AbstractThe compatibility of natural rubber/ethylene‐propylene‐diene monomer (EPDM) blends with and without different compatibilizers was evaluated with viscosity measurements, differential scanning calorimetry, and scanning electron microscopy. The blends were modified with two methods. In the first method, high‐energy radiation, in the form of γ‐rays, was used to create crosslinks (chemical bonds) between the rubber chains at the domain boundaries. In the second method, various compatibilizers, such as ethylene‐propylene‐diene monomer‐g‐maleic anhydride (prepared by the radiation‐induced graft copolymerization of EPDM with maleic anhydride), polybutadiene rubber, chlorinated rubber, chlorosulfonated polyethylene, and poly(vinyl chloride), were used. The results revealed that the addition of a small percentage of a compatibilizer reduced the domain size of the dispersed phase. Furthermore, the compatibility and properties of the blends were greatly enhanced and improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1–11, 2003