Determination of local mechanical stresses in irradiated polymers

Determined are the values of local mechanical stresses in irradiated polyethyleneterephthalate (PETP) and mechanically stressed segments in irradiated samples at the temperature of 200 deg C using infrared spectroscopy method. Infrared spectra showed, that the intensity of the long-wave absorption edge of the 975 cm-1 band appreciably decreases with temperature increasing. The calculations showed that segment concentration with the stresses of 4300 and 5700 Mn/m2 constitutes 5 and 10% respectively. The amount of stressed segments at 200 deg C is explained by thermofluctuated decay of overstressed segments and by supermolecular structure partial rebuilt of irradiated polymers. The conclusion was made, that in irradiated (PETP) samples internal stresses arise and their values depend on the irradiation doses. Under the influence of this stresses the dissociation energy of chemical bonds, included in molecular segments, is appreciably lowed and this is the reason for strength decreasing in irradiated samples