The use of polymers in orthopaedics is steadily increasing. In some markets, such as spinal fusion and soft tissue anchors, the polymer polyetheretherketone (PEEK) is already the material of choice in the majority of implants. Despite PEEK’s widespread use, it is often associated with poor osseointegration, which can lead to implant loosening and ultimately failure of the device. Many attempts have been explored to improve the osseointegration of PEEK but none have had widespread clinical success. In this dissertation, a novel surface porous structure has been created, where limiting the porosity to the surface maintains adequate mechanical properties for load bearing applications while providing a surface for improved osseointegration. Careful control of the processing parameters resulted in tunable porous microstructures optimized for bone ingrowth: highly interconnected 200-500µm pores with porosity ranging from 60-85% and pore layers from 300-6000µm thick. Mechanical characterization, including monotonic tensile and compression, tensile fatigue, shear, and abrasion tests, were used to probe the effects of the surface porosity on the relevant mechanical properties of the material. In addition, the effect of surface porosity and surface roughness on the mechanical properties of a range of thermoplastics with varying chemistries and crystallinities was explored. This research showed that there is a great disparity in the notch sensitivity of polymers that correlates to the polymers fracture toughness as well as trends in the monotonic stress-strain curve. The results illustrate that care must be taken in the design of polymeric implants, especially when introducing topographical changes to promote osseointegration, in order to ensure they maintain adequate load-bearing capacity. Finally, preliminary in vitro and in vivo data demonstrated the ability of surface porous PEEK (PEEK-SP) to promote osseointegration. Cells grown on PEEK-SP demonstrated enhanced mineralization and differentiation, suggesting the ability of PEEK-SP to facilitate bone ingrowth. The potential of PEEK-SP was further demonstrated by implantation in a rat femoral segmental defect model which demonstrated bone ingrowth and reduced formation of a fibrous capsule.

Polyetheretherketone (PEEK) is a Federal and Drug Administration (FDA) approved biomaterial that has been used as an orthopedic implant material due to its inherent properties. Laser etching has become a popular means to create identication markers on the individual implants as required by the FDA. The interaction of laser energy with polymeric materials could potentially cause changes in the material's biocompatibility and mechanical properties. The objective of this study was to determine the effect of laser energy on the biocompatibility and mechanical properties of implantable PEEK by measuring contact angle, micro-tensile testing, nite-element modeling (FEM), and biocompatibility testing according to International Organization for Standardization (ISO) 10993 for cytotoxicity. The results of the study showed that the etching characteristics were mostly in by the laser power and the laser pulse spacing. The mechanical properties were degraded by the laser and the tensile strength of the material was decreased by 50% is some cases. The laser, however, did not affect the biocompatibility. The biocompatibility testing of the material showed no cytotoxic effect using an agar overlay method. The contact angle measurements demonstrated that the laser etching produced a hydrophobic effect to the surface. The FEM model demonstrated a good correlation between the laser power and the vaporization of the PEEK material. The results of the study showed the effect of laser energy on biocompatibility and mechanical properties.

Polyetheretherketone (PEEK) is a designation given to materials of the polyaryletherketone family having a characteristic distribution of ether and ketone groups in the polymer backbone. PEEK materials have high strength and chemical resistance as well as very high melting points and glass transition temperatures. Because of this combination of properties, PEEK materials find use for wear application in extreme environments where they provide a light-weight and corrosion resistant bearing material that often does not require lubrication. An initial study focused on determining the effects of supplier and molecular weight on the wear of particular PEEK materials, in addition to the effect of contact pressure. This work is significant because it highlights the fact that tribologically relevant polymers, such as PEEK materials, vary greatly in terms of their polymer morphology and processing history, and this variation must be recognized by investigators when reporting wear data. Because of their light weight, chemical resistance, and self-lubricating properties, polymers are used in applications ranging from biomedical to aerospace. Some polymers exhibit significant differences in wear resistance based on whether they are in unidirectional or multidirectional sliding. Shear induced polymer chain orientation is believed to be responsible for this behavior. Polyetheretherketone (PEEK) has excellent wear resistance, but its multidirectional sliding behavior has not been thoroughly investigated. A factorial multidirectional pin-on-plate wear study of PEEK was conducted with a focus on molecular weight and sliding path directionality. These factors were studied for their correlation to overall wear performance. Additionally, transfer film thickness was measured at locations along the wear path using white light interferometry. A result of this work has been a greater understanding of PEEK wear mechanisms in various sliding configurations and how they relate to transfer film formation. A major outcome was the development of a quantitative metric to describe transfer film thickness and continuity. It was found that thinner more continuous transfer films form under sliding conditions that change direction rather than overlapping along the same path. The thinner more continuous transfer film was found to also correspond with statistically lower wear behavior. Scanning electron microscope (SEM) investigation of the transfer film and pin wear surface confirmed the relationship between transfer film quality and wear.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24836号 / 医博第5004号 / 新制||医||1068(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 安達, 泰治, 教授 森本, 尚樹, 教授 上杉, 志成 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Yes / Polyetheretherketone (or PEEK) is a thermoplastic polymer known for its high plasticity and toughness and has been widely employed as a material for a variety of load-bearing medical devices ranging from trauma implants to interspinal spacers and femoral stems. While being inherently chemically inert and therefore biocompatible and having very short lived post-radiation free radicals, PEEK presents different mechanical properties depending on its degree of crystallinity. It can be processed via extrusion, injection or compression moulding. However, these techniques do not allow high precision control over the fine morphological structure that strongly influences mechanical properties. Microinjection moulding, in contrast, makes it possible to produce fine details of medical implants with high precision and accuracy. Another advantage of this method is the controlled production of the material with heterogeneous structure due to variations in crystallinity. Having stiffness in the middle of the sample different from that at the edges enables a structure that mimics the bone/cartilage parts of an implant. This paper reports on the manufacturing of PEEK components by microinjection moulding, and their characterisation by physico-chemical (XRD, SAXS, TEM, FTIR, POM) and mechanical (tensile testing) means, in order to assess the suitability of use for biomedical application, such as spinal implants. We discuss the influence of such parameters as mould temperatures, injection speeds and hold pressures on the crystallinity and mechanical properties of the material. / Science Bridges: Bradford-China Programme for Pharmaceutical Sciences and Medical Technology, EP/G042365/1

Intensive research on development of alternative low cost, high temperature membranes for proton exchange membrane (PEM) fuel cells is going on because of the well-known limitations of industry standard perfluoro-sulfonic acid (PFSA) membranes. To overcome these limitations such as the decrease in performance at high temperatures (&gt / 80 0C) and high cost, non-fluorinated aromatic hydrocarbon based polymers are attractive. The objective of this study is to develop alternative membranes that possess comparable properties with PFSA membranes at a lower cost. For this purpose post-sulfonation studies of commercially available engineering thermoplastics, polyether-ether ketone (PEEK) and polyether-sulfone (PES), were performed by using suitable sulfonating agents and conditions. Post sulfonated polymers were characterized with proton nuclear magnetic resonance spectroscopy (H+-NMR), sulfur elemental analysis and titration to calculate the degree of sulfonation (DS) values and with TGA and DSC for thermal stability and glass transition temperature (Tg). Chemical stabilities were evaluated by hydrogen v peroxide tests. Proton conductivities of sulfonated PEEK (SPEEK) measured by electrochemical impedance spectroscopy (EIS) were observed to increase linearly with degree of sulfonation (DS). However, above a certain DS SPEEK loses its mechanical stability significantly with excessive swelling which leads to deteriorations in mechanical stability. Therefore, DS of 50-70% were used for the fabrication of composite membranes. To improve mechanical stability, SPEEK polymers were blended with more stable polymers, polyether-sulfone (PES) or in its sulfonated form (SPES) or with polybenzimidazole (PBI). In addition, the composite approach, which involves the incorporation of various inorganic fillers such as zeolite beta, TiO2, montmorrilonite (MMT), heteropolyacids (HPA), was used for further improvement of proton conductivity. Among the composite membranes 20% TPA/SPEEK (DS=68) composites conductivity value exceeded that of Nafion&lsquo / s at room temperature. Effects of various parameters during the fabrication process such as the filler type and loading, DS of sulfonated polymer, casting solvents, and thermal and chemical treatment were also investigated and optimized. Various blend/composite membranes were fabricated with solvent casting method, and characterized for their proton conductivity, chemical/thermal stability and for evaluating their voltage/current performance at various temperatures in a single cell setup. Chemically and thermo-hydrolytically stable composite/blend membranes such as 25% tungstophosphoric acid (TPA)/PBI(5%)/SPEEK (DS=68) with good single cell performances at 800C were developed (~450 mA/cm2 at 0.5 V). The performance of the hydrolytically stable composite/blend membrane prepared with SPEEK (DS=59) / 5% PBI / and 10% TiO2 increased appreciably when the temperature was raised from 80 0C to 90 0C while the performance of Nafion decreases sharply after 80 0C. Methanol permeability studies were also performed for investigating the potential of fabricated blend/composite membranes for direct methanol fuel cell (DMFC) use. Selectivities (conductivity/methanol permeability) vi greater than Nafion 112 (S=7.3x107) for DMFC were observed for composite/blend membranes such as 10% TiO2/10% PES blend with SPEEK (DS=68) with a selectivity of 9.3x107. The factors that affect proton conductivity measurements were investigated and equivalent circuit analysis was performed with results obtained by electrochemical impedance spectroscopy (EIS). The choice of the conductivity cell (electrodes, cell geometry) and the method (2-probe vs 4-probe) were shown to affect the conductivity analysis. A systematic development and characterization route was established and it was shown that by optimizing proton conductivity and thermal/chemical stability with blending/composite approaches it is possible to produce novel high performance proton exchange membranes for fuel cell applications.

In der Zahnmedizin werden endodontische Instrumente aus metallischen und polymeren Werkstoffen zur Desinfektion infizierter Wurzelkanalsysteme eingesetzt. Durch den Einsatz von Polymeren ergeben sich aufgrund ihrer günstigen Werkstoffeigenschaften die Vorzüge einer minimal invasiven Arbeitsweise und einer geringeren Bruchgefahr. Demgegenüber besitzen die eingesetzten metallischen Instrumente durch hochfrequente Oszillationen eine verbesserte Reinigungswirkung. Zur Auslegung optimierter polymerbasierter Instrumente, die zuverlässig reinigen, wird daher eine simulationsbasierte Entwicklungsmethode erarbeitet. Ausgangspunkt hierfür ist die ingenieurwissenschaftliche Analyse der methodischen und experimentellen Grundlagen des Gesamtsystems. Die Beschreibung des instationären Schwingungsverhaltens der Instrumente erfolgt durch dynamische Finite-Elemente-Analysen unter Verwendung eines viskoelastischen Materialmodells. Das dazu erforderliche Materialverhalten des ausgewählten Polymers Polyetheretherketon wird mithilfe eines neu entwickelten Prüfaufbaus charakterisiert. Das erarbeitete Simulationsmodell ermöglicht erstmalig eine Analyse des kontaktmechanischen Verhaltens polymerer Miniaturstrukturen unter hochfrequenter Schwingungsanregung. Im Ergebnis steht mit diesem Modell eine realitätsnahe Beschreibung des Schwingungsverhaltens und der auftretenden Beanspruchungen zur Verfügung. Die gewonnenen Erkenntnisse leisten einen wesentlichen Beitrag zur gezielten, werkstoffgerechten und schwingungsoptimierten Auslegung von zukünftigen zahnmedizinischen Instrumenten zur Wurzelkanalreinigung.:1 Einleitung 1.1 Literaturübersicht 1.2 Problemstellung und Zielsetzung 2 Thermoplastische Polymere für die Anwendung in endodontischen Instrumenten 2.1 Mechanische und technische Anforderungen 2.1.1 Bestimmung einer repräsentativen Wurzelkanalgeometrie 2.1.2 Schwingungstechnik und Aufbau von Reinigungsansätzen 2.1.3 Werkstoffauswahl für Reinigungsansätze 2.1.4 Fertigungstechnologien für Miniaturstrukturen aus PEEK 2.2 Biologische und mechanische Wechselwirkungen 2.2.1 Verhalten gegenüber desinfizierenden Spüllösungen 2.2.2 Tribologie der Wurzelkanalreinigung 3 Analyse des zyklischen Verformungsverhaltens von PEEK 3.1 Phänomenologische Beschreibung des Verformungsverhaltens 3.1.1 Klassifizierung des Materialverhaltens 3.1.2 Elastische Verformung thermoplastischer Polymere 3.1.3 Mechanische Dämpfung 3.2 Experimentelle Untersuchungen 3.2.1 Probekörper 3.2.2 Versuchsaufbau und Durchführung 3.2.3 Voruntersuchungen 3.2.4 Ergebnisse der experimentellen Untersuchungen 4 Modellierung des zyklischen Deformationsverhaltens von PEEK 4.1 Einachsige rheologische viskoelastische Materialmodelle 4.1.1 Allgemeine konstitutive Gleichungen 4.1.2 Einachsige rheologische Grundelemente 4.1.3 Einachsige rheologische Modelle 4.1.4 Vergleich der einachsigen rheologischen Modelle 4.2 Charakterisierung des viskoelastischen Materialverhaltens 4.2.1 Analytische Beschreibung der Balkenschwingung 4.2.2 Resonanzkurvenverfahren 4.2.3 Bestimmung der Materialparameter von PEEK 4.3 Numerische Implementierung eines mehrachsigen Materialmodells 4.3.1 Mehrachsiges Materialmodell 4.3.2 Validierung des implementierten Materialmodells 5 Simulation des Schwingungsverhaltens und experimentelle Verifikation 5.1 Numerische Simulationsmodelle 5.1.1 Geometrische Modelle 5.1.2 Rand- und Anfangsbedingungen 5.1.3 Kontaktmodellierung 5.2 Simulationsergebnisse 5.2.1 Schwingungsverhalten ohne Oberflächenkontakt 5.2.2 Schwingungsverhalten mit Oberflächenkontakt 6 Zusammenfassung Literaturverzeichnis A Experimentelle Voruntersuchungen B Klassische Balkentheorie / In dentistry, endodontic instruments made of metallic and polymer materials are used for the disinfection of infected root canal systems. Due to their beneficial material properties, the use of polymers offers the advantages of a minimally invasive operation and a lower risk of breakage. In contrast, the metallic instruments used have an improved cleaning efficiency due to high-frequency oscillations. A simulation-based development method for the design of optimized polymer-based instruments that clean effectively is therefore being worked out. As starting point, an engineering analysis of the methodological and experimental fundamentals of the overall system has been carried out. The description of the instrument’s transient vibration behavior is performed by dynamic finite element analyses using a viscoelastic material model. The required material behavior of the selected polymer polyetheretherketone is characterized with the aid of a newly developed test setup. The resulting simulation model allows for the first time an analysis of the contact mechanical behavior of polymeric miniaturized structures under high-frequency vibration excitation. As a result, this model provides a realistic description of the vibration behavior and the stresses that occur. The knowledge gained will make a significant contribution to the targeted, material-specific and vibration-optimized design of future dental instruments for root canal irrigation.:1 Einleitung 1.1 Literaturübersicht 1.2 Problemstellung und Zielsetzung 2 Thermoplastische Polymere für die Anwendung in endodontischen Instrumenten 2.1 Mechanische und technische Anforderungen 2.1.1 Bestimmung einer repräsentativen Wurzelkanalgeometrie 2.1.2 Schwingungstechnik und Aufbau von Reinigungsansätzen 2.1.3 Werkstoffauswahl für Reinigungsansätze 2.1.4 Fertigungstechnologien für Miniaturstrukturen aus PEEK 2.2 Biologische und mechanische Wechselwirkungen 2.2.1 Verhalten gegenüber desinfizierenden Spüllösungen 2.2.2 Tribologie der Wurzelkanalreinigung 3 Analyse des zyklischen Verformungsverhaltens von PEEK 3.1 Phänomenologische Beschreibung des Verformungsverhaltens 3.1.1 Klassifizierung des Materialverhaltens 3.1.2 Elastische Verformung thermoplastischer Polymere 3.1.3 Mechanische Dämpfung 3.2 Experimentelle Untersuchungen 3.2.1 Probekörper 3.2.2 Versuchsaufbau und Durchführung 3.2.3 Voruntersuchungen 3.2.4 Ergebnisse der experimentellen Untersuchungen 4 Modellierung des zyklischen Deformationsverhaltens von PEEK 4.1 Einachsige rheologische viskoelastische Materialmodelle 4.1.1 Allgemeine konstitutive Gleichungen 4.1.2 Einachsige rheologische Grundelemente 4.1.3 Einachsige rheologische Modelle 4.1.4 Vergleich der einachsigen rheologischen Modelle 4.2 Charakterisierung des viskoelastischen Materialverhaltens 4.2.1 Analytische Beschreibung der Balkenschwingung 4.2.2 Resonanzkurvenverfahren 4.2.3 Bestimmung der Materialparameter von PEEK 4.3 Numerische Implementierung eines mehrachsigen Materialmodells 4.3.1 Mehrachsiges Materialmodell 4.3.2 Validierung des implementierten Materialmodells 5 Simulation des Schwingungsverhaltens und experimentelle Verifikation 5.1 Numerische Simulationsmodelle 5.1.1 Geometrische Modelle 5.1.2 Rand- und Anfangsbedingungen 5.1.3 Kontaktmodellierung 5.2 Simulationsergebnisse 5.2.1 Schwingungsverhalten ohne Oberflächenkontakt 5.2.2 Schwingungsverhalten mit Oberflächenkontakt 6 Zusammenfassung Literaturverzeichnis A Experimentelle Voruntersuchungen B Klassische Balkentheorie

Die Analyse von Implantat-Gewebe-Wechselwirkungen basiert derzeit hauptsächlich auf histologischen Techniken. Der invasive Charakter der histologischen Präparation lässt allerdings keine Untersuchung am lebenden Tier zu. Dadurch ist es nicht möglich, den Prozess der Implantateinheilung wiederholt an einem Tier zu beobachten. Die Folgen sind eine hohe Anzahl aufzuwendender Versuchstiere und eine Vergrößerung der Messunsicherheit infolge der gestiegenen biologischen Variabilität. Nicht-invasive, bildgebende Verfahren spielen daher eine zunehmende Rolle für die Entwicklung neuer Biomaterialien. Während die Computertomographie (CT) häufig zur Untersuchung der knöchernen Implantateinheilung verwendet wird, hat sich die Nutzung der Magnetresonanztomographie (MRT) für diese Fragestellungen bisher nicht etabliert. Bei der Magnetresonanztomographie handelt es sich, analog zur Computertomographie, um ein bildgebendes Verfahren zur nicht-invasiven Erzeugung digitaler Schnittbilder. Im Gegensatz zur CT, die das Hartgewebe abbildet, wird bei der MRT das Weichgewebe detektiert, wobei keine ionisierende Strahlung verwendet wird. Der große Vorteil der MRT gegenüber anderen bildgebenden Methoden besteht darin, dass es möglich ist, das Weichgewebe auf den Schnittbildern anhand verschiedener Kontraste darzustellen. Zusätzlich können MR-spezifische Parameter quantifiziert werden, die einen direkten Rückschluss auf die Struktur zulassen. Mit diesen Kennzahlen ist es möglich, Veränderungen im Weichgewebe analysieren. Das Ziel der Arbeit war es deshalb, die Eignung und mögliche Anwendungen der Magnetresonanzto-mographie (MRT) zur Analyse der Implantat-Gewebe-Wechselwirkungen zu erörtern. Für die Untersu-chungen wurde ein NMR-Spektrometer inklusive Imaging-Zubehör verwendet. Die Dissertationsarbeit beinhaltete sowohl die Untersuchung verschiedener Materialsysteme hinsichtlich ihrer Eignung für die MRT und deren Biokompatibilität, als auch die Analyse der knöchernen Einheilung ausgewählter Biomaterialien. Diese umfasste Aussagen zur Darstellbarkeit und Abgrenzbarkeit von Strukturen und beinhaltete auch quantitativ gewonnene Messparameter. Die Ergebnisse wurden stets im Vergleich mit der Histologie diskutiert. In der Arbeit konnte dargestellt werden, dass die Überprüfung der Eignung des zu untersuchenden Materials für die MRT vor der Analytik erfolgen muss. Es wurde demonstriert, dass Metalle erheblich mit dem MR-System wechselwirken können, was in der Konsequenz zu drastischen Störungen der Bildqualität führt. Diese Effekte waren stark von den ausgewählten Messparametern abhängig. Als ein MRT-geeignetes Verbundmaterial wurde Titan-beschichtetes Polyetheretherketon (PEEK/Ti) vorgeschlagen. Die Beschichtung mit Titan führte zu einer signifikant verbesserten Biokompatibilität des Kunststoffes. Die erfolgreiche Analyse der knöchernen Einheilung mit der Magnetresonanztomographie wurde im Rahmen von zwei tierexperimentellen Studien an verschiedenen Biomaterialien gezeigt (die Analyse erfolg-te ex vivo). Die Untersuchung der knöchernen Integration eines Zahnimplantates aus PEEK/Ti hatte das Ziel, die Darstellbarkeit des Implantates und knöcherner Strukturen mit der Magnetresonanztomographie zu evaluieren. Außerdem wurde ebenfalls gezeigt, dass es anhand der MRT-Schnittbilder möglich ist, quantitative Messgrößen zur Beschreibung des Einheilprozesses zu gewinnen. Aufgrund der geringen Versuchstierzahl wurde jedoch eine breite Streuung der Messdaten festgestellt. Allerdings besitzt die Studie durch die Untersuchung eines Zahnimplantates aus Polyetheretherketon/Titan mit der MRT nicht nur Neuheitswert in der Biomaterialforschung, sondern schlägt gleichzeitig eine Brücke zur klinischen, dentalen Implantologie. Die Bewertung der Darstellbarkeit knöcherner Strukturen und der verwendeten (teils tissue-engineerten) Knochenersatzmaterialien mit MRT und Histologie und des klinischen Erfolges derselben bildeten einen Schwerpunkt der zweiten tierexperimentellen Studie (die Analyse erfolgte ex vivo). Es war möglich, mit beiden bildgebenden Verfahren zu zeigen, dass sich die verwendeten Knochenersatzmaterialien nicht für die vorgesehene Anwendung eigneten. Die Beurteilung der Übereinstimmung der quantitativ gewonnenen Parameter beider Analysenmethoden bildete den Abschluss der Arbeit. Es wurde festgestellt, dass zwischen den Messdaten stets ein syste-matischer Unterschied bestand. Nachweislich war dieser aber weniger das Resultat der ungleichen lateralen Auflösungen oder der unterschiedlichen Darstellbarkeit von Gewebestrukturen der beiden Verfahren, sondern konnte auf den Einfluss der Analyse verschiedener Schichtebenen und individueller Unterschiede bei der digitalen Quantifizierung der auswertenden Personen zurückgeführt werden. / Currently, histological techniques are used to analyse implant-tissue-interactions. However, these methods are destructive and do not allow for the investigation of living animals. Therefore, it is not possible to study the integration of biomaterials repeatedly with one animal, resulting in a large number of animals and an increase of biological variability. Non-invasive imaging techniques have gained interest in the field of biomaterials. Whereas Computed Tomography (CT) was often used to evaluate the osseous integration, the assessment using Magnetic Resonance Imaging (MRI) has not been established, yet. MRI is a non-invasive medical imaging method that detects soft tissue. In contrast to CT the method does not require individuals to be exposed to radiation. The most important benefit of MRI is the possibility to acquire different soft tissue contrasts in situ because the various tissues have different signal intensities on MR images that can be altered by using different experimental parameters. Furthermore, it is possible to gain MR-specific properties that allow conclusions to the tissue structure. Thus, the objective of the doctoral thesis has been to investigate the suitability of MRI for the use in biometerial research and to show potential areas of application. The examinations were performed using a laboratory NMR-spectrometer inclusive imaging accessory. The thesis included an evaluation of the MR compatibility of different materials and their biocompati-bility and an analysis of the ingrowth of chosen biomaterials into bone. For that, the detection and identification of tissue structures and biomaterials was investigated with both, MRI and histology. Additionally, quantitative parameters were acquired and their comparability was assessed. It was clearly demonstrated, that metals interacted with the MR system and provoked large image distortions. These effects were strongly dependent on experimental parameters chosen. Polyetheretherketone with titanium coating (PEEK/Ti) was investigated and has been found to be MR safe. Above all, it was demonstrated that the biocompatibility of the polymer was significantly enhanced by coating with titanium. Within two animal studies the successful analysis of the osseous healing of different biomaterials with MRI was presented. To demonstrate the visibility of bony structures and biomaterials a dental implant made of PEEK/Ti was analysed. The ability to measure quantitative data in analogy to histomorphometry was shown, ditto. A large variation of the values was detected due to the limited number of animals used for the pilot study. Evaluating the displayability of bone and (to some extent tissue engineered) bone substitutes and assessing the clinical success of these materials was one main focus of the second animal study. Both, MRI and histological analysis could undeniably illustrate that all of the bone substitutes were not suitable for the chosen application. The thesis was completed with the determination of the agreement of quantitative values from both analysing methods. It was concluded that all values gained from the animal study were significantly different. It was proven that the chosen slice position and the image interpretation with two evaluators had a larger share to disagreement than the different lateral resolution of MRI and histological images or the diverging displayability of bone and bone substitutes. By investigating a MR suitable dental PEEK implant the doctoral thesis fulfils the criteria of novelty in biomaterial research. Moreover, it forges links between preclinical research and dental implantology.

Les assemblages multicouches polymère-métal, combinant la faible densité du polymère à la résistance du métal, se présentent comme une solution à fort potentiel pour répondre aux problématiques d’allégement de structure dans le secteur des transports. Plus particulièrement, ces travaux s’intéressent à l’élaboration de multicouches basés sur l’utilisation de polymères thermoplastiques thermostables associés à un alliage d’aluminium via un procédé de la métallurgie des poudres appelé « Spark Plasma Sintering » (SPS). Dans un premier temps, la mise en forme par SPS du polymère seul a été étudiée. Les influences des paramètres SPS tels que la température, la pression appliquée et le temps de maintien sur les caractéristiques structurales et les propriétés mécaniques du polyétheréthercétone (PEEK) ont été déterminées au moyen d’un plan d’expérience. Cette étude a permis de proposer des mécanismes de frittage et de mettre en évidence le rôle complexe joué par la pression sur la structure cristalline. Ensuite, le développement des assemblages, sans colle, d’un polyimide ou PEEK associé avec l’aluminium a été considéré. Une approche expérimentale a été mise en place, dans le but d’améliorer l’adhésion entre les deux matériaux. Des traitements de surface appliqués à l’aluminium visant à augmenter l’ancrage mécanique et la compatibilité chimique ont été testés. Le renforcement du polymère afin de limiter sa dilatation thermique a également été abordé. Les contributions de chacun des facteurs sont discutées sur la base de mesures d’adhérence et de caractérisations microstructurales. Cette stratégie a permis d’obtenir des multicouches avec une forte résistance à l’interface. / Polymer/metal multilayer assemblies, combining the low density of the polymer with the strength of the metal, are considered to be of great interest for high-demand engineering applications, especially in the transportation industries where the lightweighting issues are predominant. Keeping this in mind, the present study deals with the development of this kind of assembly, using thermostable thermoplastic polymers associated with an aluminum alloy by means of a powder metallurgy process: the “Spark Plasma Sintering” (SPS) technology. As the first part of this work, the sintering of the polymer was considered. The effects of SPS parameters such as temperature, pressure, and dwell time on mechanical properties of a PolyEtherEtherKetone (PEEK) were investigated thanks to a design of experiment. This study allowed to determine the mechanisms of polymer’s consolidation and the intricate role of pressure on the PEEK crystallinity was examined with particular attention. Then, the development of the assembly, without adhesive part, composed of both polymer (polyimide or PEEK) and aluminum alloy was considered. An approach was set up to improve the compliance between these dissimilar materials comprising: surface treatments on aluminum in order to enhance their mechanical anchoring and their chemical compatibility, as well as polymer reinforcement with the aim of reducing its thermal expansion. The efficiency of each solution is discussed based on microstructural and mechanical characterizations. This approach enabled to process multilayer assemblies with a significant strength at the interface.

Hydrogen and oxygen or air polymer electrolyte membrane fuel cell is one of the most promising electrical energy conversion devices for a sustainable future due to its high efficiency and zero emission. Membrane electrode assembly (MEA), in which electrochemical reactions occur, is stated to be the heart of the fuel cell. The aim of this study was to develop methods for preparation of MEA with alternative polymer electrolyte membranes and compare their performances with the conventional Nafion&reg / membrane. The alternative membranes were sulphonated polyether-etherketone (SPEEK), composite, blend with sulphonated polyethersulphone (SPES), and polybenzimidazole (PBI). Several powder type MEA preparation techniques were employed by using Nafion&reg / membrane. These were GDL Spraying, Membrane Spraying, and Decal methods. GDL Spraying and Decal were determined as the most efficient and proper MEA preparation methods. These methods were tried to improve further by changing catalyst loading, introducing pore forming agents, and treating membrane and GDL. The highest performance, which was 0.53 W/cm2, for Nafion&reg / membrane was obtained at 70 0C cell temperature. In comparison, it was about 0.68 W/cm2 for a commercial MEA at the same temperature. MEA prepared with SPEEK membrane resulted in lower performance. Moreover, it was found that SPEEK membrane was not suitable for high temperature operation. It was stable up to 80 0C under the cell operating conditions. However, with the blend of 10 wt% SPES to SPEEK, the operating temperature was raised up to 90 0C without any membrane deformation. The highest power outputs were 0.29 W/cm2 (at 70 0C) and 0.27 W/cm2 (at 80 0C) for SPEEK and SPEEK-PES blend membrane based MEAs. The highest temperature, which was 150 0C, was attained with PBI based MEA during fuel cell tests.