Co-cured blends of fluoroelastomers of tetrafluoroethylene-propylene copolymer with cure site monomer and terpolymers of Vinylidene fluoride (VDF), Hexafluoropropylene (HFP) and Tetrafluoroethylene (TFE) with peroxide as initiator and coagent TAIC as crosslinker show improved curing performance, improved mechanical properties and improved compression set as well. The co-cured fluoroelastomers show improved chemical resistance to the solvent aging systems and better retention of mechanical properties after aging at high temperature in the solvents system.

Co-cured blends of fluoroelastomers of tetrafluoroethylene-propylene copolymer with cure site monomer and terpolymers of Vinylidene fluoride (VDF), Hexafluoropropylene (HFP) and Tetrafluoroethylene (TFE) with peroxide as initiator and coagent TAIC as crosslinker show improved curing performance, improved mechanical properties and improved compression set as well. The co-cured fluoroelastomers show improved chemical resistance to the solvent aging systems and better retention of mechanical properties after aging at high temperature in the solvents system.

Co-cured blends of fluoroelastomers of tetrafluoroethylene-propylene copolymer with cure site monomer and terpolymers of Vinylidene fluoride (VDF), Hexafluoropropylene (HFP) and Tetrafluoroethylene (TFE) with peroxide as initiator and coagent TAIC as crosslinker show improved curing performance, improved mechanical properties and improved compression set as well. The co-cured fluoroelastomers show improved chemical resistance to the solvent aging systems and better retention of mechanical properties after aging at high temperature in the solvents system.

The invention relates to a method of polymerizing at least one monomer comprising a vinylidene fluoride monomer, the method comprising putting in contact the at least one monomer with a polymerization initiator -and an oxidizing agent, the polymerization initiator having the formula (I):

##STR00001##

wherein R.sub.f is a fluoroalkyl group comprising from 1 to 3 carbon atoms; and M.sup.x+ is chosen from a monovalent cation, or a divalent cation, or a trivalent cation, or a tetravalent cation.

The invention relates to a method of polymerizing at least one monomer comprising a vinylidene fluoride monomer, the method comprising putting in contact the at least one monomer with a polymerization initiator -and an oxidizing agent, the polymerization initiator having the formula (I):

##STR00001##

wherein R.sub.f is a fluoroalkyl group comprising from 1 to 3 carbon atoms; and M.sup.x+ is chosen from a monovalent cation, or a divalent cation, or a trivalent cation, or a tetravalent cation.

A fluororesin having a tensile strength retention ratio of 50% or more, the tensile strength retention ratio being calculated by the following formula from the tensile strength of the fluororesin after a heat treatment obtained by conducting a heat treatment at 130° C. for 40,000 hours, and the tensile strength of the fluororesin before the heat treatment. Tensile strength retention ratio (%)=(tensile strength of fluororesin after heat treatment (MPa))/(tensile strength of fluororesin before heat treatment (MPa))×100.

A fluororesin having a tensile strength retention ratio of 50% or more, the tensile strength retention ratio being calculated by the following formula from the tensile strength of the fluororesin after a heat treatment obtained by conducting a heat treatment at 130° C. for 40,000 hours, and the tensile strength of the fluororesin before the heat treatment. Tensile strength retention ratio (%)=(tensile strength of fluororesin after heat treatment (MPa))/(tensile strength of fluororesin before heat treatment (MPa))×100.

A partially-fluorinated resin having a storage elastic modulus G′ of 0.1 Pa or more at a measurement temperature of 230° C. and an angular frequency of 0.0025 rad/second in dynamic viscoelasticity measurement. Also disclosed is a laminate including a partially-fluorinated resin layer containing the partially-fluorinated resin and a non-fluororesin layer containing a non-fluororesin.

A partially-fluorinated resin having a storage elastic modulus G′ of 0.1 Pa or more at a measurement temperature of 230° C. and an angular frequency of 0.0025 rad/second in dynamic viscoelasticity measurement. Also disclosed is a laminate including a partially-fluorinated resin layer containing the partially-fluorinated resin and a non-fluororesin layer containing a non-fluororesin.

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.