TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The solvent-less liquid ethylene propylene diene rubber compound is moldable to form a hydrogen permeable layer, and the hydrogen permeable layer is impermeable to oxidants. The compound comprises 41 wt.% of the liquid ethylene propylene diene rubber and 20 wt.% of filler system. The compound further comprises: 0.1-20 wt.% of the crosslinking agent to provide strength in vulcanization, where the crosslinking agent comprises a phenolic resin or an organic peroxide and/or a silanol; 1-15 wt.% of an additional ethylene propylene diene rubber, where the additional ethylene propylene diene rubber is produced from a member comprising ethylene propylene ethylidene norbornene, ethylene propylene dicyclopentadiene, ethylene butene ethylidene norbornene, ethylene propylene vinylidene norbornene and/or ethylene butene dicyclopentadiene. Preferred Components: The plasticizing oil is paraffin oil, naphthenic oil or ester oil. The filler system is zinc oxide, calcium carbonate, calcium oxide, aluminum silicate, kaolin clay, titanium dioxide, magnesium silicate, talc, precipitated silica, hydrated amorphous silica, fumed silica, silica pretreated with a coupling agent and/or carbon black. The coupling agent is mercaptan silanes, silanol, silane and/or polysulfidic silane. The solvent-less liquid ethylene propylene diene rubber compound is flowable at 23-150 degrees C. In the compound, an ethylene monomer content of the ethylene propylene diene rubber is 39-75 wt.%, a propylene monomer content of the ethylene propylene diene rubber is 24-60 wt.%, and a diene monomer content of the ethylene propylene diene rubber is 0.01-12 wt.%. The liquid ethylene propylene diene rubber has a viscosity of 100-200000 centipoises. Preferred Method: The method comprises mixing the liquid ethylene propylene diene rubber, and 20 wt.% of the filling system. The method further comprises: mixing 0.1-20 wt.% of a first curative into the liquid ethylene propylene diene rubber, the filler system and the plasticizer, where the first curative is an organic peroxide; mixing 0.1-10 wt.% of a second curative into the liquid ethylene propylene diene rubber, the filler system, and the plasticizer, where the second curative is a trimethylolpropane trimethacrylate; mixing 0.1-10 wt.% of a coupling agent into the liquid ethylene propylene diene rubber, the filler system and the plasticizer, where the coupling agent is vinyl tris(2-methoxy ethoxy) silane, mercaptan silane, silanol, silane, polysulfidic silane and/or another silane; mixing 0.1-15 wt.% of a lubricant into the liquid ethylene propylene diene rubber, the filler system, and the plasticizer, where the lubricant is a polyethylene homopolymer; allowing the uniform mixture to cure in the liquid injection molding equipment for 20-60 seconds; and radiating the formed part for a time period long enough to induce crosslinking in the formed part using electron beams or gamma -radiation. EXAMPLE - Liquid ethylene propylene rubber (20-60 wt.%) was placed in a low shear mixer. A solid ethylene propylene (up to 15 wt.%) was dissolved in a plasticizing oil and placed in the low shear mixture. A lubricant (0-15 wt.%), such as a polyethylene homopolymer lubricant, was added to the low shear mixer. The liquid ethylene propylene rubber, solid ethylene propylene was dissolved in the plasticizing oil, and lubricant was mixed until uniform. Then, a filler system (5-30 wt.%) along with any pigments was added into the low shear mixture and mixed until uniform. During the addition and mixing of the liquid ethylene propylene rubber, solid ethylene propylene dissolved in the plasticizing oil, lubricant, filler system and any pigments, the temperature was maintained at 212 degrees F and reduced to 150 degrees F, and then 0.1-20 wt.% of a crosslinking agent was added to the low shear mixture, and mixed to form a uniform mixture. The uniform mixture was molded at 120-200 degrees C using the liquid injection molding equipment and the mixture was cured to obtain solvent-less liquid ethylene propylene diene rubber compound.