Ce travail de thèse a pour objectif d’élaborer de nouveaux revêtements composites en utilisant les nanocristaux de cellulose (NCC) comme additifs biosourcés. Pour pallier au problème d’incompatibilité entre les charges hydrophiles et les matrices hydrophobes, une méthode simple à partir des esters de vinyle a été développée pour fonctionnaliser la surface des NCC. Une étude préliminaire réalisée à partir de l’acétate de vinyle utilisé comme réactif modèle, a d’abord permis d’optimiser les conditions de réaction. Ce protocole expérimental a ensuite été étendu à d’autres esters de vinyle fonctionnels, confirmant le caractère polyvalent de la méthode. Les NCC non modifiés et acétylés ont été dispersés dans des matrices acryliques (latex) ou polyuréthane (réticulable), afin d’étudier leur impact sur les performances mécaniques et barrières des composites. Une amélioration des propriétés mécaniques et barrières à l’oxygène a pu être observée dans certains cas, mais l’acétylation de surface des NCC n’a pas conduit à de meilleures performances. Une solution bicouches constituée d’un film 100 % NCC acétyles recouvert de polymère a alors été envisagé et a d’augmenter fortement les propriétés barrières à l’oxygène des différents matériaux. Certains NCC fonctionnalisés ont également été dispersés dans une matrice polydiméthylsiloxane, potentiellement utilisable comme revêtement protecteur pour l’aérospatial. Une amélioration notable de la stabilité thermique et optique sous irradiations UV dans des conditions géostationnaires a alors été observée. / The objective of this research work consist in the elaboration of novel compositecoatings using cellulose nanocrystals (CNC) as biobased additives. To palliate the problem ofincompatibility between the hydrophilic filler and the hydrophobic matrices, a simple methodbased on vinyl esters was developed to functionalize the CNC surface. A preliminary studyperformed with vinyl acetate selected as model reactant first allowed optimizing the reactionconditions. This experimental protocol was subsequently extended to other functional vinylesters to confirm the versatility of the method. The unmodified and acetylated CNC weredispersed in acrylic polymers (latex) or polyurethane (cross-linked resin) matrices, to studytheir impact on the mechanical and barrier performances of the composites. An improvementof the mechanical and barrier properties could be observed in some cases, but the CNCacetylation did not improve further the performances. A bi-layer approach consisting in afilm of 100 % of acetylated CNC coated with the polymer was then envisaged, and allowedincreasing significantly the oxygen barrier properties of the different resins. Some of thefunctionalized CNC were incorporated into a polydimethylsiloxane matrix, for a potential useas protective aerospace coating. A significant improvement in thermal stability and in opticalstability under UV irradiation in geostationary conditions was then observed.

Le graphène est un matériau prometteur pour de nombreuses applications du fait de ses propriétés exceptionnelles. Cependant, à la fois les propriétés et les rendements des graphènes et dérivés sont très variables et dépendants de la méthode de production utilisée. De ce fait, la méthode de production doit être développée en accord avec les besoins liés à l'application visée. Dans cette thèse, différents nanomatériaux dérivés du graphène ont été préparés en employant deux méthodes différentes, l'exfoliation en milieu liquide et la synthèse directe par dépôt chimique catalytique en phase vapeur (CVD), et une compréhension fondamentale sur la production de graphène a été acquise. Ces deux méthodes sont prometteuses en termes de qualité, de possibilité de production à grande échelle, de cout de production et enfin d'applications des différents "graphènes" obtenus. D'une part, l'exfoliation en milieu liquide permet de produire des dérivés du graphène tels que le few-layer graphene (FLG (<5 feuillets)) à relativement grande échelle, pour des applications telles que les nanocomposites. Le défi principal consiste à augmenter la concentration en FLG autant que possible, tout en conservant une bonne qualité. De ce fait, une étude comparative de l'exfoliation dans l'alcool isopropylique de 3 poudres de graphite différentes a été entreprise. Des suspensions de FLG de concentration élevée (?1,1 mg/ml) ont été obtenues en partant de poudre de graphite de surface spécifique élevée, par sonication dans l'alcool isopropylique (cuve, 90 min). Ces nanoparticules ont ensuite été incorporées dans des nanocomposites à matrice alumine. Ainsi, nous avons préparé par frittage SPS des nanocomposites à matrice céramique possédant des propriétés mécaniques, thermiques et électriques anisotropes. D'autre part, des films de graphène alliant une grande surface, prometteurs pour des applications dans le domaine de l'électronique, ont été synthétisés par CVD basse pression sur des feuilles de Cu. L'influence de l'atmosphère pendant le traitement thermique et la nature du catalyseur sur le niveau d'impuretés, la qualité des films de graphène synthétisés et leur uniformité en termes de nombre de feuillets a été étudiée. Des films de graphène CVD de haute qualité (très peu de désordre de structure) ont été utilisés pour la réalisation de dispositifs. Ces derniers ont été caractérisés à température ambiante en mesurant leur résistance électrique en fonction de la tension grille ainsi que par des mesures de transport en régime d'effet Hall quantique (basse température et forts champs magnétiques - pulsés). Les résultats préliminaires obtenus confirment que du graphène mono-feuillet possédant une bonne mobilité électronique atteignant jusqu'à 46500 cm²/Vs à température ambiante a pu être synthétisé avec succès. / Graphene is a promising material for many applications due to its unique properties. However, properties and yield of graphene-based materials show variations depending on which production route is used. Therefore, an appropriate production method has to be preferred according to the requirements of a specific application. In this thesis study, graphene-based materials have been successfully produced by liquid phase exfoliation (LPE) and chemical vapor deposition (CVD), which are promising graphene production methods in terms of quality, scalability, cost and applicability of the produced material to relevant applications, and a fundamental understanding on graphene production has been developed. LPE route allows one to produce graphene-based materials at a large-scale for applications such as nanocomposites. The challenge of this method is to increase graphene concentration as much as possible while maintaining the quality of the graphene flakes. Therefore, a comparative study, at which three different graphite-based powders were investigated as starting materials for an effective exfoliation process in isopropyl alcohol (IPA), was performed. High concentration (?1.1 mg/ml), few-layer (?5 layers) graphene-based dispersions were prepared by sonication in IPA within 90 min by utilizing a high surface area graphite nano-powder. This graphene-based material was then incorporated into Al2O3 matrix nanocomposites as a reinforcing/filler phase. Ceramic matrix nanocomposites which exhibit anisotropic mechanical, thermal and electrical properties have been successfully prepared by spark plasma sintering. On the other hand, large-area graphene films, which are promising for electronic applications, were synthesized via low-pressure CVD method over Cu-foils. The influence of ramping atmosphere and Cu foil characteristics on the impurity level, quality of the synthesized graphene films and their thickness uniformity was investigated. High quality CVD-grown graphene films with a significantly reduced disorder level were used for device fabrication and characterized in terms of their electrical resistance at room temperature as a function of gate voltage and transport property measurements in Quantum Hall Effect (QHE) regime (at low temperature and high magnetic field) by pulsed magnetic field experiments. The preliminary results confirmed that single layer graphene with a relatively high electronic mobility reaching up to ?46500 cm2/Vs at room temperature was successfully produced.

Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers. Magnetite (Fe3O4) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of transverse external magnetic fields of up to 4.5 kOe. Experiments confirm strong magnetic field dependence across all samples. When incorporated in to a cavity resonator device, tangent losses were reduced, quality factor increased by 5.6 times, and tunability of the resonance frequency was demonstrated, regardless of NP-loading. Work on PNC materials revealed the importance of NP interactions in confined spaces and motivated the study of confinement effects of magnetic NPs in more controlled environments, such as MWCNTs with varying diameters. MWCNTs were synthesized with diameters of 60 nm, 100 nm, 250 nm, and 450 nm to contain magnetic NP fillers (~10 nm) consisting of ferrites of the form MFe2O4, where M = Co2+, Ni2+, or Fe2+. All confined samples exhibit superparamagnetic-like behavior with stronger magnetic response with respect to increasing MWCNT diameter up to 250 nm due to the enhancement of interparticle interactions. This thesis provides the first systematic study of this class of nanocomposites, which paves the way to inclusion of novel nanostructured materials in real-world applications.

High voltage rotating machines play a significant role in generation and use of electrical energy as the demand for power continues to increase. However, one of the main causes for down times in high voltage rotating machines is related to problems with the winding insulation. The utilities want to reduce costs through longer maintenance intervals and a higher lifetime of the machines. These demands create a challenge for the producers of winding insulations, the manufacturers of high voltage rotating machines and the utilities to develop new insulation materials which can improve the life of the equipment and reduce the maintenance cost. The advent of nanotechnology in recent times has heralded a new era in materials technology by creating opportunities to significantly enhance the properties of existing conventional materials. Polymer nanocomposites belong to one such class of materials that exhibit unique combinations of physical, mechanical and thermal properties which are advantageous as compared to the traditional polymers or their composites. Even though they show tremendous promise for dielectric/electrical insulation applications, there are no studies relating to the long term performance as well as life estimation of the nanocomposites. Considering this, an attempt is made to generate an understanding on the feasibility of these nanocomposites for electrical insulation applications. An epoxy based nanocomposite system is chosen for this study along with alumina (Al2O3) and silica (SiO2) as the nanofillers. The first and the foremost requirement for studies on polymer nanocomposites is to achieve a uniform dispersion of nanoparticles in the polymer matrix, as nanoparticles are known to agglomerate and form large particle sizes. A laboratory based direct dispersion method is used to process epoxy nanocomposites in order to get well dispersed samples. A detailed microscopy analysis of the filler dispersion using Scanning Electron Microscope (SEM) has been carried out to check the dispersion of the nanofiller in the polymer. An attempt is made to characterize and analyze the interaction dynamics at the interface regions in the epoxy nanocomposite by glass transition temperature (Tg) measurements and Fourier transform infrared (FTIR) spectroscopy studies. The values of Tg for the nanocomposites studied decreases at 0.1 wt% filler loading and then starts to increase gradually with increase in filler loading. This Tg variation suggests that there is certainly an interaction between the epoxy chains and the nanoparticles. Also no new chemical bonds were observed in the spectra of epoxy nanocomposite as compared to unfilled epoxy. But changes were observed in the peak intensity and width of the –OH band in the spectrum of epoxy nanocomposite. This change was due to the formation of the hydrogen bonding between the epoxy and the nanofiller. The thermal conductivity of the epoxy alumina and the epoxy silica nanocomposites increased even with the addition of 0.1 wt% of the filler. This increase in thermal conductivity is one of the factors that make these nanocomposites a better option for electrical insulation applications. The dielectric properties of epoxy nanocomposites obtained in this investigation also reveal few interesting behaviors which are found to be unique and advantageous as compared to similar properties of unfilled materials. It is observed that the addition of fillers of certain loadings of nanoparticles to epoxy results in the nanocomposite permittivity value to be lower than that of the unfilled epoxy over the entire range of frequencies [10-2-106 Hz] considered in this study. This reduction has been attributed to the inhibition of polymer chain mobility caused by the addition of the nanoparticles. The tan values are almost the same or lower as compared to the unfilled epoxy for the different filler loadings considered. This behavior is probably due to the influence of the interface as the strong bonding at the interface will make the interface very stable with fewer defects apart from acting as charge trapping centres. From a practical application point of view, the surface discharge resistant characteristics of the materials are very important and this property has also been evaluated. The resistance to surface discharge is measured in the form of roughness on the surface of the material caused by the discharges. A significant enhancement in the discharge resistance has been observed for nanocomposites as compared to unfilled epoxy/ microcomposites, especially at longer exposure durations. The partial discharge (PD) measurements were carried out at regular intervals of time and it is observed that the PD magnitude reduced with discharge duration in the case of epoxy alumina nanocomposites. An attempt was made to understand the chemical changes on the surface by conducting the FTIR studies on the aged surface. For all electrical insulation applications, materials having higher values of dielectric strengths are always desired and necessary. So AC breakdown studies have also been conducted. The AC breakdown strength shows a decreasing trend up to a certain filler loading and then an increase at 5 wt% filler loading for epoxy alumina nanocomposites. It has been also observed that the type of filler as well as the thickness of the filler influences the breakdown strength. The AC dielectric strength of microcomposites are observed to be lower than the nanocomposites. Extensive research by long term aging studies and life estimation are needed before these new nanocomposites can be put into useful service. So long term aging studies under combined electrical and thermal stresses have been carried out on unfilled epoxy and epoxy alumina nanocomposite samples of filler loading 5 wt%. The important dielectric parameters like pemittivity, tan  and volume resistivity were measured before and after aging to understand the performance of the material under study. The leakage current was measured at regular intervals and tan  values were calculated with duration of aging. It was observed that the tan  values increased drastically for unfilled epoxy for the aging duration considered as compared to epoxy alumina nanocomposites. The life estimation of unfilled epoxy as well as epoxy nanocomposites were also performed by subjecting the samples to different stress levels of 6 kV/mm, 7 kV/mm and 8 kV/mm at 60 oC. It is observed that the epoxy alumina nanocomposite has an enhanced life which is nine times the life of the unfilled epoxy. These results obtained for the nanocomposites enable us to design a better material with improved dielectric strength, dielectric properties, thermal conductivity, resistance to surface discharge degradation and enhanced life without sacrificing the flexibility in the end product and the ease of processing. Dry type transformers and stator winding insulation need to be cast with the above material developed and tested before practically implementing these in the actual application.

Les dispersions de nanocomposite à base aqueuse sont produites pour des applications diverses telles que les adhésifs, les revêtements et plus récemment les encres. Ce projet consiste à réaliser des encres conductrices nanocomposites comprenant des particules de polymère (latex) à basse température de transition vitreuse, Tg, pour la formation de films à température ambiante, et des plaquettes de graphène, en raison de leurs excellentes propriétés conductrices. Les charges conductrices, appelées multi-feuillets de graphène, sont réalisées par broyage en voie aqueuse de graphite (1-10 µm) stabilisées par différents tensio-actifs et/ou stabilisants. Cette méthode sans solvant et à bas coût permet de produire des suspensions de multi-feuillets (1-10 feuillets) de graphène. Les particules de polymères utilisées sont synthétisées par polymérisation en émulsion de monomères acrylates. Dans un second temps, des mélanges physiques de suspensions de graphène et de latex acrylates ont permis d’obtenir des encres nanocomposites. L’ajout de graphène permet l’obtention d’un seuil de percolation à bas taux de charge et une nette amélioration des propriétés électriques et du renfort. Le diamètre des billes de latex a une influence importante sur ces propriétés et a également été étudié. Afin d’augmenter la stabilité des suspensions et les interactions graphène/latex, des nanocomposites structurés ont été synthétisés par polymérisation in situ en émulsion, miniemulsion ou dispersion en présence de graphène. Les excellentes propriétés électriques associées à leur flexibilité font de ces matériaux des candidats adaptés pour la réalisation d’encres conductrices pour impression sur textile. / Printed electronics, particularly on flexible and textile substrates, raised a strong interest during the past decades. This project presents a procedure that provides a complete and consistent candidate for conductive inks based on a graphene/polymer nanocomposite material. It consists in the synthesis of conductive inks nanocomposites comprising polymer particles (latex) with low glass transition temperature, Tg, and graphene platelets, for the conductive properties. The conductive particles, named Nanosize Multilayered Graphene (NMG), are prepared by wet grinding delamination of micro-graphite suspensions stabilized by various surfactants and/or polymeric stabilizers. This solvent-free procedure allows the formation of NMG suspensions with low thickness (1-10 sheets). Polymer particles are synthetized by surfactant-free emulsion polymerization with acrylates monomers.Physical blending of latex particles and NMG platelets are performed to obtain conductive nanocomposites inks. Adding NMG induce a low percolation threshold and a sharp increase of the electrical and mechanical properties of the nanocomposites. Moreover, the polymer particles diameters have an impact on these properties.To increase the formation of a well-defined cellular microstructure, the nanocomposites are also synthetized by in situ polymerization in presence of NMG platelets, using emulsion, miniemulsion or dispersion polymerization. The excellent electrical properties of these nanocomposites associated to their flexibility make these materials suitable candidates for the production of conductive inks for textile printing applications.

The dissertation consists of the following three sections: 1. Hydroxyapatite (HA) coatings. In this work, we deposited HA precursor films from weak basic electrolytic solution (pH= 8-9) via an electrochemical approach; the deposits were changed into crystallite coatings of hydroxyapatite by sintering at specific temperatures (600-800 ºC). The formed coatings were mainly characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRD patterns show well-defined peaks of HA when sintered under vacuum conditions. FTIR measurements indicate the existence of hydroxyl groups, which were confirmed by the characteristic intensity of the stretching and bending bands at ~3575 and ~630 cm-1, respectively. The SEM shows an adhesive, crack free morphology for the double-layer coating surface of the samples sintered in a vacuum furnace. 2. Silver/polymer/clay nanocomposites. Silver nanoparticles were prepared in layered clay mineral (montmorillonite)/polymer (PVP: poly (vinyl pyrrolidone)) suspension by an electrochemical approach. The silver particles formed in the bulk suspension were stabilized by the PVP and partially exfoliated clay platelets, which acted as protective colloids to prevent coagulation of silver nanoparticles together. The synthesized silver nanoparticles/montmorillonite/PVP composite was characterized and identified by XRD, SEM, and TEM (transmission electron microscopy) measurements. 3. Ce-doped lead zirconate titanate (PZT) thin films. In this study, we fabricated cerium-doped PZT films (molar ratio of Zr/Ti:: 0.5:0.5) via cathodic electrodeposition on the indium tin oxide ( ITO) coated glass substrate. In the preparation process, the PZT films were modified by adding a small amount of cerium dopants, which led to the formation of Ce-doped PZT films after sintering at high temperatures. The fabricated PZT films on the ITO coated glass substrate may be used as electro-optic devices in the industrial application.

Orientador: Julio Roberto Bartoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-07T21:53:07Z (GMT). No. of bitstreams: 1 Zanin_AileenNicoleFowler_M.pdf: 11356850 bytes, checksum: cf01903240aa482d9b8d8f3559af3823 (MD5) Previous issue date: 2006 / Resumo: Adesivo Sensíveis à Pressão (PSA) são adesivos poliméricos usados principalmente em fitas e etiquetas. De modo geral, existem três tipos de adesivos PSA: a base de solvente, a base d'água e "hot melt". Os adesivos a base de solvente apresentam algumas limitações como flamabilidade e toxicidade, mas ainda são amplamente usados, devido às propriedades finais que apresentam, como boa adesividade a substratos polares c boa adesão com alguns plásticos. Geralmente, os compostos poliméricos para PSA utilizam cargas minerais devido à redução de custo e às propriedades finais que os PSA podem apresentar, como propriedades dielétricas, resistência à umidade e tensão na ruptura. Por outro lado, nanocompósitos estão mostrando grandes vantagens em várias aplicações poliméricas, melhorando suas propriedades térmicas, mecânicas e retardância à chama. Adesivos PSA nanocompósitos a base de solvente foram preparados pelo processo de esfoliação-solução de compostos a base de borracha natural e argilas organicamente modificadas. Um planejamento fatorial de experimentos, 22 com replicata, foi utilizado para verificar a influência dos fatores da composição: concentração e tipos de argilas modificadas, nas propriedades físicas dos adesivos. Um composto adesivo de referencia (PSA convencional) foi também preparado utilizando CaCOH3, carga de uso comum nessas formulações. Os adesivos foram caracterizados através das suas propriedades adesivas (coesão ou "shear", adesão ao aço ou "peel" ,tlato à superfície ou "tack") gel e resistência à propagação de chama. A maioria dessas propriedades apresentou significância estatística em ao menos um dos fatores de composição estudados, tipo ou concentração de nanoargila. Os ensaios de resistência á propagação de chama mostraram melhoria nas propriedades de resistência à propagação da chama em todos os adesivos com argilas modificadas, comparados ao composto de referência. Análises TGA indicaram o mesmo comportamento de variação de massa em função da temperatura para lodos os adesivos. As análises DMTA dos adesivos mostraram diferenças entre os dois tipos de argilas modificadas quanto às suas Tg. Nas análises XRD dos adesivos não foram identificados picos de difração característicos das argilas, talvez devido à diluição das amostras ou até à desejada esfoliação. Nas análises de SEM dos compostos adesivos observou-se uma tênue forma lamelar devido às argilas e as análises EDS dos compostos indicaram a presença de Si e Al, constituintes da argila modificada / Abstract: Pressure sensitive adhesives (PSA) are polymeric adhesives used for mainly in tapes and labels. Usually, there are 3 types of PSA: solvent based, water based and hot melt. Solvent based adhesives have few limitations, like flammability and toxicity, but they are still often used, due to their properties as good adhesion to polar substrates and good bonding with some plastics. The compounds for pressure sensitive adhesives, in general, use fillers due to cost reduction and properties they can give, like dielectric properties, water resistance and tensile strength. On the other side, nanocomposites are showing great advantages on several polymers applications improving thermal resistance, flame retardancy and mechanical properties. Nanocomposites for solvent-based adhesives were prepared by an exfoliation-solution process of natural rubber and organically modified clay compounds. A Design of Experiment (DOE). 22 with replication, was used to verify the influence of compounding factors; concentration and grades of nanoclays.A control adhesive compound was prepared using CaCO3, very common filler for adhesive fonnulations. The PSA were characterized by their adhesive properties (cohesion or shear, adhesion to steel or peel test, tack), gel and flammability. Almost all these properties showed statistical significance at least for one of the compounding factors, grade or concentration of nanociay. The flammability tests showed an improvement on the flame retardancy properties for all the nanoclays adhesives compared to the control compound. TGA analyses showed the same pattern of mass reduction as a function of temperature for all the adhesives. DMTA showed differences between the 2 kinds of nanoclays regarding Tg. XRD analyses did not show any diffraction peak related to the clays, likely due to the diluted samples or even to an exfoliation. SEM analyses showed a slightly lamellar pattern of clays and EDS analyses of the compounds confirmed the presence of Si and Al, elements of the nanoclays / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Orientador: Yoon Kil Chang / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-18T15:58:47Z (GMT). No. of bitstreams: 1 Biasutti_ElizaAugustaRolim_D.pdf: 5427328 bytes, checksum: bb45f1359e2ca61015efd7dd7e6eddc1 (MD5) Previous issue date: 2011 / Resumo: Os plásticos de amido apresentam aplicações limitadas devido às pobres propriedades mecânicas e processabilidade, além de serem hidrofílicos. Para superar estas deficiências, a associação do amido com outros polímeros biodegradáveis ou a adição de nanoargilas são formas de se obter materiais de baixo custo, com melhores propriedades e compostáveis. O objetivo geral deste trabalho foi o desenvolvimento e avaliação de blendas poliméricas e nanocompósitos, obtidos por extrusão, extrusão de filme tubular e injeção, cujo principal componente da matriz polimérica foi o amido. No artigo I, para estudar o efeito da nanoargila sobre as propriedades mecânicas e estruturais de blendas poliméricas extrusadas de amido e gelatina, quatro misturas foram obtidas, sendo que as proporções de amido, gelatina, glicerol e água (100:20:40:40) foram mantidas constantes, enquanto o teor de nanoargila das blendas variou de 0 a 2,5%. Os resultados de difração de raios-X dos nanocompósitos revelaram a expansão dos espaços interlamelares consistentes com um processo de intercalação e, consequentemente, foi observado o aumento da resistência à tração (RT). No artigo II, para obtenção dos filmes de blendas poliméricas de amido de milho nativo (AN) e amido reticulado (AM) e poli (adipato de butileno-co-tereftalato) (PBAT) o processo de extrusão de filme tubular foi empregado. Para definição das misturas para produção dos filmes foi usada a metodologia de planejamento de misturas. As propriedades de tração dos filmes foram determinadas nas direções de fabricação (DF) e transversal (DT). Verificou-se que tanto para RT na DF quanto para o alongamento na ruptura (AR) na DF, os maiores valores de resposta, 5,48 MPa e 41,79%, respectivamente, foram encontrados para as composições localizadas próximo ao vértice do triângulo, correspondente às menores concentrações de AM e maiores concentrações de AN. Através da análise do perfil de desejabilidade, obteve-se a mistura ótima, correspondente à formulação com 60% de AN, 10% de AM e 30% de PBAT, que foi avaliada quanto às propriedades de barreira e estruturais (Artigo III). O filme de AN/AM/PBAT 60:10:30 apresentou coeficientes de permeabilidade ao vapor de água e ao oxigênio de 7,56 x 10-6 g. m-1.Pa-1.dia-1 e de 4997 cm3.µm.m-2.dia-1.atm-1, respectivamente. A análise das micrografias de microscopia eletrônica de varredura dos filmes mostrou uma estrutura heterogênea e a presença de grânulos de amido intactos, também visualizados nas micrografias de luz polarizada. Os espectrogramas de espectroscopia no infravermelho com transformada de Fourier e módulo de refletância total atenuada, revelaram que não houve uma boa compatibilização entre os amidos e o PBAT. O ensaio de degradação em solo simulado revelou que após 27 dias, o filme de AN/AM/PBAT 60:10:30 não apresentava fragmentos visíveis, enquanto o filme de PBAT puro havia perdido somente 1,5 % de sua massa inicial. No artigo IV, blendas de AN e PBAT foram obtidas por injeção para avaliar a variação das propriedades mecânicas, em função do tempo de permanência no solo. Verificou-se que, de uma forma geral, a blenda de AN/PBAT 50:50 apresentou uma redução na RT em função do tempo de enterramento no solo (cerca de 50% após 30 dias em solo), enquanto que a blenda de AN/PBAT 60:40 apresentou um comportamento completamente distinto, exibindo um aumento da RT em função do tempo de permanência no solo. Concluiu-se, portanto, que a obtenção de blendas poliméricas e nanocompósitos, à base de amido, empregando-se os processos de extrusão, extrusão de filme tubular e injeção, é uma alternativa tecnologicamente viável para o estudo e desenvolvimento de produtos plásticos biodegradáveis/compostáveis / Abstract: Starch plastics have limited applications due to poor mechanical properties and processability, in addition to being hydrophilic. To overcome these shortcomings, the combination of starch with other biodegradable polymers or the addition of nanoclays are ways to obtain low-cost compostable materials with improved properties. The aim of this work was the development and evaluation of polymeric blends and nanocomposites, obtained by extrusion, blown film extrusion and injection, whose main component of the polymeric matrix was starch. In article I, to study the effect of nanoclays on the mechanical and structural properties of extruded starch-gelatin blends, four mixtures were obtained with proportions of starch, gelatin, glycerol and water (100:20:40:40) that were kept constant while the nanoclay content ranged from 0 to 2.5%. The X-ray diffraction results revealed an expansion of the interlayer spaces consistent with an intercalation process, and, consequently, tensile strength (RT) increases were observed. In article II, to obtain films of polymeric blends of native cornstarch (AN), cross-linked starch (AM) and polybutylene adipate co-terephthalate (PBAT), the process of blown film extrusion was employed. To set the raw material mixtures for film production the methodology of mixture design was used. The tensile properties of the films were determined in the manufacture (DF) and transverse (DT) directions. It was found that both RT and elongation at break, both in the DF, the highest responses, 5.48 MPa and 41.79% respectively, were found for the compositions located near the apex of the triangle, corresponding to lower concentrations of AM and higher concentrations of AN. By analyzing the profile of desirability, the optimum mix ratio was obtained, corresponding to the formulation with 60% native cornstarch, 10% crosslinked starch and 30% PBAT, which was evaluated for barrier and structural properties (article III). The film of AN/ AM/ PBAT 60:10:30 showed coefficients of permeability to water vapor and oxygen of 7.56 x 10-6 g. m-1.Pa-1.day-1 and 4997 cm3.µm.m-2.day-1.atm-1, respectively. The film MEV analysis showed a heterogeneous structure and the presence of intact starch granules, also visualized through polarized light microscopy. FTIR-ATR analysis revealed that there not was a good match between the starches and PBAT. The degradation test in simulated soil showed that the film, after 27 days, did not present visible fragments in soil, while the PBAT lost just 1.5% of its initial mass. In article IV, AN and PBAT blends were obtained by injection to evaluate the changes on mechanical properties as a function of length of stay in simulated soil. It was found that, in general, the blend of AN/ PBAT 50:50 showed a reduction in the RT as a function of time in the soil (about 50% after 30 days), while the blend of AN/ PBAT 60:40 presented a completely different behavior, showing an increase of RT as a function of time in soil. Therefore, obtaining starch-based polymeric blends and nanocomposites, using the processes of extrusion, blown film extrusion and injection, is a technologically feasible alternative for the study and development of biodegradable/ compostable plastic products / Doutorado / Tecnologia de Alimentos / Doutor em Tecnologia de Alimentos

Orientador: Juliano Alves Bonacin / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T15:22:06Z (GMT). No. of bitstreams: 1 Santos_PamylaLayenedos_M.pdf: 4212017 bytes, checksum: 32d8be4cbad15f721c18e5490e98cb35 (MD5) Previous issue date: 2015 / Resumo: O azul da Prússia (AP) é um dos mais antigos compostos de coordenação e pode ser utilizado na modificação de sensores eletroquímicos para a detecção de H2O2, o AP pode catalisar a redução do peróxido e por isso é conhecido como "artificial peroxidase". Entretanto, filmes de AP não apresentam boa estabilidade eletroquímica e alternativas como a obtenção de nanocompósito baseados em AP e grafeno podem ser utilizadas para contornar o problema. O grafeno é um material com alta condutividade, flexibilidade e resistência à tração, pode ser obtido pelo método de Hummers que consiste na redução do óxido de grafeno e neste caso é chamado de óxido de grafeno reduzido. Assim, o objetivo deste trabalho é a obtenção fotoquímica de um nanocompósito baseado em azul da Prússia (AP) e óxido de grafeno reduzido (rGO) que permite uma combinação das propriedades eletrocatalíticas do AP e condutoras do rGO para a aplicação em sensores eletroquímicos. Além disso, espera-se uma maior estabilidade eletroquímica deste material. Os materiais óxido de grafeno reduzido e azul da Prússia foram obtidos separadamente pelos métodos químicos e fotoquímicos com a utilização de LEDs. Os resultados mostraram vantagens do método fotoquímico como o controle da morfologia e do tamanho dos cristais de azul da Prússia. O grau de redução dos materiais baseados em grafeno foi controlado com o tempo de irradiação no LED e isso foi refletido em suas propriedades eletroquímicas, com uma resposta linear da corrente de pico em função do grau de redução. O nanocompósito foi obtido pelo método fotoquímico in situ, e isso foi comprovado pelas técnicas DRX, espectroscopias Raman e UV-Vis. As micrografias obtidas por FEG-SEM mostraram a presença de cubos de AP sobre toda a superfície do óxido de grafeno reduzido. Espera-se que a interação entre o AP e rGO permita uma maior estabilidade eletroquímica do material que será testado no sensoriamento de H2O2 / Abstract: Prussian blue is one of the oldest coordination compounds and can be used on the modification of electrochemical sensors for the detection of H2O2, PB can catalyze the reduction of hydrogen peroxide and, for that, it is known as "artificial peroxidase". However, PB films do not show good electrochemical stability and alternatives such as the obtention of nanocomposites based on PB and graphene can be used to work around this problem. Graphene is a material with high conductivity, flexibility and tensile strength. Graphene can be obtained by Hummers method, which consists of reducing graphene oxide, in which case it is called a reduced graphene oxide. The goal of this work is photochemically obtaining a nanocomposite based on Prussian blue (PB) and reduced graphene oxide (rGO) that allows a combination of the electrocatalytical properties of PB and high conductivity of rGO for use in electrochemical sensors. In addition, we expect a higher electrochemical stability of this material. Reduced graphene oxide and Prussian blue were obtained separately by chemical and photochemical methods using LED. The results show the advantages of photochemical method to control the morphology and size of Prussian blue crystals. The reduction extent of graphene-based material was controlled by the irradiation time of the LED and this was reflected in its electrochemical properties, with a linear response of the peak current depending on the reduction extent. The nanocomposite was obtained by in situ photochemical method, and this was confirmed by XRD techniques, Raman and UV-Vis. The micrographs obtained by FEG-SEM showed the presence of PB cubes on the entire surface of the reduced graphene oxide. It is expected that the interaction between the PB and rGO allowing greater electrochemical stability of the material to be tested in H2O2 sensing / Mestrado / Quimica Inorganica / Mestra em Química

Orientador: Eliana Aparecida de Rezende Duek / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-27T23:48:09Z (GMT). No. of bitstreams: 1 Leal_ClaudeneteVieira_D.pdf: 6830750 bytes, checksum: e1a33a17e1e2276d0b1b5bace3231cb6 (MD5) Previous issue date: 2015 / Resumo: Nanocompósitos poliméricos exibem potencial para aplicações como biomateriais, pois podem melhorar as propriedades dos polímeros por meio da associação com nanoestruturas, resultando em um material com propriedades estruturais e funcionais superiores. O objetivo desse trabalho foi o desenvolvimento e posterior caracterização de nanocompósitos de poli (L-ácido lático) (PLLA) e nanotubos de carbono (NTC). Os NTC têm sido pesquisados para aplicações biomédicas devido às suas excelentes propriedades, entretanto, os NTC possuem características estruturais que podem causar toxicidade em ambiente biológico. Nesse trabalho, primeiramente foi aplicado um método para purificar os NTC por modificação química com objetivo de melhorar a dispersibilidade e diminuir os efeitos tóxicos. Posteriormente foram preparados os nanocompósitos na forma de membranas de PLLA com NTC em diferentes concentrações, utilizando o método de evaporação de solvente. Foram realizadas caracterizações morfológicas com microscopia eletrônica de varredura e microscopia de força atômica, estudo do comportamento térmico por calorimetria exploratória diferencial e microscopia ótica com luz polarizada, e ensaios mecânicos sob módulo de tração, análise dinâmico-mecânica e nanoindentação. Na última etapa foi realizado teste in vitro de cultura de células. Resultados indicaram aumento da rugosidade das amostras após a adição de NTC, o estudo do comportamento térmico revelou que o NTC atua como agente nucleante nos nanocompósitos, promovendo a formação de maior quantidade de núcleos cristalinos na matriz polimérica. As propriedades mecânicas indicaram aumento no módulo de elasticidade, alongamento e dureza nos nanocompósitos. Na análise biológica, os resultados obtidos comprovaram que, após a adição de NTC, as células foram capazes de aderir e sustentar a proliferação celular sobre as membranas, apresentando favorável citocompatibilidade / Abstract: Polymer nanocomposites exhibit potential for applications as biomaterials because they can improve the properties of polymers by combination with nanostructures, resulting in a material with superior structural and functional properties. The purpose of this work was the development and further characterization of poly (L-lactic acid) (PLLA) and carbon nanotubes (CNT) nanocomposites. CNTs have been investigated for biomedical applications due to their excellent properties, however, pristine NTC have structural characteristics that may cause toxicity in biological environment. In this work, a method to purify the NTC by chemical modification in order to improve the dispersibility and to reduce the toxic effects was firstly applied. Subsequently, PLLA/NTC nanocomposite membranes were prepared at different concentrations by solvent casting. Samples were characterized by scanning electron microscopy, atomic force microscopy, polarized optical microscopy, differential scanning calorimetry, dynamic mechanical analysis, tensile test, nanoindentation and X ray diffraction. In the last step, in vitro cell culture assay was performed. The results indicated an increase of the roughness of the samples after the addition of NTC. Thermal behavior study showed that the NTC act as a nucleation agent in nanocomposites, promoting the formation of a larger amount of crystal nucleous in the polymer matrix. Mechanical properties indicated an increase in elastic modulus, elongation and hardness in the nanocomposites. In biological testing, the results showed that, after addition of NTC, cells were able to adhere and sustain cellular proliferation on membranes and showed a favorable cytocompatibility / Doutorado / Materiais e Processos de Fabricação / Doutora em Engenharia Mecânica