The present invention is a composition and a method of forming a composition, the composition comprising at least a halogenated elastomer and an amine or phosphine. An additional rubber component may be present in the composition of the invention. In one embodiment, the halogenated elastomer is a isoolefin copolymer comprising a halomethylstyrene derived unit. The amine or phosphine compound is represented by the formula (R¹R²R³)Q, wherein Q is a Group 15 element, and wherein R¹ is either hydrogen or a C₄ to C₃₀ hydrocarbyl group, R² is either hydrogen or a C₁ to C₃₀ hydrocarbyl group; and R³ is either hydrogen or a C₁ to C₃₀ hydrocarbyl group provided that at least one of R¹, R² and R³ is not hydrogen. The additional rubber is selected from butyl rubber, halogenated butyl rubber, star-branched butyl rubber, halogenated star-branched butyl rubber, isobutylene homopolymer, butadiene rubber, neoprene, nitrile rubbers, ethylene/propylene/diene terpolymers, ethylene/propylene copolymers, styrene butadiene rubbers, polybutadiene, polyisoprene, isoolefin/alkylstyrene copolymer, halogenated isoolefin/alkylstyrene copolymer, natural rubber, polypropylene, polyethylene, polyurethane, polyvinyl chloride, silicon rubber, propylene oxide polymer, and mixtures thereof.