RESUMEN El objetivo de esta tesis fue la obtención y caracterización de films biodegradables con características antimicrobianas y/o antioxidantes a partir de quitosano (CH). Para modular sus propiedades y mejorar su funcionalidad, se estudió la combinación con otras matrices poliméricas: almidón de trigo (WS), polivinil alcohol (PVA) y ácido poliláctico (PLA). Además se incorporaron aceites esenciales (EO) de tomillo (Th) o albahaca (B), ¿-tocoferol (Tp) y ácido cítrico (CA). Se evaluó el efecto del tratamiento de homogenización de las dispersiones formadoras de films (FFD) en films de quitosano con EO en diferentes proporciones. La microfluidización dio lugar a una reducción en el tamaño de gota, a una mayor carga superficial de las mismas y una menor viscosidad de las dispersiones. Además, intensificó todos los efectos provocados por la incorporación de EO sobre las propiedades mecánicas de los films debido a potenciación de las interacciones con el polímero. A baja proporción de EO, la microfluidización mejoró las propiedades de barrera al vapor de agua de los films, pero no tuvo un impacto significativo en la permeabilidad al oxígeno. Los films ejercieron un papel protector frente a la oxidación en grasa de cerdo. La presencia de EO en los films, a pesar de aumentar la permeabilidad al oxígeno, dio lugar a una menor velocidad de oxidación de las muestras (especialmente a alta humedad relativa), probablemente por el efecto antioxidante de los componentes de los EO. Los films de quitosano se mostraron efectivos en el control del deterioro microbiano cuando se aplicaron en carne de cerdo picada, pero la incorporación de los EO no mejoró su actividad antimicrobiana. Se incorporó CH en films de WS en diferentes proporciones. La adición de CH en cantidades crecientes dio lugar a un aumento en la viscosidad y estabilidad de las FFD. Ambos polímeros mostraron un alto grado de compatibilidad lo que dio lugar a una microestructura homogénea. El aumento de la proporción de CH dio lugar a films con mejores propiedades mecánicas ya que el CH pareció inhibir la retrogradación del almidón. Los films WS:CH dieron lugar a una reducción de la carga microbiana cuando se aplicaron en muestras de carne de cerdo picada. Se incorporaron diferentes antioxidantes (aceite esencial de tomillo y albahaca, ácido cítrico y ¿-tocoferol) en films mezcla de WS (80%) y CH (20%). Los films presentaron una microestructura heterogénea por la inmiscibilidad de componentes, principalmente el film con ¿-tocoferol que presentó separación de fases. Esto llevó asociado una superficie más rugosa, con menor brillo y, en el caso del ¿-tocoferol, un color más amarillo. No obstante la incorporación de antioxidantes conllevó un aumento de la transparencia y una disminución de la permeabilidad al oxígeno. El CA provocó un aumento en el módulo de elasticidad y un descenso de la extensibilidad de los films. La incorporación de CH en matrices de PVA dio lugar a films altamente homogéneos, debido a la compatibilidad de ambos polímeros. Se obtuvieron films más resistentes y rígidos, pero menos extensibles. Se observó una reducción del grado de cristalinidad y un aumento de la estabilidad térmica, además de una reducción de la trasmisión de la luz UV. Así mismo, cuando se aplicaron a muestras de carne de cerdo picada presentaron una acción antimicrobiana. La incorporación de CH en una matriz de PLA mediante extrusión no afectó al comportamiento térmico del PLA ni a su grado de cristalinidad. Ambos polímeros se mostraron incompatibles. La reducción del tamaño de las partículas de CH minimizó el impacto negativo sobre las propiedades mecánicas y de barrera al vapor de agua. En su aplicación a muestras de carne de cerdo picada, la presencia de CH mejoró las propiedades antimicrobianas de los films. / Bonilla Lagos, MJ. (2013). Desarrollo de films y recubrimientos comestibles bio-activos como soporte de agentes antioxidantes y antimicrobianos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28370 / TESIS

Teoretická část předložené dizertační práce popisuje princip radikálového roubování a faktory ovlivňující reakční průběh. Radikálové roubování poly(mléčné kyseliny) (PLA) reaktivní modifikací je vhodnou technikou přípravy biodegradabilních polymerních materiálů s rozličnými vlastnostmi. Současný stav problematiky modifikace poly(mléčné kyseliny) radikálovým roubováním v tavenině je obsahem literární rešerše včetně možných aplikací. Experimentální část se zabývá modifikací PLA anhydridem kyseliny itakonové (IAH) radikálovým roubováním v tavenině. Reakce byla iniciována 2,5-bis(tert-butylperoxy)-2,5-dimethylhexanem (L101). V první části je průběh radikálového roubování pozorován “in situ” pomocí diferenciální kompenzační kalorimetrie (DSC) a termogravimetrické analýzy (TGA). Exotermní pík na DSC záznamu odpovídá průběhu radikálové reakce, na jehož základě lze definovat aktivační energii reakce. Průběh TGA křivky “in situ” radikálové reakce umožňil detekovat vedlejší produkty vznikající v průběhu radikálové modifikace. Ve druhé části byla PLA funkcionalizována reakcí v diskontinuálním laboratorním mixéru za reakčních podmínek navržených dle poločasu rozpadu zvoleného iniciátoru a zpracovatelských podmínek PLA. Reakční teplota 190 °C byla stanovena výpočtem z Arrheniovy rovnice pro reakční čas 6 min. Uvedené reakční parametry byly zvoleny s ohledem na kinetiku rozkladu L101 a potlačení degradace PLA. Infračervená spektroskopie (FTIR) potvrdila navázání IAH na PLA řetězec na základě výskytu –CH2 vibrací s absorpčními pásy při vlnočtu 2860 a 2920 cm-1. Vzrůstající intensita absorpčního pásu 1750 cm-1 potvrdila přítomnost minoritních C=O vibrací anhydridového kruhu překrytých dominantními C=O vibracemi PLA řetězce. Nukleární magnetická rezonance (1H-NMR) nepotvrdila roubování oligomerního IAH na PLA. Koncentrace reaktantů ve zvoleném rozsahu (0.5–10 hm % IAH, 0.1–2 hm % L101) byla použita pro posouzení jejího vlivu na obsah naroubovaného IAH a míru vedlejších reakcí, např. -štěpení, větvení a síťování. Při vysoké koncentraci IAH a L101 byla potvrzena homopolymerace IAH i přes její zanedbávání v tématicky podobných studiích. Tvrzení o IAH homopolymeraci bylo podpořena výsledky kolorimetrické analýzy, charakterizací vzorků připravených polymerací IAH za podmínek radikálového roubování a termickou stabilitou frakcí extrahovaných z PLA-g-IAH. Radikálovou modifikací PLA došlo ke zvýšení flexibility polymerních řetězců díky objemné struktuře IAH navázané na PLA řetězci, což se projevilo poklesem teploty skelného přechodu (Tg). Zvýšený obsah amorfní fáze, hydrofilní chování, rozvětvená struktura a štěpení řetězců má pozitivní vliv na zvýšenou biodegradabilitu PLA-g-IAH v porovnání s nemodifikovanou PLA. Neradikálová degradace, probíhající v průběhu zpracování PLA, byla prokázána změnou tokových vlastností taveniny. Tento nežádoucí jev byl potlačen přídavkem tzv. “prodlužovače řetězců” obsahujícího reaktivní epoxy skupiny. Reakce mezi epoxy skupinami a karboxylovými skupinami byla potvrzena pomocí FTIR a změnou reologických vlastností PLA-g-IAH.

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.

Capsaicin, prostaglandin E2 (PGE2) and polydopamine (PDA) were used to target macrophage and myofibroblast activity to reduce biomaterial-induced fibrosis. The lifetime and efficacy of implantable biomedical devices are determined by the foreign body response. Immediately after implantation, proteins nonspecifically adsorb onto the material and initiate inflammation. Macrophages recruited to the site can differentiate into M1 and M2 phenotypes and upregulate inflammation and fibrosis which interferes with the intended function. M1 macrophages secrete pro-inflammatory mediators that induce chronic inflammation and promote myofibroblast differentiation while M2 macrophages are wound healing cells that suppress inflammation and regulate fibroblast activity. The fibrotic tissue is developed by myofibroblasts which produce collagen in an unregulated fashion. Collagen thickening and biomaterial encapsulation decreases efficacy and sensitive of biomedical devices. We investigated the in vitro and in vivo effects of capsaicin, PGE2 and polydopamine surface modification on macrophages and myofibroblasts. Capsaicin and PGE2 reduced poly(lactic-co-glycolic) acid (PLGA)-induced fibrosis by promoting M2 macrophage phenotype to secrete anti-inflammatory IL-10 and suppressing myofibroblast marker α-smooth muscle actin (α-SMA). Capsaicin decreased collagen by 40% and upregulated IL-10 secretion by 35% while PGE2 reduced collagen by 55% after 14 days of implantation and 40% less collagen after 42 days. PDA was used to bind an anti-fibrotic compound to the surface of a poly(dimethyl siloxane) (PDMS-PDA) to reduce fibrosis. However, PDMS-PDA controls gave an unexpected result by reducing fibrosis to the same extent as anti-fibrotic compound bound PDMS- v PDA. PDA modification reduced cellularity by 50% and significantly decreased collagen thickness by 30%. Overall, our results showed that biomaterial-induced fibrosis can be reduced by promoting M2 macrophage activity and inhibiting myofibroblast differentiation. This research demonstrates three compounds that have potential to reduce fibrosis and extend the lifetime and efficacy of implantable biomedical devices. / Thesis / Master of Applied Science (MASc) / Capsaicin, prostaglandin E2 (PGE2) and polydopamine were used to reduce scar tissue development around implanted polymers. Biomedical devices implanted in the body can undergo severe scar tissue formation, or fibrosis, and fail. Fibrosis is described by the accumulation of collagen and encapsulation of an implanted polymer. Macrophages regulate fibrosis by secreting pro-fibrotic compounds and myofibroblasts produce unregulated amounts of collagen. In this thesis, capsaicin, PGE2 and polydopamine were incorporated into implants to target macrophage and myofibroblast activity and reduce fibrosis in mice. Capsaicin and PGE2, released from a degradable polymer, altered macrophages to secrete anti-fibrotic compounds and decreased collagen by 40% and 55%, respectively. Polydopamine surface modified implants gave an unexpected result and suppressed overall cell activity to reduce fibrosis by 30%. The research conducted shows the potential of these compounds to reduce fibrosis and extend the lifetime of implantable devices.

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.