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.

In an effort to produce new derivatives of cellulose for drug delivery applications, methods were developed to regioselectively modify C-6 halo cellulose esters to produce cationic derivatives via nucleophilic substitution. Reaction of C-6 substituted bromo and iodo cellulose with trialkylated amines and phosphines produced new cationic ammonium and phosphonium cellulose derivatives which can be explored as delivery agents for nucleic acids, proteins and other anionic drug molecules. It was anticipated that these new derivatives would not only be capable of complexing anionic drug molecules but would have greatly improved aqueous solubility compared to their precursors. The phosphonium derivatives described in this work are an obvious example of such improved solubility properties. Given the importance of cellulose derivatives in making amorphous dispersions with critical drugs, it has also been important to analyze commercially available polymers for the potential impact in oral drug delivery formulations. To do so pairwise blends of cellulosics and synthetic polymers commonly used as excipients were tested for miscibility using techniques such as DSC, mDSC, FTIR and film clarity. Miscible combinations highlight the potential to use combinations of polymers currently available commercially to provide drug delivery solutions for specific drug formulations. The use of melt extrusion in processing some of these drug/polymer dispersions provides a means of highlighting the capability for the use of these cellulosics in melt extruded amorphous dispersions. This solvent free, high pressure method significantly reduces cost and time and can be applied on a large scale. The analysis of long chain cellulose esters and ultimately the novel omega carboxy esters for melt processability significantly impacts the possibilities available for use of those excellent drug delivery agents on a much larger scale. / Ph. D.

Applying sizing material (poly n-vinylpyrrolidone or PVP) around graphite fibers enhances the mechanical properties of carbon fiber reinforced epoxy composites. Understanding the influence of the interphase region between the carbon fiber and epoxy matrix is crucial in enhancing the performance of carbon fiber reinforced epoxy composite materials. In this work, simulated interphase regions, in the form of pure and modified epoxies were synthesized in the laboratory. Several characterization techniques were used to identify the properties of these modified epoxies. They were: 1) Tensile Tests: 2) Fracture Toughness Tests; 3) Thermogravimetric Analysis (TGA): 4) Differential Scanning Calorimetry (nSC); 5) Fourier Transform Infrared (FTIR) Spectrometry: and ()) Water Absorption. Young's modulus, yield stress, yield strain. ultimate tensile stress. ultimate tensile strain, tensile toughness, fracture toughness, and strain energy release rate were obtained from tensile and fracture tests. DSC and FTIR experiments were employed in this study to show the miscibility of PVP and epoxy resin. The pure and modified epoxy samples were immersed in water for about a month to determine their water absorptivity. Almost all epoxies remained unchanged in stiffness, with the exception of the sample 40 wt. % PVP. Only the pure epoxy and light PVP loading epoxies exhibited yield points. The ultimate properties worsened significantly with the increase of PVP loading. A decreasing trend was found in fracture toughness as PVP loading increased. All pure and modified epoxies exhibited sharp glass transition temperatures and the T_g's followed the Fox prediction. Downward frequencies shifting of carhonyl and hydroxyl groups were obtained from the PVP/epoxy blends by infrared study. This was believed to show evidence of hydrogen bond formation. All epoxy and modified epoxies were swollen in water absorption experiments. The samples reached equilibrium after about one month and water absorptivity was found to be a function of PVP content. These experiments sought to demonstrate the characteristics of the interphase region of the composites. / Master of Science

No

Yes / Binary and ternary blends of a polylactic acid matrix with polycaprolactone (PCL) and polybutylene succinate (PBS) were produced by twin screw extrusion, containing up to 30 wt% loading. Mechanical, thermal and rheological characterisation techniques were used to quantify properties of the different blend formulations and miscibility was investigated using scanning electron microscopy. PCL is known to act as an impact modifier in PLA but to cause a corresponding reduction in strength. Results showed that addition of both PBS and PCL seperatly caused a reduction in melt viscosity, elastic modulus and tensile strength, but an increase in impact strength and strain at break. Analysis of morphology suggested that immiscibility was evident, particularly at higher PCL and PBS loadings. Results indicated that incorporation of a small loading of PBS had a synergistic effect on the PLA-PCL blend properties. Miscibility was improved and enhanced mechanical properties were observed for a ternary blend containing 5 wt% of both PBS and PCL compared to blends containing 10% of each polymer alone. / Financial support of Floreon- Transforming Packaging Ltd through the PhD sponsorship and materials provision.

Durch das Einbringen von Additiven, Füll- und Verstärkungsstoffen in eine polymere Matrix oder durch das Blenden unterschiedlicher Polymere ist es möglich, die Eigenschaften von Kunststoffen gezielt auf den Anwendungsfall hin zu optimieren. Gerade durch diese „Einstellbarkeit“ der Eigenschaften und infolge ihrer vergleichsweise geringen Dichte verdrängen Kunststoffe zunehmend klassische Werkstoffe und erobern so neue Anwendungsgebiete. Die Entwicklung solcher innovativer Kunststoffrezepturen (Compounds) ist jedoch zeitaufwendig und kostenintensiv. Um die gewünschten Gebrauchseigenschaften des Endproduktes zu erreichen, ist oft eine Vielzahl unterschiedlicher Zusatzstoffe erforderlich; somit werden entsprechende Rezepturen schnell sehr komplex. Bei der klassischen Materialentwicklung wird zumeist nicht erfasst/ermittelt, welche Synergien die einzelnen Bestandteile - positiver oder negativer Art - untereinander haben. Eine gezielte systematische Untersuchung dieser Synergien mit klassischen Methoden ist aus Kosten- und Zeitgründen kaum möglich. Für eine zeitgemäße Materialentwicklung sind daher neue Methoden gefragt, die eine schnelle Rezepturvariation, gepaart mit einem schnellen Eigenschaftsscreening, ermöglichen. Mit der Entwicklung des kombinatorischen Compoundier und High Throughput Screening Systems (CC/HTS-Systems) wurde im Rahmen dieser Arbeit eine, auch industriell einsetzbare, Basisanlage für die schnelle Entwicklung von neuen und innovativen Compoundrezepturen erstellt und hinsichtlich der Übertragbarkeit der Ergebnisse verifiziert. Das CC/HTS-System besteht aus: • einem Doppelschneckenextruder (ZSK 18 MegaLab) Eine entscheidende Besonderheit dieses System resultiert aus der Möglichkeit, die Materialzufuhr und damit die Zusammensetzung über rechnergesteuerte Dosierwaagen kontinuierlich zu verändern. Die im Vergleich zur klassischen Vorgehensweise somit vorhandene schnelle Rezepturänderung ermöglicht es in kürzester Zeit, eine große Rezepturvielfalt abzuarbeiten. • einer Flachfolienanlage Durch die direkte Kopplung der Flachfolienanlage mit der Folienextrusion wird der Rezepturgradient in einer Folie, im Sinne einer 1-dimensionalen Library „eingefroren“. • integrierten Prüfeinrichtungen Durch den Einsatz von in das System zu integrierenden unterschiedlichen HTS-Methoden ist eine schnelle und aussagefähige Charakterisierung der so hergestellten Rezepturen direkt online möglich. Erst diese im Rahmen dieser Arbeit entwickelten und validierten mechanischen Online-Prüfungen, als neue HTS-Methoden, ermöglichen durch deren Integration in das Gesamtsystem ein schnelles Materialscreening, indem die im Rahmen des CC hergestellten Folien (Library) online auf ihre mechanische Performance hin geprüft werden. Die mechanische Online-Prüfeinrichtung wurde so konzipiert, dass drei unterschiedliche Tests simultan in einer Vorrichtung durchgeführt werden. Hierbei handelt es sich um: • einen Durchstoßversuch, • einen Weiterreißversuch (wahlweise in oder travers zur Folienabzugsrichtung), • einen modifizierten Zugversuch (wahlweise in oder travers zur Folienabzugsrichtung). Anhand dieser drei zeitgleich online gemessenen Werkstoffkennwerte sind Aussagen über die wichtigsten mechanischen Eigenschaften - Steifigkeit, Zähigkeit und Festigkeit - abhängig von der Werkstoffzusammensetzung möglich. Die Prüfeinrichtungen für den Zug- und den Weiterreißversuch sind so konstruiert, dass sie sich je nach Entwicklungsaufgabe in der Prüfeinrichtung um 90° drehen lassen, um auch mechanische Eigenschaften in und/oder travers zur Folienabzugsrichtung zu ermitteln. Durch das Entfernen der Kerbmesser in der Prüfeinrichtung des Weiterreißversuchs lässt sich dieser zu einem zweiten Online-Zugversuch umrüsten, um z. B. gleichzeitig in und travers zur Folienabzugsrichtung die Zugfestigkeit zu erfassen. Hierdurch ist es möglich, in einem Prozessdurchlauf das anisotrope Werkstoffverhalten rezeptur- und prozessabhängig zu charakterisieren. Die Entwicklung der mechanischen Online-Prüfeinrichtung wurde durch stetige Validierung der Prüfergebnisse abgesichert. Als Ergebnis dieser Validierungsschritte ist festzuhalten, dass die online und offline ermittelten mechanischen Eigenschaften gut miteinander korrelieren. Eine entscheidende Frage beim CC war neben der Korrelierbarkeit der mechanischen Eigenschaften die Zuordnung der Rezepturzusammensetzung - welche sich kontinuierlich infolge der Gradientendosierung verändert - zu den online ermittelten Materialeigenschaften. Hierbei ist das Verweilzeitverhalten des Gesamtsystems, bestehend aus Extruder und Flachfolienanlage, zu berücksichtigen. Zur Beantwortung dieser Fragestellung wurden zunächst verschiedene theoretische Modelle auf ihre Anwendbarkeit hin untersucht. Es konnte gezeigt werden, dass das Double Backflow Cell Model die gewählte Versuchsanordnung am besten beschreibt. Als Ergebnis dieser theoretischen Überlegungen ist festzuhalten, dass für eine gute Korrelation von Rezepturzusammensetzung und online ermittelten Materialeigenschaften nur die System-Totzeit bei hinreichend langer Gradientenzeit zu berücksichtigen ist. Diese Arbeitshypothese konnte durch einen Versuch mittels Gradientenzugabe von Glasfasern von 0 w% auf 30 w% in Polypropylen und anschließender Glührückstandsbestimmung experimentell bestätigt werden. Im Anschluss an die Entwicklung und Validierung des Gesamtsystems (Gradientendosierung und mechanische Online-Prüfung) wurden die Möglichkeiten des CC/HTS-Systems anhand eines praxisrelevanten Zweistoffsystems, bestehend aus Polypropylen und verschiedenen POEs, welche sich im Viskositätsverhältnis zum Polypropylen und dem α-Olefin-Anteil unterscheiden, aufgezeigt. Durch das Blenden von Polypropylen mit einem Polyolefinelastomer (POE) lässt sich Polypropylen schlagzäh modifizieren. Bei einem solchen Blend aus zwei in der Regel nicht mischbaren Polymeren ist die sich einstellende Phasenmorphologie für das mechanische Werkstoffverhalten von entscheidender Bedeutung. Die Phasenmorphologie, also die Form und Größe der POE-Partikel, in der Polypropylenmatrix ist stark von der ausgewählten POE-Type abhängig. Um Aussagen zur Blendmorphologie zu erhalten, wurde im Rahmen dieser Untersuchungen die mechanische Online-Prüfung erstmals mit einer Online-Kleinwinkellichtstreuung als HTS-Methoden gekoppelt. Durch die Online-Kleinwinkellichtstreuung ist es möglich, simultan zu den mechanischen Eigenschaften auch online Rückschlüsse auf die Blendmorphologie zu erhalten. Diese Untersuchungen zeigten, wie die Morphologie und die mechanischen Eigenschaften korrelieren und welche Bedeutung der Auswahl der Blendpartner - des POEs – für das mechanische Werkstoffverhalten zukommt. Interessant war, dass die untersuchten Prozessparameter von untergeordneter Bedeutung für die Performance eines solchen Blends sind. Abschließend wurde die CC/HTS Methode auf eine industrielle Fragestellung - Dreistoffsystem bestehend aus Polypropylen/Glasfasern/Koppler – angewandt. Die Anwendbarkeit des Systems auch auf komplexere Werkstoffzusammensetzungen wurde dabei bestätigt. Es konnte gezeigt werden, dass mit Hilfe dieser Methode / Versuchseinrichtung die Compoundentwicklung deutlich beschleunigt und ressourcenschonender durchgeführt werden kann und die Ergebnisse mit den klassisch erarbeiteten Werten korrelieren.

Le caoutchouc naturel (NR) et le caoutchouc époxydé (ENR) ont constitué la base de cette étude consacrée à l’étude des composites et mélanges de polymères. La présence du groupe époxyde a conduit à une amélioration des propriétés mécaniques de ces formulations en termes de module et de la résistance à la traction. De plus, l’utilisation de la spectroscopie diélectrique a révélé que les ENRs présentent une conductivité plus élevée que le NR à basse fréquence et à haute température. En particulier, le caoutchouc naturel époxidé contenant 50 mol% de groupes époxyde ENR-50 présente des conductivités et permittivités les plus élevées. Par conséquent, ce dernier a été choisi pour préparer des composites polymères en incorporant des particules de titanate de barium (BT) et de noir de carbone (CB). Les résultats montrent que la permittivité et conductivité des composites élaborés augmentent avec le taux d'incorporation de ces charges. Par exemple, les composites BT/ENR-50 atteignent une permittivité élevée 48.7 pour 50 vol% de BT. De plus, les composites CB/ENR-50 présentent un seuil de percolation de 6.3 vol% de CB. Enfin les mélanges à base de poly(fluorure de vinylidène) (PVDF) et d’ENR ont été étudiés. Il a été observé que la morphologie de ces mélanges dépend du degré d’époxydation du caoutchouc naturel et bien entendu de la composition du mélange. Une morphologie co-continue peut être observée dans l’intervalle 40 et 60% en masse d’ENR-50. En outre, les résultats issus d’analyses dynamiques mécanique et diélectrique montrent que ces mélanges présentent une miscibilité partielle. Enfin, des composites à base de ces mélanges binaires PVDF/ENR- 50 contenant BT ont été préparés. L’étude des morphologies a révélé que les particules de BT étaient dispersées dans la phase d’ENR-50 pour le mélange classique. Cependant, les particules de BT sont localisées à l'interface et dans la phase PVDF pour le mélange réticulé dynamiquement. En termes de propriétés, la permittivité plus élevée est obtenue pour le mélange PVDF/ENR 50 (80/20) ayant été réticulé dynamiquement / Natural rubber (NR) and epoxidized natural rubber (ENR) were chosen to study the composites and blends of polymers. The presence of epoxide group caused to improve the mechanical properties in terms of modulus and tensile strength. Furthermore, dielectric spectroscopy revealed that ENR showed conductivity process at low frequency and high temperature. Epoxidized natural rubber containing 50 mol% of epoxide group or ENR-50 exhibited the highest dielectric permittivity and electrical conductivity. Therefore, ENR-50 was then selected to prepare polymer composite filled with barium titanate (BT) and carbon black (CB) particles. The permittivity and conductivity of the composites increased with the volume content of the fillers. The BT/ENR-50 composites reached a high permittivity of 4 8 . 7 for addition of 50 vol% BT. Meanwhile, CB/ENR-50 composite reached percolation threshold at 6. 3 vol% of CB. The phase development and miscibility of poly(vinylidene fluoride) (PVDF)/epoxidixed natural rubber (ENR) blends were then investigated. It was also found that phase structure depended on epoxidation level and blend compositions. The blend exhibited a co-continuous phase morphology in the region of 40 to 60 wt% of ENR-50. Furthermore, the results from dynamic mechanical and dielectric analysis revealed that these blends present a partial miscibility. Finally, the composites based on binary blends of PVDF/ENR-50 containing BT were prepared. The study of the morphologies revealed that BT was dispersed in ENR-50 phase in the case of simple blend. However, the addition of BT after dynamic vulcanization induced localization of BT in PVDF phase and at interface. The highest increment of permittivity can be observed for the composite based on dynamically cured PVDF/ENR-50 (80/20) blend / ศึกษาอิทธิพลของโครงสร้างโมกุลยางธรรมชาติ (NR) และยางธรรมชาติอิพอกไซด์ (ENR) ต่อสมบัติ พบว่าการมีหมู่อิพอกไซด์อยู่ในยาง ENR ทำให้มีการปรับปรุงสมบัติเชิงกล เช่น มอดุลัสและความต้านทานต่อแรงดึง นอกจากนี้สมบัติไดอิเล็กทริกได้แสดงให้เห็นถึงการนำ ไฟฟ้าที่ความถี่ต่ำและอุณหภูมิสูง ยางที่มีหมู่อิพอกไซด์ 50 โมล% (ENR-50) มีค่าการนำไฟฟ้า และค่า permittivity สูงที่สุด ดังนั้นจึงนำยาง ENR-50 ไปใช้ในการเตรียมคอมพอสิตที่ใช้แบเรียม ไททาเนตและเขม่าดำเป็นตัวเติม ซึ่งพบว่าค่า permittivity และค่าการนำไฟฟ้าสูงขึ้นตาม ปริมาณตัวเติมที่ใส่ลงไป ที่ปริมาณ 50%โดยปริมาตรของแบเรียมไททาเนตในยางให้ค่า permittivity สูงถึง 48.7 ในขณะเดียวกันก็พบว่าการเตรียม ENR-50 คอมพอสิตที่ใช้เขม่าดำมี percolation threshold ที่ 6.3 vol% ของเขม่าดำ สำหรับการศึกษาการเปลี่ยนแปลงของสัณฐาน วิทยาและความเข้ากันได้ของพอลิเมอร์เบลนด์ระหว่างพอลิไวนิลลิดีนฟลูออไรด์ (PVDF) กับยาง ENR พบว่า สัณฐานวิทยาของพอลิเมอร์ที่เตรียมได้ขึ้นอยู่กับปริมาณหมู่อิพอกไซด์ในยาง ENR และอัตราส่วนการเบลนด์ อัตราส่วนการเบลนด์ในช่วง 40 ถึง 60% โดยน้ำหนักของยาง ENR- 50 ให้ลักษณะสัณฐานวิทยาแบบวัฏภาคร่วม (co-continuous) นอกจากนี้ผลการทดสอบจาก สมบัติพลวัตเชิงกลและสมบัติไดอิเล็กทริกแสดงให้เห็นถึงความเข้ากันได้บางส่วน (partial miscibility) ท้ายที่สุดนี้ได้เตรียมคอมพอสิตจากพอลิเมอร์เบลนด์ที่เติมแบเรียมไททาเนต สัณฐานวิทยาของคอมโพสิทที่เตรียมได้นั้น พบว่าแบเรียมไททาเนตกระจายตัวในเฟสยางเป็น หลัก อย่างไรก็ตามการเติมแบเรียมไททาเนตหลังจากการวัลคาไนซ์แบบไดนามิกส์ทำให้ แบเรียมไททาเนตกระจายตัวในเฟสพอลิไวนิลลิดีนฟลูออไรด์ (PVDF) และที่ผิวประจัญ (interface) นอกจากนี้คอมพอสิตที่เตรียมจากเทอร์โมพลาสติกวัลคาไนซ์ของ PVDF/ENR 50 ที่ อัตราส่วนการเบลนด์ที่ 80/20 ให้ค่า permittivity ที่สูง

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<p>  </p> <p>With economies shifting towards net-zero carbon emissions, there is an increased interest in carbon-free energy carriers. Hydrogen is a potential carbon-free energy source. However, it poses several production, infrastructural, and safety challenges. Ammonia blends have been identified as a potential hydrogen carrier and fuel for gas turbine combustion. Partially cracked ammonia mixtures consist of large quantities of hydrogen that help overcome the disadvantages of pure ammonia combustion. The presence of nitrogen in the fuel blends leads to increased NO_x emissions, and therefore lean premixed combustion is necessary to curb these emissions. Understanding the flame features, precursors, and dynamics of blowout of such blends due to lean conditions is essential for stable operation, lean blowout prediction, and control. </p> <p><br></p> <p>In this study, high-fidelity large eddy simulations for turbulent premixed ammonia/hydrogen/nitrogen-air flames in an axisymmetric, unconfined, bluff-body stabilized burner are performed to gain insights into lean blowout dynamics. Partially cracked ammonia (40% NH₃, 45% H₂, and 15% N₂, by volume) is chosen as fuel since its laminar burning velocity is comparable to CH4-air mixtures. A finite rate chemistry model with a detailed chemical kinetic mechanism (36 species and 247 reactions) is utilized to capture characteristics of various species during blowout. A comprehensive study of the flow field and flame structure for a weakly stable burning at an equivalence ratio of 0.5 near the blowout limit is presented. Further, the effects of blowout on the heat release rate, vorticity, distribution of major species, and ignition radicals are studied at four time instances at blowout velocity of 70 m/s. Since limited data is available on turbulent premixed combustion of partially cracked ammonia, such studies are essential in understanding flame behavior and uncertainties with regard to blowout.</p>

Master of Science / Department of Civil Engineering / Kyle Riding / Corrosion of reinforcing steel is one of the most common and serious causes of reinforced concrete deterioration. While corrosion is normally inhibited by a passive layer that develops around the reinforcing steel due to the high pH environment of the surrounding concrete, chlorides will break down this protective layer, leading to reinforcement corrosion. Decreasing the diffusivity of the concrete would slow the ingress of chlorides into concrete, and is one of the most economical ways to increase the concrete service life. Optimized concrete mixtures blending portland cement and supplementary cementing materials (SCMs) have become popular throughout the construction industry as a method of improving both fresh and long-term concrete properties such as workability, strength and porosity. It has been shown that use of Class F fly ash, silica fume and ground granulated blast furnace slag (GGBFS) in binary concrete mixture blends can result in a significant reduction in concrete diffusivity. This study investigates the ability of Class C fly ash and ternary concrete mixture blends to also aid in diffusivity reduction. In order to study the effect of incorporation of SCMs into concrete, mixtures containing Class C and Class F fly ash, silica fume and GGBFS were tested following the ASTM C 1556 procedures to measure the concrete’s apparent chloride diffusivity. Structure life cycles were modeled using the measured apparent chloride diffusivities with two finite-difference based life-cycle analysis software packages. To determine whether a correlation between diffusivity and deterioration due to freezing and thawing exists, samples were also tested for their ability to resist deterioration from freezing and thawing cycles using a modified ASTM C 666 Procedure B test. Results show that the use of Class C fly ash yields some service life improvements as compared to the portland cement control mixtures, while ternary mixture blends performed significantly better than the control mixture and equal to or better than the binary SCM mixtures tested. Freeze-thaw tests showed all mixtures to be equally resistant to deterioration due to freezing and thawing.