In this article, the spherulitic morphology and growth rate of the neat and plasticized poly(lactic acid) (PLA) with triphenyl phosphate (TPP) were compared and analyzed by polarizing optical microscopy with hot Stage at a temperature range of 100-142 degrees C. The spherulitic morphology of the neat PLA underwent a series of changes Such as the typical Maltese Cross at less than 132 degrees C, the disappearance of the Maltese Cross at 133 degrees C, the irregular and distorted spherulites at higher than 134 and 142 degrees C, respectively. For plasticized PLA, the spherulitic morphology exhibited the same changes as neat PLA, but these changes were shifted to lower temperature when compared with neat PLA. In the case of the spherulitic growth, neat PLA had the maximum value of 0.28 mu m/s at 132 degrees C, and plasticized PLA had higher values than that of neat PLA. Further analysis based on the Lauritzen-Hoffman theory was presented and results showed that the values of nucleation parameter 1, increased with TPP content. The crystallization behavior of PLA was analyzed by differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that the degree of crystallinity of plasticized PLA markedly increased when compared with neat PLA sharply with the incorporation of plasticizer. The crystallization kinetics for the neat and plasticized PLA under isothermal crystallization at 114 degrees C was described by the Avrami equation and the Avrami exponent is close to 2, implying that the crystallization mechanism did not change. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 112-121,2009