Two diverse projects illustrate the application of various materials characterization techniques to investigate the structure and properties of nanostructured functional materials formed in both bulk as well as in solutions. In the first project, ordered magnetic nanostructures were formed within polymer matrix by novel metallopolymers. The novel metal-functionalized block copolymers (BCPs) enabled the confinement of cobalt metal ions within nanostructured BCP domains, which upon simple heat treatment resulted in room temperature ferromagnetic (RTFM) materials. On the contrary, cobalt functionalized homopolymer having similar chemical structure and higher loading of metal-ion are unstructured and exhibited superparamagnetic (SPM) behavior at room temperature. Based on a series of detailed investigations, using various materials characterization techniques, it was hypothesized that the SPM cobalt particles within BCP microdomains exhibited a collective behavior due to increased dipolar interactions between them under the nanoconfinement of cylindrical domains in BCP, resulting in RTFM behavior. On contrary, the same SPM cobalt particles formed within homopolymer, without any confinement exhibited SPM behavior either due to lack of interactions or random interactions between them. To further support this hypothesis, a series of BCPs were prepared in which the BCP morphology was varied between the cylindrical, lamellar, and inverted cylindrical phases and their magnetic properties were compared. All these BCPs, which are nanostructured, exhibited RTFM behavior, further supporting the proposed hypothesis. Different dimensionality or degree of nanoconfinement in BCP morphologies affected the magnetization reversal processes in these BCPs, yielding different macroscopic magnetic properties. Most strongly constrained cylindrical morphology has shown best magnetic properties (highest coercivity) among other BCP morphologies. Inverted cylindrical morphology, in which a 3-D matrix is confined between the non-magnetic cylinders, had second highest and lamellar morphology with least confinement among BCPs, exhibited lowest coercivity. The proposed hypothesis was further tested by systematically varying the dipolar interactions between the SPM cobalt nanoparticles by reducing the density of cobalt within the cylindrical domains and varying the dimensions of the cylindrical domains (i.e. diameter). A series of novel ferrocene-cobalt containing block copolymers were developed and cobalt density within the cylindrical domains of BCP was varied by changing the chemical composition of the metal functionalized block. Further, the diameter of the cylindrical domains was varied by varying the molecular weight of the cobalt-containing BCPs. These studies allowed us to understand the fundamental correlations between the self-assembled nanostructures and their macroscopic magnetic properties. In the second part of the thesis, a novel amphiphilic block copolymer (ABC), composed of a hydrophilic zwitterionic block and a hydrophobic PS block, was synthesized by ROMP. The formation of zwitterionic vesicles in an ionic liquid, as well as in PBS buffer, was confirmed by TEM and DLS characterization. The dispersion of vesicles within ionic liquid enabled the usage of conventional, room temperature TEM to visualize them in their solution state. This technique of materials characterization could be extended for the visualization of other hydrophilic soft matter.

Um filme polimérico utilizado na fabricação de curativos adesivos não perfurados deve ter baixo módulo de elasticidade e boa permeabilidade ao vapor d\' água. O baixo módulo de elasticidade garante sensação de maior conforto do produto em contato com a pele quando a pessoa que o está utilizando movimenta a parte do corpo sobre a qual está aplicado o curativo, principalmente a região das articulações, como joelhos e cotovelos. A importância de uma boa permeabilidade ao vapor d\' água está relacionada, principalmente em curativos não perfurados, ao fato de que a pele perde água constantemente e, se o filme polimérico não permitir a saída dessa água ao meio ambiente, ocorrerá um fenômeno denominado maceração, que é a sensibilização excessiva da pele, causada pela hiper hidratação da mesma. O presente trabalho apresenta um estudo da permeabilidade ao vapor d\' água, bem como a caracterização vibracional e térmica de um filme polimérico constituído por três polímeros diferentes, desenvolvido para substituir a poliuretana utilizada atualmente na produção de curativos adesivos não perfurados, com custo inferior. Os polímeros que constituem o filme foram caracterizados separadamente e alguns resultados obtidos, como Tm e a estrutura química dos polímeros Lotader® e Lotryl® foram comparados aos dados fornecidos pelo fabricante. Verificou-se que as propriedades de módulo de elasticidade e permeabilidade ao vapor d\' água do filme desenvolvido são inferiores às da poliuretana inviabilizando a substituição. Entretanto, o trabalho proporcionou um melhor entendimento dos fatores que influenciam o módulo de elasticidade e a permeabilidade do novo material ao vapor d\' água. / A polymeric film must have low elasticity modulus and good water vapor permeation to be used in the production of non perforated adhesive tapes. Low modulus is desirable to provide comfort sensation as the consumer moves the part of his or her body in which the tape is applied on, mainly in the articulations regions, as elbows and knees. The importance of good water vapor permeation is related, mainly in the case of non perforated adhesive tapes with the continuous loss of water by the skin. If the film does not allow the release of the water continuously lost by the skin to the environment, the skin will become very sensitiveness as a result of over hydration. This work presents a study of water permeability and a thermal and vibrational characterization of a polymeric film composed of three different polymers developed to replace the adhesive not perforated polyurethane tape providing lower cost. Besides characterization a test of Water Vapor Transmission Rate (WVTR) was performed. Each polymer present in the film composition was analyzed and the results as Tm and chemical structure of Lotader® e Lotryl® were compared with the producer data. It was verified that the properties of elasticity modulus and water vapor permeability of the new material developed are worse than polyurethane so the substitution can not be performed. However, the work provided a better understanding of the factors that influences the elasticity modulus and water vapor permeability of the new material.

Accurate statistical characterization of nanomaterials is crucial for their use in emerging technologies. This work investigates how different structural characteristics of metal nanoparticles influence the line profiles of the corresponding powder diffraction pattern. The effects of crystallite size, shape, lattice dynamics, and surface strain are all systematically studied in terms of their impact on the line profiles. The studied patterns are simulated from atomistic models of nanoparticles via the Debye function. This approach allows for the existing theories of diffraction to be tested, and extended, in an effort to improve the characterization of small crystallites. It also begins to allow for the incorporation of atomistic simulations into the field of diffraction. Molecular dynamics simulations are shown to be effective in generating realistic structural models and dynamics of an atomic system, and are then used to study the observed features in the powder diffraction pattern. Furthermore, the characterization of a sample of shape controlled Pt nanoparticles is carried out through the use of a developed Debye function analysis routine in an effort to determine the predominant particle shape. The results of this modeling are shown to be in good agreement with complementary characterization methods, like transmission electron microscopy and cyclic voltammetry.

[pt] Nos últimos anos muitos esforços foram realizados para obtenção de materiais capazes de explorar eficientemente a conversão de energia solar. Em particular, a geração de combustíveis por fotocatálise retém grande interesse devido às suas propriedades intrínsecas de promover reações com variação de energia positiva, possibilitando seu armazenamento em compostos químicos. A eficiência desses processos, entretanto, é limitada pela fotoativação dos principais fotocatalisadores no espectro UV, desperdiçando grande parte da energia solar presente no Visível. Neste trabalho foi investigada a influência no desempenho de fotoativação de heteroestruturas de titanatos de Fe e Cu crescidos sobre TiO2 para produção de gás H2 por fotólise da água utilizando luz Visível. As amostras foram preparadas segundo rota por impregnação via úmida e pós-tratamento térmico, em que óxidos metálicos foram formados na superfície de partículas de TiO2 com posterior interdifusão e formação de fases ternárias de Fe2TiO5 e Cu3TiO4. Realizou-se a caracterização dos materiais por meio das técnicas de DRX, DSC, TGA, MEV/EDS, DRS, PLS e Fisissorção de N2. Os resultados obtidos confirmaram a formação dos materiais, sugerindo a criação de heteroestruturas do tipo PN para as amostras contendo Fe e a formação de fase dopada rutilo Cu para as contendo Cu. A atividade fotocatalítica foi avaliada em teste de desempenho realizado em sistema reacional construído na execução do trabalho. Os testes permitiram identificar resultados preliminares promissores de atividade fotocatalítica para as amostras contendo Fe em sua estrutura, que demonstraram uma significativa atividade fotocatalítica no espectro Visível. / [en] In recent years many efforts have been made to obtain materials capable of efficiently exploiting the potential of solar energy conversion. In particular, the generation of fuels by photocatalysis retains great interest due to its intrinsic properties of promoting up-hill reactions, with a positive free energy variation, allowing its storage in chemical compounds. The efficiency of these processes, however, is usually limited by the photoactivation of main photocatalysts in UV spectrum, wasting much of the solar energy present in visible spectrum. This work investigates the influence on photoactivation performance of heterojunctions with Fe and Cu titanate grown on TiO2 for H2 gas production under Visible light by water-splitting. The samples were prepared according route by wet impregnation followed by post-heating treatment, where metal oxides were formed on TiO2 particles surface with subsequent interdiffusion and formation of ternary phases of Fe2TiO5 e Cu3TiO4. The materials were characterized by DRX, DSC, TGA, MEV / EDS, DRS, PLS and N2 Physisorption techniques. The results confirmed the materials sucessful preparation, suggesting the formation of PN-type heterostructures for Fe-containing samples and a rutile-Cu doped phase for Cu-containing samples. The photocatalytic activity was evaluated in a performance test using a photoreactor system built in as part of this work. The tests allowed to identify promising preliminary results for Fe-containing samples, which demonstrated a significant photocatalytic activity in the Visible spectrum.

Um filme polimérico utilizado na fabricação de curativos adesivos não perfurados deve ter baixo módulo de elasticidade e boa permeabilidade ao vapor d\' água. O baixo módulo de elasticidade garante sensação de maior conforto do produto em contato com a pele quando a pessoa que o está utilizando movimenta a parte do corpo sobre a qual está aplicado o curativo, principalmente a região das articulações, como joelhos e cotovelos. A importância de uma boa permeabilidade ao vapor d\' água está relacionada, principalmente em curativos não perfurados, ao fato de que a pele perde água constantemente e, se o filme polimérico não permitir a saída dessa água ao meio ambiente, ocorrerá um fenômeno denominado maceração, que é a sensibilização excessiva da pele, causada pela hiper hidratação da mesma. O presente trabalho apresenta um estudo da permeabilidade ao vapor d\' água, bem como a caracterização vibracional e térmica de um filme polimérico constituído por três polímeros diferentes, desenvolvido para substituir a poliuretana utilizada atualmente na produção de curativos adesivos não perfurados, com custo inferior. Os polímeros que constituem o filme foram caracterizados separadamente e alguns resultados obtidos, como Tm e a estrutura química dos polímeros Lotader® e Lotryl® foram comparados aos dados fornecidos pelo fabricante. Verificou-se que as propriedades de módulo de elasticidade e permeabilidade ao vapor d\' água do filme desenvolvido são inferiores às da poliuretana inviabilizando a substituição. Entretanto, o trabalho proporcionou um melhor entendimento dos fatores que influenciam o módulo de elasticidade e a permeabilidade do novo material ao vapor d\' água. / A polymeric film must have low elasticity modulus and good water vapor permeation to be used in the production of non perforated adhesive tapes. Low modulus is desirable to provide comfort sensation as the consumer moves the part of his or her body in which the tape is applied on, mainly in the articulations regions, as elbows and knees. The importance of good water vapor permeation is related, mainly in the case of non perforated adhesive tapes with the continuous loss of water by the skin. If the film does not allow the release of the water continuously lost by the skin to the environment, the skin will become very sensitiveness as a result of over hydration. This work presents a study of water permeability and a thermal and vibrational characterization of a polymeric film composed of three different polymers developed to replace the adhesive not perforated polyurethane tape providing lower cost. Besides characterization a test of Water Vapor Transmission Rate (WVTR) was performed. Each polymer present in the film composition was analyzed and the results as Tm and chemical structure of Lotader® e Lotryl® were compared with the producer data. It was verified that the properties of elasticity modulus and water vapor permeability of the new material developed are worse than polyurethane so the substitution can not be performed. However, the work provided a better understanding of the factors that influences the elasticity modulus and water vapor permeability of the new material.

Orientador: Antonio Jose Ramirez Londono / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-21T15:16:14Z (GMT). No. of bitstreams: 1 Santos_TiagoFelipedeAbreu_D.pdf: 110699747 bytes, checksum: 6759b8c1d313c0a5ec2220e3fd107447 (MD5) Previous issue date: 2012 / Resumo: Juntas consolidadas a topo com penetração completa, livres de defeitos, foram obtidas usando a técnica de soldagem por atrito com pino não consumível em chapas de 6 mm de espessura para os aços inoxidáveis duplex UNS S32101 e S32205 e os superduplex UNS S32750 e S32760. Testes de dobramento de raiz indicaram a penetração completa e a ausência de trincas bem como inspeção por líquido penetrante. A penetração completa foi atingida quando o aporte energético aumentou de 0,89 kJ/mm para 1,43 kJ/mm. Os testes de tração na junta soldada evidenciaram a falha no MB e o aumento da resistência mecânica da junta associada à uma boa ductilidade, exceto para o UNS S32760. Mapas de dureza mostraram o aumento da dureza em toda junta soldada em relação ao metal de base. Avaliação microestrutural mostrou um pronunciado refinamento do tamanho de grão médio de ambas as fases (ferrita e austenita) na junta soldada para os materiais estudados. A avaliação por microscopia de transmissão indicou a evolução de arranjos celulares formando contornos de grão na ferrita corroborando o mecanismo de recuperação e rescristalização dinâmica contínua. Análise por meio da técnica de EBSD mostrou elevada fração de contornos de grão do tipo 'sigma' na 'gama' indicando a recristalização dinâmica descontínua desta fase. Os AID S32205, S32750, S32760 mostraram sutis alterações na resistência à corrosão para meios com diferentes concentrações de cloretos (3,5% NaCl e 1 M NaCl). Porém, para concentrações mais altas o AISD S32760 exibiu importante decréscimo de resistência a corrosão. Este comportamento foi associado à maior fração de ferrita e a precipitação do nitreto de cromo na junta soldada. O AID S32101 mostrou diminuição da resistência à corrosão na condição como soldado / Abstract: Fully consolidated and full penetration butt joints were produced using friction stir welding (FSW) on 6 mm thick plates of UNS S32101 lean duplex stainless steel (LDSS), S32205 duplex stainless steel (DSS) and S32750 and S32760 superduplex stainless steels (SDSS) with heat input of 1.43 kJ/mm. Liquid penetrant inspection showed the full penetration obtained in the welded joints which was corroborated with the bending tests. Transverse tensile tests of the welded joints failed at the base metal revealing an overmatching weld metal. Moreover, longitudinal tensile tests of the welded joints presented an increase of the yield and tensile strength for all joints together with the elongation, but for UNS S32760, which showed a ductility reduction. Microhardness revealed a hardness increase for all the joints, while the SDSSs presented a more homogeneous hardeness areas of joint. Microstructural evaluation indicated a pronounced grain refinement in the welded joints for all the studied materials achieving down to 1 ?m grain size. Transmission electron microscopy and EBSD indicated dislocation cells evolving towards grain boundaries that corroborates the occurrence of dynamic recovery followed by continuous dynamic recrystallization for ferrite. Austenite exhibited high fraction of high angle grain bondaries associated with 'sigma' boundaries indicating the discontinuous dynamic recrystallization. DSS UNS S32205, SDSS UNS S32750, and S32760 showed good corrosion behavior for 3.5% NaCl and 1 M NaCl environments. However, with the increase of chlorides concentrations, the SDSS UNS S32760 exhibited strong decrease of corrosion performance. This behavior was associated with a combination of high ferrite fraction and chromium nitride precipitation. DSS S32101 exhibited a decrease of corrosion performance when welded / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Dans l’industrie automobile, le véhicule électrique séduit de plus en plus de clients. Ce qui limite sa progression dans le marché est son manque d’autonomie. Une des solutions permettant d’augmenter l’autonomie d’un véhicule est de réduire sa masse en modifiant la géométrie des pièces et les matériaux utilisés. Cependant, de tels changements peuvent avoir des impacts sur la CEM du véhicule.Les travaux de cette thèse portent sur l’étude de l’allègement du blindage des batteries de traction pour véhicule électrique du point de vue de la CEM. Plusieurs méthodes de caractérisation de matériaux sont mises en place dans ce document. Une méthode innovante reposant sur l’utilisation d’une cellule TEM ou d’une stripline a été développée durant ces travaux de thèse, elle permet de mesurer la permittivité relative complexe d’un matériau diélectrique inconnu entre 1 kHz et 1 GHz. Les propriétés électromagnétiques ainsi mesurées sont insérées dans des modèles numériques 3D. Les méthodes numériques adaptées à ce type d’étude sont les différences finies dans le domaine temporel et la méthode des moments. L’étude du rayonnement de la batterie a été effectuée grâce à une maquette à l’échelle ½ en chambre semi-anéchoïque et en chambre réverbérante à brassage de mode selon des montages normatifs. Des configurations plus complexes ont ensuite été étudiées en tenant compte de l’intégration du pack-batterie dans le véhicule. / In automotive industry, electric vehicle is becoming more and more attractive for car buyers. The market penetration of electric vehicle is limited by its short range. One of the solutions to increase the range is to lower the weight of the vehicle by modifying the geometry or the material composition. Nevertheless, such changes may have consequences on the EMC of the vehicle.The work of this thesis concern the study of weight reduction of the battery shield from an EMC point of view. Several methods for materials characterization are set in this document. A method which uses a TEM cell or a stripline has been designed during this thesis to measure the complex relative permittivity of an unknown dielectric material. Then, the measured properties are inserted into numerical 3D models. The numerical techniques that fit this study are the finite differences in time domain and the method of moments. The study of radiated electromagnetic field from a battery has been performed thanks to a ½ scale model in semi anechoic chamber and mode-stirred reverberation chamber according to standard setups. More complex configurations were studied taking into account the integration of the battery-pack into the vehicle.

<div>Metal-zeolites are promising materials for passive adsorber technologies for the abatement of nitrogen oxides (NOx, x = 1,2) and aldehydes during low-temperature operation in automotive exhaust aftertreatment systems. The aqueous-phase exchange processes used commonly to prepare metal-zeolites typically require mononuclear, transition metal complexes to diffuse within intrazeolite pore networks with their solvation shells and replace extra framework cations of higher chemical potential. When metal complexes are larger than the zeolite pore-limiting diameter, this imposes intracrystalline transport restrictions; thus, complexes and agglomerates tend to preferentially deposit near the surfaces of crystallites, requiring post-synthetic treatments to disperse metal species more uniformly throughout zeolite crystallites via solid-state ion-exchange processes. Here, we address the influence of post-synthetic gas treatments and zeolite material properties on the structural interconversion and exchange of extra framework Pd in CHA zeolites with a focus on the thermodynamic, kinetic, and mechanistic factors that dictate the Pd site structures and spatial distributions that form.<br></div><div><br></div><div>Pd-amine complexes introduced via incipient wetness impregnation on CHA zeolites were found to preferentially site near crystallite surfaces. Post-synthetic treatments in flowing air results in Pd-amine decomposition and agglomeration to metallic Pd0and supersequent oxidation to PdO, before converting to mononuclear Pd²⁺cations through an Ostwald ripening mechanism at high temperatures (>550 K). Progressively higher air treatment temperatures (up to 1023 K) were found to (1) thermodynamically favor the formation of mononu-clear Pd²⁺cations relative to agglomerated PdO particles, (2) increase the apparent rate of structural interconversion to mononuclear Pd²⁺, and (3) facilitate longer-range mobility of molecular intermediates involved in Ostwald ripening processes that allow Pd cations to form deeper within zeolite crystallites to form more uniformly dispersed Pd-zeolite materials. Additionally, the controlled synthetic variation of the atomic arrangement of 1 or 2Al sites in the 6-membered ring of CHA was used to show a thermodynamic preference to form mononuclear Pd2+cations charge-compensated by 2 Al sites over [PdOH]⁺complexes at 1 Al site. Colloidal Pd nanoparticle syntheses and deposition methods were used to prepare monodisperse Pd-CHA materials to isolate the effects of Pd particle size on structuralinterconversion to mononuclear Pd²⁺under a range of external environments. Consistent with computational thermodynamic predictions, smaller Pd particle sizes favor structural interconversion to mononuclear Pd²⁺under high-temperature air treatments (598–973 K),while adding H2O to the air stream inhibits the thermodynamics but not the kinetics of mononuclear Pd²⁺formation, demonstrating that water vapor in exhaust streams may be deleterious to the long-term stability of Pd-zeolite materials for passive NOx adsorption.<br></div><div><br></div><div>The influence of metal-zeolite material properties on the adsorption, desorption, and conversion of formaldehyde, a government-regulated automotive pollutant, under realistic conditions was investigated to identify beneficial material properties for this emerging application in mobile engine pollution abatement. A suite of Beta zeolite materials was synthesized with varied adsorption site identity (Brønsted acid, Lewis acid, silanol groups, and extra framework metal oxide) and bulk site densities. All materials stored formaldehyde and converted a large fraction of formaldehyde to more environmentally benign CO and CO₂, demonstrating the efficacy of silanol defects and zeolitic supports for the storage of formaldehyde. Sn-containing zeotypes, containing either Lewis acidic framework Sn sites or extra framework SnO_x particles, resulted in the greatest selectivity to CO and CO₂ formed during formaldehyde desorption, suggests that Sn species are a beneficial component in metal-zeolite formulations for the abatement of formaldehyde in automotive exhaust streams.<br></div><div><br></div><div>This work demonstrates how combining precise synthesis of metal-zeolites of varied bulk and atomic properties with site-specific characterization and titration methods enables systematically disentangling the influence of separate material properties (e.g., Pd particle size, zeolite framework Al arrangement, silanol density, heteroatom identify) and external environment on changes to metal structure, speciation, and oxidation state. This approach provides thermodynamic, kinetic, and mechanistic insights into the factors that influence metal re-structuring under the practical conditions encountered in automotive exhaust after treatment applications and guidance for materials design and treatment strategies to form desired metal structures during synthesis and after regeneration protocols.<br></div>

Tesis por compendio / [EN] In the present Doctoral Thesis, antimicrobial active packaging materials, at lab and at semi-industrial scale, have been developed with the aim to reduce the natural flora of peeled and cut fruit and extend its shelf life. Packaging prototypes have been developed for their further application. Prior to developing the active materials, the most suitable active agents were selected. To that end, the antimicrobial properties of the volatile active agents citral, hexanal and linalool and mixtures thereof were evaluated against typical microorganisms related to fruit spoilage, molds and yeast, concluding that the effectiveness of the mixture is higher than the sum of the effectiveness of the individual agents. Likewise, non-volatile antimicrobial agents such as potassium sorbate and sodium benzoate were selected, which are widely used in the food industry due to their antifungal properties. With the selected active agents, monolayer polypropylene (PP) films with different concentration of the active mixture citral, hexanal and linalool, at lab scale by means of extrusion, and bilayer films at semi-industrial scale with different active layer thickness by means of coextrusion were prepared. Besides, active packaging trays were developed at semi-industrial scale by thermoforming active sheets obtained by coextrusion of PP and ethyl vinyl acetate (EVA) compounds containing potassium sorbate and sodium benzoate as active agents. Mechanical, barrier and thermal properties of the developed active packaging materials, as well as their sealability and transparency were evaluated. In general, the materials' properties were not affected in a significant manner. However, active trays decreased in transparency due to the incorporation of non-volatile active agents. The release kinetics of the volatile and non-volatile active agents were studied at different temperatures, defining their diffusion coefficients by the adjustment to mathematic models based on Second's Law Fick. Among the volatile active agents, hexanal showed a higher diffusion coefficient, followed by citral and linalool. On the other hand, very small differences were observed between potassium sorbate and sodium benzoate diffusion coefficients, being of the same order of magnitude. In vitro tests were also performed at different temperatures to evaluate the antimicrobial properties of the developed materials. In general, the active packaging materials showed high antimicrobial properties which were enhanced with the increment of temperature. Once the properties of the developed materials were evaluated, in vivo tests with peeled and cut orange and pineapple were performed by packing these fruits with the active film, active tray and their combination (active packaging system). In general, the active packaging system improved the microbiological preservation of the fruit for longer times, between 2 and 7 days for orange and pineapple, respectively, and maintained quality parameters of the fruit at stable levels for longer times. Lastly, the safety of the active packaging materials was evaluated according to the European food contact materials and food legislation, and it was concluded that these materials were not of any safety concern for the consumers. / [ES] En la presente Tesis Doctoral se han desarrollado materiales de envase activo antimicrobiano, a escala laboratorio y a escala semi-industrial, con el objetivo de reducir la proliferación de la flora natural de la fruta pelada y cortada y extender su vida útil. Se han desarrollo distintos prototipos para su posterior aplicación industrial Previo al desarrollo de los materiales de envase, se ha realizado una selección de agentes activos más idóneos. Para ello se han estudiado mediante ensayos in vitro las propiedades antimicrobianas de agentes activos volátiles, citral, hexanal y linalool y diferentes mezclas de los mismos, frente a distintos microorganismos típicos del deterioro de las frutas, mohos y levaduras, concluyendo que la efectividad de la mezcla de los tres es superior a la suma de la efectividad de los activos de forma individual. Así mismo, también se han seleccionado antimicrobianos no volátiles como el sorbato potásico y benzoato sódico, los cuáles son ampliamente empleados en la industria alimentaria debido principalmente a sus propiedades antifúngicas. Con los agentes activos seleccionados, se han desarrollado películas monocapa de polipropileno (PP) con distintas concentraciones de la mezcla activa, citral, hexanal y linalool, a escala laboratorio, mediante técnicas de extrusión, y películas bicapa a escala semi-industrial con distintos espesores de capa activa mediante coextrusión. Por otra parte, se desarrollaron bandejas activas a escala semi-industrial mediante termoconformado de láminas obtenidas por coextrusión de compuestos de PP y etilvinilaceteto (EVA) con sorbato potásico o benzoato sódico como agentes antimicrobianos. Se han evaluado las propiedades mecánicas, barrera y térmicas de los materiales activos desarrollados, así como su sellabilidad y transparencia. En general, las propiedades de los polímeros no se vieron afectadas de manera relevante. Sin embargo, las bandejas activas perdieron su carácter transparente debido a la incorporación de los agentes activos no volátiles. Se ha estudiado la cinética de liberación de los compuestos activos volátiles y no volátiles a distintas temperaturas, determinando los coeficientes de difusión de los agentes activos mediante el ajuste a modelos matemáticos de difusión basados en la Segunda Ley de Fick. Entre los agentes volátiles, el hexanal mostró un mayor coeficiente de difusión seguido de citral y linalool. Por otra parte, no hubo apenas diferencia en los coeficientes de difusión del sorbato potásico y benzoato sódico, siendo éstos del mismo orden de magnitud. Igualmente, se han realizado diferentes experimentos in vitro a distintas temperaturas para determinar las propiedades antimicrobianas de los materiales desarrollados. En general, los materiales activos presentan una elevada capacidad antimicrobiana que se ve potenciada al aumentar la temperatura de exposición. Una vez evaluadas las características de los materiales desarrollados, se han efectuado ensayos de envasado de naranja y piña pelada y cortada con las películas y las bandejas activas y con la combinación del sistema de envase bandeja activa termosellada con la película activa. En general, el sistema de envase activo mejoró la conservación de la fruta por un mayor tiempo, entre 2 y 7 días para la naranja y piña, respectivamente, presentando una gran capacidad antimicrobiana y manteniendo los parámetros de calidad de la fruta en niveles estables por un mayor tiempo. Por último, se ha estudiado la seguridad de estos materiales de acuerdo a la legislación de materiales en contacto con alimentos y la legislación alimentaria europea, concluyendo que los materiales activos desarrollados no presentan preocupación para la seguridad de los consumidores. / [CA] En la present Tesi Doctoral s'han desenvolupat materials d'envasament actiu antimicrobià, a escala de laboratori i a escala semi-industrial amb l'objectiu de reduir la proliferació de la flora natural de la fruita pelada i tallada i estendre la seua vida útil. S'han desenvolupament diferents prototips per a la seua posterior aplicació industrial. Previ al desenvolupament dels materials actius, s'han seleccionat els agents actius mes idonis estudiant mitjançant assajos in vitro les propietats antimicrobianes d'agents actius volàtils, citral, hexanal i linalool i diferents mescles dels mateixos, enfront de diferents microorganismes típics de la deterioració de les fruites -floridures i llevats- concloent que l'efectivitat de la mescla dels tres és superior a la suma de l'efectivitat dels actius de forma individual. Així mateix, s'han seleccionat antimicrobians no volàtils, sorbat potàssic i benzoat sòdic, els quals son àmpliament empleats a l'industria alimentaria per les seues propietats antifúngiques. Amb els agents actius seleccionats, s'han desenvolupat pel·lícules monocapa de polipropilè (PP) amb diferents concentracions de la mescla activa, citral, hexanal i linalool, a escala laboratori, mitjançant tècniques d'extrusió, i pel·lícules bicapa a escala semi-industrial amb diferents espessors de capa activa mitjançant coextrusió. D'altra banda, s'han desenvolupat safates actives a escala semi-industrial mitjançant termoconformació de làmines obtingudes per coextrusió de compostos de PP i etil vinil acetat (EVA) amb sorbat potàssic o benzoat sòdic com a agents antimicrobians. S'han avaluat les propietats mecàniques, barrera i tèrmiques dels materials actius desenvolupats, així com la seua sellabilidad i transparència. En general, les propietats dels polímers no es van veure afectades de manera rellevant. No obstant això, les safates actives van perdre el seu caràcter transparent a causa de la incorporació dels agents actius no volàtils. S'ha estudiat la cinètica d'alliberament dels compostos actius volàtils i no volàtils a diferents temperatures, determinant els coeficients de difusió dels agents actius mitjançant l'ajust a models matemàtics de difusió basats en la Segona Llei de Fick. Entre els agents volàtils, l' hexanal va mostrar un major coeficient de difusió seguit de citral i linalool. D'altra banda, no va haver-hi a penes diferències en els coeficients de difusió del sorbat potàssic i benzoat sòdic, sent aquests del mateix ordre de magnitud. Igualment, s'han realitzat diferents experiments in vitro a diferents temperatures per determinar les propietats antimicrobianes dels materials desenvolupats. En general, els materials actius presenten una elevada capacitat antimicrobiana que es veu potenciada en augmentar la temperatura d'exposició. Una vegada avaluades les característiques dels materials desenvolupats s'han efectuat assajos d'envasament de taronja i pinya pelada i tallada amb la safata, la pel·lícula activa i la seva combinació (sistema d'envàs actiu). En general, el sistema d'envàs actiu va millorar la conservació de la fruita per un major temps, entre 2 i 7 dies per a la taronja i pinya respectivament, presentant una gran capacitat antimicrobiana i mantenint els paràmetres de qualitat de la fruita en nivells estables per un major temps. Finalment, s'ha estudiat la seguretat d'aquests materials d'acord a la legislació de materials en contacte amb aliments i la legislació alimentària europea, concloent que els materials actius desenvolupats no presenten preocupació per a la seguretat dels consumidors. / Lara Lledó, MI. (2016). Antimicrobial packaging system for minimally processed fruit [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61388 / TESIS / Premios Extraordinarios de tesis doctorales / Compendio

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