Nuclear Magnetic Resonance Study of O-ring Polymer Exposed to High-Pressure Hydrogen

Magic angle spinning (MAS) nuclear magnetic resonance (NMR) for F-19 and H-1 nuclei was used how exposure to high-pressure (70 Wifa) H-2 gas affected an O-ring material. F-19 MAS NMR revealed that poly(vinylidenefluoride-co-hexafluoroprophylene) in VDF/HFP = 76.1/23.9 mol % (FKM type 1) was involved in the O-ring material. This copolymer may undergo main-chain scission and termination to -CF2H end groups during depressurization of high-pressure H-2. Evidence for formation of additional -CF2H end group includes a small increase in the F-19 MAS NMR signal at -96 ppm, and a corresponding H-1 MAS NMR signal at 7.1 ppm in comparison with those in the material that had not been exposed to high-pressure H-2. Neither the F-19 nor the H-1 MAS NMR showed chemical shift after exposure to H-2; this absence of response means that exposure to H-2 did not affect the structure of the polymer.