Correlation between polymerization of cyclic butylene terephthalate (CBT) and crystallization of polymerized CBT

Abstract

The correlation between ring-opening polymerization (ROP) of cyclic butylene terephthalate (CBT) and crystallization of polymerized CBT (pCBT) strongly affected the final properties of pCBT and its composites. The major objective of this contribution is to pinpoint the threshold temperature between them and the interrelation is successfully disclosed. That is, crystallization during polymerization occurs below 204 °C and the crystallization properties of pCBT are determined by this isothermal ROP stage; polymerization and crystallization are gradually separated with the increase of temperature of ROP (T P) from 204 °C, and the crystallization properties of pCBT are dominated by cooling stage; only polymerization is performed above 212 °C. Moreover, quantitative analysis suggests that uniform crystal size distributions and thicker lamellar crystals derive from the stage of crystallization during polymerization. On the contrary, the crystal size distributions become wider above 204 °C of T P and lead to obvious double melting peaks during heating scan. These efforts provide a very useful guide for the related investigation and application of CBT.