Orientador: Marco-Aurelio De Paoli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-21T05:15:05Z (GMT). No. of bitstreams: 1 Araujo_JoyceRodriguesde_D.pdf: 3671133 bytes, checksum: c0208a3fbc4c962177c7cf09361d5293 (MD5) Previous issue date: 2012 / Resumo: Materiais antiestáticos têm aplicações tecnológicas muito diversificadas. Seu principal objetivo é dissipar a eletricidade estática que pode acumular em sua superfície reduzindo o risco de ocorrência de faíscas. Trabalhos anteriores mostraram que a fibra de Curauá atua como agente de reforço em matrizes termoplásticas, como polietileno, polipropileno e poliamida-6. Comprovada a eficiência da fibra de Curauá em promover o efeito de reforço em matrizes termoplásticas com vantagens em relação a outras fibras vegetais, buscou-se neste trabalho aliar propriedades elétricas às excelentes propriedades mecânicas destes compósitos recobrindo as fibras vegetais com um polímero condutor, a polianilina, PAni. Na primeira parte deste trabalho, os compósitos foram processados em uma mini-extrusora contra-rotatória utilizando baixo teor de FC-PAni (de 5 a 15 wt%). Além de promover condutividade elétrica, foi observado que as fibras modificadas aumentaram a eficácia do efeito de reforço das fibras de curauá na matriz poliamida-6 devido ao aumento da adesão interfacial entre a matriz e a fibra. Na segunda parte deste trabalho, foi desenvolvido o método de preparação em escala piloto da FC-PAni e as mesmas foram incorporadas à matriz polimérica (em teores de 5 até 30 wt%) em uma extrusora dupla-rosca co-rotante interpenetrante e os corpos de prova foram moldados por injeção. Os compósitos foram caracterizados por ensaios mecânicos, ensaios de índice de fluidez do fundido, condutividade elétrica e microscopia eletrônica de varredura. As propriedades eletroquímicas dos compósitos e da PAni pura foram investigadas por voltametria cíclica, enquanto que o estado de oxidação da PAni foi verificado por espectroscopia de fotoelétrons excitados por raios-X e UV-visível. Os resultados obtidos mostraram que o recobrimento das fibras com a polianilina ocorreu de maneira uniforme e promoveu um aumento da interação entre as fibras e a poliamida-6 devido à hidrofilicidade de ambos / Abstract: Antistatic materials have very diverse technological applications. Its main purpose is to dissipate static electricity that can accumulate on the surface of a polymer, reducing the risk of sparks. Previous studies have shown that Curauá fibers act as a reinforcing agent for thermoplastic matrices, such as polyethylene, polypropylene and polyamide-6. Proven efficiency of Curauá fibers in promoting the reinforcement effect, with advantages in relation to other vegetable fibers, the aim of this study is to combine the mechanical properties of these fibers with the electrical properties of the polyaniline, PAni. In the first part of this work, the composites were prepared in a counter-rotating mini-extruder using low content of CF-PAni (5 to 15 wt%). The addition of PAni coated curauá fibers to the polyamide-6 generated electrical conductivity and also improved the reinforcement effect of the fiber in the matrix due to the improvement of matrix-fiber interfacial adhesion. In the second part of this work, polyaniline was prepared and deposited on the surface of the fibers on a pilot plant scale and the composites were prepared by extrusion and injection molding (fiber content of 5 to 30 wt%) . The composites were characterized by electrical conductivity measurements using the four-probe method. The electrochemical properties and the doping degree of the PAni coated curauá fibers were evaluated by cyclic voltammetry and UV-vis spectroscopy. The effect of the PAni coating on the mechanical properties of the composites was evaluated by tensile, flexural and impact tests. The morphology was studied by scanning electron microscopy. The chemical interaction between polyaniline, polyamide-6 and curauá fibers was analyzed by infrared spectroscopy and X-ray Photoelectron Spectroscopy. The results showed that the polyaniline coating was uniform and increased the chemical interaction between the fibers and polyamide-6 due to the hydrophilicity of both / Doutorado / Quimica Inorganica / Doutora em Ciências

Blends of poly(vinylidene fluoride) (PVDF) and polyamide 6 (N6) are interesting for both scientific studies and commercial exploitation. PVDF is known to be miscible with polymers produced from monomers containing carbonyl side groups, eg. polyethyl acrylate, polyacrylamide etc., but is not miscible with polymers containing carbonyl groups in the main chain, ego polyamides, polyester, etc. Although complete miscibility of the blend components is not always necessary, strong physical interactions between the two components are needed in order to obtain a compatible blend, i.e. one which exhibits good mechanical properties. An investigation was carried out to explore the possibility to compatibilise blends of PVDF and N6 using y-radiation to graft acid groups on either polymer and subsequently ionomerizing these with zinc cations. Graft copolymer type of compatibilizer was produced when the acid functionalized PVDF (grafted PVDF) was blended with N6 or acid functionalized N6 (grafted N6). Fourier transform infrared analysis has confirmed the occurance of reactions between acid groups in the grafted PVDFand amine groups in the N6. The compatibility of the PVDF/N6 blends was found to increase with increasing amount of carboxylic acid groups in the two polymers. This was accompanied by an increase in Tg of the N6 phase in blend, which became more pronounced when both components were grafted. Tensile test and solvent resistance experiments were carried out to relate the compatibization of the blend to the improvement in mechanical properties. Ionomerization of the functionalized polymers with zinc cations was performed in order to study the effect on compatibility of the blend. The neutralization of the acid groups in either polymer in the blend by addition of zinc acetyl acetonate was found to suppress the chemical reaction with the amine end groups in the N6 phase, and to cause a reduction in the T g and a reduction in crosslinking of the N 6 phase. However when both polymers were grafted, the crystallinity of the N6 phase was restored, which was accompanied by an increase in Tg.

Philosophiae Doctor - PhD / Organic and inorganic pollutants are two broad classes of pollutants in the environment with their main sources from waste waters that are indiscriminately dumped from chemical related industries. Among the organic pollutants are dyes that come as effluents from the textile industries. Toxic metals are the main inorganic pollutants with their sources from industries such as mining, electroplating, batteries etc. The presence of both classes of pollutants in the aquatic environment poses a serious threat to aquatic organisms and humans who depend on these waters for domestic purpose. Therefore, this research focused on the fabrication of materials and designing of methods for removal of both classes of pollutants from their aqueous solutions.

Les engrenages en matériau polymère présentent de nombreux avantages par rapport aux aciers. Ils sont plus légers, résistants à la corrosion, fonctionne sans lubrifiant et leurs coûts de revient est moindre grâce au moulage par injection. Ils sont de plus en plus utilisés dans des domaines variés, mais se limitent à la transmission de mouvement. L’ajout de fibre de verre courte permet d’augmenter leur tenue mécanique et de diversifier leur domaine d’utilisation à des transmissions de petite à moyenne puissance. Le polyamide (Nylon) renforcé de fibres de verre est le composite le plus couramment utilisé dans le domaine des engrenages. Néanmoins, son comportement viscoélastique ainsi que la présence de fibres introduit une difficulté supplémentaire dans la modélisation. En outre, le comportement viscoélastique dépend de la température et pour le Polyamide, de l’humidité. Par conséquent, la viscoélasticité impacte directement la répartition des charges, l’erreur de transmission sous charge, la raideur d’engrènement. Dans cette thèse, une méthode numérique originale modélisant le comportement mécanique des engrenages en Polyamide 6 renforcé de fibre de verre est proposée. L’approche utilise le modèle rhéologique linéaire de Kelvin généralisé pour simuler le comportement viscoélastique du matériau et prendre en compte la température, l’humidité ainsi que le taux de fibre et leur anisotropie. Ensuite ce modèle rhéologique est intégré dans le modèle quasi-statique du partage des charges développé par le LaMCoS. Ce processus de calcul permet d’obtenir les résultats essentiels pour les engrenages (répartition des charges, pressions de contact, erreur de transmission sous charge, raideur d’engrènement) avec un temps de calcul assez court. Afin de de valider les modèles numériques développés, un banc d’essai a été mis en place, permettant la mesure de l'erreur de transmission et la visualisation de la température de l’engrenage pendant son fonctionnement. / Polymer gears present several advantages: they can be used without lubricant, their meshing is silencer, resistance to corrosion is better, weight is reduced. However they have a poor heat resistance and are limited to rotation transmission. In order to improve the gears performance, glass fibre reinforcement is being increasingly used, where their lower cost and higher strength, compared to unreinforced polyamide, offer a potential increase in gear performance. Mechanical behaviour of polymers materials is very complex; it depends on time, history of displacement, temperature and for several polymers, on humidity. Moreover, an addition of fibres can make the material properties heterogeneous and anisotropic. The particular case of Polyamide 6 + 30% glass fibres which is the most common fibre reinforced plastic is studied in this work. In the first part of this work, a mould was developed to better control the material choice and moulding conditions. Using tomographic observations, investigations were done to better understand the relation between moulding conditions, gears geometry and fibres orientation. Based on these observations and with the help of mechanical characterisation, a linear rheological generalized-Kelvin model was developed to simulate the viscoelastic behavior of the polymer material. In a second part, this model taking into account temperature, humidity and rotation speed is integrated in quasi-static load sharing computation developed by the LaMCoS laboratory. In the load sharing calculus, the displacements are obtained on a large meshing covering the entire surface of the tooth. This relation integrates the viscoelastic displacement, the fibre orientation and the geometrical influence coefficients. The method permits to obtain results such as the loaded transmission error, the instantaneous meshing stiffness, the load sharing and the root tooth stress at different temperature, humidity and rotation speeds within a reasonable computation time. Investigation have shown interesting results regarding the historic of displacements which represents up to 15% of the total displacement at the tip radius, the localization of the maximal tooth root stress, which is the same than metal gears, or the influence of the thermal expansion toward transmission error. On another hand, we have highlighted the low difference between a realistic description of the fibre orientation and an homogeneous anisotropic one. The last step concerns the validation of the numerical. The measurements are carried out on a test bench developed at the LaMCoS laboratory. It provides two experimental results: the temperature of the gear during operation, and the load transmission error using optical encoders to measure the angular positions of the pinion and the gear. This one is global enough to validate the three steps of the model: geometry, kinematics and load sharing.

Les réservoirs composites de type IV utilisés pour le stockage de l’hydrogène gazeux rencontrent du succès dans les applications mobiles de la pile à combustible. Au cours de leur utilisation, ces supports de stockage sont soumis à des cycles successifs de remplissage/maintien/vidange en hydrogène. Sous des conditions spécifiques de vidange, l’apparition d’un décollement entre l’enveloppe en polyamide 6 qui assure l’étanchéité (liner) et la paroi composite, peut être observée. Ce décollement, encore appelé collapse, peut poser des problèmes de limitation à un débit de vidange lent ou à un seuil minimal de pression résiduelle du gaz sur le liner.Air Liquide a cherché à élucider expérimentalement l’influence des cycles de pression en hydrogène sur le comportement mécanique des liners en situation de collapse. Mais compte tenu des coûts très élevés des essais, l’utilisation d’un outil numérique prédictif s’avérait nécessaire. L’enjeu principal dans le développement d’un tel outil était la modélisation du comportement d’un liner collapsé sous des chargements de cyclage – fluage.L’objectif de cette thèse est de proposer une loi de comportement capable de prédire l’évolution cyclique de la déformée d’un liner en situation collapsée.Le liner est exposé à plusieurs variations de son environnement : présence d’un résidu d’humidité dans le liner après épreuve hydraulique, variations de températures générées par la compression/détente de l’hydrogène, diffusion de l’hydrogène dans le liner. Un travail préliminaire a donc consisté à évaluer l’influence de ces différents facteurs environnementaux sur la réponse mécanique du polyamide 6. Cette première étape a permis de définir un cadre de sollicitation à l’échelle du laboratoire, mais qui préserve les principales caractéristiques du collapse. Les essais de caractérisation sur éprouvette ont montré que le liner pouvait être modélisé par une loi viscoélastique multiaxiale formulée dans le cadre thermodynamique des processus irréversibles en petites déformations, faiblement couplée avec la thermique. Des modifications mineures ont été introduites pour permettre à cette loi de capter les effets du comportement en fatigue-fluage d’un liner en situation collapsé. Ces modifications ont malheureusement pénalisé l’identification manuelle et par conséquent, ont conduit à développer une stratégie d’identification spécifique. La qualité de d’identification a été évaluée dans le cadre isotherme en regardant les effets de la vitesse de la sollicitation, du niveau de contrainte et de la température. Puis, le modèle a été validé en présence de transitoires thermiques, d’abord sur éprouvette, ensuite dans un réservoir en présence d’un collapse. / Hyperbaric hydrogen storage vessels of type IV are encountering success for portable applications of fuel cell. During their use, these cylindric containers undergo repeated fill in/fill out cycles of H2-gaz. Under specific fillout conditions, an emerging detachment between the sealing inner layer (liner) and the composite wall, can be observed. This layer debonding also called collapse may limit the pressure release rate of H2-vessels or increase the residual gas pressure prescribed to avoid collapse.Experimental studies have been conducted by Air Liquide at vessel scale to identify some parameters responsible for the collapse onset. But the high cost of these studies and the complexity of the operating conditions makes the use of numerical tools necessary. That led to a numerical modeling approach. The main goal in the numerical approach is to model the cyclic mechanical response of a collapsed liner under fatigue – creep loadings.In this thesis, the purpose was to develop a mechanical constitutive law able to predict the cyclic deformation of a collapsed liner subjected to hydrogen pressure cycles.The liner was subjected to several environment variations due to: (i) the presence of residual water into the liner after initial hydraulic vessel tests, (ii) the temperature changes caused by the hydrogen compression/expansion, and (iii) the hydrogen diffusion/saturation. So, a preliminary work consisted in investigating the influence of each environmental factor on the polyamide 6 mechanical response. This first step allowed to outline a loading frame at laboratory scale that preserved main characteristics of the collapse phenomenon. Characterization tests on tensile specimens revealed that the liner could be modelled by a non linear viscoelastic law written within the thermodynamic framework of the irreversible processes in small deformations, and coupled with the temperature. Minor changes were introduced to extend the model capacity to capture liner behavior effects during fatigue – creep. These changes had negative impact on the manual method of model calibration, and consequently required to develop a specific identification strategy. The identification performance was assessed in different isothermal frames through stress rate, stress level and temperature effects. Then, the calibrated model was validated by taking temperature gradients into account, firstly on a tensile specimen, secondly within a H2-vessel.

Starch is a natural polymer occurring in the seeds, tubers and stems of many plants, including maize. It is a mixture of two polymers: linear amylose and highly branched amylopectin. The ratio and the molar masses of the two polymers depend on the starch source, giving rise to different starch properties. Thermoplastic starch (TPS) was obtained by gelatinising a dry-blend mixture of maize starch, water, plasticisers and additives in a single-screw laboratory extruder. The TPS formed is a translucent amorphous material that could be shaped into pellets and injection-moulded into a variety of articles, just like conventional plastics [Shogren et al., 1994]. The advantages of TPS are that it is cheap and fully biodegradable. However, because of its hydrophilic nature, its properties and dimensional stability are influenced by moisture (humidity). It is also not easily processed like conventional plastics and the freshly moulded material ages, i.e. its properties change over time. The latter is caused by retrogradational structural changes which include helix formation and the crystallisation that occurs above the glass transition temperature [Myllärinen et al., 2002]. The unacceptable physical and processing properties of TPS were improved by blending with other polymers. The objective of this work was to determine the effects of water and glycerol content and the starch source or type on the mechanical properties of maize-based TPS. In addition, the effect of gypsum filler and polyamides or polyvinyl butyral (PVB) as modifying agent was also investigated. The PVB was based on material recycled from automotive windscreens. As with the thermoplastic starch, the thermoplastic/polymer blends, e.g. polyvinyl butyral, were also prepared using a single-screw extruder. After pelletisation, the materials were conditioned at 30 °C and a relative humidity of 60%. Tensile test specimens were prepared by injection moulding. Samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and tensile testing. The effect of environmental conditions (temperature and humidity or water submersion) on the ageing of the samples was investigated using tensile properties as a measure. Initial extrusion and moulding trials revealed that the TPS compounds were very difficult to process. Difficulties were encountered with feeding the dry blends into the compounding extruder. The moulded samples adhered strongly to the mould walls, especially the sprue part. These problems were overcome by adding 2,5% precipitated silica to improve the flowability of the dry blends and stearyl alcohol at ca. 1,5% as a processing aid. The latter performed as an external lubricant and mould-release agent. Nevertheless, for some compositions it was also necessary to use ‘Spray-and-Cook’ as mould-release agent during injection moulding. The results show that HiMaizeTM, a high-amylose maize starch, provided the best properties in TPS and its blends. Further improvements in properties were obtained by blending with low-molecular-weight hot-melt adhesive-grade polyamides (Euremelt 2138 and 2140), engineering polyamide (EMS Grilon CF 62 BSE) or low amounts of PVB. The properties of all the compounds investigated were affected by moisture content and also by ageing. The TPS-PVB blends showed highly non-linear composition-dependence. SEM and DMA revealed a phase separation for all the TPS-PVB blend compositions investigated. The tensile properties were negatively affected by ageing in a high-humidity environment and they deteriorated rapidly when the samples were soaked in water. Synergistic property enhancement was observed for a compound containing 22% thermoplastic starch. It featured a higher tensile strength, showed better water resistance and was significantly less affected by ageing. At higher PVB levels, the property dropped to values that were lower than expected from the linear blending rule. / Thesis (PhD)--University of Pretoria, 2008. / Chemical Engineering / unrestricted

Solvent suspensions of a high performance polymer, Polyamide-imide (PAI) are widely used in magnetic wire coatings. Here we investigate the effect that the introduction of montmorillonite (MMT) has on PAI. MMT was introduced into an uncured PAI suspension; the sample was then cured by step-wise heat treatment. Polarized optical microscopy was used to choose the best suitable MMT for PAI matrix and to study the distribution of MMT in PAI matrix. Concentration dependent dispersion effect was studied by x-ray diffraction (XRD) and was confirmed by Transmission electron microscopy (TEM). Differential scanning Calorimetry (DSC) and Thermogravimetric analysis (TGA) was used to study impact of MMT on glass transition temperature (Tg) and degradation properties of PAI respectively. Micro-hardness testing of PAI nanocomposites was also performed. A concentration dependent state of dispersion was obtained. The glass transition (Tg), degradation and mechanical properties were found to correlate to the state of dispersion.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20929号 / 理博第4381号 / 新制||理||1630(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 杉山 弘, 教授 三木 邦夫, 教授 秋山 芳展 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The purpose of this work is to understand the reasons for varied mechanical properties among three polymer Powder Bed Fusion (PBF) Additive Manufacturing (AM) processes. Parts for this work were manufactured from Polyamide 12 (PA12) using the Laser Powder Bed Fusion (L-PBF), Multi-Jet Fusion (MJF), and the recently developed Large Area Projection Sintering (LAPS) processes. Previous works have shown that LAPS parts demonstrate significantly higher density, ductility, and toughness than parts from the L-PBF and MJF processes. A hot isostatic pressing (HIP) treatment was developed to reduce porosity in L-PBF and MJF parts and determine if increasing part density would improve ductility for these processes. It is found that density is not strongly correlated with mechanical properties for high density parts (ρ > 0.98 g/cm3) for the L-PBF and MJF processes, and a following study confirms that this is the case for the LAPS process as well. Differential Scanning Calorimetry (DSC) and microtome sectioning are performed on parts from all three processes, and it is found that neither percent crystallinity nor crystalline morphology are strongly correlated with mechanical properties. A heat treatment at temperatures well over the melting point for the material is developed and is shown to improve ductility and toughness for all three processes. It is concluded that the improved ductility observed in the LAPS process stems from long exposure to high temperature, rather than increased density or a specific crystalline structure, and is associated with post-condensation reactions increasing polymer chain length. Work is also presented on the development of a production-scale LAPS system at Ascend Manufacturing. This research focuses on the results of "tiling" and "scanning" methods for producing larger parts than previously possible with prototype LAPS systems. Tensile testing showed that the methods both produced parts with similar properties, though with lower ductility than previous LAPS parts. Analysis of thermal data identifies areas for improvement of the system to attain high strength and high ductility parts. Preliminary work is done to demonstrate avenues for process improvement. Analysis of data from across the entire powder bed shows that process defects can be observed from the thermal data available in the LAPS process, and that weak spots in parts may be related to this data. Finally, the potential for process improvement through a multiple-input, multiple-output (MIMO) control scheme is discussed.

学位プログラム名: 京都大学大学院思修館 / 京都大学 / 新制・課程博士 / 博士(総合学術) / 甲第23345号 / 総総博第18号 / 新制||総総||3(附属図書館) / 京都大学大学院総合生存学館総合生存学専攻 / (主査)教授 山敷 庸亮, 教授 杉山 弘, 教授 積山 薫 / 学位規則第4条第1項該当 / Doctor of Philosophy / Kyoto University / DGAM