1,1-Difluoroethene, 1-((trifluoroethenyl)oxy)heptafluoropropane, tetrafluoroethene polymer 74499-68-6 Propane, 1,1,1,2,2,3,3-heptafluoro-3-((trifluoroethenyl)oxy)-, polymer with 1,1-difluoroethene and tetrafluoroethene