Nous avons développé une décharge transportée fonctionnant à la pression atmosphérique. Le générateur fonctionne en mode alternative avec une fréquence d’excitation variant entre 1 et 10kHz. Grace à une forme d'onde en dents de scie, il a été possible de transporter la décharge à l’intérieur d’un tube sur une longueur qui pourrait atteindre 200cm. L’influence des différents paramètres tels que la forme de la tension appliquée, le diamètre du tube et la configuration d’électrode, sur la formation de la décharge a été étudié. La nature des espèces excitées à l’intérieur et extérieur du tube a été identifié par Spectroscopie Optique d’Emission. La propagation de la décharge dans un système multi jets et un jet unique de la même section a été comparée. L’influence de ces deux types de jets transportés exposés aux bactéries de type E. coli a été étudiée et les résultats montrent que la zone d’inactivation des bactéries augmente significativement.De plus le potentiel de cette décharge pour le traitement de surface et dépôt des couches minces de polymère a été investigué aussi bien à l’extérieur qu’à l’intérieur du tube capillaire pour la première fois. Nous avons employé deux types de précurseurs: le TEOS, et le DEGME. Sous certaines conditions, les couches de type PEG présentant des propriétés antiadhésives des cellules ont été déposées sur le PS. Afin d’étudier les modifications de surface créées sur les polymères par cette décharge. Les résultats obtenus par des méthodes d’analyse différentes montrent qu’à part l’oxydation de la surface du UHMWPE nous pouvons déceler une insaturation de la surface qui est souvent accompagnée de la réticulation de la surface. / We have developed a transporting discharge source that can operate at atmospheric pressure. The device is working by using AC power supply with a frequency ranging between 1 to 10 kHz. The sawtooth waveform enabled the transport of discharge as long as 200 cm. The different parameters that affect the plasma delivery such as voltage of the waveforms, tube diameter and electrode configuration were investigated. The electronically excited and active species inside and outside of the plasma channel were characterized by Optical Emission Spectroscopy. The electrical and temporal characteristics of the plasma, discharge power and charges on the sample were investigated. The propagation of transporting discharge with multi-jets and a single jet with the same cross-sectional area has been compared. Also, E.coli bacteria were exposed to the transporting discharge multijets and single jet for different time durations.The potential of the transported discharge for the surface treatment of polymers and deposition of thin films has been investigated. Two different precursors namely TEOS, and DEGME have been employed for the elaboration of thin organic coatings by introducing the precursors inside and at the exit of the capillary tube. The PEG like coatings obtained in the case of DEGME on PolyStyrene films showed for particular operating conditions nonadhesive coatings with respect to Ovary Carcinoma Celles. In order to study the surface modification effects of the discharge, the Ultra High Molecular Weight PolyEthylene was used as the substrate in the two different configurations. The results show that besides the oxydation of the UHMWPE, crosslinking takes place.

Predložená dizertačná práca sa zaoberá analýzou opotrebenia totálnych bedrových endoprotéz za použitia optických metód. V práci bol predstavený nový prístup hodnotenia objemového úbytku materiálu pomocou 3D optického skeneru. Tento nový prístup je časovo efektívny, poskytuje veľké množstvo snímaných bodov na povrchu implantátu. Množstvo bodov umožňuje presnejšiu rekonštrukciu pôvodnej geometrie a prípadné rekonštrukcie nežiaducich poškodení polyetylénovej vložky pri extrakcii. Predstavené metóda bola validovaná za pomoci štandardizovanej gravimetrickej metódy v súlade s ISO 14242. Následne bol optická skenovacia metóda použitá v troch štúdiách zameraných na analýzu opotrebenia, mechanické zmeny artikulujúceho povrchu a mikroštruktúrne zmeny v dôsledku zlyhania implantátu. Analýza 23 extrahovaných polyetylénových vložiek typ Bicon - plus s rozšíreným použitím v Českej republike poukázala na niektoré problémy spojené so zlyhaním implantátu. Adhezívno - abrazívne opotrebenie bolo identifikované v oblasti penetrácie femurálnej hlavice a následné poškodenia ako delaminácia materiálu , plastické deformácie a pitting boli pozorované v okolí tejto oblasti. Analýza materiálových vlastností poukázala na degradáciu mechanických a chemických vlastností, čo bolo prevažne závislé od rozsahu opotrebenia implantátu. U implantátov boli pozorované výrazné plastické deformácie , nárast oxidačného indexu a nižší pomer tvrdosti voči modulu elasticity, v porovnaní s novými vzorkami. Tečenie materiálu a plastické deformácie, ktoré vykazovali všetky extrahované vzorky boli analyzované v závere predloženej dizertačnej práce, na základe testov na nových implantátoch v zábehovom cykle. Cieľom práce je uviesť nový prístup analýzy opotrebenia polyetylénových vložiek za pomoci optických skenovacích metód a preukázať jeho použiteľnosť na analýze súboru extrahovaných implantátov. Výsledky získané pomocou tejto metódy sa ukázali ako vhodné a môžu viesť k lepšiemu pochopeniu procesov opotrebenia a zlyhávania implantátov.

Made available in DSpace on 2017-07-21T20:42:32Z (GMT). No. of bitstreams: 1 Melina Correa Gabriel.pdf: 5915390 bytes, checksum: bae67fca28fd7999823fa6ec6ac98844 (MD5) Previous issue date: 2010-03-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The intention of this exploratory research is to study the modifications provided by high-energy mechanical milling in ultra-high molecular weight polyethylene (UHMWPE) and mixtures of this polymer with polyethylene glycol (PEG). These modifications can be of interest for future processing of UHMWPE. The mechanical milling was performed in an attritor mill, a type of mill that can be used in laboratory as well as in industry. The millings of UHMWPE were performed in different rotation speeds. For mixtures of UHMWPE and PEG, the amounts of PEG were also different. The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The mechanical milling modified the UHMWPE particles morphology: with milling, the almost rounded shape became flat-like shape. This caused the reduction of apparent density of polymer after milling. The mechanical milling also provided structural changes. With the increasing of the rotation speed,there was the increasing of the monoclinic phase and the decreasing of the orthorhombic, up to 500 rpm. For 600 rpm, the amount of monoclinic phase decreased. In this rotation, the deformation rate probably increased the process temperature, allowing the monoclinic phase to return to its initial structural orthorhombic form. In mixtures of UHMWPE and PEG, after mechanical milling, the particles of PEG were probably reduced and better dispersed in the UHMWPE matrix. Changes in thermal characteristics of polymers also could be noted. The kinetics of UHMWPE crystal growth changed, as well as the behavior of PEG crystallization. Feasibly, dispersed particles of PEG acted as physical barriers against the crystalline phase growth of UHMWPE and the crystallization temperature of PEG decreased, when the UHMWPE and PEG mixtures were milled. / Este trabalho exploratório teve por objetivo estudar as modificações promovidas por moagem de alta energia no de polietileno de ultra-alta massa molar (PEUAMM) e sua mistura com polietileno glicol (PEG), que podem ser de interesse para auxiliar um posterior processamento do PEUAMM. As moagens foram realizadas em um moinho do tipo attritor, um tipo de moinho que pode ser usado tanto em laboratório quanto em escala industrial. Foram variadas as velocidades de rotação na moagem do PEUAMM, além das concentrações de PEG, quando feita a mistura. As amostras foram caracterizadas por microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), calorimetria exploratória diferencial (DSC) e difração de raios X. A moagem de alta energia do material modificou a forma das partículas de PEUAMM, passando de arredondadas a flakes, com a evolução do processo de moagem, fazendo com que a densidade aparente do polímero diminuísse muito comparado ao polímero não moído. A moagem também proporcionou mudança estrutural, permitindo a formação de fase monoclínica em detrimento da ortorrômbica. A medida que se aumentou a rotação do moinho até 500 rpm, houve um crescimento da fase monoclínica. Apenas para 600 rpm, a quantidade dessa fase sofreu decréscimo, devido possivelmente ao aumento da frequência de choques e da temperatura de processamento, fazendo com que a estrutura monoclínica retornasse à estrutura ortorrômbica original. Na mistura de PEUAMM com PEG, a moagem provavelmente permitiu redução das partículas e a melhor dispersão de PEG na matriz de PEUAMM. Também se observaram mudanças nas características térmicas dos polímeros na mistura após moagem. Ocorreu mudança na cinética de crescimento dos cristais de PEUAMM e mudança no comportamento de cristalização do PEG, comportamento este que não ocorreu para o PEUAMM moído ou para a mistura de PEUAMM com PEG antes da moagem. Possivelmente, as partículas dispersas de PEG atuaram como barreiras ao crescimento da fase cristalina do PEUAMM e houve diminuição da temperatura de cristalização do PEG, na mistura com PEUAMM após moagem.

The increasing worldwide demand for more eco-friendly materials with improved tribo- logical properties has expanded the interest in research on polymer as an alternative for conventional metal/metal contacts under dry lubrication. Specifically, UHMWPE, a semi-crystalline polymer, has shown interesting tribological properties for low demanding applications, allied with excellent recyclability, manufacturability and low cost. Though, its limited working temperature range and wear resistance claims reinforcements to modulate these drawbacks. Metal sulfides, such as MoS2 and SnS2 are well-known 2D materials with outstanding thermal, mechanical and tribological properties which have the potential to increase the range of applicability of UHMWPE. Therefore, this work aims to investigate the influence of metal sulfide-based micro-particles on UHMWPE-based composites properties under reciprocating movement and to determine further acknowledgements about the mechanisms involved. The results showed that the incorporation of fillers im- proved in hardness and wettability, whereas thermal properties were conserved. Though, it is noted that chemical degradation processes (oxidation and un-saturation reactions) that occurred during the manufacturing negatively influenced the composite’s tribological response. Higher reinforcement weight percentages (10%) promoted metal-sulfides agglomeration, increased degradation and ultimately diminished wear resistance. Overall, optimizing the amount of filler in the matrix at 5 wt% provided its homogeneous dispersion and a good interface with the matrix, leading to enhancement in wear resistance up to 62%. Indeed, the incorporation of metal-sulfide based materials in the UHMWPE matrix revealed an excellent solution where wear resistance improvements are needed.

The increasing demand for more readily bio-degradable, renewable and non-toxic environmentally adaptive lubricants with a lower degree of bioaccumulation has escalated the investigation of water-based lubricants as the potential alternatives for conventional mineral-based oils. Water is an excellent environmentally adapted lubricant; however, it is a low viscous fluid and holds downsides of having corrosive nature and extremely low pressure-viscosity coefficient leading to insufficient load-carrying capacity. These shortcomings make pure water a poor choice for operations involving high load and low speed, for instance, within hydropower applications. Therefore, the choice of appropriate modifiers and additives is crucial to improve the viscosity, friction-reducing performance and anti-wear properties of water as a base lubricant. Appropriate selection and combination of bearing materials also significantly improve the tribological performance of the lubricants. In the presented work, tribological behavior of polyvinylpyrrolidone (PVP) and poly(sodium 4-styrenesulfonate) (PSS) thickening agents with water as a base fluid in the lubrication of pure UHMWPE and SCF reinforced UHMWPE bearing materials has been investigated individually under reciprocating tribometer. The results showed that both PVP and PSS are excellent viscosity modifiers. PVP exhibited excellent friction-reducing and anti-wear performance, while PSS revealed increased wear rates with an insignificant reduction of friction coefficients. This study aims to explore the potential for using newly developed water-based lubricants in the replacement of traditional mineral-based lubricants for hydropower turbine bearings.

The transition to a Circular Economy scheme that enables a more efficient usage of the resources is one of the most pressing needs in our society. From the industrial perspective this has been translated into new design philosophies and the search for more efficient systems. Polymeric composites have played a key role in the development of lighter components with good mechanical and tribological properties. Specifically, the demand of Carbon Fiber Reinforced Polymers (CFRP) has had an increasing trend since 1970s-1980s, becoming one of the kind of composites with the highest demand in the market to supply industries such as aerospace, automotive, construction, renewable energies, among others. With the increasing demand of CFRP materials some of the main challenges that arise are their disposal, environmental impact and cost of production to maintain the required supply. The use of Carbon Fibers as a reinforcement for polymeric matrices has been widely documented over the last decades, however the characterization of recycled Carbon Fibers for tribological applications is still scarce. Therefore, this investigation is focused on the mechanical and tribological characterization under water lubricated conditions of Ultra High Molecular Weight Polyethylene (UHMWPE) composites reinforced with virgin and recycled Carbon Fibers and Graphene Oxide. The findings of this work provide an important panorama regarding the performance of recycled Carbon Fibers, showing that they can have a comparable performance in mechanical properties and tribological behavior. This enables the use of recycled Carbon Fibers without compromising performance while reducing the environmental impact and cost.

Les maladies ostéoarticulaires représentent environ 10% de l'ensemble des pathologies identifiées en France chaque année. Pour l'instant aucun traitement permettant la réparation du tissu cartilagineux n'est vraiment disponible, hormis la pose d'un implant articulaire. Mais, malgré de nombreux efforts pour développer de nouveaux matériaux pour les implants articulaires leur durée de vie in vivo s'avère souvent très décevante par rapport aux extrapolations faites à partir de simulations ex-vivo. Les discordances entre les durées de vie in vivo et ex vivo sont principalement imputées aux conditions d'essais ex vivo insuffisamment réalistes vis-à-vis des propriétés physico-chimiques des lubrifiants biologiques. Dans ce contexte, ce travail vise à agir sur la réactivité physicochimique des surfaces frottantes des implants articulaires en UHMWPE afin de maîtriser l'accrochage des molécules lubrifiantes de type phospholipidique et ainsi d'augmenter leurs performances tribologiques. Les résultats montre que l'activation physichochimique des surfaces de UHMWPE par des couche de MPC peut diminuer l'usure des surfaces polymères d'implant mais cela nécessite un contrôle de la qualité de la couche MPC greffée (densité surfacique, épaisseur, accrochage chimique, adsorption physico-chimique) afin de garantir une bonne tenue mécanique et tribologique. D'autre part il a été montré que la présence de lubrifiant biologique (substitut du fluide synovial à base de liposomes) réduit l'usure des surfaces de UHWPE même si la couche de MPC est peu dense et peu épaisse

Im Rahmen der Arbeit wurde ein semi-analytisches Berechnungsmodell für den Reibwert einzelner kugelförmiger Erhebungen erarbeitet, das die Berechnung der deformativen (μ_def) und adhäsiven (μ_adh) Reibanteile ermöglicht. Die Integration eines plastischen (Radius der Laufspur R_Spur) und eines viskosen (Rückstellwinkel ω) Verformungsanteils gestattet die Berechnung der realen Kontaktfläche während des Reibvorgangs. In Abhängigkeit des mittleren Kontaktdrucks kann damit der adhäsive Reibanteil μ_adh bestimmt werden. Die experimentelle Untersuchungen umfassten neben ungeschmierten Reibversuchen, die zur Ermittlung des gesamten Reibwertes (μ_ges) dienten, auch mit Silikonöl geschmierte Versuche aus denen sich μ_def ergibt. Anhand der Verifikationsversuche konnte einerseits gezeigt werden, dass beide Schmierungszustände zu gleichen Verformungen führen und andererseits wurde der Nachweis erbracht, dass der im Berechnungsmodell postulierte Zusammenhang zwischen dem Rückstellwinkel ω und μ_def Gültigkeit besitzt. Hierzu wurden Reibversuche mit segmentierten Kugeln durchgeführt, die eine gezielte Variation des Rückstellwinkels ω erlauben. Für beide untersuchten Reibpaarungen (Stahl | PE-UHMW und POM-C | PE-UHMW) kann abgeleitet werden, dass der deformative Reibanteil μ_def generell von untergeordneter Rolle ist (ca. 1/3 μ_ges) und der Einfluss des adhäsiven Reibanteils μ_adh überwiegt (ca. 2/3 μ_ges). Dabei sinkt μ_adh und folglich auch μ_ges mit zunehmendem Kontaktdruck p_(max,Ebene). Dieser wurde als verallgemeinerte Bezugsgröße eingeführt und beschreibt den maximalen Hertz´schen Kontaktdruck eines äquivalenten Kugel-Ebene-Kontaktes, der sich unter Eingabe des Kugelradius r_Kugel, der Normalkraft und der Verwendung der statischen E-Moduln beider Werkstoffe ergibt. Weiterhin zeigten die Untersuchungen, dass die oszillierende Bewegungsform im Vergleich zur rotierenden Bewegung immer einen erhöhten Reibwert μ_ges auszeichnet. Abschließend wurden noch Reibexperimente zu Mehrfachstrukturen aus POM-C mit je 6 Einzelerhebungen im Kontakt durchgeführt. Auch hier lag eine hohe Übereinstimmung zwischen Experiment und Modell vor. Es konnte gezeigt werden, dass Reibwerte für beide Bewegungsformen auf μ_ges ~ 0,13 gesenkt werden können. Bezogen auf den jeweiligen höchsten Reibwert (μ_(ges,rotierend) ~ 0,24, μ_(ges,oszillierend) ~ 0,34), welcher mit glatten Probekörpern ermittelt wurde, stellt dies eine erhebliche Reduktion dar. / In this thesis, a semi-analytical calculation model for the coefficient of friction (COF) of single spherical protrusions which allows the calculation of the deformative (μ_def) and adhesive (μ_adh) friction parts was developed. The integration of a plastic (radius of the running track R_Spur) and a viscous (rear angle ω) component of deformation allows the calculation of the real area of contact during the friction process. Depending on the mean contact pressure, the adhesive friction part μ_adh can be determined. The experimental studies included unlubricated friction tests, which served to determine the total COF (μ_ges), as well as tests being lubricated with silicone oil, from which μ_def is obtained. Based on the verification tests, it could be shown that both states of lubrication result in the same deformation and that the relationship between the rear angle ω and μ_def postulated in the calculation model is valid. Therefore, friction tests were carried out with segmented spheres, which allow a specific variation of the rear angle ω. For both friction pairings investigated (steel | PE-UHMW and POM-C | PE-UHMW), it can be concluded that the deformative friction part μ_def is generally of minor significance (approx. 1/3 μ_ges) and the influence of the adhesive friction part μ_adh predominates (approx. 2/3 μ_ges). Thereby μ_adh and consequently also μ_ges decreases with increasing contact pressure p_(max,Ebene). The latter was introduced as a generalised reference value and describes the maximum Hertzian contact pressure of an equivalent sphere-plane contact, which is obtained by entering the radius of the sphere r_Kugel, the normal force and using the static E-moduli of both materials. Furthermore, the investigations revealed that the oscillating form of motion always has an increased COF μ_ges compared to the rotating motion. Finally, friction experiments on multiple structures made of POM-C were carried out, each with 6 individual protrusions in contact. Also here, there was good agreement between the experiment and the model. It could be demonstrated that COF for both forms of motion can be reduced to μ_ges ~ 0.13. In comparison to the highest COF (μ_(ges,rotating) ~ 0.24, μ_(ges,oscillating) ~ 0.34), which were obtained with flat specimens, this is a significant reduction.