Free volume study of 70 MeV carbon induced modification in polymers through positron annihilation

Free volume properties of polymers have strong correlation with macroscopic properties and can be modified by radiations and ions. Positron annihilation lifetime spectroscopy (PALS) provide direct information about the dimension, content and size distribution of free volume holes in polymers. CR-39 (DOP), a polycarbonate widely used as ion track detector and polyamide Nylon-6, a high performance plastic having a unique combination of superior mechanical, electrical, chemical and thermal properties were irradiated with 70 MeV C5+ ion beam to different fluences ranging from 1011 to 3.7 × 1013 ions/cm2. The results of characterization by PALS are reported here. o-Ps lifetime and the average free volume for both the polymers are found to decrease with fluence, indicating the facilitation of cross-linking. The results are interpreted in terms of change in the free volume. Maximum change of 9.7% in average free volume was observed in PN-6 irradiated to 3.7 × 1013 ions/cm2.