Abstract: Pure perfluoro(propylvinylether) is obtained by extractive distillation of crude perfluoro(propylvinylether) containing a hydrogen fluoride adduct of perfluoro(propylvinylether), which is obtained by gas phase or liquid phase thermal decomposition of perfluoro(2-propoxypropionyl)fluoride, in the presence of a ketone having a boiling point of 100.degree. C. of higher.

Abstract: A fluorine-containing elastomer capable of giving a primary vulcanization product with a good permanent set through peroxide vulcanization is produced by homopolymerization or copolymerization of a fluorine-containing olefin having 2 to 8 carbon atoms in the presence of an iodine and bromine-containing compound represented by the general formula RBrnIm, wherein R represents a fluorohydrocarbon group, a chlorofluorohydrocarbon group, a chlorohydrocarbon group or a hydrocarbon group, and n and m each are integers of 1 and 2, and a small amount of perfluoro(vinylether) compound having a general formula of CF.sub.2 .dbd.CFO[CF.sub.2 CF(CF.sub.3)O]m(CF.sub.2)nX, wherein X is a bromine atom or an iodine atom and m and n each are 1, 2 or 3.

Abstract: A novel perfluoropolyether containing 0.1 to 10% by weight of halogen atoms as bonded in the molecule is obtained by reacting tetrafluoroethylene with oxygen in a fluorinated solvent or a chlorofluorinated solvent under ultraviolet irradiation in the presence of a halogenated hydrocarbon chain transfer agent having a chain transfer coefficient with respect to methyl methacrylate of at least 5.times.10.sup.-4.

Abstract: A novel perfluoropolyether containing 0.1 to 10% by weight of halogen atoms as bonded in the molecule is obtained by reacting tetrafluoroethylene with oxygen in a fluorinated solvent or a chlorofluorinated solvent under ultraviolet irradiation in the presence of a halogenated hydrocarbon chain transfer agent having a chain transfer coefficient with respect to methyl methacrylate of at least 5.times.10.sup.-5.