Fluoroelastomers

Curable fluoroelastomers comprising units derived from the following monomers:

• a) vinyl fluoride (VF), trifluoroethylene, perfluoroalkylethylenes CH2═CH—R2f wherein R2f is a C1-C6 perfluoroalkyl;
• b) fluorovinylethers of general formula:
• CFX═CXOCF2OR (I)
• wherein
• R has the following meanings:
• C2-C6 linear or branched (per)fluoroalkyl,
• C5-C6 cyclic (per)fluoroalkyl,
• C2-C6 linear or branched (per)fluoro oxyalkyl, containing from one to three oxygen atoms,
• X═F, H;
• and
• c) bis-olefins having general formula:
• RI1RI2C═CRI3-Z-CRI4—CRI5RI6 (IA)
• wherein
• RI1, RI.3, RI.4, RI5, RI6 equal to or different from each other, are H or C1-C5 alkyl;
• Z is a C1-C18 linear or branched alkylene or C4-C18 cycloalkylene radical, optionally containing oxygen atoms, or a (per)fluoropolyoxyalkylene radical;
• d) optionally, one or more fluorinated olefinic comonomers selected from the following:
• (per)fluoroalkylvinylethers (PAVE) CF2═CFOR2f, wherein R2is a C1-C6 perfluoroalkyl;
• (per)fluoro-oxyalkylvinylethers CF2═CFOXa, wherein Xa is a C1-C12 alkyl, or a C1-C12 oxyalkyl, or a C1-C12 (per)fluoro-oxyalkyl having one or more ether groups;
• e) optionally, C2-C8 perfluoroolefins;
• and
• f) optionally, one or more C2-C8 non fluorinated olefinic comonomers;
• said fluoroelastomers comprising iodine and/or bromine atoms in the chain and/or in end position, said halogen atoms deriving from “cure site” comonomers and/or from chain transfer agents used in polymerization.