Fluoro-rubber composition and bladder for tire fabrication

A fluoro rubber composition comprising a rubber component comprising:

• a fluoro rubber;
• carbon black;
• and
• a vulcanization system compounding agent containing a co-crosslinking agent,
• wherein the fluoro rubber is at least one member selected among (A) a copolymer of tetrafluoroethylene/perfluoroalkyl vinyl ether, (B) a copolymer of tetrafluoroethylene/propylene, and (C) a copolymer made of (i) at least one monomer selected among tetrafluoroethylene, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, vinyl fluoride, perfluoroalkyl vinyl ether and propylene, and (ii) vinylidene fluoride;
• in a kneading step of compounding the carbon black in the rubber component, an average shear rate of a rotor tip point of a kneading machine is 100 (1/sec) or more, and a kneading maximum temperature Tm is 120° C. or higher and not higher than 200° C.;
• and
• in a dynamic viscoelasticity test of an unvulcanized rubber by a rubber process analyzer (RPA) (measurement temperature:
• 100° C., measurement frequency:
• 1 Hz), a difference δGA′ (G′(1%)−G′(100%)) between a shear modulus G′(1%) at the time of a dynamic strain of 1% and a shear modulus G′(100%) at the time of a dynamic strain of 100% is 120 kPa or more and not more than 3,000 kPa,
• wherein the elongation at break at 25° C. of the fluoro rubber composition after vulcanization is 400% or more and not more than 800%, and
• wherein a compounding amount of the co-crosslinking agent is 0.5 to 2.5 parts by mass based on 100 parts by mass of the rubber component.