Octavinyl POSS (vPOSS) and epoxycyclohexyl POSS (ePOSS) were separately incorporated into the poly(lactic acid)/poly(butylene succinate-co-adipate) (PLA/PBSA) blend by melt mixing. Field emission scanning electron microscopy and X-ray diffraction analysis revealed that vPOSS existed as crystalline aggregates, whereas ePOSS was more uniformly dispersed in the composites. The storage modulus and complex viscosity slightly decreased after the addition of vPOSS but Significantly increased after the addition of ePOSS, indicating the higher melt elasicity and broader processing window of the PLA/PBSA after the addition of ePOSS. The chloroform solutions of PLA/PBSA/ePOSS composites were turbid in appearance, and the extracted POSS showed absorbant peaks assigned to the vibration of -OH and -C = O groups in the Fourier transform infrared spectroscopy analysis, indicating the reactions between ePOSS and the PLA/PBSA. Polarized optical microscopy analysis revealed that the two types Of POSS Could act as nucleating agents for PLA, and enhance its crystallization ability. Thermal gravimetric analysis showed that the addition of the two types of POSS increased the decomposition temperature and activation energy, consequently retarding the thermal degradation of PLA/PBSA. The retardation of degradation is more significant with the addition of ePOSS, for the reactions reduced the end groups of PLA/PBSA as well as the Molecular chain mobility. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 3095-3102, 2009