the main activities carried out within the context of the COMPTINN‟ program, a joint research project founded by a FUI program (Fonds Unifiés Interministériels) in which four research teams focused on the thermo-oxidation behaviour of HTS-TACTIX carbon-epoxy composite at „high‟ temperatures (120°C-180°C). The scientific aim of the COMPTINN‟ program was to better identify, with a multi-scale approach, the link between the physico-chemical mechanisms involved in thermo-oxidation phenomena, and to provide theoretical and numerical tools for predicting the mechanical behaviour of aged composite materials including damage onset and development

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field

Rigidification de structures gonflables pour satellites par photopolymérisation d'époxydes

L utilisation d éléments de structures rigides gonflables doit permettre de réduire la masse, le volume en configuration pliée, ainsi que les coûts de fabrication d'éléments structuraux attachés aux satellites artificiels. Dans ce contexte, une technologie permettant le durcissement d un composite multicouche par voie photochimique a été développée. La polymérisation de résines époxy amorcées par un complexe d'hexafluorophosphate cyclopentadiènyle-Fe(II)-arène a été retenue comme voie privilégiée pour la rigidification des structures. Des composés modèles ont d'abord été étudiés, sous un angle fondamental, dans le but d examiner les étapes clef du processus de polymérisation photo-amorcée et de développer des méthodes quantitatives de suivi et de modélisation des phénomènes afin d apporter des éléments de compréhension en vue d une meilleure maîtrise du procédé. La contrainte de la faible teneur en composés volatils a ensuite été intégrée dans la recherche de nouvelles formulations compatibles avec un usage spatial, d abord en se tournant vers des prépolymères époxy commerciaux. Afin d obtenir les propriétés thermomécaniques désirées, il est apparu nécessaire de se tourner vers la synthèse sur mesure de copolymères réactifs à base de méthacrylate de glycidyle. Le point clef étant de contrôler les propriétés antagonistes d une faible viscosité (poids moléculaires pas trop élevés) et d une faible teneur en composés volatils. Divers outils d ingénierie macromoléculaire ont été utilisés pour jouer sur l architecture moléculaire, la teneur en fonctions réactives et les masses molaires.The development of original concepts such as inflatable and rigidizable structures for satellite appendages is driving the need for in-orbit rigidization technologies. Polymerization of composite in free space environment appears as one of the most promising processes among those envisioned to turn a foldable, inflatable structure into a rigid, load-bearing structure. In this context, the polymerization of epoxy resins photoinitiated by a Fe(II) cationic complex of methylnaphthalene was developed for the rigidization of inflatable structures. Model compounds were first studied from a fundamental point of view, in order to examine the key steps of the cationic photoinitiated polymerization reaction and to develop quantitative methods for monitoring and modeling the different steps of the curing reaction. The constraint of low content in volatile compounds in the uncured materials was then taking into account by considering commercial reactive prepolymers. For obtaining the desired thermomechanical properties, it become necessary to move towards the synthesis of reactive copolymers including glycidyle methacrylate units. The key point is to control the antagonistic properties of low viscosity (molecular weight not too high) and low content in volatile compounds. Various macromolecular engineering tools were used to obtain the desired architecture, with appropriate content in reactive functions and molecular weight.REIMS-BU Sciences (514542101) / SudocSudocFranceF

Une clientèle envahissante ? Les temporalités des avocat·es en droit de la famille

À partir d’une enquête collective menée dans les cabinets de plusieurs juridictions, cet article étudie le rapport au temps et au travail d’avocat·es en droit de la famille. Nuançant les travaux montrant des avocat·es qui maîtrisent l’interaction avec les client·es, il analyse comment des professionnel·les peuvent se sentir envahi·es. Les avocat·es déclarent d’autant plus être débordé·es que la norme de disponibilité permanente reste très ancrée, même si elle est mise à mal par la féminisation de la profession. La gestion de leur relation avec la clientèle correspond ainsi à différentes logiques d’articulation des temps sociaux, à l’intersection des rapports de genre, des configurations familiales dans lesquels ils et elles sont pris et de leur position dans la carrière. Enfin selon leur place dans le marché du conseil, la composition de leur clientèle ou la taille de leur cabinet, les avocat·es n’ont pas les mêmes ressources pour face à cet envahissement. Les inégalités de genre, de situation professionnelle et de territoire sont alors déterminantes.This article analyzes the relationship to time and work of family lawyers based on a collective survey conducted in law firms in several jurisdictions. This article nuances the studies highlighting the lawyers' control of interaction and analyzes how professionals can feel overwhelmed in their relationship with clients. The impression of being overwhelmed is all the more intene that that the norm of permanent availability remains very rooted, even if it is undermined by the feminization of the profession. Lawyers' management of their relationship with their clients thus corresponds to different logics of articulation of social times, to the intersection of gender relations, the family configurations in which they are caught and their position in the career. Finally, depending on their place in the legal advice market, the composition of their clientele or the size of their practice, lawyers do not lawyers have the same resources to deal with this invasion. Inequalities in terms of gender, professional situation and territory are therefore a determining factor.A partir de una investigación colectiva llevada a cabo en los despachos de varias jurisdicciones, este artículo estudia la relación en el tiempo y en el trabajo de abogados(as) en derecho familiar. Al matizar los trabajos que muestran abogados(as) quienes manejan la interacción con los(as) clientes, analiza cómo los(as) profesionales pueden sentirse invadidos(as). Los(as) abogados(as) declaran estar tanto más abrumados(as) cuanto que la norma de disponibilidad permanente sigue estando muy arraigada, incluso si está en riesgo por la feminización de la profesión. De este modo, el manejo de su relación con la clientela corresponde a diferentes lógicas de articulación de los tiempos sociales, a la intersección de las relaciones de género, configuraciones familiares en las cuales ellos y ellas se encuentran, y de su posición en la carrera. Finalmente, según su lugar en el mercado del consejo legal, la composición de su clientela o el tamaño de su bufete, los(as) abogados(as) no tienen los mismos recursos para hacer frente a esta invasión. Las desigualdades de género, de situación profesional y de territorio son, por lo tanto, determinantes

Une clientèle envahissante ? Les temporalités des avocat·es en droit de la famille

International audienc

Étude exploratoire sur la médiation culturelle et artistique des tout-petits à Mille Formes

International audienc

Radiation-initiated cationic polymerization of epoxy monomers for demanding applications: formulation design and processing

International audienc

Recent advances in the radiation-induced polymerization of epoxy-based resins: reactivity, network structure and material performances

International audienceRecent advances in the radiation-induced polymerization of epoxy-based resins: reactivity, network structure and material performance