One embodiment of the present invention relates to an elastomer composition, a sealing material, or a method for producing a sealing material, in which the elastomer composition includes a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, an ethylenically unsaturated bond-containing compound (B), a crosslinking agent (C), and a crosslinking aid (D), the ethylenically unsaturated bond-containing compound (B) contains at least one selected from compounds having a perfluoro skeleton having an ethylenically unsaturated bond and compounds having a siloxane skeleton having an ethylenically unsaturated bond, and a mass ratio of a content of the crosslinking aid (D) to the crosslinking agent (C) is 5 or more.

One embodiment of the present invention relates to an elastomer composition, a sealing material, or a method for producing a sealing material, in which the elastomer composition includes a crosslinkable fluoroelastomer (A1) that is other than a perfluoroelastomer and has a fluorine content of 69% by mass or more and a crosslinkable fluoroelastomer (A2) that is other than a perfluoroelastomer and has a fluorine content in a range of 55 to 68% by mass, and a content of the fluoroelastomer (A1) is 60 to 95% by mass based on 100% by mass of the total of the fluoroelastomers (A1) and (A2).

One embodiment of the present invention relates to an elastomer composition, a sealing material, or a method for producing a sealing material, in which the elastomer composition includes a crosslinkable fluoroelastomer (A1) that is other than a perfluoroelastomer and has a fluorine content of 69% by mass or more and a crosslinkable fluoroelastomer (A2) that is other than a perfluoroelastomer and has a fluorine content in a range of 66 to 68% by mass.

One embodiment of the present invention relates to a sealing material or a method for producing a sealing material, in which the sealing material is a radiation-crosslinked body of an elastomer composition including a crosslinkable fluoroelastomer (A) other than a perfluoroelastomer, a crosslinking agent, and a crosslinking aid, and the fluoroelastomer (A) contains a crosslinkable fluoroelastomer (A1) that is other than a perfluoroelastomer and has a fluorine content in a range of 66 to 68% by mass.

A copolymer containing a tetrafluoroethylene unit, and a perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of the perfluoro(propyl vinyl ether) unit of 3.4 to 3.9% by mass with respect to the whole of the monomer units, and a melt flow rate of 29 to 36 g/10 min, and the number of functional groups of —CF═CF.sub.2, —CF.sub.2H, —COF, —COOH, —COOCH.sub.3, —CONH.sub.2 and —CH.sub.2OH of more than 50 per 10.sup.6 main-chain carbon atoms. Also disclosed is a sealing tool, an injection molded article, a member to be compressed including the copolymer, and a coated electric wire including a coating layer containing the copolymer.

A sealing member containing 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 3.0 to 4.5% by mass with respect to the whole of the monomer units, a melt flow rate of 5 to 26 g/10 min, and the number of functional groups of —CF═CF.sub.2, —CF.sub.2H, —COF, —COOH, —COOCH.sub.3, —CONH.sub.2 and —CH.sub.2OH of more than 50 per 10.sup.6 main-chain carbon atoms, wherein the sealing member has a thickness of 0.5 to 2.5 mm. Also disclosed is a power storage assembly including the sealing member.

A sealing member containing 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 2.7 to 4.5% by mass with respect to the whole of the monomer units, a melt flow rate of 26 to 42 g/10 min, and the number of functional groups of —CF═CF.sub.2, —CF.sub.2H, —COF, —COOH, —COOCH.sub.3, —CONH.sub.2 and —CH.sub.2OH of more than 50 per 10.sup.6 main-chain carbon atoms. Also disclosed is a power storage assembly including the sealing member.

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 2.26 to 2.75 mol % with respect to the whole of the monomer units, a melt flow rate at 372° C. of 4.0 to 11.0 g/10 min, and the number of functional groups of 50 or less per 10.sup.6 main-chain carbon atoms.

Provided is a composition for a gas seal member that can form a gas seal member for a high-pressure hydrogen device that is capable of sufficiently inhibiting both swelling destruction and blister destruction. The composition for a gas seal member is a composition for a gas seal member used in a high-pressure hydrogen environment and contains an elastomer and fibrous carbon nanostructures. The fibrous carbon nanostructures are contained in a proportion of not less than 1 part by mass and not more than 10 parts by mass per 100 parts by mass of the elastomer. An area fraction S (%) of aggregates of the fibrous carbon nanostructures in a cross-section of the composition for a gas seal member and a volume percentage V (volume %) of the fibrous carbon nanostructures in the composition for a gas seal member satisfy a relationship 0≤S/V≤2.0.

Provided is a member to be compressed for an electrochemical device obtained by crosslinking a crosslinkable composition containing a fluorine-containing elastomer, wherein the fluorine-containing elastomer exhibits a difference δG′ (G′(100° C.)−G′(180° C.)) between the storage elastic modulus G′(100° C.) at a measurement temperature of 100° C. and the storage elastic modulus G′(180° C.) at a measurement temperature of 180° C., in the dynamic viscoelasticity test (strain amplitude: 0.5 Deg; frequency: 100 CPM) with a rubber process analyzer satisfying the following conditions:

40 kPa<δG′<175 kPa.