Dissertations / Theses on the topic 'Polyester'

A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel chain-wire mooring lines is extended to allow for the large elongation in a mooring line, the dependence of the modulus on tension, and energy dissipation of a polyester rope under mean and cyclic loads. The modified CABLE3D is then integrated into a numerical package, known as COUPLE6D, for computing the interaction between a floating structure and its hybrid polyester mooring system. The Deepstar Spar is chosen in this study to represent the floating structure. By considering large elongation in polyester ropes in numerical simulation, the static offset curve of a polyester mooring system is softer than that calculated under the assumption of small elongation. That is, about 10% reduction in restoring force at the mean offset position of the Spar under the impact of 100-year hurricane storm. The effects of the mean loads on the modulus of polyester ropes are much greater than those of the dynamic loads. Hence, the former is more important in the simulation of the response of floating structures. The energy dissipation in polyester ropes under cyclic loading does not play significant roles in the responses of the Spar and tensions in a polyester mooring system. The above findings, although observed based on the numerical simulation of a particular floating structure, namely Spar, may have implications to other floating offshore structures moored by a polyester mooring system. Two systems are simulated in two different met-ocean conditions: hurricane and loop current condition. To study the properties of polyester, numerical simulation were conducted in three ways. Those are related to the modulus based on mean load, mean and dynamic loads, and structural damping respectively. Through the simulation, statistics of motions of the hull and tension in the mooring lines are compared with those of a conventional steel mooring system.

Enzyme selectivity means that the enzyme´s preferences towards competing substrates will be different. In this thesis, the enzyme selectivity has been studied for utilization in synthesis of functionalized macromonomers. The aim was to study how the inherent –or introduced – selectivity of lipases can be used to introduce thiol‐ or enefunctionalities into short polyesters. Thiol‐ and ene‐functionalized renewable organic precursor molecules in combination with thiol‐ene click chemistry opens up for a sustainable material production. Lipases do not normally affect ene‐moieties and the preference towards thiols is low, enabling introduction of these functional groups for further modifications. In addition, lipases have been shown to be good catalysts in the formation of polyesters, both via ring‐opening and polycondensation polymerization. In paper I Candida antarctica lipase B was used to end‐functionalize poly(ε‐caprolactone) with free thiols in a one‐pot reaction. The advantage of using achemoselective lipase as catalyst was that no protection of the thiol was needed. The chemoselectivity displayed by Candida antarctica lipase B turned out to be 88 000 in favour of the alcohol (paper II). Rhizomucor miehei lipase showed less pronounced chemoselectivity. The largest contribution to the selectivities was derived from the more than two orders of magnitude higer KM towards the thiol compared to the alcohol. Thiols can be cross‐linked with enes in radical reactions to form networks, enabling formation of materials. One promising renewable molecule containing an acrylate moiety is itaconic acid. In paper III the selectivity towards the two esters in dimethyl itaconate was investigated and the active site of Candida antarctica lipase B was redesigned to generate variants with increased and decreased selectivity. One variant showed 14‐fold higher selectivity and could regioselectively add dimethyl itaconate onto a diol. This variant could be used in end‐functionalizations of polymers, introducing acrylate‐ester end‐groups. The enzyme selectivity towards lactones and their corresponding polyesters is of importance when designing a ring‐opening polymerization reaction. In paper IV Candida antarctica lipase B was found to prefer ω‐pentadecalactone and polyesters over ε‐caprolactone ten‐fold, while Humicola insolens cutinase preferred ε‐caprolactone and its corresponding polyester four‐fold over ω‐pentadecalactone and its polyester. From a selectivity point of view, Candida antarctica lipase B and Humicola insolens cutinase would be equally good in ring‐opening polymerization of ω‐pentadecalactone, while in the case of ε‐caprolactone Humicola insolens cutinase would be the preferred choice.
QC 20110608

The work contained in this thesis examines how the properties of polyester film substrates affect the structure and performance of thin coatings vacuum-deposited upon them, particularly with regards to their function as gas barriers for use in packaging. By modifying the surface of a PET film prior to deposition, with either oxygen or argon plasma, an increase in adhesion between the polymer and coating by 50% occurs for both aluminium and SiOₓ layers. A reduction in the density of pinhole defects is also observed after such treatment. A set of silicon oxide (SiOₓ) coatings, deposited using a novel PECVD method, that display excellent barrier to water vapour permeation, impressive mechanical properties and good adhesion to the base film, is studied. Water vapour transmission rates as low as 2 x 10⁻⁴g m⁻² day⁻¹; are reported for these thin films as a result of their thickness and structure, where the deposition of the coating in several layers prevents defects extending throughout the coating. A high level of carbon incorporated in these films makes them flexible with relatively high strain to failure and low stress. The properties of the SiOₓ coatings vary significantly depending on the substrate on which they are deposited. By tailoring the polyester film properties during manufacture, a wide range of substrates with differing properties is produced. The most relevant appear to be the surface thermal and mechanical properties. SiOₓ layers on heat stabilised PET (with or without an additional primer layer) and PEN outperform an equivalent coating on standard PET film by two orders of magnitude, in terms of gas barrier, and also possess superior mechanical properties. This is due to the enhanced thermal stability of the surfaces of these films as they undergo heating during deposition, as thermally induced motion of the chains at the surface of a plain PET film is thought to create defects. Substrate roughness is found to affect the morphology of deposited coatings but not the permeation of gas through them. The importance of substrate selection is illustrated by substituting PET with PEN, for example, where improvement in barrier is comparable to that achieved by coating a polymer film in the first place.

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.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 55-57).
The objective of this research is to enable large part or high volume manufacturing processes to make consumer or industrial products from a cork reinforced polymer composite, similar to current applications of glass reinforced polyester. The low initial investment and high flexibility of the spray lay-up process make it an attractive candidate to study. A spray lay-up apparatus was successfully constructed and employed in manufacturing parts from a hybrid material composed of granulated cork, chopped glass strand, and a polyester matrix. The material was tested for tensile and flexural properties following relevant ASTM standards. The material was found to have a tensile strength of 4.4 MPa and tensile modulus of 850 MPa. The flexural strength and modulus were 9 MPa and 830 MPa, respectively. Adding a fiberglass skin to the cork hybrid significantly improved its flexural strength. Additionally, a small turbine blade prototype was created as a proof of concept. It is recommended that further work focus on optimizing the hybrid material's properties, re-designing and optimizing the apparatus used for the spray-up process, and demonstrating material viability by manufacturing a cross section of a large turbine blade.
by Benjamin J. Pope.
S.M.

A commercial unsaturated polyester resin has been used in combination with commercial multiwalled carbon nanotubes (MWNTs) to study the effects of this nanofiller on the electrical properties of the mix in the liquid state, during the cure and in the solid state. The level of addition of the nanotubes ranged from 0.05 to 0.3 wt%. The dispersion of the filler particles in the matrix was carried out combining triple roll milling, horn sonication and high shear mixing. Qualitative optical and electronic microscopy characterisation supports the development of novel techniques for real-time quantitative assessments of dispersion quality. Fitting of shear dependent viscosity, measured between 0.1 and 100 s-1, to Carreau's model has been shown to provide an indicator of the state of nanotube dispersion in the mixture. Additionally, liquid electrical conductivity measurements offer the option of on-line monitoring, providing a promising tool for process optimisation. The formation of an effective conductive network of nanotubes during the cure was investigated by combining impedance spectroscopy measurements and equivalent circuit modelling with two parallel RC circuit in series with each other. This allows in-situ observation of the key phenomenon responsible for the electrical conductivity of the nanocomposite, namely the filler re-aggregation during cure. Optimisation of dispersion and cure parameters results in a nanocomposite showing conductive behaviour in the solid state, achieving DC conductivity of 0.13 S/m at 0.30 wt% loading. The percolation threshold was estimated to occur at 0.026 wt% filler loading. The conductivity achieved is comparable to state-ofthe-art epoxy thermosetting nanocomposites based on use of carbon nanotubes of equivalent quality. Successful laboratory scale trials demonstrated the suitability of the materials in copper electroplating and resistance heating. An industrial scale up trial of a 40 kg batch was carried out, using the dispersion and the monitoring techniques developed in the study.

Polyethylene terephthalate (PET) is used to make textile fibres, bottles and packaging films. The global production in 2013 was 65 Mt, growing at 5-7% per year over the last decade. PET is manufactured by the continuous polymerisation of ethylene glycol and terephthalic acid, both of which are produced from fossil fuels. This Dissertation examines the environmental impact of manufacturing PET using process modelling and life cycle assessment. The work focused on ways of reducing the environmental impact of the polymer manufacture by using biomass instead of conventional fossil fuels, either as a raw material for producing ethylene glycol or terephthalic acid, or as a fuel to supply process heating or electricity. The environmental impacts of producing a PET bottle using ethylene glycol derived from two types of biomass, sugarcane and willow, were investigated and compared with conventional production. For sugarcane, the sugars were fermented to bioethanol, then dehydrated to ethylene. By using sugarcane, it was found that the global warming potential (GWP) and non-renewable resource use could be reduced by 28% and 16% respectively. Ethanol, and hence ethylene, can also be produced from willow, a lignocellulosic biomass, which could also potentially reduce nonrenewable resource use by 16%. However, for sugarcane there was a significant increase in other environmental impacts, e.g. acidification and eutrophication potential; these increases were smaller when using willow. From supply chain analysis, the transport of finished and intermediate products only made a minor contribution to the environmental impacts. The principal raw material for terephthalic acid is p-xylene, conventionally made from naphtha. It is feasible, however, to manufacture p-xylene by the catalytic conversion of sugars extracted from biomass sources. A PET bottle made using p-xylene derived from willow could reduce the GWP and non-renewable energy use by 32% and 2%, respectively, or 87% and 26% using sugarcane. Again, the disadvantage of using biomass was that all other environmental impact categories were increased over materials derived from petrochemicals. Biomass can also be used for generating process heat or electricity. It was found that the best possible use of biomass within the PET value chain would be combustion to supply process heat, followed closely by burning to generate electricity. In fact, only where ethylene is produced via the fermentation of sugars from hydrolysed willow, and for one measure, GWP, was producing a chemical from biomass more sustainable than combustion for process heating. This conclusion is sensitive to the energy sources from which heat and grid electricity are otherwise produced and might therefore alter as future conventional energy sources change. Finally, the possible savings in GWP and energy use by recycling PET bottles were evaluated for both closed-loop and open-loop systems. Open-loop recycling gave better savings for GWP and energy use when compared with closed-loop recycling. The transport associated with the international trade of baled bottles, largely imported by China, has a minimal effect on the possible savings by recycling. This work has established that there is scope for improving the sustainability of the polyester industry; however trade-offs need to be carefully considered on a case by case basis.

There is an increased awareness of the textile dyeing and finishing sector’s high impact on the environment due to high water consumption, polluted wastewater, and inefficient use of energy. To reduce environmental impacts, researchers propose the use of dyes from natural sources. The purpose of using these is to impart new attributes to textiles without compromising on environmental sustainability. The attributes given to the textile can be color and/or other characteristics. A drawback however, is that the use of bio-sourced dyes is not free from environmental concerns. Thus, it becomes paramount to assess the environmental impacts from using them and improve the environmental profile, but studies on this topic are generally absent. The research presented in this thesis has included environmental impact assessment, using the life cycle assessment (LCA) tool, in the design process of a multifunctional polyester (PET) fabric using natural anthraquinones. By doing so an eco-design approach has been applied, with the intention to pave the way towards eco-sustainable bio-functionalization of textiles. The anthraquinones were obtained from the root extracts of the madder plant (Rubia tinctorum L.), referred to as madder dye. The research questions were therefore formulated related to the use of madder dye. Three research questions have been answered: (I) Can madder dye serve as a multifunctional species onto a PET woven fabric? (II) How does the environmental profile of the dyeing process of PET with madder dye look like, and how can it be improved? (III) What are the main challenges in using LCA to assess the environmental impacts of textile dyeing with plant-based dyes? It is concluded that there is a potential for the madder dye to serve as a multifunctional species onto PET. Based on the encouraging result, a recommendation for future work would be to focus on the durability of the functionalities presented and their improvement potential, both in exhaustion dyeing and pad-dyeing. LCA driven process optimization of the exhaustion dyeing enabled improvement in every impact category studied. However, several challenges have been identified which need to be overcome for the LCA to contribute to the sustainable use of multifunctional plant-based species in textile dyeing. The main challenges are the lack of available data at the research stage and the interdisciplinary nature of the research arena. It is envisaged that if these challenges are addressed, LCA can contribute towards sustainable bio-functionalization of textiles.
Le secteur de la teinture et de l’ennoblissement textile est de plus en plus conscient de son impact sur l’environnement dû principalement à la consommation élevée de l’eau et à sa pollution, et aux pertes d’énergie. Pour réduire ces impacts, les chercheurs proposent l’utilisation de molécules issues de ressources naturelles, pour traiter les textiles en limitant les impacts sur l’environnement. C’est le cas pour l’obtention de textiles colorés ou pour l’attribution de toute autre fonctionnalité. Cependant, il n’est pas évident que ces molécules bio-sourcées n’aient aucun impact sur l’environnement. On comprend l’importance d’évaluer les impacts de leur utilisation et d’améliorer leur profil environnemental. Or ce type d’étude est peu présent dans la littérature. La recherche présentée dans cette thèse comporte l’évaluation des impacts environnementaux en utilisant l’outil d’analyse du cycle de vie (ACV) pour la conception du traitement d’un tissu de polyester (PET) multifonctionnel avec des anthraquinones naturelles. La méthodologie d’éco conception que nous avons appliquée ouvre la voie à une bio-fonctionnalisation des textiles plus respectueuse de l’environnement. Les anthraquinones ont été obtenues par extraction des racines de plantes de garance et constituent le colorant appelé garance. Les trois questions principales abordées lors de ce travail de recherche sont formulées autour de l’utilisation de la garance : (I) Peut-on traiter les tissus de PET avec de la garance pour obtenir des propriétés multifonctionnelles ? (II) Quel est le profil environnemental du procédé de teinture du PET par la garance et comment l’améliorer ? (III) Quels sont les principaux challenges pour l’utilisation de l’ACV dans l’évaluation environnementale du traitement des textiles par des colorants naturels? Nous avons montré que la garance peut être utilisée pour conférer des propriétés multifonctionnelles au PET. Ensuite, nous avons pu orienter notre étude pour améliorer la durabilité des traitements par les procédés de fonctionnalisation à la fois par épuisement ou par foulardage. En s’appuyant sur l’ACV, l’optimisation de la teinture que nous avons réalisée réduit tous les impacts sur l’environnement. Cette étude nous permet d’identifier les challenges qui doivent être surmontés pour que l’ACV puisse contribuer à l’utilisation de bio-molécules pour la teinture des textiles dans le respect des principes de développement durable. Ils concernent le manque de données pour ces travaux de recherche et leur nature interdisciplinaire. Ainsi, en résolvant ces questions, on peut envisager aboutir à une bio- fonctionnalisation des textiles respectueuse de l’environnement.
Den höga miljöpåverkan från textilfärgning och efterbehandling, på grund av hög vattenförbrukning, dess förorening, och ineffektiv användning av energi, är idag välkänt. För att minska miljöpåverkan föreslår forskningsvärlden användning av färgämnen från naturliga resurser. Syftet med att använda dessa är att ge nya attribut till textilier utan att göra avkall på miljömässig hållbarhet. Attribut som ges kan vara färg och/eller andra egenskaper. En nackdel är dock att användningen av bio-baserade färgämnen är inte fri från att belasta miljön. Det blir därför av största betydelse att bedöma denna miljöpåverkan och förbättra miljöprofilen. Sådana studier är dock i allmänhet sällsynta. Studien som presenteras i denna avhandling har inkluderat miljöpåverkans- bedömning, med hjälp av livscykelanalys (LCA), i designprocessen av en multifunktionell polyester (PET) väv via naturliga antrakinoner. Genom att göra så har ett eko-design tillvägagångssätt använts, med avsikt att bana väg för miljömässigt hållbar bio-funktionalisering av textil. Antrakinonerna erhölls från rot extrakt av växten krapp (Rubia tinctorum L.), och hänvisas till som krapp färgämne. Frågeställningar var därför formulerade relaterat till användningen av krapp färgämne. Tre forskningsfrågor har besvarats: (I) Kan krapp färgämne verka multifunktionellt på en PET väv? (II) Hur ser miljöprofilen ut, från färgningsprocessen av PET med krapp färgämne, och hur kan den förbättras? (III) Vilka är de största utmaningarna med att använda LCA för att bedöma miljökonsekvenserna av textilfärgning med växtbaserade färgämnen? Det kan konkluderas att det finns potential för krapp färgämne att verka multifunktionellt på PET. Baserat på uppmuntrande resultat är en rekommendation för det framtida arbetet att fokusera på kvalitén hos de attribut som presenterats och deras förbättringspotential, både i färgning via färgbad och via foulard. LCA driven processoptimering av textilfärgningen förbättrade i varje miljöpåverkans- kategori som studerats. Emellertid har flera utmaningar identifierats som måste  övervinnas för att LCA skall kunna bidra till en hållbar användning av multifunktionella växtbaserade färgämnen för textil. De största utmaningarna är bristen på tillgängliga data i forskningsstadiet och den tvärvetenskapliga forskningsarenan. Det är tänkt att om dessa utmaningar bemästras kan LCA bidra till en hållbar bio-funktionalisering av textil.

Disputationen kan följas via länk i sal U401b, Textilhögskolan, Högskolan i Borås

Erasmus Mundus Joint Doctorate program: Sustainable Management and Design for Textiles

Thesis(Ph.D.)--Case Western Reserve University, 2010
Title from PDF (viewed on 2009-12-22) Department of Macromolecular Science and Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center

In rural parts of the world, lack of access to roads that are useable year-round significantly contributes to poverty. Suspended footbridges can improve access at locations that require medium span crossings (15 m to 64 m). This dissertation challenges the idea that modern bridges of this type must use steel rope, a well-established material for this application. Polyester rope, an unconventional bridge material, is investigated as an alternative to steel rope for rural suspended footbridges. The specific goals of this research are to: (i) characterize the static and dynamic behavior of polyester-rope bridges and (ii) determine which design criteria and system parameters will influence future design guidelines for these structures.

Numerical and analytical, static, natural frequency, and pedestrian excitation computations are performed to investigate the influence of polyester rope's material stiffness on the static and dynamic response of polyester-rope suspended footbridges. Polyester rope's low stiffness leads to larger static bridge deflections than occur for steel-rope structures. These deflections are accompanied by a nonlinear increase in a bridge's geometric stiffness and lead to high levels of safety against overloading. Polyester rope's low stiffness also requires that these bridges be prestressed to meet static and dynamic serviceability (pedestrian comfort) limits specified in footbridge guidelines. The damping ratios that are utilized in the pedestrian excitation analyses follow from the first set of full-scale physical tests that have been performed on a medium-span polyester-rope bridge.

Multi-objective optimization is utilized to find minimum volume polyester-rope and steel-rope suspended footbridge designs across the medium span range when subject to in-plane static and dynamic strength and serviceability constraints. The optimization problems are evaluated with a novel methodology that combines a genetic algorithm with static, natural frequency, and pedestrian excitation analyses. The impact of cross-sectional area, material stiffness, prestress, damping, mass, and stiffening stay elements on rope volume requirements for these bridges are investigated. Minimum volume results are presented graphically as functions of span to provide visual design aids that can be included in future bridge guidelines to facilitate comparisons between different systems under a range of constraint combinations.

Les résines polyesters sont des composants présents dans une majorité des revêtements et matériaux utilisés aujourd'hui. Ils sont obtenus par polycondensation de polyols, polyacides et monoacides. Les réglementations évoluant (REACH) et le public étant de plus en plus sensible à l'origine et l'impact des produits qu'il consomme, la substitution des produits pétrosourcés vers des matières premières renouvelables semble évidente. De nouveaux polyesters, composés majoritairement de monomères biosourcés, ont donc été synthétisés. L'acide L-(+)-tartrique a été principalement étudié, ce monomère quadri-fonctionnel étant peu utilisé dans la chimie des matériaux bien que disponible en grandes quantités et peu coûteux. Afin de caractériser les polyesters, différents tests utilisés dans l'industrie ont été mis en place, les caractéristiques physico-chimiques pouvant varier d'une application à l'autre. Différents mécanismes de réticulation ont également été explorés afin d'adapter les polyesters aux contraintes de résistance et de séchage requises. Ces mécanismes incluent la réaction entre les hydrazides et les méthyles cétones ainsi que celle des dérivés du Bore et des hydroxyles à température ambiante. La solubilité des polyesters synthétisés a également été étudiée afin d'obtenir un produit soluble en phase aqueuse capable de devenir insoluble après réticulation et séchage
Polyester binders are the main components of the coatings and materials used nowadays. They are obtained by the condensation of polyols, polyacids and monoacids. Evolving regulations (REACH) and the public being increasingly sensitive to the origin and impact of the products it consumes, petro based compounds substitution to renewable raw materials seems obvious. New polyesters, mainly composed of biobased monomers were therefore synthesized. The L-(+)-tartaric acid was mainly studied, this quad-functional monomer being barely used in materials chemistry, although available in large quantities and inexpensive. To characterize polyesters, various tests used in the industry have been established, the physicochemical characteristics may vary from one application to another. Different crosslinking mechanisms have also been explored to adapt polyesters constraints of resistance and drying. These mechanisms include the reaction between the hydrazide and methyl ketones, as well as the derivatives of Boron and hydroxyl at room temperature. The solubility of the synthesized polyesters was also studied in order to obtain a water soluble material capable of becoming insoluble after crosslinking and drying

In this work, hyperbranched aromatic polyesters-polyphenols based on 4,4-bis(4’ hydroxy¬phenyl)pentanoic acid (BHPPA) were prepared and, according to the authors knowledge, for the first time tested as precursors for polyurethane bulk resins and coatings. Comparison of poly-BHPPA with competing products The materials prepared in this work show better properties than their aliphatic polyester-polyol analoga based on 2,2-bis-(hydroxymethyl)propanoic acid (BHMPA). Especially, the solubility of poly-BHPPA in organic solvents is better and poly-BHPPAs also do not tend to microphase separation during their reaction with isocyanates, in contrast to poly-BHMPAs. The poly-BHPPA and the polyurethane networks made from them display higher Tg values than analogous poly- BHMPA compounds. Because of the high Tg of the reacting and final systems, curing must occur at elevated temperatures (90°C) in order to avoid undercure. The lower reactivity of phenolic OH groups prevents the reaction from being too fast at that temperature. A drawback of the polyurethanes based on the aromatic polyesters-polyols prepared is the lower thermal stability of their urethane bonds, if compared to aliphatic urethanes. An interesting possibility for future investigations would be the modification of the BHPPA monomer in order to change the OH functionality from phenolic to aliphatic OH, e.g. by replacement of the phenolic OH by hydroxymethyl or hydroxyethyl groups (requires a strong modification of the monomer synthesis) or simpler by reacting the phenolic OH of BHPPA with a suitable reagent like oxirane, which would lead to groups like O-CH2-CH2-OH in the place of the phenolic OH. Such a BHPPA modification should in turn yield modified “poly-BHPPA” polycondensates, which would combine the advantages of poly-BHPPA with those of aliphatic OH precursors of polyurethanes. Poly-BHPPA synthesis Hyperbranched polymers of the 4,4-bis-(4’-hydroxyphenyl)pentanoic acid (BHPPA) were synthesized successfully by the catalyzed (by dibutyltin diacetate) polycondensation of BHPPA. The products obtained were oligomers with number average molecular weight ranging from 1800 to 3400 g/mol (polymerization degree of ca. 6 to 12), displaying a first moment of functionality in the range 7 to 14. Such products were good OH precursors for the preparation of polyurethane coatings, because higher functional polymers would gel at low conversions. The analysis of the functional groups (determination of acid and hydroxyl numbers) and the 1H-NMR and the 13C-NMR spectroscopy were found to be good methods for the determination of molecular weights. The polydispersity of the poly-BHPPA products was in the range 3.5 to 6. Their degree of branching was found to be in the range 0.36 to 0.47. Poly-BHPPA containing aliphatic polyols as core monomers were also prepared successfully. Difunctional and trifunctional core monomers usually reached a full conversion of their OH groups, while the tetra- and hexafunctional core monomers were converted only to 89%. In all these products however, a considerable amount, usually even a majority, of the polymer molecules were core free. The poly-BHPPA products prepared displayed relatively high glass transition temperatures, in the range of 84°C to 114°C, obviously due to interactions between the phenol groups and to hydrogen bridging. The thermal stability of these products was also high, with decomposition occurring near 350°C (at a heating rate of 10°C / min) Kinetics investigations of the poly-BHPPA reactivity towards isocyanates The poly-BHPPA are polyphenols and were expectedly found to react significantly slower with isocyanates than aliphatic alcohols. The reactivity of poly BHPPA was also found to be somewhat lower than that of the monofunctional, low molar-mass 4 ethylphenol. Hexamethylene diisocyanate trimer, Desmodur N3300, was found to be more reactive than hexamethylene diisocyanate (HDI) or butyl isocyanate in all experiments, possibly due to a substitution effect. The substitution effect can be explained by a change of microenvironment caused by conversion of isocyanate group and OH group into urethane groups. The reactions of low-molecular-mass alcohols or phenols with low molecular weight isocyanates followed well the 2nd order kinetics, while the reactions of poly-BHPPA with isocyanates show deviations from ideal 2nd order kinetics at higher conversions. All the kinetics experiments were carried out under catalysis by dibutyltin dilaurate. This catalyst inhibits the undesired reaction of isocyanate groups with moisture. It was also found that the catalysis was necessary to reach reasonable curing times for poly-BHPPA based polyurethane networks. The uncatalyzed systems reacted extremely slowly. Preparation of polyurethane networks from poly-BHPPA The poly BHPPA products prepared were used successfully as OH functional precursors of polyurethane networks. The networks prepared contained only very low sol fractions. Acetone and also ethylene diglycol dimethylether (diglyme) were found to be good swelling solvents for the networks prepared, while methyl propyl ketone was a much poorer solvent and aromatic compounds like toluene or xylene practically did not swell the poly BHPPA based polyurethanes. The networks prepared contain a relatively high amount of cyclic bonds, 40 to 50% in the finally cured state, which is an expected result for systems with precursors of high functionality and with small distances between the functional groups. The temperature of glass transition (Tg) of the networks prepared (ranging from 68°C to 126°C) depends of the poly BHPPA precursor used: it increases with increasing molecular mass and with increasing core functionality. The choice of the isocyanate crosslinker also influences Tg: the networks made from HDI show higher Tg values, than networks made from the same poly BHPPA but crosslinked with Desmodur N3300 (Tri HDI). The urethane bonds in the networks prepared start to decompose near 140°C. The easier degradation of PU with aromatic urethane bonds is a disadvantage in comparison with aliphatic polyurethanes, whose decomposition starts at 200°C. The surfaces of polyurethane coatings prepared are smooth, displaying a roughness of ca. 20-25 nm, and relatively hydrophilic: the contact angle with water was found to be near 80°. The prepared networks are also relatively hard, possessing the Shore D hardness of 70.

L'Imagerie par Résonance Magnétique (IRM) est à l'heure actuelle la technique de visualisation préférentiellement choisie par les chirurgiens. Cependant, cette technique ne permet pas de visualiser des prothèses à base de polymères, qu'elles soient dégradables ou non. Afin de mieux évaluer la fixation, l'intégration tissulaire et le devenir de l'implantation de ces prothèses polymères, il serait souhaitable qu'elles soient visibles par IRM. Ce travail présente donc la conception et la synthèse de copolymères biocompatibles visibles par IRM destinés à être introduit dans la composition de prothèses pour applications temporaires ou permanentes. En utilisant la modification chimique en position alpha de fonction ester décrite précédemment par notre laboratoire, nous avons greffé de façon covalente et par une liaison stable un chélate du gadolinium (le DTPA) sur la chaîne de la PCL (dégradable) et du PAM (non dégradable). Le gadolinium a ensuite été complexé par le DTPA greffé préalablement. Ces nouveaux copolymères ont été caractérisés par RMN et CES, et le taux de gadolinium évalué par ICP-MS. Des images d'IRM ont été réalisées in vitro et in vivo sur des appareils contenant des aimants de 7 Teslas (recherche) et 1,5 Teslas (clinique). Ces images montrent qu'un treillis en polypropylène enduit de copolymère greffé par un complexe DTPA-gadolinium est visible par IRM, ce qui laisse entrevoir un large champ d'applications pour ce type de composé
Magnetic Resonance Imaging (MRI) is currently the visualization technique that surgeons preferentially choose. However this technique does not allow the visualization of polymer-based prosthesis, whether they are degradable or not. In order to best assess adhesion, tissue integration and the future of implantation of these polymer prosthesis, it would be advisable to make them visible in IRM. This work presents the conception and the synthesis of biocompatible copolymers visible in IRM meant to be implanted under the form of prosthesis for temporary or permanent applications. Using the chemical modification in alpha position of ester function, previously described by our laboratory, we grafted a gadolinium chelate, in a covalent way and forming a stable bond on PCL (degradable) and PMA (non degradable) backbone. Gadolinium was then complexed by DTPA previously grafted. Those new copolymers were characterized with NMR and SEC, and the rate of gadolinium was assessed by ICP-MS. MRI images were taken in vitro and in vivo on devices containing 7-Teslas (research) and 1,5 Teslas (clinical) magnets. These images show a poly(propylene) mesh coated with grafted copolymer containing complex gadolinium which is visible in MRI. It will consequently improve the prospects of applications for this kind of MRI-visible compound

The aim of the work described in this thesis was to develop novel semi-crystalline, semi-aromatic polyester-based materials with improved thennal properties relative to their parent polymers, specifically poly(ethylene terephthalate) (PET) and po)y(ethylene-2,6-naphthalate) (PEN). This work involved the design and development of a small-scale (2-10 g) vacuum polyesterification rig, synthesis of a variety of suitable comonomers - both known and unknown - and the synthesis of a range of novel copolymers by incorporating these comanomers through melt-phase polycondensation. Several comonomers were synthesised which could potentially enforce are-entrant chain-fold through confonnational restrict ions. However, these comonomers typically hindered the crystallisability of the copolymers and had no significant effect on Tg• Double Tgs were apparent for a small number of these copolymer compositions. A wide range of imide-containing comonomers was synthesised and incorporated into both PET and PEN. The resulting novel copoly(ester-imide)s generally displayed enhanced Tgs but showed a reduction in crystallinity at levels of 5 to 15 mol% diimide. Annealing of these copolymers gave materials with a greater Xc. often close to those of their respective homopolymers. The diimide monomer N,N-bis-(2-hydroxyethyI)pyromeJlitic diimide (POI), incorporated at 5 mol% into PEN, gave a Tg 10°C higher as well as a T m 10°C lowerthen PEN, with a comparable value of Xc once annealed. Finally, a range of copolymers containing 3,3',4,4'-biphenyldiimide units were introduced into PET, PEN and poly(butylene-2,6-naphthalate) (PBN). Crystallinity was observed for all compositions investigated with PEN (2-25% comonomer), and the degree of crystallinity and rate of crystallisation increased progressively above 5 mol%. X-ray powder and fibre diffraction techniques revealed that compositions containing ~ 5 mol% diimide, annealed at 180°C, have a completely different crystalline structure from PEN itself. The new unit cell for this novel copolymer is monoclinic, space group C2/m, with two chains passing through the unit cell, and cell parameters a = 10.50, b = 6.85, c = 13.28 A, f3 = 141.6°