Crystallisation kinetics of cyclic and linear poly(butylene terephthalate)

The isothermal crystallisation kinetics of cyclic poly (butylene terephthalate) (cPBT) were analysed using a primary-limited differential Avrami analysis, and the equilibrium melting point ( TomTmo ) was determined using the Hoffman–Weeks approach. Further analysis of the kinetic data using the Hoffman–Lauritzen analysis yielded the nucleation constant (Kg) and the end surface free energies (σσe). The kinetic parameters obtained for cPBT were compared with a commercial sample of linear PBT. The Kg values of cPBT and linear PBT were observed to be 5.13 ± 0.02 × 105 K2 and 4.50 ± 0.02 × 105 K2, respectively. Meanwhile, the σσe of cPBT was calculated as 6.44 ± 0.05 × 10−4 J2 m−4 and linear PBT was 5.54 ± 0.05 × 10−4 J2 m−4.