A method is disclosed for preparing an elastomeric base composition
comprising: (I) mixing by an extrusion process (A) a fluorocarbon
elastomer with (B) an optional compatibilizer, (C) an optional catalyst
(D) a silicone base comprising a curable organopolysiloxane, (E), an
optional crosslinking agent (F) a cure agent in an amount sufficient to
cure said organopolysiloxane; and (II) dynamically vulcanizing the
organopolysiloxane, wherein the weight ratio of fluorocarbon elastomer
(A) to silicone base (B) in the elastomeric base composition ranges from
95:5 to 30:70. The cured rubber compositions obtained from the
elastomeric base compositions herein have good fuel resistance
properties.