Study of the long term effect of high gamma doses in the crystalline phase of P(VdF-TrFE) copolymers

Differential Scanning Calorimetry (DSC) and X-ray diffraction (XRD) of gamma irradiated poly(vinylidene fluoride–trifluoroethylene) copolymer [P(VdF-TrFE)] have been studied in connection with the use of material in industrial high gamma dose measurement. Interaction between radiation and P(VdF-TrFE) results in a decrease of its crystallinity together with the simultaneous formation of CC conjugated bonds. It has been found that the melting latent heat (LMelt) of the crystallites is unambiguously related to the value of absorbed dose. The DSC technique can be used to evaluate high gamma doses ranging from 1.0 kGy to 1.0 MGy. The relation between LMelt and gamma doses can be fitted by an exponential function for measurements taken until 3 months after irradiation. After this time, the relation can be fitted by a linear function for periods at least of one year. X-ray diffraction revealed an expansion of the β-phase unit cell of 5% in the b direction for gamma doses between 250 and 500 kGy. The results presented highly increases the possibility of using the melting latent heat of P(VdF-TrFE) copolymer in high dose dosimetry.