Gamma irradiation of fluorocarbon polymers

Abstract

Several ~uorocarbon polym~rs ~ere irradiated with Co60 gamma radiation at doses up to 10 22 ev/g. ~he polymers studIed Included polytetrafiuoroethylene, polytrifiuoroethylene, polychlorotrIfiuoroethy.len~, a copoly.mer of tetrafiuoroethylene with hexafiuoropropylene, and several rubbery vInylIdene fiuorIde copolymers. G-values were measured for volatile p~oducts, for free radica.ls ~etected by electron spin reso~ance, and, in the case of polychlorotrIfiuoroethylene, for SClSSIOns. The course of degradatIOn or crosslinking was followed by zero-strength-time .and tensile-strength measurements. It was found that for poly tetrafiuoroethylene and Its hexafiuoropropylene copolymer the presence of air-accelerated scission drastically. The mechanism of the radiation-induced changes is discussed in terms of freeradical intermediates.

Degradation of γ-irradiated linear perfluoroalkanes at high dosage

“…The presence of fluoroalkenes is confirmed by characteristic lines in the UV spectra of irradiated perfluoroalkanes [18,21]. About 100 eV of absorbed radiation energy is required to break two molecules of liquid (n-E 6 F 14 , n-E 8 F 18 ) or solid (n-E 12 F 26 , n-E 16 F 34 ) perfluoroalkanes during radiolysis up to a dose of 50 Mrad at 27 8C [20]. Increasing the perfluoroalkane chain length from C6 to C16 does not affect the products of radiolysis for smaller perfluoroalkanes such as CF 4 , C 2 F 6 , C 3 F 8 , n-C 4 F 10 , n-C 5 F 12 , and n-C nÀ2 F 2(nÀ2)+2 up to n = 16; c-C 3 F 6 ; and perfluoroalkenes with internal double bonds such as C 5 F 10 and CF 3 CF = CFCF 3 or with terminal double bonds such as C 2 F 4 , C 3 F 6 , and F 2 C = CFC 2 F 5 .…”

“…The low-molecular weight products (EF 4 , E 2 F 6 , E 3 F 8 ) from the radiolysis of PTFE [19] are formed in only low yield (G = 0.3) [20]. The main radiolysis products of perfluoroalkanes are smaller linear perfluoroalkanes of various chain lengths.…”

Evaluation of vinylidene fluoride polymers for use in space environments: Comparison of radiation sensitivities

“…Fully fluorinated (perfluorinated) polymers such as poly(tetrafluoroethylene) (PTFE) (Florin and Wall, 1961), poly(tetrafluoroethylene-coperfluoropropylene) (FEP) (Hill et al, 2003), and poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (Dargaville et al, 2003a), experience dramatic degradation and loss in tensile properties even after low radiation doses in vacuum due to the almost exclusive chain scission reactions. The mechanism is believed to involve scission of C-F bonds, generating highly reactive F d radicals, which then cleave C-C bonds, producing saturated end groups and terminal double bonds (Forsythe and Hill, 2000).…”

Characterization, performance and optimization of PVDF as a piezoelectric film for advanced space mirror concepts.

“…Fully fluorinated (perfluorinated) polymers, such as poly(tetrafluoroethylene) (PTFE) [80], experience dramatic degradation and loss in tensile properties even after relatively low (<20 kGy) radiation doses in vacuum due to almost exclusive chain scission reactions. The mechanism is believed to involve scission of C-F bonds, generating highly reactive F • radicals which then cleave C-C bonds producing saturated end groups and terminal double bonds [62].…”