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Thèses sur le sujet « Bionanocompositi »
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1
Iozzino, Valentina. « PLA-based bionanocomposites with modulated degradation rate : preparation and processing by microinjection molding ». Doctoral thesis, Universita degli studi di Salerno, 2019. http://elea.unisa.it:8080/xmlui/handle/10556/4646.
Texte intégralRésumé :
2016 - 2017... The aim of this work has been to obtain bionanocomposites with a degradation rate which can be modulated in time, so that it can be possible to decide a priori the time after which the material will disappear in a given environment. At the same time, the material should preserve its properties during processing. Several mixtures of PLA (4032D, 4060D) and LDH of cation composition Mg2Al organo-modified with organic acids (succinc, fumaric and ascorbic acid) have been obtained by extrusion. From the extruded materials there were obtained films by compression molding; these films were then subjected to hydrolysis tests. The experimental results show that for samples loaded with LDH-organic acid (in particular LDH-succinic acid), there is an increase in the time needed for degradation, and a decrease in this time for samples loaded with organic acid alone. From the selected material (PLA + LDH-succinic acid) and from pure PLA, biphasic samples (half amorphous and the other half crystalline) have been obtained by micro-injection molding. Also in this case, the experimental results show an increase for the loaded samples in the time needed for degradation compared to pure PLA both for the crystal phase and for the amorphous one, and in particular the presence of a degradation profile within the same sample is observed. [edited by Author]
XVI n.s. (XXX ciclo)
2
He, Jing. « Des (bio)nano-composites utilisés dans le traitement d'eaux contaminées par de l'arsenic/gentamicine ou pour des applications médicales ». Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00988092.
Texte intégralRésumé :
Les composés dits 'bionano' (bionanocomposites) apparaissent comme un nouveau groupe de matériaux hybrides nano-structurés. Ils sont issus de la combinaison de polymères naturels et de solides inorganiques et sont de l'ordre du nanomètre dans au moins une direction. Ces matériaux hybrides conservent les structures et les propriétés fonctionnelles des polymères et matériaux inorganiques dont ils sont composés. Parallèlement, la présence de biopolymères permet de diminuer les risques environnementaux et de santés publiques liés aux nano-matériaux. Les propriétés inhérentes aux biopolymères (biocompatibles' et biodégradables) ouvrent des perspectives intéressantes pour ces matériaux hybrides en particulier dans les domaines de la médecine regénérative et en génie de l'environnement. La production de bionanocomposites de taille plus importante, que les nanoparticules qu'ils renferment, permet d'éviter les effets nocifs potentiels des nanoparticules (NPs) pour les organismes vivants et plus particulièrement pour l'homme. L'association de biopolymères et de nano-solides inorganiques permet la conception de bionanocomposites multifonctionnels qui peuvent être synthétisés et utilisés pour des applications dans des domaines variés. Cette thèse se propose d'étudier principalement (i) ma présence d'arsenic et d'antibiotiques dans les sources d'eau potable en Chine; (ii) l'évaluation d'un nouveau bionanocomposites, à savoir le CGB (chitosan goethite bionanocomposite), dans la décontamination des eaux contenant des espèces inorganiques d'arsenic; (iii) l'évaluation d'argiles comme adsorbants de décontamination de la gentamicine (un antibiotique aminoglycoside ) présent dans l'eau de même que celle de bionanocomposés fait d'argiles riches en gentamicine de polymères de methycelluloses hydroxypropyles Gt-Mt-HPMC (gentamicin-montmorillonite- hydroxypropyl methycellulose) utilisés comme pansement contre les infections qui ont lieu suite à des brûlures.
3
Belda, Marín Cristina. « Silk bionanocomposites : design, characterization and potential applications ». Thesis, Compiègne, 2020. http://www.theses.fr/2020COMP2570.
Texte intégralRésumé :
Les « bionanocomposites » à base de soie sont des matériaux qui suscitent un intérêt croissant dans de nombreuses applications, et en particulier dans le domaine biomédical, de par leur capacité à combiner les propriétés de la fibroïne (biodégradabilité, biocompatibilité et propriétés mécaniques intéressantes) et celles des nanoparticules (NP). L’objectif de ce travail est de (i) développer une méthode efficace, et « facile » à mettre en oeuvre, permettant l’élaboration de plusieurs types de bionanocomposites de soie ; (ii) fournir une caractérisation approfondie pour une meilleure compréhension de l’interface soie/NP ; et (iii) présenter des applications pertinentes en relation avec les propriétés spécifiques de ces bionanocomposites. Pour ce faire, les NP, d’or (Au NP), d’argent (Ag NP) et d’oxyde de fer (IONP) ont été utilisées en raison de leurs propriétés bien connues. L’élaboration de bionanocomposites à base de soie, tels que les tissus électrofilées, hydrogels, aérogels, éponges et structures imprimés en 3D est décrite. Une caractérisation approfondie, y compris des mesures in situ (pendant la formation du gel) et des analyses ex situ (une fois le gel formé), des hydrogels de soie montre qu’aucune différence significative n’est observée dans la structure de l’hydrogel, alors que la biocompatibilité des matériaux est préservée. Enfin, une application potentielle pour chaque « bionanocomposite » est présentée. Dans une perspective biomédicale, les hydrogels soie-Ag NP montrent une activité antibactérienne significative. Les hydrogels soie-IONP, implantés dans le cerveau d’un rat et suivis par imagerie de résonance magnétique (IRM), montrent l’induction d’une procédure de régénération du cerveau pendant au moins 3 mois. Dans une perspective liée à la dépollution, les hydrogels soie-Au NP montrent des performances remarquables dans la catalyse de la réaction de réduction du bleu de méthylène par le borohydrure de sodiumSilk-based bionancompoistes have attracted a growing interest in numerous applications, particularly in the biomedical field, owing to their ability to combine the specific properties of silk fibroin (biodegradability, biocompatibility and interesting mechanical properties) and nanoparticles (NPs). This work aims to (i) develop a straightforward, yet efficient, methodology to design various silk bionanocomposite materials; (ii) provide an in-depth characterization regarding the silk/NPs interface and (iii) provide potential applications which are relevant for the use of these bionanocompoistes. To this end, gold (Au NPs), silver (Ag NPs) and iron oxide (IONPs) NPs are used as model nanomaterials due to their well-known properties. The successful design of silk bionancocomposite electrospun mats, hydrogels, cryogels, sponges and 3D printed structures is described. An in-depth characterization, including in situ (during hydrogel formation) and ex situ (once hydrogel is formed), of silk hydrogel bionanocomposites do not reveal any noticeable structural changes of silk hydrogels, while their biocompatibility is not impacted by the incorporation of NPs. Finally, a potential application for each bionanocomposite is presented. In a biomedical perspective, silk-Ag NPs hydrogels bionanocomposites show significant antibacterial activity. Silk-IONPs hydrogel bionanocomposites are implanted into rat’s brain allowing a good monitoring of the implant by magnetic resonance imaging and inducing a brain regeneration process up to 3 months. In depollution perspective, silk-Au NPs hydrogel bionanocomposites show remarkable ability to adsorb and catalyze the reduction of methylene blue dye by sodium borohydride
4
Silva, Mariana Rodrigues Ferreira da. « Active and intelligent bionanocomposites for food packaging ». Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22400.
Texte intégralRésumé :
Mestrado em BiotecnologiaA produção de plásticos, baseados no uso de combustíveis fósseis, está a aumentar e estima-se que esta tendência continuará no futuro com impactos ambientais consideráveis. Os bioplásticos são uma alternativa amiga do ambiente. Biopolímeros como quitosana já foram adotados com sucesso para produzir bioplásticos que agem como substitutos do plástico em embalagem. A quitosana foi selecionada devido às suas numerosas vantagens para embalagem alimentar, principalmente devido às suas atividades antioxidantes e antimicrobiana. Por outro lado, o dióxido de titânio foi selecionado como aditivo devido à sua capacidade de retirar oxigénio do ambiente e devido à possibilidade de poder ser facilmente funcionalizado para a formação de um sensor. Isto permitiria a formação de uma embalagem ativa e inteligente na proteção do alimento. Assim, nanopartículas homogéneas arredondadas e monofásicas de anatase de dióxido de titânio (TiO2) foram usadas para melhorar os filmes de quitosana, criando um bionanocompósito. Estas nanopartículas de TiO2 foram produzidas por síntese hidrotermal, tendo sido otimizadas as condições de síntese, como a temperatura e tempo, para selecionar as condições que originam as nanopartículas com as caraterísticas desejadas. As condições escolhidas para a produção do TiO2 foram 200 ºC e 2,5 h devido ao tamanho, dispersão e tipo de nanoparticulas de TiO2 produzidas. Os filmes de quitosana foram preparados com cerca de 9 mg de nanopartículas de TiO2. Para criar uma embalagem ativa e inteligente compostos fenólicos (principalmente antocianinas) de arroz preto (Oryza sativa L. Indica) foram adicionados para funcionalizar o TiO2 (4,1 mg de extrato por filme). Os filmes foram caracterizados em relação à sua atividade antioxidante, humidade, solubilidade, hidrofobicidade da superfície e propriedades mecânicas. Os melhores resultados foram obtidos nos filmes com nanopartículas e compostos fenólicos e foi demonstrado que a forma como cada componente é adicionado altera as suas propriedades. Os melhores resultados foram o aumento da atividade antioxidante, diminuição da solubilidade e da elasticidade, elongação e resistência à tração no filme composto por pigmento e TiO2,. No entanto nestes últimos três parâmetros, a sua diminuição pode ser um aspeto positivo ou negativo dependendo das propriedades desejadas para o filme e o produto alimentar a embalar
Plastic production based in fossil fuels is rising, and predictions supports it continuous and enhanced use, with consequent environmental damage. Bioplastics are an environmentally friendly alternative. Biopolymers as chitosan have already been successfully used to produce bioplastics that act as plastic substitutes in packaging. Chitosan was chosen for its numerous advantages for food packaging namely due to its antioxidant and antimicrobial activities. On the other hand, TiO2 was selected due to its oxygen scavenging ability and due to its possibility to be easily functionalised to create a sensor. This would allow the construction of an active and intelligent packaging for food protection. Thus, monophasic anatase homogeneous round-shaped nanoparticles of titanium dioxide (TiO2) were used as filler to improve the chitosan films, creating a bionanocomposite. These TiO2 nanoparticles were produced via a hydrothermal method and its synthesis was optimized testing various reaction times and temperatures to find the conditions that create TiO2 nanoparticles with the desired features. The conditions used for the chosen TiO2 were 200 ºC and 2.5 h due to the size, dispersion and TiO2 of the nanoparticles produced. The chitosan films were prepared with about 9 mg of TiO2 nanoparticles. To develop an active and intelligent food packaging, phenolic compounds (mainly anthocyanins) from black rice (Oryza sativa L. Indica) were used to functionalise the TiO2 (4.1 mg of extract in each film). The films were characterised regarding its antioxidant activity, humidity, solubility, surface hydrophilicity and mechanical properties. The best results were from films with both nanoparticles and phenolic compounds, and it was established that the order in which they are added alters its properties. The more notable improvements are an increase in antioxidant activity and a decrease in solubility, elasticity, elongation and tensile strength in the film containing pigment and TiO2. However, the reduction of the later three properties can either be positive or negative, it depends on desired properties for the film for a chosen food product
5
Nechyporchuk, Oleksandr. « Nanofibres de cellulose pour la production de bionanocomposites ». Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI056/document.
Texte intégralRésumé :
Un des principaux challenges dans le contexte du développement des matériaux biocomposites est de remplacer les matières plastiques à base de pétrole par des matériaux biosourcés. En raison de leurs origines naturelles, d'une résistance relativement élevée et de leur capacité à former des produits transparents, les nanofibres de cellulose possèdent un grand potentiel d'applications dans les matériaux composites. Dans ce travail des résultats ont été apportés premièrement sur l'optimisation des procédés de productions de nanofibres de cellulose par des traitements biochimiques et mécaniques, deuxièmement sur leurs propriétés rhéologiques et structurelles en milieu aqueux et troisièmement sur la production de composites à matrice de latex. Les questions de dispersions homogènes de nanofibres de cellulose dans la matrice et des interactions entre ces composants à des fins de renforcement des bio-composites ont été étudiés en détailsOne of the main challenges in the context of biocomposites development is to replace petroleum-based materials with bio-based. Because of their natural origin, relatively high strength and the ability to form transparent products, cellulose nanofibers have a large potential for application in the composite materials. This work was focused primarily on the optimization of cellulose nanofiber production methods using biochemical and mechanical treatments, secondly on their rheological and structural properties in an aqueous medium and thirdly on the production of latex-based composites. The questions of homogeneous dispersion of cellulose nanofibers in the matrix and the interactions between these components for the purpose of matrix reinforcement are particularly addressed
6
Mousa, Mohanad Hashim. « Experimental Characterisation and Modelling of Sustainable Multiscaled Bionanocomposites ». Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75691.
Texte intégralRésumé :
Novel polyvinyl (PVA) bionanocomposite films reinforced with four different types of nanofillers were manufactured based on a solution casting method. The effect of nanofiller size, shape and content on the material performance of bionanocomposites was holistically investigated in experimental characterisation. Furthermore, nanomechanical properties and dimensions of nanointerphases in PVA bionanocomposites were systematically determined via peak force quantitative nanomechanical tapping mode (PFQNM). Finally, newly developed micromechanical modelling results confirmed good agreement with experimental data.
7
Piazzolla, Caterina. « Study of plasticised PLA based bionanocomposites reinforced with nanofibrillated cellulose ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Trouver le texte intégralRésumé :
In this study polylactide (PLA)-based nanocomposites plasticised with poly(ethylene glycol) (PEG) and nanofibrillated cellulose (NFC) were evaluated. Their physico-chemical properties were assessed by field emission scanning electron microscopy (FE-SEM), gel permeation cromatography (GPC), tensile testing machine, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effect of PEG with molecular weight of 400 g·mol-1 and 1500 g·mol-1 (PEG-400 and PEG-1500) and the influence of nanofibrillated cellulose (NFC) with different concentration (0, 1, 3, 5 wt%) on the polylactide, were analysed. No pores or cracks were observed in the evaluation of the cryo-fracture surface, suggesting an adequate processing strategy. The study of molar mass variation revealed that the additional processing step for the blends and composites promoted slight chain scission of PLA. The addition of NFC provoked a slight decrease in molar mass possibly due to the shear effects caused by the presence of nanofibrils during processing. With the incorporation of PEG-1500, the tensile strength and modulus decreased, whereas the elongation at break increased by 70%. Further, the nanocomposites showed increased rigidity and lower tensile strength in comparison to the blends. The microscopic evaluation of the fracture surface after tensile test suggested the possible agglomeration of NFC as the cause for this behaviour, especially for high NFC contents. The study of the thermal and thermo-oxidative stability highlighted the presence of PEG, as it decomposed at lower temperatures than the PLA. Finally, the presence of PEG decreased the glass transition temperature and the degree of crystallinity. Complementarily, the addition of NFC nanoparticles increased the PLA crystallinity due to its nucleation effects. This behaviour occurred for NFC contents between 1 and 3% wt., which suggested feasible nanoparticle agglomeration for higher concentrations.
8
Vassalli, J. Todd Grant Sheila Ann. « Development of electrospun synthetic bioabsorbable fibers for a novel bionanocomposite hernia repair material ». Diss., Columbia, Mo. : University of Missouri--Columbia, 2008. http://hdl.handle.net/10355/5631.
Texte intégralRésumé :
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 6, 2009). Thesis advisor: Dr. Sheila Grant, Includes bibliographical references.
9
Bettini, Giacomo. « Bionanocomposites based on Plla, Pcl and montmorillonite : synthesis, characterization and crystallization ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10025/.
Texte intégralRésumé :
Poly(lactide) is one of the best candidate to replace conventional petroleum-based polymers, since it is biobased, biocompatible and biodegradable. However, commercial PLA materials typically have low crystallization rate resulting in long processing time and low production efficiency. In this work the effects of two nanofillers MMT30B and MMT30B-g-P(LA-co-CL) on the crystallization rate of neat PLA and PLA/PCL blend were investigated.
MMT30B-g-P(LA-co-CL) was synthetized by in situ grafting reaction. The synthesis was carried in xylene at 140°C, upon the results of a screening. The grafted copolymers were evaluated by 1H-NMR ,ATR–IR and TGA. Solvent casted films were obtained by mixing MMT30B-g-P(LA-co-CL) at 5% (w/w) with neat PLA and PLA/PCL blend, comparing the properties with the corresponding blends with and without a 5% of (w/w) unmodified clay. SEM images on PLA based blends shows that MMT30B is aggregated into larger particles compared to MMT30B-g-P(LLA-co-CL). This behavior is correlated to the better exfoliation of MMT30B-g-P(LA-co-CL) clay layers. SEM images on PLA/PCL based blends exhibit the typical sea-island morphology, characteristic of immiscible blends. PLA is the matrix while PCL is finely dispersed in droplets. MMT30B does not reduce PCL droplets size, while MMT30B-g-P(LA-co-CL) reduces the size of PCL droplets. This means that MMT30B-g-P(LA-co-CL) can migrate to the PLA-PCL interface, acting as a compatibilizer.
Non-isothermal DSC cooling scans show a fractionated crystallization of the PCL phase in PLA/PCL/MMT30B-g-P(LA-co-CL), confirming the compatibilizer effect of MMT30B-g-P(LA-co-CL). At the same timeMMT30B-g-P(LA-co-CL) can better nucleate the PLA phase, both in neat PLA and PLA/PCL blend, promoting the crystallization during the heating scans. In isothermal condition, both the nanofillers increase the crystallization rate of PLA phase in neat PLA, while in PLA/PCL blends the effect is covered by the nucleating effect of PCL.
10
Touati, Souad. « Elaboration d'aérogels d'hydroxydes doubles lamellaires et de bionanocomposites à base d'alginate ». Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-00975932.
Texte intégralRésumé :
Cette thèse présente un travail sur l'obtention d'aérogels d'HDL par séchage en conditions CO2 supercritique et l'élaboration de nouveaux bionanocomposites formés par la coprécipitation d'hydroxydes doubles lamellaire (HDL) dans l'espace confiné des billes d'alginate. Grâce à la combinaison d'une synthèse par coprécipitation Flash et d'un séchage en conditions supercritiques au CO2, des aérogels d'HDL possédant des surfaces spécifiques élevées sont élaborés. Parallèlement, l'alginate est utilisé comme une matrice de confinement pour la précipitation inorganique d'HDL. D'une part, les billes d'alginate sont synthétisées par complexation des ions Ca2+ et la coprécipitation des phases HDL s'effectue en réalisant des imprégnations successives de réactifs. D'autre part, des billes d'alginate sont formées directement en présence des cations divalents (Mg2+, Ni2++, Co2+, ...) et des cations des métaux trivalents (Al3+), précurseurs des composés inorganiques. La coprécipitation des HDL se produit dans ce cas lors d'une étape d'imprégnation dans une solution d'hydroxyde de sodium. Tous les composés HDL, aérogels ou encore bionanocomposites sont caractérisés en détail par DRX, spectroscopie IR, MEB/MET, adsorption/désorption d'azote et ATG/DTG, pour obtenir un meilleur aperçu de la structure des particules, de leur taille et de leur morphologie. Des études menées sur l'adsorption de la trypsine pour les aérogels ou encore sur les performances d'électrodes modifiées HDL-alginate ont permis de montrer qu'il était possible d'améliorer les performances des HDL en augmenter leur porosité et en élaborant des bionanocomposites.
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Liu, HuiHua. « Synergistic interactions of plasticizers and nanoclays in hydrophilic starch based bionanocomposites ». Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1758.
Texte intégralRésumé :
Depletion of non-renewable resources and exorbitant levels of carbon dioxide emissions have questioned the further usage of traditional plastics. The imbalance in global sustainability has necessitated the development and use of biodegradable polymers. This research work set sights on understanding the synergistic interactions of plasticizer, starch and Na[superscript]+-montmorillonite (MMT). Having a clear view of the molecular behavior within this ternary system ameliorates the performance of the end product and fabrication of the tailored-property biodegradable polymers. Conversely, the explicit information of the synergistic Interactions of Plasticizers and MMT in hydrophilic starch is still vague. Hence a great degree of work and effort has been put forward through this work to understand the fundamental principles of competitive interaction.The study emphasizes on modelling the kinetics of various components in the system such as crystallisation of the long chain starch, water diffusion from the polymer matrix and the interaction between the MMT molecules and the water molecules. It was observed that the interactions between MMT and plasticiser were enhanced upon increasing the MMT loading. The high hydrophilicity of plasticizer ensured a stronger interaction of plasticizer/MMT which overtook the MMT/MMT interaction causing a dimensional increase in basal spacing in the high plasticiser loading samples.GAB model based on the multi-layer kinetics has been applied in the current work to understand the isotherm behaviour. Small Angle X-ray Scattering (SAXS) was employed to determine the diffraction pattern and intensity of the samples at the micro/nano structural level and thereby fathom the orientation of the crystalline domains. Differential Scanning Calorimetry was carried out to indicate the changes in T[subscript]g/T[subscript]m values of various samples and the corresponding degree of plasticization. The obtained results were then interpreted with Avrami equation to reach solid conclusions.The crystallization ability and intermolecular hydrogen bond strength of the applied plasticizer were the key parameters that affected the crystallisation process. The crystallisation mechanism in xylitol-plasticized samples differed from that of glycerol/sorbitol-plasticized samples. It was also determined that the molecular size of the plasticizer was another significant element that influenced the crystalline domain formation. The interaction process was defined into three stages based on the concentration of plasticizer used. The plasticizer concentration for the formation of a loosen-soft polymeric network and tighten-firm polymeric network was categorised. Correspondingly, the ‘threshold’ value for glycerol, xylitol and sorbitol-plasticized systems was characterised to be 5%, 10% and 5%, respectively. Morphological observations such as Wide Angle X-ray Diffraction (WAXD) and Transmission electron microscopy (TEM) has been utilised to examine the morphology formed in all nanocomposite samples.A relatively unsaturated loosen-soft polymeric network was formed and the starch/plasticizer interaction and starch/MMT interaction transpired without interfering each other within the threshold limits. Nonetheless, beyond the threshold, a relatively saturated tighten-firm polymeric network was observed as confirmed by x-ray scattering results, the molecular dynamic modelling results and Positron Annihilation Lifetime Spectroscopy (PALS) measurements from representative samples. Plasticizer/plasticizer interactions significantly altered the MMT exfoliation process and crystallization behaviour of the corresponding sample.The complex interactions existing in the polymeric system were found to be dependent on several main factors including type of the plasticizer and the relative ratio of plasticizer and MMT. These factors have been kept in mind whilst designing the modes of experiment and understanding the related outcomes. The incidence of excess moisture successfully modified the interactions amongst starch/ MMT/plasticizer. Water molecules behaved like a typical plasticizer and occupied most of the small voids between the starch polymers throughout the polymeric network.
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Abdullah, Zainab Waheed. « Polyvinyl Alcohol / Starch/ Glycerol/ Halloysite Nanotube Bionanocomposites for Biodegradable Packaging Applications ». Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/81687.
Texte intégralRésumé :
Polyvinyl alcohol/ starch/ glycerol/ halloysite nanotube bionanocomposite films were manufactured using the solution casting method. The effect of material composition and nanofiller contents on mechanical, thermal, optical, water resistance and biodegradable properties as well as the migration rates of material constituents were investigated along with the morphological structures. Modelling approaches for permeabilities have developed based on Nielsen model and Cussler model in good agreement with experimental results. Finally, prepared bionanocomposite films were confirmed to be effective food-packaging materials for lipidic and acidic fruits.
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ÜNALAN, İ UYSAL. « POTENTIAL USE OF GRAPHENE FOR THE GENERATION OF BIONANOCOMPOSITE MATERIALS FOR FOOD PACKAGING APPLICATIONS ». Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/245012.
Texte intégralRésumé :
Lo sviluppo di nuovi materiali multifunzionali, a minore impatto ambientale e con benefici economici, rappresenta una impellente necessità. L’avvento delle nanotecnologie ha aperto la strada a nuove possibilità, ad esempio attraverso lo sviluppo di materiali biopolimerici nanostrutturati. Questa tesi di dottorato si propone di illustrare nuove strategie per lo sviluppo di bionanocompositi a base di grafene per specifiche applicazioni nel settore dell’imballaggio alimentare. L’uso del grafene mira ad approfondire le conoscenze circa la potenziale applicazione di tale filler inorganico come alternativa alle attuali soluzioni. Il progetto è stato suddiviso in quattro parti.
Nella prima parte è stato valutato l’uso del pullulano per la produzione di bionanocompositi a base di ossido di grafene (GO), con particolare riferimento alle proprietà di barriera all’ossigeno, proprietà meccaniche, termiche ed ottiche. I dati sperimentali di barriera all’ossigeno e quelli meccanici, inoltre, sono stati confrontati con quelli ottenuti mediante l’uso di tre modelli predittivi, ovvero Nielsen e Cussler per le barriere, Halpi-Tsai per le prove meccaniche. La modellazione ha indicato come il miglioramento delle proprietà di barriera e di quelle meccaniche fosse dovuto a tre effetti principali: i) affinità chimica tra GO e pullulano, con conseguente miglioramento delle forze di adesione all’interfaccia tra le due fasi; ii) prevalente allineamento unidirezionale del filler inorganico; iii) elevata area superficiale e bidimensionalita del GO.
I risultati ottenuti nella prima parte del progetto hanno evidenziato l’enorme potenzialità dei bionanocompositi a base di pullulano e grafene ad agire da barriera all’ossigeno anche ad elevate umidità (70% RH). Tuttavia, i costi elevati possono limitarne l’applicazione nel settore dell’imballaggio alimentare. Per tale motivo, nella seconda parte del progetto si è deciso di valutare la possibilità di utilizzare altri biopolimeri in combinazione col pullulano. Sono stati pertanto sviluppati film a base di pullulano e chitosano e pullulano e alginato. Questi films hanno evidenziato proprietà meccaniche e termiche superiori ai film di solo pullulano mantenendo le proprietà barriera. Inoltre, i valori di opacità e trasmittanza sono stati mantenuti entro i valori ‘limite’ del 3% e del 90% (a 550 nm) comunemente accettati per le applicazioni nell’imballaggio alimentare. Non meno importante, l’ottenimento di tali blend ha permesso una maggiore efficienza in termini di performance/costi.
La terza parte del progetto ha avuto come obiettivo lo sviluppo di sottili strati bionanocompositi a base di pullulano e GO. Tali strati sono stati depositati su polietilene tereftalato (PET), al fine di migliorarne specifiche proprietà, senza compromenetterne la funzionalità. L’esfoliazione del GO è avvenuta mediante ultrasonicazione, che è risultato essere un trattamento ‘chiave’ al fine di ottenere specifiche proprietà di barriera e meccaniche del coating finale.
La quarta ed ultima parte del progetto si è incentrata su nuove strategie per la produzione di grafene, con particolare riferimento all’uso dell’ultrasonicazione facilitare l’esfoliazione di grafite in grafene mediatada dalla presenza di polisaccaridi. I risultati ottenuti in quest’ultima fase del progetto hanno evidenziato la possibilità di ottenere grafene mediante un processo pulito, efficiente e a basso costo.The development of new packaging materials offering new functionalities, less environmental impact, and economical benefits is nowadays an urgent necessity. The advent of nanotechnology opened new possibilities toward this goal, e.g. by the generation of a new class of bionanocomposite films or coatings for “greener” packaging structures with same or even better overall performance compared to the conventional materials. This PhD thesis has been conceived as an effective and promising strategy for the development of biopolymer nanocomposites based on graphene specifically intended for food packaging applications. Within this context, the use of graphene aims to prompt new research on this unexplored inorganic filler in the food packaging sector as a potential alternative to the currently used solutions. The overall project has been divided into four parts. In the first part, the use of pullulan to produce graphene oxide (GO)-bionanocomposites was investigated for the first time in terms of oxygen barrier, tensile, thermal, and optical properties. To get deep understanding on the physical arrangement of the newly generated biopolymer nanocomposites, both oxygen permeability and elastic modulus experimental data were compared with predictive models (Nielsen and Cussler models, and Halpin–Tsai model, respectively). These models, complemented by morphological observations, suggested that the simultaneous improvement of mechanical and oxygen barrier properties was attributed to three main effects: i) chemical affinity between GO and pullulan, which significantly enhanced the interfacial adhesion between the two phases; ii) prevalent unidirectional alignment of GO sheets in the pullulan matrix, parallel to the surface of nanocomposite films; and iii) high specific surface area and 2D geometry of GO. The results obtained in the first part disclosed the great potential of graphene-based pullulan bionanocomposites as oxygen barrier even at high relative humidity (70% RH) values. However, high cost of pullulan may limit its applications in food packaging. Therefore, in the second part, GO-enhanced pullulan/chitosan and pullulan/alginate blend systems were prepared using the same technique used in part 1. Compared to pure pullulan films, optimized bionanocomposite blend films exhibited enhanced mechanical and thermal properties and comparable oxygen performance while keeping the haze formation within the 3% threshold and transmittance below 90% at 550 nm, which are adequate values for most applications in the food packaging sector. These optimized formulations allowed achieving a well-balanced performance/cost ratio. The third part of the project was aimed to design bionanocoatings combining pullulan and GO to be applied on polyethylene terephthalate (PET). The rationale behind this approach lies in the fact that most examples on the use of nanosized fillers concern bulky biopolymers. Only very recently it has been proposed the use of fillers within coatings made of biopolymers to produce bionanocomposite coatings to improve the properties of a plastic substrate without jeopardizing its original attributes and optimize cost efficiency. Full exfoliation of GO platelets during preparation of the coating water dispersions was mediated by ultrasonic treatment, which turned out to be a pivotal factor in the oxygen barrier performance of the final material at 0 and 30% RH condition as well as in its stiffness, elongation, and friction properties. The fourth and last part of the PhD project focused on the graphene production. Specifically, the capability of three different biopolymers (the positively charged polyelectrolyte chitosan, the uncharged pullulan, and the anionic polyelectrolyte alginate) was evaluated to promote the direct exfoliation of graphite into graphene sheets in an aqueous medium by means of high-intensity ultrasonication. Findings arising from this work suggest that non-ionic pullulan and cationic chitosan are more effective to exfoliate graphite into graphene under ultrasonication than anionic alginate, which was attributed to thermodynamic reasons. This approach provides an economical, solvent-free, high-yield, and industrially scalable route for new applications of graphene-based nanocomposites, e.g. in the food packaging industr
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Tavernelli, Alice. « Synthesis, characterization and crystallization of bionanocomposites based on PLLA, PCL and nanocellulose ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9317/.
Texte intégralRésumé :
In recent years, environmental concerns and the expected shortage in the fossil reserves have increased further development of biomaterials. Among them, poly(lactide) PLA possess some potential properties such as good ability process, excellent tensile strength and stiffness equivalent to some commercial petroleum-based polymers (PP, PS, PET, etc.). This biobased polymer is also biodegradable and biocompatible However, one great disadvantage of commercial PLA is slow crystallization rate, which restricts its use in many fields. Using of nanofillers is viewed as an efficient strategy to overcome this problem.
In this thesis, the effect of bionanofillers in neat PLA and in blends of poly (L-lactide)(PLA)/poly(ε-Caprolactone) (PCL) has been investigated. The used nanofillers are: poly(L-lactide-co-ε-caprolactone) and poly(L-lactide-b-ε-caprolactone) grafted on cellulose nanowhiskers and neat cellulose nanowhiskers (CNW). The grafting reaction of poly(L-lactide-co-caprolactone) and poly (L-lactide-b-caprolactone) on the nanocellulose has been performed by the grafting from technique. In this way the polymerization reaction it is directly initiated on the substrate surface. The condition of the reaction were chosen after a temperature and solvent screening. By non-isothermal an isothermal DSC analysis the effect of bionanofillers on PLA and 80/20 PLA/PCL was evaluated. Non-isothermal DSC scans show a nucleating effect of the bionanofillers on PLA. This effect is detectable during PLA crystallization from the glassy state. Cold crystallization temperature is reduced upon the addition of the poly(L-lactide-b-caprolactone) grafted on cellulose nanowhiskers that is most performing bionanofiller in acting as a nucleating agent.
On the other hand, DSC isothermal analysis on the overall crystallization rate indicate that cellulose nanowhiskers are best nucleating agents during isothermal crystallization from the melt state. In conclusion, nanofillers have different behavior depending on the processing conditions. However, the efficiency of our nanofillers as nucleating agent was clearly demonstrated in both isothermal as in non-isothermal condition.
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Castro, Smirnov Fidel Antonio. « Physicochemical characterization of DNA-based bionanocomposites using nonafibrous clay minerals : biological applications ». Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112260/document.
Texte intégralRésumé :
Parmi les différents minéraux argileux, la sépiolite, qui est un silicate fibreux naturel, est un potentiel nano-transporteur prometteur pour le transfert non-viral de biomolécules. Il a en effet été montré que la sépiolite interagissait avec des molécules biologiques telles que les lipides, les polysaccharides et les protéines. Dans ce travail, nous démontrons que la sépiolite interagit également efficacement avec différents types de molécules d'ADN (génomique, plasmidique, oligonucléotides simple et double brin), et nous présentons la première étude détaillée sur les mécanismes d'interaction entre la sépiolite et l'ADN, ainsi qu’une caractérisation physico-chimique de bionanocomposites ADN-sepiolite. Une analyse spectroscopique a montré tout d’abord que l’interaction de l'ADN avec la sépiolite était plus forte en présence de polycations, la valence de ces derniers accroissant le rendement d’absorption, et deuxièmement, que l'ADN ainsi adsorbé pouvait être récupéré avec un rendement modulé par la présence d’EDTA, la structure de l'ADN et son activité biologique étant conservées. Par spectroscopie infrarouge à transformée de Fourier (FTIR) nous avons identifié les groupes silanol externes comme les principaux sites d'interaction avec l'ADN. Nous avons ensuite prouvé qu'il est possible d'utiliser la sépiolite pour extraire l'ADN de bactéries, pour la purification de l'ADN et pour la purification de toute contamination bactérienne. En combinant la microscopie à fluorescence, la microscopie électronique à transmission (MET), la vidéo-microscopie et l’analyse par cytométrie en flux (FACS), nous avons montré que la sépiolite peut être spontanément internalisée dans des cellules de mammifère par le biais de deux voies, l’endocytose et la macropinocytose. En tant que preuve de concept, nous montrons que la sépiolite est capable de transférer de manière stable l'ADN de plasmide dans des bactéries et des cellules de mammifères. Il a également été prouvé qu’en incubant des bactéries avec des bionanocomposites ADN-sepiolite, initialement préparés en présence d'une faible concentration en cations divalents et avec de la sépiolite traitée aux ultrasons (sSep), il était possible d'augmenter l'efficacité de la transformation bactérienne 20 à 30 fois par rapport aux méthodes basées sur l'«effet Yoshida». En outre, nous montrons que l'efficacité du transfert de gènes par la sépiolite peut être optimisée : l'utilisation de sSep et l'exposition à la chloroquine augmentent d’un facteur 100 et 2, respectivement, l’efficacité de transfection. Ces résultats ouvrent la voie à l'utilisation de bionanocomposites à base de sépiolite comme de nouveaux potentiels nano-transporteurs hybrides potentiels, à la fois pour la thérapie génique et le développement de nouveaux modèles biologiques en sciences fondamentales et appliquéesAmong the various clay minerals, sepiolite, which is a natural fibrous silicate, isa potential promising nanocarrier for the non-viral transfer of bio-molecules. Indeed,sepiolite has been shown to interact with biological molecules such as lipids,polysaccharides and proteins. Here, we show that sepiolite efficiently binds differenttypes of DNA molecules (genomic, plasmid, single strand and double strandoligonucleotides), introducing the first detailed study on the interaction mechanismsbetween sepiolite and DNA, as well as the physicochemical characterization of theresulting DNA-sepiolite bionanocomposites. The interaction mechanisms aresuggested to be electrostatic interactions, van der Waals forces, cation bridges, andhydrogen bonding. Spectroscopy analysis showed that the binding of DNA to sepiolitewas increased by polycations with valence dependent efficiency, and the DNApreviously adsorbed could be recovered with an efficiency that could be modulatedusing a chelating agent (EDTA), preserving the DNA structure and biological activity.Fourier-transform infrared spectroscopy identified the external silanol groups as themain sites of interaction with the DNA. It was proved that it is possible to use sepiolitefor extracting DNA from bacteria, for DNA purification and for purification from bacterialcontamination. By combining fluorescence microscopy, transmission electronmicroscopy (TEM), time-lapse video microscopy and flow cytometry analysis (FACS),we show that sepiolite can be spontaneously internalized into mammalian cells throughboth endocytic and non-endocytic pathways. As a proof of concept, we show thatsepiolite is able to stably transfer plasmid DNA into bacteria and mammalian cells. Itwas also proved that with the incubation of bacteria with the Sep/DNAbionanocomposite initially prepared in the presence of a low concentration of divalentcation, and using sonicated sepiolite (sSep), it is possible to increase the bacterialtransformation efficiency from 20 to 30-fold compared to previously reported methodswhich are based in the “Yoshida effect”. Additionally, we show that the efficiency ofsepiolite-mediated gene transfer can be optimized: the use of sSep and the exposureto the endosome disrupter chloroquine 100-fold and 2-fold stimulated DNA transfectionefficiency, respectively. These results open the way to the use of sepiolite-basedbionanocomposites as a novel class of hybrid nanocarriers for both potential genetherapy and the development of novel biological models of interest for academic andapplied sciences
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GUADARRAMA, REYES SARAI CARMINA 259233, et REYES SARAI CARMINA GUADARRAMA. « Obtención de un bionanocomposito con nanopartículas biogénicas de plata, para ser utilizado como hilo de sutura ». Tesis de doctorado, Universidad Autónoma del Estado de México, 2018. http://hdl.handle.net/20.500.11799/94835.
Texte intégralRésumé :
La ocurrencia de infecciones por la utilización de hilos de sutura a base de fibras naturales, representa en la actualidad, un riesgo evidente a la salud humana, especialmente los hilos de sutura multifilamento, en donde se ha encontrado una acumulación importante de comunidades bacterianas. Además de cuidar los procedimientos durante el acto quirúrgico, y la elección del material adecuado, es importante contar con sustancias o productos que posean un efecto antiséptico, que disminuya el riesgo a contaminación post quirúrgica. Uno de los requisitos más importantes que un material de sutura debe reunir, es el hecho de poseer propiedades físicas, mecánicas, de manejo, biocompatibilidad y efecto antibacteriano. La nanotecnología representa una alternativa para la creación de materiales avanzados que coadyuven a la práctica quirúrgica bucomaxilofacial. El presente trabajo propone la creación de un bionanocomposito que posea un efecto inhibitorio sobre microorganismos patógenos y que sea producido bajo condiciones eco-amigables para aminorar el daño ocasionado a la salud y el impacto ambiental.
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Wallet, Brett. « Structural investigation of silk fibroin-based membranes ». Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51907.
Texte intégralRésumé :
Silk fibroin has created a surge of interest for use as organic material due to its optical transparency, biocompatibility, biodegradability, and excellent physical properties. However, the implementation of silk films and structures into biomedical and sensing devices has been relatively low due to a lack of understanding of the mechanisms involved in such implementation. Increasing need for multifunctional high-performance organic materials has caused an emphasis on the ability of researchers to spatiotemporally pattern and control the structure and consequently functional properties of materials. Silk fibroin displays high potential for use as a controllable biomaterial that can be formed into a myriad of different structures for various applications. By implementation of an aqueous silk solution approach combining various fabrication techniques, several different pristine-silk and silk-composite membranes have been developed to investigate the importance of internal structuring. Different methods of investigation include: 1) incorporation of reinforcing nanoparticles within the silk matrix; 2) neutron reflectivity measurements of ultrathin silk films; 3) film patterning with nanoscale features followed by boundary organized surface mineralization of inorganic nanoparticles. The ultimate goal will be to provide fundamental data assisting in an increased knowledge of silk fibroin-based membranes and the effect of secondary structures on properties of interest.
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Siqueira, Gilberto Antônio De Freitas. « Processing and thermo-mechanical characterization of polymer bionanocomposites reinforced with microfibrillated cellulose and cellulose whiskers ». Grenoble INPG, 2010. http://www.theses.fr/2010INPG0019.
Texte intégralRésumé :
This work describes the use of some Brazilian natural fibers (Sisal, Luffa Cylindrica and Capim Dourado) as sources of cellulose nanowhiskers and microfibrillated cellulose (MFC) for the preparation of polymeric nanocomposites. It proposes a new way of obtaining cellulose nanoparticles and exploits their intrinsic properties. For this purpose two main routes were investigated, namely (i) use of chemically grafted cellulosic nanoparticles reacted with isocyanates and incorporated in a -polycaprolactone (PCL) matrix, and (ii) direct use of cellulose nanoparticles as reinforcement in a natural rubber (NR) matrix. The thermo-mechanical properties were investigated by DSC and DMA. In both cases it was demonstrated that low amounts of fillers provides high mechanical properties when compared to the neat matrix, PCL or NR. The study of crystallization kinetics of PCL and PCL-nanocomposites provided additional information for cellulosic nanofillers acting as nucleating agents accelerating the crystallization process of nanocomposites. Enzymes were also used to prepare such nanoparticles thus yielding nanofillers with different morphologies. As a result, the final NR-nanocomposites showed different mechanical performances and gain in both Young’s and storage modulus with respect to the neat polymeric matrixThis work describes the use of sorne Brazilian natural fibers (Sisal, Luffa Cylindnca and Capim Dourado) as sources of cellulose nanowhiskers and mierofibrillated cellulose (MFC) for the preparation of polymerie nanocomposites. It proposes a new way of obtaining cellulose nanoparticles and exploits their intrinsic properties. For this purpose tvvo main routes were investigated, namely (i) use of cllernically grafted cellulosic nanoparticles reacted with isocyanates and incorporated in a []-polyeaprolactone (PCl) matrix, and (ii) direct use of cellulose nanoparticles as reinforcement in a natural rubber (NR) matrix, The thermo-mechanical properties were investîgated by DSe and DMA. Ln both cases it was dernonstrated that low amounts of fillers provides high mechanical properties when cornpared ta the neat matrix, PCL or NR
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Busse, Marta Julia. « Bionanocomposites of Fe3O4/SiO2 and alginate for magnetic removal of Cr(III) species from water ». Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14196.
Texte intégralRésumé :
Mestrado em QuímicaThe aim of the present work was to study the removal of Cr (III) species from aqueous solutions by adsorption process, using magnetic nanoparticles functionalized with amine groups and with the polysaccharide alginate. Heavy metal pollution is serious environmental and public health problem worldwide. Chromium is one of the most toxic metal endangering human life. Cr(III) is often used in industry which caused water pollution. Therefore, increased interest by the researchers to employ nanomaterials for the removal contamination and explore adsorbents to replace expensive materials, particularly low-cost raw materials such as, residual polymers materials or agricultural by-products. The work included the preparation of magnetic nanoparticles, coating them with amorphous silica shell functionalized with amine groups and the covalent attachment of alginate to the magnetic nanoparticle. The properties of the nanoparticles were assessed by a number of experimental techniques namely x-ray diffraction, infrared spectroscopy, elemental analysis, thermogravimetry and zeta potential measurements. Silica coated magnetic nanoparticles functionalized with amine groups were investigated for the uptake of Cr(III)/EDTA complexes from water, while the nanoparticles attached to the alginate molecules were tested for the removal of aqueous Cr(III) ions. The kinetic results were fitted to models of pseudo first and pseudo second order and the equilibrium adsorption results were adjusted to suitable isotherm models such as Langmuir and Freundlich. The composite nanoparticles revealed affinity to the Cr(III) species. Due to its properties, this new composite nanoparticles may find interesting applications in purification of water.
O objectivo do presente trabalho foi o de estudar a eliminação de Cr (III), a partir de soluções aquosas, por processo de adsorção, utilizando nanopartículas magnéticas funcionalizadas com grupos amina e com o polissacarídeo alginato. A poluição causada por metais pesados está na base de graves problemas de saúde pública e ambientais em todo o mundo. O crómio é um dos metais mais tóxicos, pondo em perigo a vida humana. O Cr (III) é frequentemente usado na indústria, causando a poluição da água. Por esta razão, aumentou o interesse dos investigadores na utilização de nanomateriais para a remoção de poluentes e no estudo de adsorventes para substituir materiais caros, nomeadamente matérias-primas de baixo custo, tais como, materiais provenientes de polímeros residuais ou subprodutos agrícolas. Este trabalho incluiu a preparação de nanopartículas magnéticas, o seu revestimento com uma capa de sílica amorfa funcionalizada com grupos de amina e a ligação covalente do alginato à nanopartícula magnética. As propriedades das nanopartículas foram avaliadas utilizando várias técnicas experimentais nomeadamente difracção de raios-X, espectroscopia de infravermelho, análise elementar, termogravimetria e medições do potencial zeta. As nanopartículas magnéticas revestidas com sílica e funcionalizadas com grupos de amina foram investigadas para a adsorção de Cr (III) / complexos de EDTA de águas, enquanto que as nanopartículas ligadas às moléculas de alginato foram testadas para a remoção de iões Cr (III) em meio aquoso. Os resultados de cinética foram ajustados aos modelos de pseudo-primeira e pseudo-segunda ordem, e os resultados de equilíbrio de adsorção foram ajustados aos modelos adequados, tais como a isotérmica de Langmuir e a de Freundlich. As nanopartículas compósitas revelaram ter afinidade para as espécies de Cr (III). Devido às suas propriedades, estas nova nanopartículas compósitas podem encontrar aplicações interessantes na purificação de águas.
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Nunes, Juliana Carla. « Preparação e caracterização de filmes comestíveis baseados em gelatina, chá-verde e nanoemulsão de óleo essencial de limão / ». Ilha Solteira, 2018. http://hdl.handle.net/11449/156001.
Texte intégralRésumé :
Orientador: Marcia Regina de Moura AouadaResumo: Diante da crescente preocupação com os impactos ambientais relacionados ao uso de polímeros sintéticos, estudos visando à obtenção e aplicação de materiais poliméricos de fontes renováveis vêm aumentando, como por exemplo, o desenvolvimento de filmes comestíveis à base de polímeros naturais. Para a obtenção de filmes comestíveis necessita-se de um material polimérico que forme uma matriz homogênea e contínua. A gelatina é um polímero natural, de fonte abundante, biodegradável e biocompatível e tais características motivam sua utilização como matriz em filmes comestíveis. O uso de extrato de chá-verde e óleo essencial de limão em filmes de gelatina é uma alternativa para melhoria de suas características físicas e organolépticas para uma aplicação inovadora do produto como sachê de chá. Neste contexto, o objetivo do presente estudo foi preparar, caracterizar e avaliar a influência do extrato de chá-verde e da nanoemulsão de limão nas propriedades de solubilidade, mecânicas, térmicas e de permeabilidade ao vapor de água da matriz de gelatina. A nanoemulsão apresentou tamanho médio de 171 ± 3 nm e potencial zeta de -10,9 ± 0,1 mV. Os filmes foram obtidos por casting a partir de soluções filmogênica de gelatina com extrato de chá verde e nanoemulsão de limão. A adição de chá verde ocasionou um aumento da tensão máxima de ruptura do filme de gelatina de 86 ± 7 MPa para 101 ± 5 MPa e quando a nanoemulsão foi adicionada o valor diminuiu para 78 ± 8 MPa. A incorporação de chá-verde e ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In view of the growing concern about the environmental impacts related to the use of synthetic polymers, studies aimed to obtain and apply polymeric materials from renewable sources have been increased, as the development of edible films based on natural polymers. To obtain edible films, a polymeric material is needed to form a homogeneous and continuous matrix. Gelatin is a natural polymer, from an abundant source, biodegradable and biocompatible and such characteristics motivate its use as a matrix in edible films. The use of green tea extract and lemon essential oil in gelatin films is an alternative to improve its physical and organoleptic characteristics for an innovative application of the product as a tea bag. In this context, the objective of the present study was to prepare, characterize and evaluate the influence of the green tea extract and the lemon nanoemulsion on the solubility, mechanical, thermal and water vapor permeability properties of the gelatin matrix. The nanoemulsion had an average size of 170.6 ± 3 nm and a zeta potential of -10.9 ± 0.1 mV. The films were obtained by casting from filmogenic solutions of gelatin with green tea extract and lemon nanoemulsion. The addition of green tea caused an increase in the maximum tensile stress of the gelatin film from 86 ± 7 MPa to 101 ± 5 MPa and when the nanoemulsion was added the value decreased to 78 ± 8 MPa. The incorporation of green tea and nanoemulsion increased the permeability of water vapor and the solu... (Complete abstract click electronic access below)
Mestre
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Pilon, Andrea S. « The Development and Characterization of a Bionanocomposite Tissue Engineering Scaffold Consisting of Poly(lactic acid) (PLA) and Monetite for Bone Regeneration ». University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1278433227.
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Ferreira, Leite Liliane Samara. « Préparation et caractérisation de bionanocomposites à base de protéines et nanocristaux de cellulose par casting continu ». Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI063.
Texte intégralRésumé :
Cette thèse étudie la production et la caractérisation de films bionanocomposites de gélatine-cellulose nanocristaux (CNCs) destinés aux emballages alimentaires multifonctionnels. L’évolutivité des films de gélatine/CNCs a été obtenue par casting continu, et les paramètres rhéologiques des solutions filmogènes et la température de séchage nécessaire pour produire 12 m de film/h ont été établis. Le processus de casting continu s'est avéré avantageux par rapport au processus de casting conventionnel. Les tests de traction, l'analyse thermogravimétrique et l'analyse de perméabilité à la vapeur d'eau ont montré que les films de gélatine/CNCs laminés produits continuellement ont eu une meilleure performance que ceux obtenus par casting conventionnel. Les propriétés physiques et structurelles des gélatine/CNCs modulé par des interactions électrostatiques changés par le pH ont été étudiées. La fonction des CNCs a été étendue avec succès par la fonctionnalisation avec rosin (r-CNCs), qui a produit des nanocharges antimicrobiennes. Des tests de traction et des analyses antimicrobiennes ont montré que les r-CNCs servent d’agent antibactériens dans les films à base de gélatine. Sans cela, les films souffriraient autrement de propriétés physiques et biologiques limitées. L'acide tannique a été utilisé avec succès comme antioxydant et additif antibactérien, comme une autre perspective pour développer le potentiel des films de gélatine/CNCs comme matériel d'emballage. L'acide tannique non oxydé a favorisé les interactions non covalentes et intermoléculaires entre la gélatine, les CNCs et l'acide tannique. Ces interactions physico-chimiques ont montré une plus grande influence sur les propriétés antioxydantes et physiques des films gélatine/CNCs-acide tannique. Cette thèse donne une compréhension globale de la façon dont la CNCs peut être exploitée pour développer des films biodégradables à base de gélatine avec des propriétés améliorées ou des fonctionnalités supplémentaires. Le casting continu a été appliqué afin d’augmenter la production de films de gélatine/CNCs, ce que rend les films hautement souhaitables pour les applications d'emballageThis Ph.D. thesis covers the production and characterization of gelatin-cellulose nanocrystals (CNCs) bionanocomposite films intended for multifunctional food packaging. The up-scalability of the gelatin/CNCs films was attained by continuous casting and the rheological parameters of the film-forming solutions and drying temperature required to produce 12 m film/h were established. The continuous casting processing was proven to be advantageous when compared to the bench solution casting method. Tensile tests, thermogravimetric analysis, and water vapor permeability analysis showed that the continuously cast gelatin/CNCs films had exceptionally better performance than the films obtained by bench casting. The physical and structural properties of the gelatin/CNCs bionanocomposites as tailored by pH-dependent electrostatic interactions were investigated. The suitability of CNCs was successfully extended by functionalization with rosin (r-CNCs), thus giving rise to antimicrobial reinforcing agents. Tensile tests and antimicrobial analysis showed that r-CNCs served as bacterial nanofillers in gelatin-based films, which otherwise would suffer from limited physical and biological properties. Plant-derived tannic acid was successfully used as an antioxidant and bactericidal additive, as another perspective of extending the potential of the gelatin/CNCs films as a packaging material. Non-oxidized tannic acid favored non-covalent interactions and intermolecular connections between gelatin, CNCs, and tannic acid. These physico chemical interactions showed to have a greater influence on the antioxidant and physical properties of gelatin/CNCs/Tannic acid films. This thesis provides a comprehensive understanding of how CNCs can be explored to develop biodegradable films based on gelatin with enhanced properties or extra functionalities. A continuous solution casting was applied for scaling up the production of gelatin/CNCs-based films making them highly desirable for packaging applications
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Dhanasekaran, Swaminathan Puttagounder. « Fabrication and characterization of highly porous peek bionanocomposites incorporated with carbon and hydroxyapatite nanoparticles for scaffold applications ». Diss., Wichita State University, 2013. http://hdl.handle.net/10057/6420.
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Zhou, Mengbo [Verfasser], Thomas [Gutachter] Heinze et Felix [Gutachter] Schacher. « Magnetic bionanocomposites with low melting temperature : fabrication, characterization, and application / Mengbo Zhou ; Gutachter : Thomas Heinze, Felix Schacher ». Jena : Friedrich-Schiller-Universität Jena, 2019. http://d-nb.info/1207272736/34.
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Coativy, Gildas. « Optimisation des propriétés de mémoire de forme de l’amidon : rôle des procédés thermomécaniques et apport de l’introduction de nanocharges ». Nantes, 2013. http://archive.bu.univ-nantes.fr/pollux/show.action?id=dd59b6e5-214f-4120-a9fc-fc73e3210d86.
Texte intégralRésumé :
L’amidon amorphe possède des propriétés de mémoire de forme : une fois déformé à chaud puis refroidi, il peut recouvrer sa forme initiale lors du passage de la transition vitreuse par chauffage ou par absorption d’eau. L’objectif principal de ce travail était d’améliorer les performances mécaniques du matériau lors de la recouvrance de forme. Deux approches ont été étudiées : l’optimisation de la mise en forme du matériau à chaud et l’introduction de nanocharges lamellaires (montmorillonites) dans la matrice par extrusion bi-vis. Le développement de procédés modèles et de méthodes spécifiques de caractérisation, structurale et thermomécanique, a permis l’optimisation de l’élaboration des matériaux et une meilleure compréhension des mécanismes à l’origine de la mémoire de forme et de la contrainte de relaxation. Des composites contenant entre 1 et 10% de nanocharges ont été élaborés à l’aide d’un micromélangeur bi-vis permettant la simulation du procédé d’extrusion. Les meilleurs états de dispersion ont été obtenus sans ajout de surfactant, l’amidon cationique utilisé induisant une agrégation des nanocharges. Les bionanocomposites obtenus présentent une amélioration significative des performances mécaniques sans altération des propriétés de mémoire de forme et avec une amélioration de la contrainte de relaxation. Toutefois un ralentissement de la cinétique de recouvrance de forme est observé, qui pourrait être lié à une modification de la dynamique macromoléculaire en présence des nanocharges, détectée par calorimétrie et par analyse thermomécanique dynamiqueStarch has shape memory properties: after hot forming and quenching, it is able to recover its initial shape by crossing the glass transition, by heating and/or by moisture uptake. The target of the present work is to improve the material’s thermomechanical performances during shape recovery. Two approaches were studied: the optimization of the hot forming process and the introduction of lamellar nanofillers (montmorillonites) in the matrix by twin screw extrusion. Model processes and specific structural and thermomechanical characterization methods allowed optimizing the elaboration process and allowed a better understanding of the shape memory and stress relaxation mechanisms. Composites containing 1 to 10% of nanofillers have been processed using a twin screw microcompounder allowing simulating the extrusion process. The best dispersion states were obtained without addition of a surfactant. Indeed, an aggregation of the nanoparticles was induced by the cationic starch used. The obtained bionanocomposites showed a significant increase of mechanical performances, without decrease of the shape memory properties and with an improvement of the relaxation stress. However, the shape relaxation kinetics appears to be slowed down. This could be related to a modification of the macromolecular dynamics observed in presence of the nanofiller by calorimetry and dynamic mechanical thermal analysis
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Dall'Osso, Nicolò. « Shelf Life Assessment of Fresh Poultry Meat Packaged in Novel Bionanocomposite of Chitosan Incorporated with ZnO nanoparticles synthesized using food industry by-products ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20653/.
Texte intégralRésumé :
Nel settore alimentare viene utilizzata un’elevata quantità di materie plastiche per conservare i prodotti e facilitarne la distribuzione. L’utilizzo di questi polimeri ha un costo ambientale piuttosto elevato, per questo trovare surrogati ecosostenibili diventa sempre più importante.
In questa tesi abbiamo testato l’efficacia del confezionamento di un prodotto altamente deperibile, quale carne di pollo, con un biofilm a base di chitosano. Il chitosano è polisaccaride largamente presente in natura, dotato di caratteristiche chimico-fisiche che permettono l’ottenimento di un film con proprietà meccaniche e di barriera simili ai polimeri tradizionali, oltre a possedere attività antibatterica. Abbiamo realizzato film contenenti chitosano e altri biocomposti, quali montmorillonite, nanoparticelle di ossido di zinco e olio essenziale di rosmarino, per un totale di 6 film con diversa composizione. Tramite analisi microbiologiche e chimico-fisiche abbiamo confrontato l’efficacia dei diversi film prodotti rispetto ad un controllo (carne conservata in un contenitore asettico). Le analisi sono state svolte in doppio, a 0, 3, 7, 10, 15 giorni di conservazione ad una temperatura di 4°C. In diversi film abbiamo ottenuto una riduzione significativa rispetto al controllo (p<0,05) della conta totale dei microrganismi mesofili aerobici (TMAM) e delle Enterobacteriaceae. La rilevazione del pH e dell’acidità titolabile ha fornito risultati in linea a quelli microbiologici. I campioni nel biofilm hanno spesso subito una variazione significativa (p<0,05) dell’umidità rispetto al controllo, a causa dell’elevata permeabilità al vapore acqueo. L’analisi dei TBARS non ha spesso riportato differenze significative rispetto al controllo (p>0,05), e quando presenti, è perché il campione era più ossidato del controllo (p<0,05). Invece, è stato ottenuto un miglioramento significativo (p<0,05) dello Hue angle tra i film e il controllo. I risultati ottenuti forniscono le basi per studi aggiuntivi.
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Mansa, Rola. « Preparation and Characterization of Novel Montmorillonite Nanocomposites ». Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20207.
Texte intégralRésumé :
Clay minerals have historically played a consequential role in human health. While the beginnings were rooted in geophagy, a primitive act of consuming earth, the health-related uses of clay minerals have evolved and diversified over time.
As excipients in pharmaceutical formulations, clay minerals can attribute novel properties onto intercalated compounds. Intercalating oxybenzone, a UV filter, within the interlamellar space of montmorillonite is desirable in order to minimize direct contact with skin. Intercalating resveratrol, a compound known for attributing beneficial effects onto human health, may be advantageous since this compound is susceptible to cis-trans isomerisation. The strategy of using alkylammonium–modified clay was undertaken and proved successful for the intercalation of oxybenzone.
The field of biopolymer/layered silicate nanocomposites is heavily researched for use in a multitude of applications. Novel montmorillonite nanocomposites were prepared with neutral guar gum and cationic guar gum, using an environmentally friendly process and are fully characterized.
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Cuadra, Ramírez Felipe Andrés. « Evaluación in vivo en modelo animal de la capacidad de bionanocompositos a base de nanopartículas de vidrio bioactivo para estimular la regeneración de tejido óseo ». Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/146855.
Texte intégralRésumé :
Trabajo de Investigación Requisito para optar al Título de Cirujano DentistaIntroducción La reparación de tejidos óseos en odontología es una necesidad en distintos tipos de cirugías. Sin embargo, los autoinjertos, aloinjertos y xenoinjertos que existen en el mercado presentan limitada capacidad osteogénica que no siempre permiten obtener resultados clínicos satisfactorios. Por esta razón la ingeniería de tejidos cobra importancia, ya que esta disciplina busca la síntesis de injertos aloplásticos o biomateriales sintéticos, que superen las capacidades regenerativas de los injertos tradicionales. En tesis anteriores, pertenecientes a este mismo proyecto se sintetizaron y evaluaron in vitro bionanocompósitos a base de andamios de quitosano/gelatina (QG) y poliuretano biodegradable (PU), cargados con nanopartículas de cerámicas de vidrio bioactivo (nBG y nMBG). Los resultados concluyeron que estos biomateriales son capaces de inducir la formación de apatita y la diferenciación osteogénica de células madre. El presente trabajo de tesis tiene como objeto evaluar in vivo la capacidad de regeneración de tejido óseo de los mismos bionanocompósitos, utilizando para ello un modelo animal. Hipótesis Bionanocompósitos cargados con nanopartículas de vidrio bioactivo presentan capacidad de regeneración ósea in vivo superior a la presentada por los andamios puros. Objetivo Compar ar l a capaci dad de r egener aci ón ósea in vivo de bionanocompósitos cargados con nanopartículas de vidrio bioactivo respecto a los andamios puros y los controles. Materiales y métodos Los bionanocompósitos a utilizar en este trabajo, fueron preparados y evaluados in vitro en tesis anteriores del presente proyecto. Los bionanocompósitos evaluados fueron: bionanocompósitos de quitosano/ gelatina cargados nanopartículas de vidrio bioactivo (nBG) y nanoesferas de vidrio bioactivo mesoporoso (nMBG) en forma de esponjas porosas (nBG/QGSP/QG- SP) y de y nMBG/QG-SP) y esferas en estado gel (nBG/QG-SF y nMBG/QG-SF) (Cádiz, Covarrubias, y cols., 2015) y el andamio puro DE de quitosano/gelatina sin las nanopartículas (QG-SP). Además se probaron andamios de poliuretano puro (PU) y con nanopartículas de vidrio bioactivo (nBG/PU y nMBG/PU) (Agüero, Covarrubias, 2015). Como referencia de material clínico se utilizó el aloinjerto comercial Puros® Particulate Allograft (Zimmer Dental). Los bionanomateriales se evaluaron in vivo utilizando un protocolo de modelo animal en rata, el cual fue aprobado por el Comité de Bioética sobre Investigación en Animales de la Facultad de Medicina, Universidad de Chile (Protocolo CBA# 0542 FMUCH, Anexo 1). Todo el procedimiento estuvo regido de acuerdo a protocolos del comité de bioética institucional, correspondiente a los cuidados antes, durante y después del procedimiento quirúrgico. Se utilizaron en total 22 ratas (Sprague Dawley) en las cuales se generó un defecto óseo que cumplía con el tamaño crítico del defecto (4 mm) y luego se implantaron un injerto en cada uno. Después de 8 semanas de implantación los animales fueron eutanasiados y se obtuvo muestras de tejido, correspondiente a la zona del defecto óseo en la cual se realizó el injerto. Las muestras de tejidos obtenidas fueron incluidas en resina y caracterizadas mediante análisis con microscopía electrónica de barrido en modalidad backscattering (SEM-BS), análisis elemental con energía dispersiva de rayos X (EDX) y microtomografía computarizada de rayos - x (Micro-CT). Resultados Como era de esperar el defecto óseo sin tratamiento no reparó por sí solo, mientras que todos los biomateriales estudiados presentaron capacidad de estimular la formación de tejido óseo en diferentes grados. En control positivo Puros® reparó con corticales continuas pero de menor espesor. Los bionanocompósitos de nBG/QG-SP presentaron en general corticales continuas, y de espesor similar al resto de las corticales del mismo hueso. Los bionanocompósitos a base de PU presentaron formación de tejido óseo con corticales abombadas, irregulares, con centros de densidad mixta que invaden el espacio medular. Los compósitos de nBG/QG-SF y de nBG/QG-SP fueron quienes presentaron mejor capacidad de estimular la formación de tejido óseo, en términos de cantidad y densidad de hueso formado. Estos materiales presentaron también una capacidad regenerativa mayor que el aloinjerto comercial Puros®. Los resultados demuestran que los materiales con la nanopartícula nBG son más eficientes que aquellos preparados con nMBG lo anterior debido a que nBG posee menor tamaño de partícula (70 nm) y por lo tanto posee mayor tasa de disolución y liberación de iones capaces de inducir la formación de hidroxiapatita. Con respecto al tipo de polímero de los andamios, el QG presentó mejores propiedades que PU, debido principalmente a la mayor biodegradabilidad de QG respecto a PU. Se encontró además que en cuanto los formatos de presentación, esferas en estado gel y esponjas liofilizadas, ambos presentan características favorables y su utilidad dependerá de las características clínicas del defecto que se requiera reparar. Conclusión Todos los bionanocompósitos con vidrio bioactivo fueron capaces de inducir calcificación y reparación de los defectos óseos en modelos animal en ratas, en especial los scaffolds cargados con nBG (nBG/QG-SP y nBG/QG-SF), quiene presentaron resultados superiores incluso que el aloinjerto comercial Puros®.
Adscrito a Proyecto FONDECYT 1130342
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Souza, Josefa Virginia da Silva. « Preparação e caracterização de bionanocompósitos à base de gelatina e magnetita reticulados com sacarose ». Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=3532.
Texte intégralRésumé :
Fundação de Amparo à Pesquisa do Estado do Rio de JaneiroCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Nesta dissertação, foram estudadas a preparação e a caracterização debionanocompósitos à base de gelatina e magnetita. Sacarose foi empregada comoagente de reticulação e gelatina tipo A e gelatina tipo B foram comparadas nautilização para a preparação das microesferas por meio de emulsão água-em-óleo.As microesferas foram caracterizadas por VSM, DSC, TGA, FTIR, testes deinchamento, espectroscopia de absorção atômica, microscopia ótica e microscopiaeletrônica de varredura. Um planejamento de experimentos variando-se aconcentração de gelatina e de sacarose, a temperatura e a velocidade de agitaçãofoi realizado a fim de encontrar quais parâmetros influenciam o diâmetro dasmicroesferas. A concentração de gelatina e velocidade de agitação foram osparâmetros diretamente associados com os tamanhos de partículas. A distribuiçãode tamanho das partículas revelou que o diâmetro das microesferas variou de 5 a 60micrômetros, com predominância na faixa de 11 a 30 micrômetros. A extensão dareticulação foi aumentada com o aumento do tempo de aquecimento na etapa depreparação das microesferas. Todos os bionanocompósitos apresentaramsuperparamagnetismo. Os resultados mostraram que não há diferença significativa entre a utilização de gelatina do tipo A e gelatina do tipo B. Além disso, o estudo de reticulação degelatina revelou que, ao contrário do que diz a literatura, a sacarose não é umagente de reticulação para as cadeias proteicas, pois não foram encontradasevidências de uma reação química entre a sacarose e gelatina
The preparation and characterization of microbeads based on gelatin and magnetite are reported. Sucrose was employed as crosslinking agent and type A gelatin and type B gelatin were compared for preparation of microspheres by water-in-oil emulsion. The microbeads were characterized by VSM, DSC, FTIR, swelling ratio, atomic absorption spectroscopy and optical and scanning electronic microscopy. The influence of gelatin and sucrose concentration, temperature and stirring speed on the microbeads characteristics was studied. The gelatin concentration and stirring speed were the parameters directly associated with the particle sizes. The particle size distribution revealed that the diameter of the microspheres ranged from 5 to 60 micrometers, with predominance in the range from 11 to 30 micrometers. The extent of cross linking increased as a function of preparation heating time periods. The microbeads presented superparamagnetism. The results show that have no significant difference between the utilization of type A gelatin and type B gelatin. In addition, the gelatin crosslinking study revealed that sucrose is not a crosslinking agent because there was no evidence of chemical reaction between sucrose and gelatin
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Silva, Ingrid Souza Vieira da. « Nanocompósitos de pectina reforçados com nanocristais de celulose para utilização como revestimentos para morangos ». Universidade Federal de Uberlândia, 2015. https://repositorio.ufu.br/handle/123456789/17438.
Texte intégralRésumé :
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorIn this work, the effects of the incorporation were valued of cellulose nanocrystals of the wood pulp of Eucalyptus urograndis from three different times of acid hydrolysis (20, 50 and 80 minutes) in order to determine which of three types of nanocrystals would be most appropriate in the reinforcement function for the matrix of apple pectin. The films were characterized using dynamic mechanical thermal analysis to choose the best reinforcement element in terms of improvement in mechanical properties. After choosing the appropriate filler, new nanocomposites were produced with the percentages of 1, 2, 4 and 8% w/w in relative to the final mass of 0.5 g of each nanocomposite film. The films were manufactured by casting method, in the presence and absence of glycerol as plasticizer in the formulations. These nanocomposite films were characterized using the techniques of water vapor permeability and gases, with the aim of evaluating the barrier properties, contact angle with water in order to verify the hydrophillicity of the material, and dynamic mechanical thermal analysis for evaluating mechanical properties. The nanocrystals extracted with fifty minutes hydrolysis (NC50) were the ones that stood out in terms of improvement in mechanical properties, due to the significant increase in the values of E\'. The nanocomposite films acted as a barrier to passage of gases due to its dense structure, without pores and homogeneous. The formulations of the nanocomposite films with 8% w/w of cellulose nanocrystals in the absence and presence of glycerol were used for coating of strawberries, the comparatives were made with poly (vinyl chloride) film, in relation to weight loss (%) and texture analysis in terms of Puncture Strength the film and Puncture deformation suffered by them. The results showed that the nanocomposite films with glycerol and poly (vinyl chloride) showed comparable values in terms of weight loss, and the glycerol incorporation provided a gain in flexibility of these films. Additionally this same formulation was used in the formulations of the edible coatings and the incorporation of essential oil of lemon grass in the formulations, in order to study the antifungal potential of this compound for coating strawberries. The formulation (18.20 mL of suspension the cellulose nanocrystals fifty minutes, NC50, 230 mL of suspension of apple pectin, 0.50 mL glycerol and 0.12 mL of essential oil of lemon grass) whose processes of immersion were performed twice. This formulation, was the one that stood out in terms of reduction of weight loss, around 5% for the strawberry coated with this formulation and on the other hand 12% for uncoated, analyzed in the time of two days, time that these fruits should be consumed when fresh and stored under satisfactory conditions. So with this work it was observed that the addition of cellulose nanocrystals acted as reinforcement elements for the matrix in the study, these films are hydrophilic and acted as a barrier to passage of gases. The addition of glycerol causes changes in mechanical, thermal and barrier properties of the nanocomposites. According to applicability tests the same base formulation can be used in two different perspectives: coating strawberries in the form of films and as ingredients for preparing the edible coatings to extend shelf life of these fruits which have an extremely short life-time due to rapid metabolism thereof.
Neste trabalho, foram avaliados os efeitos da incorporação de nanocristais de celulose da polpa de madeira de Eucalyptus urograndis a partir de três tempos distintos de hidrólise ácida (20, 50 e 80 minutos) a fim de determinar qual dos três tipos de nanocristais seria o mais adequado na função de reforço para a matriz de pectina de maçã. Os filmes foram caracterizados utilizando análise térmica dinâmico mecânica, para a escolha do melhor elemento de reforço em termos de melhora nas propriedades mecânicas. Após a escolha do elemento de reforço mais adequado, novos nanocompósitos foram produzidos com as percentagens de 1, 2, 4 e 8% m/m em relação à massa final de 0,5 g de cada filme nanocompósito. Os filmes foram obtidos através do método de casting, na presença e na ausência de glicerol como plastificante nas formulações. Estes filmes nanocompósitos foram caracterizados através das técnicas de permeação aos vapores de água e a gases, com intuito de se avaliar as propriedades de barreira, ângulo de contato em água a fim de verificar a hidrofilicidade dos materiais, e análise térmica dinâmico mecânica para avaliação das propriedades mecânicas. Os nanocristais extraídos com cinquenta minutos de hidrólise (NC50) foram os que mais se destacaram em termos de melhora em propriedades mecânicas, devido ao aumento significativo nos valores de E‟. Os filmes nanocompósitos atuaram como barreira a passagem de gases, devido a sua estrutura densa, homogênea e sem poros. As formulações dos filmes nanocompósitos com 8% m/m de nanocristais de celulose na ausência e na presença de glicerol foram utilizados no revestimento de morangos, e os devidos comparativos foram feitos com o filme de policloreto de vinila, com relação à perda de massa (%) e análise de textura em termos de força máxima para a perfuração dos filmes, bem como a deformação sofrida pelos mesmos. Os resultados mostraram que os filmes nanocompósitos com glicerol e policloreto de vinila apresentaram valores comparáveis em termos de minimização de perda de massa, e a incorporação do glicerol proporcionou um ganho em flexibilidade destes filmes. Adicionalmente esta mesma formulação foi usada nas formulações dos revestimentos comestíveis, além da incorporação do óleo essencial de capim-limão as formulações com a finalidade de estudar a potencialidade antifúngica deste composto para revestir morangos. Os devidos comparativos foram feitos com os morangos não revestidos. A formulação (18,20 mL de suspensão de nanocristais de celulose, NC50, 230 mL de suspensão de pectina de maçã, 0,50 mL de glicerol e 0,12 mL de óleo essencial de capim-limão) cujos processos de imersão foram realizados por duas vezes. Sendo esta, a que mais se destacou em termos de redução de perda de massa em torno de 5% para o morango revestido com esta formulação e em contrapartida 12% para o não revestido, analisados no tempo de dois dias, tempo esse que estes frutos devem ser consumidos quando in natura e armazenados sob condições satisfatórias. Assim, com este trabalho foi possível observar que a adição de nanocristais de celulose atuou como elementos de reforço para a matriz em estudo, os filmes são hidrofílicos e atuaram como barreira a passagem de gases. A adição de glicerol provocou alterações nas propriedades mecânicas, de barreira e térmica dos nanocompósitos. E diante dos testes de aplicabilidade, uma mesma formulação base pode ser empregada em duas perspectivas distintas: para revestir morangos na forma de filmes e como ingredientes para o preparo dos revestimentos comestíveis, a fim de se estender o tempo de prateleira destes frutos que é extremamente curto, devido ao metabolismo acelerado dos mesmos.
Mestre em Química
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Silva, Nuno Hélder da Cruz Simões. « Production of protein nanofibers and their application in the development of innovative materials ». Doctoral thesis, Universidade de Aveiro, 2018. http://hdl.handle.net/10773/23348.
Texte intégralRésumé :
Doutoramento em Engenharia QuímicaAs nanofibras proteicas, também conhecidas como fibrilas amilóide, estão a ganhar muito interesse devido às suas propriedades únicas, nomeadamente elevada resistência mecânica e propriedades funcionais. Estas nanofibras caracterizam-se por depósitos proteicos que resultam de um processo onde a molécula proteica adquire uma conformação estrutural em folhas-β. Dadas as suas propriedades, estas nanofibras têm sido estudadas como elementos estruturais e funcionais no desenvolvimento de materiais inovadores para aplicação em diferentes áreas como, por exemplo, em biosensores, membranas bioactivas e estruturas tridimensionais (scaffolds) para engenharia de tecidos. No entanto, uma das principais limitações na exploração de nanofibras proteicas está relacionada com o tempo necessário para a sua produção, uma vez que a fibrilação é um processo moroso que pode levar horas, dias ou até mesmo semanas. A utilização de solventes alternativos como agentes promotores de fibrilação, nomeadamente líquidos iónicos (ILs), foi recentemente demonstrada como uma via para reduzir o tempo de fibrilação. Estes resultados serviram de inspiração para estudarmos o processo de fibrilação de uma proteína modelo, a lisozima, em soluções aquosas de líquidos iónicos baseados nos catiões imidazólio ou colina com diferentes aniões derivados de ácidos orgânicos. A presença de qualquer um dos ILs testados no meio de fibrilação demonstrou ser muito eficiente obtendo-se taxas de conversão superiores a 80% de fibrilas. Seguindo uma abordagem semelhante, estudou-se também um solvente eutéctico profundo (DES) baseado em cloreto de colina e ácido acético (1:1) como possível promotor da fibrilação da lisozima, diminuindo-se o tempo de fibrilação de 8-15 h para apenas 2-3 h. Foi também demonstrado que a temperatura tem um papel fundamental na aceleração da fibrilação e tanto a temperatura como o pH influenciam significativamente as dimensões das nanofibras, nomeadamente em termos de comprimento e largura. Com o objectivo de ajustar a razão de aspecto das nanofibras (razão comprimento/largura), foram ainda estudados vários DES baseados em cloreto de colina e com ácidos mono-, di- e tri-carboxílicos, tendo-se observado que o ácido carboxílico do DES desempenha um papel fundamental no comprimento das nanofibras produzidas, sendo as razões de aspecto sempre superiores às obtidas por fibrilação apenas com cloreto de colina. O potencial das nanofibras proteicas como elementos de reforço em materiais compósitos foi avaliado pela preparação de filmes nanocompósitos à base de pululano com nanofibras de lisozima em diferentes proporções. Foram obtidos filmes transparentes com maior resistência mecânica à tracção, particularmente para as nanofibras com razões de aspecto mais elevadas. Além disso, a incorporação de nanofibras de lisozima nos filmes de pululano conferiu propriedades bioativas aos filmes, nomeadamente capacidade antioxidante e atividade antibacteriana contra a Staphylococcus aureus. O aumento do conteúdo de nanofibras nos filmes promoveu um aumento das propriedades antioxidante e antibacteriano dos filmes, sugerindo-se como possível aplicação a utilização destes nanocompósitos como filmes comestíveis e ecológicos para embalagens alimentares bioactivas. As nanofibras de lisozima foram também misturadas com fibras de nanocelulose com o objectivo de produzir um filme sustentável para a remoção de mercúrio (II) de águas naturais. Os filmes foram obtidos por filtração sob vácuo e mostraram-se homogéneos e translúcidos. A incorporação das nanofibras de lisozima nos filmes de nanocelulose promoveu um reforço mecânico significativo. Em termos da capacidade de remoção de mercúrio (II) a partir de água natural, a presença das nanofibras de lisozima proporcionou um aumento muito expressivo com eficiências de 82% (pH 7) < 89% (pH 9) < 93% (pH 11), utilizando concentrações de mercúrio (II) de acordo com o limite estabelecido nos regulamentos da União Europeia (50 μg L-1). Em suma, foi demonstrado nesta tese que o uso de líquidos iónicos e de solventes eutécticos profundos assume um papel fundamental na formação de nanofibras de lisozima morfologicamente alongadas e finas, que podem ser exploradas no desenvolvimento de bionanocompósitos para diversas aplicações desde embalagens bioactivas a sistemas de purificação de água.
Protein nanofibers, also known as amyloid fibrils, are gaining much attention due to their peculiar morphology, mechanical strength and functionalities. These nanofibers are characterized as fibrillar assemblies of monomeric proteins or peptides that underwent unfolding-refolding transition into stable β-sheet structures and are emerging as building nanoblocks for the development of innovative functional materials for application in distinct fields, for instance, in biosensors, bioactive membranes and tissue engineering scaffolds. However, one of the main limitations pointed out for the exploitation of protein nanofibers is their high production time since fibrillation is a time-consuming process that can take hours, days, and even weeks. The use of alternative solvents, such as ionic liquids (ILs), as fibrillation agents has been recently reported with considerable reduction in the fibrillation time. This fact encouraged us to study the fibrillation of a model protein, hen egg white lysozyme (HEWL), in the presence of several ILs based on imidazolium and cholinium cations combined with different anions derived from organic acids. All ILs used were shown to fibrillate HEWL within a few hours with conversion ratios over than 80% and typically worm-like nanofibers were obtained. In another study, a deep eutectic solvent (DES) based on cholinium chloride and acetic acid (1:1) was studied as a possible promoter of HEWL fibrillation, and a considerably reduction of the fibrillation time from 8-15 h to just 2-3 h was also observed. Temperature has a key role in the acceleration of the fibrillation and both temperature and pH significantly influence the nanofibers dimensions, in terms of length and width. In what concerns the nanofibers aspect-ratio, several DES combining cholinium chloride and mono-, di- and tri-carboxylic acids were studied. It was observed that carboxylic acid plays an important role on the length of the nanofibers produced with aspect-ratios always higher than those obtained by fibrillation with cholinium chloride alone. The potential of the obtained protein nanofibers as reinforcing elements was evaluated by preparing pullulan-based nanocomposite films containing lysozyme nanofibers with different aspect-ratios, resulting in highly homogenous and transparent films with improved mechanical performance, particularly for the nanofibers with higher aspect-ratios. Furthermore, the incorporation of lysozyme nanofibers in the pullulan films imparted them also with bioactive functionalities, namely antioxidant capacity and antibacterial activity against Staphylococcus aureus. The results showed that the antioxidant and antibacterial effectiveness increased with the content of nanofibers, supporting the use these films as, for example, eco-friendly edible films for active packaging. Lysozyme nanofibers were also blended with nanocellulose fibers to produce a sustainable sorbent film to be used in the removal of mercury (II) from natural waters. Homogenous and translucent films were obtained by vacuum filtration and the incorporation of these nanofibers in a nanocellulose film promoted a considerable mechanical reinforcement. In terms of the capacity to remove mercury (II) from natural water, the presence of lysozyme nanofibers demonstrated to increase expressively the mercury (II) removal with efficiencies of 82% (pH 7) < 89% (pH 9) < 93% (pH 11), using realistic concentrations of mercury (II) under the limit established in the European Union regulations (50 μg L-1). In sum, it was demonstrated in this thesis that the use of ionic liquids and deep eutectic solvents can accelerate the formation of long and thin lysozyme nanofibers that can be explored as nanosized reinforcing elements for the development of bionanocomposites with applications ranging from food packaging to water purification systems and nanotechnology
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Nevena, Vukić. « Strukturiranje kompozitnih materijala na osnovu poli(laktida) i ugljeničnih nanocevi ». Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=111137&source=NDLTD&language=en.
Texte intégralRésumé :
U ovom radu, izvršena je sinteza i karakterizacija bionanokompozitnih materijala na osnovu poli(laktida) i višeslojnih ugljeničnih nanocevi. Ispitivan je uticaj različitih tehnika funkcionalizacije nanocevi, kao i izbor uslova sinteze i odnosa polaznih komponenti sistema, na svojstva dobijenih kompozitnih materijala na osnovu poli(L-laktida). Radi postizanja uniformne raspodele nanopunila u kompozitima, višeslojne ugljenične nanocevi su modifikovane hemijskom i radijacionom funkcionalizacijom. Izvršena je karakterizacija ugljeničnih nanocevi, sa ciljem utvrđivanja uspešnosti primenjenih tehnika modifikacije na njihova svojstva i stepen funkcionalizacije. Metodom in situ polimerizacije L-laktida sa površina modifikovanih nanocevi, pripremljene su serije uzoraka kompozitnih materijala sa različitim sadrţajem funkcionalizovanih nanocevi. Detaljno je ispitan uticaj funkcionalizovanih nanocevi na toplotna, kristalna, morfološka, mehanička i električna svojstva sintetisanih kompozitnih materijala. Postignuta homogena disperzija nanocevi unutar biorazgradive, biokompatibilne matrice polimera koji se dobija iz obnovljivih sirovina, uticala je na poboljšanje svojstava, kao i na uspostavljanje novih funkcionalnosti dobijenih materijala. Značajno poboljšanje toplotnih i mehaničkih svojstva sintetisanih materijala, zajedno sa postignutom električnom provodljivošću, omogućava proširenje oblasti primene kompozita na osnovu poli(laktida) i ugljeničnih nanocevi.In this thesis, bionanocomposites based on poly(lactide) and multi-walled carbon nanotubes were synthesized and characterised. Poly(L-lactide) was used as a matrix for the composite synthesis; the influence of nanofillers content, the methods of their functionalization, as well as the synthesis parameters, on the properties of obtained materials were investigated. In order to achieve a uniform dispersion of nanofillers in composite materials, multi-walled carbon nanotubes were modified using chemical and radiation functionalization. Characterization of carbon nanotubes was performed in order to determine the influence of applied modification techniques on their properties and degree of functionalization. A series of composite materials with different content of modified nanotubes were prepared by in situ polymerization of L-lactide from the surface of functionalized nanotubes. The influence of functionalized nanotubes on the thermal, crystal, morphological, mechanical and electrical properties of synthesized composites was investigated in detail. The homogeneous dispersion of carbon nanotubes within the biodegradable, biocompatible, biobased polymer matrix, has influenced the improvement of the properties, as well as the acquiring of new functionalities of synthesized materials. The significant improvement of thermal and mechanical properties of composites, and the achievement of its electrical conductivity, allow the field of application of composites based on poly(lactide) and carbon nanotubes to be expanded.
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Guzmán, Sierra Dayana Lizethe. « Flexible piezoelectric bionanocomposites for biomedical sensors ». Master's thesis, 2018. http://hdl.handle.net/10773/25894.
Texte intégralRésumé :
In recent decades, there has been increasing interest in the development of new materials in order to achieve the "Internet of Things (IoT)" which provided for the connection of 20 to 30 billion devices to the Internet by 2020. The implementation of the "Internet of Things "requires the development of base technology, which includes transducers, actuators and sensors. Sensors are often used in biomedical applications that require flexibility, biocompatibility and sustainability. In this context, the motivation of this work was the preparation of a bionanocomposite for biocompatible piezoelectric sensors for biomedical applications. Thus, a polysaccharide that have the ability to form films (films), and particles of barium titanate which is ferroelectric and piezoelectric material at room temperature, having no lead in its composition.
The BaTiO3 particles were synthesized by hydrothermal method at moderate temperature (200 °C) and in the absence of organic solvents. Several reaction times were studied in order to select the ideal conditions for the particles preparation with the required properties to be incorporated in the chitosan-based films. The structural characterization by X-ray diffraction (XRD) and Raman spectroscopy allowed us to verify that the particles synthesized at 200 °C showed a well-defined tetragonal crystallographic structure after 24 hours of synthesis. The particles showed uniformed cubic morphology and average size of about 306 nm. In general, particle and crystallite sizes increase with reaction time. The films were obtained by the solvent evaporation method, after dispersing the particles in different proportions, in a solution of chitosan. Structural properties (XRD) and morphological (SEM); physical-chemical (mechanical, degree of humidity, solubility in water and contact angle, and Raman); and electrical (dielectric behavior, hysteresis curves and nanoscale piezoelectric response) of the films were characterized. The addition of particles improved the mechanical properties of the chitosan films, making them more resistant, elastic and ductile. These films have also been shown to be more resistant to water, which reveals that there is an interaction between the particles and the chitosan matrix. In relation to the electric behavior of the films, the increase of particles improves the permittivity of the samples five times in relation to the biopolymer material. It was verified a great difficulty of deposition of electrodes in the flexible films that can be justified on the basis of the characteristics of the samples and / or the inadequacy of the experimental conditions of deposition of the electrodes in the sample. It was not possible to measure the piezoelectric response at the macroscopic scale nor to polarize an area of the bionanocomposite sample. Thus, the piezoelectric response at the nanometric scale was studied by atomic microscopy of piezoelectric response. It was found that nanocomposite films with the highest concentration of nanoparticles clearly showed piezoelectric domains, but it is not possible to obtain an acceptable hysteresis curve and to polarize a small area of the nanocomposite. These observations, together with the analysis by surface potential microscopy of the control film (chitosan only) that indicates the presence of charges in the pure polymer, lead to the conclusion of an electret type behavior, being necessary a strategy to eliminate (or reduce) the matrix's contribution.
Despite the difficulties encountered due to degree of innovation of the work, the bionanocomposites developed based on chitosan and barium titanate are promising to be used in biomedical devices (drug release pads, etc.) since they have high mechanical resistance, elasticity, and ductility, as well as have higher resistance to conditions with high degree of humidity. In addition, they are biocompatible and partially biodegradable, being an excellent alternative to synthetic polymersNas últimas décadas, tem havido um interesse crescente no desenvolvimento de novos materiais com o intuito de alcançar a "Internet of Things (IoT)" que prevê a ligação de 20 a 30 bilhões de dispositivos à internet até 2020. A implementação da “Internet of Things” exige o desenvolvimento de tecnologia base, onde se incluem os dispositivos de captação de energia, atuadores e sensores. Os sensores são muitas vezes utilizados em aplicações biomédicas que exigem flexibilidade, biocompatibilidade e sustentabilidade. Neste contexto, a motivação deste trabalho foi a preparação de um bionanocompósito para sensores piezoelétricos biocompatíveis para aplicações biomédicas. Assim, escolheu-se como matriz um polissacarídeo que tem a capacidade de formar películas (filmes) facilmente, e partículas de titanado de bário que é um material ferroeléctrico e piezoeléctrico à temperatura ambiente, não possuindo chumbo na sua composição. As partículas de BaTiO3 foram sintetizadas por método hidrotermal a temperatura moderada (200 °C) e na ausência de solventes orgânicos. Foram estudadas vários tempos de reação de forma a selecionar as condições ideais para a preparação das partículas com as propriedades adequadas para a incorporação nos filmes à base de quitosana. A caracterização estrutural por difração de raios-X (DRX) e espectroscopia de Raman permitiu verificar que as partículas sintetizadas a 200 °C apresentavam, ao fim de 24 horas de síntese, a estrutura cristalográfica tetragonal bem definida. As partículas mostraram morfologia cúbica uniforme e tamanho médio de cerca de 306 nm. Em geral, os tamanhos das partículas e de cristalites aumentam com o tempo de reação. Os filmes foram obtidos pelo método de evaporação de solvente, após a dispersão das partículas, em diferentes proporções, numa solução de quitosana. As propriedades estruturais (DRX) e morfológicas (SEM); físico-químicas (mecânicas, grau de humidade, solubilidade em água e ângulo de contacto e Raman); e elétricas (comportamento dieléctrico, curvas de histerese e resposta piezoelétrica à escala nanométrica) dos filmes foram caracterizadas. A adição de partículas melhorou as características mecânicas dos filmes de quitosana, tornando-os mais resistentes, elásticos e dúcteis. Estes filmes revelaram também serem mais resistentes à água, o que revela que existe uma interação entre as partículas e a matriz de quitosana. Em relação ao comportamento elétrico dos filmes, o aumento de partículas melhora a permitividade das amostras cinco vezes em relação ao material biopolimérico. Foi verificada uma grande dificuldade de deposição de elétrodos nos filmes flexíveis que se pode justificar com base nas características das amostras e/ou na inadequação das condições experimentais de deposição dos elétrodos na amostra. Como não foi possível medir a resposta piezoeléctrica à escala macroscópica, nem polarizar uma área da amostra de bionanocompósito, fez-se o estudo da resposta piezoelétrica à escala nanométrica por microscopia atómica de resposta piezoelétrica. Os filmes com a concentração mais elevada de nanopartículas mostraram claramente domínios piezoelétricos, não sendo, contudo, possível traçar uma curva de histerese aceitável nem polarizar uma pequena área do nanocompósito. Esta observação, juntamente com a análise por microscopia de potencial de superfície do filme controlo (só de quitosana) que indica a presença de cargas no polímero puro, leva à conclusão da existência de um comportamento do tipo electret pelo que será necessário encontrar uma estratégia para eliminar (ou reduzir) a contribuição da matriz. Apesar das dificuldades encontradas, os bionanocompóstos desenvolvidos, à base de quitosana e titanato de bário são promissores para serem usados em dispositivos biomédicos (por exemplo em compressas para libertação de fármacos, etc.) devido à sua elevada resistência mecânica, elasticidade e ductilidade, sendo adaptados a condições de elevado grau de humidade. Estes bionanocompósitos são ainda biocompatíveis e parcialmente biodegradáveis, tendo potencial para serem usados como alternativa aos polímeros sintéticos
Mestrado em Materiais e Dispositivos Biomédicos
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Sureshkumar, Manthiriyappan, et 宋裕民. « MULTIFUNCTIONAL BIONANOCOMPOSITES FROM SUSTAINABLE RESOURCE FOR BIOTECHNOLOGY APPLICATIONS ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/18019246682355060999.
Texte intégralRésumé :
博士國立臺灣科技大學
化學工程系
98
The field of magnetic nanocomposites is fascinating from the aspect of integrating the key features of both polymers and magnetic nanoparticles into an attractive new generation hybrid material. The sustainable biopolymers such as cellulose, chitin and chitosan were used for this study. The synthesis of biopolymers-based magnetic nanocomposites was accomplished through co-precipitation method. Biopolymers homogenized with ferric and ferrous mixture followed by adjusting the homogenate to alkaline pH generates desired nanocomposites. Magnetic-bacterial cellulose (MBC), magnetic chitin (MCT) soaked in dopamine solution will be coated with an adherent self-polymerized multifunctional polydopamine layer on the surface of MBC and MCT. Polydopamine coated magnetic-bacterial cellulose contains multifunctional groups, which acts as a reducing agent for in situ preparation of reusable antibacterial Ag-nanocomposites. The Ag nanocomposite holds a high antimicrobial activity against Escherichia coli and Bacillus subtilis. Its application for in situ fermentation medium sterilization is also demonstrated. Further, polydopamine functionalized MCT also served as α-amylase immobilization matrix, starch hydrolysis efficiency was enhanced over wider pH and temperature ranges. The magnetically retrievable immobilized α-amylase retained over 70% of its original activity after six times of repeated use. Magnetite particles present in the PMBC can also serve as mimic peroxidase and polydopamine surface can immobilize glucose oxidase (GOX) to determine glucose concentration or remove glucose in the solution. MBC and PMBC are showed mimic peroxidase activity over wide pH and temperature range. Further, MBC magnetic-chitosan (MCTS) is modified with resacetophenone (RATP) formed Schiff- base can be utilized as immobilized metal affinity chromatography (IMAC) carrier for model poly-histidine tagged green fluorescent protein (GFP) purification. Likewise, under supercritical carbon dioxide (scCO2) condition ethanolic BC gel also acts as reducing agent to generate silver nanoparticle incorporated in the light-weight BC aerogels.
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Macheca, Afonso. « Preparation and properties characterization of polyamide/clay bionanocomposites ». Thesis, 2016. http://hdl.handle.net/2263/57490.
Texte intégralRésumé :
A novel method for polyamide/clay bio-nanocomposites fabrication was developed in an attempt to facilitate ?extensive delamination? of clay stacks in polyamide matrices. The method, the so-called ?surfactant-free organo-modification approach? did not employ any surfactants for the matrix-clay compatibilisation. The idea was to exploit the use of dimer fatty acid polyamides with protonated amine end groups as clay surface modifiers of the clay previously dispersed in a liquid medium. The clays of choice in the study were the standard smectite clays commonly used to prepare polymer-clay nanocomposites and vermiculite. They were ultimately chosen on the basis of their ability to exfoliate into nano-thick sheets.
Dimer fatty acid polyamide/clay bio-nanocomposites containing either montmorillonite or vermiculite were successfully prepared using the ?surfactant-free organo-modification approach?. Bio-nanocomposites containing as much as 28 wt.% montmorillonite and 30 wt.% vermiculite were obtained. In both cases, the composites featured a mixed morphology containing some exfoliated clay sheets together with nano-sized clay tactoids. At these filler loadings, the melt viscosity, tensile strength and Young?s modulus increased. Dynamic mechanical analysis showed that the glass transition temperature of the polymer increased by as much as 5 ?C when 27.5 wt.% montmorillonite was added and 10 ?C when 30 wt.% vermiculite was added. This indicates that the high interfacial surface area, presented by the clay platelets dispersed in the matrix, significantly impaired the polymer chain mobility. A further goal of the research was to extend the application of organo-modified vermiculite to the semi-crystalline polyamide-11. In this particular case, organomodified- and unmodified vermiculite and commercial sepiolite (Pangel S9) were considered. The clays were melt-compounded into the polyamide-11 to form products that contained either no filler, i.e. neat polyamide-11 or 10 wt.% clay. The aspects that were addressed included the effect of vermiculite organomodification, the effect of the shape of the clays, the aspect ratio of the particles, and the degree of dispersion that was achieved on properties of the generated polyamide-11/bio-nanocomposites. The emphasis was given to the mechanical and flame retardant properties.
Polyamide-11/clay bio-nanocomposites were successfully prepared. Tensile properties results showed improvements in tensile strength and Young?s modulus increased with the presence of the nano-fillers. Young?s modulus of the bio-nanocomposites was almost the double of that of the neat polymer. Thermo-mechanical results also showed improvements in storage modulus with the addition of all particles, especially in the temperature range corresponding to the rubbery plateau (above the glass transition temperature). Cone calorimeter test results showed that the peak heat release rate and smoke production rate values of the polyamide-11/clays significantly decreased compared with those of neat polymer. This indicates that the addition of clays not only decreased the flammability of polyamide but also effectively reduced smoke production.
The key findings of the thesis are:
? The ?surfactant-free organo-modification approach? offers an alternative to conventional clay modification routes based on cationic surfactants. It provides additives suitable for the improvement of the properties of amorphous polyamide matrices.
? The solution casting route allows the preparation of amorphous polyamide/clay nanocomposites with a very high clay content, i.e. approaching 30 wt.%.
? There are at least three stiffening mechanisms operating in amorphous polyamide/clay bio-nanocomposites. The reinforcing effect of the high stiffness inorganic flakes is the primary contributor. Together with the chain confinement effect, that expresses itself in an apparent increase in the glass transition temperature, this provided an adequate rationalisation of the stiffness variation below the glass transition temperature. However, an additional stiffening effect is indicated at temperatures above the glass transition temperature. The mechanism may involve dynamic network formation based on fluctuating hydrogen bonding interactions between the matrix polymer chains and the filler particles.
? From an engineering viewpoint, the good mechanical and fire retardant properties obtained with the vermiculite samples are very encouraging considering the inexpensive nature of this filler.
? The organo-modification of vermiculite and sepiolite is not necessary for the preparation of polyamide-11/clay bio-nanocomposites with excellent mechanical and thermal properties.Thesis (PhD)--University of Pretoria, 2016.
tm2016
Mechanical and Aeronautical Engineering
PhD
Unrestricted
36
Malwela, Thomas. « The study of bionanocomposite thin films and their crystal growth behaviour ». Thesis, 2014. http://hdl.handle.net/10210/12337.
Texte intégralRésumé :
Ph.D. (Chemistry)This study focuses on the morphology and crystal-growth behaviour of polyactide (PLA)-based blends and blends modified with organoclay thin films. The study further examined the effect of blending and the incorporation of organoclays on the enzymatic degradation behaviour. Thin films of unmodified and nanoclay-modified PLA/poly(butylene succinate) (PBS) blends were cast on a glass substrate by a spin coater, while thin films of biodegradable PLA/poly[(butylene succinate)-coadipate] PBSA blends and blends containing organoclays were cast on a silicon (100) wafer substrate. The morphology and crystal growth behaviour of the thin films crystallized at different temperatures were examined with an atomic force microscopy (AFM) equipped with a hot-stage scanner. In PLA/PBS blend thin films, AFM images showed that the size of the dispersed PBS phase was influenced by C30B clay loading on the blends. The dispersed size reduced on the addition of C30B clay up to 2 wt%, beyond which, dispersed size began to increase. Transmission electron microscopy studies indicated that this behaviour was due to the preferential location of silicates in the PBS phase than in the PLA phase. For thin films annealed at 60 °C, the additi on of organoclays to the blend quenched the growth of edge-on lamellae. The crystalline morphologies at 120 °C were dominated by edge-on lamellae grown, around the PBS phase to form spherulites. Morphologies of thin films crystallized at 120 °C from melt were dominated by the flat-on lamellae, while those crystallized at 70 °C from melt were dominated by the edge-on lamellae. In the case of PLA/PBSA blend thin films, the results indicated that the size and distribution of the dispersed phase were directly related to the blend composition. The crystal growth behaviours indicated the presence of homogeneous and heterogeneous nucleations, and the nature of nucleation was directly related to the blend ratio and the temperature at which crystallization occurred. Therefore, this study will facilitate the understanding of crystal growth behaviour in a confined environment and will enable the modulation of the blend properties.
37
Makhado, Edwin. « Poly(ε-caprolactone) based bionanocomposites for food packaging application ». Thesis, 2014. http://hdl.handle.net/10210/11345.
Texte intégral
38
Upadhyay, Rahul Kumar. « Development of Polyethylene Grafted Graphene Oxide Reinforced High Density Polyethylene Bionanocomposites ». Thesis, 2017. http://etd.iisc.ernet.in/2005/3587.
Texte intégralRésumé :
The uniform dispersion of the nano fillers without agglomeration in a polymeric matrix is widely adapted for the purpose of mechanical properties enhancement. In the context to biomedical applications, the type and amount of nanoparticles can potentially influence the biocompatibility. In order to address these issues, High Density Polyethylene (HDPE) based composites reinforced with graphene oxide (GO) were prepared by melt mixing followed by compression moulding. In an attempt to tailor the dispersion and to improve the interfacial adhesion, polyethylene (PE) was immobilized onto GO sheets by nucleophilic addition-elimination reaction. A good combination of yield strength (ca. 20 MPa), elastic modulus (ca. 600 MPa) and an outstanding elongation at failure (ca. 70 %) were recorded with 3 wt % polyethylene grafted graphene oxide (PE-g-GO) reinforced HDPE composites. Considering the relevance of protein adsorption as a biophysical precursor to cell adhesion, the protein adsorption isotherms of bovine serum albumin (BSA) were determined to realize three times higher equilibrium constant (Keq) for PE-g-GO reinforced HDPE composites as compared to GO reinforced composites. In order to assess the cytocompatibility, osteoblast cells (MC3T3) were grown on HDPE/GO and HDPE/PE-g-GO composites, in vitro. The statistically significant increase in metabolically active cell was observed, irrespective of the substrate composition. Such observation indicated that HDPE with GO or PE-g-GO addition (upto 3 wt %) can be used as cell growth substrate. The extensive proliferation of cells with oriented growth pattern also supported the fact that tailored GO addition can support cellular functionality, in vitro. Taken together, the experimental results suggest that the PE-g-GO in HDPE can effectively be utilized to enhance both mechanical and cytocompatibility properties and can further be explored for potential biomedical applications.
39
Tsai, Kai-Hsun, et 蔡凱勛. « Fabrication of array-type glucose sensors using ultrasonic liquid atomizer for sprying γ-APTES/SiO2 bionanocomposite ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/17244784853860831648.
Texte intégralRésumé :
碩士國立暨南國際大學
應用材料及光電工程學系
101
The aim of this thesis focuses on the film deposition of γ-APTES mixed with PDMS-treated silica nanoparticles (NPs) by ultrasonic liquid atomizer for sensor applications, investigating the effects on glucose sensing property of the film in different NPs/γ-APTES weight ratio, different γ-APTES/C2H5OH concentration ratio, and ultraviolet (UV) light exposure. The reason we deposit the γ-APTES+NPs nanocomposite thin film on poly-silicon wire (PSW) by an ultrasonic liquid atomizer is that we might fabricate the glucose sensors array by batch production. We first characterize the surface morphology and measure the vertical leakage current by using atomic force microscopy (AFM). Then, the sensitivity of glucose sensors array is analyzed. It is found that the vertical leakage current of the sensing film increases with NPs/γ-APTES weight ratio in the range of 0% to 1%, and increases with the concentration ratio of (γ-APTES+NPs)/C2H5OH. In comparing the distribution of the values of vertical leakage current, we prove that a uniform γ-APTES+NPs nanocomposite thin film is successfully deposited by using ultrasonic liquid atomizer method. We find that the permance of the batch fabricated glucose sensor array is nearly as good as our previous result which was fabricated by AFM tip coating method. According to our experimental results, the optimal conditions for the glucose detection are 1% weight ratio for NPs/γ-APTES, 1% concentration ratio for (γ-APTES+NPs)/C2H5OH and 120 s for UV exposure. The lowest detection limit is less than 10-9 M, and the linear detection region is from 10-2 M to 10-7 M. Comparing with our previous results, the lowest detection limit and the linear region are nearly the same as the tip-coating method. The sensitivity is about 80% of that tip-coating result. The ultrasonic liquid atomizer spray method can effectively reduce the costs and simplify the process to achieve the goal of a rapid production for large area of sensing membrane.
40
Hsiao, Chi-Lin, et 蕭祺霖. « Fabrication of array-type dopamine sensors using ultrasonic liquid atomizer for spraying γ-APTES/SiO2 bionanocomposite ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72399870932952718484.
Texte intégralRésumé :
碩士國立暨南國際大學
應用材料及光電工程學系
101
The purpose of the thesis is to use the ultrasonic liquid atomizer to spray the sensing membrane of a mixture of 3-aminopropyltriethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs) onto a polysilicon wire (PSW), investigating the characteristics of electrical interference of the PSW in detectingthe nerve substance of dopamine. The ultrasonic liquid atomizer we used might rapidly spray the γ-APTES+NPs onto the PSW with the advantages of large-area production as well as with good uniformity of the film. We used two methods to do the dopamine detections: 1. Using the 4-carboxyphenylboronic acid (CPBA) to modify the surfaces of γ-APTES- or γ-APTES+NPs-coated PSWs. The CPBA molecules were then used as interfacial layer for bonding dopamine molecules (CPBA modification method). 2. Using the tyrosinase to mix with dopamine solution to produce the hydrogen ions. The γ-APTES- or γ-APTES+NPs-coated PSWs were then used to capture the hydrogen ions (tyrosinase conversion method). We found the optimal conditions for sensitivity through changing the weight ratio of NPs/γ-APTES or the volume ratio of (γ-APTES+NPs)/C2H5OH. It was found that, for both the CPBA modification and tyrosinase conversion methods, the optimal conditions for two methods were the same, that is, the weight ratio of the NPs to γ-APTES was 1% and the volume ratio of the γ-APTES+NPs to C2H5OH was 0.2%. For the optimal conditions, the dopamine sensor exhibited the best performance of sensitivity and linear detection region in dopamine detections. For the CPBA modification method, the lowest detection limit is 10-6 M, and the linear region is in the range of 10-3 M ~ 10-6 M. For the tyrosinase conversion method, the lowest detection limit is 10-11 M, and the linear region is in the range of 10-3 M ~ 10-11 M. We found that the tyrosinase conversion method is better than the CPBA surface modification method. Neverthless, both methods can be used for dopamine sensing application. We successfully fabricated the low-cost dopamine biosensor array by batch production using the ultrasonic atomizing for spraying the large–area γ-APTES +NPs membrane with good uniformity.
41
Araújo, David Jefferson Cardoso. « Production of cellulose-based bioplastics from agroindustrial residues ». Doctoral thesis, 2020. http://hdl.handle.net/1822/76361.
Texte intégralRésumé :
Tese de Doutoramento (Gestão e Tratamento de Resíduos)O desenvolvimento de plásticos biodegradáveis e de base biológica desempenham um papel fundamental na transição para uma economia circular, nomeadamente em aplicações de caso único, como embalagens. Esta tipologia de materiais basia-se no uso de matérias-primas renováveis, na possibilidade de reciclagem orgânica e na economia de recursos por reprocessamento. A biomassa lignocelulósica destaca-se como uma fonte promissora de biopolímeros naturais, sendo os resíduos agroindustriais uma fonte atraente devido à sua disponibilidade, baixo custo e alto teor de celulose. Paralelamente, é igualmente importante que os produtos emergentes de base biológica acompanhem as tendências do mercado, nomeadamente no uso de técnicas de processamento ecológicas e no desenvolvimento de materiais com propriedades ativas. No presente trabalho pretendeu-se desenvolver bioplásticos de base celulósica a partir de resíduos agroindustriais. Estes foram identificados com base num diagnóstico e na implementação de um modelo linear, tendo siso selecionado o caroço do milho como matéria prima a estudar. Um pretratamento combinado de dois estágios (tratamento hhidrtérmico seguido da reação com solução diluída de hidróxido de sódio) foi realizado para extrair a sua fração celulósica. A celulose extraída foi utilizada para produção de acetato de celulose atavés de uma técnica acetilação sem a presença de um meio solvente para dissolução. Na síntese do acetato de celulose obteve-se um grau de substituição de 2,68 e um rendimento de 60%. O acetato de celulose produzido apresentou ainda características adequadas para a preparação de filmes com características mecanicas significativas. Avaliação do ciclo de vida foi realizada para contabilizar os impactos ambientais associados à aplicação conjunta das ténicas de pré-tratamento e acetilação. A análise de ciclo de vida mostrou que as técnicas utilizadas repercutiram em impactos ambientais menos significativos que os gerados por abordagens convencionais. Um bionanocompósito foi produzido através da dissolução do acetato de celulose sinterizado em uma suspensão coloidal contendo nanopartículas de dióxido de titânio e óxido de magnesio, obtida a partir da ablação a laserdos metais percussores em diclorometano. A técnica utilizada possibilitou a produção de filmes bioplásticos sem o uso de qualquer outro reagente químico ou geração de subprodutos.
Bio-based and biodegradable plastics play a key role towards the successful transition to a circular economy, namely regarding the application of single-use products, such as packaging. The benefits brought by this class of materials rest on the use of renewable resources of raw-materials, organic recycling and resource-saving by reprocessing. Lignocellulosic biomass stands out as a promising source of natural biopolymers, being the agroindustrial residues are especially attractive alternative due to their availability, low-cost and high cellulose content. On top of that, it is likewise important that the emerged bio-based products keep up with the latest trends on the market, which are focused on the use of eco-friendly processing techniques and development of active materials. In this regard, the present thesis is intended to develop cellulose-based bioplastics from agroindustrial residues. Potential agroindustrial residues were identified based on a diagnosis study and on the implementation of a linear model, from which corncob was selected as the raw material to be studied. A combined two-stage liquid hot water/dilute-NaOH pretreatment was carried out to extract its cellulose content. Furthermore, cellulose acetate (CA), a recognized biodegradable polymer, was synthesized from the extracted cellulose by a solvent-free method using iodine as catalyst. The cellulose acetate synthesis resulted in substitution degree of 2.68 and yield of 60%. The synthesized CA was suitable to produce films with remarkable mechanical properties. A life cycle assessment (LCA) was modeled in order to count the environmental impacts resulting from the joint application of pretreatment/acetylation techniques. The LCA showed that, in response to the less consumption of chemicals and high yield of acetylation, the proposed techniques have environmental impacts less significant than those of conventional approaches. A bionanocomposite was produced via the direct dissolution of the synthesized CA in a colloidal suspension containing titanium dioxide and magnesium oxide, the latter obtained through the laser ablation of bare metal targets in an appropriate solvent. The processing technique used allowed the production of bioplastic films without the use of any other chemical reagent or generation of byproducts.
CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) e ao governo do Brasil pelo suporte financeiro no consentimento da bolsa 201940/2015-9. Obrigada à FCT (Fundação para a Ciência e Tecnologia) pelo apoio financeiro no âmbito dos projetos TSSiPRO (technologies for sustainable and smart innovative products-norte-01-0145-FEDER-000015) e UID/CTM/50025/2019 (UID/EEA/04436/2019 e NORTE-01-0145-FEDER-000018-HAMaBICo).