Decomposition of fluoroelastomer: Poly(vinylidene fluoride-ter-hexafluoropropylene-ter-tetrafluoroethylene) terpolymer in subcritical water

Decomposition of poly(vinylidene fluoride-ter-hexafluoropropylene-ter-tetrafluoroethylene) ter-polymer, a typical fluoroelastomer with high flexibility and high resistance to permeation of oil and excellent adhesive ability to other materials, in subcritical water (SubCW) was studied as a first example of the decomposition of the terpolymer with the aim of developing a technique to recover the fluorine element. Compared to the common fluoropolymers such as poly(vinylidene fluoride), the terpolymer was considerably stable in SubCW. F-19 NMR spectral analysis of the decomposition products obtained from the reaction at 300 degrees C was carried out to better understand the decomposition mechanism. When the reaction was performed in SubCW at 300 degrees C for 6 h under argon, only a negligible amount of F- ions (1%) was released. Addition of H2O2 into the reaction system accelerated the mineralization of the terpolymer to form F- and CO2. Apart from these major products, small amounts of malonic acid and CF3H were detected. When this polymer was heated in SubCW at 350 degrees C with 4.0 M H2O2, both the yields of F- and CO2 reached up to 95%. These features indicate a quasi-complete mineralization of the terpolymer. Furthermore, the reaction in the presence of 4.0 M H2O2 and stoichiometric amount of Ca(OH)(2) at 350 degrees C for 18 h resulted in the formation of pure CaF2, a raw material for hydrofluoric acid, in 84% yield.