Abstract: Cyclopentanes alkyl-substituted with one or more C.sub.1 -C.sub.6 alkyls are used as chain transfer agents in (co)polymerization reactions carried out, either in suspension or in aqueous emulsion, at low temperatures, comprised between -30.degree. and +30.degree. C., for preparing thermoplastic hydrogen-containing fluoropolymers , such as for instance ethylene/chlorotrifluoroethylene and ethylene/tetrafluoroethylene copolymers, or homopolymers and copolymers of vinylidenefluoride. They are transfer agents having high efficiency, which are liquid and thus can be easily handled and dosed, non-toxic, yielding alkyl end groups of high thermal stability.

Abstract: A stabilized melt processable composition containing a halopolymer (e.g., an ethylene chlorotrifluoroethylene copolymer) and an effective stabilizing amount of an ester of a (4-hydroxy-5-alkylphenyl) alkanoic acid and at least one phosphite. Such compositions may be melt processed and extruded at high temperatures (e.g., up to 305.degree. C.) and retain their stability. These compositions are especially desirable in wire and cable coating applications.