Microstructural modifications in swift ion irradiated PET

Polyethylene terephthalte (PET) was irradiated with carbon (70 MeV) and copper (120 MeV) ions to analyze the induced modifications with respect to optical, structural and thermal properties. In the present investigation, the fluence for carbon irradiation was varied from 1×1011 to 1×1014 ions cm−2, while that for copper beam was kept in the range of 1×1011 to 1×1013 ions cm−2. UV–vis, FTIR, XRD and DSC techniques were utilized to study the induced changes. The analysis of UV–vis absorption studies reveals that there is decrease of optical energy gap up to 10% on carbon ion irradiation (at 1×1014 ions cm−2), whereas the copper beam (at 1×1013 ions cm−2) leads to a decrease of 49%. FTIR analysis indicated the formation of alkyne end groups along with the overall degradation of polymer with copper ion irradiation. X-ray diffraction analysis revealed that the semi-crystalline PET losses its crystallinity on swift ion irradiation. It was found that the carbon beam (1×1014 ions cm−2) decreased the crystallite size by 16% whereas this decrease is of 12% in case of the copper ion irradiated PET at 1×1013 ions cm−2. The loss in crystallinity on irradiation has been supported by DSC thermograms.