one preferred embodiment the base rubber comprises a transition metal polybutadiene a rare earth catalyzed polybutadiene rubber or blends thereof if desired the polybutadiene can also be mixed with other elastomers known in the art such as natural rubber polyisoprene rubber and or styrene butadiene rubber in order to modify the properties of the core other suitable base rubbers include thermosetting materials such as ethylene propylene diene monomer rubber ethylene propylene rubber butyl rubber halobutyl rubber hydrogenated nitrile butadiene rubber nitrile rubber and silicone rubber thermoplastic elastomers tpe many also be used to modify the properties of the core layers or the uncured core layer stock by blending with the base thermoset rubber these tpes include natural or synthetic balata or high trans polyisoprene high trans polybutadiene or any styrenic block copolymer such as styrene ethylene butadiene styrene styrene isoprene styrene etc a metallocene or other single site catalyzed polyolefin such as ethylene octene or ethylene butene or thermoplastic polyurethanes tpu including copolymers e g with silicone other suitable tpes for blending with the thermoset rubbers of the present invention include pebax u00ae which is believed to comprise polyether amide copolymers hytrel u00ae which is believed to comprise polyether ester copolymers thermoplastic urethane and kraton u00ae which is believed to comprise styrenic block copolymers elastomers any of the tpes or tpus above may also contain functionality suitable for grafting including maleic acid or maleic anhydride additional polymers may also optionally be incorporated into.