Thermal analysis for study of the gamma radiation effects in poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) has attracted interest in the technology and industrial sectors, due to its mechanical and electrical properties, its resistance to weathering and its thermostability. It is well known that polymer properties change after irradiation. Thermal degradation studies after irradiation of the polymers play an important role in establishing the threshold temperature for breakdown and information about the molecular and crystalline structure. A systematic study of the effects of gamma irradiation on PVDF using DSC, TG, DTA, FTIR and XRD techniques has been conducted. The samples were irradiated with a Co-60 source at constant dose rate (12.0 kGy/h), with doses ranging from 100 kGy to 3000 kGy. The DSC data reveals a decrease in the melting temperature and melting latent heat for increasing doses. There is a remarkable decrease in the melting latent heat ranging from 46 J/kg (pristine sample) to 26 J/kg (3000 kGy). The data analysis suggests that the decrease observed in the onset decomposition temperature is due to the radio-induction of C=C bonds in the crosslinking process and that the increase of the residual amount is due to the radio-induction of C=O bonds, via chain scission.