Methods for making processable rubber compositions containing fluorocarbon elastomers cured by polyol or phenol curative agents include an optional heat treating step before thermoplastic processing. In one aspect, a dynamic vulcanizate of a fluorocarbon elastomer containing an excess of un-reacted polyol curative agent is subject to a pre-molding heat treatment at a temperature of 150.degree. C. or above, but preferably below the thermoplastic processing temperature, for a time sufficient to drive off or decompose at least part of the un-reacted or excess polyol curative agent. After part or all of the curative agent is driven off or decomposed by the heat treatment, the heat treated material may be thereafter processed by thermoplastic techniques to form shaped articles. Advantageously, articles produced by thermoplastic processing of the heat treated dynamic vulcanizates are characterized by a low permeability to gases and vapors.