Abstract: Fluoroelastomers comprising, by mole:(a) from 33 to 75% of tetrafluoroethylene (TFE);(b) from 15 to 45% of a perfluorovinylether (PVE);(c) from 10 to 22% of vinylidene fluoride (VDF).They are endowed with high resistance to polar solvents and to bases, excellent compression set also at high temperatures, low Tg and good processability.They result particularly suitable for the manufacture of sealing elements (O-rings) for plants intended to the production of methylterbutylether (MTBE).

Abstract: The emission of the highly toxic volatile products, such as methyl bromides or iodides, or ethyl bromides or iodides, during the cure with peroxides of fluoroelastomers containing bromine or iodine atoms is substantially reduced by adding to the cure mix small amounts of substances capable of combining with the radicals which give rise to the aforesaid toxic products, thereby preventing them from forming. This procedure does not sensibly affect the cure trend and results.

Abstract: Ionically curing of VDF-containing fluoroelastomers selected from the ones containing less than 60 moles % of VDF and from the ones containing hydrogenated olefins is improved by using, as accelerators, triazinic compounds of formula: ##STR1## (R=H, C.sub.1 -C.sub.4 alkyl; R'=R or benzyl, arylalkyl; X=Cl, Br, I, a bisphenoxy radical or O--CH.sub.2 RF--CH.sub.2 R.sub.2 ; Rf=a perfluorooxyalkylene chain; R.sub.2 =--OH, --O.sup.-). What is claimed are the fluoroelastomeric compositions containing said accelerators.

Abstract: The emission of the highly toxic volatile products, such as methyl bromides or iodides, or ethyl bromides or iodides, during the cure with peroxides of fluoroelastomers containing bromine or iodine atoms is substantially reduced by adding to the cure mix small amounts of substances capable of combining with the radicals which give rise to the aforesaid toxic products, thereby preventing them from forming. This procedure does not sensibly affect the cure trend and results.

Abstract: The invention relates to new fluoroelastomeric copolymers endowed with resistance to bases and suitable in particular for preparing O-rings, comprising:______________________________________ (I) VDF 47-80 mols % HFP and/or PAVE 16-30 mols % hydrogenated olefin containing 2-25 mols % 2-4 C or (II) VDF 42-80 mols % PAVE 16-30 mols % hydrogenated olefin containing 2-30 mols % 2-4 C ______________________________________The invention relates to new fluoroplastomeric copolymers endowed with resistance to bases, comprising: ______________________________________ (III) VDF 70-99 mols % HFP and/or PAVE 0-16 mols % hydrogenated olefin containing 1-30 mols % 2-4 C ______________________________________A further object of the invention is a process for preparing the abovesaid fluoroelastomeric and fluoroplastomeric copolymers.

Abstract: Fluoroelastomeric copolymers exhibiting high resistance to bases and alcohols, as well as high mechanical properties and low-temperature resistance, comprising, in moles:4-75% of units of vinylidene fluoride;12-40% of units of hexafluoropropene and/or perfluorovinylether and/or hydropentafluoropropene and/or chlorotrifluoroethylene;2-35% of units of an olefin containing up to 4 carbon atoms;2-60% of units of tetrafluoroethylene, provided that, when the sum of the olefin units and the perfluorovinylether units is equal to or greater than 70%, such copolymers possess a molecular weight sufficiently high to exhibit good mechanical characteristics.

Abstract: Fluoroelastomeric copolymers, vulcanizable by ionic methods, suitable for the manufacture of "shaft seals" and "fuel hoses", comprising by weight:______________________________________ VDF 30-47% HFP 20-40% PAVE 3-20% TFE 10-30% ______________________________________

Abstract: Fluoroelastic copolymers, suitable for the manufacture of O-rings, comprising by weight:48-65% of VDF units21-36% of HFP units3-9% of PAVE units0-17% of TFE units

Abstract: There are described mixes, which are curable by using radical intermediates, are based on fluoroelastomers containing bromine or iodine, exhibit, during curing, a low emission of toxic vapors of methyl bromide or iodide and are characterized in that they contain, as cross-linking agents, peroxides having the following formulas: ##STR1## wherein the substitutents from R.sub.1 to R.sub.17 have the significances defined in the specification.