FT-IR imaging and Raman microscopic study of poly(ethylene terephthalate) film processed with supercritical CO2

• Published in: Vibrational spectroscopy Vol. 35; no. 1-2; pp. 3 - 7
• Main Authors: Fleming, O.S, Chan, K.L.A, Kazarian, S.G
• Format: Journal Article
• Language: English
• Published: 17.06.2004
• ISSN: 0924-2031
• DOI: 10.1016/j.vibspec.2003.10.003

PET, a significant industrial polymer, may exist in three possible morphologies: amorphous, ordered amorphous, and the all-trans crystalline structure. The amorphous morphology has gauche glycol conformers and disordered terephthalate units, differing from the ordered amorphous structure which has a trans glycol fonformation with disordered terephthalate groups. Supercritical processing of PET provides the opportunity to induce morphological alterations (e.g. crystallinity) in an environmentally friendly manner. Poly(ethylene terephthalate) (PET) film was exposed to supercritical (sc) CO2 for a range of exposure times to induce morphological change. Transmission FT-IR imaging and Raman point mapping were applied to the microtomed film sections to determine the extent of the scCO2-induced morphological gradient. Confocal Raman microscopy (oil and dry objectives) was also used to elucidate the extent of the morphological gradient in a non-destructive manner. A region of semi-crystalline PET with a significant morphological gradient has been observed normal to the surface of the film at a maximum of 50 mum. The `tunable' nature of scCO2 processing as a function of exposure time has been demonstrated. This work confirms the suitability of the techniques to study the induced morphological changes in polymers processed with scCO2 and the reliability of the oil immersion objective used to generate confocal Raman depth profiles.