In this study, we investigated the nonisothermal crystallization kinetics, crystallization morphology, and melting behavior of polymerized cyclic butylene terephthalate (pCBT) copolymerized with polycaprolactone (PCL). The results of this experiment indicated that the Ozawa exponent varied between 2 and 3 for pCBT, but between 1 and 2 for blends of pCBT/PCL. At the same temperature (185 degrees C), the crystallization rate constant K-T for pCBT/PCL blend was much lower than for pCBT homopolymer. These results indicated a strong hindrance on the crystallization of pCBT/PCL blends. The pCBT and pCBT/PCL samples exhibited no visible difference in morphology or microstructure. However, the crystallization and melting peak temperature of pCBT/PCL blends was similar to 20 degrees C lower than that of pCBT homopolymer. Crystal morphology confirmed that the mechanism of simultaneous polymerization and crystallization found applicable to pCBT homopolymer did not apply for blends of pCBT/PCL. It therefore appears that crystallization should be delayed until after the completion of pCBT/PCL copolymerization. POLYM. ENG. SCI., 51:1004-1013, 2011. (C) 2011 Society of Plastics Engineers