This study aimed to evaluate the thermal behavior of polyhydroxybutyrate (PHB)/polypropylene grafted with maleic anhydride (PP-g-MA) blends and PHB/PP-g-MA/vermiculite bionanocomposites submitted to the biodegradation test according to ASTM G 160-03. The blends and bionanocomposites were prepared by melt intercalation method using a single screw extruder, and then, compression molded. The thermal analyzes were performed by thermogravimetry (TG) and differential scanning calorimetry. It was verified the decrease of onset degradation temperature and the melting temperature mainly after 86 days of exposure to the simulated soil. This behavior was more pronounced in bionanocomposites because of interactions between the maleic anhydride groups and the clay favoring biodegradation, making the systems more amorphous and propitious to the attack of microorganisms.(C) 2016 Society of Plastics Engineers