An uncrosslinked copolymer of comonomers (a), (b) and (c) and containing reactive double bonds, the comonomers based on the total mols of (a), (b) and (c) comprising(a) 45 to 99.9 mol-% of at least one ethylene containing 1 to 4 fluorine atoms,(b) 0 to 54.9 mol-% of at least one comonomer selected from the group consisting of(b1) a linear or branched C.sub.3-8 alkene containing at least one fluorine atom,(b2) an alkyl vinyl ether containing at least one fluorine atom,(b3) an open-chain or cyclic C.sub.3-6 ketone containing fluorinated .alpha.,.alpha.'-positions and(b4) non-fluorinated C.sub.2-4 alkene, C.sub.3-6 alkyl vinyl ether or C.sub.4-6 vinyl ester, and(c) 0.1 to 5 mol-% of at least one unconjugated diene. They are produced by radical polymerization. Because of the absence of bromine and/or iodine, during subsequent peroxidic cross-linking no toxic alkyl bromide and/or iodide is released.