Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-10-08T14:50:19Z No. of bitstreams: 1 TÂNIA LÚCIA LEAL - TESE (PPGEP) 2007.pdf: 1662597 bytes, checksum: 3b9ecad3c331d148a824d574cd4ac35c (MD5) / Made available in DSpace on 2018-10-08T14:50:19Z (GMT). No. of bitstreams: 1 TÂNIA LÚCIA LEAL - TESE (PPGEP) 2007.pdf: 1662597 bytes, checksum: 3b9ecad3c331d148a824d574cd4ac35c (MD5) Previous issue date: 2007-02-22 / CNPq / Membranas obtidas por sinterização de partículas de PEUAPM foram desenvolvidas visando sua aplicação no tratamento de efluentes. As membranas foram sinterizadas em diferentes tempos e temperaturas e o seu desempenho na remoção de partículas presentes em efluentes aquosos foi investigado. Utilizou-se o planejamento experimental fatorial e análise de superfície de resposta para avaliar os efeitos do tempo e temperatura de sinterização no desempenho das membranas. Este estudo foi conduzido com as amostras que apresentaram menor tamanho de partículas, isto é, passantes em peneira de malha 200. Os resultados evidenciam que quanto maiores os tempos e temperaturas de sinterização, menores os fluxos do permeado através das membranas e que os efeitos da temperatura foram mais acentuados do que os do tempo de sinterização. A compactação das membranas após a sinterização provocou reduções no fluxo e na porosidade, enquanto o tamanho médio dos poros permaneceu inalterado. Dois procedimentos foram utilizados para modificar a superfície interna das membranas: a) deposição de um filme de PEAD e b) modificação por plasma de metano. Estas modificações foram realizadas nas membranas manufaturadas com pó de PEUAPM como recebidos do fabricante e com os passantes em peneira de malha 200. Ambas as modificações de superfície levaram a reduções no tamanho de poros na superfície das membranas. O tratamento por plasma minimizou o fenômeno de “fouling”, enquanto que maior eficiência na remoção de partículas sólidas em suspensão na água foi obtida com membranas recobertas internamente com filme de PEAD. Melhor desempenho global foi obtido para as membranas manufaturadas com PEUAPM de código 3041 passante em peneira de malha 200, superficialmente modificadas ou não. Este estudo indica que o PEUAPM pode ser usado na produção de membranas de microfiltração de baixo custo para remoção de partículas sólidas presentes em efluentes aquosos. / Membranes obtained by sintering of UHMWPE powders were manufactured aiming at their use in effluent treatment. The membranes were sintered at different times and temperatures and their performance in aqueous effluent particle removal were investigated. An factorial experimental planning and response surface analysis was employed to evaluate the effects of sintering time and temperature in the performance of the membranes. This study was conducted on samples having the smallest particles size, i.e., with powders that passed through a 200 mesh sieve. Higher sintering times and temperatures led to smaller permeate flow through membranes and temperature effects were more significant than those of time. Membranes compaction after sintering leads to lower permeate flows and porosities, although the average pore sizes do not change. Two routes were used to modify the internal surface of the membranes: a) HDPE film deposition and b) methane plasma modification.These modifications were made with membranes prepared with UHMWPE powder as received from supplier and passed through a 200 mesh sieve. Both treatments caused reductions on the membranes superficial pore sizes. Plasma treatment minimized the “fouling” phenomenon, while the best efficiency in solid particle removal from water dispersions was found for the membrane internally coated with a HDPE film. Best overall performances were displayed by the membranes prepared with UHMWPE grade 3041 sieved though a 200 mesh sieve. The results indicate that the UHMWPE can be used to prepare low cost micro-filtration membranes to remove solid particles present in aqueous effluents.

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During normal walking, the relative motion of the human knee involves flexion/extension, anterior/posterior sliding, and medial/lateral rotation. As well, the knee experiences a complex, dynamic loading curve with a peak of up to seven times body weight. However, most wear testing machines that have been used to evaluate total knee replacement materials are unidirectional and/or apply only static force. This thesis presents an alternate wear testing device capable of simulating the most prevalent motions of the knee, and applying physiologically-correct loading to the material interface. By incorporating a CoCr disc, an UHMWPE block, stepping motors, pneumatic components, computer control, and linear tables in an x-y configuration, the device is capable of quickly screening new and alternative materials to UHMWPE before evaluating them on a much more expensive knee simulator. In addition, flexibility of the device allows programming of many different motion and loading configurations permitting materials testing under only certain circumstances, or evaluating the effects on wear of specific motions. Design rationale, development, validation, and future recommendations are presented. / Master of Science

[pt] Ameaças contra a vida, principalmente por disparos de armas de fogo, impulsionam a pesquisa de novos materiais para fabricação de soluções para proteção balística individual. Os compósitos poliméricos reforçados por fibras de polietileno de ultra alto peso molecular revolucionaram esse campo nos últimos 15 anos e têm sido extensivamente estudados, principalmente por suas excepcionais propriedades mecânicas e baixa densidade, visando desenvolver materiais com alta capacidade específica de absorção de energia. Em desacordo, a produção desses compósitos é dominada por poucas empresas no mundo, e sua disponibilidade relativamente limitada, além do fato das placas balísticas serem materiais controlados e de domínio de fabricação restrito, o que dificultou a obtenção de informações. Neste sentido, a presente pesquisa buscou projetar, fabricar e caracterizar seis modelos de placas balísticas para proteção contra disparo de munição de fuzil, utilizando diferentes tipos de compósitos (préimpregnados) com a adição de camada da liga de titânio. A caracterização contou com ensaios de FTIR do CBPF, TGA e DSC da PUC-Rio, ensaio de tração (EMT) das fibras, de dureza, MEV e metalografia no CTEx. A análise do desempenho das placas foi realizada no CAEx e contou com câmera de ultra alta velocidade, equipamentos para ensaios balísticos e equipamento de varredura 3D a laser. Os resultados dos ensaios foram mensurados pela velocidade dos disparos e pela profundidade da deformação da face posterior de 16 placas. Foi possível concluir que a fabricação de protótipos mantendo os valores de espessura ou densidade de área da solução semelhante a de placas controle somente em pré-impregnado foi eficiente. O emprego da chapa da liga de Ti-6Al-4V com espessura de apenas 1mm se deu em substituição de até 30 por cento do material pré-impregnado. Na situação limite, foi possível obter placas que resistiram aos impactos de munição de fuzil com cerca de 95 por cento da velocidade especificada na norma, dentro da tolerância de deformação posterior. / [en] Life threats, mainly from firearms, incentive research into new materials for manufacturing personal ballistic protection. Polymer composites reinforced with ultra high molecular weight polyethylene fiber have revolutionized this field over the last 15 years and have been extensively studied, especially for their exceptional mechanical properties and low density, to develop materials with high specific energy absorption capacity. In disagreement, the production of these composites is dominated by few companies in the world, and their availability is relatively limited, besides the fact that ballistic plates are controlled materials and restricted manufacturing domain, which made it difficult to obtain information. In this sense, the present research aims to design, manufacture and characterize six models of ballistic plates for protection against firing of rifle ammunition, using different types of composites (prepregs) with the addition of a titanium alloy layer. The characterization included FTIR at CBPF, TGA and DSC tests at PUC-Rio, fiber tensile strength, SEM, and metallography at CTEx. The plate performance analysis was performed at CAEx and included an ultra high speed camera, ballistic testing equipment and 3D laser scanning equipment. Test results were measured by firing speed and depth of the back face deformation of 16 plates. It was possible to conclude that the prototyping keeping the thickness or areal density values of the solution similar to control plates only in prepreg was efficient. The use of Ti-6Al-4V alloy plate with thickness of only 1mm by replacing up to 30 percent of prepreg material. In the border situation, it was possible to obtain plates that withstood the impact of rifle ammunition at about 95 percent of the speed specified in the standard, within the back face deformation tolerance.

Le polyéthylène à ultra haute masse molaire (UHMWPE) présente une viscosité si forte à l’état fondu que seuls des procédés de mise en forme de type frittage peuvent être employé. Ce procédé rarement utilisé pour les polymères reste peu étudié. En particulier les deux principaux mécanismes généralement mentionnés que sont le réenchevêtrement et la cocristallisation aux interfaces sont difficilement observables séparément. Le UHMWPE, grâce à sa très haute viscosité à l’état fondu et grâce à son plateau caoutchoutique extrêmement étendue en température, peut faire l’objet d’essais mécaniques à la fois à l’état semi-cristallin et à l’état fondu. Des poudres natives de UHMWPE de masses molaires comprises entre 0,6 et 10,5 Mg.mol-1 sont utilisées comme matériau de départ pour leur mise en oeuvre par frittage. La consolidation des interfaces par soudage des particules a été effectuée sous pression à différentes températures supérieures au point de fusion et pour différentes durées. Des expériences de traction effectuées soit à température ambiante soit au-dessus du point de fusion ont permis de distinguer le rôle de l'interdiffusion des chaînes au travers des interfaces de celle de la cocristallisation dans les mécanismes de soudage de particules. Il s'est avéré qu’un soudage efficace se produit dans une échelle de temps très courte. La très faible influence de la durée de frittage par rapport à celle de la température de frittage a prouvé que l'interdiffusion des chaînes n'est pas régie par un mécanisme de reptation. L'explosion à la fusion des cristaux « hors-équilibre » de la poudre native est suggérée être le mécanisme principal permettant un réenchevêtrement dans un laps de temps beaucoup plus court que celui de la reptation. La cocristallisation est un phénomène si efficace dans la consolidation de l'interface à l'état solide qu'elle masque significativement la cinétique de réenchevêtrement gouverné par la température, visible dans les tests mécaniques à l’état fondu. / One of the main issues of ultra-high-molecular-weight polyethylene (UHMWPE) is to overcome its very high viscosity. Powder sintering is then often required instead of injection or extrusion. However, sintering mechanisms remain partially understood. Indeed, the two main mechanisms generally mentioned for interparticle welding, i.e. re-entanglement and cocrystallization, can hardly be observed separately. Fortunately, due to its very high molecular weight, UHMWPE exhibits an exceptionally broad rubbery plateau so that mechanical tensile tests can be easily performed both below and above the melting point. Four UHMWPE of molecular weight in the range of 0.6.106 g.mol-1 to 10.5.106 g.mol-1 have been processed by means of sintering of nascent powders. The interface consolidation or particle welding was carried out under pressure at various temperatures above the melting point and for various durations. Tensile drawing experiments performed either at room temperature or above the melting point enabled to discriminate the role of chain interdiffusion through the particle interface from that of cocrystallization in the mechanism of particle welding. It turned out that an efficient welding occurred within a very short time scale. The very weak influence of sintering time compared to that of sintering temperature gave evidence that chain interdiffusion was not governed by a reptation mechanism. The entropy-driven melting explosion of the “non-equilibrium” crystals in the nascent powder is suggested to be the main mechanism of the fast chain reentanglement and subsequent particle welding within a time scale much shorter than the reptation time. Cocrystallization is so much efficient in the interface consolidation in the solid state that it significantly hides the temperature-governed kinetics.

Two different catalysts (bis[N-(3-tert-butylsalicylidene)-pentafluoroanilinato] titanium (IV) dichloride and [1-(8-quinolyl)indenyl] chromium (III) dichloride catalysts) activated with aluminoxane based co-catalysts (MAO, PMAO, MMAO12 and MMAO3A) have been evaluated in the polymerisation of ethylene leading to UHMWPE having a reduced number of entanglements between the chains. The effect of a co-catalyst modifier (BHT) on the catalytic systems and the resulting polymers is also addressed. Both catalysts are capable to promote the synthesis of UHMWPE having a reduced amount of entanglements in the conditions used. Uniaxial solid-state deformation of UHMWPE samples of different molar masses have been evaluated and related with the entanglement state of the polymers synthesised. A clear relationship between some mechanical properties and the molar mass/entanglement density of the polymers synthesised has been found.

In this thesis Graphit-iC™, an amorphous carbon coating developed by Teer Coatings Ltd. was modified and deposited onto CoCr and WHMWPE substrates in order to improve the wear properties. It was identified that depositing a hard coating onto soft substrate would cause high stresses and lead to coating delamination. Consequently the polyethylene substrates were ion implanted with nitrogen to reduce the hardness differential at the substrate-coating boundary. The coating was characterised using a pin on disc method in order to determine wear and friction. Hardness and fatigue was characterised using nano-indentation and the coating adhesion was measured using scratch testing. Application of the coatings resulted in a significant reduction in wear. Wear factors as low as 3.65x10¯18m³/Nm were achieved for coated CoCr substrates compared to 3.53x10¯15m³/Nm reported in the literature for uncoated CoCr. The coating resulted in friction coefficients between 0.12 and 0.19 with hardness ranging from 6.65 and 15.63GPa. Similarly coating UHMWPE resulted in a reduction in the wear factor to less than 9.6x10¯17m³/Nm. It was concluded that the deposition of amorphous carbon coatings can improve wear of hip joint prostheses, although consideration must be made for the adhesion of the coating to the substrate so that it does not contribute to an early failure of the device. Improved adhesion can be achieved by reducing the hardness differential between the coating and adhesion, either through softening the coating or by using interlayers.

More and more, advanced polymer and composite materials are being applied in engineering situations where a high resistance to loading at high rates of strain, such as by impact or blast deformation, are a vital requirement. Specific examples exist in the fields of defence and sport research and development for personal, and in the case of the former, vehicular, protection. There are obvious advantages to the use of polymer materials for these applications in augmenting the more widely used metals and ceramics, most notably the evident reduction in weight, and it is believed that with suitable nano-reinforcement these materials may exhibit improved combat survivability. The current study concerns the effect that nano-reinforcements in the form of Carbon Black, Titanium Dioxide, Exfoliated Hectorite Nanoclay and Carbon Nanotubes; have upon the high strain rate mechanical properties of structural variants of Polyethylene (Linear Low Density Polyethylene, LLDPE; High Density Polyethylene, HDPE; Ultra-High Molecular Weight Polyethylene, UHMWPE) and blends of UHMWPE and HDPE. The testing samples were manufactured using a novel process developed in the Loughborough University Materials Department, which has produced well-dispersed specimens. The formed nanocomposite samples were studied using an in-house four-bar Split Hopkinson Pressure Bar (SHPB) system for high strain rate performance, instrumented dropweight for intermediate strain rates and a conventional commercial Hounsfield H50KM universal testing machine for quasi-static strain rate compressive tests. The experimental results recorded for un-reinforced materials are used as a reference to allow comparative analysis of any effect the nano-reinforcements or the blending process have upon the structure, performance and properties of the composite material. From the mechanical testing, it was seen that the stress-strain behaviour of Polyethylene is highly strain-rate-dependent, as plots of the average representative yield stress as a function of strain rate show a bilinear relationship when plotted on a logarithmic strain rate scale, with the gradient of the curve rising sharply at around 103s-1. Concerning the addition of the nanofiller materials, it was seen that there was an increase in the flow and yield stresses and the energy absorption characteristics of the resulting composite with the magnitude dependent upon whether it was a pure or blended polymer that was reinforced. Of the aforementioned fillers it was seen that the addition of Carbon Nanotubes in the small concentrations studied resulted in the greatest increase in properties compared to the pure polymers, closely followed by the Carbon Black fillers. Also of note, the un-reinforced blended samples showed significant increases in flow stress, yield stress and energy absorption when compared to the constituent UHMWPE and HDPE polymers. Additionally, a complete set of Differential Scanning Calorimetry and density measurements were made before testing to assess any changes in the properties after reinforcement or blending, and to help in the interpretation of the results from the different mechanical tests.

Inom området skyddskläder för utövande av vattenblästring ställs mycket höga krav på säkerhet, de textila material och tillverkningstekniker som används idag ger stela produkter med negativ hälso- och miljöpåverkan vid produktion och är en tidskrävande tillverkningsprocess. Ämnesområdet med en vara av nonwoven som skyddande komponent i skyddskläder vilken sammanfogas med hjälp av en smältfiber har undersökts tidigare i en kort förberedande studie vilket lagt grund för detta examensarbete. Uppdraget om en alternativ tillverkningsmetod till skyddande komponent till en skyddsdräkt för vattenblästring kommer från företaget TST Sweden AB i Kinna. En nonwovenprodukt kan ge ett mjukt och mer följsamt resultat på varan och är relativt kostnadseffektiv att tillverka. De fibertyper som är intressanta för denna kombination är UHMWPE-fiber och bikomponentsfiber. UHMWPE-fibern har tidigare visat klara kraven på säkerhet och bikomponentsfibern fungerar som smältfiber för att skapa bindepunkter i nonwovenvaran. Denna studie undersöker och jämför ett material som tas fram i studien med syfte att klara samma skyddande egenskaper som ett referensmaterial av den produkt som används idag. Målet är att ersätta den kemiska doppningen med en termisk sammanfogning. Studien är både teoretisk och praktisk och går igenom hela processen från kardning till termiska bindesätt och slutligen även för materialegenskapstester genom bland annat dragprovning och penetrationstester. Två olika bikomponenter jämfördes i denna studie, på grund av bristande mottagningskontroll på den beställda bikompPE-fibern tillverkades material utifrån fel specifikationer, vid upptäckt av detta adderades anpassade tillverkningsmetoder. Resultatet från denna studie tyder på att en komponent till skyddsdräkt för vattenblästring tillverkad av UHMWPE/bikomp – nonwoven har kommit framåt i utvecklingen men ännu inte är färdigutvecklad. Studien visar att provserien av nonwoven som bestod av 70% UHMWPE och 30% coPES/PES vilken behandlades termiskt i mikrovågsugn visade bäst resultat i energiabsorption, men vilket inte nådde upp till samma nivå som referensmaterialet. Med avseende på materialets styvhet nåddes klara förbättringar då alla provserier uppvisade mjukare resultat än referensmaterialet. Hållbarhetsmässigt ses fördelar med nonwoven-konstruktion av lågsmältande bikomponentsfiber jämfört med kemiskt doppad nonwoven.