Spelling suggestions: "subject:"polyamide 11"" "subject:"polyamiden 11""
1 |
Fragilisation mécanique du polyamide 11 en condition d'hydrolyse : mécanisme et modélisation / Hydrolysis-Included Mechanical Embrittlement of Polyamides : Mechanisms and ModellingMaïza, Sofiane 28 September 2017 (has links)
Le polyamide 11 (PA11) est soumis à des conditions particulières d’utilisation (contraintes mécaniques, température élevée en présence d’eau) au cours desquelles ses caractéristiques mécaniques et physico-chimiques peuvent être altérées. Notamment l’hydrolyse peut générer une fragilisation du matériau par coupure des chaines macromoléculaires. On peut trouver dans la littérature des rapprochements entre propriétés macroscopiques et propriétés microstructurales afin de caractériser la transition ductile-fragile du polyamide. Mais peu d’attention a été portée jusqu’à présent sur la modélisation du comportement mécanique évoluant avec le vieillissement en lien avec la diffusion d’eau dans le matériau.L’objectif de ce travail de thèse est donc de pouvoir prédire la transition ductile-fragile des polyamides, du PA11 en particulier, au cours d’un vieillissement en température et en milieu aqueux acide.La première partie du travail de thèse a porté sur la compréhension de la dégradation mécanique du PA11 en fonction d’un vieillissement hydrique et thermique (à pH4 et à 110°C) en s’appuyant sur une campagne expérimentale afin de relier l’évolution du comportement mécanique macroscopique à celle de descripteurs physico-chimiques. Tout d’abord, des essais de vieillissement en milieu acide et en température ont été effectués pour évaluer la dégradation aux temps longs du PA11. Puis, pour décorréler les effets de l’hydrolyse des effets de recuit, des essais de vieillissement thermique uniquement, en milieu neutre, ont été réalisés. Des essais de traction à la rupture, et des essais de fluage ont ensuite été menés dans le but de mesurer d’éventuelles modifications des propriétés mécaniques au cours du vieillissement. Différentes caractérisations physico-chimiques (DSC, GPC, FTIR, viscosimétrie) ont permis de relier des changements morphologiques à différentes échelles du matériau à l’évolution de ces grandeurs mécaniques macroscopiques. Dans un second temps, une modélisation de la transition ductile-fragile du PA11 au cours du vieillissement a été mise en place. L’évolution de descripteurs physico-chimiques a été intégrée dans le formalisme d’un modèle mécanique développé à IFPEN pour rendre compte du comportement biphasique des polymères semi-cristallins. Le modèle permet de décrire l’impact du vieillissement sur le comportement mécanique du PA11, en particulier l’initiation ainsi que la propagation d’une striction le cas échéant. Enfin, une modélisation de la rupture du PA11 par fragilisation est proposée. / The prediction of the long-term behaviour of polyamides (PAs) is a major challenge for the structural design of various technological equipment in the field of energy and transport. PAs are very ductile when new, but they are sensitive to hydrolysis.Structure-properties relationships of PAs during ageing in water have been somewhat studied in literature. But little attention has been paid so far to the modeling of the mechanical behavior evolving with ageing in relation to the diffusion of water in the material.This work aims to be able to predict the ductile-brittle transition of polyamides, PA11 in particular, during ageing in temperature and acidic aqueous medium.The first part of the work focused on understanding the mechanical degradation of PA11 as a function of hydric and thermal ageing (at pH4 and at 110 ° C), based on an experimental campaign in order to link the evolution of the macroscopic mechanical behavior to that of physicochemical descriptors. First, acid and temperature ageing tests were performed to evaluate the long-term degradation of PA11. Then, in order to decorrelate the effects of the hydrolysis of the annealing effects, tests of thermal ageing only, in neutral environment, were carried out. Tensile tests at break and creep tests were then performed in order to measure possible changes in the mechanical properties during ageing. Different physicochemical characterizations (DSC, GPC, FTIR, viscosimetry) made it possible to link morphological changes at different scales of the material to the evolution of these macroscopic mechanical quantities.Secondly, a modeling of the ductile-brittle transition of PA11 during ageing was put in place. The evolution of physicochemical descriptors has been integrated into the formalism of a mechanical model developed at IFPEN to account for the biphasic behavior of semi-crystalline polymers. The model makes it possible to describe the impact of ageing on the mechanical behavior of PA11, in particular the initiation as well as the propagation of a neck if necessary. Finally, a model of the rupture of PA11 by embrittlement is proposed.
|
2 |
Etude de la morphologie, des propriétés et de la durabilité de nanocomposites à base de polyamide-11/halloysite / Study of the morpholgy, the propreties and the durability of polyamide-11/ halloysite based nanocompositesSahnoune, Mohamed 13 December 2016 (has links)
La thèse porte sur l’étude des propriétés et de la durabilité de différents systèmes nanocomposites à base de polyamide-11 (PA11) et d’halloysite algérienne. La première partie est consacrée à l’évaluation du potentiel comme nanocharge de l’halloysite algérienne, en la comparant à une autre commerciale, et ce à travers l’étude de nanocomposites PA11/halloysite préparés par voie fondue. Au vu des différentes techniques utilisées, les résultats révèlent le plein potentiel de l’halloysite algérienne avec des améliorations à la fois des propriétés thermiques et mécaniques après incorporation de la nanocharge. La seconde s’intéresse à l’utilisation de l’halloysite, après fonctionnalisation, comme agent compatibilisant dans des mélanges de polymères à base de PA11. Deux fonctionnalisations ont été testées avec succès, via greffage en surface de chaînes de P(S-co-MAPC1(OH)2) et de SEBS. L’incorporation de ces deux halloysites modifiées dans des mélanges PS/PA11 et PA11/SEBS-g-MA, respectivement, a permis d’obtenir des systèmes ternaires ou l’halloysite modifiée joue le rôle de compatibilisant en se plaçant à l’interface. La troisième et dernière partie du travail se concentre sur la durabilité des nanocomposites PA11/halloysite. D’abord, l’impact de l’halloysite jusqu’à 6 semaines d’immersion, sur la cinétique du vieillissement hygrothermique a été étudié, ainsi que les effets de ce vieillissement sur la morphologie et les propriétés des échantillons. L’étude révèle que l’halloysite augmente la sorption en eau tout en retardant sa diffusion dans le PA11 du fait de la tortuosité induite par sa présence. Une évolution de l'aspect extérieur du matériau est observée avec une diminution des propriétés mécaniques du PA11. Enfin, l’étude de la réaction au feu de nanocomposites PA11/halloysite avec et sans présence de retardateurs de flamme phosphorés a mis en évidence l’effet inhibiteur de l’halloysite après sa fonctionnalisation avec de l’acide méthylphosphonique. Les résultats montrent qu’à taux d’incorporation comparable, l’halloysite modifiée possède un meilleur effet sur le comportement au feu que le polyphosphate d’ammonium ou l’halloysite brute. / The thesis is on the study of the properties and the sustainability of different nanocomposites systems based on polyamide-11 (PA11) and Algerian halloysite. The first part is devoted to the assessment of the potential as nanofiller of the Algerian halloysite by comparing it to another commercial one, through the study of PA11/halloysite nanocomposites prepared by melt mixing. In view of the different techniques, the results show the full potential of the Algerian halloysite with improvements in both thermal and mechanical properties after incorporation of the nanocharge. The second focuses on the use of halloysite, after functionalization, as compatibilisant agent in PA11 based polymers blends. Two functionalizations have been tested successfully via grafting on the surface of P(S-co-MAPC1(OH)2) and SEBS chains. The incorporation of these two modified halloysites in PS/PA11 and PA11/SEBS-g-MA, blends, respectively, led to ternary systems where the modified halloysite plays the role of compatibilizing agent by its localization at the interface. The third and final part of the work focuses on the sustainability of the PA11/halloysite nanocomposites. First, the impact of halloysite up to 6 weeks of immersion on the kinetics of the hygrothermal aging has been studied, as well as the effects of aging on the morphology and properties of samples. The study reveals that halloysite increases water sorption while delaying its diffusion in the PA11 due to the tortuosity induced by its presence. An evolution of the outward appearance of the material is observed with a decrease of the mechanical properties of the PA11. Finally, the study of the fire reaction of the PA11/halloysite nanocomposites with and without presence of phosphorus flame retardants has highlighted the inhibitory effect of halloysite after its functionalization with methylphosphonic acid. The results show that at comparable incorporation rate, the modified halloysite has a better effect on the fire behavior than ammonium polyphosphate or raw halloysite.
|
3 |
Mécanismes et modélisation mécanique de la déformation, de l'endommagement et de la rupture du PolyAmide 11 pur et renforcé chocBoisot, Guillaume 30 June 2009 (has links) (PDF)
ARKEMA s'intéresse à la conception de matériaux thermoplastiques renforcés au choc en incorporant des particules dans le polymère pur au moment de la mise en forme et à l'effet du vieillissement hydrolitique sur ces mêmes matériaux. L'ajout d'une seconde phase de type élastomère est une technique souvent utilisée dans le but d'améliorer la résilience d'un polymère, celle-ci étant testée par essais Charpy. La présence de particules modifie les mécanismes d'endommagement par germination, croissance et coalescence de cavités soit en coeur des particules de renfort, soit à l'interface matrice-particule. La matrice des polymères renforcés de l'étude consiste en du PolyAmide 11 (PA11), un thermoplastique semi-cristallin. Ce matériau, qui possède une porosité initiale mesurée de l'ordre de 1% blanchit sous charge. Ce blanchiment est dû à une augmentation de la porosité par croissance de cavités, qui engendre une variation de volume. On s'intéresse donc aux phénomènes d'endommagement par cavitation dans les matériaux polymères, ceux-ci pouvant conduire jusqu'à la rupture finale. Dans la thèse, la compréhension des mécanismes d'endommagement est analysée aussi bien pour la matrice de PA11 neuf, pour la matrice de PA11 plastifiée et vieillie que pour deux matériaux renforcés. <br>Cette thèse montre qu'une nouvelle fois le modèle de Gurson-Tvergaard-Needleman, modèle initialement développé pour l'étude de la rupture ductile des matériaux métalliques, s'applique dans le cas d'un matériau polymère semicristallin. Le modèle s'avère pertinent pour décrire le comportement endommageable du matériau. Tout comme dans le PVDF, deux critères d'amorçage apparaissent : un critère en coalescence de cavités et un critère d'élongation des fibrilles. Les polymères se déformant rarement dans des conditions d'isothermie, l'auto-échauffement du matériau a été pris en compte en rendant les paramètres intervenant dans le modèle dépendant de la température ; les résultats s'avèrent intéressants et concordent bien avec ceux obtenus expérimentalement. La thèse met également en lumière la préservation de la ductilité par l'ajout d'une seconde phase de caoutchouc en dépit du vieillissement hydrolitique, dans une zone de température inférieure à la zone de température de transition vitreuse. Cependant nous montrons que, selon les caractéristiques de cette seconde phase, les mécanismes d'endommagement peuvent varier et ainsi le critère d'amorçage changer.
|
4 |
Fissuration fragile lente du polyamide 11 : mécanismes et durées de vie en fluageLefebvre, Xavier 19 December 2002 (has links) (PDF)
Létude a pour but de caractériser lévolution du comportement du Polyamide 11 au cours dun vieillissement thermo-mécanique de type fluage, et sintéresse en particulier à la fissuration fragile lente à 90°C.<br />En suivant lévolution de nombreux paramètres physico-chimiques, nous avons déterminé des conditions de vieillissement qui permettent dobtenir un matériau ayant des propriétés semblables à celles du matériau vieilli en service (transport de fluide).<br />La thèse démontre que le vieillissement influe fortement sur le comportement à la fissuration en fluage, et que le mécanisme dendommagement (multi-crazing) observé sur les éprouvettes est similaire à celui observé in-situ. <br />A partir des mécanismes observés, deux méthodes de détermination des durées de vie sont proposées. Dune part, à partir de courbes maîtresses présentées dans le cadre de la mécanique de la rupture en viscoplasticité avec utilisation du paramètre C*h, paramètre pertinent pour le PA11 à 90°C. Dautre part, à partir de critères locaux sur la base dune loi de comportement viscoplastique (modèle DDI). La pertinence de deux modèles dendommagement a été testée et discutée à partir dessais en mode mixte I+II.
|
5 |
Improved high velocity cold copaction processing : polymer powder to high performance partsAzhdar, Bruska January 2005 (has links)
<p>A uniaxial High-Velocity Compaction (HVC) process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with a focus on the compactibility characteristics and surface morphology of the compacted materials using various heights of relaxation assist device with different compacting profiles.</p><p>Relaxation assist device was presented as a new technique to reduce springback, pull-out phenomenon and to improve the compaction process.</p><p>The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomenon during the decompacting stage. In this study, polyamide-11 powders with different particle size distributions have been compacted with the application of different compaction profiles, e.g. different energies and velocities. It was found that the relative green density is influenced more by the pre-compacting (primary compaction step) than by the post-compacting (secondary compaction step).</p><p>Experimental results for different compaction profiles were presented showing the effect of varying the opposite velocity during the decompacting stage and how to improve the homogeneous densification between the upper and lower surface and the evenness of the upper surface of the compacted powder bed by using relaxation assists, and the influences of the relaxation assist device on the process characteristics. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. In addition, the relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be controlled by altering the height of the relaxation assist. It was found that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. Furthermore, the first gross instantaneous springback and the total elastic springback are reduced.</p><p>Two bonding strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. Scanning electron microscopy (SEM) and image computer board Camera (IC-PCI Imaging Technology) were used to the study the morphological characteristics, the limit of plastic deformation and particle bonding by plastic flow at contact points, and pull-out phenomena.</p> / QC 20100506
|
6 |
Improved high velocity cold copaction processing : polymer powder to high performance partsAzhdar, Bruska January 2005 (has links)
A uniaxial High-Velocity Compaction (HVC) process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with a focus on the compactibility characteristics and surface morphology of the compacted materials using various heights of relaxation assist device with different compacting profiles. Relaxation assist device was presented as a new technique to reduce springback, pull-out phenomenon and to improve the compaction process. The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomenon during the decompacting stage. In this study, polyamide-11 powders with different particle size distributions have been compacted with the application of different compaction profiles, e.g. different energies and velocities. It was found that the relative green density is influenced more by the pre-compacting (primary compaction step) than by the post-compacting (secondary compaction step). Experimental results for different compaction profiles were presented showing the effect of varying the opposite velocity during the decompacting stage and how to improve the homogeneous densification between the upper and lower surface and the evenness of the upper surface of the compacted powder bed by using relaxation assists, and the influences of the relaxation assist device on the process characteristics. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. In addition, the relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be controlled by altering the height of the relaxation assist. It was found that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. Furthermore, the first gross instantaneous springback and the total elastic springback are reduced. Two bonding strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. Scanning electron microscopy (SEM) and image computer board Camera (IC-PCI Imaging Technology) were used to the study the morphological characteristics, the limit of plastic deformation and particle bonding by plastic flow at contact points, and pull-out phenomena. / QC 20100506
|
7 |
[pt] COMPORTAMENTO MECÂNICO E TÉRMICO DA POLIAMIDA 11, POLIURETANO E POLIETILENO EMPREGADOS EM MANGUEIRAS DE UMBILICAIS TERMOPLÁSTICOS ANTES E APÓS ENVELHECIMENTO UV E EM AMBIENTE SALINO / [en] MECHANICAL AND THERMAL BEHAVIOR OF POLYAMIDE 11, POLYURETHANE AND POLYETHYLENE USED IN THERMOPLASTIC UMBILICAL HOSES BEFORE AND AFTER UV AGING AND IN SALINE ENVIRONMENTKARINE COSTA MACHADO MENEZES 25 July 2023 (has links)
[pt] As mangueiras termoplásticas, um dos componentes funcionais mais importantes dos
umbilicais, são compostas de tubo interno, reforço de fibra sintética e capa externa fabricada
em material termoplástico com proteção contra ozônio e radiação ultravioleta (UV). A
poliamida 11 (PA11) e o poliuretano termoplástico (TPU) são geralmente especificados para as
capas externas, mas outros materiais que atendam a função podem ser utilizados, como o
polietileno de alta densidade (PEAD). Independentemente do polímero selecionado para a
fabricação das capas, elas precisam garantir a integridade das camadas inferiores da mangueira
em um ambiente offshore severo devido à exposição constante ao sol e ao ambiente marítimo.
Não é grande a quantidade de trabalhos que estudaram e correlacionaram os efeitos da
sobreposição da radiação UV e ambiente salino nos materiais PA11, TPU e PEAD. Assim, o
objetivo deste trabalho foi comparar as propriedades mecânicas e térmicas de PA11, TPU e
PEAD, por meio de análises térmicas, espectroscópicas e de tração antes e após o
envelhecimento por UV e névoa salina, a fim de simular um mecanismo de degradação
semelhante ao da vida real das mangueiras termoplásticas e correlacionar o comportamento
termomecânico dos três materiais após o envelhecimento. Os materiais utilizados para a
fabricação das amostras deste estudo foram obtidos a partir de mangueiras não utilizadas,
extrudadas com PA11, TPU e PEAD comerciais. As capas virgens foram submetidas as análises
por infravermelho (FTIR), termogravimetria (TGA), termogravimetria derivativa (DTGA),
calorimetria exploratória diferencial (DSC) e ensaio de tração, para obtenção das propriedades
iniciais dos materiais. Em seguida, foram realizados os testes de envelhecimento, que foram
desenvolvidos em quatro ciclos. O primeiro ciclo foi o envelhecimento por UV por 720h das
amostras inicialmente na condição virgem (1° ciclo: UV), o segundo ciclo foi o envelhecimento
por névoa salina por 720h das amostras envelhecidas do primeiro ciclo (2° ciclo: UV+NS), o
terceiro ciclo foi o envelhecimento por névoa salina por 720h das amostras inicialmente na condição virgem (3° ciclo: NS) e o quarto ciclo foi o envelhecimento UV por 720h das amostras
envelhecidas do terceiro ciclo (4° ciclo: NS+UV). Após o término de cada ciclo de
envelhecimento, as amostras de PA11, TPU e PEAD foram submetidas à mesma análise das
amostras virgens para fins comparativos. No FTIR todos os materiais apresentaram redução na
intensidade dos picos característicos do material, associado a quebra de ligações das cadeias.
No PEAD ocorreu o aumento do índice de carbonila e no TPU o surgimento de novo grupo
funcional (estiramento C=C em alcenos), associados à oxidação da cadeia polimérica, cisão da
cadeia e possível reticulação. Os testes térmicos mostraram um aumento na temperatura de
degradação e pequena alteração na temperatura de fusão do PA11 associado à extração de
plastificante; no PEAD e TPU ocorreu a diminuição da estabilidade térmica dos materiais após
os envelhecimentos e não foram identificadas alterações na temperatura de fusão. Nos ensaios
de tração foi verificado no PA11 e PEAD uma diminuição do módulo de elasticidade após os
envelhecimentos, atribuída ao processo de cisão das cadeias poliméricas e consequente
diminuição da massa molar e no TPU foi observado uma tendência ao aumento da tensão na
deformação de 300% nas amostras envelhecidas por UV+NS, NS e NS+UV e uma tendência
ao aumento da tensão de ruptura nas amostras envelhecidas por NS+UV, associado a uma
concorrência entre a cisão de cadeias e reticulação. A partir dos resultados encontrados nesse
estudo, pode-se concluir que o material menos afetado com os ciclos de envelhecimento em sua
estrutura química e termicamente foi o PA11. Em relação ao comportamento mecânico, o TPU
sofreu menos influência em suas propriedades comparado aos demais materiais. / [en] Thermoplastic hoses, one of the most important functional components of umbilicals, are
composed of inner liner, synthetic fibre reinforcement and outer sheath manufactured from
thermoplastic material with protection against ozone and ultraviolet (UV) radiation. Polyamide
11 (PA11) and thermoplastic polyurethane (TPU) are generally specified for the sheaths, but
other materials that meet the function can be used, as high density polyethylene (HDPE).
Regardless of the polymer selected for the sheath manufacturing, they need to guarantee the
hose lower layers integrity in an offshore environment due to constant sun exposure and to the
maritime environment. The amount of works that studied and correlated the effects of the
overlap of UV radiation and saline environment on PA11, TPU and HDPE materials is not
large. So, the objective of this work was to compare the mechanical and thermal properties of
PA11, TPU and HDPE, by thermal, spectroscopic, and tensile analysis before and after UV and
salt spray aging, in order to reproduce a degradation mechanism similar to real life of the
thermoplastic hoses and relate the thermomechanical behavior of the three materials after aging
to evaluate the material which best suits the use of the sheath. The materials used to manufacture
the samples in this study were obtained from unused hoses, extruded with commercial PA11,
TPU and HDPE. The virgin sheaths were submitted to infrared (FTIR), thermogravimetric
(TGA), derivative thermogravimetric (DTGA), differential scanning calorimetry (DSC)
analysis and tensile test, to obtain the initial properties of the materials. Then the aging tests
were carried out, which were developed in four cycles. The first cycle was UV aging for 720h
of samples initially in the virgin condition (1st cycle: UV), the second cycle was salt spray
aging for 720h of aged samples from the first cycle (2nd cycle: UV+NS), the third cycle was
salt spray aging for 720h of samples initially in the virgin condition (3rd cycle: NS) and the
fourth cycle was UV aging for 720h of aged samples from the third cycle (4th cycle: NS+UV).
After the end of each aging cycle, the PA11, TPU and HDPE samples were submitted to the same analysis as the virgin samples for comparative purposes. In FTIR, all materials had a
reduction in the intensity of the material characteristic peaks, associated with breaking chain
bonds. In HDPE, there was an increase in the carbonyl index and in TPU, the formation of a
new functional group (C=C stretching in alkenes), associated with oxidation of the polymeric
chain, chain scission and possible crosslinking. Thermal tests showed an increase in the
degradation temperature and a small change in the melting temperature of PA11 associated with
plasticizer extraction; in HDPE and TPU, there was a decrease in the thermal stability of the
materials after aging and no changes in the melting temperature were identified. In the tensile
tests, a decrease in the modulus of elasticity was observed in PA11 and HDPE after aging,
attributed to the process of scission of the polymeric chains and consequent decrease in molar
mass, and in TPU, a tendency to increase tension in deformation of 300% was observed in the
samples aged by UV+NS, NS and NS+UV and a tendency to increase tensile strength in
samples aged by NS+UV, associated with competition between chain scission and crosslinking.
From the results found in this study, it can be concluded that the material least affected by aging
cycles in its chemical structure and thermally was PA11. Regarding the mechanical behavior,
TPU suffered less influence in its properties compared to other materials.
|
Page generated in 0.0288 seconds