Hydrogenated nitrile rubber (HNBR) and a ternary copolymer of vinylidene fluoride, tetrafluoropropylene, and perfluoromethyl vinyl ether (FKM) were blended and vulcanized rubbers that have the excellent low temperature characteristics and oil resistance were successfully obtained. The results of dynamic mechanical analysis demonstrated the great improvement of low temperature characteristics for one of the polymer blend materials (FKM/HNBR = 30/70). Subsequently, the structures of the polymer blends were analyzed by using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The results of AFM and TEM showed that the polymer blend materials have phase-separated structures with the sea-island morphology. The sea regions were HNBR and the island regions were FKM for the samples containing less than 50% of FKM. On the other hand, the sea region was FKM for the sample containing 70% of FKM. Even in the stretched polymer blend, no gap or crazing was observed at the interface of FKM and HNBR. Therefore, some kind of strong bonding was presumed to exist between the two types of phases. (C) 2004 Wiley Periodicals, Inc.