Rubber sealant formulations made of ethylene propylene diene monomer (EPDM), thermally conductive, hydrogen barrier, and reinforcing fillers, as well as liquid rubber, antioxidant, and abrasion resistance additives have been explored. The formulations can be peroxide cured to produce thermosetting elastomers with excellent thermomechanical properties, very low equilibrium hydrogen concentrations, as low as 2.2 wt ppm/mm3, and a high thermal conductivity. No chemical or mechanical failures were observed under high hydrogen pressure up to 90 MPa and during the rapid decompression process. The densities and the chemical structures (FTIR) of all formulations are the same with no significant changes before and after the thermal desorption analysis (TDA). In addition, the in-situ swelling during rapid decompression rate of 15 MP/min from high hydrogen pressure of 90 MPa was approximately 39 ± 2% compared to 80 to 250% for other EPDM formulations reported previously. All the invented formulations have extremely low equilibrium hydrogen concentrations and low swealing% under high hydrogen pressure compared to the commercially available sealants currently used in hydrogen storage and transportation infrastructure (2.2-2.9 compared to 6 to 50 wt ppm/mm3). The invented formulations can be used as outstanding and cost-effective alternatives to the sealants currently used in the manufacture of hydrogen storage vessels, tanks, and fuel stations.