A method for producing an aqueous dispersion of a fluorine-containing elastomer, including polymerizing a fluorine-containing monomer in the presence of a compound (1) having an aromatic ring, a hydrophilic group, and an unsaturated double bond, and an aqueous medium, to produce an aqueous dispersion of a fluorine-containing elastomer containing -CH.sub.2- in a main chain.

Provided is a binder for a battery, including a fluorine-containing copolymer, wherein the fluorine-containing copolymer comprises a repeating unit (a) based on vinylidene fluoride and at least one repeating unit (b) selected from the group consisting of a repeating unit (bl) represented by a specific structural formula (bl) and a repeating unit (b2) represented by a structural formula (b2), and the fluorine-containing copolymer has a molar ratio of the repeating unit (a) to the repeating unit (b), (a)/(b), of 95/5 to 5/95.

Provided is a binder for a battery, including a fluorine-containing copolymer, wherein the fluorine-containing copolymer comprises a repeating unit (a) based on vinylidene fluoride and at least one repeating unit (b) selected from the group consisting of a repeating unit (bl) represented by a specific structural formula (bl) and a repeating unit (b2) represented by a structural formula (b2), and the fluorine-containing copolymer has a molar ratio of the repeating unit (a) to the repeating unit (b), (a)/(b), of 95/5 to 5/95.

A fluororesin having a reactive functional group, wherein the difference between the loss elastic modulus at 270° C. of the fluororesin (G″.sub.270) and the loss elastic modulus at 280° C. of the fluororesin (G″.sub.280) (G″.sub.270-G″.sub.280) is 2,500 Pa or more. Also disclosed is a fluororesin layer containing the fluororesin; and a non-fluororesin layer containing a non-fluororesin.

A fluororesin having a reactive functional group, wherein the difference between the loss elastic modulus at 270° C. of the fluororesin (G″.sub.270) and the loss elastic modulus at 280° C. of the fluororesin (G″.sub.280) (G″.sub.270-G″.sub.280) is 2,500 Pa or more. Also disclosed is a fluororesin layer containing the fluororesin; and a non-fluororesin layer containing a non-fluororesin.

An electrocaloric element for a heat transfer system includes an electrocaloric material of a copolymer of (i) vinylidene fluoride, and (ii) an addition polymerization monomer that is larger than vinylidene fluoride and includes a substituent more electronegative than chlorine. Electrodes are disposed on opposite surfaces of the electrocaloric material, and an electric power source is configured to provide voltage to the electrodes. The system also includes a first thermal flow path between the electrocaloric material and a heat sink, and a second thermal flow path between the electrocaloric material and a heat source.

An electrocaloric element for a heat transfer system includes an electrocaloric material of a copolymer of (i) vinylidene fluoride, and (ii) an addition polymerization monomer that is larger than vinylidene fluoride and includes a substituent more electronegative than chlorine. Electrodes are disposed on opposite surfaces of the electrocaloric material, and an electric power source is configured to provide voltage to the electrodes. The system also includes a first thermal flow path between the electrocaloric material and a heat sink, and a second thermal flow path between the electrocaloric material and a heat source.

The present invention aims to provide a method of producing a fluoropolymer, especially a fluoropolymer essentially including a tetrafluoroethylene or chlorotrifluoroethylene unit, at a higher polymerization rate with improved efficiency, the method being capable of improving the moldability in extrusion molding and suppressing discoloration. The method of producing a fluoropolymer of the present invention includes producing a fluoropolymer by polymerizing tetrafluoroethylene or chlorotrifluoroethylene in the presence of a peroxydicarbonate. The peroxydicarbonate is represented by the formula:
R—O—C(═O)—O—O—C(═O)—O—R
wherein R's may be the same as or different from each other and individually represent a C4 alkyl group or alkoxy alkyl group.

The present invention aims to provide a method of producing a fluoropolymer, especially a fluoropolymer essentially including a tetrafluoroethylene or chlorotrifluoroethylene unit, at a higher polymerization rate with improved efficiency, the method being capable of improving the moldability in extrusion molding and suppressing discoloration. The method of producing a fluoropolymer of the present invention includes producing a fluoropolymer by polymerizing tetrafluoroethylene or chlorotrifluoroethylene in the presence of a peroxydicarbonate. The peroxydicarbonate is represented by the formula:
R—O—C(═O)—O—O—C(═O)—O—R
wherein R's may be the same as or different from each other and individually represent a C4 alkyl group or alkoxy alkyl group.

Provided is a fluoroelastomer crosslinkable composition, containing a polyol-crosslinkable fluoroelastomer (a) and a cross-linking agent (b), wherein the cross-linking agent (b) is at least one selected from the group consisting of a compound represented by the general formula (b) set forth in the description and a salt of the compound with an alkali metal, an alkaline earth metal, or an onium compound.