a nitrile rubber based sealant system including seals a made from a unique delayed curing nitrite rubber composition . the composition has excellent storage ability in dry form which can be cured as needed under and with the aid of varying field conditions . the seals provide superior leak seal suitable for sealing leaks in pipes , fittings , flanges and other structures and are made by heating delayed self curing nitrile rubber formulation comprised of a critically selected combination of components including specially preconditioned nitrile rubber , sulfur , accelerants , activators , fillers , plasticizers , flame retardant , antidegradant , metallic filaments and optionally , nanophase rare earth material . the invention is also a method of sealing leaking pipes , fittings and structures in which the composition is injected into heated molds , where it is vulcanized without further additives , to form a hard , strong , durable chemical resistant seal that can be used to seal leaking pipes and structures without interruptions of flow or shut down of operations . the formulation has the advantage of wide temperature adaptability , wide medium resistance , injection manufacturability with excellent filling quality and sealing ability .