La construction en terre crue constitue une alternative écologique aux bétons de ciment. Afin de promouvoir son usage, la présente étude s’intéresse à la mise au point de bétons de terre coulables permettant une mise en œuvre analogue à celle des bétons usuels. Dans cette optique, il est nécessaire de conférer au matériau une solidification à court terme (24 h) sans attendre son séchage, afin de permettre un débanchage rapide. La voie explorée pour répondre à cette problématique s’inspire de la technique du Gelcasting utilisée dans le domaine des céramiques techniques. Celle-ci s’appuie sur la gélification de polymères préalablement introduits dans une barbotine céramique pour induire une transition liquide-solide rapide et homogène. Une étude bibliographique complétée par des essais préliminaires a mené à la sélection de l’alginate, un polymère biosourcé non toxique et gélifiant à température ambiante sous l’action de cations multivalents tels que le calcium. Ce polymère s’est révélé très prometteur. Il a permis la réalisation d’éprouvettes de mortier démoulables 24 h après coulage et présentant une résistance en compression de l’ordre de 0,1 MPa, théoriquement suffisante à un mur de 3 m de haut pour tenir sous son propre poids. Une preuve de concept à l’échelle du béton a par ailleurs pu être réalisée sous la forme d’un muret de 40 cm de haut coulé et vibré à partir d’une consistance fluide puis décoffrable en 24 h. Les performances mécaniques et hygrothermiques du matériau sec ont été validées, et la présence du polymère gélifié pourrait améliorer la résistance à l’érosion. De premiers essais ont montré que le procédé pouvait être adaptable à des terres moins calcaires que celle utilisée tout au long de l’étude. / Developing raw earthen construction is nowadays a major environmental issue, due to its low embodied energy compared to Portland cement. A solution would be to use a similar process as cement-based concrete, by casting into formworks. Nevertheless, this is limited by technical difficulties, owing to the fact that earth is not a hydraulic binder. In that perspective, this work focuses on inducing a liquid-solid transition to an earth suspension without waiting for drying, similar to cement-based materials. The approach explored to meet this challenge is inspired by the technique of Gelcasting used in the field of technical ceramics. This relies on the gelation of polymers previously introduced into a ceramic slurry to induce a rapid and homogeneous liquid-solid transition. A bibliographic study supplemented by preliminary tests led to the selection of alginate, a biosourced polymer that is non-toxic. Its gelation is allowed at ambient temperature, via addition of multivalent cations such as calcium ions. This polymer proved to be very promising. It made it possible to produce mortar specimens which could be unmoulded 24 hours after casting. A wet compressive strength close to 0.1 MPa could be reached, theoretically sufficient for a wall of 3 meters high to stand under its own weight. A proof of concept at the concrete scale was then realized as a low wall of 40 cm high casted and vibrated and then unmoulded in 24 hours. Mechanical and hygrothermal performances of the dry material were validated, and the presence of the gelled polymer could improve the resistance to erosion. Initial trials showed that the process could be adapted to low calcareous soils.

[pt] Microcápsulas são utilizadas em diversos setores da indústria para isolar o material interno do ambiente externo. Elas protegem o conteúdo interno e permitem uma liberação controlada. Neste trabalho, apresenta-se um método de produção de microcápsulas de goma gelana monodispersas a partir da formação de modelos de emulsão dupla óleo-em-água-em-óleo por microfluídica. A extração do óleo externo, após a gelificação ionotrópica, permite a dispersão das microcápsulas em meios aquosos. Assim, o método proposto permite encapsular ativos hidrofóbicos e dispersar as microcápsulas em uma fase aquosa, tendo diversas aplicações. Foram definidas janelas de operação para produção de microcápsulas de gelana monodispersas em função da vazão volumétrica de cada fluido que forma as microcápsulas e das dimensões do dispositivo microfluídico. Produziu-se microcápsulas com diâmetros variando de 95 a 260 um e um coeficiente de variação máximo de 5 per cent. Os resultados mostram que é possível controlar o diâmetro das cápsulas e a espessura da membrana através das vazões da fase externa e intermediária, respectivamente. Além disso, estudamos o escoamento de cápsulas de gelana com diferentes diâmetros e espessuras de membrana por um capilar com constrição através de imagens microscópicas e medidas de diferença de pressão. Mapeamos as condições nas quais a membrana é rompida devido à constrição e o conteúdo interno é liberado durante o escoamento. A gastroresistência das cápsulas de gelana é verificada através de testes in vitro que simulam as fases gástrica e intestinal da digestão. Mostramos, através de imagens fluorescentes, que as cápsulas são capazes de liberar o conteúdo interno apenas no intestino devido ao seu pH. Finalmente, demonstramos ser possível, não só produzir microcápsulas magnéticas, mas controlar a resposta magnética delas regulando a quantidade de ferrofluido que é adicionada à fase interna ou à membrana polimérica. As microcápsulas produzidas neste estudo têm grande potencial de aplicação em diversos setores, como alimentício, biomédico, farmacêutico e de óleo e gás. / [en] Microcapsules are applied in several sectors of industry when a physical barrier between the core material and the external environment is required. They protect their cargo and ultimately release it in a controlled way. In the present work, microcapsules with hydrogel-based shells are produced. Monodispersed microcapsules are formed by ionotropic gelation of gellan gum from monodispersed oil-in-water-in-oil (O/W/O) double emulsion templates obtained using glasscapillary microfluidic devices. An oil extraction step was added after the shell gelation process to enable the dispersion of the microcapsules in an aqueous medium. We report the operability window for the production of monodispersed microcapsules as a function of the flow rate of each fluid phase and the dimensions of the device. Microcapsules with mean diameters ranging from 95 to 260 um and a maximum coefficient of variation of 5 per cent were formed. The results show how to independently control the capsule diameter and shell thickness by varying the outer and middle phase flow rates. After that, we experimentally investigate the flow of monodispersed gellan gum microcapsules through a constricted capillary tube by measuring the evolution of the pressure difference and flow visualization. The maximum pressure difference and capsule deformation is obtained for capsules with different diameter and shell thickness. We map the conditions at which the capsule membrane ruptures during the flow, releasing its internal phase. Then, the gastro-resistance of gellan microcapsules is verified through an in vitro test that mimics the gastric and intestinal phases of digestion. Confocal fluorescence microscopy is used to track microcapsules integrity and we show that microcapsules cargo is released in the intestine mostly due to its pH. Finally, we demonstrate that it is possible to produce magnetic microcapsules with well controlled magnetic response by adding different amounts of ferrofluid to their core or shell. The microcapsules produced have great potential for different applications in food, biomedical, pharmaceutical and oil and gas industries.

No description available.

No description available.

In many countries over the world (including Sweden), metal toxicity in freshwater resources causes a severe drinking water quality problem and poses a threat to the environment and human health. Among the different toxic metals in the water resources of Sweden, arsenic and uranium are the biggest threats to health. These elements, over long time consumption, may even lead to cancer and/or neurological disorder. Most of the wells are installed in crystalline and sedimentary bedrock and the received water comes from water bearing fractures in the bedrock. The handling of such water is an issue and there is a need to reduce the arsenic and uranium exposure by improving processes and technologies. It is a very serious problem demanding a safe, sustainable and eco-friendly arsenic and uranium removal technology prior to drinking water supply. Different treatment systems are available, but many of them are not suitable due to their high cost, operation complexity and waste management issues. Through this study, chitosan biopolymer the second largest abundant polysaccharide on earth after cellulose, was verified as a potential adsorbent for arsenic(V) and uranium(VI) removal from water solution. Adsorbent characterizations were also conducted by XRD, FTIR, SEM, UV-visible spectrum and TGA/DTA investigations. Bench-scale batch experiments were conducted using chitosan biopolymer (DDA-85%) as an adsorbent to determine the arsenic(V) and uranium(VI) removal efficiency, by allowing four important effective parameters e.g. chitosan dosages, pH, contact time and contaminant concentration. The adsorption data at optimum conditions were fitted with Langmuir, Freundlich and Dubinin-Radushkhevic (D-R) isotherm and Lagergren pseudo-first-order and pseudo-second-order kinetic model to investigate the adsorption process. The characterization of materials assured the presence of effective amino, hydroxyl, and carboxyl groups of chitosan. Another advanntage is that the materials are bio-degradable. The results show that the arsenic(V) and uranium(VI) removal efficiency was 100% and 97.45% after 300 minutes with optimum pH of 6.0 and 7.0 respectively. The optimum adsorbent dosages and initial concentration were 60 and 80g/L and 100 and 250 µg/L respectively. The adsorption process was suitably described by Freundlich isotherm (R2 = 0.9933) and Langmuir isotherm (R2 = 0.9858) correspondingly for arsenic(V) uranium(VI) compared to other isotherms. This is an important indicator of homogeneous monolayer adsorption of metals. For both of arsenic(V) and uranium(VI), pseudo-second-order explained the adsorption kinetics better than pseudo-first-order and the second-order kinetic regression coefficient (R2) were 0.9959 and 0.9672 correspondingly. Connecting to the above mentioned results, it can be summed up that the chitosan biopolymer (DDA 85%) can be used as an inexpensive, sustainable and environment-friendly treatment option for arsenic(V) and uranium(VI) contaminated drinking water. / I många länder världen runt (även i Sverige) orsakar metallers toxicitet besvärliga vattenkvalitetsproblem och utgör ett hot mot människors hälsa. Bland de toxiska metaller som finns i svenska vatten utgör arsenik och uran i dricksvatten allvarliga hälsorisker vid långvarig exposition då de kan orsaka cancer och neurologiska problem. Flertalet brunnar är installerade i kristallint berg och sedimentära bergarter och vattnet kommer vanligen från sprickor i berggrunden. Hanteringen av sådant vatten kan kräva reduktion av expositionen för arsenik- och uraninnehåll genom förbättrade processer och teknologier. Detta är ett angeläget problem som kräver en säker, pålitlig och ekovänlig teknologi att tillämpas innan vattnet distribueras. En rad olika behandlingssystem är tillgängliga men många av dem är inte lämpliga beroende på deras höga kostnad, den komplicerade tillämpningen och problem med hanteringen av restprodukter. I denna studie has biopolymeren chitosan, den näst vanligaste polymeren efter cellulosa, konstaterats vara en möjlig adsorbent för att avlägsna arsenik(V) och uran(VI) från vatten. Karakterisering av adsorbenten har också genomförts genom XRD, FTIR, SEM, UV och strålning i synligt ljus samt TGA/DTA undersökningar. Batch-tester i bänkskala har genomförts med användning av chitosan (DDA-85%) som adsorbent för att bestämma dess förmåga att avlägsna arsenik(V) och uran(VI)genom att variera fyra parametrar, nämligen kontakttid, pH, dos av chitosan och halt av föroreningen. Adsorptionsdata vid optimala förhållanden bestämdes genom tillämpning av Langmuir, Freundlich och Dubinin-Radushkhevic (D-R) isotermerna. Vidare tillämpades Lagergrens pseudo-first-order och pseudo-second-order kinetiska modell för att undersöka adsorptionsprocessen. Karakteriseringen av materialet visade förefintligheten av effektiva amino- (N-H), hydroxyl- (O-H) samt karboxylgrupper (C=O) i chitosan-polysackariden och att det är lätt nedbrytbart. Preliminära resultat visar att reduktionen av arsenik(V) och uran(VI) var 100 respektive 97,45 % efter 300 minuters kontakttid med optimalt pH på 6,0 respektive 7,0. De optimala doserna av adsorbent och den initiala koncentrationen var 60 och 80 g/L och 100 och 250 µg/L. Adsorptions process beskrevs bäst av Freundlich-isotermen för arsenik(V) (R2 = 0.9933) och med Langmuir-isotermen för uran(VI) (R2 = 0,9858) jämfört med andra isotermer vilket var en viktig indikation på en homogen monolager-adsorption. För både arsenik(V) och uran(VI) beskrev pseudo-second order adsorptionen bättre än pseudo-first-order. Second-order kinetiska regressionskoefficienten (R2) var 0.9959 och 0.9872 respektive. De ovanstående resultaten visar sammanfattningsvis att chitosan (DDA-85%) kan användas som en billig, pålitlig och miljövänlig behandlingsmetod av vatten för arsenik(V) och uran(VI). / <p>QC 20150526</p> / ChitoClean

This thesis examines the dynamic mechanical properties of natural silk fibres, mainly from silkworm species Bombyx mori (B. mori) and spider species Nephila edulis, using dynamic mechanical thermal analysis, DMTA. The aim is not only to provide novel data on mechanical properties of silk, but also to relate these properties to the structure and morphology of silk. A systematic approach is adopted to evaluate the effect of the three principal factors of stress, temperature and hydration on the properties and structure of silk. The methods developed in this work are then used to examine commercially important aspects of the ‘quality’ of silk. I show that the dynamic storage modulus of silks increases with loading stress in the deformation through yield to failure, whereas the conventional engineering tensile modulus decreases significantly post-yield. Analyses of the effects of temperature and thermal history show a number of important effects: (1) the loss peak at -60 °C is found to be associated the protein-water glass transition; (2) the increase in the dynamic storage modulus of native silks between temperature +25 and 100 °C is due simply to water loss; (3) a number of discrete loss peaks from +150 to +220°C are observed and attributed to the glass transition of different states of disordered structure with different intermolecular hydrogen bonding. Excess environmental humidity results in a lower effective glass transition temperature (Tg) for disordered silk fractions. Also, humidity-dynamic mechanical analysis on Nephila edulis spider dragline silks has shown that the glass transition induces a partial supercontraction, called Tg contraction. This new finding leads to the conclusion of two independent mechanisms for supercontraction in spider dragline silks. Study of three commercial B. mori cocoon silk grades and a variety of processed silks or artificial silks shows that lower grade and poorly processed silks display lower Tg values, and often have a greater loss tangent at Tg due to increased disorder. This suggests that processing contributes significantly to the differences in the structural order among natural or unnatural silks. More importantly, dynamic mechanical thermal analysis is proposed to be a potential tool for quality evaluation and control in silk production and processing. In summary, I demonstrate that DMTA is a valuable analytical tool for understanding the structure and properties of silk, and use a systematic approach to understand quantitatively the important mechanical properties of silk in terms of a generic structural framework in silk proteins.

Um problema importante na produção de filmes ativos utilizando agentes ativos lipofílicos é a dificuldade de dispersão desses agentes na solução formadora de filme (SFF). As nanoemulsões podem ser uma alternativa para dispersar esses compostos na matriz biopolimérica. Os objetivos gerais desta pesquisa foram: 1) Desenvolver nanoemulsões óleo-em-água (O/A), com três agentes ativos na fase óleo, sendo dois antimicrobianos - cinamaldeído e óleo essencial de alho - e um antioxidante - alfa-tocoferol, e caracterizar essas nanoemulsões, inclusive sua estabilidade; e 2) Desenvolver, caracterizar e aplicar filmes ativos à base de gelatina-quitosana (G-Q), ativados com nanoemulsões O/A preparadas nas condições ótimas de processo: N1: &alpha;-tocoferol/cinamaldeído; N2: &alpha;-tocoferol/óleo essencial de alho; N3: &alpha;-tocoferol/cinamaldeído e óleo essencial de alho; e N4: óleo de canola. As nanoemulsões O/A foram preparadas usando um microfluidizador e Tween 20 e Span 60 como emulsificantes, caracterizadas e incorporadas na SFF. Os filmes foram produzidos pela técnica de Casting incorporando 0 ou 5 g agente ativo nanoemulsificado/100 g biopolímero e usando glicerol como plastificante. Os filmes foram caracterizados em termos de propriedades físicas, mecânicas, de permeabilidade ao vapor de água e isotermas de sorção, ópticas, microestruturais, e atividades antimicrobiana e antioxidante. Além disso, um estudo de migração dos agentes ativos em simuladores de alimentos foi realizado. A mortadela fatiada foi embalada em bandejas de poliestireno usando filmes como separador de fatias. Posteriormente, foi avaliada a aceitação sensorial da mortadela e sua vida útil com base em análises físico-químicas e microbiológicas. Os resultados mostraram emulsões O/A com tamanho de gota nanométrico, distribuição monomodal, potencial &zeta; &gt;-30 mV, alta estabilidade física e eficiência de encapsulação e propriedades ativas. Por outro lado, os filmes ativos não apresentaram diferenças significativas (p&gt;0,05) quanto à espessura, umidade, permeabilidade ao vapor de água e propriedades térmicas. A solubilidade em água, ângulo de contato, transmissão de luz, rigidez e resistência à tração e o brilho dos filmes foram reduzidos (p&lt;0,05), enquanto a deformação na ruptura, opacidade, grau de inchamento, cor e rugosidade da superfície aumentaram consideravelmente (p&lt;0,05) em razão da incorporação das nanoemulsões. Os modelos matemáticos de BET, GAB, Peleg e Oswin descreveram o comportamento de absorção de vapor de água dos filmes. As análises de DSC, FTIR e de difração de raios-X sugeriram compatibilidade entre a gelatina e a quitosana. Uma boa distribuição das nanogotas de óleo que encapsulavam os agentes ativos na matriz biopolimérica foi confirmada pelas análises de MEV e MFA. As nanoemulsões e os filmes ativos foram efetivos contra a Pseudomonas aeruginosa e Listeria monocytogenes e apresentaram atividade antioxidante frente aos radicais DPPH&bull;, ABTS&bull;+ e o reagente FRAP. As cinéticas de migração dos agentes ativos apresentaram comportamento Fickiano, com valores de coeficientes de difusão efetiva (D) entre 10-14 e 10-15 m2/s. Por outro lado, as fatias de mortadela embaladas sem filme foram as mais aceitas sensorialmente. Porém, o filme ativo utilizado ofereceu a maior ação antimicrobiana contra a L. monocytogenes e P. aeruginosa, inicialmente inoculadas na mortadela, além do maior efeito protetor contra bactérias deteriorantes, assim como inibiu a oxidação lipídica por mais tempo (5 dias) durante o estudo de vida útil. Em geral, este estudo evidenciou que os filmes à base de G-Q carregados com agentes ativos nanoemulsificados pode ter potencial como material de embalagem para melhorar a vida útil de alimentos. / A major problem in the production of active films using lipophilic active agents is their poor dispersion in the film-forming solution (FFS). Nanoemulsions may be an alternative to disperse these compounds within the biopolymeric matrix. The main aims of this research were: 1) to develop oil-in-water (O/W) nanoemulsions incorporated with three active agents in the oil phase, two antimicrobials - cinnamaldehyde and garlic essential oil - and one antioxidant - &alpha;-tocopherol and characterize those nanoemulsions, even their stability, and 2) Develop, characterize and applicate gelatin-chitosan (G-Ch) based films activated with O/W nanoemulsions prepared under optimal conditions: N1: &alpha;-tocopherol/cinnamaldehyde; N2: &alpha;-tocopherol/garlic essential oil; N3: &alpha;-tocopherol/cinnamaldehyde and garlic essential oil; and N4: canola oil. The O/W nanoemulsions were prepared using a microfluidizer and Tween 20 and Span 60 as emulsifiers, characterized, and then loaded into the FFS. The films were produced by the casting method incorporating 0 or 5 g of nanoemulsified active agent/100 g biopolymer, using glycerol as a plasticizer, and subsequently characterized in terms of their physical, mechanical, water vapor permeability, water sorption, optical, microstructural, antimicrobial and antioxidant properties. In addition, a study of active agent migration into food simulants was performed. The sliced mortadella was packed in polystyrene trays using films as a slice separator. After, a sensorial acceptance evaluation and shelf life study, based on physicochemical and microbiological analyses, were performed for the mortadella sausage. The results showed O/A emulsions with nanometric droplet size, monomodal distribution, &zeta; potential greater than -30 mV, high physical stability, high encapsulation efficiency, and active properties. On the other hand, the active films presented no significant differences (p&gt;0.05) in terms of thickness, moisture content, water vapor permeability, and thermal properties. The solubility in water, contact angle, light transmission, tensile strength, and brightness of films were reduced (p&lt;0.05), whilst the deformation at break, opacity, degree of swelling, color, and surface roughness considerably increased (p&lt;0.05), due to the incorporation of nanoemulsions. The mathematical models of BET, GAB, Peleg and Oswin described the water vapor absorption behavior of the films. The DSC, FTIR, and x-ray analyses suggested compatibility between the gelatin and chitosan. A good distribution of the oil nanodroplets encapsulating the active agents within the matrix was confirmed by AFM and SEM analyses. The active nanoemulsions and films were effective against Pseudomonas aeruginosa and Listeria monocytogenes, and showed antioxidant activity against the DPPH&bull; and ABTS&bull;+ free radicals, as well as the FRAP reagent. The kinetic migration of the active agents presented a Fickian behavior with values of effective diffusion coefficients (D) between 10-14 and 10-15 m2/s. On the other hand, the mortadella slices packed without films were the most sensorially accepted. However, the active films used offered the greatest effectiveness against L. monocytogenes and P. aeruginosa initially inoculated in the mortadella sausage, and highest protective effect against spoilage bacteria, as well as inhibiting lipid oxidation for longer time (5 days) during the shelf life study. Overall, this study offered clear evidence that G-Ch based films, loaded with nanoemulsified active agents, can have potential as packaging material for enhancing the shelf life of food.

Ce travail de thèse porte sur la caractérisation d’un matériau composite polyacide lactique-bioverre pour application comme dispositif de réparation osseuse. Le bioverre étant trop fragile pour être utilisé seul comme dispositif de réparation osseuse, celui-ci est associé à une matrice polymère résorbable permettant d’apporter le caractère bioactif à des matériaux pouvant être mis en forme par des procédés de plasturgie. Le matériau composite polyacide lactique-bioverre est ainsi mis en forme par injection à partir de granules élaborés par voie solvant. La caractérisation des propriétés de ce matériau composite a révélé une augmentation du module élastique avec l’ajout de charges, mais une diminution des contraintes maximales admissibles et de la déformation à la rupture. Les modifications des propriétés mécaniques ont été associées à une modification des propriétés de la matrice et notamment de sa masse moléculaire. Un autre mode d’élaboration par pressage à chaud a permis de limiter la dégradation du polymère. Une meilleure maitrise de la masse moléculaire du composite serait ainsi un moyen de contrôler sa cinétique de dégradation in vivo et ainsi d’adapter ses propriétés en fonction du cahier des charges des applications visées. Dans une seconde partie, l’effet du taux de bioverre sur le caractère bioactif du composite a été évalué par immersion dans un fluide biologique de composites chargés à 20, 30 et 50% (en masse de bioverre). Un scénario de cristallisation à la surface des différents composites a ainsi été proposé. Tous les composites se sont révélés bioactifs et d’autant plus que le taux de bioverre est élevé. Le composite chargé à 50% apparait ainsi comme le matériau le plus bioactif, mais sa vitesse de dégradation est très rapide. Ce matériau étant destiné à être implanté, une étude de biocompatibilité in vitro a été menée par culture de cellules ostéoblastiques à la surface des matériaux. Enfin la biocompatibilité du composite in vivo, son caractère biorésorbable et ostéoconducteur ont été évalués par implantation du matériau composite dans les tissus musculaires et osseux de lapins. Le caractère biocompatible, bioactif et ostéoconducteur du composite chargé à 30% en masse de bioverre en fait un candidat de choix pour les applications proposées. / The aim of this work was to evaluate polylactic acid- Bioglass® composites for bone repair applications. Bioglass being too brittle to be used alone for load bearing applications, our strategy was to incorporate bioactive Bioglass® particles into a bioresorbable polymer matrix processed by conventional manufacturing techniques. The composite were processed by injection moulding from granules prepared by a solvent route. The composites exhibit higher Young modulus but lower strength and strain to failure than polymer alone. This is attributed to a decrease of molecular weight of the polymer matrix during the different steps of the process. Another processing method (hot pressing) was used to limit the drop in molecular weight of the polymer matrix: it leads to higher mechanical properties. Therefore, a careful control of the Polymer degradation may insure better mechanical properties and a better control of the degradation rate in vivo. The bioactivity of composites with 20, 30, 50 Wt. % of Bioglass® was a assessed by immersion in simulated body fluid. All the composites are bioactive, and all the more since the Bioglass® content is large. On the other side, the degradation of composites with a Bioglass® content of 50 wt. % is very rapid. Biological evaluation was conducted in vitro and in vivo. Osteoblast cell cultures and in vivo evaluation in rabbits demonstrate that polylactic acid - Bioglass® composites are biocompatible and osteoconductive. Such composites may therefore be a good option for bone repair applications in the future.

Les plastiques sont aujourd'hui des matériaux ubiquitaires utilisés dans tous les aspects de notre vie quotidienne, en particulier pour l'emballage alimentaire. Cependant, après usage, les plastiques sont une source de pollution de notre environnement naturel. Certains plastiques biodégradables et biosourcés sont déjà disponibles sur le marché, comme l’acide polylactique (PLA), mais ils présentent des performances inférieures. Ce travail de thèse vise à: 1) étudier la stabilité des films de PLA dans diverses conditions de température, d'humidité relative, de pH, d'exposition à des liquides ou à des vapeurs... 2) mieux comprendre l'impact de certains procédés industriels tels que les traitements corona ou pressage à chaud sur le PLA 3) combiner le PLA à des couches de gluten de blé afin de produire des complexes ayant des propriétés barrière plus élevées.Les films de PLA ont été produits par la société Taghleef Industries sur demande et avec des traitements de surface spécifiques, comme le traitement Corona. Des films et des enductions à basede gluten de blé ont été développés à l’échelle laboratoire ainsi que des complexes tricouches PLA- gluten-PLA. Les propriétés physiques et chimiques des films ont été étudiées par différentes techniques issues des sciences des matériaux et des aliments ont été utilisées, telles que l’analyse enthalpique différentielle (DSC), l'analyse thermogravimétrique (TGA), la chromatographie d'exclusion de taille (SEC), la microscopie de force atomique (AFM), la microscopie électronique (SEM), la spectroscopie infrarouge à transformée de Fourier (ATR-FTIR) et la spectroscopie de rayons X (XPS). Les propriétés fonctionnelles telles que la perméabilité à la vapeur d'eau, à l'oxygène (O2), au dioxyde de carbone (CO2) ou à l'hélium (He), la sorption de gaz et de vapeurs, les propriétés mécaniques et de surface ont également été étudiées.Exposés au CO2, les films de PLA présentent une isotherme de sorption linéaire avec l’augmentation de pression. Cependant les modifications physiques et chimiques induites à des pressions élevées n'affectent pas son utilisation dans le domaine d’application alimentaire. Au contraire, lorsque les films de PLA sont exposés à l'humidité à l'état liquide ou vapeur, leur dégradation survient après deux mois à 50 ° C (essai accéléré) suite à son hydrolyse. Cette détérioration chimique, mise en évidence par une diminution significative de la masse molaire, entraine une perte de transparence, mais également par une augmentation de la cristallinité. Par ailleurs, le pH n'affecte pas le taux d'hydrolyse, ce qui est d'un intérêt essentiel pour conditionner des aliments humides.Les films à base gluten de blé ont été choisis pour leurs propriétés de barrière élevées lorsque l’humidité relative reste faible. L'incorporation de lipides n'a pas apporté d'amélioration de leurs performances barrières. Cependant, l'utilisation d’un procédé d’homogénéisation à haute pression a permis une meilleure dispersion du gluten, ce qui a conduit à des films plus homogènes ayant ainsi de meilleures propriétés fonctionnelles. Ces conditions ont donc été retenues pour réaliser des complexes à 3 couches par assemblage d'une couche de gluten de blé entre deux couches de PLA en utilisant un pressage à chaud (10 MPa, 130 ° C, 10 min).La technologie de pressage à chaud montre une forte influence sur les films de PLA, de gluten et sur les tricouches. Elle induit une cristallisation accrue du PLA, ce qui augmente ses propriétés de barrière d'environ 40% et 60%, respectivement pour l'eau et l'oxygène. Cela masque par contre l’effet du traitement corona. D’autre part, le pressage à chaud induit une restructuration du réseau de gluten qui améliore les propriétés de barrière aux gaz des complexes, mais provoque aussi une évaporation de l'eau à l'interface gluten / PLA défavorable à l’adhésion des couches (...) / Poly(lactic acid) (PLA) is a biodegradable and renewable polyester, which is considered as the most promising eco-friendly substitute of conventional plastics. It is mainly used for food packaging applications, but some drawbacks still reduce its applications. On the one hand, its low barrier performance to gases (e.g. O2 and CO2) limits its use for applications requiring low gas transfer, such as modified atmosphere packaging (MAP) or for carbonate beverage packaging. On the other hand, its natural water sensitivity, which contributes to its biodegradation, limits its use for high moisture foods with long shelf life.Other biopolymers such as wheat gluten (WG) can be considered as interesting materials able to increase the PLA performances. WG is much more water sensitive, but it displays better gas barrier properties in dry surroundings. This complementarity in barrier performances drove us to study the development of multilayer complexes PLA-WG-PLA and to open unexplored application scenarios for these biopolymers.This project was thus intended to better understand how food components and use conditions could affect the performances of PLA films, and how these performances could be optimized by additional processing such as surface modifications (e.g. corona treatment and coatings).To that aim, three objectives were targeted:- To study the stability of industrially scale produced PLA films in contact with different molecules (CO2 and water) and in contact with vapour or liquid phases, with different pH, in order to mimic a wide range of food packaging applications.- To better understand the impact of some industrial processes such as corona or hot press treatments on PLA.- To combine PLA with WG layer to produce high barrier and biodegradable complexes.Different approaches coming from food engineering and material engineering were adopted. PLA films were produced at industrial scale by Taghleef Industries with specific surface treatments like corona. Wheat gluten films, coatings and layers were developed and optimized at lab scale as well as the 3-layers PLA-WG-PLA complexes. Different technologies able to mimic industrial processes were considered such as hot press, high pressure homogenization, ultrasounds, wet casting and spin coating. The physical and chemical properties of PLA films were then studied at the bulk and surface levels, from macroscopic to nanometer scale. The functional properties like permeability to gases (e.g. O2 and CO2) and water, gas and vapour sorption, mechanical and surface properties were also investigated.Exposed to CO2, PLA films exhibited a linear sorption behaviour with pressure, but the physical modifications induced by high pressure did not affect its use for food packaging. However, when exposed to moisture in both liquid and vapour state (i.e. environments from 50 to 100 % relative humidity (RH)), PLA was significantly degraded after two months at 50 °C (accelerated test) due to hydrolysis. This chemical deterioration was evidenced by a significant decrease of the molecular weight, which consequently induced a loss of transparency and an increase of the crystallinity. The hydrolysis was accelerated when the chemical potential of water was increased, and it was surprisingly higher for vapour compared to liquid state. In addition, pH did not affect the rate of hydrolysis.Knowing much better the limitation of PLA films, the challenge was to improve its functional properties by combining them with WG, as a high gas barrier bio-sourced and biodegradable polymer. The use of high pressure homogenization produced homogeneous WG coatings, with improved performances. This process was thus selected for making 3 layer complexes by assembly of a wheat gluten layer between two layers of PLA, together with corona treatment and hot press technologies.Corona treatment applied to PLA physically and chemically modified its surface at the nanometer scale (...) / I materiali plastici convenzionali trovano impiego in tutti campi della nostra vita, specialmente nel settore del packaging alimentare, ed in seguito all’utilizzo contaminano e danneggiano il nostro ecosistema. Materiali plastici derivanti da risorse naturali e biodegradabili, come acido polilattico (PLA), sono attualmente disponibili sul mercato anche se caratterizzati da performances inferiori.Questo progetto di dottorato è mirato 1) allo studio della stabilità di film di PLA a varie condizioni di stoccaggio come temperatura, umidità relativa, pH, o esposizione a vapori o gas; 2) a comprendere meglio le influenze di alcuni processi industriali come trattamento corona e hot press nelle proprietà dei film di PLA; 3) a sviluppare complessi multistrato tra film di PLA e di glutine che abbiano proprietà barriera più elevate rispetto ai singoli film.Gli imballaggi a base di PLA sono stati prodotti da Taghleef Industries, produttore leader nel settore e dotato di infrastrutture atte ai trattamenti di modificazione di superfice come il trattamento corona. I film a base di glutine e i coatings sono stati sviluppati e ottimizzati su scala di laboratorio, così come i complessi trilaminari PLA-glutine-PLA.Le proprietà fisiche e chimiche dei film di PLA sono state investigate a livello di superficie, così come a livello di bulk. Diverse tecniche analitiche, provenienti dal campo delle scienze dei materiali e delle scienze degli alimenti, sono state adottate in questo progetto di dottorato come calorimetria differenziale a scansione (DSC), termogravimetria (TGA), cromatografia di esclusione molecolare (SEC), microscopia a forza atomica (AFM), microscopia elettronica a scansione (SEM), spettrofotometria infrarossa a trasformata di Fourier in riflettanza totale attenuata (ATR-FTIR) e spettroscopia fotoelettronica a raggi X (XPS).Le proprietà funzionali come le permeabilità al vapore acqueo (H2O), all’ossigeno (O2), al diossido di carbonio (CO2) o all’elio (He) sono state investigate, cosi come l’assorbimento di gas e/o vapori, le proprietà meccaniche e le proprietà di superfice.Nonostante i film di PLA assorbano linearmente CO2 a pressioni crescenti, l’assorbimento di tale gas è ridotto a basse pressioni in modo da non modificare le sue proprietà fisiche – come contrariamente osservato quando il PLA è esposto a CO2 ad alte pressioni – e da non influenzare negativamente il suo utilizzo come imballaggio alimentare. Ad ogni modo, quando i film di PLA sono esposti ad ambienti umidi, o quando sono immersi in acqua liquida, sono significativamente degradati per idrolisi dopo due mesi di stoccaggio a 50 °C (test accelerato). Questo deterioramento chimico è stato evidenziato da una significativa riduzione del peso molecolare del PLA che, conseguentemente, induce una sua perdita di trasparenza e ne incrementa la sua cristallinità. Inoltre, è stato evidenziato che il pH non influenza la velocità di idrolisi. Quest’informazione ha importanza pratica per possibili utilizzi di PLA come imballaggio di alimenti ad alta umidità.Il glutine è stato scelto per le sue alte proprietà barriera, quando è protetto da ambienti ad alta umidità. Si è visto che l’incorporazione di lipidi non porta con sé grandi miglioramenti nelle performances dei film a base di glutine. Invece, l’utilizzo della tecnologia di omogeneizzazione ad alte pressioni permette una migliore dispersione del glutine, ottenendo film più omogenei e con migliori proprietà funzionali. Questa tecnologia è stata quindi scelta per produrre i complessi multistrato, intercalando i film di glutine tra due film di PLA, usando il trattamento hot press (10 MPa, 130 °C, 10 min). Si è osservato che il trattamento hot press modifica le proprietà dei film di PLA, di glutine e dei film multistrato Hot press induce cristallizzazione in PLA, e conseguentemente aumenta le sue proprietà barriera complessive, approssimativamente al 40 % all’acqua e al 60 % all’ossigeno (...) / Los materiales plásticos tradicionales son utilizados en todos los campos de nuestra vida y en particular modo como embajales de productos alimenticios; los cuales después de ser utilizados contaminan y dañan nuesto medio ambiente. Materiales plásticos derivados de recursos naturales y biodegradables, como el ácido poliláctico (PLA) se encuentran actualmente disponibles en el mercado a pesar de sus menores performances. Este proyecto de doctorado está orientado 1) al estudio de la estabilidad de películas de PLA bajo diferentes condiciones como temperatura, humedad relativa, pH o exposición a vapores o gases, 2) comprender los efectos en las propiedades de las películas de PLA de algunos procesos industriales como el tratamiento corona y hot press, 3) desarrollar complejos multicapas de PLA y gluten que tengan propiedades barrera mejores que las de las películas individuales.Los embalajes a base de PLA han sido producidos por Taghleef Industries, productor líder en el sector y dotado de las infraestructuras industriales adaptadas a los tratamientos superficiales como el tratamiento corona. Las películas de gluten y los coatings han sido desarrollados a escala de laboratorio, así como los complejos tricapa PLA-gluten-PLA.Las propiedades físicas y químicas de las películas de PLA han sido investigadas a nivel de superficie así como a nivel de bulk. Diferentes técnicas de análisis, frecuentemente utilizadas en los campos de las ciencias de los materiales y de las ciencias de los alimentos, han sido empleadas en este proyecto como calorimetría diferencial de barrido (DSC), análisis termogravimétrico (TGA), cromotagrafía de exclusión por tamaño (SEC), microscopía de fuerza atómica (AFM), microscopía electrónica de barrido (SEM), espectroscopía de infrarrojos por transformada de Fourier con reflectancia total atenuada (ATR-FTIR) y espectroscopía fotoelectrónica de rayos X (XPS).Las propiedades funcionales de los embalajes como las permeabilidades al vapor de agua, al oxígeno (O2), al dióxido de carbono (CO2) o al helio (He) han sido investigadas, asi como la absorción de gases/vapores, las propiedades mecánicas y las propiedades superficiales. A pesar de que las películas de PLA absorven linealmente CO2 a presiones mayores, la absorción del gas es reducida a bajas presiones y no modifica las propiedades físicas del PLA, como contrariamente sucede cuando el PLA es expuesto a altas presiones de CO2. Por lo tanto, su influencia en las propiedades funcionales del PLA es mínima en las normales aplicaciones alimentarias. De todos modos cuando los embalajes de PLA son expuestos a ambientes húmedos o cuando son sumergidos en agua, procesos de hidrólisis los degradan significativamente después de dos meses de conservación a 50 °C (test acelerado). Este deterioramiento químico ha sido evidenciado por una significativa reducción del peso molecular del PLA, que en consecuencia induce una pérdida de transparencia y un aumento de su cristalinidad. Además, se ha observado que el pH no influye en la velocidad de hidrólisis. Esta información tiene una importancia práctica para posibles usos del PLA como embalajes de alimentos a alta humedad. El gluten ha sido elegido por sus altas propiedades barrera cuando es protegido de ambientes a alta humedad. La incorporación de lípidos en las películas de gluten no han mejorado sus performances. Pero la tecnología de la homogenización a altas presiones ha permitido mejorar la dispersión del gluten, obteniendo películas más homogéneas y con mejores propiedades funcionales. Esta tecnología ha sido, por lo tanto, elegida para producir los complejos multicapa, intercalando las películas de gluten entre dos de PLA, utilizando el tratamiendo hot press (10 MPa, 130 °C, 10 min) (...)

Made available in DSpace on 2014-06-11T19:27:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-23Bitstream added on 2014-06-13T20:35:42Z : No. of bitstreams: 1 silva_lj_me_sjrp.pdf: 1135399 bytes, checksum: 5c78b7f4373a9244db399ef5e02efdad (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Os polímeros microbianos extracelulares (exo-biopolímeros) são moléculas que apresentam um grande potencial de aplicação nas indústrias de alimentos, farmacêuticas, petrolíferas, de cosméticos, têxteis, de papéis, tintas, produtos agrícolas entre outras. Como biorremediadores, podem ser utilizados na remoção de metais pesados em ambientes aquáticos poluídos, atuando como agentes de biossorção por meio da acumulação de nutrientes a partir do meio ambiente. O objetivo do trabalho foi a produção de exobiopolímeros a partir de três Ascomicetos endofíticos (Colletotrichum sp., Guignardia sp. e Phomopsis sp.). Foi selecionado o fungo que apresentou a maior produção desse material biológico. Tanto esse exo-biopolímero quanto a biomassa foram avaliados quanto aos seus potenciais de biossorção dos íons metálicos chumbo (Pb+2) e cádmio (Cd+2). Para a obtenção do meio de cultivo utilizado para a produção de exo-biopolímeros, foram testados o meio mínimo de sais de Vogel modificado com diferentes fontes de nitrogênio definidas e glicose como única fonte de carbono. Em seguida, foi realizado um planejamento fatorial 3(3-0) com 27 experimentos em duplicata, onde as variáveis independentes foram o tempo, temperatura de cultivo e a concentração inicial de glicose. O fungo Colletotrichum sp. apresentou a maior produção de exo-biopolímero (5,71 gL-1) utilizando a uréia como fonte de nitrogênio, em cultivo a 28 ºC, 150 rpm e glicose 6 % (p/v) em 192 horas de cultivo. A execução do planejamento fatorial demonstrou que a produção de biomassa seca foi favorecida por faixas de temperatura e concentração inicial de glicose entre 24 e 32 ºC e 35 e 75 gL-1, respectivamente. A produção de exo-biopolímero foi favorecida por faixas de temperatura e concentração... / The microbial extracellular polymer (exo-biopolymers) are molecules that have a great potential for application in the industries of food, pharmaceutical, oil, cosmetics, textiles, paper, paints, agricultural products and others. As bioremediation, can be used in the removal of heavy metals in polluted aquatic environments, acting as agents of bioremediation through the accumulation of nutrients from the environment. Objective of this study was to produce exo-biopolymer from three endophytic Ascomycota (Colletotrichum sp., Guignardia sp. and Phomopsis sp.). Then, was selected the fungus that showed the highest production of exobiopolymer. Both the exo-biopolymer and biomass were assessed for their potential of biosorption of metallic ions lead (Pb+2) and cadmium (Cd+2). To obtain the culture medium used for the production of exo-biopolymers, was tested a minimal medium salts of Vogel modified with different nitrogen sources and glucose defined as the only carbon source. Next, was performed a factorial design 3(3-0) with 27 experiments in duplicate, where the independent variables were the time and temperature of cultivation and the initial concentration of glucose. Colletotrichum sp. had the highest production of exo-biopolymer (5.71 gL-1) using urea as the nitrogen source in cultivation at 28 ºC, 150 rpm, and glucose 6% (w/v) in 192 hours of culture. The implementation of the factorial design showed that the dry biomass production was enhanced by a range of temperatures and initial concentration of glucose between 24 and 32 ºC and 35 and 75 gL-1, respectively. The production of exobiopolymer was favored by a range of temperatures and initial concentration of glucose between 24 and 36 ºC and 35 and 70 gL-1, respectively. In the experiment, the fungus Colletotrichum sp. produced 6.11 gL-1 of... (Complete abstract click electronic access below)