Increasing scrutiny over industrial activity has driven the search for environmentally friendly processing alternatives. Supercritical (sc) CO2 functions as a transient plasticiser in polymer processing applications and offers intrinsic advantages. Exploiting the potential benefits provided by CO2 requires a detailed understanding of the implications of CO2 exposure to polymeric material. This thesis describes the use of the confocal Raman microscopy (CRM) and FTIR imaging to characterise polymers processed with scCOz. The processing of semicrystalline polymers is a complex process due to possible CO2-induced morphological alterations to the matrix. The development of an experimentalapproach for studying semicrystalline polymers processed with scCO2 via CRM, Ramanmapping and FTIR imaging is described. A significant gradient in the degree of crystallinity normal to the surface of poly(ethylene terephthalate) (PET) film has been observed non-destructively with CRM and confirmed by a complementary analysis of microtomed film sections via Raman mapping and transmission FTIR imaging. A model system of PET film impregnated with Disperse Red I (ORI) from a scCO2 solution was developed and a one-dimensional Fickian diffusion model was used to evaluate the diffusion coefficient of the dye as a function of pressure and temperature. This approach has been extended to investigate other scCO2 processed polymer systems including PET fibres, syndiotactic polystyrene impregnated with DRl and a biocompatible polymer impregnated with a model drug. The interdiffusion of polyvinylpyrrolidone and poly( ethylene glycol) subjected to scCO2 was studied using a novel application of in situ attenuated total reflection (ATR) FTIR imaging. Visualisation of the dynamic miscible polymer system was achieved and the influence of pressure and molecular weight elucidated, revealing the ability to control the rate of the dynamic process. The feasibility to apply in situ A TR FTIR imaging to study CO2-induced alterations in PET and CO2-induced polymer phase separation is explored.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:428533 |
| Date | January 2006 |
| Creators | Fleming, Oliver Stuart |
| Contributors | Kazarian, Sergei G. ; Higgins, Julia |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/65000 |
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