Ion induced chemical modifications of polyethylene terephthalate (PET) were studied by Fourier-transform infrared spectroscopy The irradiations with Kr (86 MeV/u) and with Mo (56 MeV/u) ions were performed under vacuum and in oxygen atmosphere, respectively The overall degradation of the polymer was investigated as a function of the ion fluence in the range from 1 × 1011to 6 × 1012 ions/cm2 A significant loss of crystallinity is related to scission processes of the main chains at the ethylene glycol residue The benzene ring structures show only small changes under irradiation and do not seem to participate in the degradation process significantly While various degradation processes known from photochemical degradation take place, the creation of alkynes near the track core is found to be a unique process induced by heavy ions The presence of oxygen during irradiation enhances the overall degradation of PET and leads to enhanced formation of alkynes and CO2

Chemical modifications of PET induced by swift heavy ions

Effects of gamma irradiation at different doses up to 135 kGy on polyethylene terephthalate (PET) polymer films have been investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-VIS) spectroscopy. From XRD analysis, it was found that even at a high dose of gamma irradiation of 135 kGy, crystallinity of the PET samples remain unchanged. However, the FTIR peak at 871 cm−1 (depicting C–H bending mode of out-of-plane vibration) and another at 1303 cm−1 (representing C–H bending mode of in-plane vibration) disappear for gamma-irradiated PET. In this study, it has also been found that γ-irradiation in air enhances the optical absorption in the wavelength region 320–370 nm. This has been attributed to free radicals being produced in the polymer by the γ-radiation. Further, the free radicals react with oxygen of air to form carbonyl group and hydroxyls. With increasing γ-dose, there is a red shift of the UV—near visible cutoff for PET. XRD and FTIR observations on γ-damage have been correlated.

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Structural and Optical Investigations of Radiation Damage in Transparent PET Polymer Films

Degradation processes in various polymers (polycarbonate, poly(ethyleneterephthalate), polyimide, and polysulfone) induced by krypton and molybdenum ions of several hundred MeV were studied by infrared and mass spectroscopy. A wide spectrum of degradation products well known from low ionizing radiation were found, which are strongly enhanced if the irradiation takes place in oxygen atmosphere. Most notables are the formation of triple bonded species such as alkynes, cyanates and acetylene. They are created within a radius of about 3–4 nm around the ion trajectory. The complementing observation of degradation products in the bulk polymer and as volatile fragments allows a detailed description of the underlying decomposition mechanisms. The observation of degradation products in close analogy to pyrolysis and the thermal stability of acetylene, strongly suggest that transient temperatures above 1500 K are involved in the track formation process.

Pyrolytic effects induced by energetic ions in polymers

In materials which are sensitive to radiolysis such as ionic crystals and polymers, energetic heavy ions (MeV–GeV) create cylindrical tracks with a complex damage structures consisting of a small core region surrounded by a much larger halo. In the track core, specific defects such as the formation of triple bonds in polymers or defect clusters in alkali halides are observed. They are linked to the extremely high energy density of heavy ions, whereas modifications in the halo are similar to effects induced by conventional radiation. Using different complementing techniques such as absorption spectroscopy, small-angle X-ray scattering and chemical etching, a detailed description of the core and halo defects is presented.

M. Bravar

Papers

Correlation of physico-chemical, mechanical and electrical properties of ultraviolet-degraded poly(ethylene terephthalate)

The effects of photo-degradation on the electrical properties of poly(ethylene terephthalate)