Measurement of high disorder state of high-density polyethylene (HDPE) on irradiation by gamma rays

High-density polyethylene (HDPE) is irradiated to moderate gamma doses 10, 20, 30, 40 and 50 kGy to carry out the study of change in its states. It is conducted by measuring resistivity and capacitance due to scissoring of chains; hence, immergence of various functional groups in the bulk of samples is irradiated to three doses 10, 30 and 40 kGy. Enhanced resistivity is found to follow sequential change as ρ10kGy > ρ30kGy > ρ40kGy > ρpris. Fractional change of resistivity, (ρ − ρ0)/ρ0, at small frequencies is correlated with fractional change of volume which is measured using the positron annihilation lifetime spectroscopy to estimate index of disorder, X. Disorder index, X, is the highest in the case of sample irradiated to 10 kGy gamma dose. Electrical capacitance, C, measured across the bulk of HDPE is found maximum in the case of 10 kGy dose, while samples irradiated to 30 and 40 kGy show capacitance smaller than the pristine HDPE indicating different dielectric behavior. Similarly, dissipation factor is found to be the smallest in the case of 10 kGy than 30 and 40 kGy doses up to several thousands of frequency in Hz. In all cases, electrical capacitance is found to be sustainable at high frequencies in the pristine as well as samples irradiated to the 10, 30 and 40 kGy doses.