Melting and recrystallization kinetics of poly(butylene terephthalate)

Melting of original crystals and their recrystallization during heating were successfully separated for isothermally crystallized poly(butylene terephthalate) (PBT). The corresponding kinetics was determined and quantitatively discussed for a wide range of heating rates (0.1–100,000 K s -1 ) using fast-scanning chip calorimetry (FSC) and differential scanning calorimetry (DSC). The double melting peaks observed on the FSC curves are assigned to the melting of original crystals (low-temperature peak) and recrystallized and/or reorganized crystals (high-temperature peak). Heating rate dependence of the degree of recrystallization has been evaluated and the kinetics was discussed on the basis of Ozawa's method. Compared with the melt-crystallization and cold-crystallization, recrystallization kinetics is the fastest process. This is because many crystal remnants, which do not transform into the isotropic melt, act as athermal nuclei, and accelerate recrystallization.