To attain excellent resistances to carbon dioxide gas permeation and to volume swell by forming a molded material comprising a blend of a hydrogenated NBR and a vinyl chloride-based resin.

The subject molding material comprises 100 pts.wt. of a blend of a hydrogenated NBR and 5-50 wt.% of a vinyl chloride-based resin such as a polyvinyl chloride or the like, and having incorporated therewith, 5-150 pts.wt. of an inorganic filler comprising a reinforcing filler such as carbon black, silica or the like and non-reinforcing filler such as calcium carbonate or the like, 0.1-7 pts.wt. of an organic peroxide, as a crosslinking agent, such as dicumyl peroxide, benzoyl peroxide or the like, 0.1-10 pts.wt. of a co- crosslinking agent such as trially cyanurate or the like. This material has a carbon dioxide gas permeability at 60 atm of 10-10 cm3 (STP).cm/cm2.sec.cmHg or less and a rate of change in volume swell (ΔV) of 20% or less. The hydrogenated NBR is obtained by hydrogenating at least 50% of conjugated diene units in an NBR having a medium or medium-high nitrile content.