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 comprising tetrafluoroethylene unit, hexafluoropropylene unit, and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of hexafluoropropylene unit of 10.4 to 11.5% 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 7.0 to 9.9 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 90 or less per 10.sup.6 main-chain carbon atoms.

There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit, and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 4.10 to 5.20 mol % with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 0.53 to 0.86 mol % with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 0.7 to 2.5 g/10 min.

There is provided a copolymer containing tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 2.14 to 3.00 mol % with respect to the whole of the monomer units, a melt flow rate at 372° C. of 33.0 to 50.0 g/10 min, and the number of functional groups of 50 or less per 10.sup.6 main-chain carbon atoms.

There is provided a copolymer containing tetrafluoroethylene unit and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the perfluoro(propyl vinyl ether) unit of 4.1 to 4.9% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 33.0 to 45.0 g/10 min, and the number of functional groups 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 the hexafluoropropylene unit of 7.0 to 8.5% by mass with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 1.5 to 2.9% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 9 to 15 g/10 min.

There is provided a fluorine-containing copolymer comprising tetrafluoroethylene unit, hexafluoropropylene unit and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the hexafluoropropylene unit of 9.4 to 10.3% by mass with respect to the whole of the monomer units, a content of the perfluoro(propyl vinyl ether) unit of 0.8 to 1.6% by mass with respect to the whole of the monomer units, and a melt flow rate at 372° C. of 7.0 to 17.0 g/10 min.

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 7.0% by mass with respect to the whole of the monomer units, a content of the fluoro(alkyl vinyl ether) unit of 1.4 to 2.9% by mass with respect to the whole of the monomer units, a melt flow rate at 372° C. of 9 to 40 g/10 min, and the number of functional groups of 90 or less per 10.sup.6 main-chain carbon atoms.