The relationship between polymer chain architecture, crystallization behavior, and morphology formation was investigated. The structures formed are highly dependent on chain configuration and crystallization kinetics. Poly(lactic acid) (PLA) and Poly(ethylene-co-vinyl acetate) (EVA) random copolymers were studied. Sample characterization was performed using a variety of techniques, including spectroscopy, scattering, and calorimetry. In PLA, structural differences between α’ and α crystalline phases were analyzed using cryogenic infrared and Raman spectroscopy. Compared to the  crystal, the ’ crystal has slightly looser packing and weaker intermolecular interactions involving carbonyl and methyl functional groups. Simulations in conjunction with Raman scattering analyzed the conformational distortion of the α’ phase. The conformation of an α’ chain was determined to have tg’t-103 conformation with tg’t-31 units randomly distributed along the chain. Departure of the O-C α dihedral angle was also confirmed. The structural disorder leads to different thermal properties for α’ and α crystalline forms, which was quantified by measuring the enthalpic change at melting for both crystals ( = 57 ± 3 J/g and =9 6 ± 3 J/g). The transformation from α’ to α and the mechanism of order formation in PLA were also elucidated. The relationship between chain configuration of EVA random copolymers and crystallization behavior was established. For three different EVA samples, the distribution of methylene sequences was calculated and compared to a distribution of crystallite sizes formed. This comparison revealed that only a small fraction of the total methylene segments present actually crystallized. Cocrystallization with highly mobile oligomers was explored to enhance the crystallization of EVA copolymers. When blended, EVA28 (28 weight percentage) cocrystallizes with C36H74 n-alkane resulting in faster crystallization kinetics and a higher degree of crystallinity. The observed increase in degree of crystallinity was directly related to the chain configuration. Compositional mapping using Raman spectroscopy provided evidence for oligomer nucleation. The cocrystallization kinetics and morphology of EVA and n-alkane blends was found to depend on the chain length of oligomer. In both systems studied, crystallization kinetics determines the morphologies formed, which are undoubtedly related to the details of molecular architecture.

Yes / The shape memory effect of highly oriented long‐chain‐branched poly(lactic acid) (LCB‐PLA) prepared through solid‐phase die drawing technology was studied by comparison with PLA. When the recovery temperature increased from 60°C to 120°C, for PLA, only one‐step recovery at about 80°C can be observed and the recovery ratio was below 21.5%, while, for LCB‐PLA, multiple recovery behavior with high recovery ratio of 78.8% can be achieved. For oriented PLA, the recovery curve of the final sample showed the same trend with that of sample suffering just free drawing; while for oriented LCB‐PLA, the recovery curve of the final sample showed the same trend with that of sample suffering just die drawing. After shape recovery, the mechanical properties of LCB‐PLA showed a linear downward trend with the recovery temperature. Together with amorphous phase, the oriented mesomorphic phase, which formed during solid die drawing, can act as switching domains. And thus, upon heating, the chain segment of amorphous phase relaxed at first and triggered the first macroscopical shape recovery, leading to the decrease of long period (Lac) and the thickness of the amorphous layer (La). Then, with further increasing temperature, the oriented mesomorphic phase gradually relaxed resulting subsequently multi‐shape recovery, and the Lac and the La further decreased. Therefore, by regulating the recovery temperature of oriented LCB‐PLA, the shape recovery ratio and mechanical strength can be controlled effectively, and thus the self‐reinforced and self‐fastening effect can be achieved simultaneously for PLA as bone fixation material.

<p>Poli(mlečna kiselina) (PLA) predstavlja jedan od najpopularnijih komercijalnih biorazgradivih polimera. Iako može da zameni neke od najče&scaron;će kori&scaron;ćenih sintetskih polimera, neka njegova svojstva (lo&scaron;a barijerna, termička i mehanička) jo&scaron; uvek predstavljaju prepreku u &scaron;iroj primeni, posebno za pakovanje hrane. Jedan od najsavremenijih načina prevazilaženja nedostataka u svojstvima biopolimera predstavljaju nanotehnologije.<br />U ovom radu ispitan je uticaj dodatka različitih koncentracija hidrofobnih nanočestica silicijum (IV) oksida (od 0.2 mas.% do 5 mas.%) pripremom uzoraka u rastvoru, i rastopu na toplotna, mehanička, i barijerna svojstva PLA. Morfolo&scaron;ke karakteristike uzoraka nanokompozita snimljene su pomoću skenirajuće elektronske mikroskopije (SEM). Ostvarena je izuzetno dobra disperzija i distribucija hidrofobnih čestica silicijum (IV) oksida koje su u malim udelima dodavane u poli(mlečnu kiselinu). Dobra disperzija i distribucija hidrofobnih čestica silicijum (IV) oksida ostvarena je kako pripremom nanokompozita metodom u rastvoru, tako i metodom u rastopu.<br />Toplotna svojstva PLA i pripremljenih nanokompozita proučavana su primenom diferencijalnog skenirajućeg kalorimetra (DSC), dok je stepen kristalnosti određen rasipanjem X zraka pod &scaron;irokim uglom(WAXD). Mehanička svojstva su ispitivana da bi se odredio uticaj dodatka nanočestica SiO2 na prekidnu čvrstoću i izduženje čistog PLA. Iako su prilikom pripreme materijala metodom u rastvoru, pobolj&scaron;anja mehaničkih i barijernih svojstava postignuta pri udelima silicijum (IV) oksida u rasponu od 0,2 do 5 mas.%, najznačajnija pobolj&scaron;anja postignuta su za najmanje udele nanočestica (0,2 mas.% i 0,5 mas.%). Pobolj&scaron;anja mehaničkih i barijernih svojstava nanokompozita, primenjenih metodom u rastopu, su registrovana i za udele silicijum (IV) oksida od 0,2 do 3 mas.%.<br />Takođe je ispitana mogućnost primene pripremljenog nanokompozita na osnovu poli(mlečne kiseline) i silicijum (IV) oksida za pakovanje prehrambenih proizvoda na primeru pakovanja svežeg svinjskog mesa (M. longissimus thoracis et lumborum). Ispitivanjem uticaja materijala za pakovanje svežeg mesa u vakuumu, na parametre tehnolo&scaron;kog (pH, boja), senzorskog, i mikrobiolo&scaron;kog kvaliteta mesa, utvrđeno je da su PLA kao i nanokompoziti na osnovu PLA sa različitim udelima silicijum (IV) oksida, pogodni za vakuum pakovanje i skladi&scaron;tenje svežeg svinjskog mesa.</p> / <p>Poly(lactic acid) presents one of the most popular bio-polymers for diverse applications. However, the use of PLA as food packaging material is limited due to poor barrier and mechanical properties. These properties could be improved by incorporation of nanoparticles into polymer matrix.<br />In this work neat PLA films and PLA films with different percentage of hydrophobic fumed silica nanoparticles (0,2 wt.% to 5 wt.%) were prepared by solution casting and melt blending methods. Several procedures were used to characterize the influence of different silica content on dispersion (SEM), crystalline behavior (WAXD), thermal stability (DSC, TGA), mechanical and barrier properties. It is shown that the applied techniques and selection of specific hydrophobic spherical nanofiller provide a good dispersion and distribution of silica nanoparticles in poly(lactic acid) for both film preparation methods.<br />Characteristics of films prepared by solution casting method showed improvements in mechanical and barrier properties for all loadings of nanofiller but the most significant improvements were achieved for lowest silica content (0,2 wt.% and 0,5 wt.%) The improvements in material characteristics (mechanical and barrier) for melt blending method were also achieved (for concentrations from 0,2 wt.% to 3 wt.%).<br />After film preparation, selected cuts of M. longissimus thoracis et lumborum were packed in prepred films of polymer nanocomposites, and the shelf-life characterisation was conducted on technological, sensory and microbiological paramethers of quality. After shelf-life characterisation it can be concluded that polymer nanocomposites based on PLA and silica nanoparticles could be used for packaging od fresh pork meat in vacuum.</p>

Les balles de céréales, à savoir l'enveloppe autour du grain, ont récemment retenu l'attention des scientifiques afin d'entrer dans la formulation de biocomposites. En effet, ces sous-produits de l'agriculture ont un coût négligeable, sont perpétuellement renouvelables et disponibles en volume important dans le Monde et leur fin de vie est assurée par leur biodégradabilité. Leurs compositions chimiques et leurs propriétés thermiques et mécaniques sont similaires à celles des fibres naturelles.Dans cette thèse, deux types de balles de riz et deux types de balles de Petit Epeautre ont été étudiées à travers leur microstructure, leur composition chimique, leurs propriétés mécaniques et thermiques. Les balles ont été incorporées dans une matrice bio-sourcée et biodégradable, à savoir le poly(acide lactique) (PLA) pour donner des biocomposites dont les propriétés d'usage ont été étudiées. Il apparaît que les balles céréalières peuvent devenir un candidat potentiel intéressant pour le renforcement du PLA moyennant une amélioration de l'adhésion à l'interface entre les balles et le PLA.Afin d'améliorer cette interface, les balles ont été traitées par une solution alcaline (NaOH) et par des agents de couplage de type organosilane (3-aminopropyltriéthoxysilane et 3- glycidoxypropyltrimethoxysilane). Le traitement alcalin a permis de retirer une grande partie des hémicelluloses, de la lignine, de la cire et de la silice présentes dans les balles. La dissolution de ces constituants a provoqué une plus forte hygroscopicité des balles et se traduit par de plus faibles propriétés mécaniques des biocomposites. Le couplage traitement alcalin/traitement silane semble apporter une amélioration des performances plus importantes que le traitement silane seul. Ce traitement de surface a davantage d'impact sur la balle de Petit Epeautre que sur la balle de riz.L'évolution des propriétés d'usage des biocomposites à base de balles de riz au cours de différents vieillissements (thermique, hydro-thermique, cyclages hygro-thermiques, UV) a été étudiée. Les résultats montrent que l'évolution microstructurale induite par les vieillissements influence significativement les propriétés des biocomposites. La dégradation des biocomposites se traduit par une diminution de la masse moléculaire moyenne du PLA. La réorganisation de ces macromolécules augmente sensiblement le taux de cristallinité du matériau. Ceci induit un changement de la couleur, de la stabilité dimensionnelle des pièces et des propriétés mécaniques du PLA et des biocomposites qui dépend essentiellement de la température de vieillissement par rapport à la température de transition vitreuse du PLA. Il apparaît que l'ajout de balles accélère la dégradation du PLA. Dans le cas d'un vieillissement hydro-thermique au-dessus de la température de transition vitreuse du PLA, une réduction de cette dégradation a été mise en évidence par l'utilisation de certains traitements de surface des balles. / The cereal husks, namely the envelope around the grain, have recently attracted the attention of scientists for biocomposites development, because they are low-cost, renewable, biodegradable, and available in abundant volume throughout the world. Their chemical composition and their thermal and mechanical properties are similar to the natural fibers.In this work, two types of rice husk and two types of Einkorn wheat husk were studied through their microstructure, chemical composition, mechanical and thermal properties. The husks have been incorporated into a bio-sourced and biodegradable matrix, namely poly (lactic acid) (PLA) to produce biocomposite which functional properties were studied. It appears that the husks can be good candidates for strengthening the PLA through improved adhesion at the interface between the husks and the PLA.To improve the husks/PLA interface, the husks were treated with an alkaline solution (NaOH) and organosilane coupling agents, such as 3-aminopropyltriethoxysilane and 3 - glycidoxypropyltrimethoxysilane. The alkaline treatment has removed much of hemicelluloses, lignin, wax and silica present in the husks. The dissolution of these components resulted in a higher hygroscopicity of husks and lower mechanical properties of biocomposites. The coupling between an alkaline treatment and a silane treatment seems to provide better properties than the silane treatment alone. This surface treatment has a greater impact on the Einkorn wheat husks than on rice husksThe variations of the functional properties of rice husks based biocomposites during different ageings (thermal ageing, hydro-thermal ageing, hygro-thermal cycled ageing, UV ageing) was studied. The results show that the microstructural changes induced by ageing significantly influence the properties of biocomposites. Biocomposites degradation results in a decrease of the average molecular weight of PLA. The reorganization of these macromolecules significantly increases the degree of crystallinity of the material. This causes a change in color, dimensional stability of devices and mechanical properties of PLA and biocomposites which essentially depends on the ageing temperature regards to the glass transition temperature of PLA. It appears that the addition of husks accelerates the degradation of PLA. In the case of a hydro-thermal ageing performed above the glass transition temperature of the PLA, a reduction of this degradation was demonstrated by the use of specific surface treatments of husks.

Ces travaux de recherche ont porté sur l'élaboration et la compatibilisation de mélanges de matériaux biosourcés à base d'amidon plastifié et de poly (acide lactique). La transformation de l'amidon natif en amidon plastifié est réalisable par extrusion en utilisant des plastifiants. Dans notre étude, les propriétés finales de l'amidon plastifié ont été contrôlées en faisant varier les conditions du procédé (température, temps de séjour, vitesse de rotation des vis) et du matériau (nature et teneur en plastifiant). La plastification de l'amidon par l'eau, le glycérol, le sorbitol et l'acide citrique a ainsi été étudiée. Les mélanges d'amidon plastifié et le poly (acide lactique)(PLA) ont été préparés et caractérisés dans la deuxième partie du travail. Afin d'améliorer la compatibilité de ces polymères, une voie consiste à incorporer un copolymère dans le mélange.Dans ce travail, le copolymère utilisé est un copolymère (Amylose-g-PLA) constitué d'une dorsale amylose et de greffons poly (acide lactique). Une polymérisation en trois étapes a été utilisée pour la synthèse du copolymère dans le but de contrôler la taille et le nombre de greffons de PLA. Deux types de copolymère ont été préparés : le type 1 contenant un nombre élevé de greffons de faible masse molaire et le type 2 contenant un nombre limité de greffons de haute masse molaire. L'efficacité de l'addition de ces copolymères Amylose-g-PLA dans les mélanges (PLA et amidon plastifié) est étudiée dans la dernière partie de ce travail. Une comparaison entre la morphologie et les propriétés mécaniques des mélanges préparées avec ces différents copolymères révèle l'efficacité plus élevée du copolymère de type 1 / This study dealt with the development and the compatibilization of the blends of plasticized starch and polylactic acid. The transformation of native to plasticized starch is possible by extrusion in the presence of plasticizers. In this work, the final properties of plasticized starch are controlled by changing process parameters (temperature, extrusion time, screw's rotation speed) and nature and quantity of plasticizers. Plasticization of starch by water, glycerol, sorbitol and citric acid is studied. The blends of plasticized starch and poly (lactic acid) (PLA) are prepared and characterized in the second part of this work. To improve the compatibility of the blend, one way is the addition of a copolymer to the mixture to stabilize the dispersed phase in the matrix. The copolymer used in this work (Amylose-g-PLA) is constituted of amylose backbone and poly (lactic acid) (PLA) grafts. The number and the size of the grafted chains of PLA have been controlled by a three step process polymerization. Two copolymer structures have been prepared: type1, containing high numbers of low molar weight PLA grafts and type 2, lower numbers of high molar weight PLA grafts. In the final part, efficiency of these copolymers (Amylose-g-PLA) in these blends is studied. The comparison between morphology and mechanical properties of blends prepared with these copolymers, demonstrate the higher efficiency of type1 copolymer

Dans ce travail de thèse, nous nous sommes intéressés au mélange de la farine de blé et du poly(acide lactique). La farine de blé, qui est composée principalement d'amidon, a été thermoplastifiée en extrudeur bivis par l'effet conjugué de la chaleur et du cisaillement en présence de plastifiants. Le poly(acide lactique) est, quant à lui, le polyester biodégradable le plus répandu à l'heure actuelle. Le mélange de ces deux phases est thermodynamiquement immiscible et peu compatible, différents leviers sont testés afin d'améliorer la qualité du mélange. Une première partie de ce travail repose sur la recherche de conditions optimales pour la transformation et le mélange des matières premières. L'extrusion bivis est utilisée à la fois pour plastifier l'amidon et pour assurer un bon mélange entre les phases. Le profil de vis et les différents équipements sont donc choisis en conséquence. Différents paramètres classiques de l'extrusion bivis sont étudiés : le profil de vis, le profil de température, le taux de remplissage… L'étude de la formulation, notamment des plastifiants utilisés pour la plastification de l'amidon mais également l'utilisation de compatibilisants pour améliorer l'interface amidon/PLA est traitée en deuxième partie. L'acide citrique est testé à la fois comme plastifiant et comme compatibilisant. Ces investigations nous ont permis de mettre au point différents grades intéressants répondant à des applications industrielles distinctes : injectabilité, souplesse, rigidité… / In this work, we have been interested in blending wheat flour and poly(lactic acid). Wheat flour, which is mainly constituted of starch, has been transformed with plasticizers in a twin-screw extruder with the effect of heat and shear. Poly(lactic acid) is the main biodegradable polyester in the world nowadays. These two phases are thermodynamically immiscible and not very compatible, different ways are tried to improve the blend quality. A first part of this work lies on the search of optimal conditions to transform and blend the raw materials. Twin-screw extrusion is used to pasticize starch and to ensure a good blending between the two phases. Screw design and different equipments have been chosen for this purpose. Classical twin-screw parameters have been studied: screw design, temperature profile, filling ratio… The study of the formulation, more particularly of plasticizers for starch plasticization but also of compatibilizers to improve starch/PLA interphase is tackled in a second part. Citric acid is tested as a plasticizer but also as a compatibilizer. These researches have allowed to develop interesting formulations for industrial applications: possibility of processing by injection-molding, flexibility, rigidity…

O poli(ácido láctico) (PLA) é um polímero biodegradável, biocompatível e bioabsorvível proveniente de fontes renováveis. Constitui uma excelente alternativa sustentável para substituição dos polímeros provenientes de petróleo, atualmente dominantes no mercado industrial. Apesar das vantagens, o PLA tem baixa tenacidade e reduzida elongação na ruptura a temperatura ambiente, o que torna a sua utilização limitada em usos que necessitem de alta deformação plástica em níveis de exigência mecânicos elevados. Misturas mecânicas de PLA com polímeros altamente flexíveis, como é o caso da poli(&#949;-caprolactona) (PCL), podem resultar em novos materiais com propriedades mecânicas adequadas para diferentes aplicações. Blendas PLA/PCL são completamente imiscíveis, sendo seu comportamento mecânico altamente dependente da interação interfacial entre os componentes da blenda. Portanto, o objetivo desse trabalho é avaliar o efeito compatibilizante de um copolímero em bloco de baixa massa molar (2000 g mol-1) derivado de &#949;-caprolactona e policarbonato (C2) e, disponível comercialmente em blendas imiscíveis PLA/PCL. Blendas binárias e ternárias foram preparadas por mistura mecânica no estado fundido via processo de extrusão em rosca simples. O teor de PLA nas blendas foi de 75, 50 e 25% (em massa) e a concentração do copolímero de 0, 1, 3, 5 e 7% (em massa). O comportamento térmico, morfológico e mecânico das blendas compatibilizadas e não compatibilizadas foi avaliado por Calorimetria Exploratória Diferencial (DSC), Análise Termodinâmico-Mecânica (DMTA), Microscopia Eletrônica de Varredura (MEV) e ensaios de tração, flexão e impacto Izod. Os resultados de DSC e DMTA indicaram que o copolímero provocou pequena redução na temperatura de transição vítrea (Tg) do PLA, sugerindo que o C2 é solúvel no PLA. Entretanto, nas micrografias das superfícies de fraturas do PLA foi nítida a presença de pequenas micelas formadas pelo copolímero em bloco, indicando que há um limite de solubilidade do compatibilizante na fase de PLA. Os resultados obtidos em tração mostraram que com o aumento do teor de compatibilizante, a tensão no escoamento, a tensão na ruptura e o módulo elástico das blendas sofrem alterações. A propriedade de tenacidade, avaliada no ensaio de impacto Izod, mostrou que as blendas tiveram um ganho na resistência quando comparadas com o PLA puro. Os resultados mostraram que o copolímero em bloco derivado de &#949;-caprolactona e policarbonato alifático pode atuar como compatibilizante para blendas PLA/PCL / Poly(lactic acid) (PLA) is a biodegradable, biocompatible and bioabsorbable polymer from renewable sources. It is an excellent sustainable alternative for replacing petroleum polymers, currently dominant in the industrial market. Despite the advantages, PLA has low toughness and reduced elongation at room temperature, which makes its use limited in uses that require high plastic deformation under high mechanical stress levels. Mechanical mixtures of PLA with highly flexible polymers, such as poly(&#949;-caprolactone) (PCL), may result in new materials with mechanical properties suitable for different applications. PLA/PCL blends are completely immiscible, and their mechanical behavior is highly dependent on the interfacial interaction between the components of the blend. Therefore, the objective of this work is to evaluate the compatibilizing effect of a low molar mass block copolymer (2000 g mol-1) derived from &#949;-caprolactone and polycarbonate (C2) and commercially available in PLA/PCL immiscible blends. Binary and ternary blends were prepared by mechanical mixing in the melted state via single-screw extrusion process. The content of PLA in the blends was 75, 50 and 25% (% by mass) and the copolymer concentration was 0, 1, 3, 5 and 7% (% by mass). The thermal, mechanical and morphological behavior of compatibilized and non-compatibilized blends was evaluated by differential scanning calorimetry (DSC), thermodynamic-mechanical analysis (DMTA), scanning electron microscopy (SEM), tensile test, flexion test, and Izod impact. The results of DSC and DMTA indicated that the copolymer caused a small reduction in the glass transition temperature (Tg) of PLA, suggesting that C2 is soluble in PLA. However, in the micrographies of the fracture surfaces of the PLA the presence of small micelles formed by the block copolymer is clear, indicating that there is a limit of solubility of the compatibilizer in the PLA phase. The results obtained in a tensile test showed that with the increase of the compatibilizing content, the tension in the flow, the tension at rupture and the elastic modulus of the blends undergo changes. The tenacity property, evaluated in the Izod impact test, showed that the blends had a gain in resistance when compared to pure PLA. The results showed that block copolymer derived from &#949;-caprolactone and aliphatic polycarbonate can act as a compatibilizer for PLA/PCL blends.

O Poli(ácido láctico) (PLA) é um polímero biodegradável, biocompatível e biorreabsorvível proveniente de fontes renováveis. Constitui uma excelente alternativa sustentável para os polímeros provenientes de petróleo, atualmente dominantes no mercado industrial. Porém, apresenta baixas ductilidade e tenacidade como principais limitações mecânicas. Um dos métodos mais utilizados para modificar essas propriedades é a mistura mecânica do PLA com polímeros flexíveis, como a poli(&#949;-caprolactona) (PCL). Entretanto, o alto desempenho mecânico de blendas PLA/PCL é difícil de ser atingido devido à imiscibilidade dos polímeros. A melhoria de propriedades, neste caso, só é conseguida por meio de compatibilização. Este trabalho visa avaliar o efeito compatibilizante do copolímero tribloco de baixo peso molecular derivado de &#949;-caprolactona e tetrametileno éter glicol disponível comercialmente em blendas imiscíveis de PLA com PCL. Blendas binárias e ternárias foram preparadas por mistura mecânica no estado fundido via processo de extrusão em rosca simples. O teor de PLA nas blendas variou em 75, 50 e 25% (% em massa) e a concentração do copolímero em 0, 1,5, 3 e 5% (% em massa). A avaliação morfológica e o comportamento térmico e mecânico das blendas PLA/PCL foram realizados por microscopia eletrônica de varredura (MEV), calorimetria exploratória diferencial (DSC), análise térmica dinâmico-mecânica (DMTA) e ensaios mecânicos de tração, flexão e impacto Izod. O efeito compatibilizante do copolímero foi mais bem observado nas blendas com 75% (% em massa) de PLA, enquanto que nas blendas com 50% e 25% (% em massa) de PLA esse efeito não foi tão evidente. Os resultados obtidos no ensaio de tração mostraram que com o aumento do teor de compatibilizante, a tensão no escoamento, a tensão na ruptura e o módulo elástico das blendas com 75% (% em massa) de PLA se mantiveram praticamente constantes, enquanto que a deformação na ruptura evoluiu de 20% na blenda com 1,5% (% em massa) de copolímero para 84% na blenda com 5% (% em massa) de copolímero. As análises morfológicas indicaram que o copolímero em bloco agiu na interface PLA/PCL, melhorando sua adesão. Esse resultado foi reforçado pelas análises térmicas, onde foi constatado que as Tg\'s e Tm\'s do PLA e do PCL nas blendas não apresentaram alterações, o que indica que o copolímero encontra-se na região interfacial da blenda. A resistência ao impacto Izod com entalhe, propriedade mecânica utilizada nesse trabalho como uma medida da tenacidade, da blenda PLA75C5 alcançou 42 J/m, valor significativamente superior ao determinado para o PLA puro, por volta de 28 J/m. Esses resultados mostram claramente que o copolímero tribloco derivado de &#949;-caprolactona e tetrametileno éter glicol é um eficiente compatibilizante para blendas PLA/PCL. / The Poly (lactic acid) (PLA) is a biodegradable, biocompatible and bioabsorbable polymer derived from renewable sources. It is an excellent sustainable alternative to polymers derived from oil, currently dominating the industry. However, PLA has low ductility and poor toughness as main mechanical limitations. Mechanical mixing of PLA with flexible polymers, such as poly (&#949;-caprolactone) (PCL), is one of the most used methods to modify these properties. However, a high mechanical performance of PLA/PCL blends is difficult to achieve due to the immiscibility of the polymers. The improvement of properties in this case is achieved only by compatibilization. This study aims to evaluate compatibilizer effect of a low molecular weight tri-block copolymer derived from &#949;-caprolactone and tetramethylene ether glycol, commercially available, on immiscible blends of PLA with PCL. Binary and ternary blends were prepared by mechanical blending in melt state through a single screw extrusion. The content of PLA in the blends ranged in 75, 50 and 25 wt% and the concentration of copolymer in 0, 1.5, 3 and 5 wt%. The morphological evaluation and the thermal and mechanical behavior of PLA/PCL blends were performed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and tensile test, flexural and Izod impact. The compatibilizer effect of the copolymer was more clearly observed in the blends with 75 wt% PLA, whereas in blends with 50 wt% to 25 wt% of PLA this effect was not so evident. The results of the mechanical tests showed that with the increase of the compatibilizer content, the yield stress, the stress at break and the elastic modulus of the blends with 75% (wt%) remained practically constant, while the elongation at break evolved from 20% in the blend with 1.5 wt% of copolymer to 84% in the blend to with 5 wt% of copolymer. Morphological analysis indicated that the block copolymer acted in the PLA/PCL interface, improving adhesion. This results were reinforced by thermal analysis, where it was found that the Tg and Tm of PLA and PCL in the blends showed no change, indicating that the copolymer is in the interfacial region of the blend. The Izod impact strength (Notched Izod), mechanical properties used in this work as a measure of toughness, of the blend PLA75C5 reached 42 J/m, significantly higher than the determined for pure PLA, about 28 J/m. These results clearly show that the triblock copolymer derived from &#949;-caprolactone and tetramethylene ether glycol is a good compatibilizer for blends PLA/PCL because it acts at the interfacial region, promoting the adhesion between the phases.

O poli(ácido láctico) (PLA) é um polímero biodegradável, biocompatível e bioabsorvível proveniente de fontes renováveis. Constitui uma excelente alternativa sustentável para substituição dos polímeros provenientes de petróleo, atualmente dominantes no mercado industrial. Apesar das vantagens, o PLA tem baixa tenacidade e reduzida elongação na ruptura a temperatura ambiente, o que torna a sua utilização limitada em usos que necessitem de alta deformação plástica em níveis de exigência mecânicos elevados. Misturas mecânicas de PLA com polímeros altamente flexíveis, como é o caso da poli(&#949;-caprolactona) (PCL), podem resultar em novos materiais com propriedades mecânicas adequadas para diferentes aplicações. Blendas PLA/PCL são completamente imiscíveis, sendo seu comportamento mecânico altamente dependente da interação interfacial entre os componentes da blenda. Portanto, o objetivo desse trabalho é avaliar o efeito compatibilizante de um copolímero em bloco de baixa massa molar (2000 g mol-1) derivado de &#949;-caprolactona e policarbonato (C2) e, disponível comercialmente em blendas imiscíveis PLA/PCL. Blendas binárias e ternárias foram preparadas por mistura mecânica no estado fundido via processo de extrusão em rosca simples. O teor de PLA nas blendas foi de 75, 50 e 25% (em massa) e a concentração do copolímero de 0, 1, 3, 5 e 7% (em massa). O comportamento térmico, morfológico e mecânico das blendas compatibilizadas e não compatibilizadas foi avaliado por Calorimetria Exploratória Diferencial (DSC), Análise Termodinâmico-Mecânica (DMTA), Microscopia Eletrônica de Varredura (MEV) e ensaios de tração, flexão e impacto Izod. Os resultados de DSC e DMTA indicaram que o copolímero provocou pequena redução na temperatura de transição vítrea (Tg) do PLA, sugerindo que o C2 é solúvel no PLA. Entretanto, nas micrografias das superfícies de fraturas do PLA foi nítida a presença de pequenas micelas formadas pelo copolímero em bloco, indicando que há um limite de solubilidade do compatibilizante na fase de PLA. Os resultados obtidos em tração mostraram que com o aumento do teor de compatibilizante, a tensão no escoamento, a tensão na ruptura e o módulo elástico das blendas sofrem alterações. A propriedade de tenacidade, avaliada no ensaio de impacto Izod, mostrou que as blendas tiveram um ganho na resistência quando comparadas com o PLA puro. Os resultados mostraram que o copolímero em bloco derivado de &#949;-caprolactona e policarbonato alifático pode atuar como compatibilizante para blendas PLA/PCL / Poly(lactic acid) (PLA) is a biodegradable, biocompatible and bioabsorbable polymer from renewable sources. It is an excellent sustainable alternative for replacing petroleum polymers, currently dominant in the industrial market. Despite the advantages, PLA has low toughness and reduced elongation at room temperature, which makes its use limited in uses that require high plastic deformation under high mechanical stress levels. Mechanical mixtures of PLA with highly flexible polymers, such as poly(&#949;-caprolactone) (PCL), may result in new materials with mechanical properties suitable for different applications. PLA/PCL blends are completely immiscible, and their mechanical behavior is highly dependent on the interfacial interaction between the components of the blend. Therefore, the objective of this work is to evaluate the compatibilizing effect of a low molar mass block copolymer (2000 g mol-1) derived from &#949;-caprolactone and polycarbonate (C2) and commercially available in PLA/PCL immiscible blends. Binary and ternary blends were prepared by mechanical mixing in the melted state via single-screw extrusion process. The content of PLA in the blends was 75, 50 and 25% (% by mass) and the copolymer concentration was 0, 1, 3, 5 and 7% (% by mass). The thermal, mechanical and morphological behavior of compatibilized and non-compatibilized blends was evaluated by differential scanning calorimetry (DSC), thermodynamic-mechanical analysis (DMTA), scanning electron microscopy (SEM), tensile test, flexion test, and Izod impact. The results of DSC and DMTA indicated that the copolymer caused a small reduction in the glass transition temperature (Tg) of PLA, suggesting that C2 is soluble in PLA. However, in the micrographies of the fracture surfaces of the PLA the presence of small micelles formed by the block copolymer is clear, indicating that there is a limit of solubility of the compatibilizer in the PLA phase. The results obtained in a tensile test showed that with the increase of the compatibilizing content, the tension in the flow, the tension at rupture and the elastic modulus of the blends undergo changes. The tenacity property, evaluated in the Izod impact test, showed that the blends had a gain in resistance when compared to pure PLA. The results showed that block copolymer derived from &#949;-caprolactone and aliphatic polycarbonate can act as a compatibilizer for PLA/PCL blends.

Orientador: Guilherme de Camargo Ferraz / Resumo: A descoberta de polímeros biodegradáveis influenciou a pesquisa biomédica. O poli (ácido lático) (PLA) e a Poli (Ɛ-caprolactona) (PCL) e suas blendas se tornaram foco de vários estudos por serem biodegradáveis e biorreabsorvíveis, particularmente em pesquisas envolvendo a implantação in vivo. Pelo presente, objetivou-se avaliar se o implante subcutâneo (SC) e intraperitoneal (IP) de PLA ou blenda PLA/ PCL são seguros, biocompatíveis e biodegradáveis em ratos machos Wistar. Os ratos foram distribuídos em cinco grupos avaliados em duas fases; aguda: -1, 1, 2, 7 e 14 dias e crônica: 2, 8 e 24 semanas após a implantação. Assim, estudaram se os grupos PLA (PLA puro), PLA/PCL (mistura PLA/PCL), instrumentado (GI), controle (C) e grupo controle inflamatório (CI). Para avaliar a biocompatibilidade utilizou-se teste comportamental de campo aberto (CA), filamentos de von Frey (FvF) e análises histopatológicas utilizando coloração de hematoxilina-eosina (HE) e picrosirius-hematoxilina (PSH). A biodegradação in vivo e degradação in vitro em solução de PBS a 37°C do PLA e PLA/PCL foram avaliadas por microscopia eletrônica de varredura (MEV). As comparações foram realizadas entre os grupos subdivididos conforme a implantação IP e SC. No teste CA, realizado dois dias após a implantação, o grupo CI demonstrou redução nas frequências de locomoção e levantar e aumento na frequência de grooming em relação aos grupos implantados PLA, PLA/PCL, GI pela via IP ou SC e grupo C. As avaliações de FvF ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The discovery of biodegradable polymers influenced biomedical research. Poly (lactic acid) (PLA) and poly (Ɛ-caprolactone) (PCL) and their blends have become the focus of several studies because they are biodegradable and bioreabsorbable, particularly in research involving implantation in vivo. The aim of this study was to evaluate whether the subcutaneous (SC) and intraperitoneal (IP) implantation of PLA or PLA / PCL blends are safe, biocompatible and biodegradable in male Wistar rats. The rats were distributed in five groups evaluated in two phases; acute: -1, 1, 2, 7 and 14 days and chronic: 2, 8 and 24 weeks after implantation. Thus, we studied whether the groups PLA (pure PLA), PLA / PCL (PLA / PCL mixture), sham (S), control (C) and inflammatory control group (IC). To evaluate the biocompatibility, the open field behavioral test (OF), von Frey filaments (FvF) and histopathological analyzes using hematoxylin-eosin (HE) staining and picrosirius-hematoxylin (PSH) were used. In vivo biodegradation and degradation in vitro in PBS solution at 37°C of PLA and PLA / PCL were evaluated by scanning electron microscopy (SEM). The comparisons were made between groups subdivided according to the IP and SC implementation. In the OF test, performed two days after implantation, the IC group demonstrated a reduction in the locomotion frequencies and augmentation and increase in the grooming frequency in relation to the PLA, PLA / PCL, sham implanted groups via IP or SC and C groups. FvF... (Complete abstract click electronic access below) / Mestre