AbstractThe isothermal crystallization process of polycaprolactone/clay nanocomposites was studied at several temperatures. The effects of the clay type (modified and unmodified) and clay content were analyzed. Bulk crystallization was studied with differential scanning calorimetry and modeled with Avrami's equation. The reinforcement phase lowered the time at which the first crystal nucleus appeared (i.e., the induction time) and fastened the global crystallization rate in comparison with that of neat polycaprolactone. The spherulitic growth was analyzed by optical microscopy with polarized light. The presence of the clay produced more and bigger spherulites in the same time and with the same undercooling degree. All these properties were strongly dependent on the polycaprolactone/clay compatibility and hence the dispersion degree achieved in the nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008