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Numerical Simulation of Recycled PET Preforms Infrared Heating Including Force Convection Effect in the Industrial ISBM Ovens
No full textInternational audienceNowadays, injection stretch blow molding (ISBM) process represents the most employed technology to produce plastic bottles. An important step of this process is the heat conditioning stage which is performed within infrared ovens by the use of powerful halogen lamps. Homogenizing the temperature distribution along and inside the preform at the end of this conditioning stage is one of the key parameters to determine the final quality of the bottle (thickness, mechanical properties, transparency...). In this research work, a numerical software has been developed to simulate recycled PET (rPET) preforms infrared heating inside the industrial ISBM ovens, where both rotation and translation of the preform across different heating modules occur. In addition, the presence of a fan system involving a forced convective condition inside the ovens is also considered using a Computational Fluid Dynamics (CFD) approach instead of using a conventional heat transfer coefficient
Influence of fiber/matrix interface on gas permeability properties of CF/TP composites
No full textInternational audienceOne of the main properties to be satisfied in hydrogen applications is low gas permeability. In composite materials, this property depends on the processing parameters and in particular on the residual porosity, but also on the quality of the fiber/matrix interface. This is particularly the case in composites involving a thermoplastic matrix with carbon fibers as the lack of reactive group on the fiber surface can limit the level of interfacial interaction between the reinforcement and the matrix. In this study, the role of the interface is therefore analyzed through the investigation of the hydrogen permeability of CF/PVDF and CF/PPS composites manufactured with different grades of polymers and reinforcements. The hydrogen permeability of the composites was determined, and a correlation with the crystallization behavior of the matrix on the fiber surface could be identified. Hydrogen permeation decreases when the fiber favors matrix nucleation
Moussage de biocomposites PLA-fibres végétales par des procédés assistés par CO2 supercritique
No full textInternational audienceDans de nombreux domaines industriels, le développement de structures composites polymères poreuses et légères présente un grand intérêt en raison de leurs nombreux avantages par rapport à un solide massif de même composition. Ces structures moussées sont utilisées dans les industries du sport, de la pharmacie, de l'aéronautique et de l'emballage, par exemple. Les thermoplastiques pétrosourcés sont largement utilisés mais en raison de la raréfaction inexorable des ressources fossiles et des enjeux environnementaux actuels, les biopolymères (polymère biosourcé, biodégradable et/ou biocompatible) sont de plus en plus utilisés. Il existe deux voies principales pour produire des mousses polymères en fonction de l'agent moussant utilisé, qui peut être chimique (CBA) ou physique (PBA). Les CBA sont capables de libérer un gaz lors de la décomposition thermique mais ils présentent certains inconvénients, parmi lesquels la nécessité de températures de traitement élevées, la rémanence de résidus solides dans la mousse et leur toxicité. Les PBA apparaissant comme une alternative à ces agents chimiques. Le CO 2 et le N 2 supercritiques sont les plus utilisés (Chauvet et al, 2017). Le procédé de moussage de polymères assisté par fluide supercritique est très souvent effectué dans un autoclave, procédé discontinu (ou batch). Les échantillons sont saturés en gaz sous pression et leur moussage est réalisé en induisant une instabilité dans le système. La solubilité des gaz dans les polymères augmente avec la pression mais diminue avec la température. Par conséquent, l'instabilité peut être induite par une chute brutale de pression ou par une élévation de température provoquant ainsi le moussage du polymère. L’extrusion moussage est quant à lui un processus continu dans lequel le gaz injecté dans le fourreau de l'extrudeuse agit comme plastifiant et comme agent moussant lors de la détente en sortie de filière (Villamil Jiménez et al, 2020). Cette technologie de moussage a été utilisée pour différents polymères, y compris les composites à base de PLA avec du CO 2 supercritique en tant qu’agent moussant. Les fibres de cellulose (Boissard et al,2012), de jute (Zafar et al, 2018) et la farine de bois (Neagu et al, 2012) ont été étudiés comme charges dans les mousses PLA. Les conditions opératoires, la nature et la teneur des charges ont une grande influence sur la morphologie, la texture et la structure finale de la mousse. En général, les charges modifient la cinétique de cristallisation et améliorent la résistance à l'état fondu du PLA. L’utilisation de charges permet d’obtenir des mousses dont le taux d'expansion est réduit par rapport aux mousses de PLA pur, augmentant ainsi la densité cellulaire et réduisant la taille des cellules. Ce travail a pour but d'expliquer les effets de la taille, du rapport d'aspect et de la teneur en fibres de cellulose utilisées en tant que charges sur les caractéristiques des mousses de PLA. Celles-ci ont été obtenues par procédés assistés par CO 2 supercritique suivant les deux modes de mise en œuvre : en voie continue et discontinue. L’effet de ces deux voies sur les propriétés des mousses n'a encore jamais été étudié
EFFECT OF PROCESS PARAMETERS ON IMPACT ON COMPOSITES AND COMPRESSION AFTER IMPACT
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Identifying at molecular scale the pyrolysis heavy components from two lignin monomers
No full textInternational audience4-hydroxy benzaldehyde (H) and vanillin (G) are typical primary pyrolysis products of β-O-4 lignin dimers with key functional groups that affect the secondary reactions of lignin pyrolysis. In this study, the pyrolysis heavy components from these two lignin monomers were analyzed and identified at molecular scale for the first time with Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR-MS) and compared with lignin-derived results. The detected heavy components were typically phenolic oligomers distributed in the nominal mass range of 200–600 Da with 2–6 aromatic rings. They are assumed to be formed through the re-polymerization of certain GC-MS-detected monomers during pyrolysis. In particular, the extra methoxy group in model compound G allows for more variations of monomer products, which serve as building blocks to form heavy components and char. Two-dimensional Kendrick mass defect (2D KMD) analysis was employed to reveal the evolution of different functional groups. Two evolution pathways were found to be dominant, namely the modification of phenol cores and methoxy groups. It was found that aldehyde groups promoted the evolution of heavy components with more aromatic rings (up to 6), which might serve as precursors for char. This influence was mitigated by the co-existence of methoxy group, which might compete for the linking positions on benzene rings
CO 2 Solubility Modelling in Non-Precipitating Aqueous Solutions of Potassium Lysinate
No full textInternational audienceModelling of CO 2 solubility in aqueous solutions of potassium lysinate (LysK) is mainly hindered by scarcity of experimental vapor-liquid equilibrium data and lack of chemical equilibrium constants associated to the reaction mechanism for the CO 2 /LysK/H 2 O system. Therefore, Kent-Eisenberg (KE) correlation stands out from the literature, being among the most used approaches for the description of the equilibrium CO 2 partial pressure at different loadings. In this work, a Kent-Eisenberg-like approach has been developed, enhancing the empirical Kent-Eisenberg with Debye-Hückel activity coefficients in order to guide model calibration with reference to selected experimental data for CO 2 solubility in 33.1 and 33.5% w/w aqueous LysK solution; moreover, the KE edition provides an estimation of the missing equilibrium constants. This information has been embedded in a first thermodynamically sound and predictive Deshmukh-Mather (DM) model (average absolute deviation equal to 7%) validated against additional experimental data in a wide temperature and concentration range
Introduction to Hydroxyapatite-based Materials in Heterogeneous Catalysis
No full textInternational audienceThe objective of this chapter is to introduce hydroxyapatite (HA) and HA-based materials in the field of the heterogeneous catalysis. The chapter mostly focuses on the properties of these materials, such as ion exchange capacity, acidity-basicity, and thermal stability, which make them specially attractive for application in heterogeneous catalysis. Opportunities and challenges of HA and HA-based materials in the field of catalysis are also briefly summarized
Infrared heating modeling of recycled PET preforms in injection stretch blow molding process
No full textInternational audienceRelatively recent citizen’s consciousness about plastic pollution forces industrial actors of packaging to re-invent their shaping processes and materials. Specifically, for plastic bottle industry shaping, classical Polyethylene Terephthalate (PET) material is little by little replaced by recycled PET (rPET). The change in material composition due to recycling loops leads to an inevitable adaptation of the Injection Stretch Blow Molding (ISBM) process used to shape bottles at a satisfactory production rate. Indeed, rPET contains contaminants which modify its optical properties, so the heating stage becomes material-dependent and unstable regarding the polymer supplier. The approach adopted in this article is to build a numerical model able to simulate the infrared heating of rPET preforms, sensitive enough to predict changes in temperature due to the recycling rate. To do so, the optical properties of 50% and 100% rPET are measured by spectrometry and implemented in the simulation. Thermal radiative heat transfer between infrared lamps and rPET preforms is simulated by ray tracing method using an in-house software so-called RAYHEAT. Then, the result of the infrared ray tracing computation is used as the input heat source for thermal simulation by commercial software COMSOL Multiphysic® in order to simulate the temperature distribution of the preform. The numerical results are then confronted to experimental ones obtained on a research Stretch Blow Molding pilot, instrumented with thermography. The results show that the temperature obtained at the end of a classical heating cycle of the 100% recycled grade is 8 °C higher than the virgin one. Also, simulations confirm that this difference is attributed to changes in optical properties. Finally, heating 100% rPET at a sufficient forming temperature is about 8% less energy consuming than for virgin PET
A methodology for developing evidence-based optimization models in humanitarian logistics
No full textInternational audienceAbstract The growing need for humanitarian assistance has inspired an increasing amount of academic publications in the field of humanitarian logistics. Over the past two decades, the humanitarian logistics literature has developed a powerful toolbox of standardized problem formulations to address problems ranging from distribution to scheduling or locations planning. At the same time, the humanitarian field is quickly evolving, and problem formulations heavily rely on the context, leading to calls for more evidence-based research. While mixed methods research designs provide a promising avenue to embed research in the reality of the field, there is a lack of rigorous mixed methods research designs tailored to translating field findings into relevant HL optimization models. In this paper, we set out to address this gap by providing a systematic mixed methods research design for HL problem in disasters response. The methodology includes eight steps taking into account specifics of humanitarian disasters. We illustrate our methodology by applying it to the 2015 Nepal earthquake response, resulting in two evidence-based HL optimization models
Size effects on high temperature oxidation of MCrAlY coatings processed via APS and HVOF depositions
No full textInternational audienceThe paper demonstrates how defects inherited from the deposition processes can severely impair the lifetime of MCrAlY coatings in service. The oxidation behavior of two NiCoCrAlY coatings was investigated at 1150 °C up to 500 h. The coatings had the same nominal composition but were processed by two different projection techniques: air plasma spray (APS) and high velocity oxy fuel (HVOF). Freestanding coating specimens were extracted from the coated system and thinned down to different thicknesses ranging from 400 to 15 μm in order to investigate size effects inherent to the oxidation response. The oxidation rate of the APS coating was found to be insensitive to the specimen thickness, while that of the HVOF coating increased with the specimen thickness, due to greater intersplat oxidation. APS specimens thinner than 60 μm experienced intrinsic chemical failure (InCF) due to Al consumption to form the Al2O3 scale. In comparison, HVOF specimens with a thickness of 367 μm were subject to InCF after 250–350 h oxidation. This first stage of InCF resulted in the formation of a Cr2O3 layer at the Al2O3/metal interface once Al activity in the MCrAlY coating was low enough to thermodynamically allow Cr2O3 to form. In addition, thick HVOF specimens developed mechanically induced chemical failure (MICF) resulting in the formation of (Ni,Co)(Cr,Al)2O4 spinels on top of the Al2O3 scale and within oxide intrusions. The occurrence of MICF was associated with the concomitant effects of Al consumption due to intrusive oxidation and the spallation of the external Al2O3 scale