Abstract: A copolymer comprising monomeric units of tetrafluoroethylene, ethylene and at least one monomeric compound selected from the group consisting of 2-trifluoromethylpropylene and 2-methyl-1,1,3,3,3-pentafluoropropylene, which has a improved crack resistance at a high temperature.

Abstract: A copolymer comprising monomeric units derived from ethylene, tetrafluoroethylene or chlorotrifluoroethylene and a fluorovinyl compound of the formula:CH.sub.2 .dbd.CFRf (I)wherein Rf is a C.sub.2 -C.sub.10 fluoroalkyl group, a molar ratio of ethylene and tetrafluoroethylene or chlorotrifluoroethylene being from 40:60 to 60:40 and the content of the fluorovinyl compound being from 0.1% to 10% by mole having improved thermal resistance and high temperature mechanical properties such as crack resistance.

Abstract: A process for preparing a tetrafluoroethylene/fluoro(alkyl vinyl ether) copolymer comprising polymerizing tetrafluoroethylene and fluoro(alkyl vinyl ether) in an aqueous suspension system which comprises a mixed medium of water and a fluorohydrocarbon or a chlorofluorohydrocarbon in a volume ratio of from 1:1 to 10:1 at a temperature of from 0.degree. to 25.degree. C. in the presence of a polymerization initiator of the formula:[Cl(CF.sub.2).sub.n --COO].sub.2 (I)wherein n is an integer of 1 to 10, the copolymer obtained by the process having a small number of unstable terminal groups and excellent flex life.

Abstract: A fluoroelastomer composition comprising (a) a fluoroelastomer having stabilized end group derived from an isoparaffin selected from the group consisting of isobutane, isopentane and isohexane, (b) at least one member selected from the group consisting of bivalent metal oxides, bivalent metal hydroxides and mixtures of bivalent metal oxide or metal hydroxide with metal salt of weak acid, (c) an aromatic polyhydroxy compound and (d) a quaternary ammonium compound of 8-alkyl- (or 8-aralkyl-)1,8-diazabicyclo[5.4.0]-7-undecenium, provides a fluoro-rubber having low compression set and excellent elastic properties and has excellent processing and storage properties. The fluoroelastomer can be cured with appropriate induction time and fast cure rate by the use of a specific curing agent system mentioned above.