Abstract: Substantially gel-free copolymers of cyclopentene with dicyclopentadiene are prepared by polymerizing these monomers in the presence of (1) a catalyst comprising (a) at least one compound selected from the group consisting of dialkylaluminum iodides, alkylaluminum diiodides and mixtures of trialkylaluminum compounds with elemental iodine and (b) at least one solvent- or monomer-soluble tungsten compound, and (2) at least one nonconjugated acyclic olefin having at least one hydrogen on each double-bonded carbon atom. Catalyst component (a) is charged before catalyst component (b).

Abstract: Smoke retardant vinyl chloride and vinylidene chloride polymer compositions are obtained by including therein a synergistic mixture of (A) at least one nickel compound selected from the group consisting of NiCO.sub.3, NiCrO.sub.4, NiI.sub.2, NiO, NiS, NiSO.sub.4, nickel acetylacetonate, nickel citrate and nickel formate and (B) at least one iron compound selected from the group consisting of Fe.sub.3 C, Fe.sub.2 (MoO.sub.4).sub.3, Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, FeS, cyclopentadienyl iron dicarbonyl, ferric acetylacetonate, ferric hydroxy distearate, and ferrocene. Substantial smoke retardation is also obtained by including the above nickel compounds or iron compounds individually in the vinyl chloride or vinylidene chloride polymer compositions.