Poly(butylene terephthalate) (PBT) was blended with different content (1, 3, and 6 wt %) of nanoscale fully vulcanized acrylic rubber (FVAR) powders in a twin extruder to prepare PBT/FVAR composites (PBT/ FVARL PBT/FVAR3, and PBT/FVAR6).The influence of different content (1, 3, and 6 wt %) of nanoscale FVAR powder on the nonisothermal crystallization behavior of PBT was investigated by using differential scanning calorimeter. The nonisothermal crystallization data were analyzed using Avrami, Ozawa, and Liu-Mo methods. The validity of kinetic models on the nonisothermal crystallization process of PBT and PBT/FVAR blends was discussed. All kinetic parameters showed that the "crystallization rate" followed the order: PBT > PBT/FVAR1 > PBT/FVAR3 > PBT/FVAR6 at a given cooling rate during experimental crystallization. However, when undercooling was taken into consideration, crystallization ability followed the order: PBT > PBT/FVAR6 > PBT/FVAR3 > PBT/FVAR1. A modified the Lauritzen-Hoffman equation was used to derive nucleation parameter (K-g) derived from nonisothermal crystallization. The results revealed that FVAR particles hindered the crystallization; however higher content of FVAR powders acted as heterogeneous nuclei in the nucleation stage to facilitated the crystallization of PBT. The dependence of the effective activation energy on conversion was evaluated on the basis of Friedman equation. (C) 2007 Wiley Periodicals, Inc.