Made available in DSpace on 2017-07-21T20:42:34Z (GMT). No. of bitstreams: 1 EduardoNascimento.pdf: 8910148 bytes, checksum: f4ffc847b7369fe32fba17b11a5c5bdc (MD5) Previous issue date: 2011-02-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The degradation of polymer blends has been the subject of few scientific studies. Further studies are of great importance for understanding the degradation mechanisms in polymer blends. The degradation of the blend of HDPE / PS was studied as a function of their composition, processing temperature and number of processes. The material was extruded in a twin screw extruder co-rotacional interpenetrating at temperatures of 200, 240 and 280 ° C, reprocessed five times in the compositions of 25/75, 50/50 and 75/25 % (w.t) HDPE / PS, in addition to pure materials. An estimate of the distribution curve of molecular weight was made using data from parallel plate rheometry and degradation characteristics of the groups were analyzed by infrared spectroscopy with Fourier transformants. The results reveal two distinct regions of behavior in relation to the degradation of the blend. A domain with the mechanism of degradation of PS in which random chain scission occurs without the change in polydispersity, extending from pure PS to blend 50% HDPE / 50% PS. In this region the behavior is closer to the additivity of effects between the pure materials, tending to the field of mechanism of PS and greater balance between the mechanisms in that it increased the concentration of HDPE. It is inferred that this behavior go to about 40% of PS, where nearly co-continuity occurs between the phases. Another region is seen from the 75% HDPE blend. 25% PS to the pure HDPE, where the dominant mechanism is HDPE, with predominant chain branching and polydispersity increased at lower temperatures, in this case 200 ° C, and high rise of chain scission at higher temperatures, 280 ° C. In this region there is a synergistic effect towards the mechanism of HDPE, i.e. the addition of 25% of BP leads to a show very similar behavior to that of pure HDPE, distinguishing the effect of additivity. There is greater resistance to oxidation, synergistic effect, especially in the composition of 75% HDPE/PS 25% attributed to the dispersed morphology of the blends in this composition. / A degradação de blendas poliméricas tem sido alvo de poucos trabalhos científicos. Estudos mais aprofundados são de grande importância para o entendimento dos mecanismos de degradação em misturas de polímeros. A degradação da blenda PEAD/PS foi estudada em função da sua composição, temperatura de processamento e número de processamentos. O material foi extrudado numa extrusora dupla rosca corrotacional interpenetrantes nas temperaturas de 200, 240 e 280 °C, reprocessada cinco vezes nas composições de 25/75, 50/50 e 75/25 % (g/g) PEAD/PS, além dos materiais puros. Uma estimativa da curva de distribuição de massa molar foi feita através de dados de reometria de placas paralelas e os grupos característicos da degradação foram analisados por espectroscopia de infravermelho com transformada de Fourier. Os resultados revelam duas regiões de comportamentos distintos em relação à degradação da blenda. Uma com domínio do mecanismo de degradação do PS, no qual ocorre cisão aleatória das cadeias sem a variação da polidispersão, estendendo-se do PS puro até a blenda 50 % PEAD/ 50% PS. Nesta região o comportamento fica mais próximo à aditividade dos efeitos entre os materiais puros, tendendo para o domínio do mecanismo do PS e maior equilíbrio entre os mecanismos na medida em que é aumentada a concentração de PEAD. Infere-se que este comportamento siga até cerca de 40 % de PS, aproximadamente onde ocorre a cocontinuidade entre as fases. Outra região é vista a partir da blenda 75 % PEAD. 25 % PS até o PEAD puro, onde o mecanismo dominante é o do PEAD, apresentando preponderante ramificação de cadeia e aumento da polidispersão em menores temperaturas, neste caso 200 °C, e elevado aumento da cisão de cadeia em temperaturas maiores, 280 °C. Nesta região encontra-se um efeito sinérgico no sentido do mecanismo do PEAD, ou seja, a adição de 25 % de PS mostra conduz a um comportamento muito próximo ao de PEAD puro, distinguindo-se d efeito da aditividade. Há uma maior resistência à oxidação, efeito sinérgico, principalmente na composição 75 % PEAD. 25 % PS atribuído à morfologia dispersa da blenda nessa composição.

This research investigates formulation, compounding and thin-wall injection moulding of Polypropylene/clay nanocomposites (PPCNs) prepared using conventional melt-state processes. An independent study on single screw extrusion dynamics using Design of Experiments (DoE) was performed first. Then the optimum formulation of PPCNs and compounding conditions were determined using this strategy. The outcomes from the DoE study were then applied to produce PPCN compounds for the subsequent study of thin-wall injection moulding, for which a novel four-cavity injection moulding system was designed using CAD software and a new moulding tool was constructed based upon this design. Subsequently, the effects of moulding conditions, nanoclay concentration and wall thickness on the injection moulded PPCN parts were investigated. Moreover, simulation of the injection moulding process was carried out to compare the predicted performance with that obtained in practice by measurement of real-time data using an in-cavity pressure sensor. For the selected materials, the optimum formulation is 4 wt% organoclay (DK4), 4 wt% compatibiliser (Polybond 3200, PPgMA) and 1.5 wt% co-intercalant (erucamide), as the maximum interlayer spacing of clay can be achieved in the selected experimental range. Furthermore, DoE investigations determined that a screw speed of 159 rpm and a feed rate of 5.4 kg/h are the optimum compounding conditions for the twin screw extruder used to obtain the highest tensile modulus and yield strength from the PPCN compounds. The optimised formulation of PPCNs and compounding conditions were adopted to manufacture PPCN materials for the study of thin-wall injection moulding. In the selected processing window, tensile modulus and yield strength increase significantly with decreasing injection speed, due to shear-induced orientation effects, exemplified by a significantly increased frozen layer thickness observed by optical microscopy (OM) and Moldflow® simulation. Furthermore, the TEM images indicate a strong orientation of clay particles in the flow direction, so the PPCN test pieces cut parallel to the flow direction have 36.4% higher tensile modulus and 13.6 % higher yield strength than those cut perpendicular to the flow direction, demonstrating the effects of shear induced orientation on the tensile properties of thin-wall injection moulded PPCN parts. In comparison to injection speed, mould temperature has very limited effects in the selected range investigated (25-55 °C), in this study. The changes in moulding conditions show no distinctive effects on PP crystallinity and intercalation behaviour of clay. Impact toughness of thin wall injection moulded PPCN parts is not significantly affected by either the changes in moulding conditions or clay concentration (1-5 %). The SEM images show no clear difference between the fracture surfaces of PPCN samples with different clay concentrations. TEM and XRD results suggest that higher intercalation but lower exfoliation is achieved in PPCN parts with higher clay content. The composites in the thin sections (at the end of flow) have 34 % higher tensile modulus and 11 % higher yield strength than in the thicker sections, although the thin sections show reduced d001 values. This is attributed to the significantly enhanced shear-induced particle/molecular orientation and more highly oriented frozen layer, according to TEM, OM and process simulation results. In terms of the reduced d001 values in the thin sections, it is proposed that the extreme shear conditions in the thin sections stretch the PP chains in the clay galleries to a much higher level, compaction of clay stacks occurs as less interspacing is needed to accommodate the stretched chains, but rapid cooling allows no time for the chains to relax and expand the galleries back. Overall, data obtained from both actual moulding and simulation indicate that injection speed is of utmost importance to the thin-wall injection moulding process, development of microstructure, and thus the resulting properties of the moulded PPCN parts, in the selected experimental ranges of this research.

Des produits de consommation de première nécessité aux produits les plus fortuits, l'emballage, en particulier plastique, constitue aujourd'hui un élément indispensable de notre vie quotidienne. Son utilisation intensive dans le domaine agroalimentaire pour un usage unique à courte durée de vie incite aujourd'hui à s'orienter vers de nouveaux matériaux d'origine renouvelable et biodégradables, aux caractéristiques similaires que leurs homologues issus des ressources fossiles. Les mélanges à base de biopolymères et de biopolyesters peuvent être une bonne alternative. Dans ce présent travail de thèse, des mélanges de farine de blé, thermoplastifiée par du glycérol et de l'eau, et des polyesters biosourcés et biodégradables tels que le PLA et/ou le PHB ont été obtenus par extrusion bivis et moulés par injection thermoplastique. Les caractéristiques thermiques, thermomécaniques dynamiques, morphologiques, mécaniques et barrières de ces nouveaux matériaux ont été étudiés. De l'acide citrique a été utilisé comme agent de compatibilisant pour améliorer l'interface amidon/PLA. Les différentes investigations nous ont permis de mettre au point différents types de formulations aux caractéristiques mécaniques et barrières à la vapeur d'eau intéressantes pour la fabrication de corps de barquettes d'emballage alimentaire de denrées périssables comme la viande ou les fromages. L'aptitude au contact alimentaire des matériaux farine thermoplastifiée/polyester et l'impact de l'incorporation des polyesters sur la biodégradabilité de ces matériaux ont également été étudiés. / From basic and essential to unnecessary and optional consumer products, packaging, particularly plastic, is today an indispensable part of our daily life. Its extensive use in the food industry for a single use and for a short shelf-life encourages us today to move towards new renewable and biodegradable materials with similar characteristics than their counterparts from fossil resources. Biopolymers and biopolyesters blends can be a good alternative. Within the framework of this present work, wheat flour, thermoplasticised by glycerol and water, and biobased and biodegradable polyesters such as PLA and/or PHB, were blended using an industrial twin screw extruder and were injection-molded into thermoplastic materials. Thermal, dynamic thermomechanical, morphological, mechanical and barriers properties of these new materials were studied. Citric acid was used as a compatibilizer to improve the interface starch/PLA. The different investigations have allowed us to develop various types of formulations, with mechanical characteristics and barrier properties to water vapor, very attractive for manufacturing plastic food packaging which can be used for meats or cheeses. Food contact suitability and biodegradability of thermoplasticised wheat flour/polyester materials have also studied.

No description available.

The twin screw extrusion technique has been explored to produce lyotropic liquid crystal coated powder precursor by exploiting Pluronic F127 thermoreversible gelation property to get powder precursor without granular aggregates or with less compacted granular aggregates. The highly soluble chlorpheniramine maleate loaded in Pluronic F127 solution coated MCC particles prepared through twin screw extrusion was examined to produce the cubic phase (gel) for the development of controlled release formulation and for coating of very fine particles which cannot be achieved by traditional bead coaters. Controlled release formulations are beneficial in reducing the frequency of administration of highly soluble drugs having short half life and also to address the problem of polypharmacy in old age patients by reduction of dosage frequency. An unusual refrigerated temperature (5 C) profile for twin screw extrusion was selected based on the complex viscoelastic flow behaviour of Pluronic F127 solution which was found to be highly temperature sensitive. The Pluronic F127 solution was found to be Newtonian in flow and less viscoelastic at low temperature, such that low temperature (5 C) conditions were found to be suitable for mixing and coating the MCC particles to avoid compacted aggregates. At higher temperatures (35-40 C) Pluronic F127 solution exhibited shear thinning and prominent viscoelasticity, properties which were exploited to force CPM containing Pluronic F127 solution to stick over the MCC surface. This was achieved by elevating the temperature of the last zone of the extrusion barrel. It was found that to avoid compacted aggregates the MCC must be five times the weight of the Pluronic F127 solution and processed at a screw speed of 400 RPM or above at refrigerated temperature. Processing was not found to be smooth at ambient temperature with frictional heat and high torque generation due to significant compaction of coated particles which can be attributed to the elastic behaviour of Pluronic F127 solution at temperatures between ambient to typical body temperature. PLM images confirmed the cubic phase formation (gel) by Pluronic F127 coating which was found to be thick with maximum Pluronic F127 concentration (25%). SEM images showed smoothing of surface topography, and stretching and elongation of MCC fibres after extrusion which is indicative of coating through extrusion processing. Plastic deformation was observed for the lower Pluronic F127 concentration and higher MCC proportions. There was a significant decrease in work done for cohesion by the powder flow analyser observed in the batches with more aggregates compared with batches with least aggregates. A regression analysis study on factorial design batches was conducted to investigate the significant independent variables and their impact on dependent variables for example % torque, geometric mean diameter and work done for cohesion, and to quantitatively evaluate them. From the regression analysis data it was found that the coefficient of determination for all three dependent variables was in the range of 55-62%. The pharmaceutical performance of the prepared coated LLC precursor through twin screw extrusion in terms of controlled release was found to be very disappointing. Almost 100% chlorpheniramine maleate was released within 10-15mins, defined as providing burst release. The MDSC method was developed within this work to detect Pluronic F127 solution cubic phase formation. The MDSC method was developed to consider sample size, effect of heating and cooling, sample heat capacity, and the parameters for highest sensitivity which can be followed by sample accurately without the phase lag to produce accurate repeatable results.

Dans le contexte actuel, les communautés scientifiques et politiques sont centrées sur les différentes manières de mieux préserver et utiliser les ressources naturelles de notre planète. Dans le but de réduire la consommation des matières issues du pétrole, et de développer de nouveaux produits et procédés industriels plus propres, l’industrie des fragrances et des arômes cherche aujourd’hui à développer de nouveaux matériaux bio-sourcés pour protéger leurs molécules volatiles odorantes. Dans ce travail de thèse, les maltodextrines ont été choisies comme composé majoritaire, les protéines de pois et un amidon modifié ont été sélectionnés comme additifs compatibilisants pour la composition des matrices d’agromatériaux. L’incorporation des molécules volatiles odorantes, ainsi que l’élaboration des matrices encapsulantes ont été réalisées en une seule étape, grâce à la technologie d’extrusion bi-vis à basse température. Les caractéristiques physicochimiques, thermiques et morphologiques de ces nouvelles matrices enrobantes ont été analysées, de même que la détermination de leur efficacité d’encapsulation et du profil de libération du principe actif. Les différentes investigations menées ont permis de mieux comprendre l’impact des formulations et de l’incorporation des molécules volatiles odorantes sur les paramètres opératoires. Les interactions entre la matrice enrobante et le principe actif ont également été étudiées. Les conditions d’extrusion établies, ainsi que les caractéristiques de ces nouvelles matrices encapsulantes, s’avèrent être pertinentes pour le domaine de la parfumerie. / Nowadays, scientific and political communities are focused on ways to better preserve and manage the natural resources of our planet. In order to reduce consumption of fossil resources, and to develop more environmentally friendly industrial processes, the industry of flavors and fragrances became interested in developing new bio-based encapsulating materials. In the present work, maltodextrins have been chosen as main component of the matrix, and pea protein isolate and a modified starch were selected as compatibilizing additives. The incorporation of volatile odorant compounds and the elaboration of the new bio-based delivery systems were performed, all in one single step, by low temperature twin-screw extrusion. The physicochemical, thermal and morphological properties of these matrices were studied, as well as the encapsulation efficiency and the release profile of the active compounds. These investigations have led to a better understanding of the impact of the formulations and of the incorporation of the active compound on the process parameters. The interactions between the wall and the encapsulated materials were also analyzed. The characteristics of the new bio-based delivery systems and the established extrusion process conditions were found to be very promising to be employed in the field of perfumery.

Des procédés innovants basés sur l’extrusion à haute vitesse et l’irradiation sous rayonnement γ, ont été étudiés en vue d’améliorer la compatibilisation de deux polyoléfines non miscibles : le polypropylène PP et le polyéthylène PE. Dans un premier temps, l’étude de la distribution des temps de séjour de polypropylènes dans l’extrudeuse à haute vitesse a été réalisée. L’impact des conditions opératoires (débit et vitesse de rotation des vis) ainsi que l’impact du profil de vis et de la viscosité du polypropylène d’étude ont été mis en avant. Certains résultats expérimentaux sont souvent en accord avec ceux du logiciel de simulation d’extrusion bi-vis Ludovic, bien qu’il puisse y avoir des écarts pour les hautes vitesses de rotation des vis. Dans un deuxième temps, une fois l’écoulement caractérisé, nous avons réalisé des mélanges PP/PE, les paramètres qui ont varié sont la quantité d’énergie apportée durant le mélange (vitesse de rotation des vis) ainsi que la présence ou non de copolymère préformé et le type d’atmosphère utilisée durant l’extrusion. Faire varier le taux de cisaillement ne permet pas la modulation des propriétés finales du mélange surtout lorsque l’on extrude sous atmosphère inerte. L’utilisation de copolymère préformé, de type éthylène-octène, permet d’améliorer considérablement les propriétés de notre mélange en créant une interphase "cœur-couronne" entre la matrice PP, le compatibilisant et la phase dispersée PE. Pour terminer, une étape d’irradiation γ a été ajoutée au procédé de mise en œuvre classique de nos mélanges. En première partie de cette étude, la simulation de spectres RPE a permis d’identifier et quantifier les différentes espèces radicalaires créées. Dans la deuxième partie, l’influence de la place de la séquence d’irradiation a été étudiée : avant extrusion, entre extrusion et injection, après injection et avant recuit. Les meilleures améliorations ont été obtenues lorsque l’irradiation est suivie d’un traitement thermique. En conclusion, il est possible d’améliorer la compatibilité d’un mélange PP/PE en jouant essentiellement sur l’ordre des étapes de production sans avoir à modifier la formulation de ce dernier. / Innovative processes, based on high shear twin screw extrusion and γ-irradiation, have been used to increase the compatibility of two immiscible polyolefins: polypropylene PP and polyethylene PE. In a first part, the residence time distribution of polypropylenes in the twin screw extruder (TSE) has been investigated. The impact of the processing conditions (throughput and screw rotation speed), the screw profile and the polypropylene viscosity were underlined. Some of the experimental results are often in good agreement with those predicted by simulation software of twin screw extrusion (Ludovic), except for some experiments at high screw rotation rates. In a second part, once polymer flow was characterised in the TSE, we realized PP/PE blends. The impact of the mechanical energy (screw rotation speed), the presence or absence of copolymers and the nature of the extrusion atmosphere were analysed. Using high shear rate does not allow modulating the final properties of the blends particularly once inert atmosphere is used. The use of ethylene-octene copolymers increases significantly the final properties of the PP/PE blends by creating a “core-shell” morphology between the PP matrix, the copolymer and the PE dispersed phase. To finish, a γ-irradiation process step has been added to the classical processing of PP/PE blends. In a first part of this study, the simulations of ESR spectra have permitted to identify and quantify the different radicals created. In a second part, the sequence order of the γ-irradiation has been investigated: before extrusion, between extrusion and injection, and after injection followed by a thermal treatment. The best results were obtained once γ-irradiation is followed by a heat treatment. As a conclusion, the compatibility of immiscible polyolefins can be improved only by changing the order of the different processing steps without changing the formulation.

Le travail présenté porte sur la rhéologie, la mise en forme et la caractérisation de matériaux biocomposites de nouvelles générations pour des applications orthopédiques. Dans le cadre de cette étude, des biocomposites poly (D,L-lactide) (PDLLA)/bioverres ont été élaborés par extrusion bivis sous atmosphère inerte. Les bioverres différent par la nature de leur traitement thermique et leur morphologie. La première partie a été consacrée à l’étude de l’état de la dispersion des bioverres dans la matrice polymère. Nous avons montré que l’homogénéité de cette dispersion dépend, d’une part de la structure, de la morphologie, du taux volumique des charges et d’autre part des paramètres du procédé (cisaillement, température,…). Le comportement rhéologique des suspensions a été étudié à l’état fondu ainsi qu’à l’état solide. Un accent particulier a été porté sur l’étude de l’influence du taux des bioverres, de leur taille moyenne et plus particulièrement de leur traitement thermique. Les masses molaires de PDLLA extrait des composites élaborés ont été évaluées par chromatographie d’exclusion stérique (CES). Enfin, la qualité de la dispersion des charges, en termes de distance inter-particulaire et taille moyenne, a été étudiée par microscopie électronique à balayage (MEB) et analyses d’image. Il a été montré que l’utilisation de bioverres non traités thermiquement lors de la mise en forme de composites à haute température provoque la dégradation de la matrice. Aussi, on assiste à une réduction des masses molaires. Les propriétés viscoélastiques et les propriétés mécaniques sont altérées à leur tour. Cette dégradation a été étudiée par spectroscopie infrarouge (IRTF) et par analyse thermogravimétrique (ATG). Les origines et mécanismes sous-jacents de cette dégradation ont été proposés. Il est démontré pour la première fois que la présente dégradation du PDLLA peut être atténuée par l’emploi de différentes charges céramiques à propriétés spécifiques. En outre, l’utilisation de ces bioverres a permis l’obtention d’une dispersion homogène au sein de la matrice. L’analyse des propriétés rhéologiques de tels matériaux et leur modélisation a permis de mettre en évidence les interactions matrice-charges. La deuxième partie de l’étude a porté sur l’élaboration des biocomposites multicouches à gradient de propriétés par coextrusion. Ces multicouches présentent, d’une part, des propriétés variables selon le type de traitement et de composition du bioverre actif. D’autre part, le gradient de propriété a été également réalisé en faisant varier les paramètres expérimentaux relatifs au procédé de coextrusion. Les matériaux finaux, ainsi obtenus, présentent de très bonnes propriétés cohésives avec une bioactivité maîtrisée et contrôlée. / Bioactive and biodegradable composites have gained increasing importance in the orthopedic field as bone replacement materials and as scaffolds for tissue engineering. In this study, biocomposites based on poly(D,L-lactide) (PDLLA) and bioactive glass fillers were prepared by a twin screw extrusion under Argon inert gas with various filler contents, thermal treatments and particle sizes. The processing conditions were monitored to produce composites with well controlled physico-chemical, mechanical and dispersive properties. The aim of the present work is to gain a fundamental understanding of the relationships between structure, processing conditions and final properties of these biocomposites. The dispersion state of fillers was characterized by SEM. It was highlighted that the inclusion of non treated bioglass in PDLLA under elevated temperatures resulted in a decrease of molar mass. This degradation of the matrix leads to a reduction of the viscoelastic and mechanical properties of the composites. The origin and mechanisms of this degradation were probed using a Fourier Transform Infrared (FTIR) spectroscopy. The optimization of their processing allows a better control of this drastic loss of properties. Furthermore, the demonstration had been done that the present degradation of PDLLA matrix can be attenuated using a different glass ceramics with a special size and thermally treated. The rheological behaviour in linear and non linear viscoelasticity of the controlled PDLLA/BG suspensions has been assessed in both solid and molten state. Hence, their experimental rheological behaviour was compared to the theoretical suspension models. Finally, the effects of volume fraction, particle size and thermal treatment on the mechanical properties have been also investigated and discussed. The obtained results corroborate the rheological and physic-chemical ones. Finally, the multilayer structures with various amounts and treatments of BG fillers were obtained by a designed scale lab coextrusion machines. The gradient of properties has been obtained and improved cohesion properties between the neighboring were highlighted. Their bioactivity was finally demonstrated. At last, no residual stress inside the multilayers can be observed. This observation explains the conservation of the initial shape of those implants, without nor deformation neither relaxation, during the simulation of the chirurgical implantation in SBF.