Dielectric Properties of γ-Ray Irradiated Poly(vinylidene Fluoride)

The dielectric properties of γ-ray irradiated poly(vinylidene fluoride) (PVDF) were studied at temperatures from 213 to 423 K. The relaxation intensity, Δε, of both the β and α relaxations decreased with increasing irradiation dosages. The decrease of Δε in the β and α relaxations was ascribed to an increase in crosslinking in the amorphous regions and at lamellar surfaces, respectively. When irradiated PVDF was crystallized from the melt under uniaxial compression, Δε of the β relaxation increased with increasing compression ratio, while that of the α relaxation decreased. The increase of Δε in the β relaxation is explained by the increase of molecular chains oriented parallel to the film plane. The decrease of Δε in the α relaxation is due to conversion of form II crystal into form I.