Specific Interactions in Carbon Dioxide + Polymer Systems Anupama Kasturirangan 163 Pages Directed by Dr. Amyn S. Teja Weak complex formation in CO2 + polymer and CO2 + copolymer systems containing C=O and C-F groups was quantified using in situ FTIR spectroscopy. The enthalpy of interaction thus obtained was directly incorporated into a lattice model and compressibility effects were accounted for via ratio of free volumes in modified segment number. CO2 + fluropolymer phase behavior could be correlated within experimental error (AAD of about 2%) using the new model, a task that has been beyond the capability of published models and it was also possible to predict phase equilibria of CO2 + PLGA copolymer systems with a single parameter obtained by fitting cloud point behavior in a reference system (CO2 + PLA in this case).New data on sorption equilibria in several CO2 + PLGA systems were obtained using a quartz crystal microbalance (QCM) and new data on Tg depression in the CO2 + PLA system were also obtained using a high pressure DSC method and used to demonstarte that model parameters are valid over extended pressure ranges. The new compressible lattice model developed is thus able to correlate cloud points, sorption equilibria, glass transition temperatures, and melting points using a single parameter. The model is therefore likely to be beneficial in many applications involving CO2 + polymer systems including drug delivery and encapsulation, polymer coating, and membranes for natural gas separations.

The production of fine filaments using the melt spinning process needs considerable effort. A thermoplastic melt is stretched from the spinneret under a constant take-up speed. The high performance thermoplastic PEEK is solidified in the melt spinning process in a small distance and short time. Therefore, the fine PEEK filaments in the fibre formation zone underwent a high deformation and cooling rate. To make the melt spinning process stable and to produce the fine PEEK filaments, material properties and material behaviour are examined using on-line and off-line measurements. The fibre speed measured using Laser Doppler Anemometry and simultaneous temperature measured using infrared thermography enable both the strain rate and consequently the apparent extensional viscosity to be estimated. This provides the apparent extensional viscosity over the spinning line, which can itself show the structural development of PEEK fibres in the fibre formation zone, i.e. necking and solidification phenomena. The one-dimensional fibre formation model must include both procedural and material parameters. The heat transfer coefficient was estimated using the filament temperature measurement and showed a relatively high contribution of radiation and free convection in comparison to forced convection near the spinneret. The improved model of PEEK fibre formation gave a good agreement to both temperature and speed measurements, and also confirmed the high deformation rate effect on the extensional viscosity, which could be simulated with a properly generalised Newtonian constitutive equation. The end properties of the fibres, such as as-spun filament fineness, orientation (expressed using total birefringence) and total crystallisation (examined using DSC) are investigated in relation to different spinning conditions, i.e. take-up speed, throughput and the draw down ratio. The tensile test diagram results, measuring phenomena such as the elongation at break, tenacity, and the Young modulus of elasticity are also analysed in order to complete the correlation of the above-mentioned spinning conditions to the structural properties of as-spun fine PEEK filaments. The melt spinning of fine PEEK fibres under different spinning conditions is examined with the purpose of finding the optimum take-up speed and throughputs. Other spinning conditions, such as the temperature of melt processing, and the arrangement and diameter of the spinneret holes, are changed in order to make the process more stable. The recommendations for further study can be used to further examine some aspects of this work; however, this work presents a new concept for fine PEEK melt spinning supported by spinnability examinations under different spinning conditions and the improved model of fibre formation, which is also relevant for typical industrial processing applications.

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Les matières plastiques ont désormais envahi notre quotidien. Elles sont le symbole de la société de consommation, car elles sont considérées comme un matériau non noble : les consommateurs l'assimilent à un produit jetable après usage. N'étant pas dégradables, les plastiques représentent donc un réel danger pour l'environnement, la faune et la flore.L’objectif de ce travail de thèse a été de développer en collaboration avec l’Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (Université de Pau) de nouvelles formulations avec des additifs naturels pour obtenir des plastiques résistants et recyclables. Deux types de résines ont été utilisées : le polypropylène isotactique (i-PP) et le polyéthylène à basse densité (LDPE). Des antioxydants naturels tels que l’acide ascorbique, l’alpha-tocophérol et l’huile de lin ont été testés et leur encapsulation a permis d’améliorer leur résistance à la dégradation. Les caractérisations thermique et rhéologique des résines ont montré des qualités supérieures aux résines commerciales actuelles. Nous avons pu démontrer que les plastiques obtenus pouvaient être recyclés 9 fois sans perte de leurs caractéristiques. Des essais avec des barquettes fabriquées avec les produits élaborés sont en cours pour valider les modèles développés. / Plastics have now invaded our daily lives. They are the symbol of the consumer society, because they are considered a non-noble material: consumers equate it with a disposable product after use. Since plastics are not degradable, they represent a real danger to the environment, fauna and flora.The objective of this thesis work was to develop in collaboration with the Institute of Analytical Sciences and Physico-Chemistry for Environment and Materials (Pau University) new formulations with natural additives to produce resistant and recyclable plastics. Two types of resins were used: isotactic polypropylene (i-PP) and low density polyethylene (LDPE). Natural antioxidants such as ascorbic acid, alpha-tocopherol and flaxseed oil were tested and encapsulated to improve their resistance to degradation. Thermal and rheological characterizations of resins have shown superior qualities to current commercial resins. We were able to demonstrate that the plastics obtained could be recycled 9 times without losing their characteristics. Tests with trays made with the developed products are underway to validate the developed models.

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博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

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