Hydrophobic polymers such as polyethylene and polypropylene are very difficult to use for preparing nanocomposites without a compatibilizer. However, in this study, polybutadiene rubber (BR; a hydrophobic polymer) nanocomposites were produced successfully without a compatibilizer with a melt-compounding method. Transmission electron microscopy showed an intercalated and exfoliated clay morphology in the polymer matrix, which led to increased mechanical properties. The tensile and tear strengths of the BR/Cloisite 20A hybrids were 4.4 times and 2 times larger than that of BR, respectively. The rebound resilience, compression set, and abrasion resistance were also improved by the addition of organoclay. The abrasion resistance of BR/Cloisite 20A was approximately 2 times larger than that of BR. The cure time (t(90)), scorch time (t(2)), and their difference (t(90) - t(2)) of the BR/organoclay hybrids were much reduced than those of BR. Thus, organoclays behaved as good fillers and effective accelerant agents for BR vulcanization. (c) 2006 Wiley Periodicals, Inc.