Polylactic acid (PLA)-based composite films with four different loadings of nanoclay (2, 5, 10, and 15 wt %) were prepared using a solvent casting method and their crystalline morphology was investigated. The crystalline morphology was significantly different in the films depending on the clay content and its dispersion in the matrix. The clay platelets played the role of nucleating sites facilitating crystallization during solvent evaporation and this effect was most predominant in PLA 10. The To crystallinity and the crystallite size were determined by XRD analysis. The morphology was investigated with scanning electron microscopy (SEM) and by atomic force microscopy (AFM). A fibrillar pattern was evident in SEM micrographs, which were confirmed by AFM. The thermal properties were investigated with DSC and TGA. The glass transition temperature (T-g) increased from 51.9 to 55-57 degrees C in all the nanocomposite samples. The melting peak temperature (168 degrees C) remained unaltered in the nano-composites, but the melting enthalpy varied depending on the PLA/clay interaction. The rate of degradation was controlled by the dispersion of clay platelets in the matrix and was very low in low clay-filled films. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 143-151, 2010