Dissertations / Theses on the topic 'PA6'

Neste trabalho foi feita uma avaliação da compatibilização das blendas de Polipropileno (PP)/Poliamida-6 (PA6) e das blendas Poliamida-6/Borracha Etileno- Propileno (EPR). No primeiro sistema, foi utilizando como agente compatibilizante o PP funcionalizado Polybond 3002 e no segundo sistema, foi utilizando o EPR funcionalizado como agente compatibilizante. As blendas binárias PP/PA6 foram preparadas nas proporções 70/30 e as misturas ternárias PP/PP-MA/PA6 nas proporções 65/5/30, ambas foram processadas em Extrusora Haake Rheomex PTW e Extrusora Haake Rheomex CTW100p. A blenda binária PA6/EPR foi preparada na proporção 70/30 e a blenda ternária PA6/EPR-MA/EPR na proporção 70/25 e processadas em Reômetro de torque Haake Polylab com módulo misturador interno fechado. O gente compatibilizante EPR-MA foi funcionalizado em Extrusora Haake Rheomex PTW utilizando concentração de anidrido maleico (MA) de 1% e de 0,1% do iniciador Luperox. As blendas obtidas foram caracterizadas por Calorimetria Diferencial de Varredura (DSC), Microscopia Eletrônica de Varredura (MEV), análises Termodinâmico Mecânica (DMTA), análises reológicas além de análise mecânica. Alguns resultados passaram por uma análise estatística através do teste t para uma melhor confiabilidade nos resultados apresentados no trabalho. Os resultados mostraram que a adição do agente compatibilizante PP-MA e EPRMA provoca uma alteração na morfologia das blendas, apresentando uma melhor miscibilidade e redução do tamanho das partículas dispersas. Além disso, as análises térmicas, dinâmico-mecânicas e reológicas demonstraram um indício da interação entre as fases causado pela compatibilização. A análise mecânica das blendas PP/PA6 mostrou um melhor desempenho das blendas ternárias em comparação as blendas binárias.
In this work an evaluation of the compatibilization of the Polypropylene (PP)/Polyamide-6 (PA6) blends and Polyamide-6/Ethylene-Propylene Rubber (EPR) blends was carried out. A funcionalized PP and a funcionalized EPR were used as compatibilizer agent in the first and second systems, respectively. The binary blends PP/PA6 were prepared in the proportions 70/30 and the ternary mixtures PP/PP-MA/PA6 in the proportions 65/5/30, both in Haake Rheomex PTW Extruder and Haake Rheomex CTW100p Extruder. The binary blend PA6/EPR was prepared in the proportion 70/30 and the ternary blend PA6/EPR-MA/EPR in the proportion 70/5/25, using a Haake Polylab Rheometer with internal mixer module. The compatibilizer agent EPR-MA was prepared in a Haake Rheomex PTW Extruder functionalized with 1 wt % of maleic anhydride (MA) as grafting agent and 0.1% of Luperox as initiator. The obtained blends were characterized for Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Dynamic Mechanical Thermal Analysis (DMTA), roational rheometry and mechanical properties measurements. When necessary the significance of the differences among samples was statically analyzed using a t test. The results showed that the addition of the compatibilizer agents PP-MA and EPRMA provokes an alteration in the morphology of the blends, increasing miscibility and reducing the size of the dispersed phase particles. Besides, the dynamic-mechanical thermal and rheological analyses indicate interaction between the phases caused by the compatibilization. The mechanical analysis of the blends PP/PA6 showed a better performance of the ternary blends in comparison to the binary blends.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Ciência e Engenharia de Materiais
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Thermophysiological comfort is one of the most important factors for people to choose desirable gar-ments, which can be evaluated via measuring permeability of body heat and sweat. In this paper the water vapor permeability of nanocomposite nylon 6 fabrics produced from melt spun nanocomposite yarns with different TiO2 nanoparticle concentrations have been investigated. Results from measuring water vapor permeability at different environment temperatures for 4 h. indicated that sample with 0.4 wt% of TiO2 nanoparticle can provide fabric with maximum comfort properties. At low temperature 27.5% decline of permeability as compared to pure fabric causes this sample to protect body from cool weather through pre-venting loss of body heat. By increasing temperature from 12 to 35 oC water vapor permeability enhance-ment of nanocomposite improved about 99% as compared to pure one. Consequently nanocomposite with suitable nanoparticle content can provide more comfortable fabrics in different temperatures and applica-tions. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35603

Thesis (M.Sc.)--City University of Hong Kong, 2004.
At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.

In recent decades, polymeric nanocomposites have been widely used in chemical, automobile and aero industries due to their low weight and smoothness. Abrasion resistance is a vital property in variable ap-plications of polymeric composites. Here, to investigate the wear resistance of nylon 6 nanocomposite fab-rics, melt spun yarns were filled with different concentrations of Ag/SiO2 nanoparticles and the wear prop-erties of weft knitted nanocomposite and pure samples were evaluated. Results disclosed that the wear re-sistance of composite fabrics containing nano-particles increased considerably in comparison to pure one. Therefore, nanoparticles can play an important role in improving the nanocomposite wear resistance. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35638

The aim of this research was to study the structure-property relationships of polyamide 6 (PA6) micro- and nanocomposites produced using two particulate carbon fillers; namely graphite, G, and graphite nanoplatelet, GNP. The GNP and G are similar in lateral dimensions, but differ greatly in their thickness (by at least an order of magnitude), the size-scale of which defines G as a micron-scale filler and GNP as a nano-scale filler, and consequently, the specific surface area available for matrix interaction and the aspect ratio of each filler also differed significantly. Size scale was considered in the choice of processes to incorporate the G and GNP into a PA6 matrix. Firstly, in situ polymerisation using anionic polymerisation of epsilon caprolactam (EC), which enabled polymer/carbon interactions on the molecular scale and, secondly, melt extrusion using commercial grade PA6 as the matrix. For the G-based studies, composites with at least five stepwise incorporations between 5-25 wt. % loading were produced; whereas GNP was incorporated at loadings an order of magnitude lower (0.5-2.5 wt. %) reflecting their difference in size-scale. For both G and GNP, composites were produced via in situ polymerisation and by melt processing using a Haake Minilab bench-scale twin screw extruder, (TSE) in two groups which compare the effects of processing conditions. In in situ polymerisation, processing conditions designed to deliver the same sonication power were used and were coded as 40/10 (a sonication amplitude of 40% was applied for 10 minutes to disperse carbon filler in the molten EC) and 20/20 (sonication amplitude of 20% for 20 minutes). Similarly, in melt extrusion processing conditions designed to deliver the same strain magnitude were used and were coded as 200/3 (screw frequency of 200 rpm was applied for 3 minutes) and 100/6 (100 rpm for 6 minutes). A ninth G-based system (GL) was produced using an industrial lab-scale TSE for occasional cross-comparison with the bench-scale processed systems. All systems were characterised using thermal analysis (DSC, TGA, DMTA), tensile testing, impedance spectroscopy and electron microscopy. Overall, the best property increases were observed for the 20/20 processing conditions for the in situ polymerised systems and the 100/6 processing conditions for the melt extruded. The 20/20 in situ processing condition produced a dispersed state where particle aspect ratio was retained and less particle fragmentation occurred, the latter also giving higher reaction rates (and hence a higher molecular weight matrix) compared to the 40/10 processing conditions. In the in situ polymerised 20/20 GNP systems the best overall mechanical properties were obtained using the lowest loading applied, 0.5 GNP wt. For example, in tensile tests although addition of 0.5 GNP wt. % did not give the best tensile modulus, it gave the best tensile strength, yield stress and elongation at break. Tensile data also indicated that the dispersed states of the carbon fillers achieved using the 100/6 processing conditions are superior to that obtained using the 200/3 processing conditions. For example, tensile strength (TS) values increased above unfilled PA6 in the NP 100/6 system, where all the average TS values of the composites are higher than that of the unfilled PA6. In addition, in the G-based systems, it was only with the 100/6 processing condition that some TS values higher than the unfilled PA6 were obtained. Overall, despite the advantages in size scale of the GNP over G, the GNP nanocomposites did not consistently exhibit better properties since the growth in property values either increased slowly or fluctuated with GNP loading. In terms of electrical conductivity, with the exception of the GL system, where electrical conductivity sufficient for electrostatic applications was attained at 15 G wt. %, all other melt processed composites of both the G and GNP remained as electrical insulators with up to 50 G wt. % loading and 25 GNP wt. % loading in both the 200/3 and 100/6 processing conditions. For the in situ polymerised composites, however, electrical conductivity percolation thresholds values of <10 wt. % were measured in both the G and GNP composites, although GNP did not show a clear advantage over G despite the difference in their order size-scale.

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Universidade Federal de Sao Carlos
For some applications toughening of polyamide is important. This can be accomplished through the addition of an elastomeric phase to the polyamide matrix with the drawback of a reduction in the stiffness and strength of the material. Several studies lately have focused on the modification of polyamide matrix with the purpose of obtaining a balance between toughness and stiffness for these thermoplastics. In this work, to achieve a balance between stiffness and toughness, ternary nanocomposites based on blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene (ABS) were prepared by the melt blending processes using the organoclay Cloisite® 30B (OMMT) and the styrene-maleic anhydride copolymer (SMA) as compatibilizer. Four blending sequences were used to prepare the selected systems and their mechanical properties studied through the Young s modulus and notched Izod impact properties. The addition of organoclay increases the Young s modulus of all ternary nanocomposites when compared to the blend and the PA6 matrix. This fact was attributed to preferential location of the clay in the PA6 matrix phase. The micrographs obtained by transmission electronic microscopy (TEM) indicate that the nanoclay shows an exfoliated structure and reside in the PA6 matrix phase, as well as in the interface between the phases. PA6/ABS/OMMT ternary nanocomposites with different content of nanoclay (1, 3 and 5%) were studied and it was observed that the particles size of ABS dispersed phase decrease with the increase of the OMMT content in the blend. This fact indicates that nanoclay can play an important role to prevent the coalescence in the ABS domains during the melt state processes. PA6/ABS ternary blends compatibilized with SMA were prepared by melt state process and it was observed that the mechanical properties and the morphology were influenced by the blending sequence of the components.
A tenacificação da poliamida 6 é desejável para diversas aplicações e pode ser obtida através da adição de uma fase elastomérica à matriz, entretanto, isto leva a uma perda em suas características de rigidez e resistência a tração. Com o intuito de se obter um balanço entre as propriedades de rigidez e tenacidade, nanocompósitos baseados em blendas de poliamida 6 (PA6) e terpolímero acrilonitrila-butadieno-estireno (ABS) foram preparados pelo método de mistura no estado fundido utilizando a argila organofílica Cloisite® 30B (OMMT) como reforço e o copolímero estirenoanidrido maleico (SMA) como compatibilizante. Os sistemas foram preparados em uma extrusora de rosca dupla co-rotacional, utilizando quatro sequências de misturas e suas propriedades mecânicas foram analisadas através da determinação do módulo de elasticidade sob tração e resistência ao impacto Izod. A adição da argila organofílica aumentou o módulo de todos os nanocompósitos ternários em relação à blenda e à matriz PA6. Mas por outro lado, foi observada uma redução da resistência ao impacto desses nanocompósitos. Este aumento na rigidez foi atribuído à localização da argila no interior da fase matriz PA6. As micrografias obtidas por microscopia eletrônica de transmissão (MET) indicaram que a argila apresenta uma estrutura esfoliada em todos os sistemas e reside na fase matriz PA6, bem como na interface entre as duas fases. Sistemas ternários de PA6/ABS/OMMT com diferentes teores de argila (1, 3 e 5%) também foram estudados e foi observado que o tamanho das partículas da fase dispersa ABS diminui com o aumento da quantidade de OMMT na blenda. Isto indica que a argila pode desempenhar um importante efeito em prevenir a coalescência dos domínios de ABS durante a mistura do fundido, estabilizando a estrutura formada. Blendas ternárias de PA6/ABS compatibilizadas com o SMA foram preparadas e foi observado que as propriedades mecânicas e a morfologia são bastante influenciadas pela ordem de mistura dos componentes da blenda.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Nanocomposites based on polyamide 6 (PA6) and acrylonitrile-butadienestyrene (ABS) blends compatibilized with styrene-maleic anhydride-acrylonitrile (SANMA) and methyl methacrylate-maleic anhydride (MA-MMA) were prepared by melt blending in a twin screw extruder through different mixing protocols. The nanoclay incorporation effect, different compatibilizing systems and components mixing sequence were evaluated in morphological, mechanical, thermal, thermomechanical and rheological properties. Evidences of chemical interactions between PA6 and reactive copolymers were observed by torque rheometry. XRD analysis indicates an exfoliated structure for all the nanocomposites due to the good interaction between PA6/OMMT. The significant increase in nanocomposites viscosity when compared with their respective ternary blends corroborates the results obtained by XRD. TEM micrographs show a strong influence of both reactive copolymers on polymer blends morphology, where the presence of SANMA and MMA-MA is responsible for reducing the dispersed phase particle size when compared to the uncompatibilized blend. TEM images confirm the existence of an exfoliation structure in all nanocomposites. The addition of both reactive copolymers significantly increased the ternary blends toughness when compared with PA6/ABS. Furthermore, the nanoclay incorporation enhanced the elasticity modulus and HDT of the nanocomposites but also reduced the toughness and the elongation at break when compared with their respective compatibilized blends.
Nanocompósitos baseados em blendas de poliamida 6 (PA6) e acrilonitrila-butadieno-estireno (ABS) compatibilizadas com os estirenoacrilonitrila- anidrido maleico (SANMA) e metacrilato de metila-anidrido maleico (MMA-MA), foram preparadas por mistura no estado fundido em uma extrusora de rosca dupla corotacional através de diferentes sequências de mistura. Foram analisadas a influência da incorporação das nanopartículas lamelares de argila, dos diferentes agentes de compatibilização e da sequência de mistura dos componentes na morfologia, propriedades mecânicas, térmicas, termomecânicas e reológicas dos materiais. Evidencias de reações químicas entre a PA6 e os copolímeros reativos foram observadas por reometria de torque. Ensaios de DRX fornecem indícios da formação de estrutura esfoliada para todos os nanocompósitos decorrente da boa interação entre PA6/OMMT. O significativo aumento da viscosidade dos nancompósitos quando comparados com suas respectivas blendas ternárias corroboram os resultados obtidos por DRX. As micrografias de MET evidenciam a forte influencia da incorporação de ambos os copolímeros reativos na morfologia das blendas poliméricas onde a presença, tanto do SANMA quanto do MMA-MA, é responsável pela redução do tamanho de partícula da fase dispersa quando comparadas com a blenda não compatibilizada. Adicionalmente as imagens obtidas por MET reafirmam o alto grau de esfoliação da argila em todos os nanocompósitos estudados. Além de refinar a morfologia, a adição de ambos os copolímeros reativos aumentou significativamente a tenacidade das blendas ternárias em relação à blenda PA6/ABS. Por fim, a incorporação de nanoargila foi responsável pelo incremento no módulo de elasticidade e HDT dos nanocompósitos, resultado esse acompanhado pela redução da tenacidade e da deformação na ruptura quando comparados com suas respectivas blendas compatibilizadas.

Materiais poliméricos que possuam boas propriedades mecânicas aliadas à flexibilidade são requisitos para atender novas necessidades da indústria. Tais necessidades podem ser atingidas com a produção de elastômeros termoplásticos vulcanizados/reticulados dinamicamente (TPVs). Os TPVs são produzidos normalmente a partir de misturas imiscíveis entre polímeros. Neste trabalho, foi avaliada a produção de TPVs a partir da poliamida 6-12 (PA6-12) e o copolímero randômico de etileno e acetato de vinila (EVA) utilizando peróxido de dicumila (DCP) como agente reticulante (1, 4 e 8 phr na fase elastomérica) preparadas em misturador fechado. As misturas foram processadas utilizando a proporção mássica de PA6-12/EVA de 50/50 em reômetro de torque (120 rpm, 15 min e 200ºC). A adição de maiores quantidades de DCP nas amostras de PA6-12/EVA resultou no aumento de torque estabilizado, e taxa de aumento de torque em virtude da formação de ligações cruzadas, com teor de gel 2,6 a 17%. A mistura de PA 6-12/EVA 50/50 possui ~99% de fases interconectadas. Em menores proporções de EVA há formação de morfologia de fases dispersas com tamanhos de 0,64 a 1,57μm. Para o sistema reticulado dinamicamente, a morfologia mostrou ser dependente da adição de DCP, devido à redução da mobilidade da fase EVA. Este sistema possui uma morfologia com contornos bem definidos e uma espessura interfacial entre 7,3-7,7 nm. A ação das forças mecânicas durante o processamento resultou na fragmentação parcial da fase EVA. A imiscibilidade do sistema foi constatada através de análises de DMTA pela presença de duas transições vítreas, correspondentes aos polímeros puros e também por meio da variação de tensão interfacial do sistema, com valor de 4,62 mN/m. Quanto à cristalinidade, não há praticamente alteração neste índice, entretanto foi notado um aumento no período longo lamelar (Lp) que esta relacionado com o incremento de fração amorfa do sistema. Isso ocorrem em virtude das cadeias de EVA estarem localizadas junto com porção amorfa da PA 6-12 devido à presença de interações secundárias entre os grupos acetato e amida. A reticulação dinâmica do sistema PA6-12/EVA aumentou a dureza do sistema, no entanto não foi capaz de promover aumentos em propriedades mecânicas, assim como melhorias na recuperação elástica em virtude da formação de uma morfologia de fases com fragmentação parcial do EVA.
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Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul
Polymeric materials having good mechanical properties combined with flexibility are requirements to meet changing needs of the industry. These requirements can be met with the production of dynamically vulcanized/crosslinked elastomers (TPVs). TPVs are generally produced from blends between immiscible polymers. In this study, was evaluated the production of TPVs from polyamide 6-12 (PA-612) and random copolymer of ethylene and vinyl acetate (EVA) using dicumyl peroxide (DCP) as crosslinking agent (1, 4 and 8 phr in relation to the elastomeric phase) prepared in a batch mixer. The polymer blends were processed using the PA6-12/EVA 50/50 wt. %/wt.% in a torque rheometer (120 rpm, 15 min and 200 °C). The addition of higher DCP contents in the blends results in increase of the stabilized torque values, torque rate due to the crosslink formation, which results in a gel contents from 2,6 to 17 wt.%. The blend PA 6-12/EVA 50/50 has ~99% of interconnected phase, for the blends with in smaller EVA contents are formed disperse phase morphology with sizes from 0.64 to 1.57 μm. For the polymers systems dynamically crosslinked, the morphology was dependent on DCP addition, due to reduced mobility of the EVA phase. This system has morphology with well-defined contours and an interfacial thickness of 7.3-7.6 nm. The mechanical forces action during melt processing resulted in partial fragmentation of the EVA phase. The PA6-12/EVA blends are immiscible, since the DMTA experiments two glass transitions were observed, characteristics of each pure polymer, and also by the interfacial tension value of the system (4.62 mN/m). The crystallinity index remains constant for blends, however, an increase was observed in the lamellar long period (Lp), this effect associated with the increase of the amorphous fraction of the system. This occurs because the EVA chains being located adjacent to the amorphous portion of PA 6-12 due to the presence of secondary interactions between amide and acetate groups. The dynamic crosslinking of the PA612/EVA system, results in increases of the stiffness, on the other hand not able to promote increases in mechanical properties as well as improvement in elastic recovery due to the formation of phase morphology with partial fragmentation of the EVA.

Cette thèse porte sur le rotomoulage réactif de polyamide 6. Ce procédé a la particularité de présenter des cycles thermiques relativement réduit et de fabriquer des polymères sur mesure contrairement à son homologue conventionnelle. La voie envisagée pour la synthèse in situ de PA6 est la polymérisation anionique de l’ε-caprolactame par ouverture de cycle. Le Caprolactamate de sodium et le bromure de caprolactame-magnésium ont été utilisés comme catalyseurs, et l’hexaméthylène dicarbamoyl dicaprolactame a été employé comme activateur. L’étude rhéocinétique de deux systèmes réactifs lactames qui ont été utilisé à différentes compositions et températures a permis de déterminer une formulation appropriée aux exigences du procédé (faible viscosité initiale du système réactif, temps de polymérisation court...). La simultanéité des phénomènes de polymérisation et de cristallisation aux faibles températures à été observé à l’aide des résultats du suivi cinétique par DSC. La mise en forme par la technique de rotomoulage a été réalisée sur une installation pilote de rotomoulage associée à un système d’acquisition de température par télémesure radio. La comparaison des propriétés des articles en PA 6 obtenus par voie réactive par rapport a ceux obtenus par voie fondue, a montré un gain au niveau du temps de cycle et une amélioration des propriétés mécaniques du matériau notamment dans le domaine des faibles déformations. Le rotomoulage de la bicouche PA6/PE-GMA a été ainsi étudié, le contrôle des mécanismes réactionnels mis en jeu à l’interface par rhéologie, durant la formation de la couche de polymère PA6 par voie anionique sur une couche de PE-GMA a été effectué dans un rhéomètre, une bonne adhésion à l’interface a été observé. La faisabilité d’élaboration de nanocomposite PA 6/argile par le procède de rotomoulage réactif a été testé, les caractérisations physico-chimiques et les observations morphologiques ont été étudiés afin d’évaluer l’état de dispersion et la nature des interactions. Durant cette étude, nous avons mesurés la faisabilité de l’intercalation et le gonflement de l’argile dans le monomère ε- caprolactame et estimer la possibilité d’avoir une morphologie exfolié des nanocomposites élaborés par le procédé de rotomoulage réactif
A reactive rotational molding (RRM) process was developed to obtain a PA6 by activated anionic ring-opening polymerization of epsilon-caprolactam (APA6). Sodium caprolactamate (C10) and caprolactam magnesium bromide (C1) were employed as catalysts, and difunctional hexamethylene-1,6-dicarbamoylcaprolactam (C20) was used as an activator. The kinetics of the anionic polymerization of ε-caprolactam into polyamide 6 was monitored through dynamic rheology and differential scanning calorimetry measurements. The effect of the processing parameters, such as the polymerization temperature, different catalyst/activator combinations and concentrations, on the kinetics of polymerization is discussed. A temperature of 150°C was demonstrated to be the most appropriate. It was also found that crystallization may occur during PA6 polymerization and that the combination C1/C20 was well suited as it permitted a suitable induction time. Isoviscosity curves were drawn in order to determine the available processing window for RRM. The properties of the obtained APA6 were compared with those of a conventionally rotomolded PA6. Results pointed at lower cycle times and increased tensile properties at weak deformation. Additionally, rotational molding of the bilayer PA6/PE-GMA has been studied, the control of the reactions mechanisms involved in the interface by rheology , during formation of the anionically PA6 polymer layer on a PE- GMA layer was carried out in a rheometer , a good adhesion at the interface was observed. The feasibility of developing nanocomposite PA 6/clay by reactive rotational molding process has been tested; the physico-chemical characterization and morphological observations were studied to assess the state of dispersion and the nature of interactions. During this study, we measured the feasibility of intercalation and swelling the clay in the ε-caprolactam monomer and estimate the possibility of having morphology of exfoliated nanocomposites prepared by reactive rotational molding process

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Universidade Federal de Sao Carlos
Toughened polyamide 6 (PA6) nanocomposites were obtained by incorporation of acrylonitrile-EPDM-styrene (AES). As compatibilizing agents was used the copolymer methyl methacrylate-anhydride (MMA-MA). The effect of the blending protocol of the components and of the addition of three montmorillonites (Cloisite®30B, Cloisite®20A and Cloisite®Na+) was investigated. The nanocomposites were prepared in a twin screw extruder and then its microstructure, lamellar structure, mechanical, thermal and rheological properties were characterized. The morphology and properties of the nanocomposites were significantly affected by different nanoclays and blending protocol. The characterizations by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and wide angle X-ray difraction (WAXD) indicated intercalated structures for the nanocomposites with Cloisite®20A and Cloisite®Na+, in contrast to the ones prepared with Cloisite®30B that exhibited exfoliated structure. The addition of nanoclays in the blends increased the modulus for all nanocomposites with respect to the pure blend. Excellent impact strength results were obtained for the nanocomposites compatibilized with MMA-MA with respect to the blend PA6/AES and ternary systems ternary (PA6/AES/clay), demonstrating the effective presence of the copolymer as a compatibilizer of these systems. It was observed a good correlation between mechanical properties and morphology. An increase in rigidity is accompanied by a corresponding increase in toughness when the clay is present in both phases. A significant increase in long period of nanocomposites compared to the PA6 was observed through SAXS results. In this work, polymer blends compatibilized with MMA-MA were also prepared and a significant increases in the mechanical behavior these materials was observed.
Nanocompósitos poliméricos de poliamida 6 (PA6) tenacificados foram obtidos através da incorporação de acrilonitrila-EPDM-estireno (AES). O copolímero acrílico metacrilato de metila-anidrido maleico (MMA-MA) foi utilizado como agente de compatibilização para este sistema. O efeito da ordem de mistura dos componentes e da adição de três argilas montmorilonitas (Cloisite®30B, Cloisite®20A e Cloisite®Na+) foi investigado. Os nanocompósitos foram preparados em uma extrusora de rosca dupla corotacional e caracterizados por microscopia eletrônica de transmissão (MET), difração de raios-X de baixo ângulo (SAXS) e alto ângulo (WAXD), ensaios mecânicos, térmicos e reológicos. A morfologia e propriedades dos nanocompósitos foram significativamente afetadas pelas diferentes nanoargilas e sequências de mistura. As caracterizações por MET, WAXD e SAXS indicaram a presença de estrutura intercalada para os nanocompósitos com Cloisite®20A e Cloisite®Na+, em contraste com aqueles preparados com Cloisite®30B que apresentaram estrutura esfoliada. A adição das nanoargilas à blenda aumentou o módulo de elasticidade destes materiais. Excelentes resultados de resistência ao impacto foram obtidos para os nanocompósitos compatibilizados com o MMA-MA (sistemas PA6/AES/argila/MMA-MA) em relação à blenda PA6/AES e aos sistemas ternários PA6/AES/argila, evidenciando a presença efetiva do copolímero como agente de compatibilização destes sistemas. Foi possível obter um aumento na rigidez nas misturas com Cloisite®20A, acompanhado de um correspondente aumento na tenacidade quando a argila está presente em ambas as fases. Um aumento bastante significativo nos valores de período longo dos nanocompósitos em relação à PA6 foi observado através dos resultados de SAXS obtidos em diferentes temperaturas. Blendas poliméricas de PA6/AES compatibilizadas com MMA-MA também foram preparadas e foram verificados aumentos significativos nas propriedades mecânicas destes materiais em relação à blenda pura sem agente compatibilizante.

Em virtude do crescente volume da utilização de embalagens multicamadas na preservação de alimentos, torna-se necessário o estudo visando a reciclagem desses materiais através de seu reaproveitamento como matéria-prima e a transformação em novos produtos ou materiais. Dentre os vários tipos de reciclagem utilizados atualmente, a formação de blendas poliméricas com material descartado apresenta-se como uma alternativa viável, pois se trata de uma atividade moderna que une o desenvolvimento tecnológico e a preservação ambiental. O presente trabalho faz um estudo sobre a reciclagem de resíduos de embalagens multicamadas pós-consumo no setor alimentício para a formação de uma blenda. O filme multicamada composto por poliamida 6 e polietileno de baixa densidade foi previamente moído para obtenção de flocos e a ele foi adicionado primeiramente o aditivo etileno-propileno-dieno monômero e em seguida foi feito uma nova mistura composta apenas de anidrido maléico com filme multicamada na forma de flocos, no intuito de melhorar as propriedades mecânicas das blendas formadas pelo processo da extrusão. Para a verificação dos resultados obtidos foram realizados testes de tração, alongamento e permeabilidade ao gás oxigênio no filme de poliamida 6 e polietileno, e ensaios mecânicos, análises térmicas e microscopia eletrônica de varredura nas blendas obtidas. Também se estudou o efeito da radiação (100 kGy) sobre as propriedades das blendas utilizando-se um acelerador de elétrons.
In virtue of the increasing volume of the multilayers packings use in the food preservation, the study for the recycling of these materials through its reverse speed-exploitation as raw material and the transformation in new products or materials becomes necessary. Amongst some types of recycling used currently, the polymers blendes formation with discarded material is presented as a viable alternative, therefore if it deals with a modern activity that joins the technological development and the ambient preservation. The present research, therefore makes a study on the recycling of residues from multilayers packings after-consumes in the nourishing sector for the blend formation. The multilayer film composed by polyamide 6 and polyethylene of low density was previously worn out for flake attainment and it was added first the Ethylene-Propylene-Diene-Monomer (EPDM) additive and after that a new composed maleic anhydride mixture was made only with multilayer film in the flake form, in intention to improve the mechanical properties of blendes formed for the process of the drawing. For verification of the results assays had been carried through traction tests, rupture lengthening tests and permeability to the gas oxygen in the film of polyamide 6 and mechanical properties of blendes formed for the process of the drawing. For verification of the results assays had been carried through traction tests, rupture lengthening tests and permeability to the gas oxygen in the film of polyamide 6 and mechanical polyethylene, and assays, thermal analyses and scanning electronic microscopy in the blendes. It was also studied radiation dose (100 kGy) on the blends properties using an electron beam accelerator.

Computational Fluid Dynamics (CFD) codes are being increasingly used in the field of fire safety engineering. They provide, amongst other things, velocity, species and heat flux distributions throughout the computational domain. The various sub-models associated with these have been developed sufficiently to reduce the errors below 10%-15%, and work continues on reducing these errors yet further. However, the uncertainties introduced by using material properties as an input for these models are considerably larger than those from the other sub-models, yet little work is being done to improve these. Most of the data for these material properties comes from traditional (standard) tests. It is known that these properties are not intrinsic, but are test-specific. Thus, it can be expected that the errors incurred when using these in computations can be significant. Research has been held back by a lack of understanding of the basic factors that determine material flammability. The term “flammability” is currently used to encompass a number of definitions and “properties” that are linked to standardised test methodologies. In almost all cases, the quantitative manifestations of “flammability” are a combination of material properties and environmental conditions associated with the particular test method from which they were derived but are not always representative of parameters linked intrinsically with the tested material. The result is that even the best-defined parameters associated with flammability cannot be successfully introduced into fire models to predict ignition or fire growth. The aim of this work is to develop a new approach to the interpretation of standard flammability tests in order to derive the (intrinsic) material properties; specifically, those properties controlling ignition. This approach combines solid phase and gas modelling together with standard tests using computational fluid dynamics (CFD), mass fraction of flammable gases and lean flammability limits (LFL). The back boundary condition is also better defined by introducing a heat sink with a high thermal conductivity and a temperature dependant convective heat transfer coefficient. The intrinsic material properties can then be used to rank materials based on their susceptibility to ignition and, furthermore, can be used as input data for fire models. Experiments in a standard test apparatus (FPA) were performed and the resulting data fitted to a complex pyrolysis model to estimate the (intrinsic) material properties. With these properties, it should be possible to model the heating process, pyrolysis, ignition and related material behaviour for any adequately defined heating scenario. This was achieved, within bounds, during validation of the approach in the Cone Calorimeter and under ramped heating conditions in the Fire Propagation Apparatus (FPA). This work demonstrates that standard flammability and material tests have been proven inadequate for the purpose of obtaining the “intrinsic” material properties required for pyrolysis models. A significant step has been made towards the development of a technique to obtain these material properties using test apparatuses, and to predict ignition of the tested materials under any heating scenario. This work has successfully demonstrated the ability to predict the driving force (in-depth temperature distribution) in the ignition process. The results obtained are very promising and serve to demonstrate the feasibility of the methodology. The essential outcomes are the “lessons learnt”, which themselves are of great importance to the understanding and further development of this technique. One of these lessons is that complex modelling in conjunction with current standard flammability test cannot currently provide all required parameters. The uncertainty of the results is significantly reduced when using independently determined parameters in the model. The intrinsic values of the material properties depend significantly on the accuracy of the model and precision of the data.

Ce travail revisite la problématique des transitions de phases cristallines induites thermiquement et mécaniquement dans les polymères semi-cristallins à liaisons fortes. Ce point revêt une importance primordiale dans des matériaux où l'anisotropie de liaisons intermoléculaires (van der Waals vs hydrogène) conduit à l'existence de phases cristallines présentant une structure en feuillets des liaisons hydrogène. L'originalité principale réside dans le recours à l'expérimentation in situ pour le suivi de l'évolution structurale de ces matériaux polymorphes par diffraction et diffusion des rayons X sous rayonnement synchrotron. L'étude concerne les polyamides 11 et 6 et une attention particulière est portée à l'influence de ces transitions sur le comportement mécanique sous sollicitations uniaxiale et biaxiale. La caractérisation structurale confirme l'existence d'une transition de phase, la transition de Brill, vers une phase HT de symétrie hexagonale dans le cas de certaines structures cristallines (Alpha' et Delta' du PA11, Alpha défectueuse et Beta du PA6). Les formes stables (Alpha' du PA11 et Alpha du PA6) se reforment au refroidissement. Sous sollicitation uniaxiale, les polyamides se révèlent ductiles, quelle que soit la forme cristalline; une transformation ordre vers désordre intervient à T
This work revisits the problem of thermally and mechanically-induced crystal phase transitions in semi-crystalline polymers bearing H bonds. This point is of prime importance in materials where anisotropic intermolecular interactions (van der Waals vs H-bonding) gives rise to the existence of crystal phases with sheet-like H-bonded structures. The main originality of the present study lies in the use of in situ characterization of these polymorphic materials by wide angle and small angle X Ray scattering from a synchrotron source. Materials under concern are polyamides 11 and 6, and specific attention is paid to the role of these transitions on the mechanical behavior under uniaxial and biaxial drawing. The structural characterization confirms the existence of a phase transition, the Brill transition, towards a HT phase with hexagonal symmetry for some specific crystal structures (Alpha' and Delta' in PA11, Alpha defective and Beta in PA6). The most stable forms (Alpha' in PA11 and Alpha in PA6) rebuild upon cooling. Under uniaxial drawing, polyamides exhibit ductility, whatever the original crystal form is; an order towards disorder transition occurs for T

Cette étude s’intéresse aux procédés d’ignifugation de deux thermoplastiques techniques, le poly téréphtalate de butylène (PBT) et le polyamide 6 (PA6), à application dans le domaine électrique et électrotechnique. Plus précisément, l’accent est mis sur l’ajout en masse de retardateurs de flammes à base d’azote et de phosphore. L’objectif de ce projet consiste à préparer de nouveaux retardateurs de flamme par voie de synthèse organique. Dans un premier temps, cinq phosphinates d’aluminium ont été préparés par amidification de l’acide hydroxyphenylphosphoryl propanoïque et réaction avec un promoteur d’aluminium. Ces sels ont été incorporés au PBT et au PA6, seuls ou en combinaison avec des co-additifs, puis testés à l’UL-94, test témoin de la propagation verticale de la flamme, très utilisé dans l’industrie électrique et électrotechnique. Parmi les cinq sels, seul le phenylamide de l’acide hydroxyphenylphosphoryl propanoïque (PAS) s’est avéré être un retardateur de flammes efficace. D’autres tests ont été réalisés pour approfondir les résultats. Une instrumentation du test UL-94 a également été développée pour établir les bases de la compréhension du mécanisme d’action de la formulation, approfondies ensuite dans une série de microanalyses. Il a été démontré que le PAS se décompose en entraînant la scission des chaînes de PBT et le refroidissement du matériau. La libération de composés phosphorés en phase gaz, bien que moins efficace que pour d’autres composés commerciaux, suffit à donner à la formulation sa propriété d’auto-extinction
This study deals with the flame retardancy of two engineering plastics, the poly(butylene terephthalate) (PBT) and the polyamide 6 (PA6), widely used in the electrical and electronic equipment (EEE). The focus is made on the incorporation of phosphorus- and nitrogen-containing flame retardant (FR) additives. The main goal of this project was to prepare novel FR through organic synthesis. Five aluminum phosphinates were prepared by reaction of amines on hydroxyphenylphosphnyl propanoic acid and an aluminum promoter. The salts were incorporated to PBT and PA6, with or without co-additives, and the materials were tested in the UL-94, test investigating the vertical propagation of the flame and widely used in the EEE industry. Among the five salts, only the aluminum salt of phenyl amide of hydroxyphenylphosphnyl propanoic acid showed outstanding properties as FR. Other tests were carried out, among which an instrumentation of the UL-94 test, to build a way to the comprehension of mechanisms. First observations were completed by various microanalyses. It has been shown that the decomposition of PAS enhances that of PBT in parallel to its cooling. The liberation of phosphorus-containing species in the gas-phase, despite les efficient than in the case of other commercial FR, gives the formulation its auto-extinguishing character

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The structure and morphology of polymers and consequently their properties are dependent on the processing conditions. During the blown film process, high shear and elongational flows can induce a preferred orientation of the polymer chains; controlling the process conditions, it is possible to obtain films with anisotropic properties. Polymeric nanocomposites have attracted industrial and scientific interest due the possibility of obtaining materials with improved thermal, mechanical, and permeation properties by the addition of small contents of inorganic fillers. This dispersed phase can also be affected by the processing conditions and also develop a preferred orientation, and influence the three-dimensional structure of the composite and its properties. In this work, the influence of the nanoparticle s (NPs) shape and processing conditions on the structure (with emphasis on the orientation characteristics) of polyamide 6 (PA6) nanocomposites blown films was evaluated, by the incorporation of an one-dimensional NP (halloysite HNT, with a hollow tubular structure) and a two-dimensional NP (montmorillonite MMT, with lamellar structure) to the polymeric matrix. Using a constant NP content (fixed above the theoretical percolation threshold) and evaluating the presence or absence of the NP s superficial treatment, blown films were obtained in four different processing conditions, varying the take-up and blow-up ratios (TUR and BUR, respectively) and using a fixed mass flow. Unexpectedly, all the films exhibited a preferred orientation of the crystalline lamellae along the normal direction, i.e., along the film thickness, independently of the processing conditions. This behavior was explained by the cooling conditions and initial preferred orientation of the polymer chains in the annular die exit. On the other hand, the NPs presented a preferred orientation along the flow direction and were well distributed and dispersed through the matrix. The film s thermal dynamicviii mechanic, tensile, permeation and optical behaviors were consistent with the structure observed and significant improvements of these properties were achieved for the films of organically treated HNT and MMT PA6 nanocomposites. Regarding the NP s shape, greater aspect ratio and surface area, in the presence of good interfacial interactions, promoted a greater efficiency of reinforcement.
A estruturação e morfologia de materiais poliméricos e, consequentemente suas propriedades, são dependentes do tipo de processamento. Na obtenção de filmes tubulares, o polímero é conformado sob altas taxas de deformação em fluxos cisalhantes e elongacionais, gerando uma orientação preferencial das cadeias poliméricas, podendo-se controlar a anisotropia de propriedades através das condições de processamento. Nanocompósitos poliméricos vem despertando grande interesse industrial e cientifico pela possibilidade de se obter materiais com propriedades térmicas, mecânicas e de permeação superiores, através da adição de pequenas quantidades de cargas inorgânicas. Essa fase dispersa também pode ser afetada pelas condições de processamento e também desenvolver uma orientação preferencial, influenciando na estruturação tridimensional do compósito e em suas propriedades. Nesse trabalho avaliou-se a influencia da geometria da nanocarga e das condições de processamento na estruturação (com ênfase nas características de orientação) de filmes tubulares de nanocompósitos de poliamida 6, incorporando-se uma nanocarga unidimensional (haloisita - HNT, com formato tubular oco) e uma bidimensional (montmorilonita - MMT, com formato lamelar) à matriz polimérica. Utilizando-se um teor de nanocarga fixo, acima do limite de percolação teórico, e avaliandose a influencia da presença ou não de tratamento superficial de organofilização, foram obtidos filmes tubulares em quatro diferentes condições de processamento, variando-se as razões de estiramento e sopro, a uma vazão constante. Inesperadamente, os filmes apresentaram uma orientação preferencial das lamelas cristalinas ao longo da direção normal, ou seja, da espessura do filme, independentemente da condição de processamento. Esse resultado foi explicado pelas condições de resfriamento e orientação inicial das cadeias poliméricas na saída da matriz anelar. As nanocargas, por sua vez, se orientaram na direção do fluxo e apresentaram uma boa dispersão e distribuição pela matriz. Os comportamentos térmico dinâmico-mecânico, mecânico sob tração, de permeabilidade e ótico dos filmes foram coerentes vi com essa estruturação, verificando-se melhorias significativas de desempenho para os filmes de nanocompósitos de HNT e MMT tratados organicamente. Com relação à geometria da nanocarga, maiores razão de aspecto e área superficial, na presença de boas interações interfaciais, promoveram uma maior eficiência de reforço.

A reciclagem de resíduos sólidos tem se tornado cada vez mais relevante devido a alguns fatores como os impactos ambientais ocasionados com o seu descarte inadequado, ao rigor crescente de legislação específica e ao custo elevado para o gerenciamento apropriado destes resíduos. Na área de materiais poliméricos, os resíduos poliméricos podem ser de origem pósconsumo ou pós-industrial. Alguns rejeitos industriais poliméricos possuem características estruturais ou químicas que impossibilitam o seu reaproveitamento direto no processo que o gerou, como é o caso filmes multicamadas de polietileno de baixa densidade (PEBD) com poliamida 6 (PA6), usados para a produção de embalagens. O presente trabalho teve como objetivo central o reaproveitamento de rejeitos de filmes multicamadas de PEBD com PA6 na forma de blendas recicladas destes polímeros, fazendo uso de agente compatibilizante e variação na composição das blendas com a incorporação de PA6 virgem, a fim de produzir materiais com propriedades adequadas e custo compatível para a aplicação comercial. O desenvolvimento experimental foi dividido em três etapas que consistiram na avaliação do teor mais adequado de agente compatibilizante de fases da blenda (etapa 1), na determinação do comportamento das propriedades das blendas não compatibilizadas em diferentes composições de rejeito do filme multicamada e PA6 virgem (etapa 2) e na associação do uso de compatibilizante com variação das composições das blendas (etapa 3). A partir da execução experimental das atividades das etapas 1 e 2 do trabalho foi possível determinar que o teor de 2,5% do agente compatibilizante polietileno grafitizado com anidrido maleico (PEg- AM) é o mais adequado para compatibilizar as blendas poliméricas e que a maioria das suas propriedades das blendas apresentam um comportamento próximo ao aditivo linear, que leva em consideração somente as propriedades iniciais dos componentes poliméricos PEBD e PA6 isolados. Os diversos materiais gerados no desenvolvimento desta pesquisa apresentam desempenho de propriedades e custo de produção variáveis em função do teor de PA6 nas blendas, que podem viabilizar o uso deste material reciclado em aplicações comerciais específicas.
Recycling of solid waste has been an important issue due to some factors such as environmental damage caused by inappropriate discards, increasing rigor of specific legislation and high cost to the appropriate management of these waste. Polymeric waste can be originated from post-consume or post-industrial sources. Some polymeric waste have chemical or structural characteristics that difficult their direct reuse in the same productive process such as multilayer film of low density polyethylene (LDPE) and polyamide 6 (PA6), which are used for packing. The aim of this work has been the study the mechanical recycling of multilayer films of PEBD and PA6 as PEBD/PA6 blends with adequate properties and compatible cost for commercial applications. The experimental development has been performed in 3 steps, which correspond to evaluation of more adequate content of compatibilizer agent for interface of blends (step 1), determination of behavior of the properties of blends without compatibilizer agent on different compositions of waste form multilayer films (step 2) and production of blends with compatibilizer agent graphitized polyethylene with maleic anhydride (PE-g-MA) (step 3). Has been verified that the content of 2.5% of PE-g-MA is more adequate to be used in the compatibilization of recycled PEBD/PA blends and that the performance of the blends dependents of the content of PA6 in the material. The recycled materials have potential for commercial applications.

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Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul.

Nous avons étudié le renforcement par des copolymères diblocs formés in situ d'interfaces entre le polyamide 6 et des polypropylènes, polymères qui sont tous semi cristallins. De nombreux paramètres peuvent jouer un rôle dans l'adhésion de ces interfaces : quantité de copolymères formés , microstructure de ceux-ci, conditions de recuit, cristallinité. . . Des études récentes ont montré que ces systèmes se comportent en général de façon analogue aux interfaces entre polymères vitreux, mais certains effets liés à la cristallinité ne sont pas encore bien compris. Le but de ce travail est de répondre aux questions en supens quant aux mécanismes impliqués dans l'adhésion de ces systèmes. Nous avons déterminé l'orientation cristalline des interfaces et montré l'existence de relations d'épitaxie entre les couples iPP/PA6 et sPP/PA6. Ces orientations préférentielles sont toujours observées mais le degré d'épitaxie est sensible aux conditions de fabrication des assemblages, en partciulier la température de recuit. Nous avons caractérisé le renforcement des interfaces en mesurant l'énergie d'adhésion et la densité de copolymères formés à l'interface des systèmes PP/copolymère/PA6, en variant les conditins de rcuit et la microstructure des copolymères. La corrélation de ces données permet de tirer plusieurs conclusions quant aux mécanismes de renforcement des interfaces PP/PA6. Le renforcement de l'interface est d'autant plus rapide et efficace que les microstructures des copolymères et des matrices sont proches. Le modèle de Brown, suivi par les interfaces entre polymères amorphes, n'est pas toujours suivi par nos systèmes. En particulier, les copolymères à bloc PP longs sont plus efficaces que prévu lorsque la température de recuit est supérieure à 221°C. Nous avons relié ceci à une synergie entre la capacité des copolymères à ponter entre elles des lamelles cristallines et l'augmentation du degré d'orientation des interfaces pour ces températures de recuit.

Pesquisas e publicações sobre polímeros luminescentes vêm sendo desenvolvidas nos últimos anos devido à inovação acadêmica, porém ainda no âmbito nacional possuem aplicação industrial limitada. Marcadores ópticos processados são pouco explorados devido à dificuldade de processamento dos materiais poliméricos luminescentes com estabilidade de luminescência. Os materiais utilizados para o processamento de polipropileno luminescente foram Poliamida 6 (PA6) dopada com complexo sintetizado de [Eu(tta)3(H2O)2] obtida através do processo de diluição do polímero e técnica de derramamento. As poliolefinas, por serem inertes, não se adequam ao procedimento comum de dopagem, assim no presente trabalho, o polipropileno luminescente foi preparado indiretamente por dopagem com poliamida dopada com complexo de európio em processamento por extrusão. As técnicas de caracterização utilizadas foram a Análise Térmica (TG), Calorimetria Exploratória Diferencial (DSC), Difração de Raios-X (XRD), Espectroscopia de infravermelho (FT-IR) e estudo das propriedades fotoluminescentes. A blenda PP/PA6:Eu(tta)3 processada apresentou propriedades luminescentes observadas nas transições intraconfiguracionais de bandas finas 4f6 - 4f6 relativas aos níveis de excitação de energia 7F0 → 5L6 (394nm), 7F0 → 5D3 (415nm), 7F0 → 5D2 (464nm), 7F0 → 5D1 (525nm) e 7F0 → 5D0 (578nm). Tanto a blenda de PP/PA6:Eu(tta)3 e os filmes de PA6:Eu(tta)3 quando expostos a luz UV (365nm) apresentaram luminescência vermelha. Os resultados de TG mostraram que sob atmosfera de O2 o PP dopado PA6:Eu(tta)3 apresentou maior estabilidade do que o PP puro. Neste trabalho foi possível processar PP/PA6:Eu(tta)3 com propriedades térmicas e fotoestabilidade, que permitem sua utilização com marcador óptico em processamentos.
Research and publications about luminescent polymers have been developed in the last years for the academic innovation; however the industrial application has been very limited in this area. Processed Optical markers are few explored due to the difficult to process luminescent polymeric materials with stable luminescence. The materials used of processing luminescent polypropylene (PP) were polyamide 6 (PA6) doped with europium complex [Eu(tta)3(H2O)2] obtained through the dilution and casting process. Due to their inercy, polyolefins do not fit into the common procedure of doping, in consequence, in this work luminescent polypropylene was indirectly prepared by polyamide 6 doped with europium complex through extrusion process. Product characterization was done using Thermalgravimetry analysis (TG), Differential Scanning Calorimetric (DSC), X-Ray Diffraction (XRD), Infrared spectroscopy (FTIR) and fotoluminescence of emission and excitation. The blend PP/PA6:Eu(tta)3 presented luminescent properties, after semi-industrial process, as observed in the narrow bands of intraconfiguration transitions - 4f6 relatives to energy levels 7F0 → 5L6 (394nm), 7F0 → 5D3 (415nm), 7F0 → 5D2 (464nm), 7F0 → 5D1 (525nm) e 7F0 → 5D0 (578nm) of emission spectrum. Red light of the pellets or film is emitted when excited in UV lamp (365nm). TG results showed under O2 atmosphere that PP doped with PA6:Eu(tta)3 was more stable than pure PP. In this work luminescent PP/PA6:Eu(tta)3 was processed with properties of thermal and photo stability which can be used as optical marker in polymer processing.

Les travaux menés dans le cadre de cette thèse ont pour objectif le développement d'une approche numérique performante, basée sur la Méthode des Éléments Discrets (MED) pour simuler le comportement hygro-thermo-mécanique d'un matériau composite à fibres de verre courtes. La modélisation discrète proposée est mise en œuvre dans le cas d'un matériau composite Polyamide 6 renforcé avec 30% de fibres de verre (PA6/GF30). Tout d'abord, les propriétés mécaniques ainsi que les mécanismes d'endommagement du PA6/GF30 sont évalués expérimentalement. Ensuite, un modèle 3D par Éléments Discrets(ED), en s'appuyant sur une méthodologie originale, est développé et validé par comparaison avec des approches micromécaniques et des résultats expérimentaux,en termes de propriétés élastiques. Par ailleurs, le modèle discret mis au point est exploité afin de simuler le processus de délamination en mode I, II et mixte en utilisant un modèle de zone cohésive 3D définit selon une loi de traction-séparation bilinéaire. La décohésion interfaciale fibre/matrice sous sollicitations mécaniques, respectivement dans le cas d'un composite mono-fibre et multifibre est également étudiée. Compte tenu du caractère hydrophile du PA6, l'introduction du modèle de décohésion trouve son intérêt dans la prise en compte de l'endommagement interfacial dû à l'absorption d'eau à l'interface fibre/matrice en présence d'humidité. Par conséquent, des paramètres hygro-thermo-mécaniques sont intégrés au modèle ED afin de tenir compte du gonflement hygroscopique et de l'endommagement du PA6/GF30 dans une large gamme de conditions environnementales. Des comparaisons avec la Méthode des Éléments Finis (MEF) ont été établies afin de vérifier la validité du modèle ED proposé
This thesis work aims at developing a powerful numerical tool based on the Discrete Element Method (DEM) to simulate the hygro-thermo-mechanical behaviour of a short glass fibre composite material. The proposed discrete modelling is performed in the case of a Polyamide 6 composite material reinforced with 30% of glass fibres (PA6/GF30). First of all, mechanical properties as well as damage mechanisms of PA6/GF30 are evaluated using experimental campaign. Then, a 3D Discrete Element (DE) model based on an original methodology is developed and validated by comparison with micromechanical approaches and experimental results in terms of elastic behaviour of PA6/GF30. Furthermore, the developed discrete model is exploited to simulate delamination process on mode I, II and mixed mode using a 3D cohesive zone model with a bilinear tractionseparation law. The fibre/matrix interfacial decohesion under mechanical stress,respectively in the case of a single-fibre and multi-fibre composite is also studied. Given the hydrophilic nature of PA6, the introduction of the decohesion model is interesting in order to take into account the interfacial damage due to water absorption at the fibre/matrix interface in the presence of moisture. Therefore, hygro-thermo-mechanical parameters are integrated into the discrete model in order to take into account the hygroscopic swelling and the damage of PA6/GF30 material under a wide range of environmental conditions. Comparisons with the Finite Element Method (FEM) have been established to check out the validity of the proposed DE model

Les polymères sont utilisés dans de très nombreux secteurs d’activités tels que l’emballage, l’automobile, … car sont dotés de bonnes propriétés mécaniques, thermiques et barrières. Les enjeux économiques et environnementaux poussent le développement vers des matériaux plus performants et allégés. L’objectif de ce travail de thèse visait l’élaboration de films composites multicouches à base de polyéthylène (PE) et de polyamide (PA6) offrant de hautes propriétés barrières aux gaz et à l’eau. Un procédé de coextrusion équipé d’éléments multiplicateurs a permis de réaliser des multicouches de 100 μm d’épaisseur contenant jusqu’à 2049 couches. Deux séries de films PE-liant-PA6 de compositions différentes ont été étudiées. Des argiles (montmorillonites modifiées) ont été incorporées (à 0,5 et 5 wt%) dans les couches alternées de PE et PA6. Les propriétés structurales, thermiques, mécaniques de ces multicouches ont été corrélées aux propriétés de transport. Nous avons observé des effets de confinements sur la nanostratification des films et la cristallinité des polymères et l’impact sur les propriétés barrières. Nous avons montré la complexité des structures multinanocouches impliquant les interphases ainsi que la complexité des mécanismes de transfert. Le modèle en série de prédiction de perméabilité a mis en évidence des améliorations significatives des propriétés barrières aux gaz des couches confinées de PE mais pas à l’eau. L’effet barrière sur l’ensemble des multicouches a été toutefois limité en raison des orientations « on edge » des phases cristallines et des défauts de structure. Le confinement des nanocharges (à 1% v/v) dans les couches de PA6 a permis d’accroître les propriétés barrières des multicouches
Polymers are used in many fields such as packaging, automotive, etc. as they have good mechanical, thermal and barrier properties. Economic and environmental challenges are driving development towards more efficient and lighter materials. The aim of this thesis work was to develop multilayer composite films based on polyethylene (PE) and polyamide (PA6) with high gas and water barrier properties. A coextrusion process with multiplier elements made it possible to carry out 100 μm thick multilayers containing up to 2049 layers. Two series of PE-binder-PA6 films of different compositions were studied. Clays (organo-modified montmorillonites) were incorporated (at 0.5 and 5 wt%) into the alternating layers of PE and PA6. The structural, thermal and mechanical properties of these multilayers have been correlated with the transport properties. We observed confinement effects on nanostratification of films and crystallinity of polymers and the impact on barrier properties. We showed the complexity of the multinanolayer structures involving interphases as well as the complexity of the transfer mechanisms. The serial model for predicting permeability highlighted significant improvements in the gas barrier properties of confined PE layers but in water. The barrier effect on all of the multilayers was, however, limited due to the “on edge” orientation of the crystalline phases and structural defects. The confinement of nanofillers (at 1% v/v) in PA6 layers has made it possible to increase the barrier properties of multilayers

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas.
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Análise das propriedades micro e macroscópicas de novos materiais, obtidos a partir da mistura física de dois polímeros comerciais em presença de pequena quantidade de um terceiro polímero que atuará como agente compatibilizante e pela complexação do íon cobre (II) com o nitrogênio piridínico da poli vinil piridina. Blendas binárias e ternárias de polímeros e misturas binárias de polímero com iodeto de cobre são preparadas. Os procedimentos distintos utilizados produzem novos materiais com propriedades diferentes dos componentes puros e de interesse prático. A relação entre propriedades térmicas, mecânicas e a morfologia das blendas de poliamida 6 (PA6) e poli(2,6-dimetil-1,4-oxi fenileno) (PPE) ou PPE modificado com 20% de estireno (mPPE) ou PPE enxertado com anidrido maleico (PPE-g-AM) compatibilizado com o copolímero tribloco poli[estireno-b-(etileno-co-butileno)-b-estireno] enxertado com anidrido maleico (SEBS-g-AM) são estudados. O uso de uma combinação de SEBS-g-AM e SEBS é também usado. A adição de 1% de CuI, em massa, às blendas é também analisada. São empregadas as técnicas de MET, MEV, DSC, TGA e DMA. Propriedades mecânicas são caracterizadas por medidas de resistência ao impacto e tensão-deformação. Misturas binárias polímero/iodeto de cobre (CuI) (mol/mol) são estudados e analisados a formação de complexos polímero-cobre (II). Poli(2-vinil piridina) (P2VP) e poli(4-vinil piridina) (P4VP) são os polímeros usados. A caracterização dos complexos é realizado pelos resultados obtidos das técnicas de DSC, TGA, FTIR, EPR, Raman, MEV e condutividade elétrica.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.
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No desenvolvimento de materiais com gradiente funcional (Functionally Graded Materials - FGM), o uso do processo de sinterização seletiva a laser (SLS) oferece vantagens tais como a construção de formas livres e o controle localizado da composição e dos parâmetros de processo, em comparação aos demais processos de fabricação rápida. Estudos referentes a componentes anti-fricção (buchas, mancais, etc.) mostram que alguns destes componentes possuem melhor desempenho quando existem variações composicionais ao longo do mesmo. Visando investigar as possibilidades de aplicação de blendas com gradiente de composição fabricados por SLS em componentes anti-fricção, foram fabricados corpos de prova e peças com gradiente funcional PA12/PEAD, PA6/PA12 e PMMA/PS. Os corpos de prova foram caracterizados através de análises de espectroscopia de infravermelho, MEV, DSC, DRX, índice de fluidez e DMA. O processamento dos materiais poliméricos e das blendas por sinterização seletiva a laser mostrou-se dependente de alguns fatores: de características do material como a forma e o tamanho das partículas; da absorção da energia do laser pelo material; e do índice de fluidez nas condições de processamento. A influência do índice de fluidez sobre a processabilidade das blendas mostrou-se muito significativa. Tal fator teve também grande influência na formação da microestrutura e por conseqüência nas propriedades apresentadas pelas blendas. Materiais mais tenazes apresentam um comportamento mecânico mais interessante para peças porosas como as fabricadas por SLS, proporcionando uma maior resistência a propagação de trincas e defeitos. A fabricação das peças com gradiente de composição utilizando a sinterização seletiva a laser de blendas poliméricas, mostrou que várias microestruturas podem ser obtidas dependendo dos parâmetros de processo e da composição das blendas, permitindo a fabricação de componentes com variadas propriedades e funções ao longo do mesmo.

In this study, commercially available isotactic polypropylene (PP) and nylon-6 (PA6) blends and laminates were prepared, to develop a material with optimal water vapour and oxygen barrier properties. The effect of compatibilizers on phase dispersion has been investigated using three commercial Polybond's, PB3002, PB1001, and PB3009. Three compatibilizers prepared in-house were also used as, maleic anhydride(MA) grafted on PP, MA and butyl methacrylate(BMA) co-polymer grafted on PP, and BMA grafted on low density polyethylene. The effect of two silanes( methacrylate functional and vinyl functional) on PP were also investigated and also the plasticization of PA6 with formic acid. The results were compared with a commercial blend of PP and PA6, Orgalloy R-6000. Light microscopy with phase and fluorescence contrast has been used for morphological evaluation. Chemical changes were studied by Fourier Transform Infrared Spectroscopy and rheology by dynamic and steady state measurements. Barrier properties were determined gravimetrically for water vapour and organic solvents, and for oxygen by an Oxtran apparatus. The results have shown that phase dispersion can be more easily explained by molecular interactions than by the rheological parameters. The blend slip factor has been improved however by compatibilizers and consequently the phase dispersion, which had little effect on the barrier properties of the blends and indeed the laminates were more effective water vapour barriers. The availability of particular functional groups, which can interact with the permeant is the most important parameter, which can be affected by processing and blending conditions. The addition of hydrophobic functional groups into polypropylene was therefore the most effective method for enhancing the barrier properties of polypropylene. Cross-linking of the matrix polymer has improved the barrier properties to a lesser extent. It has also been shown, that PP solvent permeability (particularly di-chloromethane) can be improved, by silane addition.

As a renewable alternative to petroleum-based materials, wood or plant-based materials offer a greater prospect in the transition towards sustainable replacements. Native to wood, cellulose nanofibers (CNF) form the major load bearing component and possess tremendous potential as a reinforcement material in polymeric matrices. This study focuses on nanocellulose-based composites and aims to prepare and characterize bio-(nano)composites with high cellulose weight/volume fraction. The influence of nanoscale reinforcement or nanostructure on the macroscopic properties of the nanocomposites are investigated. Distinct prominence is given to the effect of nanocellulose dispersion and nanocellulose/polymer interface on the physical characteristics of biocomposites. In an initial study, effects of cellulose pulp fibers (micro scale dimensions) were investigated in pulp-fiber/polyamide 6 (PA6) composites system obtained by melt compounding and injection moulding. Strong influence on the pulp fiber reinforcement on the polymer matrix were observed with well dispersed pulp-fibers resulting in enhanced mechanical properties. Further, the effect of pulp fiber orientation within the composites was assessed and the composites with longitudinal fiber alignment recorded the highest mechanical properties. Regarding the investigation of PA6 and cellulose nanofibers, two different approaches were used to process the nanocomposites. Firstly, solvent casting-based approach, where CNF derived from enzymatic pretreatment were used to produce high content of CNF biocomposites by adopting a green solvent mixture to disperse the CNF and then impregnated by the dissolved polymer. Nanocomposite formulations up to 50 wt% of CNF were prepared and characterized. Unique characteristics due to the nanostructure of composites are discussed corresponding to CNF dispersion, CNF network, and CNF/matrix interface. In addition, a comparison between the reinforcement effect of pulp-fiber and CNF are discussed to emphasize the importance of nano-scale reinforcement and their contribution in enhancing the physical properties of thermoplastic-matrix composites. Subsequently, melt processing approach with a high speed thermo-kinetic mixer was used to prepare PA6/CNF nanocomposites with up to 25 wt% formulations. This study focused on the industrial scalability and provided a methodology to produce high cellulose content CNF-nanocomposites at a commercial spectrum. Mechanical properties were characterized at different relative humidity and the investigation revealed good hygro-mechanical properties. All in all, the current nanocomposites exhibited excellent dispersion without major agglomerations and the mechanical properties were significantly enhanced with the addition of CNF in both the approaches. Nanocomposites from polyamide-6 and high content of cellulose nanofibers were successfully prepared in this work, with remarkable improvement in the mechanical performance compared to the neat matrix, for both Young’s modulus and tensile strength. This in itself is an outstanding achievement, as compared to the literature up today. Moreover, the used methodology stands for industrial scalability and feasible processes towards the use of renewable and more sustainable products
Els materials procedents de plantes i arbres representen una alternativa renovable als materials procedents del petroli, en la transició cap a la producció de materials més sostenibles. Les nanofibres de cel·lulosa (CNF) procedents de la fusta són el principal component de càrrega i tenen un gran potencial com a material de reforç de matrius polimèriques. El present estudi es focalitza en la preparació i caracterització de bio-nano-compòsits amb un alt contingut en nanofibres de cel·lulosa (CNF). En concret, s’investiga la influència de la nanoestructura o del nano-reforç en les propietats macroscòpiques del nanocompòsit. L’efecte del grau de dispersió i de la interface nanocel·lulosa/polímer són factors claus sobre les propietats físiques dels nanocompòsits. En la primera part del treball, s’ha investigat l’efecte de fibres de cel·lulosa (de dimensions micro) com a reforç en materials compòsits de poliamida-6 (PA6)/cel·lulosa, obtinguts per un procés de barreja (melt-compounding) i posterior moldeig per injecció. S’ha observat una marcada influència de la pasta de cel·lulosa a l’hora d’actuar com a reforç de la matriu polimèirca, presentant una bona dispersió de les fibres, i conseqüentment es van obtenir molt bones propietats mecàniques. També s’ha investigat la influència del grau d’orientatió de les fibres dins dels compòsits, obtenint-se millors propietats quan les fibres estaven alineades longitudinalment en la direcció de l’assaig mecànic, Pel que fa al reforç de la matriu de PA6 amb nanofibres de cel·lulosa, s’han estudiat dos tipus diferents procediments per a processar els nanocompòsits de PA6/CNF. Per un costat es va fer servir el mètode solvent-càsting. En aquest cas, les CNF derivades d'un pretractament enzimàtic, es van dispersar i impregnar amb el polímer dissolt en una barreja de solvents “verds”. Es van produir biocompòsits amb un alt contingut de CNF, de fins al 50% en pes. Les elevades propietats dels materials es van justificar en base a la bona dispersió de les CNF, la mateixa xarxa de CNF en sí, i la interfase CNF/matriu. A més, una comparació entre l'efecte del reforç de polpa de fibres i reforç de CNF va emfatitzar la importància dels reforços nanométricos i la seva contribució en la millora de les propietats físiques dels compósits de matriu termoplàstica. Per altra banada es va fer utilitzar un procés de barreja tèrmica amb un mesclador termo-cinètic d'alta velocitat per a preparar els nanocompósits de PA6/CNF amb formulacions de fins a un 25 wt%. Aquest estudi se centra en l'escalat industrial i en proveir una metodologia per a produir nanocompósits de CNF amb un elevat contingut de cel·lulosa a nivell comercial. Les propietats mecàniques es van avaluar a diferents valors humitats relatives i es van obtenir molt bones propietats higromecàniques. En tots els casos, els materials nanocompósits presentaven una bona dispersió sense grans aglomeracions i les propietats mecàniques van millorar significativament amb l'addició de CNF en tots dos mètodes
Programa de Doctorat en Tecnologia

The objective of this study is to synthesize nematic-thermotropic liquid crystalline polymers (LCP) and determine their possible application areas. In this context, thirty different LCP&rsquo
s were synthesized and categorized with respect to their fiber formation capacity, melting temperature and mechanical properties. The basic chemical structure of synthesized LCP&rsquo
s were composed of p-acetoxybenzoic acid (p-ABA), m-acetoxybenzoic acid (m-ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA) and isophthalic acid (IPA) and alkyl-diacids monomers. In addition to mentioned monomers, polymers and oligomers were included in the backbone such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) polymers, and polybutylene naphthalate (PBN), polyhexylene naphthalate (PHN) and poly butylene terephthalate (PBT) oligomers that contain different kinds of alkyl-diols. We adjusted the LCP content to have low melting point (180oC-280oC) that is processable with thermoplastics. This was achieved by balancing the amount of linear (para) and angular (meta) groups on the aromatic backbones together with the use of linear hydrocarbon linkages in the random copolymerization (esterification) reaction. LCP species were characterized by the following techniques
Polarized Light Microscopy, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Analysis (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray Scattering (WAXS, Fiber diffraction), surface free energy, end group analysis (CEG), intrinsic viscosity (IV) and tensile test. According to these analysis LCPs were classified into five main categories
(I) fully aromatics, (II) aromatics+ PET/PEN, (III) aromatics + oligomers (IV) aromatics + short aliphatic diacids, (V) aromatics + long aliphatic diacids. The foremost results of the analysis can be given as below. DSC analysis shows that some LCPs are materials that have stable LC mesogens under polarized light microscopy. In TGA analysis LCPs that have film formation capacity passed the thermal stability test up to 390oC. NMR results proved that predicted structures of LCPs from feed charged to the reactor are correct. In FTIR due to the inclusion of new moieties, several peaks were labeled in the finger-print range that belongs to reactants. In X-ray analysis, LCP24 (containing PET) was found to be more crystalline than LCP25 (containing PEN) which is due to the symmetrical configuration. Block segments were more pronounced in wholly aromatic LCP2 than LCP24 that has flexible spacers. Another important finding is that, as the amount of the charge to the reactor increases CEG value increases and molecular weight of the product decreases. Selected group V species were employed as reinforcing agent and mixed with the thermoplastics
acrylonitrile butadiene styrene (ABS), nylon6 (PA6), polyethylene terephthalate (PET), polypropylene (PP) and appropriate compatibilizers in micro compounder and twin screw extruder. The blends of them were tested in dog-bone and/or fiber form. In general LCPs do not improve the mechanical properties except in composite application with polypropylene. A significant increase in tensile properties is observed by LCP24 and LCP25 usage. Capillary rheometer studies show that the viscosity of ABS decreases with the inclusion PA6 and LCP2 together. In addition to the composite applications, some LCPs are promising with new usage areas. Such as nano fibers with 200nm diameter were obtained from LCP27 by electrospinning method. The high dielectric constant of LCP29 has shown that it may have application areas in capacitors.

La morphologie et les propriétés de sorption d'eau et d'éthanol de films extrudés minces de polyamide 6 ont été étudiées pour différentes conditions de mise en oeuvre (température de chill roll (TCR) de 50 et 125°C et taux d'étirage compris entre x et y). L'influence de l'ajout de faibles taux de nanocharges lamellaires (montmorillonite (MMT) ou phosphate de Zirconium (ZrP)) a également été évaluée. L'étirage n'a, dans la gamme étudiée, aucun effet sur la morphologie et les propriétés de sorption des films. Les films de PA6 préparés à une température de chill roll de 50°C présentent en revanche une proportion de phase cristalline g plus faible que les films préparés à une TCR de 125°C. L'épaisseur des lamelles cristallines y est plus fine et la mobilité des chaînes de la phase amorphe y est réduite. L'ajout de faibles taux de montmorillonite à une TCR de 50°C modifie significativement la mobilité des chaînes de la phase amorphe, les proportions des phases cristallines a et g et l'orientation des lamelles cristallines, contrairement à une TCR de 125°C où l'impact de la MMT n'a été observé qu'au niveau de l'orientation de la phase cristalline g. Les mécanismes de sorption de vapeur d'eau et d'éthanol ont été étudiés pour l'ensemble des films. Les isothermes de sorption ont été modélisées afin d'étudier plus particulièrement les phénomènes d'agrégation observés à haute activité. Une modélisation des courbes cinétiques a également été proposée sur la base de l'approche de Berens et Hopfenberg. La confrontation des données thermodynamiques et cinétiques de sorption et des paramètres morphologiques caractéristiques des matériaux a permis de conclure à un rôle prépondérant des interfaces entre zone amorphe et zone cristalline sur le transport

La morphologie et les propriétés de sorption d’eau et d’éthanol de films extrudés minces de polyamide 6 ont été étudiées pour différentes conditions de mise en oeuvre (température de chill roll (TCR) de 50 et 125°C et taux d’étirage compris entre x et y). L’influence de l’ajout de faibles taux de nanocharges lamellaires (montmorillonite (MMT) ou phosphate de Zirconium (ZrP)) a également été évaluée. L’étirage n’a, dans la gamme étudiée, aucun effet sur la morphologie et les propriétés de sorption des films. Les films de PA6 préparés à une température de chill roll de 50°C présentent en revanche une proportion de phase cristalline g plus faible que les films préparés à une TCR de 125°C. L’épaisseur des lamelles cristallines y est plus fine et la mobilité des chaînes de la phase amorphe y est réduite. L’ajout de faibles taux de montmorillonite à une TCR de 50°C modifie significativement la mobilité des chaînes de la phase amorphe, les proportions des phases cristallines a et g et l’orientation des lamelles cristallines, contrairement à une TCR de 125°C où l’impact de la MMT n’a été observé qu’au niveau de l’orientation de la phase cristalline g. Les mécanismes de sorption de vapeur d’eau et d’éthanol ont été étudiés pour l’ensemble des films. Les isothermes de sorption ont été modélisées afin d’étudier plus particulièrement les phénomènes d’agrégation observés à haute activité. Une modélisation des courbes cinétiques a également été proposée sur la base de l’approche de Berens et Hopfenberg. La confrontation des données thermodynamiques et cinétiques de sorption et des paramètres morphologiques caractéristiques des matériaux a permis de conclure à un rôle prépondérant des interfaces entre zone amorphe et zone cristalline sur le transport
The morphology and water and ethanol sorption properties of thin films made of polyamide 6 were studied in relation to different transformation conditions, namely chill roll temperature (TCR) (50 and 125°C) and stretching ratio (between 6 and 10.8). The influence of nanofillers (montmorillonite (MMT) and zirconium phosphate (ZrP)) was also investigated. It was observed that stretching has no influence on neither the morphology nor the sorption properties in the studied range. In contrast unfilled films prepared at a chill roll temperature of 50°C have a lower amount of g crystalline phase, thinner cristalline lamellae and reduced amorphous phase mobility than films prepared at a chill roll temperature of 125°C. Adding low amounts of MMT at a TCR of 50°C has a remarkable impact on chain mobility, a and g crystalline phase fractions and lamellar orientation whereas the nanoparticules added at a TCR of 125°C only affect the crystalline orientation. Vapor sorption mechanisms were studied for both filled and unfilled films. The sorption isotherm curves were modelled to obtain a deeply understanding of the aggregation phenomena observed at high activity. Modelling of the kinetics was proposed according to Berens and Hopfenberg approach. Coupling the thermodynamics and kinetics of sorption with the morphological data leads to the conclusion that the interfaces between the amorphous and crystalline domains play a critical role on transport properties

Background: Food allergy affects an estimated 8% of children and 3% of adults in the United States. Food‐allergic individuals increasingly use the web for medical information. We sought to determine the educational quality of food allergy YouTube videos. Methods: We performed a YouTube search using keywords “food allergy” and “food allergies”. The 300 most viewed videos were included and analyzed for characteristics, source, and content. Source was further classified as healthcare provider, alternative medicine provider, patient, company, media, and professional society. A scoring system (FA‐DQS) was created to evaluate quality (−10 to +34 points). Negative points were assigned for misleading information. Eight reviewers scored each video independently. Results: Three hundred videos were analyzed, with a median of 6351.50 views, 19 likes, and 1 dislike. More video presenters were female (54.3%). The most common type of video source was alternative medicine provider (26.3%). Alternative treatments included the following: water fast, juicing, Ayurveda, apple cider, yoga, visualization, and sea moss. Controversial diagnostics included kinesiology, IgG testing, and pulse test. Almost half of the videos depicted a non‐IgE‐mediated reaction (49.0%).Videos by professional societies had the highest FA‐DQS (7.27). Scores for videos by professional societies were significantly different from other sources (P < .001). There was a high degree of agreement among reviewers (ICC = 0.820; P < .001). Conclusion: YouTube videos on food allergy frequently recommend controversial diagnostics and commonly depict non‐IgE‐mediated reactions. There is a need for high‐quality, evidence‐based, educational videos on food allergy.

Orientador: Cecilia Amélia de Carvalho Zavaglia
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este mundo que vivemos está se tornando extremamente competitivo dia após dia, a apenas cinquenta anos, os motores ciclo Otto permaneciam quase os mesmos quando foram inventados pelo engenheiro alemão Nikolaus August Otto no final do século 19. Foi somente no final da década de 1970 que os antigos motores começaram a ganhar apelos tecnológicos, como injeção eletrônica, ignição eletrônica, controle de emissões e gás carbônico, etc., com isso, todas as montadoras começaram a buscar soluções que fizessem do seu veículo, o melhor ou o mais econômico e menos poluente. Face às novas exigências governamentais ao redor do mundo, todas as montadoras e autopeças estão trabalhando incansavelmente na busca de várias soluções, soluções estas que vão desde a diminuição de emissões evaporativas, redução do consumo de combustível, seja em função de um motor mais econômico quanto a melhorias de aerodinâmica, que resulta em menor fenômeno de arraste e consequente economia de combustível. Sabe-se também que redução de peso impacta diretamente na redução do fenômeno de arraste, portanto, gera um menor consumo de combustível, por isso, estamos vendo o crescente interesse das indústrias automotivas em substituir as antigas e atuais peças em metal que são normalmente pesadas, para peças extremamente mais leves em plásticos de engenharia e com alta resistência térmica, mecânica, etc., e quem nem por isso não mantenham a mesma qualidade funcional das peças em metal. Plásticos de engenharia como a Poliamida 6 com 35% de fibra de vidro (PA6 GF35), já estão sendo aplicados no mercado automotivo a pelo menos quase 20 anos, pois os primeiros coletores de admissão e filtro de ar em plástico nasceram utilizando esta matéria prima, hoje em dia, nesta busca por redução de peso e consequentemente preço, um material plástico chamado Polipropileno com 35% de fibra de vidro (PP GF35), que até não muito tempo atrás era de segunda linha, passa a ser de suma importância para alcançar objetivos que técnicos e monetários que até outro dia, somente era possível com a Poliamida 6 com 35% de fibra de vidro (PA6 GF35). Hoje em dia o polipropileno é um polímero de destaque no setor automotivo, pois ele se destaca pela alta resistência química e solvente, boa estabilidade dimensional, flexibilidade, durabilidade, excelente balanço entre impacto e rigidez. Sendo assim, uma matéria prima que era utilizada na fabricação de fios de tecelagem, embalagens flexíveis, brinquedos, copos plásticos, corpo de eletrodomésticos, está sendo usado em peças de alto valor agregado, alto e com tal desempenho técnico como um coletor de admissão e em quase todas as peças de acabamento interno e externo da maioria das empresas automotiva do Brasil e do mundo
Abstract: Due to strong competition among automotive companies around the world, and also by the incessant search in order to reduce weights in vehicles, reducing fuel consumption and therefore reduce carbonic gas emissions, the automakers are working on several fronts in order to reach the targets already defined through the government¿s laws. Given these several requests, the automotive parts industries, together with the raw materials industry, are working to achieve these goals. Thus, reductions in power cell consequently the numbers of cylinders in the engines are already a reality, for example three cylinders engines are replacing the four cylinder engines, and the most important comment, and they are keeping the same driving force. In addition, we are working so hard in order to replace the current Intake Manifold in Polyamide 6 with 35% glass fiber (PA6 GF35), for Polypropylene with 35% glass fiber (PP GF35), so is being reduced around 15% of weight, changing only the raw material. Polypropylene (PP), who was a second-line raw material in the past at the automotive world, becomes to move of other excellent quality of baseline of importance, as well, as reducing the weight of the piece, how it reduces the price piece value, as also the polypropylene is cheaper around of 15% more than the polyamide 6. This new polypropylene for Intake Manifold needs to be heat stabilizer, but needs not to be flame retardant. Many characteristics had been considered very important in the decision matrix in order to reach a good polymer, as well, mechanical resistance to the tensile and impact, density, water absorption, thermal resistance, chemical resistance regarding fuel, injection process and the availability of mass production. Only twenty years ago, all engines Cycle Otto were manufactured, using Intake Manifold in aluminum material, due to the aluminum caused a chemical reaction in physical contact with the alcohol, it was invented the Intake Manifold in Polyamide 6. Today all the automotive world uses Intake Manifold in Polyamide 6 for Cycle Otto application, but due to the excellent results using the polypropylene raw material, all automakers are moving to this new raw material, which in a not so distant past, was regarded as the second line in the automotive industry
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

Any device connected to the Internet needs to be protected. Using a firewall as a first line of defence is a very common way to provide protection. A firewall can be set up to protect an entire network or just a single host. As it is becoming more and more popular to connect mobile phones and other hand held devices to the Internet, the big question is;"how to protect those devices from the perils of the Internet?" This work investigates issues with the implementation of a firewall system for protecting mobile devices. Firewall administration is an error prone and difficult task. Setting up a correctly configured firewall in a network setting is a difficult task for a network administrator. To enable an ordinary mobile phone user to set up a firewall configuration to protect his mobile phone it is important to have a system that is easy to understand and warns the user of possible mistakes. Generic algorithms for firewall rule-set sorting and anomaly discovery are presented. This ensures that the rule-set is error free and safe to use. This is a vital part of any firewall system. The prototype developed can be used to find errors in existing firewall rule-sets. The rule-set can be in either a native firewall configuration format (currently only IPF is supported) or in a generic XML format. This generic XML format was developed as a part of this research project. Further a new graphical visualization concept that allows the end user to configure an advanced firewall configuration from a device with a small screen and limited input possibilities is presented.

Polymer nanofibers used for the construction of triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are new and promising technologies for energy recovery. Thanks to the generation of electrical energy based on mechanical movement (deformation), these fibers can find application in the field of self-powered electronic devices. In this work, three nanofibrous structures of materials were prepared by electrostatic spinning: pure polyvinylidene fluoride (PVDF), pure polyamide-6 (PA6) and their mixed combination PVDF / PA6. Non-destructive analyzes such as Raman spectroscopy, FTIR, XPS and electron microscopy were used to study the properties of nanofibers. Analyzes confirmed the positive effect of electrostatic spinning of polymers on the support of the formation of highly polar crystalline -phase in PVDF and , -phase in PA6. The structure arrangement of the nanofibrous material and their defects were observed by scanning electron microscopy (SEM). Furthermore, the contact angle of the wettability of the liquid on the surface was measured for the materials, and the permittivity was measured to monitor the dielectric properties. The described results make the mixed material PVDF / PA6 very promising for further research in the field of nanogenerators and functional textiles.

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Esta pesquisa de doutorado analisou a Revista Americana, publicação protagonizada por diplomatas brasileiros ligados ao Ministério das Relações Exteriores e que circulou de forma não contínua entre 1909 e 1919. A revista se transformou em espaço de divulgação de diferentes aspectos da política, da cultura e da história do Brasil e de outras Repúblicas sul-americanas. Pretendeu-se, durante o estudo, compreender quais seriam os objetivos implícitos e explícitos desse impresso, bem como analisar qual seria o papel proposto para o corpo diplomático no sentido de viabilizar um projeto de pan-americanismo. A pesquisa partiu do pressuposto de que a Revista foi um instrumento de estratégia utilizado pelo Itamaraty no sentido de pensar e promover uma aproximação entre o Brasil e a América do Sul. Além disso, a partir da leitura dos exemplares, investigou-se qual seria o destaque do papel exercido pela diplomacia da República brasileira na difusão de representações de Brasil como possível líder diplomático do continente. Também foram localizadas as representações discutidas no periódico em relação aos problemas correntes do continente e suas possíveis soluções propostas pelos intelectuais, que eram oriundos não apenas do Brasil, mas de outros países do continente americano. Analisou-se, principalmente, quais representações de futuro são defendidas na Revista, visando apresentar o Brasil como país pacífico, civilizado, bem como de um continente americano moderno e com relações solidárias entre os países. O estudo se fundamentou no esquema conceitual de Roger Chartier (representações, práticas culturais, apropriação e circulação); no conceito de intelectuais proposto por Sirinelli (1998) e de diplomacia cultural de Ribeiro (1989). Concluiu-se que na Revista ocorria a valorização de elementos de uma diplomacia cultural, por meio de uma retórica pan-americana, que deveria servir de base para a construção de novas identidades, marcada por características próprias e específicas do continente americano. O pan-americanismo pensado dessa maneira fundamentou a existência de uma geração de intelectuais que puseram a circular na publicação projetos de futuro que representavam a América não apenas como espaço, mas principalmente como sentimento.

Ce travail présente des techniques, basées sur les modes glissants, permettant d'estimer des paramètres, de reconstruire des variables (observateur) et/ou de commander un moteur pas-à-pas. Le but étant de réaliser un suivi de trajectoire en position robuste avec un minimum de capteurs. Après avoir défini le contexte de l'étude, la planification et l'optimisation des trajectoires et les objectifs, le banc réalisé au LAGIS est décrit. Il est alors présenté une identification des paramètres par plusieurs méthodes. Les propriétés de platitude du moteur pas-à-pas sont utilisées. Des commandes classiques sont rapidement développées et illustrées de résultats expérimentaux. Cependant, elles ne sont pas assez de robustes vis à vis de perturbations internes (incertitudes ou variations paramétriques) ou externes (couple de charge). Pour pallier ce problème, des lois de commande par modes glissants, d'ordre 1 et 2, sont alors utilisées. Après une description, des expérimentations sont menées qui démontrent les qualités des modes glissants. Un nouveau mode glissant d'ordre 3, basé sur l'homogénéité géométrique et un terme additionnel de type mode glissant intégral, est introduit pour diminuer la réticence. Les résultats expérimentaux montrent une très bonne précision, une diminution de la réticence et de la consommation énergétique. Pour les commandes d'ordre deux et trois, des observateurs par modes glissants d'ordre 2 sont utilisés avec succès pour se passer d'un capteur de vitesse.

Reproduction de : Thèse de doctorat : Automatique et informatique industrielle : Villeneuve d'Ascq, Ecole centrale de Lille : 2006.
Titre provenant de la page de titre du document numérisé. Bibliogr. p. 223-228.

Le PAF (Platelet-Activating Factor) est un médiateur reconnu pour son implication dans plusieurs effets physiologiques et pathologiques, particulièrement les états inflammatoires. À l'instar du PAF, les lymphocytes T Th17 sont aussi reconnus comme exerçant un rôle majeur dans la physiopathologie des maladies auto-immunes. L'objectif de ce projet est de déterminer s'il existe un lien entre ces deux composants. En fait, nous avons émis l'hypothèse que le PAF pourrait provoquer une production de cytokines spécifiques par les cellules présentatrices d'antigène qui elles, interagissant avec les lymphocytes T, pourraient mener ultimement à une différentiation en Th17. En effet, les cellules T ne peuvent interagir directement avec le PAF puisqu'elles n'expriment pas de récepteur pour celui-ci à leur surface. Les cellules T Th17 expriment un facteur de transcription spécifique RORr, nécessitent absolument la sous-unité IL-23p19 pour leur expansion et produisent IL-17. Nous avons donc, dans un premier temps, regardé la capacité d'un type de cellules présentatrices d'antigène, les cellules de Langerhans à produire IL-23p19 en réponse au PAF. Ensuite, nous avons mis en contact ces cellules de Langerhans pré-stimulées au PAF avec des lymphocytes T activés pendant 5 jours pour vérifier l'expression de RORII et la production d'IL-17 dans ces lymphocytes T, plus précisément les lymphocytes T CD4 + . Cette étude nous a permis de mettre en évidence que certains éléments impliqués dans les processus inflammatoires sont possiblement inséparables et interagissent probablement les uns avec les autres pour mener aux séquelles multiples de l'inflammation.

Abstract My Ph.D. project focused on the tailoring of the surface properties of oxide substrates for the preparation of advanced composite materials and devices. The initial focus of my research activity was the surface modification of halloysite nanotubes (HNT), a natural material with unique structural features. I then extended my investigation to other oxides (titanium dioxide, TiO2, and Superparamagnetic Iron Oxide Nanoparticles, SPION), applying the surface modification approaches developed for HNT substrates. The resulting oxide-based hybrid systems showed promising properties as stimuli-responsive devices for health and environmental applications, and as fillers for polymeric nanocomposites with enhanced durability. The main results obtained for each oxide material will be presented in the following sections. 1. Halloysite nanotubes (HNT) Halloysite is a polymorph of kaolinite which naturally wraps itself to form tubular structures (Figure 1A). It is one of the few nanotubular systems presenting an inner lumen and an outer surface characterized by different surface charge and structural composition: the internal surface exposes aluminium hydroxyl groups, while the outermost layer is silica[1]. Among its many potential applications, its tubular dual structure has sparked interest in the field of nanomedicine and polymer nanocomposites[2]. However, only few reports investigated the possibility of a selective functionalization of the inner and outer HNT surfaces. During my first year of PhD, I investigated the selective functionalization of HNT with phosphonates, hetero-organic compounds bearing a C PO(OH)2 group, as potential site-specific linkers for the grafting of active molecules. I took advantage of the phosphonic acid selectivity towards certain oxides (especially aluminium oxides) to achieve surface-specific functionalization of HNT. An in-depth comprehension of such hybrid systems is no trivial matter, as the inner and outer HNT surfaces possess different accessibility and reactivity but are not separable. For this reason, beside HNT, I used purposely prepared model oxides, mimicking the inner and outer nanotube surfaces, to better study the actual selectivity towards SiO2 and AlOOH exhibited by the phosphonate moiety. Octylphosphonic acid (OPA) was chosen as functionalizing agent, as its alkyl chain allowed me to monitor the surface modification through changes in the water contact angle (θ). I found that the oxide isoelectric point (pHIEP) plays a major role in determining a stable OPA adsorption: while AlOOH showed good reactivity towards OPA, SiO2, which is negatively charged at the impregnation pH (pH 4), did not react with the phosphonate heads. The functionalization reversibility was also assessed: Samples showed OPA release at pH values more alkaline than the oxide isoelectric point, when the surface charge is negative. Overall, these results support an OPA-oxide bond governed both by electrostatic and covalent forces. The selective functionalization of HNT inner lumen was also demonstrated via a combination of characterization techniques, including FTIR spectroscopy, ζ-potential measurement and water dispersibility assay. Another scantly investigated topic regarding HNT nanosystems is their covalent modification. Covalent grafting allows for a superior control over the release kinetics of active principles, as the initial release burst observed in the case of electrostatically bound compounds is greatly reduced. In this respect, I studied the covalent attachment of a biologically active molecule to HNT via an imine bond. This type of covalent bond was chosen to open up the possibility for a controlled release of the bioactive molecule activated by pH changes. To this purpose, HNT was functionalized with (3 aminopropyl)triethoxysilane (APTES), a bifunctional linker which can cover the oxide surface with amino groups. Despite being non-selective for either of the two phases, it was chosen based on the relative ease with which it can be grafted to the substrate. Then, tetrathia[7]helicene aldehyde (7-THA) was bound to HNT via APTES, exploiting imine chemistry. 7-THA belongs to a group of polyaromatic molecules capable, thanks to their peculiar helicoidal shape, of intercalating DNA strands, which is at the basis of anti-sense therapy[3]. Nonetheless, HNT abysmal water solubility highly reduces their bioavailability and makes the use of hydrophilic nanocarriers necessary. I tested the relative release efficiency of 7-THA under slightly different pH conditions, representative of lysosomal, tumoral and healthy extracellular pH values. The resulting HNT-7TH system was studied in detail via XPS and angle-resolved near edge X-ray absorption fine structure spectroscopy (NEXAFS) at the Material Science Beamline of the Elettra synchrotron facility. The latter characterization technique required the synthesis and functionalization of oxide films replicating HNT surfaces, in order to probe the orientation of a population of adsorbed molecules with respect to the surface plane. NEXAFS results suggested a preferential orientation of the aromatic rings of helicene normal to the oxide surface, possibly as a result of π-π stacking interactions (Figure 1B). XPS analyses were performed at each stage of the preparation process of HNT-7TH and after the release test at pH 5 (Figure 1C): the observed change in the elemental composition indicated a release of 70% of the loaded 7-THA as a result of pH change. Given the interest for tumour therapy applications, in vitro tests were carried out to assess the selectivity of this system on cancer cells. The effect of HNT-7TH on the viability of bladder cancer cells was tested by Dr Riccardo Vago at the IRCCS San Raffaele Scientific Institute. Two different cell lines, named 5637 and HT-1376, with an extracellular pH of 7.2 and 6.8 respectively, were subjected to increasing concentrations of HNT 7TH and bare HNT as control. HNT 7TH was found to cause a more marked reduction in cell viability on the HT-1376 cell line, suggesting a faster release of the cytotoxic 7-THA at slightly acidic pH values. Release kinetics also supported this hypothesis: a new model system utilizing benzodithiophene (BDT), a more water-soluble mimic of 7-THA, was prepared analogously to the HNT-7TH powders. The release of BDT was monitored via UV-vis spectroscopy at pH 5.0, 6.8 and 7.4. The amount of released BDT at pH 7.4 was negligible even after 48 h; decreasing the pH value to 6.8 visibly increased release rates, while the release efficiency was highest for the treatment at pH 5.0. The natural origin of HNT causes a marked variability in its physicochemical features, such as its morphology and surface charge, depending on the extraction site[4]. I investigated this aspect, often overlooked in the literature, with respect to the integration of HNT as nanofillers in polymer composites. Halloysite has been investigated as filler owing to its low cost, thermal and mechanical resistance, and high aspect ratio, which is crucial to guarantee strong polymer-filler interactions[5]. In this regard, I investigated also the effect of surface functionalization in promoting HNT compatibility with the chosen polymer matrix, Polyamide 6 (PA6). PA6 has a broad range of applications, from the automotive sector to the textile industry, owing to its good mechanical performances and high thermal resistance. However, when exposed to humid conditions, it suffers from degradation in a matter of few weeks[6], as water can interpenetrate within the hydrogen bonds between –NH and C=O groups and disrupt them, leading to the loss of tensile strength and elasticity[6–9]. The addition of nanotubular fillers represents a viable strategy for overcoming this issue, although the additive/polymer interface at high filler content can become a privileged site for moisture accumulation[10]. For this reason, HNT were added to PA6 in very low amounts (< 5%w). The roles played in the reinforcement of the polymer by the physicochemical properties of HNT from two different sources and their functionalization with APTES were investigated in composites prepared by two different dispersion techniques (in situ polymerization vs. melt blending). The aspect ratio (5 vs. 15) and surface charge (−31 vs. −59 mV) of the two HNT samples proved crucial in determining their distribution within the polymer matrix: both in situ and melt blending dispersion techniques showed that lower surface area, higher aspect ratio and greater surface charge enhance filler incorporation and improve the final composite performance. Finally, filler surface modification with APTES played a major role in the durability of the PA6-HNT nanocomposites: after 1680 h of hydrothermal ageing, functionalized HNT reduced the diffusion of water into the polymer, lowering water uptake after 600 h up to 90%, increasing the materials durability. Positive effects could also be measured regarding the molecular weight distribution and rheological behaviour. These improvements could be related to the presence of amino groups on the HNT surface, which lowered the filler surface energy and prevented the diffusion of water molecules into the nanocomposites[11]. 2. Titanium dioxide TiO2 is arguably the most extensively investigated semiconductor for photocatalytic applications, from solar cells to pollutant abatement. However, applications of TiO2 for the preparation of smart surfaces are comparatively less common. My research interest in TiO2 started with the preparation of surfaces with controlled wetting features. First, the surface of commercial TiO2 powders was functionalized with perfluorinated alkylsilanes. Then, I employed the photocatalytic features of TiO2 films to produce patterned surfaces with superhydrophilic/superhydrophobic contrast by means of photocatalytic lithography. During the course of my second year of PhD, I focused on the deposition of TiO2 films with controlled porosity followed by their surface modification to impart them functional properties. These systems were applied as photo renewable coatings for electrochemical sensors and stimuli-responsive surfaces for the controlled release of active compounds. Control over film porosity was achieved by a hard-template approach using polystyrene (PS) nanospheres of different sizes, both commercial and synthesized in-house following a classical procedure[12]. Different film deposition strategies were investigated. First, I deposited a TiO2 layer on top of a porous SiO2 coating on a FTO electrode. Extensive characterization via cyclic voltammetry showed that the addition of a TiO2 layer increased peak currents due to the promoted diffusion of the analyte in the porous structure, driven by capillary effects[13] (Figure 2A). Furthermore, the TiO2 layer promoted the light-activated regeneration of the electrode surface after having been fouled. Starting from there, I investigated the possibility of pure TiO2 mesoporous films, a task made difficult by the intrinsic incompatibility between an alcohol-based TiO2 sol, extremely prone to hydrolysis, and a water-based PS suspension. This issue was solved by either adopting an aqueous TiO2 sol, slowly evaporated in presence of the particle templates (Figure 2B), or by performing a solvent exchange procedure on the PS suspension. The latter procedure resulted in pure TiO2 films with easily tuneable thickness and homogeneous porosity, opening the door to a fine tuning of the cyclovoltammetric response. The self-cleaning features of the pure TiO2 films were also tested by purposely fouling their surface with long-alkyl chain substituents: a fast and complete regeneration of the surface was achieved upon irradiation with UV light. The prepared pure TiO2 porous films were also used as substrates for the loading of bioactive substances. Cinnamaldehyde, a natural substance known for its antimicrobial properties but unstable in environmental conditions, was anchored to the film surface via APTES linkers through an imine bond, using a protocol similar to the one developed for 7-THA-loaded HNT. The immobilized cinnamaldehyde proved stable to environmental conditions for months and tests of pH triggered release performed at pH 5.5 and 7.4, showed a faster release at lower pH values. Finally, the photoactive nature of the oxide substrate could be used to promote the self-cleaning of the fouled surface after usage: after UV-light regeneration, the TiO2 film could be functionalized anew and reused. 3. Superparamagnetic Iron Oxide Nanoparticles (SPION) During my third year of PhD, I spent six months at the Technische Universiteit Delft, Netherlands, in the Advanced Soft Matter group, under the supervision of Dr Laura Rossi. There my research focused on the synthesis and surface modification of Ultrasmall SPION. SPION have gained increasing attention thanks to their peculiar behaviour: being smaller than a single magnetic crystal domain, they are free to rotate unless a specific orientation is induced by an external field. Due to their magnetic properties, they can be adopted in hyperthermia, drug delivery and as contrast agents (CA) for magnetic resonance imaging (MRI)[14]. Contrast agents are commonly used to speed up either T1 or T2 relaxation, enhancing the local contrast in pathological tissue to produce more detailed images. T1 CA are commonly represented by gadolinium complexes, while SPION are generally adopted as T2 CA. The first are preferred by radiologists, while the latter are less favoured because the darker tones they provide can be mistaken with low resolution and background interference[15,16]. Nonetheless, Gd-based CA present a serious health risk for those patients unable to efficiently remove these heavy metal complexes due to pre-existent kidney or liver pathologies[17]. While most SPION act as T2 CA, several papers report their potential use as T1 CA if their size is sufficiently small, indicatively less than 4 nm[18,19]. These materials are known as Ultrasmall SPION, or USPION. My aim was to develop a synthetic protocol to prepare USPION suitable as T1 contrast agents via co-precipitation, to minimize synthetic requirements. To this purpose, the influence of several parameters such as reaction temperature, base type, purification procedure, stabilizing agent and precursor concentration was investigated. Particles were synthesised at room temperature (RT) and 50°C, using NH4OH, N(CH3)4OH or NaOH as base. Particle purification was performed via magnetic decantation, centrifugation and dialysis against different solutions (water, citric acid and sodium citrate solutions). Sodium oleate, (3-aminopropyl)triethoxysilane (APTES) and citric acid were tested as stabilizing agents and precursor concentration was varied between 1 M and 0.5 M. It was found that the best results were obtained at room temperature and that the peptizing effect of the tetramethylammonium ion is crucial to guarantee an optimal colloidal stability, making N(CH3)4OH the base of choice. The concentration of starting precursor solutions proved to be the determining factor acting on particle size, as halving it led to a narrow particle size distribution centred around 3 nm, a significant shift from the starting 7 nm (Figure 3). Centrifugation was ineffective when adopted to wash the nanoparticles, but it proved a promising size-selection tool that could be combined with dialysis in an efficient work up protocol. Dialysis proved to be the most efficient technique to remove potentially toxic impurities, but it negatively impacted the colloidal stability, which could be mitigated by the use of a proper stabilizing agent. To preserve a high colloidal stability even after the removal of N(CH3)4OH, surface modification with several stabilizing agents was tested. Among the tested molecules, citric acid was the only one to show positive effects on particle size and aggregation, more so when added before the start of particle nucleation. These results represent a promising advance in the development of efficient T1 contrast agents based on USPION in terms of lowering the synthetic requirements: monodisperse magnetic nanoparticles were prepared through a simple co-precipitation procedure, performed at room temperature, without the aid of any polymeric additive. References [1] Y. Lvov, W. Wang, L. Zhang, R. Fakhrullin, Halloysite Clay Nanotubes for Loading and Sustained Release of Functional Compounds, Adv. Mater. 28 (2016) 1227–1250. doi:10.1002/adma.201502341. [2] E. Abdullayev, V. Abbasov, A. Tursunbayeva, V. Portnov, H. Ibrahimov, G. Mukhtarova, Y. Lvov, Self-healing coatings based on halloysite clay polymer composites for protection of copper alloys, ACS Appl. Mater. Interfaces. 5 (2013) 4464–4471. doi:10.1021/am400936m. [3] E. Licandro, S. Cauteruccio, D. Dova, Thiahelicenes, in: 2016: pp. 1–46. doi:10.1016/bs.aihch.2015.12.001. [4] E. Joussein, S. Petit, J. Churchman, B. Theng, D. Righi, B. Delvaux, Halloysite clay minerals – a review, Clay Miner. 40 (2005) 383–426. doi:10.1180/0009855054040180. [5] M.R. Ayatollahi, S. Shadlou, M.M. Shokrieh, M. Chitsazzadeh, Effect of multi-walled carbon nanotube aspect ratio on mechanical and electrical properties of epoxy-based nanocomposites, Polym. Test. 30 (2011) 548–556. doi:10.1016/j.polymertesting.2011.04.008. [6] I. Ksouri, O. De Almeida, N. Haddar, Long term ageing of polyamide 6 and polyamide 6 reinforced with 30% of glass fibers: physicochemical, mechanical and morphological characterization, J. Polym. Res. 24 (2017) 133. doi:10.1007/s10965-017-1292-6. [7] H. Shinzawa, J. Mizukado, Water absorption by polyamide (PA) 6 studied with two-trace two-dimensional (2T2D) near-infrared (NIR) correlation spectroscopy, J. Mol. Struct. 1217 (2020) 128389. doi:10.1016/j.molstruc.2020.128389. [8] K.R. Rajeesh, R. Gnanamoorthy, R. Velmurugan, Effect of humidity on the indentation hardness and flexural fatigue behavior of polyamide 6 nanocomposite, Mater. Sci. Eng. A. 527 (2010) 2826–2830. doi:10.1016/j.msea.2010.01.070. [9] D.P.N. Vlasveld, J. Groenewold, H.E.N. Bersee, S.J. Picken, Moisture absorption in polyamide-6 silicate nanocomposites and its influence on the mechanical properties, Polymer (Guildf). 46 (2005) 12567–12576. doi:10.1016/j.polymer.2005.10.096. [10] K.P. Pramoda, T. Liu, Effect of moisture on the dynamic mechanical relaxation of polyamide-6/clay nanocomposites, J. Polym. Sci. Part B Polym. Phys. 42 (2004) 1823–1830. doi:10.1002/polb.20061. [11] K. Prashantha, M.F. Lacrampe, P. Krawczak, Processing and characterization of halloysite nanotubes filled polypropylene nanocomposites based on a masterbatch route: effect of halloysites treatment on structural and mechanical properties, Express Polym. Lett. 5 (2011) 295–307. doi:10.3144/expresspolymlett.2011.30. [12] J.W. Goodwin, J. Hearn, C.C. Ho, R.H. Ottewill, Studies on the preparation and characterization of monodisperse polystyrene latices, Colloid Polym. Sci. 252 (1974) 464–471. [13] L. Rimoldi, V. Pifferi, D. Meroni, G. Soliveri, S. Ardizzone, L. Falciola, Three-dimensional mesoporous silica networks with improved diffusion and interference-abating properties for electrochemical sensing, Electrochim. Acta. 291 (2018) 73–83. doi:10.1016/j.electacta.2018.08.131. [14] J. Dulińska-Litewka, A. Łazarczyk, P. Hałubiec, O. Szafrański, K. Karnas, A. Karewicz, Superparamagnetic Iron Oxide Nanoparticles—Current and Prospective Medical Applications, Materials (Basel). 12 (2019) 617. doi:10.3390/ma12040617. [15] Y. Okuhata, Delivery of diagnostic agents for magnetic resonance imaging, Adv. Drug Deliv. Rev. 37 (1999) 121–137. doi:10.1016/S0169-409X(98)00103-3. [16] J.-C. Brisset, M. Sigovan, F. Chauveau, A. Riou, E. Devillard, V. Desestret, M. Touret, S. Nataf, J. Honnorat, E. Canet-Soulas, N. Nighoghossian, Y. Berthezene, M. Wiart, Quantification of Iron-Labeled Cells with Positive Contrast in Mouse Brains, Mol. Imaging Biol. 13 (2011) 672–678. doi:10.1007/s11307-010-0402-1. [17] M. Rogosnitzky, S. Branch, Gadolinium-based contrast agent toxicity: a review of known and proposed mechanisms, BioMetals. 29 (2016) 365–376. doi:10.1007/s10534-016-9931-7. [18] H. Wei, O.T. Bruns, M.G. Kaul, E.C. Hansen, M. Barch, A. Wiśniowska, O. Chen, Y. Chen, N. Li, S. Okada, J.M. Cordero, M. Heine, C.T. Farrar, D.M. Montana, G. Adam, H. Ittrich, A. Jasanoff, P. Nielsen, M.G. Bawendi, Exceedingly small iron oxide nanoparticles as positive MRI contrast agents, Proc. Natl. Acad. Sci. 114 (2017) 2325–2330. doi:10.1073/pnas.1620145114. [19] Y. Bao, J.A. Sherwood, Z. Sun, Magnetic iron oxide nanoparticles as T 1 contrast agents for magnetic resonance imaging, J. Mater. Chem. C. 6 (2018) 1280–1290. doi:10.1039/C7TC05854C.

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