There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit, and a fluoro(alkyl vinyl ether) unit, wherein the copolymer has a content of hexafluoropropylene unit of 11.5 to 12.5% by mass with respect to the whole of the monomer units, a content of the fluoro(alkyl vinyl ether) unit of 0 to 0.5% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 0.8 to 4.0 g/10 min, and a total number of —CF.sub.2H, carbonyl group-containing terminal groups, —CF═CF.sub.2 and —CH.sub.2OH of 50 or less per 10.sup.6 main-chain carbon atoms.

There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit, and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of hexafluoropropylene unit of 9.5 to 11.4% by mass with respect to the whole of the monomer units, a content of perfluoro(propyl vinyl ether) unit of 0.5 to 1.6% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 4.1 to 6.9 g/10 min, and a total number of carbonyl group-containing terminal groups and —CF═CF.sub.2 and —CH.sub.2OH of 90 or less per 10.sup.6 main-chain carbon atoms.

There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 9.6 to 10.5% by mass with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 1.2 to 1.6% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 17.0 to 40.0 g/10 min.

There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit, and perfluoro(propyl vinyl ether) unit, wherein the content of hexafluoropropylene unit is 7.6 to 10.3% by mass with respect to the whole of the monomer units; the content of perfluoro(propyl vinyl ether) unit is 1.3 to 2.4% by mass with respect to the whole of the monomer units; and the melt flow rate at 372° C. is 4.5 to 9.5 g/10 min.

Described herein is method of making branched perfluorinated compounds, specifically (CF.sub.3).sub.2CFCF(CF.sub.3)OCF(CF.sub.3)C(═O)F and (CF.sub.3).sub.2CFCF(CF.sub.3)OCF═CF.sub.2. Also disclosed herein is a fluoropolymer derived from the branched perfluorovinyl ether monomer and methods of making the fluoropolymer.

To provide a fluorinated copolymer excellent in low temperature properties and crosslinking property as a fluororubber, and a method for producing it.

A fluorinated copolymer which has units based on tetrafluoroethylene, units based on propylene and units based on a compound represented by the following formula 1, and which has either one or both of iodine atoms and bromine atoms:

CF.sub.2═CFO(R.sup.f1O).sub.nR.sup.f2  formula 1

wherein R.sup.f1 is a C.sub.1-3 perfluoroalkylene group, R.sup.f2 is a C.sub.1-6 perfluoroalkyl group, n is an integer of from 1 to 4, and in a case where n is from 2 to 4, a plurality of R.sup.f1 may be the same or different.

There is provided a fluorine-containing copolymer containing tetrafluoroethylene unit, hexafluoropropylene unit and a fluoro(alkyl vinyl ether) unit, wherein the copolymer has a content of hexafluoropropylene unit of 5.0 to 7.5% by mass with respect to the whole of the monomer units, a content of the fluoro(alkyl vinyl ether) unit of 0.8 to 2.9% by mass with respect to the whole of the monomer units, a melt flow rate at 372 C. of 0.7 to 9.5 g/10 min, and the number of functional groups of 90 or less per 10.sup.6 main-chain carbon atoms.

Curable fluoropolymer containing repeating units derived from VDF and TFE and at least one other fluorinated comonomer and further containing CF.sub.2CH.sub.2I end groups and branching sites derived from one or more perfluorinated bisolefinic ether(s) used as modifier(s), wherein the one or more perfluorinated bisolefinic ether(s) used as modifier(s) correspond to the general formula: CF.sub.2CF(CF.sub.2).sub.nO(R.sub.1)O(CF.sub.2).sub.mCFCF.sub.2 wherein n and m are independent from each other either 1 or 0 and wherein R.sub.1 represents a perfluorinated linear or branched, cyclic or acyclic aliphatic or aromatic hydrocarbon residue that may be interrupted by one or more oxygen atoms and comprises up to 30 carbon atoms. Further provided are methods of making the curable fluoropolymers and for making an article containing the curable polymers.

The invention provides novel pellets having high fluidity in a hopper of an extruder and capable of forming a coating layer having good wire diameter stability and capacitance stability even when used for rapid molding of electric wire coating. The pellets contain a fluororesin. Each of the pellets, placed on a horizontal surface, has a substantially circular outline or a substantially elliptic outline and has a major axis D.sub.1 of 3.1 mm or shorter and a minor axis D.sub.2 of 3.1 mm or shorter when observed in the direction normal to the horizontal surface. Each pellet satisfies the following formula (1): (D.sub.1+D.sub.2)/2L=1.8 to 2.6, wherein D.sub.1 represents the major axis, D.sub.2 represents the minor axis, and L represents the height from the horizontal surface to the highest point of the pellet.

To provide a fluorinated elastic copolymer excellent in adhesion, processability, mechanical properties, heat resistance and chemical resistance.

A fluorinated elastic copolymer having units based on a monomer (a), units based on a monomer (b) and optionally units based on a monomer (c), which has an iodine atom bonded to a terminal of a molecular chain and the unit based on the monomer (b) adjacent to the iodine atom, and which has a proportion of the units based on the monomer (b) of from 0.09 to 2.0 mol % to all units. Monomer (a): monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, chlorotrifluoroethylene, a perfluoro(alkyl vinyl ether) and 2,3,3,3-tetrafluoropropene; monomer (b): a monomer having at least one type of functional group selected from the group consisting of an epoxy group, a hydroxy group, a carbonyl group-containing group and an isocyanate group; monomer (c): a monomer selected from the group consisting of ethylene and propylene.