DSC and X-ray diffraction studies on the physicochemical changes occurring
in polyester films exposed to heavy ion irradiation
Polimery 1999, No 2, 123
Polyethylene terephthalate) (PET) (commercial biaxially oriented Mylar and Hostaphan, 23 and 19 µm thick) and poly(butylene terephthalate) (PBT) (80 µm thick) films were exposed to heavy ion irradiation and the resulting structural transformations were studied by differential scanning calorimetry (Perkin-Elmer DSC-7, heating rate in nitrogen flow, 2 or 3 K/min, open pans; heating-cooling-heating cycles run at rates of 10-10-10 K/min and 2-20-2 K/min, closed pans), wide-angle and small-angle X-ray scattering (WAXS, SAXS), Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and density measurements. The PBT film was prepared from the molten phase and then heated at 150°C. They were irradiated with Ar ions (5.5 MeV/amu, 1011 ions/cm2), Dy ions (13 MeV/amu, 1—5 · 1010 i 1011 ions/cm2), and Pb ions (11.4 MeV/amu, 1010 ions/cm2). The calculated radiation doses were found to be contained within the range of (1.1—22.0) · 105 Gy. The irradiation-effected different film melting and crystallization courses (Figs. 1, 2, 7) detected by DCS and the changes in reflection intensities in WAXS diffractograms (Figs. 4, 6) indicated to a reduced crystal phase content in the irradiated polyester films. The amorphization of the PET film was confirmed by SAXS (Fig. 3) and FTIR spectra (Fig. 5) and also by density measurements. As found by GPC, the molecular weight of the soluble fraction in PET decreases on irradiation and the accompanying increase in the content of the insoluble phase indicates that crosslinking processes occur. The DSC and X-ray techniques proved to be helpful in following the structural changes induced in polymer films by irradiation with heavy ions.
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