Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

This work consists of an investigation into the microstructure and mechanical behaviour of glass fibre reinforced polyester resin beams. The volume fraction occupied by glass fibres was 20-30%, which is that typically used in boat building. The beams tested were all unidirectional, with fibres oriented parallel or perpendicular to the long axis of the beam. Various techniques have been developed which may be applicable to other composite materials. The microstructure of the beams was investigated by observation of cross-sections using a Quantimet 720 Image Analysing Computer. Volume fractions and the distribution. of fibre cross-sectional areas were measured. Methods have been developed for the quantitative definition of the microstructure, in terms of the fibre arrangement. Cracks were grown in four-point flexural loading while monitoring acoustic emission. The acoustic emission circuit was built in the laboratory, and designed to monitor fibre failures only, one count being associated with one fibre failure. The processes of crack growth were further investigated by observation of fracture surfaces using a scanning electron microscope and measurement of crack profiles. The factors controlling the processes of crack growth have been elucidated. The material condition was monitored by specific damping capacity measurements. A free-free rig with excitation at the ends of the beam was developed. In addition measurements were made using a cantilever rig. Simple analyses involving the solution of the classical wave equation were carried out; a receptance analysis was also developed which allows the undamaged and cracked portions of the beam to be separated in the analysis. Invisible cracks, which had been indicated by acoustic emission, were successfully detected in both rigs. The correlation between recorded acoustic emissions and specific damping capacity measurements supports the validity of both techniques. Some correlation between properties and measured microstructures has been obtained here. These quantitative methods for the measurement of the microstructure of composite materials should prove very useful in a wide range of applications.

Fibras são definidas como o conjunto formado de filamentos orientados na direção da cadeia molecular e são parte fundamental na vida diária do ser humano, encontradas de várias formas, tais como filamentos, fios, feixes, cordas, tecidos, compósitos, revestimentos, entre outras. Elas abrangem diversas áreas, tais como civil, mecânica, elétrica, eletrônica, militar, naval, náutica, aeronáutica, saúde, medicina, ambiental, comunicação, segurança, espacial, entre outras. A fibras são divididas em duas classes distintas, naturais e químicas, que compõem as subclasses sintéticas e artificiais. Podem ser produzidas de vários materiais, tais como lã, algodão, raion, linho, seda, rocha, náilon, poliéster, polietileno, polipropileno, aramida, vidro, carbono, aço, cerâmica, entre outros. Em nível global, as fibras químicas correspondem a 59,9% do mercado, sendo as fibras sintéticas tipo poliéster as mais utilizadas, com 63%. Necessidades vitais têm levado ao desenvolvimento de fibras multifuncionais e o foco mudou nos últimos dez anos com a utilização da nanotecnologia para fibras de responsabilidade ambiental e fibras inteligentes. O estudo das propriedades mecânicas e dos mecanismos de fratura das fibras é de grande importância para caracterização e entendimento das causas de falhas. Para este propósito foram selecionados tecidos fabricados com fibras sintéticas de alto desempenho do tipo náilon e poliéster, utilizadas em produtos de engenharia tais como pneus, correias, mangueiras e molas pneumáticas, as quais foram analisadas em cada etapa de processamento. Amostras das fibras foram retiradas de cada etapa de processamento para análise por ensaios destrutivos de tração e microscopia eletrônica de varredura. Os resultados de análise das propriedades mecânicas mostraram perda de resistência por temperatura e tensões multiaxiais durante as etapas de processamento da fibra. Por meio de ensaios de microscopia foi possível determinar contaminações, manchas superficiais, deformações plásticas, delaminações, variações nas faces de fratura dos filamentos e analisar, na interface fibra-borracha, o nível de adesão. Estas irregularidades e variações são causadas durante as etapas inerentes ao processo de fabricação. / Fibers are groups formed by molecular-chain-oriented filaments. Fibers play a fundamental role in human beings daily life and they can be found in several forms and geometries, such as filaments, yarns, beams, rope, fabric, composite, coatings, others. They are used in various segments such as civil, mechanical, electrical, electronics, military, naval, nautical, aviation, health, medicine, environment, communications, safety, space, others. Fibers are divided into two distinct classes: natural and chemical ones, which cover synthetic and man-made sub-classes. They can be produced from several materials, such as wool, cotton, rayon, flax, silk, rock, nylon, polyester, polyethylene, poly-propylene, aramid, glass, carbon, steel, ceramic, others. Globally, the participation of chemical fibers corresponds to approximately 59,9%, and the synthetic fiber polyester, the most used one, represents approximately 63% of the world market. Vital needs have led to the development of multi-function fibers and the focus has changed in the last 10 years with the use of nanotechnology for environmental responsibility and smart fibers. The study of mechanical properties and fracture mechanisms of fibers is of great relevance for characterization and understanding of causes as consequence of failures. For such reason, it was selected technical fabrics made of high performance synthetic fiber nylon-and-polyester type, used in engineered products such as tires, belts, hoses and pneumatic springs, which have been analyzed in each processing phase. Fiber samples were extracted after each processing phase to be analyzed, by traction destructive tests and scanning electron microscopy. The results of analysis of mechanical properties showed loss of resistance to temperature and multi axial stress during fiber processing phase. Through microscopy tests, it was possible to find contamination, surface stains, plastic deformations, scaling, variations in the fracture faces of the filaments and analyze in the fiber-rubber interface, the level of adhesion. These irregularities and variations are caused during the stages of the process.

O trabalho investiga a influencia dos parametros de processo: relacao D/Y e numero dos discos do agregado de texturizacao nas propriedades de frisagem dos filamentos de poliester texturizados por falsa torcao. Sao realizados ensaios numa texturizadeira industrial simulando diferentes niveis dos fatores D/Y e numero de discos.Analises estatisticas sao apresentadas e comprovam a influencia dos fatores nas caracteristicas de frisagem com nivel de confianca de 5%. Verifica-se que a combinacao de D/Y elevado com numero de discos elevado aumenta os valores dos parametros de frisagem do fio texturizado. / The work investigates the influence of process parameters: the factor D / Y and the aggregate number of disks in the texturing properties crimping of textured polyester filaments for false twist. Tests were performed in an industrial texturing machine simulating different levels of factors D / Y and number of discs. Results of statical analyses are presented and show the influence of factors on the characteristics of crimping with a confidence level of 5%. It is found that the combination of D / Y with a high number of discs increases the high values of the parameters of the crimp textured yarn.

The aim of this research was to prepare high performance and fully biodegradable polymer nanocomposites. The most representative polymers classified as biodegradable are poly(!-caprolactone) (PCL) (issued from petrochemistry) and polylactide (PLA) (issued from renewable bio-resources). Biodegradable nanoparticles purposely extracted from biomass were selected, namely Cellulose NanoWhiskers (CNW) and Starch NanoCrystals (SNC). CNW are rod-like nanoparticles with 2 nanometric dimensions while SNC consists in nanosheets, thus with 1 nanometric dimension. A 3 nanometric-dimension particle often considered as “silica- type nanocage” was selected to complete this study, namely Polyhedral Oligomeric Silsesquioxane (POSS). The addition of such nanoparticles was expected to enhance several properties of the filled polymer matrix, especially thermo-mechanical performances and extent of crystallinity. In this field, the quality of the nanoparticle dispersion throughout the matrix is an essential parameter to produce nanocomposite materials with largely improved properties. One of the most cited techniques to overcome nanofiller aggregation and even agglomeration relies upon the creation of strong chemical bonds between the nanoparticle and the polymer matrix, leading to the preparation of so-called nanohybrids. For that purpose, the surface of the nanoparticles was first modified by chemical grafting and polymerization reactions. The ring-opening polymerization (ROP) of e-caprolactone and L,L-lactide catalyzed by tin(II) 2- ethylhexanoate (tin octoate, Sn(Oct)2) was initiated from functional groups available on the nanoparticle surface. The grafting efficiency was demonstrated for the three investigated nanofiller/polyester systems. Different characterization techniques were approached depending on the nanofiller nature. In a second step, the so-formed nanohybrids were used as “masterbatches” and dispersed in their corresponding commercial polyester matrices, i.e. PCL and PLA, by melt-compounding using a mini-lab twin screw extruder. The nanocomposite materials were fully characterized, correlating morphological observations with thermal, mechanical and rheological properties. To highlight the beneficial effect of the surface covalent grafting, simple melt-blends, i.e., containing unmodified nanofillers and polyester matrices (PCL or PLA) were prepared. The level of property improvement was most of the time directly related to the degree of nanofiller dispersion, and proved systematically better in case of masterbatch-based materials. Keeping in mind the effect of the nanoparticle geometry, as well as its mechanical modulus, crystallinity or extent of dispersion within the polyester matrix, the rod-like 2D-nanofiller, namely cellulose nanowhiskers extracted from ramie, appeared as the most efficient candidate for polyester reinforcement. The incorporation of PCL chains surface-grafted onto CNW contributed to substantially increasing the overall thermo- mechanical properties, most likely due to the formation of a strong physical chain network between surface- grafted chains and chains composing the matrix. Additionally, CNW-based nanohybrids revealed their potential as both nucleating sites dramatically increasing the crystallization rate of PLA matrix and compatibilizing PCL/PLA immiscible blends.

The unsaturated polyester/silica hybrids have been synthesized via sol-gel process and characterized in an effort to obtain a transparent hybrid material in this study, with emphasis on the effects of silica precursors and coupling agents. Chemical properties, thermal properties, and morphology of the hybrids were investigated by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that silica particles can be dispersed homogeneously in the UP matrix; also, physical and chemical interactions at the interface between UP and silica can be enhanced by adding coupling agents into the system. From the thermal and chemical properties measurement, the decomposition temperature of UP backbone and the heat distortion temperature (HDT) of UP/Silica hybrid were higher than pure UP. Solvent-resistance of UP/Silica hybrid was also enhanced by adding coupling agents. A model illustrating the chemical and physical interaction at the interface due to the addition of coupling agents is proposed to explain the resulted obtained.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2004. / Collard, David, Committee Co-Chair ; Schiraldi, David, Committee Member ; Liotta, Charles, Committee Member ; Weck, Marcus, Committee Member ; Srinivasarao, Mohan, Committee Member ; Kumar, Satish, Committee Co-Chair. Vita. Includes bibliographical references.

Om människor fortsätter med det konsumtionsbeteende som råder idag kommer jor-den resurser ta slut. Den fossila råvaran petroleum används vanligtvis vid framställ-ning av polyester och polyamid. Petroleum har en 100 000 årlig process, vilket är en ofantlig skillnad i förhållande till den takt som det förbrukas. Därför har eventuella möjligheter att återskapa en ny filament av återvunnet syntetiskt blandmaterial un-dersökts i detta arbete. Det finns befintliga metoder för att återvinna polyester och polyamid som homogena material. Dock vid återvinning i en gemensam process av materialen får den slutliga produkten en försämrad kvalité. Mekanisk och kemisk återvinning fungerar för att framställa syntetiska filament men i dagsläget kan endast den kemiska ge likvärdig kvalité på det återvunna filamentet i förhållande till den jungfruliga. Det har hittats ett flertal separationsmetoder som antas kunna tillämpas till bland-materialet. Olika egenskaper såsom densitet, polaritet och laddningsmöjligheter kan utnyttjas för att separera polymererna. Polyester och polyamid antas kunna separe-ras, dock görs inte detta på industriell basis troligtvis på grund av kvantitet, resurser och pris. / If people continue with the present consumption behaviour, the earth´s resources will run out. The fossil raw material petroleum is normally used in the manufacture of polyester and polyamide. Petroleum has a 100 000 annual process, which is a huge difference compared to the rate at which it is consumed. Therefore, any opportunities to recreate a new fibre from recycled synthetic bland materials are studied in this work. There are existing methods to recycle polyester and polyamide as homogeneous ma-terials. However, the recovery in a joint process get the final product a degraded quality. Mechanical and chemical recycling makes it possible to produce new syn-thetic filaments, but in the current situation, the chemical will provide comparable quality of the recycled filament in relation to the virgin. Several separation methods can be applied to the blend material. Various properties such as density, polarity and charging possibilities can be used to separate polymers. Polyester and polyamide are assumed to be separated, however, is not done on an industrial basis, probably because of the quantity, resources and money.

No description available.

Prolonged therapy required to effectively treat mycobacterial infection frequently results in severe dose-limiting side-effects and drug resistance due to patient non-compliance with protracted dosage regimens. Biodegradable poly-a-hydroxy acid microspheres and microcapsules containing rifampicin (RIF) and isoniazid (INH) respectively have been prepared with the intention of providing high sustained site-specific concentrations to overcome some of the shortcomings of existing oral treatments. Due to the high dose, hydrophilicity and instability of both drugs, formulation strategies to attain high drug loading and methodologies to characterize in vitro drug release during ongoing decomposition were required. Stability indicating HPLC assays to quantify drug release have been developed, validated and applied to monitor drug release based on cumulative quantification of drug and degradates. A mathematical correction for serial decompositions associated with RIF was made based on the terminal pseudo equilibrium observed during stability studies. An isocratic HPLC assay was prospectively developed for the quantification of both drugs and their major metabolites in biological samples. Further preformulation studies confirmed the absence of significant polymorphs for both drugs when recrystallized from solvents later used in formulation development. Furthermore, thermal analysis revealed only modest interaction between the drugs and Resomer®. The high and moderate water solubilities of INH (145 mgmL-1) and RIF (1 mgmL-1) determined the selection of spray-drying (SD) and emulsion solvent evaporation (ESE) for RIF, whereas preparation of INH microcapsules relied solely on the former technique. Examination of the effects of varying RIF: polymer ratio, phase volumes and continuum presaturation with selected poly(L-lactide) and poly(D, L-lactide-co-glycolide) (PDLGA) Resomer® identified optimum conditions to maximize drug loading during a comparison of aqueous ESE with spray-drying with a range of nine further amorphous Resomer® polymers. Although yields were generally higher with ESE (85-90 %), SD (45- 75 %) was considered a superior preparation technique on the basis of the rapid production of microspheres of high and predictable drug loading (100 % of that attempted), with monodisperse granulometry and superior morphology. Release profiles were typically asymptotic characterized by a rapid `burst' of release followed by a slow release of residual entrapped RIF, irrespective of the preparative technique or polymer used. Poor yields (7.2 %) when SD low molecular weight (MW) PDLGA (8 kD) were greatly enhanced (74.8 %) by reduction in drying temperature and substitution of chloroform: dichloromethane (CFM: DCM) (1: 1) cosolvent with DCM. These conditions were adopted as the optimum parameters for further studies of blends of low (2 kD, R104) and moderate (11 kD, R202H) MW poly(D, L-lactide) (PDLLA); materials which demonstrated excellent sprayability and dramatically modulated the release of drug when combined compared to their use alone. Drug release showed a remarkable dependence on blend, dramatic acceleration being observed between 44 and 48 %w/w R104. Release over this range showed a marked dependence on medium temperature and led to the proposal of an autohydration mechanism linked to the hydrophilicity and glass transition (T9) of the blend which accounted for the sigmoidal profiles observed. First order dependence of release allowed calculation of Arrhenius derived activation energies of drug release in glassy anhydrous and rubbery plastic matrices of 630 and 320 J mol-1. Hydration and thermal studies supported the postulated diffusion mechanism, whereas granulometric and morphological examinations demonstrated that erosion did not contribute significantly. The criticality of matrix composition was further highlighted when interchange with nominally identical polymer, R202H, shifted the critical composition to 30 %w/w R104. Moreover, this observation contested the batch-to-batch reproducibility of commercial polymer. Substitution of DCM with halothane (HAL) and acetone (ACT) had a profound influence on the properties of compositionally identical ('R104: R202'H, 30: 70) microspheres, particularly release kinetics. This was attributed to the more rapid drying kinetics with the poor solvent, ACT, and the generation of a porous matrix. Consequently, drug was largely released during the 'burst' phase. Superior solvents, HAL and DCM resulted in enhanced matrix coherence at the expense of considerable residual solvent burdens (6 - 12.5 %), which allowed extensive matrix relaxation as solvent was lost with first order kinetics. This ageing process was followed by the development of an endotherm associated with the Tg as the matrix stabilized with a resultant increase in the induction period and a general retardation of drug release. Extension of the concept of blending R104 as release 'initiator' to a range of MW PDLGA of 50: 50 and 75: 25 comonomer ratio as release 'modulator' was of limited success generating release profiles reminiscent of each polymer when used alone. The magnitude of the 'burst' correlated to the precipitation kinetics of the predominant complementary PDLGA polymer as determined by cloud-point titration. Due to the more hydrophilic nature of the copolymers, at the critical concentration uncontrolled hydration resulted in a single rapid release phase. Spray-dried biodegradable INH microcapsules were prepared by a two stage process whereby SD cores of drug or in combination with biodegradable albumin or casein were subsequently coated with PDLGA by SD. The highly crystalline, aggregated and irregular morphology of SD drug resulted in poor coating efficiency and a rapid release of encapsulated drug. Protein microspheres of superior sphericity allowed more effective coating and hence slower INH release. It is concluded that SD has excellent industrial potential for the preparation of biodegradable poly-a-hydroxy acid microspheres for high dose drugs to be delivered directly to their site of action, e. g., intra-pulmonary. Indeed, the granulometry of these particles and, in particular, the hydrophilic character of blends of PDLLA described have considerable potential for the sustained delivery of drugs in the low volumes of fluid that prevails in the lung. These formulations might offset some of the limitations of current oral antimycobacterial therapy.