abstract: In this work a newly fabricated organic solar cell based on a composite of fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) and regioregular poly (3-hexylthiophene) (P3HT) with an added interfacial layer of AgOx in between the PEDOT:PSS layer and the ITO layer is investigated. Previous equivalent circuit models are discussed and an equivalent circuit model is proposed for the fabricated device. Incorporation of the AgOx interfacial layer shows an increase in fill factor (by 33%) and power conversion efficiency (by 28%). Moreover proper correlation has been achieved between the experimental and simulated I-V plots. The simulation shows that device characteristics can be explained with accuracy by the proposed model. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

Proteins can often adsorb irreversibly at fluid/fluid interfaces; the understanding of the adsorption mechanism has relevance across a variety of industrial (e.g. the creation of stable emulsions) and biological (e.g. biofilm formation) processes. I performed molecular dynamics simulations of two surfactant proteins as they interact with air/water and oil/water interfaces, describing the origin of the surface activity, the adsorption dynamics and the conformational changes that these proteins undergo at the interface. BslA is an amphiphilic protein that forms a highly hydrophobic coat around B. subtilis biofilms, shielding the bacterial community from an external aqueous solution. By investigating the behaviour of BslA variants at oil/water interfaces via coarse-grained molecular dynamics, I show that BslA represents a biological example of an ellipsoidal Janus nanoparticle, whose surface interactions are controlled by a local conformational change. All-atom molecular dynamics simulations then reveal the details of the conformational change of the protein upon adsorption, and the self-assembly into a two-dimensional interfacial crystal. Ranaspumin-2 is one of the main components of the tungara frog foam nest. Contrary to most surfactant proteins, its structure lacks any sign of amphiphilicity. All-atom simulations show that the adsorption proceeds via a two-step mechanism where firstly the protein binds to the interface through its flexible N-terminal tail and then it undergoes a large conformational change in which the hydrophobic core becomes exposed to the oil phase. I then developed a simple structure-based coarse-grained model that highlights the same adsorption mechanism observed in all-atom simulations, and I used it to compare the dynamics of adsorption and the underlying free energy landscape of several mutants. These results agree with and are used to rationalise the observations from Langmuir trough and pendant drop experiments. Colloids can often be considered simpler versions of proteins that lack conformational changes. I performed coarse-grained simulations of the compression of interfacial monolayers formed by rod-like particles. These simulations show a rich behaviour characterised by the flipping of adsorbed rods, nematic ordering and bilayer formation. I report the series of transitions that take place as the rod aspect ratio is increased from 3 to 15.

Dans ce travail, nous avons étudié certains aspects fondamentaux (i) du mouillage, (ii) de germination aux interfaces réactives et au sein de la brasure et (iii) de la cinétique de croissance de couches intermétalliques au cours de l'assemblage par brasage en électronique (système Cu/liquide Sn).Le mouillage de Cu, Ag et de leurs composés avec Sn (Cu3Sn, Cu6Sn5 et Ag3Sn) par les brasures liquide Sn-Cu a été étudié par la technique de la goutte déposée dans un four à vide et suivi d'une caméra rapide. Dans la gamme de températures 300-6000C, la première étape de mouillage a lieu en moins de 10 ms et la vitesse d'étalement est d'environ 0.25 m.s-1. Au cours de cette étape (étalement non réactif) la cinétique d'étalement est pratiquement indépendante de T et similaire à celui non réactif du Pb liquide sur Cu. L'angle de contact d'équilibre de Sn liquide sur une surface non-réagi de Cu est inférieur à 300. Les angles de contact non réactifs sur Cu3Sn, atteints en moins de 10 ms, diminuent de 23 à 100 lorsque T augmente de 300 à 5000C. Au cours du mouillage sur Cu6Sn5 à 3900C, de faibles angles de contact (200) sont atteints en moins de 10 ms. Les résultats des expériences de mouillage sur Ag et Ag3Sn ont permis de proposer un mécanisme d'étalement en deux étapes: une première étape de mouillage non réactif très rapide et une seconde de mouillage réactif lente.En mettant en œuvre un dispositif expérimental d'immersion rapide et les techniques de TEM et SEM-FEG, nous avons réussi à étudier, pour la première fois, la séquence de formation des intermétalliques à l'interface Cu/alliage liquide au début de la réaction (1 ms à 1 s) à 2500C. Ces expériences donnent, pour la première fois, la réponse à une des questions les plus ouvertes et intéressantes concernant le brasage en électronique: la première phase qui se forme à l'interface Cu/Sn liquide est Cu6Sn5. Ensuite, nous avons développé une approche théorique sur les critères de suppression de la seconde phase (Cu3Sn) en supposant que Cu6Sn5 est la première qui se développe à l'interface sous forme d'une couche continue. Par ailleurs une modélisation théorique des étapes antérieures, lorsque la germination d'un embryon isolé de Cu3Sn se développe, est proposé.La cristallisation de l'alliage eutectique Sn-Cu a été étudiée par DSC en appliquant des cycles thermiques de fusion complète et partielle. Différentes catégories de degrés de surfusion ont été obtenues. En particulier, des degrés de surfusion faibles (1-7K) ont été détectés pour la première fois dans le cas de la fusion partielle. Une approche théorique sur la nucléation hétérogène est développée et les sites responsables de la germination ont été proposés.La comparaison directe de la cinétique de croissance dans le couple standard Cu/Sn liquide et celui incrémental Cu3Sn5/Sn liquide nous a permis de proposer un mécanisme de croissance de Cu6Sn à l'interface de Cu/Sn liquide. Les résultats obtenus sont compatibles avec le modèle FDR.Des expériences spécifiques de réactions interfaciales entre Cu et l'alliage liquide métastable Sn-0.7wt.%Cu à 2220C et pour des temps de réaction aussi long que 32 h ont été effectuées pour la première fois. Ceci est réalisé par des expériences spécifiques de DSC afin de contrôler l'état physique de l'alliage et la température. La comparaison directe des cinétiques de croissance et de la morphologie des couches réactionnelles formées entre les couples Cu/liquide et Cu/solide, à la même température, a conduit à la conclusion suivante: la grande différence de cinétique de croissance est due à la diffusion à l'état liquide par l'intermédiaire des canaux liquide de largeur nanométrique formés entre les joints de grains de Cu6Sn5 et/ou par des canaux cylindriques de rayon de quelques dizaines de nm formées aux joints triples des grains de Cu6Sn5. Une évaluation théorique de la largeur de ces canaux est effectuée pour la première fois et son évaluation est cohérente avec le modèle FDR. / In this work we have studied some fundamental aspects of (i) wetting, (ii) nucleation at reactive interfaces as well as inside the solder bulk and (iii) growth kinetics of intermetallic layers during a soldering process in electronic industry (Cu/liquid Sn system).Wetting of metallic substrates Cu, Ag and their intermetallics with Sn (Cu3Sn, Cu6Sn5 and Ag3Sn) by liquid Sn-Cu solders was studied by the dispensed drop technique in a high-vacuum furnace and using a rapid camera for recording the spreading process. In temperature range 300-600C, the first stage of wetting of Cu by liquid alloy occurs in less than 10ms and the spreading rate is about 0.25 m.s-1. During this stage (non reactive spreading) the spreading kinetics is practically temperature independent and similar to that of the non-reactive liquid Pb on Cu. The equilibrium contact angle of liquid Sn on a non-reacted and clean surface of Cu is lower than 300. The non-reactive contact angles on Cu3Sn, attained in less than 10 ms, decrease from 23 to 100 when T increases from 300 to 500C. During wetting of Cu6Sn5 at 390C, low contact angle of about 20 are attained in less than 10 ms. Results of wetting experiments of Ag and Ag3Sn substrates allowed to propose a mechanism of the spreading kinetics in two stages: a very rapid non reactive wetting and a slow reactive wetting stage.By implementing a fast dipping experimental set-up and SEM-FEG and TEM techniques, we succeed to study for the first time the sequence of formation of intermetallics at the Cu/liquid alloy interface at the very beginning of reaction (1 ms to 1 s) at 250C. These experiments give, for the first time, the answer to one of the most challenging questions in soldering: the first phase that appears at Cu/liquid Sn interface is the Cu6Sn5 phase. Afterwards, we developed a theoretical approach on the suppression criteria of the second phase formation (Cu3Sn) by assuming that Cu6Sn5 is the first phase that grows at the interface in form of a continuous layer. Moreover, a theoretical modeling of even earlier stages of the isolated nucleus of Cu3Sn phase nucleation is developed.Crystallization of eutectic Sn-Cu alloy was studied by performing specific DSC experiment by applying thermal cycles of complete and partial melting of the solder. Different categories of the undercooling degrees are obtained. In particular, low undercooling degrees (1-7K) are detected for the first time in the case of partial melting. A theoretical approach on heterogeneous nucleation is developed and the responsible sites of nucleation in the case of low undercooling degrees are proposed.Direct comparison of Cu6Sn5 growth kinetics in standard Cu/liquid Sn and in incremental Cu3Sn/liquid Sn couple gave a link with the operating mechanism of the Cu6Sn5 phase growth at solid Cu/liquid Sn interface. The obtained results are also consistent with the FDR model.Specific experiments dealing with interfacial reactions between Cu substrate and metastable liquid Sn-0.7wt.%Cu alloy at 222°C for reaction times as long as 32 h were performed for the first time. This is achieved by performing specific DSC experiments in order to monitor and control the physical state of the alloy as well as to set the accurate reaction temperature. Direct comparison of Cu/liquid and Cu/solid solder growth reaction kinetics and layer morphology at the same temperature lead to the conclusion that the large difference in the growth kinetics between the two couples can be explained if the growth occurs by the liquid state diffusion via the liquid channels of nanometric width formed between grain boundaries of Cu6Sn5 phase and/or by cylindrical channels of radius of some tens of nanometers formed at the triple line junctions of Cu6Sn5 scallops. A theoretical evaluation of the liquid channel width is performed for the first time. Evaluation is consistent with the FDR model.

Made available in DSpace on 2016-06-02T19:09:58Z (GMT). No. of bitstreams: 1 TeseENI.pdf: 5287790 bytes, checksum: c30a5b5cc0b140789ff3816da6250c1e (MD5) Previous issue date: 2006-09-22 / Financiadora de Estudos e Projetos / This work was motivated by the need of a better understanding of the microrheological characteristics of polybutylene terephthalate, PBT, polymer blends, such as the matrix phase PBT and the styrene-acrylonitrile, SAN copolymer as dispersed phase. The main purpose of the microrheological studies carried out was to analyze the rheological behavior and the morphology, as well as their correlation, in the preparation of the PBT/SAN immiscible blend, with and without the use of an interfacial compatibilizer. The rheological behavior was analyzed by torque rheometry, rotational rheometry with parallelplates geometry, and capillary rheometry. The interfacial tensions were measured by the modified ellipsoidal drop retraction method, using an optical polarized light microscope coupled to a hot stage. Two complementary techniques were used in the morphological analyses: scanning electron microscopy (SEM) with tetrahydrofuran (THF) extraction of the dispersed phase, and transmission electron microscopy (TEM) with rutene tetroxide (RuO4) deposition in the dispersed phase. The interfacial tension between the PBT polymer and the SAN copolymer was found to increase as the molar mass of the PBT increased. The use of rotational rheometry with parallel plates at low shear rates allowed the increase in viscosity to be quantified as a function of the reaction of the polymeric macromolecules in the PBT/SAN blend compatibilized or not with the interfacial compatibilizer, the MMA-GMA-EA copolymer. Based on the morphological characterizations, an analysis was made of the fibril formation mechanisms, break up and coalescence of the particles of dispersed phase and their interactions with the addition of interfacial compatibilizers. The rotational rheometry at low shear rates proved to be extremely efficient in the analysis of blend compatibilization, which is usually analyzed by torque rheometry. It was checked that, at high shear rates, the viscosity ratio influenced the formation of more finely dispersed phases. / O motivo que levou à realização deste trabalho de doutorado consistiu na necessidade de um melhor entendimento das características microrreológicas de blendas poliméricas constituídas de poli(tereftalato de butileno), PBT, como fase matriz, e do copolímero estireno-acrilonitrila, SAN, como fase dispersa. Os estudos microrreológicos realizados tiveram como enfoque principal analisar o comportamento reológico e a morfologia, bem como suas correlações na preparação da blenda imiscível PBT/SAN, com e sem a utilização de um compatibilizante interfacial. Nas análises do comportamento reológico, foram utilizadas reometria de torque, reometria rotacional na geometria de placas paralelas e reometria capilar. As medidas de tensões interfaciais foram realizadas através do método de retração de gotas elipsoidais modificado, utilizando-se de um microscópio óptico com luz polarizada acoplado a um estágio a quente. Nas análises morfológicas, foram utilizadas duas técnicas complementares, através de microscopia eletrônica de varredura (MEV) com extração da fase dispersa com tetrahidrofurano (THF) e por microscopia eletrônica de transmissão (MET) com a deposição de tetróxido de rutênio (RuO4) sobre a fase dispersa. Utilizando-se do método de retração de gota modificado, verificou-se que a tensão interfacial entre o polímero PBT e o copolímero SAN aumenta com o aumento da massa molar do PBT. Utilizando-se da reometria de placas paralelas a baixas taxas de cisalhamento, foi possível quantificar o aumento de viscosidade em função da reação das macromoléculas poliméricas na blenda PBT/SAN, compatibilizada ou não com o agente de compatibilização interfacial (o terpolímero metacrilato de metilametacrilato de glicidila-acrilato de etila, MMA-GMA-EA). Por meio das caracterizações morfológicas, foi possível analisar os mecanismos de formação de fibrilas, cominuição e coalescência das partículas de fase dispersa e de suas interações com a adição de agentes de compatibilização interfacial. A técnica de reometria rotacional de placas paralelas em baixas taxas de cisalhamento mostrou-se extremamente eficiente na análise de compatibilização de blendas, que, na maioria das vezes, é feita através de reometria de torque. Verificou-se que, a altas taxas de cisalhamento, a razão de viscosidade influencia a formação de fases mais finamente dispersas em função da taxa de cisalhamento aplicada à blenda PBT/SAN.

Made available in DSpace on 2016-06-02T19:11:47Z (GMT). No. of bitstreams: 1 1263.pdf: 4842944 bytes, checksum: 847b9ce01a383be03465220269170c48 (MD5) Previous issue date: 2006-09-06 / Financiadora de Estudos e Projetos / Although the influence of interfacial adhesion on short-term mechanical performance of fiber-reinforced thermoplastic composites has been well established, very little published information is available on the influence of the composite interface/interphase characteristics on fatigue properties of these materials. Fatigue life determination is of paramount importance for engineering applications of injection moulded short glass fiber (GF) reinforced polypropylene (PP) composites. Thus, this work is related to an investigation on the influence of maleated polypropylene (PP-g-MAH) interfacial compatibilizer on the fatigue resistance properties of 30 percent GF-reinforced PP composites. The mechanical fatigue analysis was carried out using four-point bending tests under deformation controlled mode at frequencies of 1 Hz and complete reverse cycle (R = - 1). In order to obtain quick comparative data on PP-g-MAH compatibilizer performance on the fatigue life of these composites, an experimental procedure was elaborated in order to correlate the properties determined by dynamicmechanical thermal analysis (DMTA) of composite samples, both pristine or subjected to short-term cyclic loading, with the experimentally determined fatigue life of these materials. The main conclusions of this work indicate that the mechanical damping (tan d) values, related to the fiber-polymer interfacial friction, reduce with compatibilizer content; this effect being better evidenced in the fatigued samples. The decrease in tan d values with compatibilizer content clearly indicate an increase in the composite interfacial compatibility and were found to be inversely proportional to the number of cycles to failure determined by long-term fatigue testing, thus, promoting an increase in the fatigue life of the investigated PP/PP-g-MAH/30%GF composites. / Apesar de já ser conhecida a influência da adesão interfacial no desempenho mecânico de curta duração dos compósitos termoplásticos, pouco se sabe sobre a influência da natureza da interface/interfase fibra-polímero na resistência à fadiga destes materiais. Esta propriedade de longa duração é de suma importância em aplicações de engenharia, onde os compósitos moldados por injeção de polipropileno (PP) reforçado com fibra de vidro curta (FV) começam a encontrar grande relevância e atuação, em função de desempenho superior alcançado com uso de compatibilizantes interfaciais. Assim, neste trabalho, buscou-se investigar a influência da adição do compatibilizante interfacial de PP funcionalizado com anidrido maleico (PP-g-MAH) no comportamento mecânico sob fadiga cíclica em compósitos de PP reforçado com 30% em peso de FV. Os ensaios de fadiga foram realizados em flexão quatro-pontos sob deformação controlada na freqüência de 1 Hz e ciclo completo reverso com tensão média zero. Com o objetivo de obter rapidamente informações indicativas sobre a influência do teor de PP-g-MAH na durabilidade sob fadiga mecânica destes compósitos, apresenta-se neste trabalho uma metodologia experimental que busca correlacionar as propriedades obtidas por análise térmica dinâmicomecânica (DMTA) dos compósitos, sem e com envelhecimento por curto tempo sob fadiga, com o experimentalmente determinado desempenho sob fadiga mecânica destes materiais. A principal conclusão deste trabalho demonstra que a propriedade de amortecimento mecânico (tan d), associado ao atrito interfacial do compósito, diminui com aumento no teor do compatibilizante de PP-g-MAH incorporado, sendo este efeito melhor evidenciado nos compósitos pré-envelhecidos sob fadiga. Esta redução no valor de tan d do compósito indica claramente um aumento no grau de compatibilização interfacial fibrapolímero e reflete de forma coerente e inversamente proporcional ao número de ciclos até falha verificada nos ensaios de longa duração sob fadiga mecânica, proporcionando um aumento na durabilidade dos compósitos de PP em análise.

Made available in DSpace on 2016-06-02T19:12:21Z (GMT). No. of bitstreams: 1 4507.pdf: 8368845 bytes, checksum: c2fbca7be58a49b0033b38e3d5a4fc89 (MD5) Previous issue date: 2010-05-17 / Financiadora de Estudos e Projetos / Talc is a well known lamellar mineral filler much used for mechanical reinforcement of polypropylene (PP) composites. Mineral nanoclay is also a lamellar filler that is gaining much interest due to its reinforcement effect achieved at relatively much reduced filler content. So the main objectives of this work were to establish a comparative study on the mechanical fatigue properties of isotactic PP composites reinforced with both types of fillers: nanocomposites with 2 and 5 wt. % of organophilic nanoclay and microcomposites with 8 and 25 wt.% of ultrafine talc, where the influence of distinct filler particles size and different filler-matrix interfacial interactions were analyzed on the fatigue life and strength properties of these materials with potential engineering applications. All composites were subjected to short-term tensile and Izod impact tests, dynamic-mechanical thermal analysis and microstructural characterization via SEM and TEM, in order to correlate the analyzed characteristics to the fatigue behavior of the materials. The fatigue tests were carried out under stress controlled mode in tensile tension-tension, with a sinusoidal stress input at 1 Hz frequency and R = 0.1. Maleated PP contributed to the enhancement of short-term mechanical properties of talc-filled composites, whilst its influence was much reduced on the same properties of OMMT nanocomposites, due to the modest nanoclay exfoliation achieved in the non-polar PP polymer matrix. In general terms, talc-filled PP microcomposites showed better fatigue performance in comparison to the nanocomposites with O-MMT. However, their Wöhler fatigue S-N curves did not indicate fatigue endurance limits, within the fatigue span of up to 1 x 106 cycles. The main conclusion derived from this study, indicated that when both types of composites exhibited equivalent elastic modulus enhancement, the stronger filler-polymer interfacial interactions present in the talc-filled microcomposites prevailed over the reduced filler particles size of the nanocomposites of O-MMT, however with presence of nanoparticles agglomerates. / O talco é uma carga mineral lamelar conhecida e bastante usada em compósitos de polipropileno (PP), por elevar a eficiência de reforço mecânico do polímero. Por outro lado, o interesse pela nanoargila, também carga mineral lamelar, vem crescendo por esta aprimorar as propriedades do polímero, com uso do nanoreforço em teores muito mais reduzidos em comparação ao dos compósitos tradicionais. Com isso, buscou-se neste trabalho fazer uma análise comparativa do comportamento de fadiga sob ciclagem mecânica de dois tipos de compósitos de i-PP homopolímero: nanocompósitos com 2 e 5% de nanoargila organofílica (O-MMT) e microcompósitos com 8 e 25% de talco ultrafino. O objetivo foi analisar a influência do tamanho das partículas do reforço e do grau de interação interfacial matriz-reforço nas propriedades de resistência e durabilidade mecânica sob fadiga destes compósitos. Todos os compósitos empregaram o PP maleado (PP-g-MAH) como compatibilizante interfacial e foram processados numa extrusora dupla-rosca e moldados por injeção. Os ensaios de fadiga foram realizados em corpos de prova de tração no modo de tensão controlada, com uma onda senoidal na freqüência de 1 Hz e R = 0,1. Foram também realizados os ensaios estáticos de tração e resistência ao impacto, microscopia eletrônica (MEV e MET) e análise térmica dinâmico-mecânica (DMTA). De forma geral, os microcompósitos de PP com 8 e 25% de talco apresentaram desempenho sob fadiga superior em relação aos nanocompósitos de O-MMT; entretanto, sem alcançar valores de tensão limite de enduro dentro do intervalo de duração dos ensaios de até 1 x 106 ciclos. A principal conclusão neste estudo demonstrou que na definição da resistência à fadiga dos dois tipos de compósitos de PP com módulo elástico equivalentes, as fortes interações polimero-reforço presentes nos microcompósitos de PP/talco, tal como identificadas por análise DMTA, prevaleceram sobre o tamanho reduzido das nanopartículas de O-MMT, porém com presença de aglomerados.

Made available in DSpace on 2016-06-02T19:12:24Z (GMT). No. of bitstreams: 1 4659.pdf: 3782907 bytes, checksum: e060d8da34ca505a42f2b053b8782c03 (MD5) Previous issue date: 2010-05-21 / Financiadora de Estudos e Projetos / In short glass fiber (GF) reinforced polypropylene (PP) composites, despite of the chemically inert and non-polar nature of the matrix, the fiber-matrix interfacial integrity may be compromised in a hygrothermal active environment by the addition of maleic anhydride (MAH) molecules of the interfacial compatibilizer (PP-g-MAH). The use of organophilic nanoclay particles (O-MMT, Cloisite 20A) could contribute to minimize this hygrothermal deterioration, due to its moisture barrier properties. So, the main goal of this study was to analyze the influence of O-MMT on the long-term mechanical performance of PP/PP-g-MAH/GF composites under hygrothermal ageing. Several PP composite formulations with constant GF content (40wt%) and varying concentrations of nanoclay (0.5; 1; 2; and 5wt%) were compounded in a corotating twin-screw extruder. The degree of nanoclay particles intercalation/exfoliation was characterized by X-ray diffraction (WAXD) and SEM/TEM microscopy analysis. Short-term mechanical characterization was carried out through standard tensile and Izod impact tests on injection moulded specimen. From this results, certain specimen were subjected to hygrothermal ageing in hot water at 80 ºC for 240/480/720 hours and the evolution of the hygrothermal deterioration was monitored by tensile tests. The increasing O-MMT content in unaged PP/PP-g-MAH/40%GF composites had an unexpected negative influence on short-term mechanical properties. Mechanical damping data indicated higher Tan  values for the ternary composite (PP/PP-g-MAH/40%GF/2%O-MMT), in comparison to the binary composite (PP/PP-g-MAH/40%FV), demonstrating deleterious effect of O-MMT on the fiber-polymer interfacial adhesion. SEM microscopy analysis of cryofractured surfaces were decisive for visual elucidation of the erosive action of O-MMT particles on the GF sizing treatment. Consequently, the relative tensile strength (TS) of the hygrothermally aged composite, with respect to that of the unaged composite (TSenv./TSn-env.), indicated that the addition of nanoclay in the ternary composite contributed to a higher deterioration of the long-term mechanical performance of GF-reinforced PP composites. / A durabilidade mecânica de compósitos poliméricos requer a preservação da integridade interfacial fibra-polímero contra a ação do ambiente agressivo. Em compósitos de polipropileno (PP) reforçado com fibra de vidro (FV) curta, apesar da natureza apolar da matriz, esta integridade poderá ser comprometida na presença de calor e umidade, devido à introdução de grupos polares de anidrido maleico do compatibilizante interfacial de PP maleado (PP-g-MAH), conduzindo ao desacoplamento interfacial e a rápida deterioração das propriedades mecânicas do compósito. A introdução de nanoargila organofílica de Montmorilonita (O-MMT, Cloisite 20A) poderá contribuir para redução desta deterioração termohidrolítica do compósito, em função das suas características de barreira à permeação de água. Portanto, é objetivo principal deste estudo avaliar a influência da introdução da nanoargila na durabilidade mecânica sob envelhecimento higrotérmico de compósitos de PP/PP-g-MAH/FV. Diversas formulações de compósitos de PP com teor constante de FV (40% em massa) e teores variados de nanoargila (0,5; 1; 2; e 5% em peso) e de PP-g-MAH foram preparados numa extrusora dupla-rosca corrotacional. O grau de intercalação/esfoliação da nanoargila em PP/PP-g-MAH foi avaliado por difração de raios-X (WAXD) e análise microestrutural por MEV e MET. Destes compósitos, algumas formulações de melhor desempenho mecânico foram submetidas ao envelhecimento higrotérmico em água deionizada a 80°C. A introdução de O-MMT nos compósitos de PP/PP-g-MAH/40%FV apresentou um efeito deletério inesperado nas propriedades mecânicas de curta duração em função do teor crescente de O-MMT. Dados de amortecimento mecânico (Tan ) indicaram o efeito deletério da O-MMT no grau de adesão interfacial no compósito ternário (PP/PP-g-MAH/40%FV/2%O-MMT), em relação ao compósito binário (PP/PP-g-MAH/40%FV). Análise de superfícies criofraturadas dos compósitos por MEV indica a ação abrasiva da O-MMT no recobrimento da FV. A resistência à tração sob envelhecimento higrotérmico, relativizada pela do material não envelhecido, indica que a presença da nanoargila contribuiu para um grau maior de deterioração destes compósitos de PP com reforço híbrido de FV/O-MMT.

Made available in DSpace on 2016-06-02T19:12:29Z (GMT). No. of bitstreams: 1 5163.pdf: 11516846 bytes, checksum: 03f054efca1b0f8ca8ec44ede8d31fad (MD5) Previous issue date: 2012-04-11 / Universidade Federal de Sao Carlos / Thermoplastic composites reinforced with short glass fibers, to be used in technical engineering applications, usually requires a good balance of properties, such as strength and tenacity. For the case of the composite of polypropylene reinforced with glass fibers, which presents a superior cost/mechanical performance when compared to other composites with matrices like polyamide and polyesters, high mechanical performance can only be achieved by an increase in fiber-polymer interfacial interaction, which is low due to the non-polar character of the PP matrix. This problem was solved by the adequate use of aminosilane coupling agent combined with an interfacial compatibilizer and its ideal content, which defines the balance between properties like strength and tenacity, still is a matter that needs further investigation. Therefore, the main goal of the present work was to evaluate the influence of maleated PP (PP-g-MAH) compatibilizer on short therm mechanical properties (tensile, flexural and impact strength) and on mechanical fracture mechanism, through the analysis of essential work of fracture (EWF), in composites of PP reinforced with equivalent fiber contents (30% in weight in the composite) of two types of glass fibers with different sizings, one compatible with matrices consisting of PP (GF968) and the other compatible with polar matrices such as polyamides (GF983). The tensile, flexural and impact strength analysis along with SEM microscopy, showed that the failure in these composites is due to achieving the maximum shear strength of the interface between the matrix and the PP-co-siloxane copolymer interphase. The results of EWF showed that the main contribution to the process of deforming energy dissipation it s attributed to the specific essential work of fracture (we), during the creation of new surfaces, associated to the mechanism of decoupling, pullout and fiber-polymer interface/interphase deformation. / Compósitos de termoplásticos reforçados com fibras de vidro curtas (TPRFVc), empregados em aplicações técnicas de engenharia, normalmente requerem um bom balanço de propriedades de rigidez, resistência e tenacidade. Para o caso do compósito de polipropileno reforçado com fibras de vidro curtas (PP/FV) o qual apresenta uma relação custo/desempenho mecânico superior em relação a outros compósitos de matrizes tais como poliamidas e poliésteres, alto desempenho mecânico só pôde ser assegurado a partir de um aumento da interação interfacial fibra-polímero que é baixa devido ao caráter apolar da matriz de PP. Este problema foi resolvido através do uso de adequado agente de acoplagem aminosilano combinado com um compatibilizante interfacial e, seu teor ideal, que define o equilíbrio das propriedades de rigidez e tenacidade, ainda é um tema que carece de investigação. Sendo assim, o principal objetivo deste trabalho foi o de avaliar a influência do teor do compatibilizante de PP maleado (PP-g-MAH) em propriedades mecânicas de curta duração (resistência à tração, flexão e impacto) e no mecanismo de fratura mecânica, através da análise de trabalho essencial de fratura (EWF), em compósitos de PP reforçado com teores equivalentes (30% em peso) de dois tipos de FV curta pré-tratada com encimagens distintas; uma compatível com matrizes de PP (FV968) e outra compatível com matrizes polares de poliamidas (FV983). A análise de propriedades de resistência à tração, flexão e ao impacto conjuntamente com microscopia MEV mostrou que a falha nestes compósitos se deve ao alcance da máxima resistência ao cisalhamento na interface matriz-interfase de copolímero de PP-co-siloxano. Os resultados da técnica de EWF indicam que a principal contribuição ao processo de dissipação de energia deformacional é atribuída ao trabalho essencial de fratura específico (we), durante a criação de novas superfícies, associado aos mecanismos de desacoplamento e arrancamento das fibras e de deformação da interface/interfase fibra-polímero.

O processo de absorção do CO2 em soluções aquosas de alcanolaminas foi estudado em uma coluna de parede molhada empregando-se uma tela metálica, de 28 mesh, como promotor de película e operando em contracorrente. As alcanolaminas testadas nos diferentes experimentos foram: monoetanolamina (MEA), 2-amino-2-metil-1-propanol (AMP) e piperazina (PZ). Os experimentos de absorção foram realizados nas soluções aquosas individuais da MEA e AMP; e, nas misturas MEA:AMP e AMP:PZ; visando avaliar a velocidade de absorção do CO2 em diferentes vazões do líquido, a saber: 3.10-7, 6.10-7 e 10.10-7 m3/s. O presente sistema de absorção foi caracterizado através da determinação dos principais parâmetros de transferência de massa: área interfacial efetiva, coeficiente de transferência individual da fase gasosa e o coeficiente volumétrico global médio de transferência de massa. Determinou-se a área interfacial efetiva da coluna, por meio da absorção do CO2 diluído em ar em uma solução aquosa de NaOH, para as diferentes vazões de líquido, sendo os resultados obtidos igual a 106, 126 e 144 m2/m3, respectivamente. O coeficiente volumétrico de transferência de massa da fase gasosa foi determinado por meio da absorção de SO2 diluído em ar em uma solução aquosa de NaOH. Os resultados experimentais mostram que o coeficiente volumétrico individual de transferência de massa e a área interfacial são função da vazão do líquido. As velocidades de absorção do CO2 diluído em ar, em soluções de aminas e suas misturas foram determinadas experimentalmente para diferentes vazões de líquido, sendo os resultados expressos na forma de coeficientes globais de transferência de massa e parâmetros cinético-difusivos da fase líquida. As velocidades de absorção em MEA são bem superiores aos de AMP e NaOH. No caso das misturas foram obtidas velocidades superiores em comparação às das aminas individuais. A velocidade de absorção em AMP é fortemente incrementada na presença de PZ, mesmo em baixa concentração. / The CO2 absorption process in alkanolamine aqueous solutions was studied in a wetted wall column employing a film promotor of thin stainless steel woven wire, 28 mesh, which was operated in countercurrent. The tested alkanolamines were monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ). The absorption experiments were performed in individual aqueous solutions of MEA and AMP and the mixtures MEA:AMP and AMP:PZ, with the aim of evaluating the CO2 absorption rate in different liquid flow rates, namely: 3.10-7, 6.10-7 e 10.10-7 m3/s. This absorption system was characterized through determining of the main parameters of mass transfer: effective interfacial area, individual mass transfer coefficient of the gas phase and the average overall mass transfer volumetric coefficient. The effective interfacial area was determined by the absorption of CO2 diluted in air into an aqueous solution of NaOH for the different liquid flow rates, and the results obtained are 106, 126 and 144 m2/m3, respectively. The mass transfer volumetric coefficient of the gas phase was determined by chemical method of the absorption of SO2 diluted in air into an aqueous solution of NaOH. The experimental results show that the individual mass transfer coefficient and interfacial area are a function of liquid flow rate. On the other hand, the results of the performance of CO2 absorption into amine aqueous solutions were expressed in function of the average overall mass transfer volumetric coefficient and liquid phase diffusive kinetic parameters, which were measured experimentally for different liquid flow rates. The absorption rate in MEA are higher in comparison with AMP and NaOH. In the case of the blended, the absorption rate in AMP is enhanced by piperazine, even in low concentration.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-04-18T20:31:20Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - André A. Ferreira.pdf: 2947466 bytes, checksum: 12ba46e44f7b04ea33d92b029b5a85f7 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-04-18T20:31:36Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - André A. Ferreira.pdf: 2947466 bytes, checksum: 12ba46e44f7b04ea33d92b029b5a85f7 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-04-18T20:31:55Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - André A. Ferreira.pdf: 2947466 bytes, checksum: 12ba46e44f7b04ea33d92b029b5a85f7 (MD5) / Made available in DSpace on 2017-04-18T20:31:55Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - André A. Ferreira.pdf: 2947466 bytes, checksum: 12ba46e44f7b04ea33d92b029b5a85f7 (MD5) Previous issue date: 2017-03-17 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this paper is to analyze the structure and morphology of Polyaniline Emeraldine-salt form (PANI-ES) by conventional (PANI-ES/C1 and PANI-ES/C2) and interfacial (PANI-ES/I1 and PANI/ES/I2) polymerization using HCl 1M and 2M. The X-ray diffraction patterns (XRD) of PANI-ES/I1 and PANI-ES/I2 have presented higher crystallinity. Furthermore, the peak located at 2θ = 18.3° has not been reported in scientific literature. PANI–ES/C1 and PANI–ES/C2 presented closed crystallinity percentage around 50 (± 2) %, while PANI–ES/I1 and PANI-ES/I2 presented, respectively, 55 (± 2) % and 63 (± 2) % of crystallinity. PANI–ES/C1 showed cell parameters similar to those reported in literature. However, PANI–ES/C2, PANI–ES/I1 and PANI–ES/I2 have presented larger “b” unit cell parameter, from 8.9021 Å (PANI–ES/C1) to ~16.2931 Å, due to the more efficient doping of the chloride ions. Fourier-transform Infrared Spectroscopy technique (FTIR) was useful to evaluate significant changes in the quinoid (Q) and benzenoid (B) bands: PANI-ES/C1 and PANI-ES/C2 presented the ratio Q/B, respectively, 0.4 and 0.6, indicating that the doping level by exposure to a higher dopant concentration has increased. An even more intense dopant action was verified in PANI-ES/I1 and PANI-ES/I2, presenting Q/B ratios of 0.7 and 0.9, respectively. These results reveal the more efficient doping level provided by the interfacial polymerization. Scanning Electron Microscopy (SEM) images showed that PANI-ES/C1 presented short nanofibers, while PANI-ES/C2 showed nanofibers length and diameter, respectively, around 61% and 13% higher than those found in PANI-ES/C1. However, PANI-ES/I1 and PANI-ES/I2 presented four different types of morphologies (nanoplates, nanorods, nanofibers and nanoflowers) due to the peculiarity of this polymerization method as well as to the lower dopant concentration. The difference of length and diameter between PANI-ES/C1 and PANI-ES/I2 nanofibers reaches 64% and 52%, respectively. Thermogravimetric Analysis (TGA) showed that the event related to the dopant release occurred for PANI-ES/I1 and PANI-ES/I2 in higher temperatures and larger temperature range, suggesting larger amount of dopant and better doping level. In addition, PANI-ES/C1 was the lesser stable sample, while the more stable sample was PANI-ES/I2. The PANI-ES/C1 presented the lowest electrical conductivity, 0.48 x 10-4 S.cm-1. Thus, PANI-ES/C2, PANI-ES/I1 and PANI-ES/I2 have presented, respectively, electrical conductivity values around 0.75 x 10-4 S.cm-1, 0.90 x 10-4 S.cm-1 and 1.20 x 10-4 S.cm-1. Furthermore, the interfacial polymerization methodology may favored higher electrical conductivity due to the better charge transport along the larger nanofibers. / O objetivo deste trabalho é analisar estrutura e morfologia de polianilinas na forma Sal de Esmeraldina (PANI-ES) obtidas por síntese convencional (PANI-ES/C1 e PANI-ES/C2) e interfacial (PANI-ES/I1 e PANI-ES/I2) usando 1 e 2M de HCl. Os padrões de difração de raios X (DRX) das PANI-ES/I1 e PANI-ES/I2 apresentaram maiores cristalinidades (55 ± 2 e 63 ± 2%) enquanto PANI-ES/C1 e PANI-ES/C2 apresentaram cristalinidade em torno de 50 ± 2%. PANI-ES/C1 apresentou parâmetros de cela unitária semelhantes aos relatados na literatura. No entanto, PANI-ES/C2, PANI-ES/I1 e PANI-ES/I2 apresentaram maior valor do parâmetro de célula unitária “b”, que passou de 8.9021 para 16.2931 Å, devido à dopagem mais eficiente pelos íons cloreto. A técnica de Infravermelho com Transformada de Fourier (FTIR) foi útil para avaliar as alterações nas bandas quinóide (Q) e benzenóide (B): PANI-ES/C1 e PANI-ES/C2 apresentaram a razão Q/B = 0,6, indicando que o nível de dopagem por exposição a uma concentração de dopante mais elevada aumentou. Verificou-se uma ação dopante ainda mais intensa em PANI-ES/I1 e PANI-ES/I2 apresentando razões Q/B de 0,7 e 0,9, respectivamente. Estes resultados revelam o nível de dopagem mais eficiente proporcionado pela polimerização interfacial. As imagens de Microscopia Eletrônica de Varredura (MEV) mostraram que PANI-ES/C1 apresentou nanofibras curtas, enquanto que PANI-ES/C2 apresentou comprimento e diâmetro de nanofibras respectivamente, cerca de 61 e 13% superiores aos encontrados para a PANI-ES/C1. No entanto, PANI-ES/I1 e PANI-ES/I2 apresentaram quatro tipos diferentes morfologias (nanoplacas, nanobastões, nanofibras e nanoflores) devido à peculiaridade deste método de polimerização. A diferença de comprimento e diâmetro entre as nanofibras de PANI-ES/C1e PANI-ES/I2 atingiu 64 e 52%, respectivamente. A análise termogravimétrica (TGA) mostrou que o evento relacionado à liberação de dopante ocorreu para PANI-ES/I1 e PANI-ES/I2 em temperaturas mais elevadas e maior faixa de temperatura, sugerindo maior quantidade de dopante e melhor nível de dopagem. Além disso, PANI-ES/C1e foi a amostra menos estável, enquanto que a amostra mais estável foi PANI-ES/I2. A PANI-ES/C1 apresentou a menor condutividade elétrica, 0,48 x 10-4 S.cm-1. PANI-ES/C2, PANI-ES/I1 e PANI-ES/I2 apresentaram, respectivamente, valores de condutividade elétrica em torno de 0,75 x 10-4 S.cm-1, 0,90 x 10-4 S.cm-1 e 1,20 x 10-4 S.cm-1, as quais podem ter sido favorecidas pelo método de polimerização devido ao melhor transporte de carga ao longo das nanofibras e também às diferentes morfologias.