Functional Transformations on the Surface of Poly(ethylene terephthalate) Films under Exposure to Accelerated Electrons

The effect of the electron-beam treatment of poly(ethylene terephthalate) (PETP) films in an air atmosphere on the functional chemical composition of their surface and on the optical properties in the UV region was studied. The mutual functional transformations of surface sites (carbonyl, methyl, and hydroxyl groups) by the action of fast electrons were analyzed as functions of the absorbed dose over the range 25–500 kGy using the adsorption of acid–base indicators with the pKa values ranging from –5 to 15. Correlation between the absorbed dose, the concentration of certain functional groups (centers with pKa 5.0 (–CH3) and 0.8 (–CH2OH)), the hydrophilicity of films, and the transparency in the UV region of the spectrum was established. The transparency was found to exhibit a pronounced minimum at an absorbed dose of 150–200 kGy. A comparative analysis of PETP surfaces differing by the absence or presence of kaolin (0.1%) as an oxide material additive was performed. Differences in the pKa distribution of adsorption sites were found, and their dependence on the absorbed dose was studied.