Induced ordering in polyethylene terephthalate films irradiated with Ar ions with an energy of 70 MeV

Abstract

This work presents the results of a study of structural changes in latent tracks in a polymer film irradiated with heavy Ar8+ ions with fluxes of 2 × 1010, 5 × 1011 ions/cm2, and 1 × 1012 ions/cm2. Samples of polyethylene terephthalate (PET) polymer films with amorphous and crystalline parts, with initial weight fractions of 57% and 43% respectively, were used. The study of changes in structural characteristics was carried out using the method of X-ray diffraction analysis in the Bragg-Brentano 2π geometry with azimuthal steps of 10°, where the initial position was aligned with the direction of the texture. It was found that the amorphous part of the irradiated samples shows the formation of an anisotropic φ diffraction reflection, that increases with increasing irradiation flux, due to induced crystallisation of the PET material in the amorphous zone along the direction of the film texture. From measurements of the ratio of the intensities of two diffraction peaks (−110) and (100) in the crystalline part, it was found that an increase in irradiation flux causes a decrease in the degree of initial texturing. This correlated behaviour of the amorphous and crystalline parts of PET can be explained by the transfer of stresses from the amorphous to the crystalline zones by covalent bonds acting along the PET molecular backbone. Annealing of irradiated samples leads to the dissipation of newly formed coherent scattering areas in the amorphous part and the partial restoration of peak intensity (100) in the crystalline part, indicating the elastic nature of deformation of the polymer structure.