Chemical conversion of a tetrafluorethylene-ethylene copolymer during radiolysis in vacuum

Abstract

IR spectroscopic studies of a tetrafluorethylene-ethylene (1:1) copolymer exposed to γ-radiation in vacuum revealed changes in chemical structure dependent on conditions of irradiation. With an increase in the dose of radiation a reduction occurs in absorption band intensities in the regions of 1450 and 2973 cm −1 corresponding to vibrations of CH 2 groups and in a series of absorption bands in the 500–1300 cm −1 region, corresponding to bond-stretching and deformation vibrations of CF bonds of CF 2 groups. These variations are intensified with an increase in the temperature of radiation from 25 to 250°. Different types of double bond are formed: −CH=CF−, −CF=CF−, −CH=CF 2 (bands at 1720, 1740, 1765 cm −1). Absorption band intensity varied in the region of 1740 cm −1 according to the dose and temperature of radiations. With an increased radiation dose (25°) band intensity at 1860 cm −1 related to “terminal unsaturation” of −CF=CF 2 increases. However, at an irradiation temperature of 250° this band disappears. At increased temperature of radiation (150, 250°) a broad absorption band is formed in the region of 1600–1700 cm −1, which is due to the formation of double bonds of the type −CH=CH 2 or −CH=CH−. Using results obtained a mechanism is proposed for breakdown and structure formation taking place during the irradiation of the copolymer.