GAMMA-RADIATION INDUCED STRUCTURAL-CHANGE S IN PVDF AND PVDF-TFE COPOLYMER

The structure of polyvinylidenefluoride (PVDF) and its copolymer with tetrafluoroethylene (TFE) exposed to various doses of gamma-radiation in air was studied by X-ray diffraction analysis. The irradiation of i sotropic PVDF samples containing crystalline alpha-modification is acc ompanied by redistribution of the diffraction intensity between some i nter- and intramolecular reflections. This is related to a partial tra nsformation of the alpha phase into its polar modification under the a ction of local fields of a space charge produced by gamma-quanta in th e polymer matrix. In the isotropic copolymer samples with coexisting n onequilibrium para- and ferroelectric phases, the irradiation leads to a radiation-induced transition of the paraelectric to ferroelectric t ype. In the uniaxially drawn copolymer samples containing both isotrop ic and anisotropic (mesomorphic) components of the paraelectric phase, the irradiation may result in increasing longitudinal dimensions of t he ferroelectric crystallites.