Thin film bilayers and blends composed of polymers and nanoparticles are increasingly important for technological applications that range from space survivable coatings to novel drug delivery systems. Dewetting or spontaneous hole formation in amorphous polymer films and phase separation in multicomponent polymer films can hinder the stability of these systems at elevated temperatures. Hence, fundamental understanding of dewetting and phase separation in polymer/nanoparticle bilayer and blend films is crucial for controlling transport and thermomechanical properties and surface morphologies of these systems. This dissertation provides studies on morphological evolution driven by phase separation and/or dewetting in model polymer/nanoparticle thin film bilayers and blends at elevated temperatures. Morphological evolution in dewetting bilayers of poly(t-butyl acrylate) (PtBA) or polystyrene (PS) and a polyhedral oligomeric silsesquioxane (POSS), trisilanolphenyl-POSS (TPP) is explored at elevated temperatures. The results demonstrate unique dewetting morphologies in both PtBA/TPP and PS/TPP bilayers that are significantly different from those typically observed in dewetting polymer/polymer bilayers. Upon annealing the PtBA/TPP bilayers at 95°C, a two-step dewetting process is observed. PtBA immediately diffuses into the upper TPP layer leading to hole formation and subsequently the holes merge to form interconnected rim structures in the upper TPP layer. Dewetting of both the TPP and PtBA layers at longer annealing times leads to the evolution of scattered holes containing TPP-rich, fractal aggregates. The fractal dimensions of the TPP-rich, fractal aggregates are ~2.2 suggesting fractal pattern formation via cluster-cluster aggregation. Dewetting in PS/TPP bilayers also proceeds via a two-step process; however, the observed dewetting morphologies are dramatically different from those observed in PtBA/TPP bilayers. Cracks immediately form in the upper TPP layer during annealing of PS/TPP bilayers at 200°C. With increasing annealing times, the cracks in the TPP layer act as nucleation sites for dewetting and aggregation of the TPP layer and subsequent dewetting of the underlying PS layer. Complete dewetting of both the TPP and PS layers results in the formation of TPP encapsulated PS droplets. Phase separation in PtBA/TPP thin film blends is investigated as functions of annealing temperature and time. The PtBA/TPP thin film blend system exhibits an upper critical solution temperature (LCST) phase diagram with a critical composition and temperature of 60 wt% PtBA and ~70°C, respectively. Spinodal decomposition (SD) is observed for 60 wt% PtBA blend films and off-critical SD is seen for 58 and 62 wt% PtBA blend films. The temporal evolution of SD in 60 wt% PtBA blend films is also explored. Power law scaling for the characteristic wavevector with time (q ~ t^n with n = -1/4 to -1/3) during the early stages of phase separation yields to domain pinning at the later stages for films annealed at 75, 85, and 95°C. In contrast, domain growth is instantly pinned for films annealed at 105°C. Our work provides an important first step towards understanding how nanoparticles affect polymer thin film stability and this knowledge may be utilized to fabricate surfaces with tunable morphologies via controlled dewetting and/or phase separation. / Ph. D.

Poly (caprolactone) (PCL) has been widely studied as a model system for investigating polymer crystallization. In this thesis, PCL crystallization along with other phase transitions in PCL-based polymer blends are studied as Langmuir films at the air/water (A/W) interface. In order to understand the phase behavior of PCL-based blends, surface pressure induced crystallization of PCL in single-component Langmuir monolayers was first studied by Brewster angle microscopy (BAM). PCL crystals observed during film compression exhibit butterfly-shapes. During expansion of the crystallized film, polymer chains detach from the crystals and diffuse back into the monolayer as the crystals "melt". Electron diffraction on Langmuir-Schaefer films suggests that the lamellar crystals are oriented with the chain axes perpendicular to the substrate surface, while atomic force microscopy (AFM) reveals a crystal thickness of ~ 7.6 nm. In addition, the competition between lower segmental mobility and a greater degree of undercooling with increasing molar mass produces a maximum average growth rate at intermediate molar mass. PCL was blended with poly(t-butyl acrylate) (PtBA) to study the influence of PtBA on the morphologies of PCL crystals grown in monolayers. For PCL-rich blends, BAM studies reveal dendritic morphologies of PCL crystals. The thicknesses of the PCL dendrites are ~ 7-8 nm. BAM studies during isobaric area relaxation experiments at different surface pressure reveal morphological transitions from highly branched dendrites, to six-arm dendrites, four-arm dendrites, seaweedlike crystals, and distorted rectangular crystals. In contrast, PCL crystallization is suppressed in PtBA-rich blend films. For immiscible blends of PCL and polystyrene (PS) with intermediate molar masses as Langmuir films, the surface concentration of PCL is the only factor influencing surface pressure below the collapse transition. For PS-rich blends, both BAM and AFM studies reveal that PS nanoparticle aggregates formed at very low surface pressure form networks during film compression. For PCL-rich blends, small PS aggregates serve as heterogeneous nucleation centers for the growth of PCL crystals. During film expansion, BAM images show a gradual change in the surface morphology from highly continuous networklike structures (PS-rich blends) to broken ringlike structures (intermediate composition) to small discontinuous aggregates (PCL-rich blends). / Ph. D.

Conventional studies of ionomers have focused on ionomers bearing monovalent carboxylate or sulfonate pendant ions. There are relatively fewer studies on ionomers containing multivalent pendant ions, such as divalent phosphonate. In this dissertation, poly(ethylene terephthalate) (PET) and polystyrene ionomers with divalent phosphonate pendant ions have been synthesized, and the influence of divalent phosphonate pendant ions on the structure-morphology-property relationship has been compared to the ionomers with monovalent sulfonate pendant ions. The phosphonate groups generated a stronger physically crosslinked network in phosphonated ionomers as compared to sulfonated analogues. Higher plateau modulus, longer relaxation time, and significantly higher zero-shear viscosity were noted for phosphonated ionomers by a dynamic melt rheology study. Compared to the ionic aggregates generated from sulfonate groups, larger ionic aggregates with associated phosphonate groups have been observed. Furthermore, phosphonated ionomers displayed significantly higher glass transition temperatures than sulfonated ionomers. Ionomers have proven to be attractive, interfacially active compatibilizers for a number of polymer blend systems because of specific interactions that may develop between the ionic groups and complementary functional groups on other polar polymers within the blends. The successful compatibilization of polyester/polyamide blends (prepared by solution mixing and melt blending methods) using phosphonated PET ionomers as a minor-component compatibilizer has been demonstrated. The phase-separated polyamide domain dimension decreased with increasing mol % phosphonated monomers and this decrease was attributed to the specific interactions between the ionic phosphonate groups on the polyester ionomer and the amide linkages of polyamide. More importantly, the divalent phosphonate pendant ions are more effective at compatibilizing polyester/polyamide blends in comparison to the monovalent sulfonate pendant ions. Phosphonated PET ionomer-compatibilized polyester/polyamide blends required 6 times fewer ionic monomers to achieve domain dimension < 1 μm as compared to sulfonated PET-containing blends. Deep eutectic solvents (DES) have been reported to be the next generation solvents due to the superior biocompatibility, biodegradability, and sustainability as compared to ionic liquids. Two types of deep eutectic solvents, choline chloride : malic acid (ChCl:MA) and L-arginine : levulinic acid (Arg:LA), have been demonstrated as effective plasticizers for poly(vinyl alcohol) (PVOH) films. The plasticization effects on the properties of PVOH films were evidenced by lower crystallizability and improved film ductility. In addition, ChCl:MA deep eutectic solvent was more effective in plasticizing PVOH as compared to propylene glycol, one of the most widely studied alcohol-type plasticizers. From an applied perspective, DES-plasticized PVOH film is a promising candidate in the packaging market of heath-related products. / Doctor of Philosophy / Non-covalent interactions play an important role on the structure-morphology-property relationship of polymeric materials. Divalent phosphonate pendant ions provide interesting effects on the properties of ionomer and polymer blends as compared to the monovalent sulfonate pendant ions. Ionomers containing phosphonate pendant ions exhibit a significantly stronger physically crosslinked network as compared to sulfonated ionomers. Compared to monovalent sulfonate groups, the divalent phosphonate groups are more effective at compatibilizing polymer blends. Furthermore, the compatibilized poly(ethylene terephthalate)-based blends exhibit improved optical and oxygen barrier properties compared to the base blend without compatibilizer, signifying potential benefits in packaging industry. Poly(vinyl alcohol) is one of the most widely used packaging materials for food, medicine, detergent, etc. The incorporation of deep eutectic solvents as plasticizers significantly improved film ductility. In addition, the plasticization effect for choline chloride-based deep eutectic solvent is more profound than one of the most widely studied alcohol-type plasticizers, propylene glycol. The effective plasticization of poly(vinyl alcohol) using deep eutectic solvents confirmed the potential for future applications in the packaging market of health-related product.

Physical aging measurements were performed on various polymeric glasses with the overriding goal of developing a better molecular picture of the nonequilibrium glassy state. To this end, aging-induced changes in mechanical properties and in the thermodynamic state (volume and enthalpy) were assessed for two different miscible polymer blends as a function of both composition and aging temperature. This investigation considered the physical aging behavior of blends containing atactic polystyrene (a-PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) as well as mixtures of poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). Substantial attractive chemical interactions are characteristic of a-PS/PPO blends but are absent in PMMA/SAN blends. The distinct nature of interactions for these two blends resulted in differences in the compositional dependence of secondary relaxation intensity, segmental cooperativity which dictates glass formation kinetics, and density (prior to aging). The variation of volume relaxation rate with aging temperature and composition was interpreted based upon these characteristics for the two systems. In addition, a general relationship was uncovered which linked structural relaxation rates for amorphous polymers to their respective segmental relaxation characteristics (glass transition cooperativity or fragility), which in turn are well understood from a molecular standpoint. This work, therefore, established a basis for comprehending glassy state volume and enthalpy relaxation rates based upon molecular characteristics. Developing an understanding of the connection between the evolving thermodynamic state and mechanical property changes fared less well. The fact that the thermodynamic and mechanical properties can have very different relaxation time responses governing their changes in the nonequilibrium glassy state was clearly evident in an extensive study of the physical aging characteristics of an amorphous polyimide material. For some materials, interpretation of mechanical aging behavior was obscured by thermorheological complexity arising due to overlap of a secondary relaxation with the main chain softening dispersion. / Ph. D.

This dissertation discusses results of crystallization kinetic, morphology and scattering studies on miscible semi crystalline blends of poly(pivalolactone)/ poly(vinylidene fluoride)(pPVLIPVF₂) and poly(pivalolactone)/poly(vinylidene fluoride <i>co</i>- tetrafluoroethylene)(95-5) (PPVL/P(VF2-TFE)(95-5)) prepared by solution blending. The spherulitic growth rates of the α-phase PPVL from miscible blends with PVF₂ or P(VF₂- TFE)(95-5) were measured by polarized optical microscopy as a function of blend composition and isothermal crystallization temperature, Tx, between 160°C and 215.5°C. The PPVL weight fraction in the blends ranged from 100 to 10 wt%. Using the Lauritzen-Hoffman kinetic theory of polymer crystal growth, the equilibrium melting temperatures of the α-phase PPVL in both the PPVL/PVF₂ and the PPVL/P(VF₂-TFE)(95-5) blends have been determined, for the first time, directly from the spherulitic growth rate data. Analysis of the composition dependence of the nucleation constant, Kg suggests that the α-phase PPVL crystal/melt lateral interface free energy, Ï , in the blends decreases markedly with increasing PVF₂ or P(VF₂-TFE)(95-5) concentration. / Ph. D.

Self-healing is an inherent property of living organisms, which poses a significant challenge for materials science. In recent years, self-repair mechanisms observed in plants have been recognized as promising models for the development of bio-inspired self-healing materials. The potential of biomimetic approaches to develop self-healing materials has been widely studied in the literature. In the field of composite materials, the concept of self-healing composites refers to the design of materials capable of autonomously restoring lost mechanical properties. The advantages of self-healing composites are numerous, including reduced maintenance and repair costs, and improved service life, leading to enhanced sustainability. Two types of self-healing composites have been extensively studied: extrinsic and intrinsic. This PhD Thesis focuses on investigating the intrinsic self-healing mechanism within polymer composites, which involves the ability of polymer matrices to heal micro-damage, such as cracks, under external stimuli. This Thesis aims to develop a thermoplastic matrix possessing self-healing properties using polyamide 6 (PA6), which is the most commonly utilized thermoplastic polymer in the production of thermoplastic composites. As there is a lack of systematic investigation on this particular research topic in the scientific literature, various combinations of PA6 and thermoplastic healing agents, along with different types of compatibilizers, were employed. The optimized matrix has been used for the manufacture of both short and long-carbon fiber composites. This PhD Thesis not only focuses on the production of thermoplastic self-healing composites but also investigates thermosetting intrinsic self-healing composites. Two distinct systems are examined, and in both cases, thermoplastic healing agents has been applied by depositing them on top of the fiber fabrics. A crucial aspect of this PhD Thesis is the fractography analysis, which enables an understanding of the reasons behind the failure of several healing mechanisms and the factors contributing to the success of other healing mechanisms. The PhD Thesis is divided into eight Chapters. Chapter I highlights the aim of this work together with the outline of the Thesis. Chapter II provides a brief introduction and the theoretical background of self-healing composites. Chapter III details all the experimental techniques utilized for the characterization of the polymer blends and for the characterization of the prepared composites. All the obtained results are thoroughly reported in Chapters IV-VIII. Chapter IV presents the results of PA6 with the combination of two different healing agents, i.e., Polycaprolactone (PCL) and Cyclic olefinic copolymer (COC) and it is subdivided into four different parts. The first investigated system was PA6/PCL and the latter was melt compounded with PA6 in different amounts. PCL caused a decrease in the mechanical properties of PA6, due to its immiscibility and low mechanical properties. Nevertheless, acceptable fracture toughness values in quasi-static mode were obtained. Samples were thermally mended at 80 and 100 °C, and the healing efficiency (HE) was assessed by comparing the fracture toughness of virgin and repaired samples both in quasi-static and in impact mode. The blend with a PCL content of 30 wt% showed limited HE values (up to 6%) in quasi-static mode, while interesting HE values (53%) were detected under impact conditions. This discrepancy was explained through microstructural analysis and correlated to a different fracture morphology. In fact, under quasi-static mode, the PA6 matrix was severely plasticized, while under impact a brittle fracture surface was obtained favoring thus the flow of PCL during the thermal healing process. The second investigated system was PA6/COC and the latter was melt compounded with PA6 in different amounts. From scanning electron microscope micrographs, it was possible to highlight the immiscibility and the lack of interfacial adhesion between the constituents. The HE of the system was evaluated by comparing the fracture toughness of the produced blends, both in quasi-static and impact mode, before and after the healing process performed at 140°C by applying a pressure of 0.5 MPa. Through the addition of 30 wt% of COC, the fracture toughness of the virgin samples slightly decreased, passing from 2.3 MPa·m1/2 of neat PA6 to 2.1 MPa·m1/2. However, the presence of the 30 wt% of COC homogeneously distributed within the PA6 matrix led to a HE of 11% in quasi-static mode and 35% in impact mode. From the analysis of these preliminary systems, it was decided that the best matrix/healing agent combination with the highest potential was the one reported by PA6/COC system. At this aim, since the lack of interfacial adhesion between the two different constituents severely decreased the healing performances of the system, different types of compatibilizers were selected in order to enhance the interphase between PA6 and COC. Three different types of compatibilizers were selected, i.e., poly(ethylene)-graft-maleic anhydride (PE-g-MAH), polyolefin elastomer-graft-maleic anhydride (POE-g-MAH), and ethylene glycidyl methacrylate (E-GMA), and thoroughly investigated in the third subchapter. The dynamic rheological analysis revealed that E-GMA played a crucial role in reducing interfacial tension and promoting PA6 chain entanglement with COC domains. Mechanical tests showed that PE-g-MAH and POE-g-MAH compatibilizers enhanced elongation at break, while E-GMA had a milder effect. A thermal healing process at 140 °C for 1 h was carried out on specimens broken in fracture toughness tests, performed under quasi-static and impact conditions, and HE was evaluated as the ratio of critical stress intensity factors of healed and virgin samples. All the compatibilizers increased HE, especially E-GMA, achieving 29% and 68% in quasi-static and impact conditions, respectively. SEM images of specimens tested in quasi-static conditions showed that all the compatibilizers induced PA6 plasticization and crack corrugation, thus hindering COC flow in the crack zone. Conversely, under impact conditions, E-GMA led to the formation of brittle fractures with planar surfaces, promoting COC flow and thus higher HE values. This study demonstrated that compatibilizers, loading mode, and fracture surface morphologies strongly influenced self-healing performance. From this study, it was evident that the best compatibilizer, in terms of HE performance, was E-GMA. For these reasons, it was decided to perform a fine-tuning of both the E-GMA content in the PA6/COC matrix and also a tuning of the temperature of the healing process. The experimental results of this investigation are reported in the fourth subchapter. From the capillary rheometer analysis, it was possible to assess that the addition of E-GMA improved both the melt strength (MS) and the breaking stretching ratio (BSR). The enhancement of these parameters reflected better processability and an improved capability of forming film by the optimized blend. From the performed fracture toughness tests, both in quasi-static mode and impact mode, it was possible to obtain, utilizing analysis of variance (ANOVA) statistics, the optimum E-GMA content, and healing temperature. The HE values in quasi-static mode at a healing temperature of 160 °C passed from 12 % for the non-compatibilized blend up to 38 % for the blend containing 5 wt% E-GMA. Passing to the performance in impact mode, the HE values at a healing temperature of 160 °C pass from 57 % for the non-compatibilized blend up to 82 % for the blend containing 5 wt% E-GMA. The differences in these two HE values for quasi-static conditions and impact mode were investigated through field emission scanning electron microscopy and it was noticed that the specimens tested in quasi-static mode showed severe plasticized fractured surfaces. On the other hand, the specimens tested in impact mode reported brittle fractured surfaces. The differences between the severely plasticized surfaces and the brittle surfaces explained the difference between the HE values of the two different tests. Severely plasticized surfaces hindered the flow of the healing agent during the thermal mending process, while the brittle surfaces allowed a better distribution of the healing agent during the thermal mending process. In conclusion, from the performed analysis, it was possible to obtain an optimized thermoplastic self-healing matrix to be used in structural composite applications. Chapter V presents the results of both short and long-carbon fiber composites produced by using the optimized self-healing thermoplastic blend detected in Chapter IV. The first investigated system was composed of short carbon fiber composite with self-healing properties. All the prepared compositions were produced in collaboration with the University of Pisa by means of a semi-industrial extruder, followed by an injection molding machine. Thanks to the remarkably high quality of the prepared specimens, the thermal mending capability was assessed through Charpy impact testing and plane-strain fracture toughness tests. The HE values of the self-healing composites were remarkable, and the system was successfully proven with HE values of approximately 10 % in quasi-static mode and approximately 50 % in Charpy impact tests. From the fractography analysis, it was possible to assess that the healing agent was capable of flowing in the crack plane but since, in both tests, a catastrophic rupture took place, the fiber integrity was thus lost. Thus, it was decided to perform fatigue testing and implement a statistical method found in the literature. In particular, a damage criterion was adopted to predict the fatigue life of these materials. Through the presented statistical approach, the Wöhler curves for both reinforced systems, i.e., the neat containing only PA6 and short carbon fibers and the self-healing short carbon fiber composites, were produced. Through the damaging/healing process, it was possible to highlight that the mending process was able to improve the fatigue life of the self-healing composites by approximately 77 %. The obtained results highlighted the potential of the self-healing composites in prolonging the fatigue life and therefore enhancing the working life of structural components. From the presented results it was highlighted that the prepared self-healing thermoplastic blend was capable of effectively repairing micro-damages and not catastrophic damages. The second investigated system was composed of long carbon fiber composites with self-healing properties prepared starting from the thermoplastic blend developed in Chapter IV. Long carbon fiber composites are prepared through film stacking and hot pressing process, the thermoplastic thin films were produced in collaboration with Professor Pietro Russo from the University of Naples by using an extruder equipped with a calender. A thorough analysis of the thermal and mechanical properties of these laminates highlighted the repair capabilities of PA6 and self-healing blend long carbon fiber laminates. The optical microscope revealed matrix-rich and fiber-rich regions, which could potentially undermine the mechanical integrity of the laminates due to incomplete impregnation of the carbon fiber by the matrices. However, pycnometer analysis confirmed that the void percentage within the composites remained acceptable for structural applications. The evaluation of the interlaminar shear strength (ILSS) through short beam shear (SBS) tests highlighted that there was no difference between the two different laminates. Through the thermal mending process, it was possible to demonstrate that the neat laminates were not able, as expected, to recover their mechanical properties. On the other hand, the self-healing laminates were capable of restoring the mechanical properties with a healing efficiency value of 104 %. From the analysis of the fracture surfaces, before and after the thermal mending process, it was possible to understand the reason behind the high value of healing efficiency. SBS tests induced mainly micro damages in the matrix and delamination. The damages were totally recovered upon the thermal mending process since there were no cracks or evident delamination on the observed specimens. In conclusion, this Chapter substantiated the efficacy of the developed thermoplastic self-healing blend in producing intrinsic self-healing composites. The self-healing laminates, with their superior tensile properties and robust self-healing performance, highlighted their potential for advanced applications in structural components with enhanced working life. Chapter VI reports the two different studies conducted on intrinsic self-healing thermosetting composites. The first investigated system was focused on the self-healing behavior of carbon fiber (CF) reinforced composites by depositing jet-spun COC meshes on dry carbon fiber plies before lamination with epoxy resin (EP). Three different laminates were prepared, including neat EP/CF and two composites with 4 wt.% and 8 wt.% in the form of a jet-spun COC network. The introduction of COC mesh reduced flexural stress by 26% and interlaminar shear strength by 50%. Mode I interlaminar fracture toughness was evaluated and specimens were mended at 110 °C by resistive heating generated by an electrical current flowing within the samples. The laminates containing 8 wt% COC reported a healing efficiency, evaluated as the ratio between the GIC and the maximum load of virgin and healed samples, of 9.4% and 33.7%, respectively. Fractography analysis highlighted the poor adhesion between the COC mesh and EP matrix, and several COC microfibers were trapped inside the epoxy matrix, hindering their diffusion inside the crack zone, which limited the healing capability of the prepared laminates. The second investigated system was based on the intrinsic-extrinsic self-healing laminates in which different healing agents were directly 3D printed on top of the fiber fabrics. Different amounts of thermoplastic healing agents were deposited through a specifically designed 3D printed process on top of fiber fabrics and with different percentages of covered area. Through vacuum assisted resin transfer molding (VARTM) process it was possible to produce, two reference laminates containing only carbon fibers and glass fibers, and laminates containing polyamide 11 (PA11), thermoplastic polyurethane (TPU) and PA11 with carbon nanotubes (PA11CNT). All the samples were labeled according to the following code “XX_YY_ZZ”, where “XX” stands for the selected reinforcements (CF or GF), “YY” stands for the thermoplastic polymer utilized, and “ZZ” stands for the percentage of the covered area by the thermoplastic polymers. A complete characterization of the thermal and mechanical properties was performed to assess the effect of the thermoplastic insertion on the physical properties of the composites. From the measurement of mode I fracture toughness, it was possible to assess the extremely positive effect of the healing agent on the GIC values. CF_PA11 laminates were demonstrated to be the best systems thanks to the toughening effect generated in the thermoplastic enriched plane. The fracture toughness was 674% higher with respect to the neat reference laminates in the case of the CF_PA11_36 system (GIC = 1641 J/m2). This exceptional result was attributable to the enhanced adhesion of the deposited thermoplastic pattern within the midplane laminae, while the large data scattering is related to the concomitant delamination processes induced in the adjacent planes. The same trend was recorded also for the CF_PA11_24 and the CF_PA11_12 laminates with a fracture toughness increase of 516 % and 359 %, respectively. On the other hand, for the TPU and PA11+CNTs laminates, the fracture toughness was marginally affected due to the possible degradation of TPU and the lack of interfacial adhesion of the PA11+CNTs thermoplastic healing agent with the GF. The specimens used for the determination of the mode I fracture toughness were healed at a temperature of 210 °C allowing the flow of the introduced healing agent in the crack plane thus restoring the loss of mechanical properties. The healing efficiency was successfully determined by calculating the variation of the fracture toughness upon the thermally activated healing cycles. In the considered analysis, the best systems were proved to be the CF_PA11_36 and the GF_PA11_CNTs laminates with a healing efficiency of 74%. Nevertheless, the best system was the one presenting the PA11 thermoplastic healing agent due to the much higher virgin fracture toughness value. Since the best system was the one composed of CF_PA11 laminates, several healing cycles were performed in order to assess the healing efficiency also for subsequent damage/healing processes. By evaluating the healing efficiency through the fracture toughness, it was possible to assess recovery of almost 50% after the three subsequent healing cycles for the CF_PA11_36 system. In conclusion, the results reported in this Chapter demonstrated that CF/epoxy laminates enriched with the 36% covered area pattern of PA11_20C were the best system in terms of both healing efficiency and fracture toughness. Chapter VII reported the final conclusion of the PhD Thesis and the general evaluation of the performances of the produced systems. Chapter VIII reported a summary of all the side activities performed during the PhD program.

Ces travaux de recherche portent sur le développement d’un procédé permettant de mélanger, directement en sortie de polycondensation, du polyamide fondu avec d’autres polymères immiscibles en tant qu’additifs. Ce procédé se distingue ainsi des méthodes d’élaboration conventionnelles pour lesquelles une fusion préalable des polymères est nécessaire. L’étude concerne le mélange de polymères de viscosités très différentes (polyamide 66 et polyéthylène glycol) et le mélange de polymères de viscosités similaires (polyamide 66 et copolymère d’éthylène propylène, en présence ou non d’un agent d’interface : polypropylène greffé par de l’anhydride maléique).Une première partie de ce travail a consisté à caractériser la dispersion de ces mélanges élaborés selon des procédés conventionnels. Ce travail a conduit à développer un modèle reliant la taille de la phase dispersée aux principaux paramètres opératoires de chaque procédé, pour le cas rarement recensé dans la littérature, des mélanges de polymères de viscosités très différentes.La seconde partie a été consacrée à la conception et à la réalisation d’une installation constituée d’un pilote de polycondensation équipé, en sortie de réacteurs, d’un dispositif de mélange reposant sur la technologie des mélangeurs statiques. Son fonctionnement a ensuite été éprouvé pour les deux mélanges considérés, grâce des expériences qui ont permis d’analyser l’influence de différentes conditions opératoires sur la morphologie des mélanges générés. La comparaison des résultats obtenus à ceux issus des procédés conventionnels, a alors permis de préciser les performances et les limites du procédé développé dans cette étude / The aim of this work is to develop a process, which enables to blend polyamide in molten state with others polymers, directly at the outlet of a polycondensation reactor. Contrary to currently industrial processes, no remelting stage is needed in this one. The study has been carried out with polyamide 66 / polyethylene glycol blends (products with very different viscosities) and with polyamide 66 / ethylene propylene blends (products with similar viscosities), with or without polypropylene-graft-maleic-anhydride as interfacial agent. The first part of this work deals with the characterization of the dispersions obtained for these blends when their elaborations are carried out using conventional processes. Only few studies are available on blends, which exhibit a large difference between components viscosity. This work led us to develop a model to correlate, in this case, the dispersed phase size to the main operating conditions of each processes.The second part is dedicated to the design and the realization of an experimental installation, which is composed of polycondensation plant equipped, at the outlet of reactors, with a blending device based on static mixers technology. Its operation has been tested and experiments have been carried out in order to study the influence of the different processing parameters on blends morphology. The comparison of the results with those previously obtained using conventional processes allowed then to precise the performances and the limits of the process developed in this study

A vasta gama de sistemas poliméricos classificados como blendas tem sido alvo crescente no meio acadêmico e científico. A possibilidade de obtenção de propriedades combinadas e múltiplas, associada a incorporações de blendas poliméricas, enriquece a condição de pesquisa abrindo assim uma extensa área de atuação. Neste trabalho foi proposto o estudo de mistura de composto de poli (cloreto de vinila) plastificado com resíduo de poli (vinil butiral), proveniente de laminados para produção de para-brisas da indústria automotiva, bem como a investigação do efeito da irradiação gama com dose absorvida de 25 kGy, 30 kGy e 40 kGy, controlado com uso de dosímetro de PMMA e taxa de dose equivalente de 0-10 kGy.h-1. Foram analisadas variações das propriedades mecânicas e térmicas das amostras antes e após exposição à radiação gama. As formulações foram constituídas em diferentes concentrações: composto de PVC-C, resíduo de PVB-R, PVC-C/PVB-R 90/10, PVC-C/PVB-R 50/50 e PVC-R/PVB-R 50/50. O composto de poli (cloreto de vinila) foi formulado e aditivado, apresentando comportamento de um elastômero termoplástico, produto flexível. Foram incorporadas aparas moídas de poli (vinil butiral), provenientes de laminados para produção de para-brisas. Ambos os materiais foram incorporados em extrusora granuladora tipo rosca simples e submetidos ao processo de calandragem para efetivação da mistura e formação de mantas plásticas. As mantas foram irradiadas em um reator multipropósito de 60Co e caracterizadas para verificação das propriedades mecânicas e térmicas. Para tanto, as blendas após exposição à radiação gama apresentaram propriedades mecânicas e térmicas intermediarias as propriedades dos seus componentes, mostrando-se um material resistente e de baixo custo. Por meio da microscopia eletrônica de varredura obteve uma redução nos vasos interfaciais mostrando um aumento na capacidade de percolação do PVB na matriz de PVC, favorecendo suas propriedades físicas. / The wide range of polymer systems classified as blends has been increasingly targeted in the academic and scientific milieu. The possibility of obtaining multiple and combined properties, combined with the incorporation of polymer blends, enriches the research condition, thus opening up an extensive area of performance. In this work the study of the poly (vinyl butyral) plasticized polyvinyl chloride mixture from laminates for automotive windshield production was investigated, as well as the investigation of the effect of gamma irradiation with absorbed dose of 25 kGy, 30 kGy and 40 kGy, controlled with use of PMMA dosimeter and equivalent dose rate of 0-10 kGy.h-1. Variations of the mechanical and thermal properties of the samples were analyzed before and after exposure to gamma radiation. The formulations were constituted in different concentrations: PVC-C compound, PVB-R residue, PVC-C/PVB-R 90/10, PVC-C/PVB-R 50/50 and PVC-R/PVB-R 50/50. The polyvinyl chloride compound was formulated and added, exhibiting the behavior of a thermoplastic elastomer, a flexible product. Poly (vinyl butyral) ground chips were produced from laminates for the production of windshields. Both materials were incorporated in a single-thread granulator extruder and submitted to the calendering process to effect the mixing and formation of plastic blankets. The blankets were irradiated in a 60Co multipurpose reactor and characterized for verification of mechanical and thermal properties. In order to do so, the blends after exposure to gamma radiation presented mechanical properties and intermediate thermal properties of their components, showing a resistant material and low cost. By means of the scanning electron microscopy it obtained a reduction in the interfacial vessels showing an increase in the percolation capacity of the PVB in the PVC matrix, favoring its physical properties.

A vasta gama de sistemas poliméricos classificados como blendas tem sido alvo crescente no meio acadêmico e científico. A possibilidade de obtenção de propriedades combinadas e múltiplas, associada a incorporações de blendas poliméricas, enriquece a condição de pesquisa abrindo assim uma extensa área de atuação. Neste trabalho foi proposto o estudo de mistura de composto de poli (cloreto de vinila) plastificado com resíduo de poli (vinil butiral), proveniente de laminados para produção de para-brisas da indústria automotiva, bem como a investigação do efeito da irradiação gama com dose absorvida de 25 kGy, 30 kGy e 40 kGy, controlado com uso de dosímetro de PMMA e taxa de dose equivalente de 0-10 kGy.h-1. Foram analisadas variações das propriedades mecânicas e térmicas das amostras antes e após exposição à radiação gama. As formulações foram constituídas em diferentes concentrações: composto de PVC-C, resíduo de PVB-R, PVC-C/PVB-R 90/10, PVC-C/PVB-R 50/50 e PVC-R/PVB-R 50/50. O composto de poli (cloreto de vinila) foi formulado e aditivado, apresentando comportamento de um elastômero termoplástico, produto flexível. Foram incorporadas aparas moídas de poli (vinil butiral), provenientes de laminados para produção de para-brisas. Ambos os materiais foram incorporados em extrusora granuladora tipo rosca simples e submetidos ao processo de calandragem para efetivação da mistura e formação de mantas plásticas. As mantas foram irradiadas em um reator multipropósito de 60Co e caracterizadas para verificação das propriedades mecânicas e térmicas. Para tanto, as blendas após exposição à radiação gama apresentaram propriedades mecânicas e térmicas intermediarias as propriedades dos seus componentes, mostrando-se um material resistente e de baixo custo. Por meio da microscopia eletrônica de varredura obteve uma redução nos vasos interfaciais mostrando um aumento na capacidade de percolação do PVB na matriz de PVC, favorecendo suas propriedades físicas. / The wide range of polymer systems classified as blends has been increasingly targeted in the academic and scientific milieu. The possibility of obtaining multiple and combined properties, combined with the incorporation of polymer blends, enriches the research condition, thus opening up an extensive area of performance. In this work the study of the poly (vinyl butyral) plasticized polyvinyl chloride mixture from laminates for automotive windshield production was investigated, as well as the investigation of the effect of gamma irradiation with absorbed dose of 25 kGy, 30 kGy and 40 kGy, controlled with use of PMMA dosimeter and equivalent dose rate of 0-10 kGy.h-1. Variations of the mechanical and thermal properties of the samples were analyzed before and after exposure to gamma radiation. The formulations were constituted in different concentrations: PVC-C compound, PVB-R residue, PVC-C/PVB-R 90/10, PVC-C/PVB-R 50/50 and PVC-R/PVB-R 50/50. The polyvinyl chloride compound was formulated and added, exhibiting the behavior of a thermoplastic elastomer, a flexible product. Poly (vinyl butyral) ground chips were produced from laminates for the production of windshields. Both materials were incorporated in a single-thread granulator extruder and submitted to the calendering process to effect the mixing and formation of plastic blankets. The blankets were irradiated in a 60Co multipurpose reactor and characterized for verification of mechanical and thermal properties. In order to do so, the blends after exposure to gamma radiation presented mechanical properties and intermediate thermal properties of their components, showing a resistant material and low cost. By means of the scanning electron microscopy it obtained a reduction in the interfacial vessels showing an increase in the percolation capacity of the PVB in the PVC matrix, favoring its physical properties.

Nos travaux sont consacrés à la fabrication, à la mise en œuvre et aux caractérisations de mélanges de polymères thermoplastiques thermostables destinés à des applications aéronautiques hautes températures. Le Poly(éther cétone cétone) PEKK, polymère semi-cristallin, a été choisi pour sa température de transition vitreuse (Tg) et son point de fusion (Tf) élevés. Les polyimides amorphes utilisés pour leur Tg élevée, sont le Poly(éther imide) PEI et le (polyimide) PI. Le but de ces mélanges est d’augmenter la Tg du PEKK, sans augmenter sa température de fusion. Ces travaux ont abouti à la caractérisation thermique, mécanique et rhéologique de chacun des polymères purs ainsi qu’à la définition d’un protocole de fabrication des mélanges. Les propriétés des mélanges ont alors été caractérisées par analyses thermomécaniques, par balayage calorimétrique différentiel et par des essais de traction afin de faire ressortir les meilleurs candidats pour les applications visées. Les modèles empiriques classiques de variation de la Tg prennent en compte seulement la composition des mélanges. Dans ce travail, nous proposons de corriger ceux-ci par la prise en compte de la variation du taux de cristallinité qui influe sur la composition de la phase amorphe et ainsi permettre une prévision plus fine de ce paramètre. La tenue au vieillissement à court terme des différents polymères dans un fluide aéronautique a aussi été abordée, et a montré que le PEKK a un effet protecteur sur les mélanges. / This PhD work presents the fabrication, processing and characterizations of thermoplastic thermostable polymer blends. It aims at finding new materials useable at high temperatures for aeronautical applications. Poly(ether ketone ketone), PEKK, a semi-crystalline polymer, has been chosen for its high glass transition temperature (Tg) and high melting point (Tf). Amorphous polyimides, that have been used for their high Tg, are Poly(ether imide), PEI, and Polyimide, PI. The aim of these blends is to increase the Tg of the PEKK without increasing its Tf. We have measured the thermal, mechanical and rheological properties of each neat polymer and the processing conditions of the blends have been defined. The properties of the blends have been characterized by thermomechanical analyses, differential scanning calorimetry and tensile tests to focus on the better candidates for the aimed applications. The classical empirical models of the Tg composition dependence take only into account the blends composition. We propose to correct them taking into account the crystallinity level, that affects the blends composition and predict a better prediction of the Tg . The short term ageing of these polymer blends specimens in a commonly used aeronautic fluid has also been studied, and showed the protection effect of the PEKK polymer in the blends.