EFFECTS OF ULTRAVIOLET AND VACUUM ULTRAVIOLET-IRRADIATION ON FLUORINATED ETHYLENE PROPYLENE COPOLYMERS - AN ELECTRON-PARAMAGNETIC RESONANCE STUDY

Fluorinated ethylene propylene copolymer (FEP) samples were irradiated by an excimer laser source, KrF (249 nm), ArF (193 nm) or F2 laser (157 nm), and observed formations of two radical species; a terminal (I) or side chain radical (III), -CF2., and a main chain radical - CF2 - CF - CF2 - (II). Room temperature EPR spectrum of (I) and (III) showed a strong triplet structure with a hyperfine splitting of 16.7 G and the radical (II) showed a doublet of quintet structure with hyperfine splitting of a(alpha) = 42 G and a(beta) = 22 G. Observations of the same radical species were reported in the literature by gamma-ray or electron irradiation of polytetrafluoroethylene or FEP samples. It seems the same radicals are involved in the initial stages of degradation processes of fluorinated polymers by gamma-ray, electron, UV or VUV irradiations.